WO2017122248A1 - Method for measuring film thickness distribution of wafer with thin film - Google Patents

Method for measuring film thickness distribution of wafer with thin film Download PDF

Info

Publication number
WO2017122248A1
WO2017122248A1 PCT/JP2016/005126 JP2016005126W WO2017122248A1 WO 2017122248 A1 WO2017122248 A1 WO 2017122248A1 JP 2016005126 W JP2016005126 W JP 2016005126W WO 2017122248 A1 WO2017122248 A1 WO 2017122248A1
Authority
WO
WIPO (PCT)
Prior art keywords
thin film
film thickness
wavelength
wafer
thickness distribution
Prior art date
Application number
PCT/JP2016/005126
Other languages
French (fr)
Japanese (ja)
Inventor
登 桑原
Original Assignee
信越半導体株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 信越半導体株式会社 filed Critical 信越半導体株式会社
Publication of WO2017122248A1 publication Critical patent/WO2017122248A1/en

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material

Definitions

  • the present invention relates to a method for measuring a film thickness distribution of a wafer with a thin film having a thin film on a substrate.
  • SOI wafers For the production of semiconductor devices, SOI (Silicon On Insulator) wafers are widely used.
  • a general structure of an SOI wafer is such that a buried oxide film layer (BOX layer) is formed on a silicon substrate, and an SOI layer made of a silicon single crystal is formed thereon.
  • the SOI wafer is a wafer with a thin film to which a thin film (BOX layer, SOI layer) is attached.
  • SOI device film thickness distribution and BOX layer film thickness distribution of SOI wafers used for SOI device fabrication, especially for FD-SOI (Fully Depleted SOI) device fabrication It has come to influence the transistor characteristics. In an integrated circuit, it is important to make the characteristics of the transistors constituting the circuit uniform.
  • spectroscopic ellipsometry spectral ellipsometry
  • reflection spectroscopy a spectrum in a certain wavelength range (generally, visible light region) is taken for each measurement point, and the model film structure is taken for that spectrum.
  • the film thickness at each measurement point is obtained by fitting to. Therefore, if the film thickness distribution of a thin film is measured with a spatial resolution of about 1 [ ⁇ m], the number of measurement points increases extremely, so that it cannot be practically measured due to the amount of calculation and time constraints.
  • the method for measuring the film thickness distribution of a thin film particularly a wafer with a thin film, which can easily measure the film thickness distribution of each of the SOI layer and the BOX layer of the SOI wafer with high accuracy, low cost, and the like. Is required.
  • Patent Document 1 discloses a technique for irradiating a SOI wafer with white light, dispersing reflected light for each wavelength, and calculating the SOI layer film thickness from interference information for each wavelength.
  • Patent Document 2 an SOI layer with a film thickness of less than 1 [ ⁇ m] is irradiated with a laser beam of 488 [nm], its specular reflection light is detected, and in-plane film thickness variation is caused by interference fringes with the irradiated light. The inspection is described.
  • Patent Document 3 describes a method of measuring the film thickness distribution of only the SOI layer.
  • the SOI film thickness is obtained from a reflectance or a calibration curve of data measured by an ellipso method.
  • JP 2002-343842 A Japanese Patent Laid-Open No. 08-264605 JP 2011-249621 A International Publication No. WO2014 / 072109
  • the conventional film thickness measurement method for calculating the film thickness distribution of a thin film wafer having a thin film on the surface of the substrate is generally a point-by-point film thickness measurement by spectroscopic ellipsometry or reflection spectroscopy.
  • Patent Document 3 proposes a method for increasing the measurement sensitivity in measuring only the SOI layer film thickness.
  • the film thickness distribution of the SOI layer is affected by the film thickness distribution of the BOX layer. Is difficult to measure with sufficient accuracy. Moreover, the measurement of the BOX layer was not performed.
  • the SOI film thickness is obtained from the calibration curve of the data measured by the reflectance or the ellipso method as described above, but it is influenced by the optical system when measuring the reflectance. Moreover, it is necessary to create a calibration curve of the SOI layer thickness value measured by the reflectance or the ellipso method for each combination of the thicknesses of the SOI layer and the BOX layer, which is complicated.
  • the present invention has been made in view of the above problems, and in a wafer with a thin film having a first thin film formed on a surface of a substrate and a second thin film formed on the first thin film, Measuring the film thickness distribution of at least one of the thin film and the second thin film as a film thickness distribution expressed in absolute values with high spatial resolution and without being affected by the film thickness distribution of each other.
  • An object of the present invention is to provide a method for measuring the film thickness distribution of a thin film-coated wafer.
  • the present invention provides the first thin film of a wafer with a thin film comprising a first thin film formed on the surface of the substrate and a second thin film formed on the surface of the first thin film.
  • a method for measuring the film thickness distribution of the wafer with a thin film for measuring the film thickness distribution of at least one of the second thin film A step of calculating by simulation a profile P1 indicating the wavelength dependence of the reflectance with respect to light in a wavelength region equal to or greater than the wavelength of visible light of the wafer with a thin film to be measured; Wavelength dependence of reflectance with respect to light in a wavelength region greater than or equal to visible light of a wafer with a thin film having a second thin film that is thinner or thicker than the set film thickness T2 of the second thin film of the wafer with the thin film to be measured.
  • a sub-step of calculating a profile P22 indicating the characteristics by simulation and a difference profile P32 ( P22 ⁇ P1) between the two calculated profiles P1 and P22, and when the calculated difference profile P32 becomes zero
  • Performing at least one of calculating the film thickness distribution represented by the relative value of the two thin films Using a film thickness measuring device capable of measuring an absolute value of at least one of the film thicknesses of the first thin film and the second thin film, at least one of the first thin film and the second thin film in the irradiation region Measuring the absolute value of one film thickness; Based on at least one of the absolute value of the measured film thickness, the film thickness distribution represented by the relative value of the first thin film, and the film thickness distribution represented by the relative value of the second thin film, Calculating at least one of the film thickness distribution represented by the absolute value of the first thin film in the irradiation region and the film thickness distribution represented by the absolute value of the second thin film in the irradiation region; A method for measuring the film thickness distribution of a wafer with a thin film is provided.
  • the reflected light intensity in the irradiation area is irradiated by irradiating the thin film wafer with light having a wavelength ⁇ 1 that does not vary the reflectivity from the thin film wafer.
  • the film thickness distribution represented by the relative value of the first thin film in the irradiation region can be accurately calculated without being affected by the film thickness distribution of the second thin film.
  • the reflected light intensity in the irradiated area is measured by irradiating the thin film wafer with light of wavelength ⁇ 2, which does not change the reflectivity from the thin film wafer.
  • the film thickness distribution represented by the relative value of the second thin film in the irradiation region can be accurately calculated with high spatial resolution without being affected by the film thickness distribution of the first thin film. Therefore, based on the film thickness distribution represented by these relative values and the absolute value of the film thickness measured by the film thickness measuring device, the film thickness distribution of at least one of the first thin film and the second thin film. Can be measured with high spatial resolution as a film thickness distribution represented by an absolute value and with high accuracy without being influenced by the film thickness distribution of each other. In the present invention, at least one of the film thickness distribution represented by the absolute value of the first thin film and the film thickness distribution represented by the absolute value of the second thin film can be measured.
  • the wavelength of the irradiated light is limited to at least one of ⁇ 1 and ⁇ 2, which are each a single wavelength, the calculation amount for calculating the film thickness distribution is small, and the measurement is simple, low cost, and low cost. Is possible.
  • the wafer with a thin film to be measured may be an SOI wafer
  • the first thin film may be a buried oxide film layer
  • the second thin film may be an SOI layer made of a silicon single crystal.
  • the film thickness distribution of the buried oxide film layer and the SOI layer in the irradiation region can be calculated with high accuracy.
  • At least one of the wavelength ⁇ 1 and the wavelength ⁇ 2 is a single wavelength selected from visible light wavelengths.
  • the method for measuring the film thickness distribution of the wafer with a thin film of the present invention can be carried out at low cost because it can be performed with visible light using a normal microscope optical system.
  • the size of one side of the pixel is not less than 1/2 of the wavelength ⁇ 1 or the wavelength ⁇ 2 and not more than 100 [ ⁇ m].
  • the relative film thickness distribution of the thin film of the thin film wafer can be calculated more accurately and with high spatial resolution.
  • the expressed film thickness distribution can also be calculated with high spatial resolution.
  • the irradiation area is matched with the lithography exposure site of the device manufacturing process.
  • the irradiation area in the method for measuring the film thickness distribution of the wafer with a thin film of the present invention is effectively utilized in the device manufacturing process by matching the lithography exposure site by adjusting the magnification and field of view of the microscope.
  • the film thickness distribution represented by the absolute value of the possible thin film can be calculated.
  • the irradiation region for calculating the film thickness distribution represented by the relative value of at least one of the first thin film and the second thin film, at a plurality of locations in the surface of the wafer with the thin film It is preferable to obtain a film thickness distribution expressed as an absolute value on the entire surface.
  • the measurement over the entire surface of the wafer with a thin film can be performed with high accuracy, low cost and simply.
  • the film thickness measuring apparatus is an apparatus using a spectroscopic ellipso method or a reflection spectroscopic method.
  • the apparatus uses the spectroscopic ellipso method or the reflection spectroscopic method, the absolute value of the film thickness of the thin film can be measured easily and with high accuracy.
  • the film thickness distribution represented by the absolute value of the first thin film by obtaining only the wavelength ⁇ 1 out of the wavelength ⁇ 1 and the wavelength ⁇ 2. Only can be calculated. Moreover, only the film thickness distribution represented by the absolute value of the second thin film can be calculated by obtaining only the wavelength ⁇ 2 out of the wavelengths ⁇ 1 and ⁇ 2.
  • the film thickness distribution represented by the absolute value of only one of the first thin film and the second thin film is measured according to the purpose. Can do. In this case, since the measurement of the film thickness distribution represented by the relative value can be performed with only one of ⁇ 1 and ⁇ 2, a more rapid and low-cost measurement method can be achieved.
  • the film thickness distribution of at least one of the first thin film and the second thin film is a film thickness distribution represented by an absolute value, and the influence of the film thickness distribution on each other with high spatial resolution. It is possible to measure accurately without receiving.
  • at least one of the film thickness distribution represented by the absolute value of the first thin film and the film thickness distribution represented by the absolute value of the second thin film can be measured.
  • the wavelength of the light to be irradiated is limited to at least one of ⁇ 1 and ⁇ 2 each having a single wavelength, the calculation amount for calculating the film thickness distribution is small, and the cost is low, simple and quick. Measurement is possible.
