WO2011148975A1 - 画像処理装置、荷電粒子線装置、荷電粒子線装置調整用試料、およびその製造方法 - Google Patents
画像処理装置、荷電粒子線装置、荷電粒子線装置調整用試料、およびその製造方法 Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B15/00—Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F18/00—Pattern recognition
- G06F18/20—Analysing
- G06F18/22—Matching criteria, e.g. proximity measures
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/02—Details
- H01J37/22—Optical or photographic arrangements associated with the tube
- H01J37/222—Image processing arrangements associated with the tube
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/26—Electron or ion microscopes; Electron or ion diffraction tubes
- H01J37/28—Electron or ion microscopes; Electron or ion diffraction tubes with scanning beams
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/245—Detection characterised by the variable being measured
- H01J2237/24571—Measurements of non-electric or non-magnetic variables
- H01J2237/24578—Spatial variables, e.g. position, distance
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/26—Electron or ion microscopes
- H01J2237/28—Scanning microscopes
- H01J2237/2813—Scanning microscopes characterised by the application
- H01J2237/2817—Pattern inspection
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/26—Electron or ion microscopes
- H01J2237/282—Determination of microscope properties
- H01J2237/2826—Calibration
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
- Y10T428/24355—Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
Definitions
- the present invention relates to a method, an apparatus, and a computer program for measuring and evaluating a displacement and the like in an image obtained by a scanning electron microscope and the like, and more particularly, a method capable of measuring and evaluating a distribution of deformation and displacement in an image. , Apparatus and computer program, or charged particle beam apparatus adjustment sample, and its manufacturing method.
- scanning pattern width measurement (hereinafter referred to as “measurement”) and visual inspection are used.
- An electron microscope (Scanning / Electron / Microscope: SEM) is widely used.
- a scanning electron microscope emits an electron beam emitted from an electron source and narrowed down by a converging lens and an objective lens using an interaction between a magnetic field or an electric field and an electron beam on a sample using a deflector.
- Secondary signals (secondary electrons, reflected electrons, electromagnetic waves) generated from the sample by electron beam irradiation are detected by a detector that uses the photoelectric effect, etc., and the detected signal is scanned with the electron beam. It is an apparatus that forms a sample image by converting and processing a signal such as a synchronized luminance signal that can be visualized.
- Patent Document 1 an absolute strain at a first magnification is measured using a measurement standard sample having a periodic structure, and a measurement sample having an arbitrary structure is photographed at a first magnification and a second magnification (second).
- the image captured at the first magnification is used as a comparison image), and the image captured at the first magnification is expanded / contracted to the second magnification to form an expanded / contracted image. It is described that the relative strain is measured and the absolute strain of the second magnification is obtained based on the relative strain and the absolute strain.
- a measuring apparatus using an SEM is required to perform highly accurate measurement stably for a long period of time. Furthermore, it is necessary to reduce the difference in measurement dimensions of a plurality of length measuring devices on the production line so that the same measurement result can be obtained regardless of which device is used for measurement. For this purpose, it is necessary to simply monitor the measurement accuracy of the length measuring electron microscope and adjust and calibrate the device so that the measurement results with the same accuracy are always obtained in all devices used in the semiconductor production line.
- Patent Document 3 Patent Document 4, and Patent Document 5 are known as methods for measuring edge sharpness from an electron microscope image.
- a sample for measuring edge sharpness a sample in which heavy metal fine particles such as gold particles are attached to a conductive organic film described in Patent Document 2 is known.
- a sample is known in which fine needle-like protrusions of Si are formed on a Si substrate.
- Non-Patent Document 2 a sample in which a Si oxide film and a resist are stacked on a Si substrate is subjected to dry etching, thereby forming an irregular pattern of the Si oxide film on the Si substrate.
- a method is known in which edge sharpness is calculated by acquiring electron microscope images of these samples and performing image processing.
- magnification calibration accuracy of the electron microscope image is another factor that determines the measurement accuracy of the electron microscope.
- a superlattice sample having a periodic structure as described in Patent Document 6 has been proposed as a calibration sample having a fineness with a pitch dimension of 100 nm or less.
- a technique for calibrating a local magnification in an image using such a magnification calibration sample having a periodic structure a technique described in Patent Document 1 is known.
- JP 2008-14850 (corresponding US Patent Publication USP 7,633,064) Japanese Patent Laid-Open No. 11-224640 Japanese Patent Laying-Open No. 2005-268231 (corresponding US Patent Publication USP 7,236,651) US Pat. No. 5,969,273 US Pat. No. 6,545,275 JP 2007-303892 A (corresponding US Patent Publication USP 7,834,997)
- the standard sample is generally a regular pattern in which regular patterns are arranged uniformly, but when a high-magnification image is acquired, the pitch interval varies locally. Since such roughness causes variations in the measured pitch interval, it is necessary to suppress the variation by measuring multiple pitch intervals at different positions and averaging them. Cost.
- semiconductor devices are in the direction of further miniaturization and higher integration.
- the resolution evaluation value of the scanning electron microscope will be measured using the above-mentioned conventional samples, the electron microscope will be adjusted, and the magnification of the image will be increased. We examined whether it was possible to calibrate.
- FIG. 68A shows a top view
- FIG. 68B shows a cross-sectional view along a straight line 6817.
- the needle-like fine protrusions 6813, 6814, and 6815 formed on this sample have different height differences 6816 at the tips of the protrusions 6813, 6814, and 6815 in the electron microscope image acquisition region as shown in the cross-sectional view. It was.
- the cross-sectional shape of the protrusion was needle-like, and the cross-sectional shape was also varied by the protrusion. Since this sample 6812 has a very fine pattern, the edge sharpness of an electron microscope image at a high magnification can be measured. However, as described above, due to variations in height and shape of individual protrusions, this sample 6812 can be measured. Using 6812, it is difficult to stably measure the edge sharpness or magnification of an electron microscope with high accuracy and good reproducibility.
- FIG. 69 shows a diagram for explaining the influence of the variation in pattern height on the measurement accuracy of edge sharpness.
- FIG. 69A shows a schematic diagram of a cross section of a high pattern 6941 and a low pattern 6942 as a schematic diagram of a cross section of patterns having different heights.
- FIG. 69B shows the secondary electron profile 6944 of the electron microscope image of the high pattern 6941 and the secondary electron profile 6944 of the electron microscope image of the low pattern 6942 shown in FIG.
- Edge sharpness is obtained by measuring the distance at which the electron beam profile changes at the pattern edge.
- the edge sharpness is the distance from the portion where the signal from the pattern top is flat to the portion where the signal from the pattern bottom 8 is flat.
- edge sharpness 6945 obtained by the high pattern 6941 and the edge sharpness 6946 obtained by the low pattern 6942
- a variation 6947 in edge sharpness due to the pattern height occurs. Therefore, if the pattern height of the sample to be measured varies, there arises a problem that the measured value of edge sharpness varies. If the pattern height varies in the region where the electron microscope image is acquired, the measurement accuracy and measurement reproducibility of the edge sharpness deteriorate, and there is a problem that the electron microscope cannot be adjusted with high accuracy.
- FIG. 70 shows an example of a black-and-white gradation histogram of an electron microscope image of a sample on which needle-like protrusions as described in Non-Patent Document 1 are formed. The higher the gradation of the histogram, the brighter the image, and the lower the gradation, the darker the image.
- the histogram in FIG. 70 shows an example of a black-and-white gradation histogram of an electron microscope image of a sample on which needle-like protrusions as described in Non-Patent Document 1 are formed. The higher the gradation of the histogram, the brighter the image, and the lower the gradation, the darker the image.
- a gradation difference 7033 between the bright peak 7031 and the dark peak 7032 is a brightness component that changes depending on the height of the needle-like protrusion.
- the gradation variation ⁇ B2 of the dark peak 7032 is a signal variation from the bottom of the pattern, and is caused by an image noise component and a variation in the height of the pattern bottom.
- the variation ⁇ B2 is mainly the image noise component ⁇ N.
- the variation ⁇ T2 of the bright peak 7031 is a variation in the signal from the pattern top portion of the needle-like protrusions 6813 to 6815, and is a variation obtained by combining the image noise ⁇ N and the brightness variation ⁇ TH2 caused by the variation in the height of the pattern top portion. is there.
- the variation ⁇ T2 of the bright peak 7031 is 50 gradations, and the variation ⁇ B2 of the dark peak 7032 is about 25 gradations. Therefore, the variation ⁇ N image noise component is 25 gradations, the component sigma TH2 due to height variation of the pattern top portion is about 25 gradations.
- the difference between the bright peak 7031 and the dark peak 7032 is 100 gradations, and the brightness changes depending on the height of the pattern top from the pattern bottom. It is a component. Therefore, for example, assuming that the average height from the pattern bottom to the pattern top is 100 nm, the height variation of the needle-like pattern can be estimated to be about 25 nm. Therefore, it has been found that it is difficult to measure with a measurement variation of edge sharpness due to the sample height being reduced to 1/10 or less.
- the gradation variation component ⁇ TH due to the height variation of the pattern top portion of the histogram of the electron microscope image corresponds to 10 gradations.
- the measurement accuracy of edge sharpness may change depending on the in-focus height of the electron optical system.
- the electron beam profile when the electron microscope is focused on the high protrusion 6813 shown in FIG. 68B is shown in FIG. 71A
- the electron beam profile when the low protrusion 6814 is in focus Is shown in FIG.
- the edge 7125 of the protrusion 6813 can be measured accurately from the electron beam profile, but the edge 7126 near the groove bottom (pattern bottom) cannot be measured accurately.
- FIG. 72 shows a schematic diagram of a chip-like sample (sample) placed on the sample holder.
- the sample 7264 is placed on the sample holder 7261 and an image is acquired, the uppermost surface 7262 of the sample holder 7261 and the surface 7263 of the sample 7264 need to coincide with each other.
- This is an electric field intensity distribution on the sample surface 7263 when the sample is a chip smaller than 5 mm square and the height of the uppermost surface 7262 of the sample holder 7261 and the surface 7263 of the sample 7264 are shifted.
- the measurement accuracy decreases when an electron microscope image of the wafer to be inspected is acquired after adjusting the electron microscope using the electron microscope image of the sample 7264 on the sample holder 7261. It is a fact that the specimen 7264 is placed with the height of the uppermost surface 7262 of the specimen holder 7261 and the surface 7263 of the sample completely matched to realize a field strength distribution 7265 that is completely the same as the field strength distribution on the surface of the wafer to be inspected. It is difficult.
- Non-Patent Document 2 In a sample in which an irregular pattern is formed on a Si oxide film formed on a Si substrate as described in Non-Patent Document 2, the surface of the sample is charged when irradiated with an electron beam, and this charging causes electrons to be charged. There is a problem that the microscope image is blurred or distorted. In an electron microscope image in which the image is blurred or distorted due to charging of the sample surface, there is a concern that the optical system of the scanning electron microscope cannot be precisely adjusted.
- magnification calibration is performed using a sample having a periodic structure as described in Patent Document 6, the following problems arise.
- sample dimensional variations cause measurement errors in magnification, it is necessary to acquire a large number of images, measure the pitch interval, and use the average value as the length measurement value. Takes time.
- this measurement In order to measure the magnification and shape distortion in the image, this measurement must be performed in each local region in the image. Therefore, it takes several hours or more to complete the measurement. And this measurement must be repeated periodically in order to confirm the stability of the device.
- a standard sample whose dimensions are calibrated is generally expensive, resulting in an increase in the maintenance cost of the apparatus.
- a charged particle beam device adjustment sample for solving the above-described problem and adjusting a charged particle beam device that can be used at a manufacturing site of a semiconductor device with high accuracy and stability, The manufacturing method and a charged particle beam apparatus adjusted with high accuracy using the adjustment sample are proposed.
- the first image of the first area having the specific area on the sample as the first part, and the first area is different in position and the first area.
- An image processing apparatus or the like is proposed in which the distance between the first image and the second image is obtained for a plurality of parts of the overlapping region of the first image and the second image.
- an image processing apparatus or the like is proposed that uses a local distortion in the detected image to obtain a positional shift distribution of each area due to the distortion in the image.
- the substrate has a concavo-convex pattern formed on a surface of the substrate and made of a semiconductor material, and the concavo-convex pattern is an irregular pattern in a two-dimensional direction.
- the upper surface of the convex portion of the concavo-convex pattern is a flat surface having a uniform height.
- the process of forming a uniform Si oxide film on the Si substrate with a thickness in the range of 10 nm to 0.1 nm that is not patterned, and a plasma dry etching apparatus the selectivity to the Si oxide film is high.
- a step of forming a fine pattern on the Si substrate under conditions, and an outermost surface of the Si substrate before the dry etching constitutes a flat surface of the upper surface of the fine pattern. It is set as the manufacturing method of a sample.
- the charged particle beam device adjustment sample at least one of focus, astigmatism, image resolution, edge sharpness, image magnification, and image distortion is measured, and the measured value falls within a preset value range.
- the charged particle beam apparatus is characterized by being adjusted to enter.
- the distance information between the same specific regions between the first image and the second image includes partial distortion of the image.
- the distance between the specific regions should be 100 nm.
- this distance is a value other than 100 nm, the position of the specific area is displaced on the image. That is, it can be seen that the specific region is located at a distorted position in the image. Therefore, it is possible to measure the distribution of distortion in the field of view by obtaining the distance for a plurality of parts.
- the first image and the second image are acquired at the same magnification (the same field size), the image of the specific area is reproduced under the same conditions. And the second image can be measured with high accuracy, and as a result, highly accurate distortion measurement can be realized.
- This result is local image distortion information such as magnification distribution. Furthermore, the distribution of local distortion in the field of view is corrected to correct the position in the image such as edge points detected for length measurement and shape evaluation of arbitrary patterns in images with image distortion. It is possible to extract each image, calculate a relative displacement distribution due to distortion of the entire image, and correct the position in the image such as the detected edge point.
- a charged particle beam apparatus that can be used at the manufacturing site of a semiconductor device can be adjusted with high accuracy and stability.
- a charged particle beam apparatus adjustment sample and a method for manufacturing the same can be provided.
- the charged particle beam apparatus adjusted with high precision can be provided by using the said sample for adjustment.
- FIG. 3 is a diagram illustrating the principle of image distortion measurement.
- the figure which shows the example of calculation of the movement amount of points other than a measurement point. 7 is a measurement flowchart of a positional deviation amount distribution.
- FIG. 69 is an example of an edge sharpness measurement flowchart using the adjustment sample shown in FIG. 66.
- FIG. It is a flowchart explaining the image acquisition process for an image distortion measurement. It is explanatory drawing of the method of measuring the movement amount of a pattern by image matching.
- FIG. 67 is an example of a power spectrum of an image of an adjustment sample shown in FIG. 66.
- the present embodiment relates to a technique for observing a sample in a device such as a microscope for measuring an image and measuring a dimension of a shape reflected in the sample, and mainly a method for measuring and evaluating magnification distortion and shape distortion in the image. explain.
- the present invention relates to a scanning electron microscope that observes a fine pattern using a scanning electron microscope and measures its dimensions, and in particular, a method for measuring or calibrating magnification distortion and shape distortion in an observation image by a microscope.
- the present invention relates to a scanning electron microscope.
- magnification uniformity or magnification distortion in the image Since the dimension of microfabrication has already become so fine that the unit of nm is used, a very high accuracy is required for the length measurement value which is a dimension value obtained by length measurement. For this, the magnification of the sample image must be accurate and it must be uniform everywhere in the image. This is called magnification uniformity or magnification distortion in the image.
- magnification not only the magnification but also the shape must be uniform. This means that if the sample is a straight line, it must also be a straight line in the image. When local magnification distortion occurs in the image, what should be a straight line appears to be bent in the peripheral portion. Even if bent, the magnification may be accurate. This is called shape uniformity or shape distortion in the image.
- magnification distortion and shape distortion In order to quantitatively measure such magnification distortion and shape distortion, by measuring the magnification standard sample in which the dimension of the shape on the sample is calibrated in advance, and comparing it with the calibration dimension of the standard sample, Work to calibrate the magnification is regularly performed.
