CN115950859B - Method and system for judging resolution limit of reflection spectrum according to film thickness detection resolution - Google Patents
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Abstract
The invention relates to a method and a system for judging resolution limit of a reflection spectrum according to film thickness detection resolution, wherein the method comprises the following steps: acquiring the reflectivity of the thickness of the measured film at the corresponding wavelength, and establishing a corresponding relation between the wavelength in the set wavelength range and the reflectivity to obtain a first reflectivity curve in the wavelength range; setting the film thickness change amount of the detected film as film thickness detection resolution, obtaining the reflectivity of the film thickness of the detected film after the film thickness detection resolution is increased or decreased under the corresponding wavelength, and establishing the corresponding relation between the wavelength and the reflectivity in the set wavelength range to obtain a second reflectivity curve in the wavelength range; and obtaining the difference value of the reflectivity of each wavelength between the first reflectivity curve and the second reflectivity curve, and processing the difference value to be used as the resolution limit of the reflection spectrum. The invention can reduce the time of selecting the film, and ensure that the spectrometer distinguishes the film thickness data with the resolution above the film thickness detection limit; can be applied in the field of electric digital data processing.
Description
Technical Field
The invention relates to the technical field of electric digital data processing, in particular to a method and a system for judging a resolution limit of a reflection spectrum according to a film thickness detection resolution.
Background
With the rapid development of the semiconductor industry, the feature size of integrated circuits is continuously miniaturized, and the semiconductor wafer is continuously developed towards the small volume, high circuit density, rapidity and low power consumption, so that integrated circuits are now brought into the submicron-scale technology stage of ULSI. With the gradual increase of the diameter of the silicon wafer, the width of the scribing lines in the element is gradually reduced, and the number of metal layers is increased, so that the high polishing of the surface of the semiconductor film has important influence on the high performance, low cost and high yield of the device, and the surface flatness requirement of the silicon wafer is becoming stricter.
In the CMP process, if there is no effective endpoint detection (End Point Detection, EPD) technology, excessive material removal or insufficient material removal on the wafer surface layer easily occurs, so how to determine whether the CMP process reaches the desired endpoint is a difficult point to be solved in the CMP process, and has important significance for effectively solving the over-polishing or under-polishing problem. Particularly in the field of nanotechnology, endpoint detection is particularly important. Endpoint detection includes both off-line and on-line. The off-line endpoint detection is to determine the polishing endpoint by controlling the polishing time in combination with a predetermined removal amount, which has the disadvantage that the problem of excessive material removal or insufficient material removal on the surface layer of the wafer cannot be effectively avoided, and the off-line endpoint detection is mainly applied to processing wafers with diameters lower than 200mm at present, and cannot meet the current requirement of automatic processing of large-diameter silicon wafers. The current mainstream technology is online endpoint detection, which can better control the thickness variation of the wafer film, reduce repeated operation, and realize the automatic operation of CMP, thereby improving the utilization rate and yield of polishing equipment, reducing the density distribution defect of IC equipment, reducing the non-uniformity, and finally improving the stability and reliability of semiconductor equipment. The principle of the online end point detection technology is mainly based on detection of optical, electrical, acoustic or vibration, thermal, friction, chemical or electrochemical principles, and is realized by detecting changes of parameters such as current changes of a driving motor, acoustic emission signals, temperature of a polishing pad, ion concentration in polishing solution and the like.
Among the above-mentioned means of endpoint detection, the reaction of film thickness by reflectance is one of the most commonly used techniques, wherein the type of spectrometer is also closely related to the accuracy of reflectance, different levels and values of spectrometer correspond to different resolution sensitivities, different resolution sensitivities have different resolution capabilities, and a user needs to make a selection of the spectrometer sensitivity according to the film thickness detection limit required at the time of film thickness measurement. How to obtain the relationship between the two limits is a technical problem to be solved.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a method and a system for determining a resolution limit of a reflection spectrum according to a resolution of film thickness detection, which can reduce a time for selecting a pattern, and ensure that a spectrometer distinguishes film thickness data with a resolution above the film thickness detection limit.