  • (B) is a graph showing the reflected light intensity distribution in a part of (A).
  • (C) is a graph which shows the film thickness distribution represented by the absolute value of the SOI layer in a part of (A).
  • (A) is a microscopic image (upper figure) of the outer peripheral part of the SOI layer surface and a diagram (lower figure) showing the reflected light intensity distribution.
  • (B) is a graph showing the reflected light intensity distribution in a part of (A).
  • (C) is a graph which shows the film thickness distribution represented by the absolute value of the BOX layer in a part of (A). It is a graph which shows the relationship between SOI film thickness and reflectance (R) which were calculated
  • FIG. 1 is a flowchart showing the steps of the method for measuring the film thickness distribution of a wafer with a thin film according to the present invention.
  • the measuring object of the method for measuring the film thickness distribution of the wafer with a thin film of the present invention is a thin film having a first thin film formed on the surface of the substrate and a second thin film formed on the surface of the first thin film. It is a wafer.
  • a buried oxide film layer BOX layer
  • SOI wafers that have been manufactured.
  • a case where the wafer with a thin film is such an SOI wafer will be described as an example.
  • the set film thickness of the buried oxide film layer set at the time of manufacturing the SOI wafer is T1 [nm]
  • the set film thickness of the SOI layer is T2 [nm].
  • either the film thickness distribution of the first thin film or the film thickness distribution of the second thin film can be measured, but both can also be measured.
  • the case where the thickness distribution of both a 1st thin film and a 2nd thin film is mainly measured is demonstrated.
  • single wavelengths ⁇ 1 and ⁇ 2 are selected in which the reflectance does not vary with respect to the film thickness variations of the SOI layer and buried oxide film layer of the SOI wafer to be measured. Then, the film thickness distribution of each of the buried oxide film layer and the SOI layer is calculated using the selected single wavelength light. In order to select the single wavelengths ⁇ 1 and ⁇ 2, the following steps are performed.
  • a profile P1 indicating the wavelength dependence of the reflectance with respect to light in a wavelength region equal to or larger than the wavelength of visible light of the SOI wafer to be measured is calculated by simulation (see A in FIG. 1).
  • the reflectance of the second thin film of the SOI wafer to be measured that is, the reflectivity for light in the wavelength region above the visible light of the SOI wafer having an SOI layer thinner or thicker than the set film thickness T2 of the SOI layer by t [nm].
  • a profile P21 indicating wavelength dependence is calculated by simulation (see B in FIG. 1).
  • the value of t is not particularly limited, but may be, for example, about 1 [nm].
  • the values of T1 and T2 are not particularly limited, in order to make the explanation easy to understand, a case where T1 is 25 [nm] and T2 is 12 [nm] will be described here as an example.
  • FIG. 3A shows a profile P1 when the set film thickness T2 of the SOI layer of the SOI wafer to be measured is 12 [nm] and the set film thickness T1 of the buried oxide film (BOX) layer is 25 [nm].
  • the profile P31 is a profile indicating the wavelength dependence of the reflectance difference between P1 and P21.
  • FIG. 3C shows a difference profile P31 between the profiles P1 and P21 shown in FIG.
  • the wavelength in this case, 615 [nm]
  • the reflectance difference becomes zero
  • each of B and C in FIG. 1 is a sub-step of the process of obtaining the wavelength ⁇ 1.
  • Profile showing the wavelength dependence of the reflectivity of the SOI wafer having a thick SOI layer that is thinner or thicker than the set film thickness T1 of the buried oxide film layer of the SOI wafer to be measured with respect to light in the wavelength region above the visible light P22 is calculated by simulation (see D in FIG. 1).
  • FIG. 3B shows the profile P1 when the set film thickness T2 of the SOI layer of the SOI wafer to be measured is 12 [nm] and the set film thickness T1 of the buried oxide film layer is 25 [nm], and the measurement object
  • the buried oxide film layer is thicker than the SOI wafer by 1 [nm], that is, from the SOI wafer having the buried oxide film layer set thickness T1 of 26 [nm] and the SOI layer set film thickness T2 of 12 [nm].
  • each of D and E in FIG. 1 is a sub-step of the process of obtaining the wavelength ⁇ 2.
  • the order of determining ⁇ 1 and ⁇ 2 is not necessarily the above order, and ⁇ 1 may be determined after ⁇ 2 is obtained first.
  • the order of the steps in FIG. 1 is A, D, E, B, C.
  • the wavelength ⁇ 1 when it is intended to calculate only the film thickness distribution represented by the absolute value of the first thin film, only the wavelength ⁇ 1 may be obtained from the wavelengths ⁇ 1 and ⁇ 2.
  • D and E step for obtaining the wavelength ⁇ 2) in FIG. 1 are not performed.
  • only the wavelength ⁇ 2 may be obtained from the wavelengths ⁇ 1 and ⁇ 2.
  • B and C step for obtaining the wavelength ⁇ 1) in FIG. 1 are not performed.
  • light having the single wavelengths ⁇ 1 and ⁇ 2 selected in advance as described above is irradiated onto a partial region on the surface of the SOI wafer whose thickness distribution is to be measured (see F in FIG. 1).
  • Reflected light is detected from the irradiated partial region (irradiation region), and the reflectance of each pixel obtained by dividing the irradiation region into a large number is measured (see G in FIG. 1).
  • the absolute value of the film thickness of the first thin film and the second thin film is measured by a device (external device) capable of measuring the absolute value of the film thickness for the region including the irradiation region for which the reflectance for each pixel is obtained (See H in FIG. 1).
  • a device capable of measuring the absolute value of the film thickness
  • an apparatus using a spectral ellipsometry method or a reflection spectroscopy method can be suitably used. If the apparatus uses a spectroscopic ellipsometry method or a reflection spectroscopy method, the absolute value of the film thickness of the thin film can be measured easily and accurately.
  • the following calculation method is used to calculate the absolute thickness distribution of the first thin film and the second thin film (see I in FIG. 1).
  • the wavelength ⁇ 2 obtained by the above-described method means a wavelength at which the reflectance of the SOI wafer does not vary even when the film thickness of the BOX layer varies. Therefore, when the wavelength ⁇ 2 is used, the thickness of the BOX layer is fixed to 25 nm, and the relationship between the SOI thickness near the design thickness of 12 nm and the reflectance (R) is obtained by simulation, FIG. 8 is obtained.
  • the change in reflectivity due to the change in thickness ( ⁇ SOI) of the SOI layer is ⁇ R
  • ⁇ R is normalized by the reflectivity R
  • ⁇ R / R is the reflectivity change rate
  • Tp T0 + ( ⁇ Rm / Rm) ⁇ C (1)
  • the absolute value of the BOX film thickness for each pixel can be obtained by using the wavelength ⁇ 1.
  • irradiation light for example, an optical microscope as shown in FIG. 2 can be used.
  • irradiation light from a light source 3 of a general optical microscope apparatus 2 equipped with a band pass filter 4 for wavelength selection is applied to a partial region of the wafer with thin film 1 for measuring the film thickness distribution. It can be carried out by irradiation.
  • the microscope reflected light image of the irradiation region of the thin film-coated wafer 1 for measuring the film thickness distribution is measured, and the obtained image is analyzed.
  • the reflected light intensity (or reflectance) for each pixel is obtained, and the first thin film and the second film measured by an apparatus (external device) capable of measuring the reflected light intensity (or reflectance) and the absolute value of the film thickness.
  • the film thickness distribution of the absolute value of each thin film in the irradiation region can be calculated.
  • the reflected light intensity distribution of the first thin film is measured at the wavelength ⁇ 1 at which the reflectance from the wafer with the thin film does not vary even if the film thickness of the second thin film varies, and the film thickness of the first thin film varies. Even if the reflected light intensity distribution of the second thin film is measured at a wavelength ⁇ 2 at which the reflectance from the wafer with the thin film does not vary even if the film thickness data from the external device is taken in, the reflected light
  • the film thickness distribution represented by the absolute value of the first thin film and / or the second thin film can be accurately calculated with micro spatial resolution.
  • the wavelength of the irradiated light is limited to at least one of ⁇ 1 and ⁇ 2, which are each a single wavelength, the calculation amount for calculating the film thickness distribution is small, and the measurement is simple, low cost, and low cost. Is possible.
  • the film thickness distribution can be calculated for each thin film by separately irradiating the light of the single wavelengths ⁇ 1 and ⁇ 2 and separately detecting the reflected light, but the single wavelengths ⁇ 1 and ⁇ 2 It is also possible to calculate the film thickness distribution for each thin film by simultaneously irradiating the light and separating the reflected light into each wavelength component.
  • OA filter, liquid crystal wavelength filter, etc. can also be used for wavelength selection. It is also preferable to use an irradiation system in which the light irradiation intensity in the observation field (irradiation region) is constant and an optical detection system in which the sensitivity in the field is constant. Even in an irradiation system in which the light irradiation intensity is not constant, the light irradiation intensity can be calibrated based on a reference sample surface (for example, a mirror-polished surface of a silicon single crystal wafer).
  • a reference sample surface for example, a mirror-polished surface of a silicon single crystal wafer.
  • the method for measuring the film thickness distribution of the wafer with a thin film according to the present invention is low in cost since it can be performed with visible light using a normal microscope optical system.
  • the spatial resolution can be freely selected from about the wavelength of the irradiation light to about 100 [ ⁇ m] by changing the magnification of the microscope.
  • the size of one side of the pixel is set to 1/2 or more and 100 [ ⁇ m] or less of the wavelength ⁇ 1 or ⁇ 2 to be irradiated as described above. With such a pixel size, there is no fear that the focus is difficult to be set, and the film thickness distribution of the thin film of the wafer with a thin film can be calculated more accurately with high spatial resolution.
  • the film thickness distribution of the entire wafer surface can be measured by setting the irradiation region at a plurality of locations on the wafer surface with a thin film and measuring the reflected light intensity distribution in the irradiation region at a plurality of locations. Even when measuring the entire surface of the wafer, the measurement wavelength is limited to one wavelength for each thin film (even if the film thickness distribution of both the first thin film and the second thin film is measured) 2 wavelengths), and requires a small amount of calculation and can be measured quickly at low cost.
  • the region irradiated with light by the method for measuring the film thickness distribution of the wafer with a thin film of the present invention can be matched with the lithography exposure site of the device manufacturing process by adjusting the magnification and field of view of the microscope.
  • the film thickness distribution of the thin film that can be effectively used in the device manufacturing process can be calculated.