- the required accuracy for the magnification uniformity in the image is about 0.1%.
- the required accuracy with respect to the contour shape of the outer periphery of the pattern is about 1 nm or less in terms of the contour position.
- the uncertainty of the pattern size of the standard sample is about 1/10 of the required accuracy.
- the uncertainty needs to be traceable by a calibration certificate issued by a public certification body in accordance with the certification standard. Otherwise, accuracy and uncertainty cannot be trusted.
- the pitch dimension of regularly arranged linear patterns is set as a standard dimension, and the length thereof is about 100 nm.
- the magnification is about 150,000 times, and the length is measured. When observed at this magnification, the pitch interval varies locally.
- the contour of the linear pattern on the sample is not a perfect straight line but has local irregularities. This is called edge roughness.
- the pitch intervals at various locations on the sample are measured, and the average value thereof is regarded as the measured value. When measuring at about 20 points, the variation of the average value is within about ⁇ 0.3 nm.
- distortion in the field of view can be measured with a small number of SEM image acquisitions by applying an image processing technique, so that distortion can be measured at high speed.
- various samples can be applied.
- a method, an apparatus, and a computer program for measuring and evaluating the amount of movement, deformation, displacement, etc.
- a transmission medium for transmitting a program an image processor designed exclusively for image processing, and a dedicated hardware accelerator
- CD-SEM critical dimension scanning electron microscope
- DR-SEM defect review inspection apparatus
- a charged particle beam apparatus is illustrated as an apparatus for forming an image, and an example using an SEM is described as one aspect thereof.
- a focused ion beam (FIB) apparatus that scans a beam to form an image may be employed as the charged particle beam apparatus.
- FIB focused ion beam
- FIG. 7 is a schematic explanatory diagram of a measurement / inspection system in which a plurality of measurement or inspection devices are connected to a network.
- the system has a configuration in which SEMs 701, 702, and 703 that mainly measure or inspect pattern dimensions of semiconductor wafers, photomasks, and the like are connected to a network.
- a condition setting device 704 that functions as an image processing device that sets a measurement position, a measurement condition, and the like on the design data of the semiconductor device and performs measurement and inspection based on the obtained SEM image in the network.
- the design data is expressed in, for example, the GDS format or the OASIS format, and is stored in a predetermined format.
- the design data can be of any type as long as the software that displays the design data can display the format and can handle the data as graphic data.
- the storage medium 706 may be incorporated in the measurement device, the control device of the inspection device, the condition setting device 704, or the simulator 705.
- the simulator 705 has a function of simulating a defect occurrence position based on design data.
- the SEMs 701, 702, and 703 are provided with respective control devices, and control necessary for each device is performed. It is assumed that the functions of the simulator and setting functions such as measurement conditions are mounted on these control devices. Therefore.
- an electron beam emitted from an electron source is focused by a plurality of lenses, and the focused electron beam is scanned one-dimensionally or two-dimensionally on a sample by a scanning deflector.
- Secondary electrons Secondary Electron: SE
- Backscattered Electron: BSE Backscattered Electron emitted from the sample by scanning the electron beam are detected by a detector, and in synchronization with the scanning of the scanning deflector, the frame memory Or the like.
- the image signals stored in the frame memory are integrated by an arithmetic device mounted in the control device. Further, scanning by the scanning deflector can be performed in any size, position, and direction.
- control and the like are performed by the control device of each SEM, and images and signals obtained as a result of electron beam scanning are sent to the condition setting device 704 via a communication line network.
- the control device that controls the SEM and the condition setting device 704 are described as separate units.
- the present invention is not limited to this, and the condition setting device 704 controls and measures the device. Processing may be performed in a lump, or SEM control and measurement processing may be performed together in each control device.
- condition setting device 704 or the control device stores a program for executing a measurement process, and measurement or calculation is performed according to the program.
- the condition setting device 704 has a function of creating a program (recipe) for controlling the operation of the SEM based on semiconductor design data, and functions as a recipe setting unit. Specifically, a position for performing processing necessary for the SEM such as a desired measurement point, auto focus, auto stigma, addressing point, etc. on design data, pattern outline data, or simulated design data And a program for automatically controlling the sample stage, deflector, etc. of the SEM is created based on the setting.
- FIG. 8 is a schematic configuration diagram of a scanning electron microscope.
- An electron beam 803 extracted from an electron source 801 by an extraction electrode 802 and accelerated by an accelerating electrode (not shown) is focused by a condenser lens 804 which is a form of a focusing lens, and then is scanned on a sample 809 by a scanning deflector 805.
- the electron beam 803 is decelerated by a negative voltage applied to an electrode built in the sample stage 808 and is focused by the lens action of the objective lens 806 and irradiated onto the sample 809.
- electrons 810 such as secondary electrons and backscattered electrons are emitted from the irradiated portion.
- the emitted electrons 810 are accelerated in the direction of the electron source by an acceleration action based on a negative voltage applied to the sample, collide with the conversion electrode 812, and generate secondary electrons 811.
- the secondary electrons 811 emitted from the conversion electrode 812 are captured by the detector 813, and the output of the detector 813 changes depending on the amount of captured secondary electrons. In accordance with this output, the brightness of a display device (not shown) changes.
- an image of the scanning region is formed by synchronizing the deflection signal to the scanning deflector 805 and the output of the detector 813.
- the scanning electron microscope illustrated in FIG. 8 includes a deflector (not shown) that moves the scanning region of the electron beam. This deflector is used to form an image of a pattern having the same shape existing at different positions. This deflector is also called an image shift deflector, and enables movement of the field of view (Field ⁇ Of View: FOV) position of the electron microscope without moving the sample by the sample stage.
- the image shift deflector and the scan deflector may be a common deflector, and the image shift signal and the scan signal may be superimposed and supplied to the deflector.
- FIG. 8 demonstrates the example which detects the electron emitted from the sample by converting once with a conversion electrode, of course, it is not limited to such a configuration, for example, the accelerated electron It is possible to adopt a configuration in which the detection surface of the electron multiplier tube or the detector is arranged on the orbit.
- the control device 710 controls each component of the scanning electron microscope and is formed on the sample based on a function of forming an image based on detected electrons and an intensity distribution of detected electrons called a line profile. It has a function to measure the pattern width.
- FIG. 9 is a diagram illustrating an overview of a processor that evaluates image distortion.
- a processor that evaluates image distortion.
- FIG. 9 an example in which processing described later is performed using an image processor designed exclusively for image processing or a dedicated hardware accelerator will be described.
- the present invention is not limited to this.
- a general-purpose processor may be used. You may make it implement the process which is mentioned later by running a predetermined program.
- An image processor 901 illustrated in FIG. 9 includes a movement amount calculation area setting unit 902, a visual field shift condition setting unit 903, a template setting unit 904, a pattern matching execution unit 905, a positional deviation amount / direction calculation unit 906, and an image distortion amount calculation.
- the movement amount calculation area setting unit 902 sets a plurality of areas in which the movement amount on the image is to be calculated based on an input or a preset condition.
- the visual field shift condition setting unit 903 sets the visual field shift amount of a scanning electron microscope or the like based on the input or preset shift amount and direction.
- the shift amount set here is stored in the recipe storage unit as a deflection signal of the image shift deflector.
- the recipe storage unit may be built in the control device 710 of the scanning electron microscope, or may be stored in an external storage medium.
- the template setting unit 904 creates a template by cutting out part of an image obtained by a scanning electron microscope, design data of a semiconductor device, or part of an image obtained by performing exposure simulation or the like on the design data. .
- the template created by the template setting unit 904 is stored in the template storage unit 908 or the recipe storage unit.
- the pattern matching execution unit 905 executes pattern matching based on the template created by the template setting unit 904.
- Template matching is to specify a pattern using a template that displays a pattern with the same shape as the desired position on the sample. By obtaining a normalized correlation value, etc., the template matches the image part. This is a technique for specifying a desired pattern position based on the degree.
- the movement amount calculation unit 906 calculates the actual movement amount based on the difference between the position specified by pattern matching and the position where the template in the visual field before movement is cut out. A specific calculation method will be described later.
- the image distortion amount calculation unit 907 calculates the image distortion amount based on the plurality of movement amounts obtained by the movement amount calculation unit 906. A specific calculation method will be described later.
- a method for evaluating image distortion using a plurality of images acquired before and after the movement of the FOV will be described.
- a partial overlapping area is provided between the first image acquired before the movement of the FOV and the second image acquired after the movement, and this area is set as an evaluation area for distortion.
- an image A101 of a certain visual field on the sample is acquired.
- the visual field is moved, for example, in the right direction by the moving amount of the visual field (about 100 nm) (the moving amount 103 of the visual field), and the image B106 is acquired.
- the visual field of the image A101 and the visual field B102 of the image B overlap.
- the position where the circular pattern 105 appears in the image A is shifted to the left in the image B by the movement amount 107 (100.1 nm) of the circular pattern. Since the movement amount 103 of the square pattern is not accurately known, the movement amount 107 (100.1 nm of the circular pattern does not necessarily coincide with the movement amount 108 (102.1 nm of the square pattern). ) Is requested.
- the movement amount of the round pattern and the movement amount of the square pattern should be completely identical. This is because the round pattern and the square pattern do not move during the acquisition of the two images A and B, and the positional deviation of the pattern due to the visual field movement should be constant regardless of the location and pattern shape in the image. That's why.
- the image distortion in the lateral direction occurring near the square pattern (104) can be considered to be about 2% larger than that near the round pattern (105). This can be calculated from Equation 1 below.
- ⁇ A merit of this method is that dimensional calibration is not necessary for the pattern on the sample. There are also no restrictions on the size and shape of the pattern. Therefore, there is an advantage that the cost required for sample preparation can be reduced. In addition, since the image distortion distribution of the entire screen can be obtained collectively from basically only two images, there is an advantage that the time and cost required for image distortion measurement can be reduced.
- the visual field movement is in the horizontal direction, but it may be in the direction of 45 degrees obliquely. Then, the visual field movement in the horizontal direction and the vertical direction can be performed simultaneously. Thereby, it is possible to measure the image distortion in the horizontal direction and the vertical direction at the same time, and there is an advantage that the measurement time can be shortened.
- the movement of the visual field is performed by beam shift in an electron microscope, for example. Beam shift is to move the observation field of the electron microscope without moving the sample.
- the moving direction when moving from the visual field A to the visual field B is, for example, a direction of 45 degrees diagonally upward to the right in the visual field A.
- the moving length is, for example, a length corresponding to about one-tenth of the length of the visual field A in the vertical and horizontal directions. For example, if the field of view is 0.7 ⁇ m in length and width, it is 0.07 ⁇ m on the right side and 0.07 ⁇ m on the top side.
- Fig. 2 shows a flowchart of image acquisition necessary for image distortion measurement.
- a signal or signal for starting measurement (step 201) is sent to the apparatus.
- the sample is moved to the visual field A by moving the optical system or the like (step 202).
- the image A is taken with the field of view A and stored in the storage device (step 203).
- it moves to the visual field B (step 204).
- the image B is taken and stored in the storage device (step 205).
- the sample for image observation includes as many patterns and patterns with characteristic shapes as possible.
- a sample called black silicon in which a silicon wafer is dry-etched to form irregularities with a size of several to several tens of nm on the surface, is used as a sample.
- FIG. 3 shows an electron microscope image 301 of black silicon as an example of a sample for image distortion measurement. The length of one side of the image corresponds to about 0.7 ⁇ m.
- the observation conditions of the electron microscope are that the acceleration voltage is 800 V, the electron beam current is 8 pA, the magnification is 200,000, the number of integrated images is 64, and the screen configuration pixels are 512 rows ⁇ 512 columns.
- a sample in which semiconductor device hole patterns with varying shapes are arranged at high density may be used.
- a sample in which gold is slightly deposited on a silicon chip and a granular pattern is irregularly arranged may be used.
- FIG. 4 A display example of the image distortion distribution is shown in FIG.
- the X component and Y component of each vector represent the X direction component and Y direction component of the distortion, respectively. Since the length of the arrow in the lower right of the distribution display diagram 401 corresponding to a vector corresponds to a distortion ratio of about 1%, if this length is compared with the length of each vector, the approximate magnitude of the distortion is visually determined. I can know.
- Measured image distortion correction method The simplest method is a correction method based on the vector distribution obtained above. For example, pixel information at a specific location in an image is not correct information because it is actually affected by distortion. The pixel information can be treated as pixel information that has been returned to its original position by the magnitude and direction of a vector in the vicinity of the location.
- the position of the extracted pixel is not necessarily correct and is moved by the influence of image distortion. Should be. Therefore, the X component and Y component of each extracted pixel coordinate are restored to the original amount by only the X component and Y component of the distortion vector in the vicinity of the pixel. By doing so, the original correct extraction pixel distribution can be obtained.
- This method of image distortion measurement and correction can be applied not only to the electron microscope described so far, but also to an optical microscope. Further, the present invention can be applied to other measuring instruments and image processing apparatuses that handle images.
- the starry sky can be used instead of the black silicon in FIG.
- an image A is an observation image of the starry sky when the astronomical telescope is directed in a certain direction.
- the image B is an image observed by moving the astronomical telescope by a minute angle therefrom.
- satellites can use satellite photos of areas where characteristic buildings on the surface of the city are dense.
- an artificial satellite scans the surface of the earth and shoots, two satellite photographs are taken at short intervals, and the images are compared by the method of this embodiment. Can be measured numerically. Based on this, image distortion can be corrected by the method of this embodiment. This is because the arrangement of buildings on the ground surface can be regarded as unchanged if the interval is short.
- FIG. 5 is a diagram for explaining the principle that the position of the pattern expressed in the field of view changes before and after the field of view moves.
- the left diagram in FIG. 5 is a diagram for explaining the coordinates of the specific area 504 when the address of the upper left vertex of the field of view is (0, 0) (in the case of judging by the number of pixels, (1, 1)).
- the right figure of FIG. 5 is a figure explaining the coordinate of the specific area
- the visual field 501 is moved in the movement direction 503 to move the visual field to the position of the visual field 502 will be described.
- the visual field is moved by (xs, ys) in the upper right direction of the drawing.
- the image distortion amount calculation unit 907. calculates image displacement vectors before and after the visual field movement.
- FIG. 14 is a diagram illustrating an example in which the position (movement amount) of a certain part (reference position) of the visual field is measured after the visual field is moved.
- the image is shifted 100 nm in the right direction and 100 nm in the upward direction by the image shift.
- the reference position 1402 in the visual field 1401 before the movement should be located at the reference position 1404 in the visual field 1403 after the movement.
- the actual reference is located at the position moved to +0.2 nm in the X direction and ⁇ 0.5 nm in the Y direction (when the upper left corner of the field is (0, 0) point).
- Position 1405 may be positioned. In FIG. 14 and the like, the positional deviation is exaggerated to facilitate visual understanding.
- FIG. 13 is a diagram illustrating an example in which the movement amount evaluation position 1301 is set at a position different from the reference position 1402. Similar to the reference position 1402, the movement amount evaluation position 1301 before the visual field movement should be located at the reference position 1302 in the visual field 1403 after the movement. However, in actuality, compared to the field of view before movement, a movement amount evaluation position 1303 after movement is positioned at +0.8 nm in the X direction and -2.1 nm in the Y direction. Based on such a result, the movement amount evaluation position is evaluated. First, the evaluation value in the X direction can be obtained as follows.
- X is an evaluation value of distortion in the X direction
- y is an evaluation value of distortion in the Y direction.
- the distortion evaluation value is obtained by calculating the ratio of the actual movement amount (change amount) between the reference position and the movement amount evaluation position, but the present invention is not limited to this.
- the amount difference may be used as the evaluation value.
- classification such as ranks 1, 2, 3, 4,... May be performed according to the ratio and the size difference, and the ranks may be used as evaluation values.
- the reference position can be more accurately identified as the position with less movement before and after visual field movement can be identified, so it is desirable to find and select such a position. .