In order to achieve the above object, according to a first aspect, the present invention adopts the following technical scheme: a method of determining a resolution limit of a reflectance spectrum based on a film thickness detection resolution, comprising: acquiring the reflectivity of the thickness of the measured film at the corresponding wavelength, and establishing a corresponding relation between the wavelength in the set wavelength range and the reflectivity to obtain a first reflectivity curve in the wavelength range; setting the film thickness change amount of the detected film as film thickness detection resolution, obtaining the reflectivity of the film thickness of the detected film after the film thickness detection resolution is increased or decreased under the corresponding wavelength, and establishing the corresponding relation between the wavelength and the reflectivity in the set wavelength range to obtain a second reflectivity curve in the wavelength range; and obtaining the difference value of the reflectivity of each wavelength between the first reflectivity curve and the second reflectivity curve, and processing the difference value to be used as the resolution limit of the reflection spectrum.
Further, the obtaining the reflectivity of the current thickness of the measured film under the corresponding wavelength includes: and calculating the reflectivity of the current thickness at the corresponding wavelength lambda according to the measured film thickness D, the air refractive index, the refractive index of the measured film and the refractive index of the substrate material.
Further, the reflectivity is:
R=r×r*=
wherein R is reflectivity;
r is the conjugate of r; r is (r) 1 And r 2 The refractive index coefficients at two interfaces formed by three refractive index mediums are the refractive index of air, the refractive index of a measured film when different wavelengths are incident and the refractive index of a substrate material when different wavelengths are incident; delta is the phase thickness of the film and lambda is the wavelength.
Further, the set wavelength range is: 210nm-500nm.
Further, the processing the difference value as the resolution limit of the reflection spectrum includes: and carrying out minimum value processing or average value processing on the difference value.
Further, the average value serves as a reflectance spectrum resolution limit.
In a second aspect, the present invention adopts the following technical scheme: a system for determining a resolution limit of a reflectance spectrum based on a film thickness detection resolution, comprising: the first processing module is used for obtaining the reflectivity of the thickness of the measured film at the corresponding wavelength, establishing the corresponding relation between the wavelength in the set wavelength range and the reflectivity, and obtaining a first reflectivity curve in the wavelength range; the second processing module is used for setting the film thickness change amount of the detected film as the film thickness detection resolution, obtaining the reflectivity of the film thickness of the detected film after the film thickness detection resolution is increased or reduced under the corresponding wavelength, and establishing the corresponding relation between the wavelength and the reflectivity in the set wavelength range to obtain a second reflectivity curve in the wavelength range; the selection module is used for obtaining the difference value of the reflectivity of each wavelength between the first reflectivity curve and the second reflectivity curve, and processing the difference value to be used as the resolution limit of the reflection spectrum.
Further, in the selecting module, obtaining the reflectivity of the current thickness of the measured film under the corresponding wavelength includes: and calculating the reflectivity of the current thickness at the corresponding wavelength lambda according to the measured film thickness D, the air refractive index, the refractive index of the measured film and the refractive index of the substrate material.
In a third aspect, the present invention adopts the following technical scheme: a computer readable storage medium storing one or more programs, the one or more programs comprising instructions, which when executed by a computing device, cause the computing device to perform any of the methods described above.
In a fourth aspect, the present invention adopts the following technical scheme: a computing apparatus, comprising: one or more processors, memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs comprising instructions for performing any of the methods described above.
Due to the adoption of the technical scheme, the invention has the following advantages:
1. according to the invention, experiments are not needed, the required model selection of the spectrometer can be obtained only through the corresponding relation, a theoretical basis is provided for reasonable selection of the spectrometer, the model selection time is shortened, and at the same time, the spectrometer can be ensured to at least distinguish film thickness data with resolution above the film thickness detection limit.
2. The method is also suitable for a measuring environment with constant relative error, and can ensure that the thickness of the thin film with the film thickness difference being the film thickness detection limit can be distinguished under the error condition.
Drawings
FIG. 1 is a flowchart of a method for determining a resolution limit of a reflection spectrum according to a film thickness detection resolution in an embodiment of the present invention;
FIG. 2 is a graph showing the reflectance curve at a fixed wavelength range after setting the film thickness detection resolution according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which are obtained by a person skilled in the art based on the described embodiments of the invention, fall within the scope of protection of the invention.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
In an embodiment of the present invention, a method for determining a resolution limit of a reflection spectrum according to a film thickness detection resolution is provided. In this embodiment, as shown in fig. 1, the method includes the following steps:
1) Acquiring the reflectivity of the thickness of the measured film at the corresponding wavelength, and establishing a corresponding relation between the wavelength in the set wavelength range and the reflectivity to obtain a first reflectivity curve in the wavelength range;
2) Setting the film thickness change amount of the detected film as film thickness detection resolution, obtaining the reflectivity of the film thickness of the detected film after the film thickness detection resolution is increased or decreased under the corresponding wavelength, and establishing the corresponding relation between the wavelength and the reflectivity in the set wavelength range to obtain a second reflectivity curve in the wavelength range;
3) And obtaining the difference value of the reflectivity of each wavelength between the first reflectivity curve and the second reflectivity curve, and processing the difference value to be used as the resolution limit of the reflection spectrum.