  • the site used by the stepper at the time of lithography exposure in the device manufacturing process is, for example, about 26 [mm] ⁇ 8 [mm] in size, so that it is matched with the lithography exposure site by adjusting the magnification and field of view of the microscope. be able to.
  • the thin film such as the first thin film and the second thin film is a film formed on the substrate, and the irradiation light transmitted through the film is at the interface with the base (substrate surface or other film).
  • the film has a film thickness that allows reflection and detection of the reflected light from the surface side of the thin film.
  • a profile P1 indicating the wavelength dependence of the reflectance with respect to light in a wavelength region equal to or larger than the wavelength of visible light of the SOI wafer to be measured is calculated by simulation (see FIGS. 4A and 4B).
  • a profile P21 indicating the wavelength dependence of the reflectance with respect to light in a wavelength region equal to or greater than the visible light of an SOI wafer having an SOI layer thicker than the set thickness 10.5 [nm] of the SOI layer by 1 [nm] is calculated by simulation. (See FIG. 4A).
  • a profile P22 indicating the wavelength dependence of the reflectance with respect to light in the wavelength region of visible light or higher of an SOI wafer having a BOX layer thicker by 1 [nm] than the set film thickness 20 [nm] of the BOX layer is calculated by simulation (FIG. 4 (B)).
  • the wavelengths 542 [nm] and 476 [nm] when the profiles P31 and P32 become zero are determined as ⁇ 1 and ⁇ 2, respectively (see FIG. 4C).
  • a profile P1 indicating the wavelength dependence of the reflectance with respect to light in a wavelength region equal to or larger than the wavelength of visible light of the SOI wafer to be measured is calculated by simulation (see FIGS. 5A and 5B).
  • a profile P21 indicating the wavelength dependence of the reflectance with respect to light in a wavelength region of visible light or higher of an SOI wafer having an SOI layer thicker than the set thickness 10 [nm] of the SOI layer by 1 [nm] is calculated by simulation (FIG. 5 (A)).
  • a profile P22 indicating the wavelength dependence of the reflectance with respect to light in the wavelength region of visible light or higher of an SOI wafer having a BOX layer thicker than the set film thickness 15 [nm] of the BOX layer by 1 [nm] is calculated by simulation (FIG. 5 (B)).
  • Wavelengths 502 [nm] and 437 [nm] when the difference profiles P31 and P32 become zero are determined as ⁇ 1 and ⁇ 2, respectively (see FIG. 5C).
  • An SOI wafer (diameter 300 [mm]) having an SOI layer thickness of 12 [nm] and a BOX layer thickness of 25 [nm] is prepared as a measurement object, and this SOI wafer is measured for film thickness distribution by the measurement method of the present invention. Went. At this time, Acumap (measurement beam diameter: about 300 ⁇ m) manufactured by ADE was used as an apparatus for measuring the film thickness of the absolute values of the SOI layer and the BOX layer.
  • the profile P21 when the SOI layer of the SOI wafer becomes 1 [nm] thick was calculated by simulation.
  • ⁇ 1 was 615 [nm].
  • a profile P22 when the BOX layer of the SOI wafer is 1 [nm] thick was calculated by simulation.
  • ⁇ 2 was 530 [nm]. That is, the same results ( ⁇ 1, ⁇ 2) as the graph shown in FIG. 3 were obtained.
  • the outer peripheral area of the SOI layer of the SOI wafer is directed from the wafer center direction to the wafer outer periphery direction at a pixel size of 2.56 [ ⁇ m].
  • the reflected light intensity was measured over the terrace (the outermost periphery without the SOI layer).
  • the upper diagram in FIG. 6A shows a microscopic image of the outer peripheral region of the SOI layer for which the reflected light intensity was measured.
  • a rectangular area surrounded by a white line is an area where the reflected light intensity is measured, and a wavy line indicating minute irregularities in the measurement area indicates a measurement result of the reflected light intensity.
  • a graph in which the vertical scale of the wavy line is enlarged is shown in the lower part of FIG.
  • FIG. 6B is an enlarged view of the horizontal axis of the region (about 300 ⁇ m) surrounded by the dotted line in the lower diagram of FIG. 6A, and the reflected light of each pixel in the linear region having a width of about 300 ⁇ m.
  • the intensity distribution (that is, equivalent to the relative film thickness distribution of the SOI layer in a linear region having a width of about 300 ⁇ m) is shown.
  • the vertical axis represents the reflected light intensity
  • the horizontal axis represents the position in the measurement region.
  • 7B is similar to FIG. 6B, the reflected light intensity distribution of each pixel in a linear region having a width of about 300 ⁇ m in a circular region having a diameter of about 300 ⁇ m (that is, a linear region having a width of about 300 ⁇ m).
  • the relative film thickness distribution of the BOX layer corresponds to the relative film thickness distribution of the BOX layer).
  • FIG. 6C is a graph showing the thickness distribution of the SOI layer in a part of FIG. 6A, and shows the result of FIG. 6B and the average value of the thickness of the SOI layer included in the measurement region. It is calculated from a certain 12.33 nm. As can be seen from FIG. 6C, the thickness distribution of the SOI layer was obtained as an absolute value.
  • FIG. 7C is a graph showing the film thickness distribution of the BOX layer in a part of FIG. 7A, and shows the result of FIG. 7B and the average value of the film thickness of the BOX layer included in the measurement region. It is calculated from a certain 24.95 nm. As can be seen from FIG. 7C, the thickness distribution of the BOX layer was obtained as an absolute value.
  • Table 1 below shows the average value, maximum value, minimum value, PV value (that is, the difference between the maximum value and minimum value), and standard deviation of the film thickness of the SOI layer and BOX layer in the measurement region. .
  • the absolute values of the film thickness of the SOI layer and the BOX layer which could be measured only as an average value of one spot having a measurement beam diameter of about 300 ⁇ m in diameter. It was found that by using the method of the present invention, the film thickness distribution can be accurately measured with a high spatial resolution on the order of ⁇ m.
  • the present invention is not limited to the above embodiment.
  • the above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Testing Or Measuring Of Semiconductors Or The Like (AREA)

Abstract

In the present invention, a profile P1 indicating the wavelength dependence of the reflectance of a wafer with thin film and a profile P21 indicating the wavelength dependence of the reflectance of a wafer with thin film having a second thin film that is t [nm] thicker (or thinner) than a set film thickness T2 for the second thin film are determined through simulation. A wavelength λ1 at which the difference between P1 and P21 is zero is determined. Light of the wavelength λ1 is irradiated onto a wafer with thin film, and a film thickness distribution for a first thin film expressed in relative values is calculated through the measurement of the reflected light intensity. A film thickness distribution for the first thin film expressed in absolute values is calculated from absolute film thickness values measured using a film thickness measurement device capable of measuring the absolute values of the first thin film and the film thickness distribution for the first thin film expressed in relative values. As a result, for a wafer with thin film having a first thin film and second thin film on a substrate, film thickness distributions for the first thin film and/or second thin film can be measured as film thickness distributions expressed using absolute values with a high spatial resolution, without the distributions being influenced by each other, and with a high degree of accuracy.

Description

薄膜付ウェーハの膜厚分布の測定方法Method for measuring film thickness distribution of wafer with thin film
　本発明は、基板上に薄膜を有する薄膜付ウェーハの膜厚分布の測定方法に関する。 The present invention relates to a method for measuring a film thickness distribution of a wafer with a thin film having a thin film on a substrate.
　半導体デバイスの作製のために、ＳＯＩ（Ｓｉｌｉｃｏｎ　Ｏｎ　Ｉｎｓｕｌａｔｏｒ）ウェーハが広く用いられている。ＳＯＩウェーハの一般的な構造は、シリコン基板の上に埋め込み酸化膜層（ＢＯＸ層）が形成され、その上にシリコン単結晶からなるＳＯＩ層が形成されたものである。このように、ＳＯＩウェーハは、薄膜（ＢＯＸ層、ＳＯＩ層）が付いた薄膜付ウェーハである。近年、デザインルールの微細化に伴って、ＳＯＩデバイス作製、特にＦＤ－ＳＯＩ（Ｆｕｌｌｙ　Ｄｅｐｌｅｔｅｄ　ＳＯＩ）デバイス作製に用いるＳＯＩウェーハのＳＯＩ層膜厚分布やＢＯＸ層膜厚分布が、デバイス製造プロセス、ひいては、トランジスタ特性に影響を与えるようになってきている。集積回路においては、回路を構成するトランジスタの特性を均一にすることが重要である。 For the production of semiconductor devices, SOI (Silicon On Insulator) wafers are widely used. A general structure of an SOI wafer is such that a buried oxide film layer (BOX layer) is formed on a silicon substrate, and an SOI layer made of a silicon single crystal is formed thereon. Thus, the SOI wafer is a wafer with a thin film to which a thin film (BOX layer, SOI layer) is attached. In recent years, with the miniaturization of design rules, SOI device film thickness distribution and BOX layer film thickness distribution of SOI wafers used for SOI device fabrication, especially for FD-SOI (Fully Depleted SOI) device fabrication, It has come to influence the transistor characteristics. In an integrated circuit, it is important to make the characteristics of the transistors constituting the circuit uniform.
　分光エリプソ法（分光エリプソメトリー）、反射分光法によるポイント測定においては、各測定点毎に、ある波長範囲（一般的には、可視光域）のスペクトルを取り、そのスペクトルに対してモデル膜構造にフィッティングすることで各測定点の膜厚を求めている。従って、１［μｍ］程度の空間分解能で薄膜の膜厚分布の測定を行おうとすると、測定点数が極端に増えるため、計算量と時間の制約から現実的に測定不可能である。 In point measurement by spectroscopic ellipsometry (spectral ellipsometry) or reflection spectroscopy, a spectrum in a certain wavelength range (generally, visible light region) is taken for each measurement point, and the model film structure is taken for that spectrum. The film thickness at each measurement point is obtained by fitting to. Therefore, if the film thickness distribution of a thin film is measured with a spatial resolution of about 1 [μm], the number of measurement points increases extremely, so that it cannot be practically measured due to the amount of calculation and time constraints.
　またスペクトル測定を行うためには、広い波長領域が必要なため、空間分解能を高くして多点膜厚測定を行うことは事実上不可能である。よって、これらの方法でウェーハ全面を一括して測定可能な装置としては、現状では数１００［μｍ］程度の空間分解能の装置しか存在しない。 In addition, since a wide wavelength region is required to perform spectrum measurement, it is practically impossible to perform multipoint film thickness measurement with high spatial resolution. Therefore, as a device capable of measuring the entire wafer surface collectively by these methods, there is currently only a device having a spatial resolution of about several hundreds [μm].