- FIG. 15 is a diagram for explaining an example of a distortion distribution diagram, and shows an example in which regions are classified according to the degree of distortion.
- the region 1501 surrounded by the alternate long and short dash line is a region where distortion is large (distortion evaluation value is larger than the first threshold value), and the region 1502 surrounded by the dotted line is moderate distortion (distortion).
- the distortion evaluation value is equal to or smaller than the second threshold.
- an area By performing such a distribution display, it is possible to specify a measurement region setting and a measurement value correction region while visually confirming a region in which deformation of the pattern edge is a concern due to distortion. Note that the same effect can be obtained by selectively displaying only the address of the part considered to have a large distortion. More simply, only information relating to the movement amount of the movement amount evaluation position may be distributed and displayed.
- the distribution information may be obtained based on the evaluation value obtained based on Equations 3 and 4, or the distribution information may be obtained based on the difference between the visual field movement amount and the movement amount of the movement amount evaluation position.
- the distortion evaluation value is obtained based on the ratio or difference between the reference position and the visual field movement amount evaluation position. It is desirable.
- FIG. 24 is a flowchart for explaining the process.
- a standard sample (not shown) previously placed on the sample stage 1101 is positioned in the field of view of the SEM (step 2401).
- the pattern included in the standard sample has a guaranteed absolute dimension, and has a pattern width of 25 nm or 50 nm, for example.
- the visual field position is set so that the reference position (reference region) 2503 assigned in the visual field 2501 is positioned in the pattern 2502.
- the size (magnification) of the visual field is the same as that of the image for which the above-described movement amount evaluation is performed.
- the electron beam is scanned to acquire the SEM image or the dimension value of the pattern (step 2402).
- a magnification calibration value (or scanning width calibration value) is calculated based on the ratio between the obtained dimension value and the dimension value of the pattern 2502 (step 2403). Since the dimension value of the pattern 2502 is guaranteed, the scan width is adjusted so that the measurement result matches the guaranteed dimension value.
- the adjusted scanning signal value (or correction coefficient) is stored as an apparatus condition (step 2404).
- An image obtained by beam scanning using the scanning signal calibrated as described above can be defined as an image having no magnification distortion at least in the reference region. Therefore, it is possible to accurately specify the distortion of each movement amount evaluation position by executing the processing illustrated in FIG. 10 with the apparatus conditions.
- FIG. 6 illustrates a template for pattern matching by cutting out the reference position of the image before moving the visual field (first image) or the two-dimensional area of the movement amount evaluation position (first position) as a specific area
- the template setting unit 904 illustrated in FIG. 9 cuts out the specific area 602 of the first image 601 to create a template 603.
- the extracted specific region is subjected to binarization and smoothing as necessary, and is stored in the template storage unit 908 as a template.
- pattern matching using the template 603 created previously is executed on the second image 604.
- the template setting unit 904 sets a pattern matching search region 605 using a position 606 shifted by the visual field movement amount from a position corresponding to the first position of the second image 604 as a base point. Since the amount of visual field movement is known and the amount of distortion is extremely small compared to the size of the visual field, the search area 605 can be made small compared to the second image. Of course, the entire second image can be used as a search area, but it is desirable to set a partial area as a search area from the viewpoint of improving the efficiency of the matching process.
- the difference between the matching position on the second image 604 and the position where the template before the visual field movement is cut out, or the matching position on the second image, and the ideal movement By calculating a difference from the position, an evaluation value of distortion in the x and y directions is calculated.
- This calculation result is stored in the calculation result storage unit 909. Since the first image and the second image have the same magnification (same field size), the template (first image) and the template position (second image) are formed under substantially the same conditions. Thus, highly accurate matching can be performed.
- the left figure of FIG. 12 is a figure explaining the example which calculates
- the left diagram in FIG. 12 is an example in which a reference position 1203 and eight movement amount evaluation positions 1205 are set, and the right diagram in FIG. 12 illustrates an example in which a reference position 1203 and 399 movement amount evaluation positions 1206 are set. It is a figure to do.
- the part may be selectively set as an evaluation target.
- the left figure of FIG. 12 is an example, and the number of calculation steps can be reduced by partially setting the movement amount evaluation position instead of the whole.
- the evaluation positions do not overlap each other in the example of the left figure in FIG. 12, it is also possible to make the evaluation by overlapping the two-dimensional regions to be cut out and overlapping the positions.
- FIG. 10 is a flowchart for explaining the image distortion evaluation process.
- apparatus conditions such as an image acquisition condition for distortion evaluation and a distortion evaluation position condition are set (step 1001).
- a first image is acquired based on the set device conditions (step 1002).
- the visual field is moved (step 1003), and the second image is acquired at the second visual field position (step 1004).
- a region serving as a template for performing pattern matching on the second image is extracted from the first image (step 1005).
- the template may be extracted immediately after step 1002.
- step 1006 using the template extracted from the first image, template matching is performed on the second image (step 1006), and the position of the same region as the template is specified in the image after visual field movement.
- the amount of movement is obtained (step 1007).
- the template matching is performed for a plurality of predetermined positions (step 1008), and the position information is stored (step 1009).
- black silicon as illustrated in FIG. 3 is used as a sample for obtaining the strain evaluation value.
- a sample 1103 containing black silicon is placed in the SEM. It may be arranged on the sample stage 1101 for arranging the sample 1102.
- a pre-exhaust chamber (load lock chamber) 815 and a mini-en 817 are connected to the sample chamber 807 through a vacuum valve 814, particularly in an SEM for semiconductor measurement and inspection.
- the sample 818 containing black silicon may be kept in the miniene 817 and may be carried into the sample chamber 807 as necessary.
- Black silicon is a sample that is particularly suitable for the strain evaluation described in this embodiment because many patterns that can be identified by pattern matching are arranged in the field of view. If there is, it can be applied instead of black silicon. Further, the magnification calibration sample may be disposed adjacent to the black silicon.
- FIG. 26 is a conceptual diagram of a method for calculating a movement amount of a plurality of parts between the two visual fields described above.
- the first field of view 2602 is positioned on the first region 2601 on the sample to acquire the first image, and the position differs from the first region 2601 and a part thereof is superimposed.
- a second image is acquired by positioning the second visual field 2606 in the second region 2605 to be acquired.
- a template for pattern matching is created by cutting out a first portion 2604 corresponding to a specific region 2603 on the sample in the first image, and the template is used on the second image. Template matching is performed to specify the position of the second portion 2608 on the second image.
- the distance between the position specified by template matching and the measurement point 2607 corresponding to the first portion of the first image on the second image is obtained.
- the movement amount of each part is obtained by performing in the overlapping region of the first visual field 2602 and the second visual field 2606.
- the sizes of the first visual field 2602 and the second visual field 2606 are the same, and the apparatus conditions for scanning both visual fields are the same except that the scanning positions are slightly different. That is, since the first image and the second image are acquired under substantially the same conditions, the distortion distribution can be reproduced under substantially the same conditions, and further, the relative position of each part can be shifted slightly, thereby Distortion can be manifested.
- FIG. 16 is a diagram illustrating an example of a technique for extracting a contour line from a pattern image formed based on detected electrons.
- This outline extraction step may be performed by the condition setting device 704 or may be performed by the control device 710 connected to the SEM.
- an SEM image 1601 is formed by SEM (step 1701).
- a first contour line (not shown) is extracted from the white band 1602 corresponding to the edge portion of the pattern on the SEM image (step 1702).
- a method for extracting the first contour line a method of thinning the edge portion based on the luminance distribution of the white band 1602 can be considered.
- the layout data 1603 and the first contour are superimposed by vector data comparison or pattern matching between the formed first contour and the layout data 1603 included in the device design data (Ste 1703).
- the layout data 1603 is line segment information of design data stored in the GDS format or the like.
- the luminance distribution information collection area 1604 is set to be perpendicular to the first contour line, and the luminance distribution 1605 is detected (step 1704).
- the luminance distribution 1605 is detected (Step 1705).
- a method for forming an accurate contour line independent of image distortion by further correcting the position of the point defined as the second contour line position 1606 using the distortion distribution information 1607. suggest.
- the distortion distribution information 1607 is information obtained at a plurality of movement amount evaluation positions, and the distortion distribution information 1607 in FIG. 16 schematically represents information obtained at a plurality of movement amount evaluation positions. .
- a dotted arrow is a distortion vector, and a solid arrow is a correction vector. Both are in a contradictory relationship.
- Such strain distribution information 1607 is read (step 1706), and the position of each contour point (second contour position 1706) is corrected (step 1707) as exemplified in the correction screen 1608.
- a final contour line (third contour line) is formed by connecting the contour points subjected to position correction (step 1708).
- the movement amount of each contour point with respect to the distortion distribution information 1607 may be set for each contour line formation, or a relational expression indicating the relationship between the distortion evaluation value and the movement amount is prepared in advance. Alternatively, correction may be made based on the relational expression. Or you may make it correct
- FIG. 18 is a diagram for explaining a specific example thereof.
- a length measurement box 1804 is set. At this time, the length measurement box 1804 recorded in advance from the strain distribution information 1802 and the strain information 1805 at the position corresponding to the area between them are read.
- the distortion information 1805 includes distortion information of three small areas 1806, 1807, and 1808, and each small area stores respective distortion information.
- the strain information may be replaced with an expansion / contraction rate having dimensions in the length measurement direction (X direction in this example).
- the expansion / contraction rates of the small regions 1806, 1807, and 1808 are k1, k2, and k3, respectively, the length measurement value CD1 after distortion correction can be obtained as follows.
- CD1 k1 ⁇ A + k2 ⁇ B + k3 ⁇ C (Formula 5) According to the method as described above, it is possible to perform accurate pattern measurement regardless of the presence of image distortion.
- FIG. 21 illustrates an example of an image in which four patterns of SEM images (or contour lines 2102 formed based on SEM images) created by changing process conditions and a pattern figure 2103 obtained by simulation are superimposed. It is a figure to do. If there are a plurality of patterns at different positions in one FOV 2101 and there is image distortion, the accuracy of the comparison result at each position may decrease. Therefore, as illustrated in FIG. 16, by correcting the SEM image or the contour line according to the image distortion, it is possible to realize a high-precision comparison regardless of the image distortion.
- FIG. 19 is a block diagram illustrating a process of comparing a simulation result and an SEM image based on distortion correction.
- the example of correcting the contour line based on the SEM image has been described.
- the pattern figure obtained from the simulation result may be corrected.
- the simulation result, the contour line, and the distortion distribution information are displayed in a superimposed manner, so that a portion having a divergence between the simulation result and the SEM image can be simulated. It is possible to easily visually identify the cause or whether it is caused by the SEM or the cause.
- the divergence between the simulation result and the SEM image is a location where the amount of distortion is greater than or equal to the predetermined value (ie, a location where AND of both can be taken (Class 1))
- a location where the amount of distortion is less than the predetermined value but the distortion amount is greater than or equal to the predetermined value (Category 2) is considered to be a location where the accuracy of the comparison verification result should be re-verified, so that the location can be easily determined. It is preferable to further display the classification result on the image.
- the above classification is performed by the information classification unit.
- FIG. 22 is a diagram for explaining an example of a processor that selects a portion to be subjected to distortion evaluation selectively from a plurality of regions in the FOV based on measurement or identification of an examination site.
- measurement and inspection apparatuses represented by CD-SEM
- measurement and inspection are performed based on an operation program of the apparatus called a recipe. That is, since the locations to be measured and inspected are determined in advance, the strain evaluation can be made more efficient by selectively performing the strain evaluation at the locations.
- the measurement position specifying unit 2202 extracts measurement or inspection position information in the FOV from the recipe information. Based on the extracted information, the distortion evaluation position setting unit 2203 uses the movement amount evaluation position corresponding to the measurement position and the reference position.
- the image acquisition condition setting unit 2204 sets apparatus conditions for image acquisition based on the position information.
- a first image before moving the visual field and a second image after moving the visual field are acquired by a plurality of SEMs (three in this example). Then, image distortion evaluation is performed in each apparatus, the evaluation value is determined as a machine difference, and the information is stored in a predetermined storage medium.
- the origin of the existence of image distortion can be determined appropriately, and further, machine difference measurement can be performed stably regardless of image distortion.
- each displacement amount obtained by the displacement amount calculation unit 906 is used, an image distortion amount calculation unit 907 obtains an evaluation value by calculations such as Equation 2 and Equation 3, and image displacement vectors before and after the visual field movement are obtained. (Image distortion distribution 401 in FIG. 4) was calculated.
- the distortion rate may be a case where the acquired pattern arrangement to be measured or the outline position of the pattern does not directly indicate the movement amount due to image distortion or the distortion distribution information 1607.
- the distortion vector 1607 illustrated in FIG. 16 is an example, but in order to obtain this distortion vector, it is necessary to consider the image distortion component and the image distortion component obtained by the moving direction of the visual field shift.
- FIG. 27 shows image examples 2701 to 2703 and a beam image 2704 of a scanning line when there is no image distortion. Since there is no distortion, there is no change in the size and shape of the pattern in the image.
- Each arrow of the beam image 2704 in the scanning electron microscope images the scanning speed and direction in each area, and a series of arrows indicates one scanning line.
- the scanning speed is the same for all scanning lines, constant in the X direction, and zero in the Y direction.
- the Y direction interval of each scanning line is constant, and the X coordinate of the starting position of each scanning line is the same.
- the local distortion assumed in the scanning electron microscope can be classified mainly into the following four components.
- the first example of distortion is a dimensional change in the X direction due to X direction magnification distortion.
- the line width dimension of the vertical line 2701 having a uniform width varies like the vertical line 2801 due to image distortion, but the line dimension of the horizontal line 2701 of the uniform width does not vary like the horizontal line 2802.
- the micro square pattern 2703 has a larger dimension in the X direction like the pattern 2803 when the X direction magnification distortion rate is positive.
- the X-direction magnification distortion rate is defined by the following expression, where the X-direction dimension of the pattern 2803 without distortion is X 0 and the dimensional difference due to distortion is ⁇ x.
- X direction magnification distortion rate DMx ⁇ x / X 0 (Formula 6)
- the main cause of this distortion is that the scanning speed (X component) when moving in the X direction from the left end of the image to the right end by beam deflection as in the beam image 2804 is non-uniform.
- the X direction magnification distortion rate is negative in an area faster than the scanning speed in the reference image area, while the X direction magnification distortion rate is positive in an area slower than the reference operation speed.
- a second example of distortion is a change in dimension in the Y direction due to double distortion in the Y direction.
- the line width dimension of the horizontal line 2902 varies, and the line dimension of the vertical line 2901 does not vary.
- the small square pattern 2903 has a large dimension in the Y direction when the Y direction magnification distortion is positive.
- the Y-direction magnification distortion rate is defined by the following expression, where Y 0 is a dimension in the Y direction of the pattern 2903 without distortion, and ⁇ y is a dimensional difference due to distortion.
- Y direction magnification distortion rate DMy ⁇ y / Y 0 (Expression 7)
- the main cause of this distortion is that the intervals between the scans are not equal due to disturbance noise synchronized with the power supply frequency as in the beam image 2904.
- the adjacent two upper and lower scanning intervals are determined by the set Y magnification.
- the Y-direction magnification distortion rate is negative in an area where there is Y-direction magnification distortion and the lower scanning line is below the relative position determined by the Y magnification, and conversely the Y-direction magnification distortion rate is positive in the upper area. .
- a third example of strain is a shape change due to an X-direction shear strain.
- the line shape of the vertical line 3001 changes.
- the line dimensions do not vary with the vertical and horizontal lines 3002.
- the small square pattern 3003 is an example in which the X direction shear strain is positive, but the shape changes and the area does not change.
- the X-direction shear strain rate is defined by the following formula, where Y 0 is the dimension in the Y-direction in the non-distorted image of the minute square pattern 3003, and X-direction shear deviation due to the distortion is ⁇ s.
- the main cause of this distortion is that the relative position in the X direction of each scanning line varies due to disturbance noise synchronized with the power supply frequency as in the beam image 3004.