When the film thickness measuring device is used, the film thickness change amount is used as film thickness detection resolution, corresponding reflectivity curves are obtained through measuring different film thicknesses, the reflectivity resolution capability is fully utilized, the type selection of a spectrometer is realized, and the film thickness measuring precision is ensured to the minimum.
In the step 1), the reflectivity of the current thickness of the measured film at the corresponding wavelength is obtained, specifically: and calculating the reflectivity of the current thickness at the corresponding wavelength lambda according to the thickness D of the measured film thickness, the air refractive index, the refractive index of the measured film and the refractive index of the substrate material.
Wherein, the reflectivity R of the measured film is:
R=r×r*=
wherein,,
r is the conjugate of r; r is (r) 1 And r 2 The refractive index coefficients at two interfaces formed by three refractive index mediums are the refractive index of air, the refractive index of a measured film when different wavelengths are incident and the refractive index of a substrate material when different wavelengths are incident; />
r 1 =-(n 2 -n 1 )/(n 2 +n 1 )，
r 2 =-(n 3 -n 2 )/(n 3 +n 2 )，
n 3 =n+iK，
δ=4πDn 2 /λ，
Delta is the phase thickness of the film, n 1 Is air refractive index, n 2 For the refractive index of the measured film when incident at different wavelengths, n 3 The refractive index of the substrate material when different wavelengths are incident, lambda is the wavelength, n is the real part of the refractive index of the substrate material when different wavelengths are incident, and K is the extinction coefficient of the substrate material.
In the present embodiment, it is preferable that the set wavelength range is: 210nm-500nm.
In the step 2), the film thickness measurement resolution value after thinning or thickening, the air refractive index, the refractive index of the measured film and the refractive index of the substrate material are calculated according to the data, the reflectivity of the current thickness under the corresponding wavelength is calculated, the corresponding relation between the wavelength of the wavelength range selected under 210nm-500nm and the reflectivity is established, and a second reflectivity curve in the wavelength range is obtained.
In the step 3), the difference value is processed to be used as a resolution limit of the reflection spectrum, specifically: and carrying out minimum value taking treatment or average value taking treatment on the difference value to obtain the minimum value or average value of the difference value.
In the present embodiment, it is preferable that an average value of the reflectance differences at each wavelength between the first reflectance curve and the second reflectance curve is used as a limit of the reflectance spectrum resolution.
Examples: by Air-SiO 2 For example, the Si structure, the film to be measured is SiO 2 The number of oscillation items is determined by the film thickness according to the oscillation characteristics of the spectrum, and when the film thickness is changed from small to large, the oscillation items appear from short waves and then gradually increase, and the oscillation density of short wave bands is larger than that of long wave bands, so that the spectrum information of the short wave bands is longer, the film thickness is easier to distinguish, and the wave bands of 210-500nm are selected in the embodiment. The thickness of the wave film was 300nm.
First, the reflectance coefficient r at two interfaces formed by three refractive index media is calculated 1 And r 2 Wherein, the wavelength is 250nm, n at the moment 1 =1，n 2 =1.51，n 3 =1.58+3.63i. At this time, the liquid crystal display device,
according to the refractive index n of the film to be measured 2 The phase difference delta is obtained from the film thickness D,
δ=4πDn 2 /λ
substituting the reflection coefficient calculation formula into the formula,
then multiplying the reflectance by the reflectance R to obtain the reflectance R at a fixed film thickness:
R=r×r*=
=0.44
after extending the wavelength range to 210nm-500nm, a reflectance curve at this wavelength range was obtained.
After the film thickness detection resolution is set to 2nm, a new reflectance curve in the same wavelength range is calculated and drawn by the same method according to the above method, and the specific calculation method is not described here. As shown in FIG. 2, is SiO 2 Two reflectance curves with a film thickness difference of 2nm, wherein the broken line is a reflectance curve at a wavelength of 302nm and the solid line is a reflectance curve at a wavelength of 300nm.