　このように、薄膜、特には、ＳＯＩウェーハのＳＯＩ層及びＢＯＸ層のそれぞれの膜厚分布についての測定を、高精度で低コストかつ簡便に行うことができる薄膜付ウェーハの膜厚分布の測定方法が求められている。 As described above, the method for measuring the film thickness distribution of a thin film, particularly a wafer with a thin film, which can easily measure the film thickness distribution of each of the SOI layer and the BOX layer of the SOI wafer with high accuracy, low cost, and the like. Is required.
　特許文献１には、ＳＯＩウェーハに白色光を照射し、反射光を各波長別に分光し、波長別の干渉情報からＳＯＩ層膜厚を算出する技術が開示されている。特許文献２には、膜厚１［μｍ］未満のＳＯＩ層に４８８［ｎｍ］のレーザー光を照射し、その正反射光を検出し、照射光との干渉縞によって面内の膜厚バラツキを検査することが記載されている。また特許文献３では、ＳＯＩ層のみの膜厚分布測定を行う方法が記載されている。 Patent Document 1 discloses a technique for irradiating a SOI wafer with white light, dispersing reflected light for each wavelength, and calculating the SOI layer film thickness from interference information for each wavelength. In Patent Document 2, an SOI layer with a film thickness of less than 1 [μm] is irradiated with a laser beam of 488 [nm], its specular reflection light is detected, and in-plane film thickness variation is caused by interference fringes with the irradiated light. The inspection is described. Patent Document 3 describes a method of measuring the film thickness distribution of only the SOI layer.
　特許文献４の方法では、反射率、又はエリプソ法で測定したデータのキャリブレーションカーブからＳＯＩ膜厚を求めている。 In the method of Patent Document 4, the SOI film thickness is obtained from a reflectance or a calibration curve of data measured by an ellipso method.
特開２００２－３４３８４２号公報JP 2002-343842 A 特開平０８－２６４６０５号公報Japanese Patent Laid-Open No. 08-264605 特開２０１１－２４９６２１号公報JP 2011-249621 A 国際公開第ＷＯ２０１４／０７２１０９号International Publication No. WO2014 / 072109
　基板の表面に薄膜を有する薄膜付ウェーハの薄膜の膜厚分布を算出する従来の膜厚測定方法は、分光エリプソ法、反射分光法によるポイント毎の膜厚測定が一般的であるが、ＳＯＩウェーハのような２層の薄膜（ＳＯＩ層及びＢＯＸ層）を有するウェーハのそれぞれの薄膜に対し、１［μｍ］程度の空間分解能で、広範囲の面内を膜厚分布測定できる装置は市販されていない。 The conventional film thickness measurement method for calculating the film thickness distribution of a thin film wafer having a thin film on the surface of the substrate is generally a point-by-point film thickness measurement by spectroscopic ellipsometry or reflection spectroscopy. There is no commercially available device that can measure the film thickness distribution over a wide area with a spatial resolution of about 1 [μm] for each thin film of a wafer having two thin films (SOI layer and BOX layer). .
　特許文献３では、ＳＯＩ層膜厚のみの測定において、測定感度の上がる方法が提案されているが、この方法においては、ＢＯＸ層の膜厚分布の影響を受けてしまい、ＳＯＩ層の膜厚分布を十分な精度で測定することが困難である。またＢＯＸ層の測定は行っていなかった。 Patent Document 3 proposes a method for increasing the measurement sensitivity in measuring only the SOI layer film thickness. However, in this method, the film thickness distribution of the SOI layer is affected by the film thickness distribution of the BOX layer. Is difficult to measure with sufficient accuracy. Moreover, the measurement of the BOX layer was not performed.
　また、ＳＯＩウェーハのような薄膜付きウェーハにおける薄膜の膜厚分布を、高い空間分解能で精度よく算出する際に、相対値だけでなく、絶対値で表された膜厚分布として算出する方法が求められていた。 In addition, when calculating the thickness distribution of a thin film on a wafer with a thin film such as an SOI wafer with high spatial resolution, there is a need for a method for calculating not only a relative value but also a thickness distribution expressed by an absolute value. It was done.
　特許文献４の方法では、上記のように反射率又はエリプソ法で測定したデータのキャリブレーションカーブからＳＯＩ膜厚を求めているが、反射率を測定する際の光学系による影響を受ける。また、ＳＯＩ層とＢＯＸ層の膜厚の組み合わせごとに、反射率又はエリプソ法で測定したＳＯＩ層膜厚値のキャリブレーションカーブを作成する必要があり、煩雑であった。 In the method of Patent Document 4, the SOI film thickness is obtained from the calibration curve of the data measured by the reflectance or the ellipso method as described above, but it is influenced by the optical system when measuring the reflectance. Moreover, it is necessary to create a calibration curve of the SOI layer thickness value measured by the reflectance or the ellipso method for each combination of the thicknesses of the SOI layer and the BOX layer, which is complicated.
　本発明は、上記問題点に鑑みてなされたものであって、基板の表面上に形成された第一薄膜と該第一薄膜上に形成された第二薄膜とを有する薄膜付ウェーハにおいて、第一薄膜及び第二薄膜の少なくともいずれか一方の膜厚分布を、絶対値で表された膜厚分布として、高い空間分解能で、かつ、互いの膜厚分布の影響を受けず精度よく測定することができる薄膜付ウェーハの膜厚分布の測定方法を提供することを目的とする。 The present invention has been made in view of the above problems, and in a wafer with a thin film having a first thin film formed on a surface of a substrate and a second thin film formed on the first thin film, Measuring the film thickness distribution of at least one of the thin film and the second thin film as a film thickness distribution expressed in absolute values with high spatial resolution and without being affected by the film thickness distribution of each other. An object of the present invention is to provide a method for measuring the film thickness distribution of a thin film-coated wafer.
　上記目的を達成するために、本発明は、基板の表面上に形成された第一薄膜と、該第一薄膜の表面上に形成された第二薄膜とを有する薄膜付ウェーハの前記第一薄膜及び第二薄膜の少なくともいずれか一方の膜厚分布を測定する薄膜付ウェーハの膜厚分布の測定方法であって、
　前記測定対象の薄膜付ウェーハの可視光の波長以上の波長領域の光に対する反射率の波長依存性を示すプロファイルＰ１をシミュレーションにより算出する工程を有し、
　前記測定対象の薄膜付ウェーハの前記第二薄膜の設定膜厚Ｔ２よりｔ［ｎｍ］だけ薄い、又は厚い第二薄膜を有する薄膜付ウェーハの可視光以上の波長領域の光に対する反射率の波長依存性を示すプロファイルＰ２１をシミュレーションにより算出するサブステップと、前記算出した両方のプロファイルＰ１、Ｐ２１の差のプロファイルＰ３１（＝Ｐ２１－Ｐ１）を算出し、該算出した差のプロファイルＰ３１がゼロとなるときの波長λ１を求めるサブステップとにより、前記波長λ１を求める工程と、
　前記測定対象の薄膜付ウェーハの前記第一薄膜の設定膜厚Ｔ１よりｔ［ｎｍ］だけ薄い、又は厚い第一薄膜を有する薄膜付ウェーハの可視光以上の波長領域の光に対する反射率の波長依存性を示すプロファイルＰ２２をシミュレーションにより算出するサブステップと、前記算出した両方のプロファイルＰ１、Ｐ２２の差のプロファイルＰ３２（＝Ｐ２２－Ｐ１）を算出し、該算出した差のプロファイルＰ３２がゼロとなるときの波長λ２を求めるサブステップとにより、前記波長λ２を求める工程と、
　のうち、少なくともいずれか一方の工程を有し、
　前記測定対象の薄膜付ウェーハ表面の一部領域である照射領域に対して、単一波長である前記波長λ１及び波長λ２の少なくともいずれか一方の光を照射する工程と、
　前記照射領域からの反射光を前記波長λ１及び波長λ２の少なくともいずれか一方に対して検出して前記照射領域を多数に分割したピクセル毎の反射光強度を測定することによって、前記照射領域内の前記波長λ１及び波長λ２の少なくともいずれか一方に対する反射光強度分布を求める工程と、
　前記波長λ１に対する反射光強度分布から前記照射領域内における前記第一薄膜の相対値で表された膜厚分布を算出することと、前記波長λ２に対する反射光強度分布から前記照射領域内における前記第二薄膜の相対値で表された膜厚分布を算出することの少なくともいずれか一方を行う工程と、
　前記第一薄膜及び前記第二薄膜の膜厚の少なくともいずれか一方の絶対値を測定可能な膜厚測定装置を用いて、前記照射領域内の前記第一薄膜及び前記第二薄膜の少なくともいずれか一方の膜厚の絶対値を測定する工程と、
　該測定された膜厚の絶対値と、前記第一薄膜の相対値で表された膜厚分布及び前記第二薄膜の相対値で表された膜厚分布の少なくともいずれか一方に基づいて、前記照射領域内の前記第一薄膜の絶対値で表された膜厚分布及び前記照射領域内の前記第二薄膜の絶対値で表された膜厚分布の少なくともいずれか一方を算出する工程と、
　を有することを特徴とする薄膜付ウェーハの膜厚分布の測定方法を提供する。 To achieve the above object, the present invention provides the first thin film of a wafer with a thin film comprising a first thin film formed on the surface of the substrate and a second thin film formed on the surface of the first thin film. And a method for measuring the film thickness distribution of the wafer with a thin film for measuring the film thickness distribution of at least one of the second thin film,
A step of calculating by simulation a profile P1 indicating the wavelength dependence of the reflectance with respect to light in a wavelength region equal to or greater than the wavelength of visible light of the wafer with a thin film to be measured;
Wavelength dependence of reflectance with respect to light in a wavelength region greater than or equal to visible light of a wafer with a thin film having a second thin film that is thinner or thicker than the set film thickness T2 of the second thin film of the wafer with the thin film to be measured. The sub-step of calculating the profile P21 indicating the characteristics by simulation and the difference profile P31 (= P21−P1) between the two calculated profiles P1 and P21, and the calculated difference profile P31 is zero A step of determining the wavelength λ1 by a sub-step of determining the wavelength λ1 of
Wavelength dependence of reflectance for light in a wavelength region greater than or equal to visible light of a wafer with a thin film having a first thin film that is thinner or thicker than the set film thickness T1 of the first thin film of the wafer with a thin film to be measured A sub-step of calculating a profile P22 indicating the characteristics by simulation and a difference profile P32 (= P22−P1) between the two calculated profiles P1 and P22, and when the calculated difference profile P32 becomes zero A step of determining the wavelength λ2 by a sub-step of determining the wavelength λ2 of
At least one of the steps,
Irradiating at least one of the wavelengths λ1 and λ2 with a single wavelength to an irradiation region that is a partial region of the surface of the wafer with a thin film to be measured;
By detecting the reflected light from the irradiation region with respect to at least one of the wavelength λ1 and the wavelength λ2 and measuring the reflected light intensity for each pixel obtained by dividing the irradiation region into a large number, Obtaining a reflected light intensity distribution for at least one of the wavelengths λ1 and λ2,
Calculating a film thickness distribution represented by a relative value of the first thin film in the irradiation region from the reflected light intensity distribution with respect to the wavelength λ1, and calculating the film thickness distribution in the irradiation region from the reflected light intensity distribution with respect to the wavelength λ2. Performing at least one of calculating the film thickness distribution represented by the relative value of the two thin films;
Using a film thickness measuring device capable of measuring an absolute value of at least one of the film thicknesses of the first thin film and the second thin film, at least one of the first thin film and the second thin film in the irradiation region Measuring the absolute value of one film thickness;
Based on at least one of the absolute value of the measured film thickness, the film thickness distribution represented by the relative value of the first thin film, and the film thickness distribution represented by the relative value of the second thin film, Calculating at least one of the film thickness distribution represented by the absolute value of the first thin film in the irradiation region and the film thickness distribution represented by the absolute value of the second thin film in the irradiation region;
A method for measuring the film thickness distribution of a wafer with a thin film is provided.