- the shear strain rate is determined by the relative position in the X direction of the lower scanning line with respect to the upper scanning line. In the area where the position of the lower scanning line is shifted to the right, the X direction shear strain is positive, and conversely, in the area shifted to the left, the X direction shear strain is negative.
- a fourth example of the strain is a shape change due to the Y-direction shear strain.
- the line shape of the horizontal line 3102 changes.
- the line dimensions do not vary for the vertical line 3101 and the horizontal line.
- the small square pattern 3103 is an example in which the Y-direction shear strain is positive, but the shape changes and the area does not change.
- the Y-direction shear strain rate is defined by the following equation, where X 0 is the dimension in the X-direction in the non-distorted image of the minute square pattern 3103, and X-direction shear deviation due to strain is ⁇ t.
- Y direction shear strain rate DSy ⁇ t / X 0 (Equation 9)
- the main factor of this distortion is that the scanning speed when moving in the X direction from the left end to the right end of the image by beam deflection has a Y component as in the beam image 3104.
- the Y direction shear strain is positive in an area where the Y direction velocity is negative (downward vector), and conversely, the X direction shear strain is negative in an area where the Y direction velocity is positive (upward vector).
- the specific measurement method and the component of the measured strain rate will be described later, but the measured strain rate distribution is a relative value of the strain from the reference. Therefore, in order to determine the distortion rate at each measurement point, it is necessary to determine a reference for no distortion (the distortion rate is 0).
- the distortion reference may be a specific location in the image, or may be an average distortion over a somewhat wide area.
- the magnification distortion reference the magnification distortion rate distribution is measured with reference to the area to be measured in the magnification calibration shown in FIG.
- the standard of shape distortion is an area calibrated with, for example, a rectangular standard sample.
- the average value of the distortion rate of the entire image can be set to no distortion.
- an example in which the image center area is set as a distortion standard no shear distortion
- FIG. 32 shows an example in which the Y-direction magnification distortion rate and the X-direction shear strain are calculated using two images whose visual field has been moved in the Y-direction.
- the first sheet image A3201
- the square pattern 3202 is a pattern at a reference position for image distortion, and the coordinates a1 in the image A are (450 nm, 400 nm).
- the circular pattern 3203 is a pattern at a position where image distortion is evaluated, and the coordinates a2 in the image A are (300 nm, 200 nm).
- the coordinate b1 of the square pattern 3206 in the image B is (450 nm, 500 nm). Move 100 nm. Therefore, the movement vector (Xs, Ys) of the reference position is (0, 100 nm).
- the circle pattern in the image B has coordinates (300 nm, 300 nm) that are positions that move 0 nm to the right and 100 nm upward as in the case of the square pattern.
- the coordinates b2 in the image B of the round pattern are (302 nm, 301 nm), and the round pattern is moved 2 nm to the right and moved 101 nm upward.
- the movement vector (Xa, Ya) of the evaluation position is (2, 101 nm).
- the distortion rate at these evaluation positions is the value of the area from coordinates b1 to b2 in the image.
- this measurement result can also be set as a measurement result of the distortion rate with the coordinate b (300 nm, 250 nm) being an intermediate coordinate between two points as a measurement point.
- FIG. 33 shows an example in which the X-direction magnification distortion rate and the Y-direction shear strain are calculated using two images whose visual field is moved in the X direction.
- the first sheet image A3301
- the square pattern 3302 is a pattern at the image distortion reference position, and the coordinates a1 in the image A are (400 nm, 450 nm).
- the circular pattern 3303 is a pattern at a position where image distortion is evaluated, and the coordinates a2 in the image A are (200 nm, 300 nm).
- the coordinate b1 of the square pattern 3206 in the image B is (500 nm, 450 nm). Move 0 nm. Therefore, the movement vector (Xs, Ys) of the reference position is (100, 0 nm).
- the circle pattern in the image B has coordinates (300 nm, 300 nm) that are positions that move 100 nm to the right and 0 nm upward as in the square pattern, but there is image distortion in the area with the circle pattern.
- the coordinate b2 in the image B of the round pattern is (302 nm, 301 nm), and the round pattern is moved to the right by 102 nm and moved upward by 1 nm.
- the movement vector (Xa, Ya) of the evaluation position is (102, 1 nm).
- + 2% larger than the X-direction movement amount of the reference position means that the X-direction magnification is 102% of the reference position in the area of coordinates b1 to b2 in the image, which is the X-direction magnification. It shows that the distortion rate is + 2%. This is expressed as follows.
- the difference in the Y-direction movement amount between the evaluation position and the reference position is + 1% of the X-direction movement amount of the reference position. This is because the Y-direction shear strain rate is higher than the reference position in the area from coordinates b1 to b2 in the image. If the shear strain rate at the reference position is 0, the Y-direction shear strain rate at the evaluation position is + 1%. This is expressed as follows.
- the distortion rate at these evaluation positions is the value of the area from coordinates b1 to b2 in the image.
- this measurement result can also be used as a distortion rate measurement result with the coordinate b (300 nm, 250 nm), which is an intermediate coordinate between two points, as a measurement point.
- the Y-direction magnification distortion and the X-direction shear distortion obtained by shifting the visual field in the Y direction mainly change in the relative position of each scanning line as in the beam images 304 and 305 in FIGS. It is a cause. Therefore, these distortions fluctuate between scanning lines, and there are many cases where the distribution within each scanning line is small. In this case, since the distortion mainly has a distribution in the Y direction and the distortion distribution in the X direction is small, an average in the X direction is obtained with respect to measurement points at the same Y coordinate in the image, and a measurement value of the same X coordinate is obtained.
- FIG. 34 shows an example in which the distortion rate is displayed as a vector by shifting the visual field in the Y direction using a scanning electron microscope.
- the X component of the vector is the X direction shear strain rate
- the Y component of the vector is the Y direction magnification strain rate.
- Each component has a distribution in the Y direction, and the distribution in the X direction is small.
- FIG. 35 shows an example in which each vector component is averaged in the X direction and the Y direction dependency is graphed. Thereby, the Y direction dependence of the X direction shear strain rate and the Y direction magnification strain rate can be detected.
- the X-direction magnification distortion and the Y-direction magnification distortion obtained by shifting in the X direction are constant when the scanning speed when moving in the X direction from the left end to the right end of the image by the beam images 204 and 505 in FIG.
- the main factor is not. Therefore, these distortions have a distribution within the scanning lines, and the distribution between the scanning lines is often small.
- the distortion mainly has a distribution in the X direction and the distortion distribution in the Y direction is small, the average of the measurement points at the same X coordinate in the image is averaged in the Y direction and approximated to the measurement value of the same X coordinate.
- FIG. 36 shows an example in which the distortion rate is displayed as a vector by shifting the visual field in the X direction using a scanning electron microscope.
- the X component of the vector is the X direction magnification distortion rate
- the Y component of the vector is the Y direction shear strain rate.
- Each component has a distribution in the X direction and a small distribution in the Y direction.
- FIG. 37 shows an example in which each vector component is averaged in the Y direction and the X direction dependency is graphed. Thereby, the X direction dependence of the X direction magnification strain rate and the Y direction shear strain rate can be detected.
- FIG. 38 shows an example of distortion calculated using two images whose visual fields are moved simultaneously in the X and Y directions.
- the first sheet image A3801
- the square pattern 3802 is a pattern at the image distortion reference position, and the coordinates a1 in the image A are (400 nm, 400 nm).
- the circular pattern 3803 is a pattern at a position where image distortion is evaluated, and the coordinates a2 in the image A are (200 nm, 200 nm).
- the coordinate b1 of the square pattern 3806 in the image B is (500 nm, 500 nm).
- the movement vector (Xs, Ys) of the reference position is (100 nm, 100 nm).
- the circle pattern in the image B has coordinates (300 nm, 300 nm) that are positions that move 100 nm to the right and 100 nm upward, like the square pattern, but there is image distortion in the area with the circle pattern.
- the coordinate b2 in the image B of the circular pattern is (304 nm, 302 nm), and the circular pattern is moved 104 nm to the right and 102 nm upward.
- the movement vector (Xa, Ya) of the evaluation position is (104 nm, 102 nm).
- These distortions may be distortions with the coordinate B (250 nm, 250 nm), which is an intermediate coordinate between two points, as a measurement point, instead of the value of the area of coordinates b1 to b2 in the image.
- FIG. 39 shows an example in which the distortion rate is displayed as a vector using a scanning electron microscope by shifting the visual field simultaneously in the X direction and the Y direction.
- the X component of the vector is the sum of the X direction shear strain rate and the X direction magnification strain rate
- the Y component of the vector is the sum of the Y direction magnification strain rate and the Y direction shear strain rate.
- the two distortions that are summed tend to have an X-direction distribution and a Y-direction distribution, respectively, and the sum of each component is a distortion distribution obtained by averaging in the Y direction and averaging in the X direction.
- FIG. 40 shows an example in which each vector component is averaged in the X direction and the Y direction and plotted. Thereby, the Y direction dependence of the X direction shear strain rate and the Y direction magnification strain rate can be detected.
- FIG. 41 shows an example of an image rotation angle of 0 °.
- the entire beam scanning is rotated by ⁇ as shown in FIG. Since the X-direction magnification distortion and the Y-direction shear distortion are caused by fluctuations in one scan, it is assumed that the magnification and the scanning angle on the sample are small and have no dependency.
- the Y-direction magnification distortion and the X-direction shear distortion are relative positional deviations between the scanning lines due to disturbance noise, and the movement amount / direction of each scanning line is assumed to have a constant relative value to the sample.
- FIG. 43 shows changes in the Y-direction magnification strain rate and the X-direction shear strain rate when the image is rotated by ⁇ .
- the X-direction magnification strain and the Y-direction shear strain change according to the following equations using each strain at the on-sample scanning angle of 0 °.
- the distortion in the Y direction magnification is shown in FIG.
- the positional deviation amount dy in the Y direction changes with a sine wave with an amplitude of 0.1 pixel and a wavelength of 512 pixel depending on only y in the coordinate system with the lower left corner of the image as the origin. Misalignment due to the distortion caused.
- FIG. 45 shows the Y-direction magnification distortion rate distribution of the image having the positional deviation distribution of Expression 18.
- the square patterns are contracted in the Y direction at 4501 and 4503, and the Y-direction magnification distortion rate is negative, and in 4502, the Y-direction magnification distortion rate is positive in the Y direction. Further, no distortion occurs at 4504 and 4505, and the square remains without distortion.
- the distortion factor DMy in the Y-direction magnification is expressed as a partial differentiation with respect to the displacement dy (x, y) due to the distortion in the Y-direction magnification. In this example, the following equation is obtained.
- the amount of displacement due to the distortion distribution of the magnification in the X direction can be calculated by the same method.
- FIG. 1 An example of X-direction shear strain is shown in FIG.
- the positional deviation amount dx in the X direction changes with a sine wave with an amplitude of 0.1 Pixel and a wavelength of 512 Pixel depending on only y in the coordinate system with the lower left corner of the image as the origin. Misalignment due to the distortion caused.
- FIG. 47 shows the distribution of the shear strain rate in the X direction of the image having the displacement distribution of Equation 18.
- Square patterns 4701 and 4703 have a negative deformation in the X direction shear strain rate, and 4702 has a positive deformation in the X direction shear strain rate.
- 4704 and 4705 deformation due to distortion does not occur, and it remains a square without distortion.
- the Y-direction shear strain rate DSx is expressed as a partial differential with respect to x of the positional shift amount dx (x, y) due to the X-direction double shear strain. In this example, the following equation is obtained.
- the X-direction shear strain rate of this embodiment is integrated by fitting the example 4001 to a function or numerically integrating the detected strain rate.
- Numerical integration uses trapezoidal approximation or Simpson's method depending on the distribution. What is obtained by this calculation is that the positional deviation at the left end of the image is 0, but the standard of positional deviation can be changed by subtracting the entire positional movement amount by the positional deviation amount ⁇ as a reference.
- the amount of misalignment due to the Y direction shear strain distribution can be calculated in the same way.
- the above example shows the case where each distortion is uniform in the X direction or the Y direction, but the same calculation can be performed when the distortion is not uniform. Further, the calculated sum of the positional deviation amounts due to the X-direction magnification distortion, Y-direction magnification distortion, X-direction shear distortion, and Y-direction shear distortion of the measurement point in the image becomes the positional deviation amount of each measurement point.
- the positional deviation amounts of the measurement points A4801, B4802, C4803, and D4804 are a, b, c, and d.
- the positional deviation amount ⁇ of the position (x, y) is interpolated by the following expression.
- FIG. 49 shows a flowchart for calculating the amount of displacement due to image distortion from two images acquired by shifting the field of view.
- FIG. 50 shows the results obtained in
- step 4901 two images with different fields of view are acquired.
- the two images have overlapping areas such as 5001, and the distribution of the distortion rate in the image in step 4902 is measured using the two areas.
- the measurement data may be displayed as a distortion rate vector, such as 5002, or the X component and Y component of the distortion rate vector at each measurement point may be stored as numerical values.
- step 4903 it is determined whether the distortion rate is within the normal range.
- Judgment includes the upper limit of the magnitude of the distortion rate and the upper limit of the difference in distortion rate at adjacent measurement points. If it is out of the range, the image quality of the acquired image, the state of the sample, the hardware state of the electron microscope, etc. are checked as an alert, and the positional deviation distribution is measured again after adjustment. On the other hand, if it is within the range, the process proceeds to step 4904, where calculation of numerical integration or the like is performed for each component of the distortion rate distribution as in 5003 to obtain a displacement distribution due to distortion. In step 4905, the positional deviation amounts of the respective distortion components are synthesized, and a positional deviation amount distribution of each measurement point due to image distortion is obtained as in 5005.
- step 4906 it is determined whether the value and distribution of the positional deviation are within the normal range. If it is out of the range, the image quality of the acquired image, the state of the sample, the hardware state of the electron microscope, etc. are examined as an alert in the same manner as in step 4903, and the positional deviation distribution is measured again after adjustment. If it is within the range, the process advances to step 4907 to store the measurement point positional deviation amount distribution and the image acquisition condition.
- FIG. 51 shows an example of pattern deformation depending on the presence or absence of distortion.
- the distribution vector of the image misregistration vector is 0 at all measurement points as in 5101, and the L / S pattern 5102 imaged under the conditions of 5101 also has no distortion with respect to the shape of the sample. It becomes a pattern.
- An example 5103 of positional deviation vector distribution due to image distortion obtained by the present invention and an example 5104 in which the same L / S pattern as that of 5102 is imaged under the condition having the image distortion of 5103 are shown. Due to image distortion, 5104 has distortion with respect to the shape of the sample, but the amount of movement from 5102 to 5104 without distortion can be calculated from the displacement vector of 5103, and 5102 and 5104 are used. Can be obtained.
- the first method is to move the detected edge point in order to measure the dimension of the pattern.
- the edge point 5202 of the line obtained in the distorted image 5201 is moved to the edge point 5204 with the correction value calculated from the data of the image distortion vector 5103, and the moved edge point 5204 is used. Measure the dimensions of the pattern.
- the corrected image 5203 does not need to be created, and dimension measurement is possible only from 5204.
- the vector 5103 may be fed back as it is, or only the X-direction component of the vector 5103 that contributes to the vertical line size like 5202. Feedback may be provided.
- the second method is correction to the hardware of the electron beam scanning microscope using a distortion rate vector and a displacement vector due to distortion.
- Strain can be classified into X-direction and Y-direction magnification strain and X-direction and Y-direction shear strain.
- FIG. 53 shows a beam image at each distortion.
- the generation source is electrical noise or vibration synchronized with the power supply frequency.
- the Y-direction distribution of the displacement amount due to the X-direction shear strain and the Y-direction magnification distortion is scanned by the electron beam scanning microscope. Correction can be made as in 5305 by feeding back the relative coordinates of the line to the controlling circuit.
- the X-direction magnification distortion is caused by the distribution of the X-direction scanning speed in the scanning line.