By calculating the minimum value of the difference in reflectivity at each wavelength between the two reflectivity curves (1.2 x 10 -4 ）&Average value (9.5 x 10) -3 ) The resolution limit of the spectrometer at this film thickness was obtained. The reflectance curves with the film thickness difference being the detection limit under different film thicknesses (200/300/400 nm) are compared, and the minimum values of the reflectance differences under different wavelengths are found to be different and are basically 10 -4 The magnitude is even smaller but the average difference in reflectance is similar, about 1 x 10 -2 。
The calculated average value of the reflectance differences is taken as the resolution limit of the required spectrometer. After determining the film thickness detection resolution to be 2nm, the minimum resolution limit of the required spectrometer is calculated to be larger than 1×10 -2 . The average difference of the reflectances is used as a selection standard, so that the film thickness measurement accuracy is ensured to the minimum, and the method has important guiding significance on the selection of the parameters of the spectrometer.
In one embodiment of the present invention, there is provided a system for judging a resolution limit of a reflection spectrum according to a film thickness detection resolution, including:
the first processing module is used for obtaining the reflectivity of the thickness of the measured film at the corresponding wavelength, establishing the corresponding relation between the wavelength in the set wavelength range and the reflectivity, and obtaining a first reflectivity curve in the wavelength range;
the second processing module is used for setting the film thickness change amount of the detected film as the film thickness detection resolution, obtaining the reflectivity of the film thickness of the detected film after the film thickness detection resolution is increased or reduced under the corresponding wavelength, and establishing the corresponding relation between the wavelength and the reflectivity in the set wavelength range to obtain a second reflectivity curve in the wavelength range;
and the selection module is used for obtaining the difference value of the reflectivity of each wavelength between the first reflectivity curve and the second reflectivity curve, processing the difference value to be used as a resolution limit of a reflection spectrum, and completing the model selection of the spectrometer.
In the above embodiment, obtaining the reflectivity of the current thickness of the measured film at the corresponding wavelength includes:
and calculating the reflectivity of the current thickness at the corresponding wavelength lambda according to the thickness D of the measured film thickness, the air refractive index, the refractive index of the measured film and the refractive index of the substrate material.
Wherein, the reflectivity is:
R=r×r*=
wherein R is reflectivity;
r is the conjugate of r; r is (r) 1 And r 2 The refractive index coefficients at two interfaces formed by three refractive index mediums are the refractive index of air, the refractive index of a measured film when different wavelengths are incident and the refractive index of a substrate material when different wavelengths are incident; delta is the phase thickness of the film and lambda is the wavelength.
In the present embodiment, it is preferable that the set wavelength range is: 210nm-500nm.
In the above embodiment, the difference is processed as the reflectance spectrum resolution limit: and carrying out minimum value processing or average value processing on the difference value.
In the present embodiment, it is preferable that the average value is taken as the reflectance spectrum resolution limit.
The system provided in this embodiment is used to execute the above method embodiments, and specific flow and details refer to the above embodiments, which are not described herein.
In one embodiment of the invention, a computing device structure is provided, which may be a terminal, and may include: a processor (processor), a communication interface (Communications Interface), a memory (memory), a display screen, and an input device. The processor, the communication interface and the memory complete communication with each other through a communication bus. The processor is configured to provide computing and control capabilities. The memory comprises a nonvolatile storage medium and an internal memory, wherein the nonvolatile storage medium stores an operating system and a computer program, and the computer program is executed by a processor to realize a method for judging the resolution limit of a reflection spectrum according to the film thickness detection resolution; the internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The communication interface is used for carrying out wired or wireless communication with an external terminal, and the wireless mode can be realized through WIFI, a manager network, NFC (near field communication) or other technologies. The display screen can be a liquid crystal display screen or an electronic ink display screen, the input device can be a touch layer covered on the display screen, can also be a key, a track ball or a touch pad arranged on the shell of the computing equipment, and can also be an external keyboard, a touch pad or a mouse and the like. The processor may invoke logic instructions in memory.
Further, the logic instructions in the memory described above may be implemented in the form of software functional units and stored in a computer-readable storage medium when sold or used as a stand-alone product. Based on this understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) to perform all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
In one embodiment of the present invention, a computer program product is provided, the computer program product comprising a computer program stored on a non-transitory computer readable storage medium, the computer program comprising program instructions which, when executed by a computer, are capable of performing the methods provided by the method embodiments described above.