　このように、第二薄膜の膜厚が設定膜厚から変動しても、薄膜付ウェーハからの反射率が変動しない波長λ１の光を薄膜付ウェーハに照射して照射領域内の反射光強度を測定することにより、照射領域内の第一薄膜の相対値で表された膜厚分布を、第二薄膜の膜厚分布の影響を受けずに精度よく算出することができる。同様に、第一薄膜の膜厚が設定膜厚から変動しても、薄膜付ウェーハからの反射率が変動しない波長λ２の光を薄膜付ウェーハに照射して照射領域内の反射光強度を測定することにより、照射領域内の第二薄膜の相対値で表された膜厚分布を、第一薄膜の膜厚分布の影響を受けずに高い空間分解能で精度よく算出することができる。そのため、これらの相対値で表された膜厚分布と、膜厚測定装置によって測定された膜厚の絶対値とに基づくことにより、第一薄膜及び第二薄膜の少なくともいずれか一方の膜厚分布を、絶対値で表された膜厚分布として、高い空間分解能で、かつ、互いの膜厚分布の影響を受けず精度よく測定することができる。本発明では、第一薄膜の絶対値で表された膜厚分布及び第二薄膜の絶対値で表された膜厚分布のうち、少なくともいずれか一方を測定することができる。また照射する光の波長を、各々単一波長であるλ１及びλ２の少なくともいずれか一方に限定しているため、膜厚分布を算出するための計算量が少なく、低コストかつ簡便で迅速な測定が可能である。 In this way, even if the film thickness of the second thin film varies from the set film thickness, the reflected light intensity in the irradiation area is irradiated by irradiating the thin film wafer with light having a wavelength λ1 that does not vary the reflectivity from the thin film wafer. By measuring, the film thickness distribution represented by the relative value of the first thin film in the irradiation region can be accurately calculated without being affected by the film thickness distribution of the second thin film. Similarly, even if the film thickness of the first thin film fluctuates from the set film thickness, the reflected light intensity in the irradiated area is measured by irradiating the thin film wafer with light of wavelength λ2, which does not change the reflectivity from the thin film wafer. By doing so, the film thickness distribution represented by the relative value of the second thin film in the irradiation region can be accurately calculated with high spatial resolution without being affected by the film thickness distribution of the first thin film. Therefore, based on the film thickness distribution represented by these relative values and the absolute value of the film thickness measured by the film thickness measuring device, the film thickness distribution of at least one of the first thin film and the second thin film. Can be measured with high spatial resolution as a film thickness distribution represented by an absolute value and with high accuracy without being influenced by the film thickness distribution of each other. In the present invention, at least one of the film thickness distribution represented by the absolute value of the first thin film and the film thickness distribution represented by the absolute value of the second thin film can be measured. In addition, since the wavelength of the irradiated light is limited to at least one of λ1 and λ2, which are each a single wavelength, the calculation amount for calculating the film thickness distribution is small, and the measurement is simple, low cost, and low cost. Is possible.
　このとき、前記測定対象の薄膜付ウェーハがＳＯＩウェーハであり、前記第一薄膜が埋め込み酸化膜層であり、前記第二薄膜がシリコン単結晶からなるＳＯＩ層であるものとすることができる。 At this time, the wafer with a thin film to be measured may be an SOI wafer, the first thin film may be a buried oxide film layer, and the second thin film may be an SOI layer made of a silicon single crystal.
　このように測定対象の薄膜付ウェーハがＳＯＩウェーハである場合、照射領域内の埋め込み酸化膜層とＳＯＩ層の膜厚分布を精度よく算出することができる。 Thus, when the wafer with a thin film to be measured is an SOI wafer, the film thickness distribution of the buried oxide film layer and the SOI layer in the irradiation region can be calculated with high accuracy.
　また、前記波長λ１及び波長λ２の少なくともいずれか一方は、可視光波長から選択された単一の波長であることが好ましい。 Further, it is preferable that at least one of the wavelength λ1 and the wavelength λ2 is a single wavelength selected from visible light wavelengths.
　本発明の薄膜付ウェーハの膜厚分布の測定方法は、通常の顕微鏡光学系を用いて可視光で行えるため低コストで実施できる。 The method for measuring the film thickness distribution of the wafer with a thin film of the present invention can be carried out at low cost because it can be performed with visible light using a normal microscope optical system.
　また、前記ピクセルの一辺のサイズを、前記波長λ１又は波長λ２の１／２以上１００［μｍ］以下とすることが好ましい。 Further, it is preferable that the size of one side of the pixel is not less than 1/2 of the wavelength λ1 or the wavelength λ2 and not more than 100 [μm].
　このようなピクセルサイズであれば、焦点が結びにくくなる恐れがなく、より正確に高い空間分解能で薄膜付ウェーハの薄膜の相対的な膜厚分布を算出することができ、その結果、絶対値で表された膜厚分布も高い空間分解能で算出することができる。 With such a pixel size, there is no risk that the focal point will be difficult to focus on, and the relative film thickness distribution of the thin film of the thin film wafer can be calculated more accurately and with high spatial resolution. The expressed film thickness distribution can also be calculated with high spatial resolution.
　また、前記照射領域をデバイス製造工程のリソグラフィー露光サイトに一致させることが好ましい。 Further, it is preferable that the irradiation area is matched with the lithography exposure site of the device manufacturing process.
　このように、本発明の薄膜付ウェーハの膜厚分布の測定方法における照射領域を、顕微鏡の倍率や視野範囲を調整するなどしてリソグラフィー露光サイトに一致させることにより、デバイス製造工程で有効に活用しうる薄膜の絶対値で表された膜厚分布を算出することができる。 As described above, the irradiation area in the method for measuring the film thickness distribution of the wafer with a thin film of the present invention is effectively utilized in the device manufacturing process by matching the lithography exposure site by adjusting the magnification and field of view of the microscope. The film thickness distribution represented by the absolute value of the possible thin film can be calculated.
　また、前記第一薄膜及び第二薄膜の少なくともいずれか一方の前記相対値で表された膜厚分布を算出する前記照射領域を、前記薄膜付ウェーハの面内の複数箇所に設定することにより、全面における絶対値で表された膜厚分布を求めることが好ましい。 Moreover, by setting the irradiation region for calculating the film thickness distribution represented by the relative value of at least one of the first thin film and the second thin film, at a plurality of locations in the surface of the wafer with the thin film, It is preferable to obtain a film thickness distribution expressed as an absolute value on the entire surface.
　このように照射領域を薄膜付ウェーハの面内の複数箇所に設定することにより、薄膜付ウェーハ全面に亘る測定を、高精度で低コストかつ簡便に行うことができる。 Thus, by setting the irradiation area at a plurality of locations within the surface of the wafer with a thin film, the measurement over the entire surface of the wafer with a thin film can be performed with high accuracy, low cost and simply.
　また、前記膜厚測定装置が、分光エリプソ法又は反射分光法を使用した装置であることが好ましい。 Further, it is preferable that the film thickness measuring apparatus is an apparatus using a spectroscopic ellipso method or a reflection spectroscopic method.
　このように、分光エリプソ法又は反射分光法を使用した装置であれば、簡便かつ高精度で薄膜の膜厚の絶対値を測定可能である。 As described above, if the apparatus uses the spectroscopic ellipso method or the reflection spectroscopic method, the absolute value of the film thickness of the thin film can be measured easily and with high accuracy.
　また、本発明の薄膜付ウェーハの膜厚分布の測定方法では、前記波長λ１及び前記波長λ２のうち、前記波長λ１のみを求めることによって、前記第一薄膜の絶対値で表された膜厚分布のみを算出することができる。また、前記波長λ１及び前記波長λ２のうち、前記波長λ２のみを求めることによって、前記第二薄膜の絶対値で表された膜厚分布のみを算出することもできる。 In the method for measuring the film thickness distribution of the wafer with a thin film according to the present invention, the film thickness distribution represented by the absolute value of the first thin film by obtaining only the wavelength λ1 out of the wavelength λ1 and the wavelength λ2. Only can be calculated. Moreover, only the film thickness distribution represented by the absolute value of the second thin film can be calculated by obtaining only the wavelength λ2 out of the wavelengths λ1 and λ2.
　このように、本発明の薄膜付ウェーハの膜厚分布の測定方法では、目的に応じて、第一薄膜及び第二薄膜のいずれか一方のみの絶対値で表された膜厚分布を測定することができる。この場合、相対値で表された膜厚分布の測定は、λ１とλ２のいずれか一方のみで行うことができるので、より迅速かつ低コストの測定方法とすることができる。 As described above, in the method for measuring the film thickness distribution of the wafer with a thin film according to the present invention, the film thickness distribution represented by the absolute value of only one of the first thin film and the second thin film is measured according to the purpose. Can do. In this case, since the measurement of the film thickness distribution represented by the relative value can be performed with only one of λ1 and λ2, a more rapid and low-cost measurement method can be achieved.