- the distortion factor of the X-direction magnification is ⁇ n%.
- a correction value determined from the distortion rate distribution is fed back to a circuit that controls the scanning speed in the X direction.
- Y-direction shear strain occurs when scanning in the X direction has a velocity in the Y direction. (Y-direction scanning speed) / (X-direction scanning speed) ⁇ 100 (%) is the distortion factor of the X-direction magnification, and the correction value determined from the distribution of the measured Y-direction shear strain is the Y-direction scanning speed during scanning. Is fed back to the control circuit. These feedbacks can be corrected as in 5306.
- FIG. 54 shows an example of image distortion correction by hardware correction.
- An image 5401 distorted by image distortion can be obtained by distortion correction, and an image without distortion such as 5402 can be obtained.
- the third method is a method of performing image processing that feeds back a displacement amount due to image distortion to an image acquired for measuring a pattern dimension.
- a distortion-free image 5502 can be obtained by performing software image correction for feeding back an image distortion vector 5103 to an image 5501 distorted by image distortion.
- FIG. 56 shows an example in which an image cannot be corrected by the correction by the image processing using the image distortion vector described so far, since the change of the image distortion is large.
- the L / S pattern which becomes 5102 has a shape change due to image distortion such as 5601 due to the image distortion.
- 5602 in which the change in image distortion is large is 5604 in the image 5603 corrected by the image processing.
- shape changes due to distortion remain. This is mainly due to the fact that the value of the distortion rate detected in the present invention is the average value of the distortion between two points where the field of view between the two acquired images is shifted.
- FIG. 57 shows an example of a distortion detection method in which distortion correction is fed back to an image for measuring distortion.
- An image group (without distortion correction) acquired by shifting the field of view is defined as an image group A (0).
- 0 in parentheses is the number of corrections N.
- a displacement amount distribution due to image distortion calculated using the image set A (0) is defined as a displacement amount distribution Z (0).
- An image set obtained by performing image processing for correcting the shift amount distribution Z (0) for the image set A (0) is referred to as an image set A (1).
- the displacement amount distribution due to image distortion calculated using the image set A (1) is defined as a displacement amount distribution Z (1).
- An image set obtained by performing image processing for correcting the shift amount distribution Z (1) for the image set A (1) is referred to as an image set A (2).
- a displacement amount distribution due to image distortion calculated using the image set A (2) is defined as a displacement amount distribution Z (2).
- FIG. 58 shows an example in which Z (0), Z (1), and Z (2) are obtained as a method for obtaining image distortion correction using these Z (N).
- the sum of the positional deviation distributions Z (0), Z (1), Z (2) is used as a positional deviation distribution sum W (2), and this value is fed back as a correction value. It is expected that 50% is detected in Z (0), 25% is detected in Z (1), and 12.5% is detected in Z (2) with respect to the distortion with the sensitivity of 50% described above. In (2), a distortion of 87.5% is detected and expected to be corrected.
- FIG. 59 shows a flowchart obtained by adding a determination at Z (N) to this method.
- the method shown in FIG. 59 is performed by adding image correction to the image that has been subjected to image correction and adding the image correction to the distortion that has been detected again.
- An example is shown in FIG. Steps 6001 and 6003 to 6007 are the same as steps 5901 and 5903 to 5907, respectively, but only 6002 is changed and the sum W (N) of the deviation amount distribution is corrected by image processing for the image set A (0).
- the image set A (N + 1) was obtained. Even if the repetitive shift amount distribution is obtained in this way, the image processing is performed on the image set A (0) that has not been subjected to image processing.
- FIG. 61 shows an example of a method for storing the measured distortion data. Distortion depends on image acquisition conditions, for example, electron beam acceleration voltage (Vacc), electron beam current value (Ip), magnification (Mag), and image rotation angle (Rot). For this reason, it is necessary to store not only the distortion rate distribution in the image and the data of the displacement amount distribution due to the distortion, but also the image acquisition conditions for calculating the distortion data. Therefore, the image acquisition conditions 6101 to 6104 are displayed as a list in addition to the data No. (or data name).
- Image acquisition conditions 6101 to 6104 are displayed as a list in addition to the data No. (or data name).
- magnification (Mag) and the rotation angle (Rot) of the image it is possible to calculate correction data other than the acquired image condition by calculation.
- the data 6103 is selected and the calculation execution button 6105 is pressed to change the magnification 6107, the Rot 6108, the data No. to be generated
- the correction data 6110 can be calculated by inputting 6109. It is also possible to read the Mag and rotation angle Rot of the image to be corrected before correction, and change the stored data according to the read Mag and Rot to correct it.
- FIG. 1 An example of automatic pattern measurement with an electronic scanning microscope is shown in FIG.
- an automatic measurement parameter 6206 is set, and a cursor indicated by 6204 is set according to the line pattern in the image.
- a condition 6207 such as a cursor size (shape), an edge detection condition, and the number of lines to be measured is set in the automatic measurement parameter 6206.
- 6204 is a cursor for one line, if the number of lines to be measured is set to 3, three lines are detected from the image and measured.
- the cursor may be manually arranged, or may be set to determine the cursor position by detecting the center of the line by image recognition of the measurement recipe.
- edge points of each line are detected as in 6205, line widths are detected at a plurality of points, and for example, an average value of all line widths is output as the line width.
- An example of a method of automatic measurement with a distorted image using a displacement distribution due to distortion measured in the present invention will be described. As shown in FIG. 63, measurement is performed when the images 6201 to 6203 are deformed to 6301 to 6303 due to image distortion. When the cursor 6304 is measured by an automatic measurement parameter 6206 that does not consider image distortion, the measured edge 6306 is detected in accordance with a distorted line.
- an item for setting distortion data No. 6308 is added to the automatic measurement parameter as 6306.
- This is, for example, distortion measurement data registered in advance as shown in FIG.
- distortion data No. 6308 can be registered when setting a recipe.
- the correction based on the image distortion by the automatic measurement may be performed using image processing, or may be performed by moving the position of the edge point 6305.
- a positional deviation vector 6402 is displayed at a measurement point 6401.
- the starting point of the vector coincides with the measurement point 6401 and is a measurement point in the distorted image.
- the end point of the vector is a position displaced due to image distortion. Therefore, in order to correct the edge point detected at the measurement point 6401, the edge point is shifted in the opposite direction by the same length as the positional deviation vector. It is also possible to display by changing colors or changing the thickness according to the vector size, and distinguishing by the vector size. Further, as a criterion for distinction, the X component or Y component of the vector can be used.
- a range is set according to the magnitude of the deviation amount, such as 6403 to 6406, as a display of the distribution of the positional deviation amount.
- it is used to determine an area that can be measured without performing correction in edge detection and contour extraction. For example, when the amount of deviation is large in the order of 6403 ⁇ 6404 ⁇ 6405 ⁇ 6406, an alert is issued if measurement including an edge point at 6406 cannot be performed, or both edge points for measuring the distance between two points are at 6405 or 6406 If it is not possible to measure, an alert can be issued.
- FIG. 65 is a diagram illustrating an example of a GUI screen including a window for displaying an SEM image.
- a display screen is displayed on the condition setting device 704 and the display devices provided in the SEMs 701 to 703, and the setting information set on the GUI screen is transmitted to the image processor 901 or the like and necessary. Processing is performed.
- EPE Error
- a selection button is provided in the GUI screen so that a pattern diagram (Deformed Image) subjected to deformation processing by information (Distortion) and distortion information can be superimposed on an SEM image or contour image.
- Examples 2 and 3 will be described with regard to a technique related to adjustment of a charged particle beam apparatus using a charged particle beam adjustment sample.
- adjustment samples As a result of examining the requirements for charged particle beam adjustment samples (hereinafter simply referred to as adjustment samples), it is necessary to use semiconductor materials such as Si to prevent contamination, and to align the height of the protrusions to reduce errors.
- an irregular pattern having a uniform height can be formed by dry etching a Si substrate having a Si oxide film with a thickness of 10 nm to 0.1 nm formed on the surface under conditions with a high selectivity to SiO 2 . I found it. Note that the side walls of the protrusions are preferably vertical. This example was born based on the above findings.
- FIG. 66, 67, and 73 to 78 A second embodiment of the present invention will be described with reference to FIGS. 66, 67, and 73 to 78.
- FIG. 66, 67, and 73 to 78 A second embodiment of the present invention will be described with reference to FIGS. 66, 67, and 73 to 78.
- FIG. 66, 67, and 73 to 78 A second embodiment of the present invention will be described with reference to FIGS. 66, 67, and 73 to 78.
- FIG. 66 is a schematic view of an adjustment sample 6601 according to the present example, where (a) is a top view and (b) is a cross-sectional view.
- symbol shows the same component.
- an Si substrate 6605 was used as the adjustment sample 6601 of this example in order to prevent heavy metal from being mixed into the semiconductor device via the electron microscope in which the adjustment sample was measured.
- the Si substrate 5 was processed by dry etching using a plasma type dry etching apparatus, and an adjustment sample 6601 having an irregular shape and a fine concavo-convex pattern was produced.
- 66 (a) shows the top surface 6604 of the pattern, and a black region 6603 shows the bottom portion 6608 of the pattern.
- Reference numeral 6606 denotes the height of the convex pattern
- reference numeral 6607 denotes the width (pattern dimension) of the convex part.
- Si substrate is used in this embodiment, a laminated substrate in which a semiconductor layer such as Si is provided on the substrate surface can also be used.
- the adjustment sample having the irregular fine pattern 6621 has the following characteristics. (1) Since the pattern is obtained by processing a Si substrate, there is no fear of heavy metal mixing into the semiconductor device, and the sample is not charged even when irradiated with an electron beam. Since the sample is not charged even when it is irradiated with an electron beam, the acquired image is not distorted by the sample charging, and accurate measurement is possible. (2) The irregular pattern formed on the sample has a flat surface on the upper surface 6604 of the pattern as shown in FIG. 66B, and the pattern height 6606 is aligned. Accordingly, there is no measurement variation of edge sharpness caused by height variation, and the electron microscope can be adjusted with high accuracy and stability.
- FIG. 73 is a flowchart of the manufacturing process of the adjustment sample 6601
- FIG. 74 is a schematic diagram of the sample during the manufacturing process
- (a) is a cross-sectional view of the adjustment sample in step S7301 of FIG. b) shows a sectional view of the adjustment sample in step S7302.
- a thin and uniform Si oxide film 7423 having a thickness of 10 nm to 0.1 nm is first formed on the surface 7422 of the Si substrate 6605 (step S7301).
- This oxide film can be formed on the surface of the Si wafer by wet oxidation or the like.
- the surface of the Si substrate is cleaned at the time of wafer creation, but in order to prevent contamination of the wafer surface and adhesion of foreign substances after wafer creation, A thin and uniform Si oxide film 7423 having a thickness of 10 nm to 0.1 nm is formed by cleaning using ammonia or hydrochloric acid (so-called cleaning based on RCA cleaning). Therefore, the dry cleaning process may be performed as it is without pre-cleaning or thermal oxidation of the purchased clean Si wafer (step S7302).
- a dry etching process is performed on the Si substrate 6605 on which the thin Si oxide film 7423 is formed under the etching conditions for etching Si and having a high selectivity with respect to the Si oxide film 7423.
- an irregular fine pattern is formed on the wafer surface.
- plasma etching using a mixed gas of Cl2 / CHF3 / Ar / O2 was performed.
- FIG. 75 shows an example of a graph showing changes in the Si etch rate 7519 and the Si oxide film etch rate 7520 when the O 2 gas mixture ratio of the mixed gas of Cl 2 / CHF 3 / Ar / O 2 is changed.
- a protective film (oxide film and deposit) 7424 that functions to stop the progress of etching is formed on the surface of the Si substrate 5.
- Si etching proceeds.
- the O2 gas mixture ratio is set to a condition in the vicinity of R 0 as an etching condition in which a part of the Si oxide film 7423 remains. Under these conditions, the Si / Si oxide film has a high selection ratio, and thus Si etching proceeds.
- the upper surface 7422 of the Si substrate 6605 has a flat surface on the pattern upper surface 6604 and the pattern height 6606 forms a uniform fine pattern in a wide area on the wafer. Dry etching was performed so that a part of the flat surface remained as a flat surface of the fine pattern upper surface 6604.
- ashing is performed to remove the residue (oxide film and deposit) 7424 at the time of dry etching from the sample surface (step S7303). Further, in order to remove the Si oxide film on the surface, cleaning is performed with hydrofluoric acid or the like (step S7304). In order to prevent the adjustment sample from being attached to the adjustment sample by the electron beam irradiation after the above treatment, the sample surface can also be oxidized thinly by performing ashing again (step S7305).
- the adjustment sample of this embodiment can be prepared on the entire surface of the Si wafer, or can be cut into a chip having a size of 1 cm ⁇ 1 cm or more and placed on a stage in an electron microscope.
- FIG. 67 is an electron micrograph of an example of the adjustment sample of this example, where (a) is a top view and (b) is a cross-sectional view.
- a dense fine pattern could be formed on the entire surface of the wafer.
- the upper surface of the fine pattern has a flat surface, and the height of the pattern is constant regardless of the location in the wafer.
- this etching condition is a condition in which the selection ratio between Si and Si oxide film is very high, the pattern can be processed into irregularities having sidewalls substantially perpendicular to the Si substrate.
- Cl2 / CHF3 / Ar / O2 is used as a gas to be used, but Cl2 / O2, Cl2 / O2 / Ar, HBr / O2 / CHF3 / Ar, HBr / O2 / Ar, HBr / O2, etc.
- a mixed gas of may be used.
- the length of one side of the image is 0.7 ⁇ m.
- the pattern pitch is about 20 nm to 60 nm
- the pattern size 6607 of the convex portion is about 10 nm to 30 nm.
- the pattern pitch and pattern dimension indicate values in a cross section at an arbitrary position in the top view.
- the width of each convex portion indicates the pattern dimension (for example, reference numeral 6607), and the distance (not shown) between the centers of the respective convex portions indicates the pitch. As shown in FIG.
- the upper surface 6604 of the pattern is substantially flat
- the pattern height 6606 is about 30 nm
- the height 6606 of the pattern upper surface is almost the same height on the entire sample surface. This is because the dry etching process is performed so that the flat surface of the first Si substrate surface 7422 remains as the flat surface of the fine pattern upper surface 6604. Therefore, the height variation of the adjustment sample 6601 is 5 nm or less, and it is possible to measure the edge sharpness with high accuracy, stability, and reproducibility.
- FIG. 76 shows an example of a monochrome gradation histogram of an electron microscope image of the adjustment sample 6601. The higher the gradation of the histogram, the brighter the image, and the lower the gradation, the darker the image.
- the histogram of FIG. 76 is composed of a bright peak 7634 and a dark peak 7635, where the bright peak 7634 is a signal from the pattern top surface 6604 and the dark peak 7635 is a signal from the pattern bottom 6608.
- the gradation difference 7636 between the bright peak 7634 and the dark peak 7635 is a brightness component that changes depending on the height 6606 of the pattern upper surface 6604 from the pattern bottom 6608.
- the variation ⁇ B1 of the dark peak 7635 is the signal variation of the pattern bottom 6608, and is a variation obtained by combining the image noise component ⁇ N and the brightness variation caused by the height variation of the pattern bottom.
- the variation ⁇ B1 is mainly the noise component ⁇ N.
- the variation ⁇ T1 of the bright peak 7634 is signal variation from the pattern upper surface 6604, and is a variation obtained by combining the image noise ⁇ N and the brightness variation ⁇ TH1 due to the height variation of the pattern upper surface.
- the variation ⁇ T1 has 30 gradations
- the variation ⁇ B1 of the dark peak 7635 has about 30 gradations. Therefore, the component ⁇ TH1 due to the height variation of the pattern upper surface is almost zero.
- the variation ⁇ T1 of the bright peak 7634 is preferably not more than twice the variation ⁇ B1 of the dark peak 7635.
- the variation in the sample height can be reduced to, for example, 10 nm or less.