In one embodiment of the present invention, a non-transitory computer readable storage medium storing server instructions that cause a computer to perform the methods provided by the above embodiments is provided.
The foregoing embodiment provides a computer readable storage medium, which has similar principles and technical effects to those of the foregoing method embodiment, and will not be described herein.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (9)
1. A method for determining a resolution limit of a reflection spectrum based on a film thickness detection resolution, comprising:
acquiring the reflectivity of the thickness of the measured film at the corresponding wavelength, and establishing a corresponding relation between the wavelength in the set wavelength range and the reflectivity to obtain a first reflectivity curve in the wavelength range;
setting the film thickness change amount of the detected film as film thickness detection resolution, obtaining the reflectivity of the film thickness of the detected film after the film thickness detection resolution is increased or decreased under the corresponding wavelength, and establishing the corresponding relation between the wavelength and the reflectivity in the set wavelength range to obtain a second reflectivity curve in the wavelength range;
obtaining the difference value of the reflectivity of each wavelength between the first reflectivity curve and the second reflectivity curve, and processing the difference value to be used as a resolution limit of a reflection spectrum;
the set wavelength range is as follows: 210nm-500nm.
2. The method for determining resolution limit of reflection spectrum according to resolution of film thickness detection as claimed in claim 1, wherein said obtaining reflectivity of the current thickness of the film under test at the corresponding wavelength comprises:
and calculating the reflectivity of the current thickness at the corresponding wavelength lambda according to the measured film thickness D, the air refractive index, the refractive index of the measured film and the refractive index of the substrate material.
3. The method for determining resolution limit of reflection spectrum according to resolution of film thickness detection as claimed in claim 2, wherein the reflectance is:
R=r×r*=
，
wherein R is reflectivity; r= (r) 1 2 +r 2 2 +2r 1 r 2 cos2δ)/(1+r 1 2 r 2 2 +2r 1 r 2 cos2 δ), r is the conjugate of r; r is (r) 1 And r 2 The refractive index coefficients at two interfaces formed by three refractive index mediums are the refractive index of air, the refractive index of a measured film when different wavelengths are incident and the refractive index of a substrate material when different wavelengths are incident; delta is the phase thickness of the film and lambda is the wavelength.
4. The method for determining a resolution limit of a reflectance spectrum according to a film thickness detection resolution as claimed in claim 1, wherein said processing the difference as the resolution limit of the reflectance spectrum comprises: and carrying out minimum value processing or average value processing on the difference value.
5. The method for determining a resolution limit of a reflectance spectrum according to a film thickness detection resolution as recited in claim 4, wherein said average value is used as the resolution limit of the reflectance spectrum.
6. A system for determining a resolution limit of a reflection spectrum based on a film thickness detection resolution, comprising:
the first processing module is used for obtaining the reflectivity of the thickness of the measured film at the corresponding wavelength, establishing the corresponding relation between the wavelength in the set wavelength range and the reflectivity, and obtaining a first reflectivity curve in the wavelength range;
the second processing module is used for setting the film thickness change amount of the detected film as the film thickness detection resolution, obtaining the reflectivity of the film thickness of the detected film after the film thickness detection resolution is increased or reduced under the corresponding wavelength, and establishing the corresponding relation between the wavelength and the reflectivity in the set wavelength range to obtain a second reflectivity curve in the wavelength range;
the selection module is used for obtaining the difference value of the reflectivity of each wavelength between the first reflectivity curve and the second reflectivity curve, and processing the difference value to be used as a resolution limit of a reflection spectrum;
the set wavelength range is as follows: 210nm-500nm.
7. The system for determining resolution limit of reflection spectrum according to resolution of film thickness as claimed in claim 6, wherein said selecting module obtains reflectivity of a current thickness of the film under test at a corresponding wavelength, comprising:
and calculating the reflectivity of the current thickness at the corresponding wavelength lambda according to the measured film thickness D, the air refractive index, the refractive index of the measured film and the refractive index of the substrate material.
8. A computer readable storage medium storing one or more programs, wherein the one or more programs comprise instructions, which when executed by a computing device, cause the computing device to perform any of the methods of claims 1-5.
9. A computing device, comprising: one or more processors, memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs comprising instructions for performing any of the methods of claims 1-5.
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