　本発明によれば、第一薄膜及び第二薄膜の少なくともいずれか一方の膜厚分布を、絶対値で表された膜厚分布として、高い空間分解能で、かつ、互いの膜厚分布の影響を受けず精度よく測定することができる。本発明では、第一薄膜の絶対値で表された膜厚分布及び第二薄膜の絶対値で表された膜厚分布のうち、少なくともいずれか一方を測定することができる。また、照射する光の波長を、各々単一波長であるλ１及びλ２の少なくともいずれか一方に限定しているため、膜厚分布を算出するための計算量が少なく、低コストかつ簡便で迅速な測定が可能である。 According to the present invention, the film thickness distribution of at least one of the first thin film and the second thin film is a film thickness distribution represented by an absolute value, and the influence of the film thickness distribution on each other with high spatial resolution. It is possible to measure accurately without receiving. In the present invention, at least one of the film thickness distribution represented by the absolute value of the first thin film and the film thickness distribution represented by the absolute value of the second thin film can be measured. In addition, since the wavelength of the light to be irradiated is limited to at least one of λ1 and λ2 each having a single wavelength, the calculation amount for calculating the film thickness distribution is small, and the cost is low, simple and quick. Measurement is possible.
本発明の薄膜付ウェーハの膜厚分布の測定方法の工程を示すフロー図である。It is a flowchart which shows the process of the measuring method of the film thickness distribution of the wafer with a thin film of this invention. 本発明の薄膜付ウェーハの膜厚分布の測定方法で使用することができる光学顕微鏡装置を示す概略図である。It is the schematic which shows the optical microscope apparatus which can be used with the measuring method of the film thickness distribution of the wafer with a thin film of this invention. ＳＯＩウェーハについてシミュレーションにより算出した各プロファイルの一例を示す図である。It is a figure which shows an example of each profile computed by simulation about the SOI wafer. ＳＯＩウェーハについてシミュレーションにより算出した各プロファイルの他の一例を示す図である。It is a figure which shows another example of each profile calculated by simulation about the SOI wafer. ＳＯＩウェーハについてシミュレーションにより算出した各プロファイルの他の一例を示す図である。It is a figure which shows another example of each profile calculated by simulation about the SOI wafer. （Ａ）は、ＳＯＩ層表面外周部の顕微鏡像（上図）と、その反射光強度分布を示す図（下図）である。（Ｂ）は、（Ａ）の一部分における反射光強度分布を示すグラフである。（Ｃ）は、（Ａ）の一部分におけるＳＯＩ層の絶対値で表された膜厚分布を示すグラフである。(A) is a microscopic image (upper figure) of the outer peripheral part of the SOI layer surface and a diagram (lower figure) showing the reflected light intensity distribution. (B) is a graph showing the reflected light intensity distribution in a part of (A). (C) is a graph which shows the film thickness distribution represented by the absolute value of the SOI layer in a part of (A). （Ａ）は、ＳＯＩ層表面外周部の顕微鏡像（上図）と、その反射光強度分布を示す図（下図）である。（Ｂ）は、（Ａ）の一部分における反射光強度分布を示すグラフである。（Ｃ）は、（Ａ）の一部分におけるＢＯＸ層の絶対値で表された膜厚分布を示すグラフである。(A) is a microscopic image (upper figure) of the outer peripheral part of the SOI layer surface and a diagram (lower figure) showing the reflected light intensity distribution. (B) is a graph showing the reflected light intensity distribution in a part of (A). (C) is a graph which shows the film thickness distribution represented by the absolute value of the BOX layer in a part of (A). シミュレーションにより求めた、ＳＯＩ膜厚と反射率（Ｒ）との関係を示すグラフである。It is a graph which shows the relationship between SOI film thickness and reflectance (R) which were calculated | required by simulation.
　以下、本発明について、実施態様の一例として、図を参照しながら詳細に説明するが、本発明はこれに限定されるものではない。 Hereinafter, the present invention will be described in detail as an example of an embodiment with reference to the drawings, but the present invention is not limited thereto.
　図１は本発明の薄膜付ウェーハの膜厚分布の測定方法の工程を示すフロー図である。 FIG. 1 is a flowchart showing the steps of the method for measuring the film thickness distribution of a wafer with a thin film according to the present invention.
　本発明の薄膜付ウェーハの膜厚分布の測定方法の測定対象は、基板の表面上に形成された第一薄膜と、該第一薄膜の表面上に形成された第二薄膜とを有する薄膜付ウェーハである。例えば、この測定対象の薄膜付ウェーハの例として、シリコン基板の上に第一薄膜として埋め込み酸化膜層（ＢＯＸ層）が形成され、その上に第二薄膜としてシリコン単結晶からなるＳＯＩ層が形成されたＳＯＩウェーハが挙げられる。ここでは、薄膜付ウェーハをこのようなＳＯＩウェーハとした場合を例として説明する。ここで、ＳＯＩウェーハの製造時にそれぞれ設定した、埋め込み酸化膜層の設定膜厚をＴ１［ｎｍ］、ＳＯＩ層の設定膜厚をＴ２［ｎｍ］とする。 The measuring object of the method for measuring the film thickness distribution of the wafer with a thin film of the present invention is a thin film having a first thin film formed on the surface of the substrate and a second thin film formed on the surface of the first thin film. It is a wafer. For example, as an example of a wafer with a thin film to be measured, a buried oxide film layer (BOX layer) is formed as a first thin film on a silicon substrate, and an SOI layer made of silicon single crystal is formed thereon as a second thin film. SOI wafers that have been manufactured. Here, a case where the wafer with a thin film is such an SOI wafer will be described as an example. Here, it is assumed that the set film thickness of the buried oxide film layer set at the time of manufacturing the SOI wafer is T1 [nm], and the set film thickness of the SOI layer is T2 [nm].
　本発明では、第一薄膜の膜厚分布及び第二薄膜の膜厚分布のうち、いずれか一方を測定することができるが、両者を測定することもできる。以下では、主に第一薄膜及び第二薄膜の両方の膜厚分布の測定を行う場合について説明する。 In the present invention, either the film thickness distribution of the first thin film or the film thickness distribution of the second thin film can be measured, but both can also be measured. Below, the case where the thickness distribution of both a 1st thin film and a 2nd thin film is mainly measured is demonstrated.
　本発明の薄膜付ウェーハの膜厚分布の測定方法では、測定対象のＳＯＩウェーハのＳＯＩ層、埋め込み酸化膜層のそれぞれの膜厚変動に対して反射率が変動しない単一波長λ１及びλ２を選択し、その選択した単一波長の光を用いて埋め込み酸化膜層、ＳＯＩ層それぞれの膜厚分布の算出を行う。この単一波長λ１、λ２を選択するために以下に示す工程を実施する。 In the method for measuring the film thickness distribution of a wafer with a thin film according to the present invention, single wavelengths λ1 and λ2 are selected in which the reflectance does not vary with respect to the film thickness variations of the SOI layer and buried oxide film layer of the SOI wafer to be measured. Then, the film thickness distribution of each of the buried oxide film layer and the SOI layer is calculated using the selected single wavelength light. In order to select the single wavelengths λ1 and λ2, the following steps are performed.
　初めに、第一薄膜、すなわち埋め込み酸化膜層の膜厚分布を測定するための単一波長λ１の決定方法について説明する。 First, a method for determining the single wavelength λ1 for measuring the film thickness distribution of the first thin film, that is, the buried oxide film layer will be described.
　まず、測定対象のＳＯＩウェーハの可視光の波長以上の波長領域の光に対する反射率の波長依存性を示すプロファイルＰ１をシミュレーションにより算出する（図１のＡ参照）。 First, a profile P1 indicating the wavelength dependence of the reflectance with respect to light in a wavelength region equal to or larger than the wavelength of visible light of the SOI wafer to be measured is calculated by simulation (see A in FIG. 1).
　次に、測定対象のＳＯＩウェーハの第二薄膜、すなわちＳＯＩ層の設定膜厚Ｔ２よりｔ［ｎｍ］だけ薄い、又は厚いＳＯＩ層を有するＳＯＩウェーハの可視光以上の波長領域の光に対する反射率の波長依存性を示すプロファイルＰ２１をシミュレーションにより算出する（図１のＢ参照）。ここで、ｔの値は特に限定されないが、例えば１［ｎｍ］程度とすることができる。また、Ｔ１、Ｔ２の値も特に限定されないが、説明を分かりやすくするため、ここでは一例としてＴ１を２５［ｎｍ］、Ｔ２を１２［ｎｍ］とした場合について述べる。 Next, the reflectance of the second thin film of the SOI wafer to be measured, that is, the reflectivity for light in the wavelength region above the visible light of the SOI wafer having an SOI layer thinner or thicker than the set film thickness T2 of the SOI layer by t [nm]. A profile P21 indicating wavelength dependence is calculated by simulation (see B in FIG. 1). Here, the value of t is not particularly limited, but may be, for example, about 1 [nm]. In addition, although the values of T1 and T2 are not particularly limited, in order to make the explanation easy to understand, a case where T1 is 25 [nm] and T2 is 12 [nm] will be described here as an example.
　図３（Ａ）は、測定対象のＳＯＩウェーハのＳＯＩ層の設定膜厚Ｔ２が１２［ｎｍ］、埋め込み酸化膜（ＢＯＸ）層の設定膜厚Ｔ１が２５［ｎｍ］の場合のプロファイルＰ１と、その測定対象のＳＯＩウェーハよりＳＯＩ層が１［ｎｍ］厚くなった、すなわち、ＳＯＩ層の設定膜厚Ｔ２が１３［ｎｍ］、埋め込み酸化膜層の設定膜厚Ｔ１が２５［ｎｍ］のＳＯＩウェーハからの反射率の波長依存性を示すプロファイルＰ２１の一例を示す図である。図３（Ａ）に示すように、ＳＯＩ層の厚さを変更することで反射率の波長依存性を示すプロファイルＰ２１がＰ１から変化している。 FIG. 3A shows a profile P1 when the set film thickness T2 of the SOI layer of the SOI wafer to be measured is 12 [nm] and the set film thickness T1 of the buried oxide film (BOX) layer is 25 [nm]. An SOI wafer in which the SOI layer is 1 [nm] thicker than the SOI wafer to be measured, that is, the SOI layer has a set film thickness T2 of 13 [nm] and the buried oxide film layer has a set film thickness T1 of 25 [nm]. It is a figure which shows an example of the profile P21 which shows the wavelength dependence of the reflectance from a. As shown in FIG. 3A, the profile P21 indicating the wavelength dependence of the reflectance is changed from P1 by changing the thickness of the SOI layer.