- the component ⁇ TH1 due to the height variation of the pattern top portion of the histogram of the electron microscope is 10 Corresponds to gradations and below. As a result, it is possible to reduce the measurement variation of edge sharpness due to 1/10 or less and perform measurement with high accuracy.
- FIG. 77 shows an example of an electron beam profile acquired from the image of the adjustment sample 6601 of this example. Since this adjustment sample 6601 has a flat portion on the outermost surface of the sample (pattern upper surface 6604) and the pattern height 6606 is uniform, the focal position at the time of image acquisition depends on variations in the pattern height 6606. A stable electron beam profile was obtained with almost no effect.
- the pattern size is 6607.
- the adjustment sample may be a pattern having the following size.
- the pattern pitch includes about 6 nm to 200 nm
- the convex pattern size 6607 includes a fine uneven pattern of about 3 nm to 200 nm
- the height of the fine uneven pattern is constant within a range of 5 to 500 nm. Any height is sufficient.
- FIG. 78 shows the correlation between the edge sharpness measured using this adjustment sample 6601 and the average length measurement value of a standard line pattern.
- FIG. 78A shows an average measurement of the edge sharpness 7851 measured using the adjustment sample 6601 and a standard line pattern when the current value of the objective lens is changed and the focus of the incident electron beam is changed. The correlation with the long value 7852 is shown.
- FIG. 78B shows the correlation between the edge sharpness 7854 measured using the adjustment sample 6601 and the average length measurement value 7855 of the standard line pattern when the astigmatism (stigma) is changed. .
- the cases of edge sharpness 7853 and 7856 measured using a conventional gold particle sample are also plotted.
- the edge sharpness value measured using the adjustment sample 6601 changes in synchronization with the length measurement value of the line pattern that is the pattern to be inspected, and the focus current value and the astigmatism setting value at which the edge sharpness is minimized.
- the condition that the line length measurement value to be inspected pattern is the minimum, so that if the electron beam is adjusted using this adjustment sample 6601, the condition is adjusted to the condition suitable for the length measurement of the inspected pattern. I understand that I can do it.
- a conventional gold particle sample is used, even if the electron beam is adjusted so as to minimize the edge sharpness, it cannot be adjusted to conditions suitable for the measurement of the pattern to be inspected.
- the structure and material of the pattern to be inspected are equivalent to the sample 6601 for adjustment, but the edge sharpness of the gold particle sample is adjusted with a contrast depending on the material of the gold particle and the organic film, or This is because the gold particle sample is a chip-like sample, so that the electric field intensity distribution on the sample surface is changed due to an attachment error to the sample holder as compared with the case of measuring the pattern to be inspected.
- the surface of the adjustment sample can be oxidized thinly (step S7305 in FIG. 73).
- the Si oxide film having a thin surface is a Si oxide film that is thin enough not to be charged by electron beam irradiation.
- the adjustment sample of the present example is an irregular pattern, even if the location where the image was once acquired is observed again, the dimensional variation does not significantly affect the resolution evaluation value and the image distortion measurement result. If you want to make precise measurements, it may be affected. Therefore, it is also possible to place some marks on the adjustment sample and confirm the image acquisition position so that the region once acquired is not evaluated again. If a mark is provided, it is possible to manage which region on the sample has been irradiated with the electron beam by the address on the sample. Since the mark is created at a desired position on the calibration sample, a mask is formed by lithography in the step of creating the mark, and the mark shape is processed by dry etching.
- the step of creating the mark may be performed before the irregular pattern of the adjustment sample is formed or after the irregular pattern is formed.
- an irregular pattern after processing the mark for example, after forming the mark with a concavo-convex pattern having a depth in the range of 100 nm to 1 ⁇ m, the thickness is 10 nm or less in the region where the irregular pattern is formed. A Si oxide film is formed. Thereafter, it can be created according to the flowchart shown in FIG. If the mark is formed after the irregular pattern is formed, the irregular pattern is formed according to the flowchart shown in FIG. 73, and then a resist is applied to protect the region where the irregular pattern remains. Then, after a mask for mark processing is formed by lithography, an uneven pattern having a depth in the range of, for example, 100 nm to 1 ⁇ m is processed by dry etching.
- a charged particle beam apparatus that can be used at the manufacturing site of a semiconductor device has high accuracy. And the charged particle beam apparatus adjustment sample which can be adjusted stably, and its manufacturing method can be provided.
- the third embodiment will be described with reference to FIGS. Note that the items described in the second embodiment and not described in the present embodiment can be applied to the present embodiment unless there are special circumstances.
- a method for measuring and adjusting the performance of an electron microscope using the adjustment sample 6601 described in Example 2 will be described.
- a method for measuring edge sharpness as an evaluation value of the spatial resolution of an electron microscope will be described in detail.
- FIG. 79 is an example of a schematic configuration diagram of a scanning electron microscope 7900 used in this example.
- An electron beam 7903 extracted from the electron source 7901 by the extraction electrode 7902 and accelerated by the acceleration electrode is focused by the condenser lens 7904 and then one-dimensionally or two-dimensionally on the sample 7909 by the scanning deflector 7905. Scanned.
- the electron beam 7903 is decelerated by the negative voltage applied to the sample stage 7908 and is focused by the lens action of the objective lens 7906 and irradiated onto the sample 7909.
- the sample 7909 When the sample 7909 is irradiated with the electron beam 7903, secondary electrons and backscattered electrons are emitted from the irradiated portion. Electrons emitted from the sample are accelerated in the direction of the electron source and collide with the conversion electrode 7912 to generate secondary electrons 7911. Secondary electrons 7911 emitted from the conversion electrode 7912 are detected by the detector 7913, and the output of the detector 7913 changes depending on the amount of secondary electrons detected. In accordance with this output, the luminance of the secondary electron image displayed on the display device 7921 changes. For example, when a two-dimensional image is formed, an image of the scanning region is formed by synchronizing the deflection signal to the scanning deflector 7905 and the output of the detector 7913.
- the scanning electron microscope 7900 illustrated in FIG. 79 includes an image shift deflector for moving the scanning region of the electron beam without moving the sample on the sample stage 7920, and the field of view of the electron microscope is reduced. It can be moved minutely.
- FIG. 79 an example is described in which electrons emitted from the sample are converted once by the conversion electrode 7912 and detected.
- the present invention is not limited to such a configuration. It is also possible to adopt a configuration in which the detection surface of the electron multiplier tube or the detector is arranged on the orbit.
- a sample 7918 including an adjustment sample 6601 for adjusting the electron optical system used in this embodiment is arranged on a sample stage 1101 for arranging the sample 1102 in the electron microscope as illustrated in FIG. You may make it do.
- the height of the sample stage top surface 7262 and the sample height 7263 are matched so that the electric field strength distribution 7265 does not change due to the difference between the sample stage top surface 7262 and the sample height 7263.
- the size of the sample was 5 mm square or more.
- a preliminary exhaust chamber (load lock chamber) 7915 and a mini environment 7917 are connected to the sample chamber 7907 via a vacuum valve 7914.
- the sample 1103 including the adjustment pattern may be put on standby and loaded into the sample chamber 807 as necessary.
- a plurality of apparatuses can be adjusted using a wafer (for example, the sample 1102) having an adjustment pattern formed on the entire surface.
- the advantage of using the adjustment sample formed on the wafer is that the measurement error caused by the sample used can be reduced by adjusting the measurement conditions using the same sample, so the instrumental differences of multiple devices can be accurately measured and adjusted. it can.
- the electron optical system can be adjusted with the same electron optical system setting conditions as when measuring the wafer to be inspected, the measurement accuracy of spatial resolution evaluation values and image distortions can be improved, and the device can be operated with high accuracy. There is an advantage that can be adjusted.
- control device 7924 controls each component of the scanning electron microscope 7900, and on the sample based on the function of forming an image based on the detected electrons and the signal intensity distribution of the detected secondary electrons. It has a function of measuring the dimension of the formed pattern.
- this control apparatus has a function of irradiating an electron beam to 7924 and the adjustment sample 6601 and adjusting the focus and astigmatism of the electron microscope from the signal intensity distribution of the acquired image.
- the control device 7924 calculates edge sharpness as an evaluation value of image resolution from the acquired image, and when the calculated evaluation value is out of a specified range, the scanning electronic device 7924 is based on the measured evaluation value.
- a function of controlling each component of the electron microscope so as to adjust the microscope 7900 is provided. Further, as will be described later, it has a function of measuring magnification and image distortion in the screen by image processing of a plurality of images. Further, the image processing unit 7923 is provided with an image processing function for correcting the distortion of the image acquired by the scanning electron microscope 7900 based on the magnification measurement result and the image distortion measurement result. Further, the control device 7924 has a function of controlling each component of the scanning electron microscope so as to correct the distortion of the image acquired by the scanning electron microscope 7900 based on the magnification measurement result and the image distortion measurement result. ing.
- FIG. 80 shows an example of an edge sharpness measurement flowchart using the adjustment sample 6601.
- inspection conditions for the scanning electron microscope 7900 are set (step S8000).
- the stage 7920 is moved to move to the visual field on the adjustment sample 6601 (step S8001).
- an image of the adjustment sample 6601 is acquired with N setting values obtained by changing the astigmatic setting value of the objective lens 7906 by a minute amount (step S8002).
- the control device 7924 calculates a setting value that minimizes the edge sharpness from the obtained N images, and adjusts the astigmatic setting value to the above value (step S8003).
- an image of the adjustment sample 1 is acquired with N setting values obtained by changing the focus setting value of the objective lens 7906 by a minute amount (step S8004).
- the control device 7924 calculates a setting value that minimizes the edge sharpness from the acquired N images, and adjusts the focus setting value to the above value (step S8005).
- an image for spatial resolution evaluation is acquired and stored in the storage device 7922.
- the control device 7924 calculates the edge sharpness of the acquired image, and determines whether or not the value of the edge sharpness is within a preset normal value range (step S8006). If the edge sharpness of the adjusted image is not within the normal value range, the process from step S8001 to step S8006 is repeated to perform readjustment. Alternatively, an alert is output. If the edge sharpness is within the normal range, save the measurement results. In addition, machine difference evaluation is performed as necessary.
- the adjustment sample 6601 used in this example has a flat surface with a uniform height on the upper surface of the pattern, and a fine pattern having a shape substantially perpendicular to the surface is densely formed. Therefore, a stable and steep electron beam profile could be obtained over the entire image, and an accurate and stable evaluation value of spatial resolution could be obtained regardless of the electron beam irradiation position on the sample.
- an accurate and stable edge sharpness can be calculated by the control device 7924 from an image acquired by irradiating the adjustment sample 6601 with an electron beam. The calculated edge sharpness value is stored in the storage device 7922. Further, the image can be displayed on the image display device 7921 of the scanning electron microscope 7900.
- each of the SEMs 701 to 703 periodically evaluates the spatial resolution using the adjustment sample 6601, displays the transition of the evaluation value, and stores it in the storage unit (for example, the storage medium 706).
- the resolution evaluation value periodically evaluated by each electron microscope is centrally managed together with information from other electron microscopes in the condition setting device 704 via the network.
- the abnormality is notified both in the display unit 7921 of the microscope and the condition setting unit 704.
- one of the inspection conditions is based on an input from the apparatus operator or an instruction from a program incorporated in the control program.
- the adjustment of the electron optical system is commanded, and the lens system is controlled by the signal based on the evaluation value via the control device 7924 of the microscope, and the adjustment is performed so that the evaluation value of the spatial resolution falls within the desired normal range.
- each electron microscope is centrally managed by the condition setting device 704 and periodically adjusted so that the evaluation value of the spatial resolution falls within a desired normal range.
- the condition setting device 704 obtains a machine difference correction coefficient between the devices for the length measurement value of each device, and corrects the length measurement value measured by each device. As a result, it has become possible to reduce the difference between the plurality of electron microscopes in dimensional management of semiconductor device manufacturing.
- the charged particle beam device adjustment sample having an irregular pattern made of a semiconductor material having a uniform height on the substrate surface can be used at the manufacturing site of the semiconductor device.
- a charged particle beam apparatus adjusted with high accuracy can be provided.
- the performance of the charged particle beam apparatus can be monitored and adjusted with high accuracy at any time, highly accurate and stable measurement can be performed.
- the evaluation value of the spatial resolution can be adjusted so as to fall within a desired normal range, the difference in the measured values of a plurality of charged particle beam devices introduced into the semiconductor manufacturing line is reduced, and stable measurement is possible. .
- the fourth embodiment will be described with reference to FIGS. 1 and 81 to 83.
- FIG. Note that matters described in the second or third embodiment and not described in the present embodiment can be applied to the present embodiment as long as there is no special circumstances.
- a method for measuring and adjusting the performance of an electron microscope using the adjustment sample 6601 described in Example 2 will be described.
- a method for measuring a local magnification variation or image distortion in a two-dimensional direction in an image acquired with an electron microscope at high speed and with high accuracy will be described in detail.
- This method is a method of measuring image distortion in a two-dimensional direction using a plurality of images acquired before and after the movement of the visual field.
- a partial overlap region is provided between the first image A 101 acquired before the movement of the field of view and the second image B 106 acquired after the movement, and this region is set as a strain evaluation region.
- Image distortion can be evaluated in a short time by a calculation using a small number of images (at least two images).
- an image A 101 of a certain visual field on the sample is acquired.
- the visual field is moved by, for example, the visual field movement amount 103 in the right direction, and the image B 106 is acquired.
- the position where the circular pattern 105 appears in the image A is shifted leftward in the image B by the movement amount 107: X1 of the circular pattern.
- the movement amount 108: X2 of the square pattern is obtained.
- the lateral image distortion occurring in the vicinity of the square pattern 104 can be measured to be X2 / X1% with respect to that in the vicinity of the round pattern 105.
- the relative magnitude of the image distortion in the vicinity of each position can be measured. If such a pattern is uniformly distributed in the image, a distribution map of image distortion in the image can be created.
- ⁇ A merit of this method is that dimensional calibration is not necessary for the pattern on the sample. Therefore, there is an advantage that the cost required for sample preparation can be reduced. In addition, basically, since the image distortion distribution of the entire screen can be obtained from two images at once, there is an advantage that the time and cost required for image distortion measurement can be reduced.
- the visual field movement is in the horizontal direction, but it may be in the direction of 45 degrees obliquely. Then, the visual field movement in the horizontal direction and the vertical direction can be performed simultaneously. Thereby, it becomes possible to measure the image distortion in the horizontal direction and the vertical direction at the same time, and there is an advantage that the measurement time can be shortened.
- FIG. 81 shows a flowchart of image acquisition necessary for image distortion measurement.
- the scanning electron microscope 7900 described in FIG. 79 in Example 3 was used.
- the stage 7920 is moved to move to the visual field A on the adjustment sample 6601 (step S8102).
- the image A is taken with the field of view A and stored in the storage device (step S8103).
- it moves to the visual field B that partially includes the visual field A and the overlapping visual field.
- the visual field is moved by image shift in the scanning electron microscope 7900, for example.
- the observation field of view may be moved by moving the stage on which the sample is mounted.
- the moving direction when moving from the visual field A to the visual field B is, for example, a direction of 45 degrees diagonally upward to the right in the visual field A.
- the moving length is, for example, a length corresponding to about one-tenth of the length of the visual field A in the vertical and horizontal directions. For example, if the size of the visual field is 0.7 ⁇ m vertically and horizontally, it is 0.07 ⁇ m on the right and 0.07 ⁇ m on the top. Then, the image B is photographed and stored in the storage device 7922 (step S8105).
- N 10
- an image region A ′ in the vicinity of a designated place in the image A is cut out, a template for pattern matching is created, the image B is searched, and the position of an image having high similarity to the template is measured.
- the amount of movement of the pattern can be measured.
- step S8108 it is determined whether the image distortion is in the normal range. If N (out of range), the deflector is adjusted based on the alert or the distortion measurement result. If Y (within range), the measurement result is stored (step S8109).
- the amount of movement of the pattern can also be measured by performing image matching using the phase-only correlation method.
- An explanatory diagram of this measurement method is shown in FIG. First, the entire image A 8201 and the entire image B 8202 whose visual field has been moved are image-matched to measure the movement amount 8203 of the entire image. Then, an image 8206 in the vicinity of the designated place 8205 in the overlapping visual field 8204 is cut out from the image A, and an image 8207 in the vicinity of the designated place 8205 in the overlapping visual field 8204 in the image B is cut out from the image B. Then, the image 8206 and the image 8207 are matched to measure the minute movement amount in the vicinity of the designated location 8205.
- the movement amount of the designated portion can be obtained by combining the movement amount 8203 of the entire image with the minute movement amount in the vicinity of the designated portion 8205.
- the amount of movement of the pattern is measured using the image information of the local area in the overlapping area.
- image matching methods other than those described above may be used.
- the magnification adjusting sample in the present embodiment as shown in the second embodiment, a sample having a pattern with a characteristic shape uniformly in the entire visual field is required. Further, in order to obtain the movement amount of the pattern, it is necessary that the image 8206 in the vicinity of the designated location and the image 8207 include characteristic shape information sufficient to measure the movement amount by image matching. . Furthermore, it is necessary that the sample can stably obtain a clear electron microscope image regardless of the sample region to be measured.
- the adjustment sample 6601 described in the second embodiment has an irregular fine pattern formed on the entire image without gaps, and is suitable as a sample for measuring and calibrating the image distortion described in this embodiment. Table 1 shows a representative value of the pattern dimension 6607 necessary on the adjustment sample corresponding to the magnification of the image measured in the present example and the image area near the designated portion.
- a case where a 32-pixel ⁇ 32-pixel block is cut out as an image area in the vicinity of a designated location and image matching is performed is shown. Since the sample for adjustment has an irregular pattern, the dimension cannot be uniquely determined, but a fine pattern corresponding to the dimension is required. If the image magnification is about 50,000 times, the representative value of the pattern dimension 6607 required on the adjustment sample is 230 nm, but the current electron microscope uses an image magnification of up to about 600,000 times, so the pattern pitch Is desirably as fine as about 20 nm.
- an irregular pattern with a pitch of 10 to 100 nm is formed on the entire surface of the sample, and in an image up to about 600,000 times, the pattern is moved at an arbitrary designated position in the field of view. The amount can be measured.
- FIG. 83 shows an example of a power spectrum 8301 obtained by two-dimensional Fourier transform of one image of the adjustment sample. Assuming that the dimension corresponding to the frequency at which the amplitude value of the power spectrum 8301 is half or more of the maximum amplitude L is the main pattern pitch of the adjustment sample, in this embodiment, the pitch in the image is between 17 and 44 nm. It can be seen that the component is a peak component. In the case of this sample, if the local region for evaluating image distortion is 32 pixels ⁇ 32 pixels, an image with a magnification of about 600,000 times can be evaluated.
- FIG. 4 shows a result of displaying the distribution of image distortion measured by moving the visual field simultaneously in the X direction and the Y direction on the vector display 401.
- a number of designated locations for measuring the amount of movement are arranged on the screen (for example, in FIG. 4, 45 vertically and 14 horizontally, total 630), and the measured distortion amount and direction are displayed as a vector. I was able to.
- the distortion vector display 401 With the distortion vector display 401, the local distortion distribution in the image can be displayed at a glance.
- the X component and Y component of each vector represent the X direction component and Y direction component of the strain, respectively.
- the length of the arrow at the lower right of the vector distribution display diagram corresponds to a strain ratio of about 1%.
- the measured distortion value of the image thus measured is output to an electronic file as inspection information at the time of image acquisition for the image acquired after the distortion measurement. Alternatively, it is stored as inspection information in the storage device 7922 of the scanning electron microscope 7900.
- the control device 7924 of the scanning electron microscope 7900 calculates an adjustment value of the scanning deflector 7905 from the distortion measurement value calculated from the image. It is possible to adjust the scanning deflection amount and correct image distortion at the time of inspection.
- a method for correcting the measured image distortion there is a method of correcting the entire image in the opposite direction based on the vector distribution of the designated portion obtained as described above.
- a distortion vector is calculated for each pixel of the image based on the distortion vector at the designated location, and a correction vector is obtained by inverting the sign of the distortion vector for each pixel. By distorting the image for each pixel according to the correction vector, the image can be corrected without distortion.
- the method for correcting the measured image distortion there is a method of correcting the position information obtained from the image and acquiring the correct position information. For example, the contour line of the structure observed in the electron beam image is extracted, and the position information at the contour points constituting the contour line is calculated. Furthermore, the distortion vector at the calculated position is calculated based on the distortion vector at the designated location measured as described above. Further, the correction vector is obtained by inverting the sign of the distortion vector at each contour point. By correcting the position of the contour line according to the correction vector, an accurate contour line that does not depend on image distortion can be obtained.
- image distortion evaluation is performed in each electron microscope, and the image distortion evaluation results and machine differences are stored in the storage unit. Image distortion evaluation results periodically evaluated by each electron microscope are centrally managed together with information from other electron microscopes in a condition setting device 704 via a network.
- the same measurement result can be obtained with a plurality of electron microscopes by performing the measurement with the image distortion corrected based on the measurement result of the image distortion of each electron microscope.
- Image distortion correction may be performed by the control device 7924 in each scanning electron microscope 7900, or images or measurement results sent from a plurality of electron microscopes via a network are concentrated by the condition setting device 704. Correction may be performed.
- the adjustment samples may be arranged one by one in a plurality of SEMs.
- the samples 7918 including the adjustment samples may be put on standby one by one in the mini-environment 7917 and carried into the sample chamber 7907 as necessary.
- a wafer-like adjustment sample 7919 having a fine concavo-convex pattern formed on the entire surface may be created, and a plurality of apparatuses may be adjusted using the same wafer.
- the adjustment sample 7919 formed on the wafer since the measurement conditions can be adjusted using the same sample, the measurement error due to the used sample can be reduced, so that the machine difference of a plurality of apparatuses can be adjusted small. Further, since adjustment can be performed under the same setting conditions of the electron optical system as when measuring the inspection wafer, there is an advantage that the measurement accuracy and adjustment accuracy of image distortion can be improved.
- the origin of the presence of image distortion can be determined appropriately, and machine difference measurement can be performed stably regardless of image distortion.
- the scanning electron microscope has been described as an example, but the present invention can be applied to all apparatuses using charged particle beams.
- the charged particle beam device adjustment sample having an irregular pattern made of a semiconductor material having a uniform height on the substrate surface can be used at the manufacturing site of the semiconductor device.
- a charged particle beam apparatus adjusted with high accuracy can be provided.
- the performance of the charged particle beam apparatus can be monitored and adjusted with high accuracy at any time, highly accurate and stable measurement can be performed.
- local magnification fluctuations and image distortion evaluation values can be adjusted so that they fall within the desired normal range, so that the difference in measured values of multiple charged particle beam devices installed in a semiconductor manufacturing line is reduced and stable. Measurement is possible.
- this invention is not limited to the above-mentioned Example, Various modifications are included.
- the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.
- a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment.
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Abstract
Description
四角パターン以外にも、特徴的な形状を持つパターンが画像内のその他の位置にあれば、それぞれの位置の近傍における像歪みの相対的な大きさを測定できる。そのようなパターンが画像内にまんべんなく分布していれば、画像内の像歪みの分布図を作ることができる。
また、Y方向についての評価値は、以下のようにして求めることができる。
以上のように、図13の例では、基準位置に対し移動量評価位置は、相対的にX方向に1%、Y方向に2%、画像がひずむことが判る。このような歪み情報に基づいて、二次元的な歪み評価値(√(x2+y2))を求めることができる。また、
arctanθ=(y/x) …(数式4)
を求めることによって、歪みの方向を演算することができる。これらの演算は、図9の画像歪み量演算部907によって、複数の移動量評価位置に対して実施し、その結果を演算結果記憶部909に記憶する。
以上のような手法によれば、像歪みの存在に依らず、正確なパターン測定を行うことが可能となる。
走査型電子顕微鏡では、ビームイメージ2804のようにビーム偏向で画像左端から右端へのX方向の移動する際の走査速度(X成分)が不均一となることがこの歪みの主要因となる。基準となる画像エリアでの走査速度よりも速いエリアではX方向倍率歪み率は負に、一方基準となる操作速度よりも遅いエリアではX方向倍率の歪み率は正となる。