　次に、シミュレーションにより算出した両方のプロファイルＰ１、Ｐ２１の差のプロファイルＰ３１（＝Ｐ２１－Ｐ１）を算出し、該算出した差のプロファイルＰ３１がゼロとなるときの波長λ１を求める（図１のＣ参照）。ここで、プロファイルＰ３１は、Ｐ１とＰ２１間の反射率差の波長依存性を示すプロファイルである。 Next, a difference profile P31 (= P21−P1) between both profiles P1 and P21 calculated by the simulation is calculated, and a wavelength λ1 when the calculated difference profile P31 becomes zero is obtained (C in FIG. 1). reference). Here, the profile P31 is a profile indicating the wavelength dependence of the reflectance difference between P1 and P21.
　図３（Ｃ）には、図３（Ａ）に示したプロファイルＰ１、Ｐ２１の差のプロファイルＰ３１が示されている。図３（Ｃ）に示すように、この場合のプロファイルＰ３１がゼロとなるとき、すなわち反射率差がゼロになるときの波長（ここでは６１５［ｎｍ］）を波長λ１と決定する。このように、図１のＢ及びＣのそれぞれは、波長λ１を求める工程のサブステップである。 FIG. 3C shows a difference profile P31 between the profiles P1 and P21 shown in FIG. As shown in FIG. 3C, the wavelength (in this case, 615 [nm]) when the profile P31 in this case becomes zero, that is, the reflectance difference becomes zero, is determined as the wavelength λ1. Thus, each of B and C in FIG. 1 is a sub-step of the process of obtaining the wavelength λ1.
　次に、第二薄膜、すなわちＳＯＩ層の膜厚分布を測定するための単一波長λ２の決定方法について説明する。 Next, a method for determining the single wavelength λ2 for measuring the film thickness distribution of the second thin film, that is, the SOI layer will be described.
　測定対象のＳＯＩウェーハの埋め込み酸化膜層の設定膜厚Ｔ１よりｔ［ｎｍ］だけ薄い、又は厚いＳＯＩ層を有するＳＯＩウェーハの可視光以上の波長領域の光に対する反射率の波長依存性を示すプロファイルＰ２２をシミュレーションにより算出する（図１のＤ参照）。 Profile showing the wavelength dependence of the reflectivity of the SOI wafer having a thick SOI layer that is thinner or thicker than the set film thickness T1 of the buried oxide film layer of the SOI wafer to be measured with respect to light in the wavelength region above the visible light P22 is calculated by simulation (see D in FIG. 1).
　図３（Ｂ）は、測定対象のＳＯＩウェーハのＳＯＩ層の設定膜厚Ｔ２が１２［ｎｍ］、埋め込み酸化膜層の設定膜厚Ｔ１が２５［ｎｍ］の場合のプロファイルＰ１と、その測定対象のＳＯＩウェーハより埋め込み酸化膜層が１［ｎｍ］厚くなった、すなわち、埋め込み酸化膜層の設定膜厚Ｔ１が２６［ｎｍ］、ＳＯＩ層の設定膜厚Ｔ２が１２［ｎｍ］のＳＯＩウェーハからの反射率の波長依存性を示すプロファイルＰ２２の一例を示す図である。 FIG. 3B shows the profile P1 when the set film thickness T2 of the SOI layer of the SOI wafer to be measured is 12 [nm] and the set film thickness T1 of the buried oxide film layer is 25 [nm], and the measurement object The buried oxide film layer is thicker than the SOI wafer by 1 [nm], that is, from the SOI wafer having the buried oxide film layer set thickness T1 of 26 [nm] and the SOI layer set film thickness T2 of 12 [nm]. It is a figure which shows an example of the profile P22 which shows the wavelength dependence of the reflectance.
　次に、シミュレーションにより算出した両方のプロファイルＰ１、Ｐ２２の差のプロファイルＰ３２（＝Ｐ２２－Ｐ１）を算出し、該算出した差のプロファイルＰ３２がゼロとなるとき、すなわち反射率差がゼロになるときの波長を波長λ２と決定する（図１のＥ参照）。図３（Ｃ）には、プロファイルＰ３２についても示しており、該図３（Ｃ）から分かるように、この場合の波長λ２は５３０［ｎｍ］である。このように、図１のＤ及びＥのそれぞれは、波長λ２を求める工程のサブステップである。 Next, a difference profile P32 (= P22−P1) between both profiles P1 and P22 calculated by simulation is calculated, and when the calculated difference profile P32 becomes zero, that is, when the reflectance difference becomes zero. Is determined as a wavelength λ2 (see E in FIG. 1). FIG. 3C also shows the profile P32. As can be seen from FIG. 3C, the wavelength λ2 in this case is 530 [nm]. Thus, each of D and E in FIG. 1 is a sub-step of the process of obtaining the wavelength λ2.
　尚、λ１とλ２の決定の順番は必ずしも上記の順番である必要はなく、先にλ２を求めてからλ１を決定してもよい。この場合、図１の工程の順番は、Ａ、Ｄ、Ｅ、Ｂ、Ｃの順番になる。また、本発明において、第一薄膜の絶対値で表された膜厚分布のみを算出することを目的とする場合は、波長λ１及び波長λ２のうち、波長λ１のみを求めることとしてもよい。この場合、図１のＤ及びＥ（波長λ２を求める工程）は行われない。また、第二薄膜の絶対値で表された膜厚分布のみを算出することを目的とする場合は、波長λ１及び波長λ２のうち、波長λ２のみを求めることとしてもよい。この場合、図１のＢ及びＣ（波長λ１を求める工程）は行われない。 Note that the order of determining λ1 and λ2 is not necessarily the above order, and λ1 may be determined after λ2 is obtained first. In this case, the order of the steps in FIG. 1 is A, D, E, B, C. In the present invention, when it is intended to calculate only the film thickness distribution represented by the absolute value of the first thin film, only the wavelength λ1 may be obtained from the wavelengths λ1 and λ2. In this case, D and E (step for obtaining the wavelength λ2) in FIG. 1 are not performed. Moreover, when it is intended to calculate only the film thickness distribution expressed by the absolute value of the second thin film, only the wavelength λ2 may be obtained from the wavelengths λ1 and λ2. In this case, B and C (step for obtaining the wavelength λ1) in FIG. 1 are not performed.
　次いで、膜厚分布を測定するＳＯＩウェーハ表面の一部領域に、上記のように予め選択した単一波長λ１、λ２の光をそれぞれ照射する（図１のＦ参照）。その照射した一部領域（照射領域）から反射光を検出してその照射領域を多数に分割したピクセル毎の反射率を測定する（図１のＧ参照）。 Next, light having the single wavelengths λ1 and λ2 selected in advance as described above is irradiated onto a partial region on the surface of the SOI wafer whose thickness distribution is to be measured (see F in FIG. 1). Reflected light is detected from the irradiated partial region (irradiation region), and the reflectance of each pixel obtained by dividing the irradiation region into a large number is measured (see G in FIG. 1).
　一方、ピクセル毎の反射率を求めた照射領域を含む領域について、膜厚の絶対値が測定可能な装置（外部装置）により、第一薄膜及び第二薄膜の膜厚の絶対値を測定する（図１のＨ参照）。この膜厚の絶対値が測定可能な装置（外部装置）としては、分光エリプソ法又は反射分光法を使用した装置を好適に用いることができる。分光エリプソ法又は反射分光法を使用した装置であれば、簡便かつ精度高く薄膜の膜厚の絶対値を測定可能である。 On the other hand, the absolute value of the film thickness of the first thin film and the second thin film is measured by a device (external device) capable of measuring the absolute value of the film thickness for the region including the irradiation region for which the reflectance for each pixel is obtained ( (See H in FIG. 1). As an apparatus (external apparatus) capable of measuring the absolute value of the film thickness, an apparatus using a spectral ellipsometry method or a reflection spectroscopy method can be suitably used. If the apparatus uses a spectroscopic ellipsometry method or a reflection spectroscopy method, the absolute value of the film thickness of the thin film can be measured easily and accurately.
　さらに、その絶対値に基づいて下記の算出法を用いて、第一薄膜及び第二薄膜の膜厚の絶対値の膜厚分布を算出する（図１のＩ参照）。 Further, based on the absolute value, the following calculation method is used to calculate the absolute thickness distribution of the first thin film and the second thin film (see I in FIG. 1).
＜ピクセル毎の膜厚絶対値の算出法＞
　前述の方法により求められた波長λ２は、ＢＯＸ層の膜厚が変動してもＳＯＩウェーハの反射率が変動しない波長を意味している。そこで、波長λ２を用い、ＢＯＸ層の膜厚を２５ｎｍに固定し、設計膜厚である１２ｎｍ付近のＳＯＩ膜厚と反射率（Ｒ）との関係をシミュレーションにより求めると、図８が得られる。 <Calculation method of film thickness absolute value for each pixel>
The wavelength λ2 obtained by the above-described method means a wavelength at which the reflectance of the SOI wafer does not vary even when the film thickness of the BOX layer varies. Therefore, when the wavelength λ2 is used, the thickness of the BOX layer is fixed to 25 nm, and the relationship between the SOI thickness near the design thickness of 12 nm and the reflectance (R) is obtained by simulation, FIG. 8 is obtained.
　図８において、ＳＯＩ層の膜厚の変動（ΔＳＯＩ）に伴う反射率変化をΔＲとし、ΔＲを反射率Ｒで規格化したΔＲ／Ｒを反射率変動率とし、ＳＯＩ膜厚に対する反射率変動率の傾きをＣとすると、傾きＣ＝ΔＳＯＩ／（ΔＲ／Ｒ）となる。 In FIG. 8, the change in reflectivity due to the change in thickness (ΔSOI) of the SOI layer is ΔR, ΔR is normalized by the reflectivity R, ΔR / R is the reflectivity change rate, and the reflectivity change rate with respect to the SOI film thickness If the slope of C is C, the slope C = ΔSOI / (ΔR / R).
　また、全ピクセルの平均反射率をＲｍ、各ピクセル毎の反射率とＲｍとの差をΔＲｍ、外部装置により測定されたＳＯＩ膜厚をＴ０とすると、求める各ピクセル毎のＳＯＩ膜厚の絶対値Ｔｐは、下記の式（１）で求めることができる。
　　Ｔｐ＝Ｔ０＋（ΔＲｍ／Ｒｍ）×Ｃ・・・式（１） Also, if the average reflectance of all pixels is Rm, the difference between the reflectance and Rm of each pixel is ΔRm, and the SOI film thickness measured by the external device is T0, the absolute value of the SOI film thickness for each pixel to be obtained is calculated. Tp can be obtained by the following equation (1).
Tp = T0 + (ΔRm / Rm) × C (1)
　同様に、波長λ１を用いることによって、各ピクセル毎のＢＯＸ膜厚の絶対値を求めることができる。 Similarly, the absolute value of the BOX film thickness for each pixel can be obtained by using the wavelength λ1.