走査型電子顕微鏡では、ビームイメージ2904のように電源周波数と同期した外乱ノイズ等で各走査の間隔が等しくないことがこの歪みの主要因となる。歪みが無い場合の隣接する上下2本の走査間隔は設定したY倍率で決まる。Y方向倍率歪みがあり、下の走査線がY倍率で決まる相対位置よりも下にあるエリアではY方向倍率歪み率は負に、逆に上にあるエリアではY方向倍率歪み率は正となる。
走査型電子顕微鏡では、ビームイメージ3004のように電源周波数と同期した外乱ノイズ等で各走査線のX方向の相対位置が変動することがこの歪みの主要因となる。隣接する上下2本の走査線に関して、上の走査線に対する、下の走査線のX方向相対位置でせん断歪み率が決まる。下の走査線の位置が右にずれたエリアではX方向せん断歪みは正であり、逆に左にずれたエリアではX方向せん断歪みは負となる。
走査型電子顕微鏡では、ビームイメージ3104のようにビーム偏向で画像左端から右端へのX方向の移動する際の走査速度がY成分を持つことがこの歪みの主要因となる。Y方向速度が負(下向きベクトル)のエリアではY方向せん断歪みは正であり、逆にY方向速度が正(上向きベクトル)のエリアではX方向せん断歪みは負となる。
=(Ya-Ys)/Ys×100
=(101-100)/100×100=1% …(数式10)
一方、評価位置と基準位置のX方向移動量の差が、基準位置のY方向移動量の+2%であることは、画像内の座標b1からb2のエリアにおいてX方向せん断歪み率が基準位置よりも+2%大きく、基準位置のせん断歪み率を0とすれば、評価位置のX方向せん断歪み率が+2%であることを示している。これを式で表すと以下となる。
=(Xa-Xs)/Ys×100
=(2-0)/100×100=2% …(数式11)
これらの評価位置の歪み率は、画像内の座標b1からb2のエリアの値である。またこの計測結果を、2点間の中間座標である座標b(300nm,250nm)を計測点とする歪み率の計測結果とすることも可能である。
=(Xa-Xs)/Xs×100
=(102-100)/100×100=2% …(数式12)
一方、評価位置と基準位置のY方向移動量の差が、基準位置のX方向移動量の+1%であることは、画像内の座標b1からb2のエリアにおいてY方向せん断歪み率が基準位置よりも+1%大きく、基準位置のせん断歪み率を0とすれば、評価位置のY方向せん断歪み率が+1%であることを示している。これを式で表すと以下となる。
=(Ya-Ys)/Xs×100
=(1-0)/100×100=1% …(数式13)
これらの評価位置の歪み率は、画像内の座標b1からb2のエリアの値である。またこの計測結果を、2点間の中間座標である座標b(300nm,250nm)を計測点とする歪み率の計測結果とすることも可能である。
走査型電子顕微鏡では、Y方向の視野ずらしで得られるY方向倍率歪みおよびX方向せん断歪みは図3,図4のビームイメージ304,305のように各走査線の相対位置が変動することが主要因である。そのため、これらの歪みは走査線間で変動し、各走査線内の分布が少ない場合が多い。その場合、歪みは主にY方向への分布を持ち、X方向への歪み分布は小さいため、画像内の同じY座標での計測点に関してX方向の平均をとり、同一X座標の計測値と近似し、各計測点の計測ばらつきを低減させることも可能である。走査型電子顕微鏡を用いてY方向の視野ずらしで歪み率をベクトルで表示する例を図34に示す。ベクトルのX成分はX方向せん断歪み率、ベクトルのY成分はY方向倍率歪み率である。各成分ともY方向に分布を持ち、X方向の分布が小さい。各ベクトル成分をX方向に平均して、Y方向依存性をグラフにした例を図35に示す。これにより、X方向せん断歪み率,Y方向倍率歪み率のY方向依存性を検出できる。
ΔX=Xa-Xs=+4nm …(数式14)
に関して、この値が基準位置のX方向およびY方向の移動量より+4%大きいことは、画像内の座標b1からb2のエリアにおいてX方向倍率の歪み率とX方向せん断歪み率の和が+4%であることを示している。この例ではX方向およびY方向の視野ずらし量を同じにしているが、異なる場合でも、数式11および数式12に従う各歪み率の和となる。
ΔY=Ya-Ys=+2nm …(数式15)
に関して、この値が基準位置のX方向およびY方向の移動量より+2%大きいことは、画像内の座標b1からb2のエリアにおいてY方向倍率の歪み率とY方向せん断歪み率の和が+2%であることを示している。この例ではX方向およびY方向の視野ずらし量を同じにしているが、異なる場合でも、数式10および数式13に従う各歪み率の和となる。
走査型電子顕微鏡の歪み特性を用いて、画像全体を角度θ回転させた画像の歪みを、回転なしでの画像歪み計測結果から算出する例を示す。図41に画像回転角度の0°例を示す。画像全体を角度θ回転させた画像を得るためには、図42に示すようにビーム走査全体を-θ回転する。X方向倍率歪みおよびY方向せん断歪みは1つの走査内の変動に起因しているため、倍率および試料上走査角度が小さく、依存性が無いとする。一方、Y方向倍率歪みおよびX方向せん断歪みは外乱ノイズによる各走査線間の相対位置ずれであり、各走査線の移動量・方向は試料に対する相対値が一定とする。図43に画像をθ回転した場合の、Y方向倍率歪み率およびX方向せん断歪み率の変化を示す。試料上走査角度θに応じて、X方向倍率歪みおよびY方向せん断歪みは試料上走査角度0°での各歪みを用いて以下の式で変化する。
=[X方向倍率歪み(θ=0)]×cosθ+[X方向せん断歪み(θ=0)] ×sinθ …(数式16)
Y方向せん断歪み(θ=θ)
=-[X方向倍率歪み(θ=0)]×sinθ+[X方向せん断歪み(θ=0)]×cosθ …(数式17)
また、倍率を変更した画像での歪みに関しては試料に対する相対値が変化しないことから、Y方向倍率歪み率およびX方向せん断歪み率は画像の倍率に比例して大きくなる。
各計測点の歪み率の分布を用いて、歪みによる位置ずれ量を求める方法の説明をする。はじめに位置ずれ量分布と、歪み率の関係を示す。
このときの位置4401,4402,4403ではY方向の位置ずれは無い。一方4404では歪みにより上へ0.1Pixel位置ずれしており、4405では下に0.1Pixel位置ずれしている。
@ここでD=0.1×2π …(数式19)
数式18,数式19の関係より、歪み率DMy(y)から歪みによる位置ずれ量をdy(y)を算出する場合は以下の式となる。
本実施例にて説明するY方向倍率歪み率は図40の例4004のように計測点ごとの歪み率が検出されるため、例4004を関数にフィッティングして積分するか、検出された歪み率を数値積分する。数値積分は分布に応じ、台形近似法やシンプソン法を用いる。この計算によって得られるのは画像左端の位置ずれを0としているが、位置ずれの基準を変更は基準とする位置のずれ量Δだけ全体の位置移動量を引くとことで修正できる。
このときの位置4601,4602,4603ではY方向の位置ずれは無い。一方4604では歪みにより右へ0.1Pixel位置ずれしており、4605では左に0.1Pixel位置ずれしている。
=-Dcos(2πy/512)
@ここでD=0.1×2π …(数式22)
数式21,数式22の関係より、歪み率DSx(y)から歪みによる位置ずれ量をdx(y)を算出する場合は以下の式となる。
本実施例のX方向せん断歪み率は図40の例4001のように計測点ごとの歪み率が検出されるため、例4001を関数にフィッティングして積分するか、検出された歪み率を数値積分する。数値積分は分布に応じ、台形近似法やシンプソン法を用いる。この計算によって得られるのは画像左端の位置ずれを0としているが、位置ずれの基準を変更は基準とする位置のずれ量Δだけ全体の位置移動量を引くとことで修正できる。
計測点における位置ずれ量を算出したが、位置ずれ量の補正対象は計測点以外にもあり、画像内の任意の点における位置ずれ量は、周囲の計測点の結果から外挿または内挿する。次にその例を示す。図48に示すように、計測点のX方向ピッチをXp(Pixel)、Y方向ピッチをYp(Pixel)で配置し、その4点のエッジ点左下にある計測点を原点とした時の、位置(x,y)の位置ずれ量の算出方法の例を示す。計測点A4801,B4802,C4803,D4804それぞれの位置ずれ量をa,b,c,dとする。このとき、位置(x,y)の位置ずれ量Δは以下の式で内挿する。
この式では下記の各点のΔは以下の様になる。
(x,y)=(Xp,0)では Δ=b
(x,y)=(0,Yp)では Δ=c
(x,y)=(Xp/2,0)では Δ=(a+b)/2
(x,y)=(0,Yp/2)では Δ=(a+c)/2
(x,y)=(Xp/2,Yp)では Δ=(c+d)/2
(x,y)=(Xp,Yp/2)では Δ=(b+d)/2
(x,y)=(Xp/2,Yp/2) では
Δ=(a+b+c+d)/4
視野をずらして取得した2枚画像から、画像歪みによる位置ずれ量を算出するフローチャートを図49に示す。またこのフローチャートの各ステップで、得られる結果を図50に示す。
図51に歪みの有無によるパターンの変形の例を示す。画像歪みが無い場合は画像の位置ずれベクトルの分布は5101のようにすべての計測点でベクトルが0となり、5101の条件で撮像されたL/Sパターン5102も、試料の形状に対し、歪み無いパターンとなる。本発明によって得られる画像歪みによる位置ずれベクトル分布の例5103と、5103の画像歪みを持つ条件で5102と同じL/Sパターンを撮像した例を5104に示す。画像歪みにより、5104は試料の形状に対し歪みを持っているが、歪みのない5102から5104への移動量は、5103の位置ずれベクトルから算出することができ、5103と5104を用いて、5102で得られる情報を算出することができる。
2つ目の方法としては、歪み率ベクトルおよび歪みによる位置ずれベクトルによる電子線走査型顕微鏡のハードへの補正である。
3つ目の方法としてはパターンの寸法を計測するために取得した画像に対し、画像歪みによる位置ずれ量をフィードバックする画像処理を行う方法である。図55に示すように、画像歪みによりひずんだ画像5501に対し、画像歪みベクトル5103をフィードバックする画像補正をソフトで実施することにより、歪みの無い画像5502を得ることができる。
画像歪みの変化が大きく、これまで説明した画像歪みベクトルを用いた画像処理による補正では画像が補正しきれない例を図56に示す。画像歪みが無い場合5102となるL/Sパターンは画像歪みにより5601のような画像歪みによる形状変化している場合、特に画像歪みの変化が大きい5602は、画像処理により修正された画像5603において5604のように歪みによる形状変化が残る場合がある。これは本発明で検出する歪み率の値が、取得した2画像間の視野をずらした2点間の歪みの平均値となっていることが主要因である。シミュレーションでの評価では視野ずらしの距離を画像サイズの1/9とした時、画像サイズの1/6の波長を持つ歪みに対する感度は50%となる。このように画像歪みの変化が大きい場合は、画像歪みベクトルを用いた画像処理による補正を、視野をずらした2画像に対して行い、再度が像歪みベクトルを算出することで精度を上げることができる。
次に計測した歪みデータの保存方法の例を図61に示す。歪みは画像取得条件、例えば電子線の加速電圧(Vacc)、電子線の電流値(Ip),倍率(Mag),画像の回転角度(Rot)に対する依存性を持つ。そのため、画像内の歪み率分布および歪みによる位置ずれ量の分布のデータだけでなく、歪みデータを算出する画像の取得条件も保存する必要がある。したがって各データのNO.(またはデータ名称)の他に画像の取得条件6101~6104も一覧として表示する。
電子走査型顕微鏡でのパターンの自動計測の例を図62に示す。ここでは3本の縦ライン6201~6203のライン幅を計測するために、自動計測パラメータ6206を設定し、画像内のラインパターンに合わせて6204に示すカーソルを設定する。自動計測パラメータ6206にはカーソルのサイズ(形状),エッジ検出条件,測定するライン本数等の条件6207を設定する。6204がライン一箇所に対してのカーソルの場合でも、測定するライン本数を3と設定すれば、画像から3本のラインを検出し計測する。このカーソルは手動で配置してもよいし、計測レシピの画像認識でラインの中心を検出しカーソル位置を決定するように設定してもよい。
計測した画像の歪みによる位置ずれ量分布の表示方法の例を示す。まず計測点6401に位置ずれベクトル6402を表示する方法である。ベクトルの始点は計測点6401と一致しており、ひずんだ画像での計測点である。ベクトルの終点は画像歪みにより位置ずれした位置である。したがって、計測点6401で検出したエッジ点を補正するためには、位置ずれベクトルと同じ長さで逆向きの方向にずらす。ベクトルサイズに応じて色分けや太さを変えるなどして表示し、ベクトルサイズで区別することも可能である。また、区別の基準としては、ベクトルのX成分またはY成分とすることも可能である。
(1)Si基板を加工したパターンであるので、半導体装置への重金属混入の恐れはなく、電子線を照射しても試料は帯電しない。試料は電子線を照射しても帯電しないので、取得した画像に試料帯電による歪みも生じず、正確な測定が可能である。
(2)前記試料に形成された不規則パターンは、図66(b)に示すようにパターンの上面6604に平坦な面を持ち、パターンの高さ6606が揃っている。従って、高さばらつきによって生じるエッジシャープネスの測定ばらつきが無く、高精度、且つ、安定して電子顕微鏡を調整できる。
造方法を提供することができる。
視野を移動した画像を取得したら、重複視野内の指定箇所のパターンの移動量を測定し、画像歪みの測定を行う(ステップS8107)。このとき、パターンの移動量の測定は、例えば、パターンマッチング法を用いることができる。パターンマッチング法は、画像A内における指定箇所近傍の画像領域A´を切り出して、パターンマッチング用のテンプレートを作成し、画像B内を探索してテンプレートと類似度の高い画像の位置を測定することで、パターンの移動量を測定できる。
なお、実施例においては走査型電子顕微鏡を例に説明したが、荷電粒子線を用いた装置全般に適用することができる。
704 条件設定装置
705 シミュレーター
706 記憶媒体
710 制御装置
801 電子源
802 引出電極
803 電子ビーム
804 コンデンサレンズ
805 走査偏向器
806 対物レンズ
807 試料室
808 試料台
809 試料
810 電子
811 二次電子
812 変換電極
813 検出器
Claims (32)
- 撮像対象の第1の領域を撮像した第1の画像について、前記撮像対象の特定領域に相当する第1の部分を切り出してパターンマッチング用のテンプレートを作成するテンプレート設定部と、当該テンプレート設定部にて作成されたテンプレートを用いてマッチング処理を実行するマッチング実行部を備えた画像処理装置において、前記第1の領域とその位置が異なると共に、その一部が重畳する撮像対象の第2の領域を撮像した第2の画像内の前記第1の画像の前記第1の部分に相当する測定点と、当該第2の画像内の前記特定領域に相当する第2の部分との間の距離を演算する演算部を備え、当該演算部は、前記測定点と前記第2の部分との間の距離を、前記重畳領域の複数の部位について求めることを特徴とする画像処理装置。
- 請求項1において、
前記第1の領域の大きさと、前記第2の領域の大きさは同じであることを特徴とする画像処理装置。 - 請求項1において、
前記演算部は、所定の基準位置における前記測定点と前記第2の部分との間の距離と、複数の移動量評価位置における前記測定点と前記第2の部分との間の距離を求めることを特徴とする画像処理装置。 - 請求項3において、
前記演算部は、所定の基準位置における前記測定点と前記第2の部分間の距離と、前記移動量評価位置における前記測定点と前記第2の部分間の距離との差、或いは比を求めることを特徴とする画像処理装置。 - 請求項3において、
前記第1の画像の基準位置、及び移動量評価位置の画像を切り出して、前記テンプレートとすることを特徴とする画像処理装置。 - 請求項5において、
前記演算部は、前記テンプレートによるテンプレートマッチングに基づいて、前記基準位置における前記測定点と前記第2の部分との距離と、複数の移動量評価位置における前記測定点と前記第2の部分との距離を求めることを特徴とする画像処理装置。 - 請求項1において、
前記画像処理装置は、走査幅が校正された装置条件に基づいて、前記第1の画像、及び前記第2の画像を取得することを特徴とする画像処理装置。 - 荷電粒子源と、当該荷電粒子源から放出されたビームの照射位置を移動する視野移動用の偏向器を備えた荷電粒子線装置において、
試料上の特定領域を第1の部分とする第1の領域の第1の画像と、当該第1の領域とは異なる位置であって、その一部が重畳する第2の領域の第2の画像を取得するための装置条件を設定する装置条件設定部と、
前記第2の画像内の前記第1の画像の第1の部分に相当する測定点と、当該第2の画像内の前記特定領域に相当する第2の部分との間の距離を演算する演算部を備え、当該移動量演算部は、前記測定点と前記第2の部分との間の距離を、前記重畳領域の複数の部位について求めることを特徴とする荷電粒子線装置。 - 請求項8において、
前記第1の領域の大きさと、前記第2の領域の大きさは同じであることを特徴とする荷電粒子線装置。 - 請求項8において、
前記演算部は、所定の基準位置における前記測定点と前記第2の部分との間の距離と、複数の移動量評価位置における前記測定点と前記第2の部分との間の距離を求めることを特徴とする荷電粒子線装置。 - 請求項10において、
前記演算部は、所定の基準位置における前記測定点と前記第2の部分間の距離と、前記移動量評価位置における前記測定点と前記第2の部分間の距離との差、或いは比を求めることを特徴とする荷電粒子線装置。 - 請求項10において、
前記装置条件設定部は、前記基準位置に基準パターンを位置づけたときに得られる画像に基づいて、前記ビームの走査幅を校正し、当該校正後の装置条件に基づいて、前記第1の画像、及び前記第2の画像を取得するための装置条件を設定することを特徴とする荷電粒子線装置。 - 請求項8において、
前記試料を載置するための試料台を備えたことを特徴とする荷電粒子線装置。 - 請求項8において、
前記試料を試料室外に配置すると共に、前記第1の画像と前記第2の画像の取得の際に、試料室に当該試料を搬入することを特徴とする荷電粒子線装置。 - 撮像した画像、及び当該撮像した画像内でパターンマッチングを行うためのテンプレートを記憶する記憶媒体にアクセス可能、或いは当該記憶媒体を内蔵するコンピュータに、撮像対象の第1の領域を撮像した第1の画像について、前記撮像対象の特定領域に相当する第1の部分を切り出してパターンマッチング用のテンプレートを作成させ、当該作成されたテンプレートを用いてマッチング処理を実行させるコンピュータプログラムにおいて、
当該プログラムは前記コンピュータに、前記第1の領域とその位置が異なると共に、その一部が重畳する撮像対象の第2の領域を撮像した第2の画像内の前記第1の画像の第1の部分に相当する測定点と、当該第2の画像内の前記特定領域に相当する第2の部分との間の距離を演算させると共に、前記測定点と前記第2の部分との間の距離を、前記重畳領域の複数の部位について求めさせることを特徴とするコンピュータプログラム。 - 荷電粒子線装置によって取得された画像の歪みを測定する画像処理装置において、
前記画像内の異なる複数の個所の歪みを計測する画像歪み量演算部を備えたことを特徴とする画像処理装置。 - 請求項16において、
前記画像の基準位置および複数の移動評価位置における移動量から、撮像された画像の歪みによる位置ずれまたは位置ずれ分布を計測することを特徴とする画像処理装置。 - 請求項16において、
前記計測された画像の位置ずれおよび位置ずれ分布より、取得画像の位置ずれ補正、または取得画像から検出されたパターン寸法補正および輪郭線補正を行うことを特徴とする画像処理装置。 - 請求項16において、前記計測された画像内の異なる複数の個所の歪みの分布を表示させる表示装置を備えたことを特徴とする画像処理装置。
- 基板と、
前記基板表面に形成され、半導体材料からなる凹凸パターンとを有し、
前記凹凸パターンは、二次元方向に不規則なパターンであり、
前記凹凸パターンの凸部上面は、高さの揃った平坦面であることを特徴とする荷電粒子線装置調整用試料。 - 請求項20記載の荷電粒子線装置調整用試料であって、
前記半導体材料は、Siであることを特徴とする荷電粒子線装置調整用試料。 - 請求項20記載の荷電粒子線装置調整用試料であって、
前記不規則な凹凸パターンは、3nm~200nmの範囲の寸法を含むことを特徴とする荷電粒子線装置調整用試料。 - 請求項20記載の荷電粒子線装置調整用試料であって、
前記基板はSi基板であり、
前記凹凸パターンの凸部上面の平坦面は、前記凹凸パターン形成前の前記Si基板の最表面で構成されることを特徴とする荷電粒子線装置調整用試料。 - 請求項20記載の荷電粒子線装置調整用試料であって、
前記凹凸パターンに荷電粒子線を照射して得られる荷電粒子線装置画像の画像階調のヒストグラムにおいて、前記凹凸パターンの凸部からの信号ピークの階調ばらつきが前記凹凸パターンの凹部からの信号ピークの階調ばらつきの2倍以下であることを特徴とする荷電粒子線装置調整用試料。 - 請求項20記載の荷電粒子線装置調整用試料であって、
前記高さが揃った平坦面とは、高さのばらつきが10nm以下の場合を含むことを特徴とする荷電粒子線装置調整用試料。 - パターニングしていない厚さ10nm~0.1nmの範囲の膜厚で均一なSi酸化膜をSi基板上に形成する工程と、
プラズマ式ドライエッチング装置を用い、Si酸化膜に対する選択比が高い条件にて前記Si基板に微細パターンを形成する工程とを含み、
前記ドライエッチング前のSi基板の最表面は、前記微細パターン上面の平坦面を構成することを特徴とする荷電粒子線装置調整用試料の製造方法。 - 請求項26記載の荷電粒子線装置調整用試料の製造方法であって、
前記微細パターンを形成する工程において、前記プラズマ式ドライエッチング装置に少なくともCl2、および、O2ガスを含む混合ガスを導入することを特徴とする荷電粒子線装置調整用試料の製造方法。 - 請求項20記載の荷電粒子線装置調整用試料を用いて、焦点、非点、画像分解能、エッジシャープネス、画像倍率、画像歪みの少なくとも一つを測定し、前記測定した値が予め設定した値の範囲に入るように調整したことを特徴とする荷電粒子線装置。
- 請求項20記載の荷電粒子線装置調整用試料を用いて、複数の荷電粒子線装置における画像分解能、エッジシャープネス、画像倍率、または、画像歪みの少なくとも一つを測定し、前記複数の荷電粒子線装置において、測定した結果が予め設定した値の範囲に入るように調整したことを特徴とする荷電粒子線装置。
- 請求項20記載の荷電粒子線装置調整用試料を用いて、荷電粒子線装置の画像分解能、エッジシャープネス、画像倍率、または、画像歪みの少なくとも一つを測定し、前記測定値に基づいて、前記荷電粒子線装置を用いて測定した画像または前記画像を処理して得たデータを補正する機能を備えたことを特徴とする荷電粒子線装置。
- 請求項20記載の荷電粒子線装置調整用試料であって、
前記凹凸パターンの凸部の側壁は垂直形状を有することを特徴とする荷電粒子線装置調整用試料。 - 請求項20記載の荷電粒子線装置調整用試料であって、
前記凹凸パターンの表面は帯電しないような薄いSi酸化膜で覆われていることを特徴とする荷電粒子線装置調整用試料。
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