　選択した単一波長λ１、λ２の光を照射する具体的な方法としては、例えば図２に示すような光学顕微鏡を用いることができる。図２に示すように、波長選択のためのバンドパスフィルター４を取り付けた一般的な光学顕微鏡装置２の光源３からの照射光を、膜厚分布を測定する薄膜付ウェーハ１の一部領域に照射することで実施することができる。 As a specific method for irradiating the selected single wavelengths λ1 and λ2, light, for example, an optical microscope as shown in FIG. 2 can be used. As shown in FIG. 2, irradiation light from a light source 3 of a general optical microscope apparatus 2 equipped with a band pass filter 4 for wavelength selection is applied to a partial region of the wafer with thin film 1 for measuring the film thickness distribution. It can be carried out by irradiation.
　即ち、単一波長λ１、λ２の光を照射する光学顕微鏡装置２を用い、膜厚分布を測定する薄膜付ウェーハ１の照射領域の顕微鏡反射光像を測定し、得られた画像を解析してピクセル毎の反射光強度（あるいは反射率）をそれぞれ求め、これらの反射光強度（あるいは反射率）と、膜厚の絶対値が測定可能な装置（外部装置）により測定された第一薄膜及び第二薄膜の膜厚の絶対値を用いて照射領域内における各薄膜の絶対値の膜厚分布を算出することができる。 That is, using the optical microscope apparatus 2 that irradiates light of single wavelengths λ1 and λ2, the microscope reflected light image of the irradiation region of the thin film-coated wafer 1 for measuring the film thickness distribution is measured, and the obtained image is analyzed. The reflected light intensity (or reflectance) for each pixel is obtained, and the first thin film and the second film measured by an apparatus (external device) capable of measuring the reflected light intensity (or reflectance) and the absolute value of the film thickness. Using the absolute value of the film thickness of the two thin films, the film thickness distribution of the absolute value of each thin film in the irradiation region can be calculated.
　本発明では、第二薄膜の膜厚が変動しても薄膜付ウェーハからの反射率が変動しない波長λ１で第一薄膜の反射光強度分布を測定することと、第一薄膜の膜厚が変動しても薄膜付ウェーハからの反射率が変動しない波長λ２で第二薄膜の反射光強度分布を測定することの少なくともいずれか一方と、外部の装置からの膜厚データを取り込んで前記各反射光強度分布とを組み合わせることで、第一薄膜及び／又は第二薄膜の絶対値で表された膜厚分布を、ミクロな空間分解能で精度よく算出することができる。また、第一薄膜と第二薄膜の膜厚の組み合わせ毎にリファレンス用ウェーハを用いて、キャリブレーションカーブを作成する必要もない。また照射する光の波長を、各々単一波長であるλ１及びλ２の少なくともいずれか一方に限定しているため、膜厚分布を算出するための計算量が少なく、低コストかつ簡便で迅速な測定が可能である。 In the present invention, the reflected light intensity distribution of the first thin film is measured at the wavelength λ1 at which the reflectance from the wafer with the thin film does not vary even if the film thickness of the second thin film varies, and the film thickness of the first thin film varies. Even if the reflected light intensity distribution of the second thin film is measured at a wavelength λ2 at which the reflectance from the wafer with the thin film does not vary even if the film thickness data from the external device is taken in, the reflected light By combining with the intensity distribution, the film thickness distribution represented by the absolute value of the first thin film and / or the second thin film can be accurately calculated with micro spatial resolution. In addition, it is not necessary to create a calibration curve using a reference wafer for each combination of film thicknesses of the first thin film and the second thin film. In addition, since the wavelength of the irradiated light is limited to at least one of λ1 and λ2, which are each a single wavelength, the calculation amount for calculating the film thickness distribution is small, and the measurement is simple, low cost, and low cost. Is possible.
　尚、単一波長λ１、λ２の光を別々に照射して、それぞれの反射光を別々に検出することで、各薄膜毎に膜厚分布を算出することができるが、単一波長λ１、λ２の光を同時に照射し、反射光を各波長成分に分離することによって、各薄膜毎に膜厚分布を算出することも可能である。 The film thickness distribution can be calculated for each thin film by separately irradiating the light of the single wavelengths λ1 and λ2 and separately detecting the reflected light, but the single wavelengths λ1 and λ2 It is also possible to calculate the film thickness distribution for each thin film by simultaneously irradiating the light and separating the reflected light into each wavelength component.
　波長選択にはＯＡフィルター、液晶波長フィルター等を用いることもできる。また、観察視野（照射領域）内の光照射強度が一定になる照射系、及び視野内の感度が一定になる光学検出系を使うことが好ましい。光照射強度が一定とならない照射系においても、参照サンプル面（例えば、シリコン単結晶ウェーハの鏡面研磨面）を基準として、光照射強度を校正することができる。 OA filter, liquid crystal wavelength filter, etc. can also be used for wavelength selection. It is also preferable to use an irradiation system in which the light irradiation intensity in the observation field (irradiation region) is constant and an optical detection system in which the sensitivity in the field is constant. Even in an irradiation system in which the light irradiation intensity is not constant, the light irradiation intensity can be calibrated based on a reference sample surface (for example, a mirror-polished surface of a silicon single crystal wafer).
　このように、本発明の薄膜付ウェーハの膜厚分布の測定方法は、通常の顕微鏡光学系を用いて可視光で行えるため低コストである。また、空間分解能は、顕微鏡の倍率を変えることで、照射光の波長程度から１００［μｍ］程度まで自由に選ぶことが可能である。 As described above, the method for measuring the film thickness distribution of the wafer with a thin film according to the present invention is low in cost since it can be performed with visible light using a normal microscope optical system. The spatial resolution can be freely selected from about the wavelength of the irradiation light to about 100 [μm] by changing the magnification of the microscope.
　また、ピクセルの一辺のサイズを、上記のように求めて照射する波長λ１又はλ２の１／２以上１００［μｍ］以下とすることが好ましい。このようなピクセルサイズであれば、焦点が結びにくくなる恐れがなく、薄膜付ウェーハの薄膜の膜厚分布をより正確に高い空間分解能で算出することができる。 Further, it is preferable that the size of one side of the pixel is set to 1/2 or more and 100 [μm] or less of the wavelength λ1 or λ2 to be irradiated as described above. With such a pixel size, there is no fear that the focus is difficult to be set, and the film thickness distribution of the thin film of the wafer with a thin film can be calculated more accurately with high spatial resolution.
　さらに、上記照射領域を薄膜付ウェーハ面内の複数箇所に設定し、照射領域における反射光強度分布の測定を複数箇所で行うことで、ウェーハ全面の膜厚分布の測定も可能である。ウェーハ全面の測定であっても、測定波長をそれぞれの薄膜に対して一波長に限定しているため（第一薄膜と第二薄膜の両方の膜厚分布を測定する場合であっても、合計で二波長）、計算量が少なく低コストで迅速な測定が可能である。 Furthermore, the film thickness distribution of the entire wafer surface can be measured by setting the irradiation region at a plurality of locations on the wafer surface with a thin film and measuring the reflected light intensity distribution in the irradiation region at a plurality of locations. Even when measuring the entire surface of the wafer, the measurement wavelength is limited to one wavelength for each thin film (even if the film thickness distribution of both the first thin film and the second thin film is measured) 2 wavelengths), and requires a small amount of calculation and can be measured quickly at low cost.
　尚、ＳＯＩウェーハを製造した後に、設定値に近い膜厚が得られているかについて、一旦、従来の膜厚測定方法（分光エリプソ法、反射分光法など）によって大まかに膜厚を確認した後、本発明による詳細な膜厚分布（ミクロな膜厚分布）の測定を行うこともできる。 In addition, after manufacturing an SOI wafer, after confirming a film thickness roughly by the conventional film thickness measuring method (spectral ellipso method, reflection spectroscopy, etc.) once the film thickness close to a set value is obtained, The detailed film thickness distribution (micro film thickness distribution) according to the present invention can also be measured.
　また、本発明の薄膜付ウェーハの膜厚分布の測定方法で光を照射する領域を、顕微鏡の倍率や視野範囲を調整するなどして、デバイス製造工程のリソグラフィー露光サイトに一致させることもできる。これにより、デバイス製造工程で有効に活用しうる薄膜の膜厚分布を算出することができる。デバイス製造工程のリソグラフィー露光時にステッパーで使用されるサイトは、例えば、２６［ｍｍ］×８［ｍｍ］程度のサイズであるため、顕微鏡の倍率や視野範囲を調整することによってリソグラフィー露光サイトに一致させることができる。 Further, the region irradiated with light by the method for measuring the film thickness distribution of the wafer with a thin film of the present invention can be matched with the lithography exposure site of the device manufacturing process by adjusting the magnification and field of view of the microscope. Thereby, the film thickness distribution of the thin film that can be effectively used in the device manufacturing process can be calculated. The site used by the stepper at the time of lithography exposure in the device manufacturing process is, for example, about 26 [mm] × 8 [mm] in size, so that it is matched with the lithography exposure site by adjusting the magnification and field of view of the microscope. be able to.
　尚、本明細書において第一薄膜や第二薄膜等の薄膜は、基板上に形成された膜であって、その膜を透過した照射光が下地（基板表面又は他の膜）との界面で反射し、その反射光を薄膜の表面側から検出することのできる膜厚を有する膜である。 In this specification, the thin film such as the first thin film and the second thin film is a film formed on the substrate, and the irradiation light transmitted through the film is at the interface with the base (substrate surface or other film). The film has a film thickness that allows reflection and detection of the reflected light from the surface side of the thin film.
　以上に本発明の薄膜付ウェーハの膜厚分布の測定方法について説明したが、前述したように、Ｔ１、Ｔ２、ｔの値は上記値に限定されるものではない。そこで以下には、波長λ１及びλ２の決定にあたり、設定膜厚Ｔ１、Ｔ２が他の値の場合（（１）ＳＯＩ層＝１０．５［ｎｍ］、ＢＯＸ層＝２０［ｎｍ］、（２）ＳＯＩ層＝１０［ｎｍ］、ＢＯＸ層＝１５［ｎｍ］の場合）について以下に示す。 The method for measuring the film thickness distribution of the wafer with a thin film according to the present invention has been described above. However, as described above, the values of T1, T2, and t are not limited to the above values. Therefore, in the following, in determining the wavelengths λ1 and λ2, when the set film thicknesses T1 and T2 have other values ((1) SOI layer = 10.5 [nm], BOX layer = 20 [nm], (2) (When SOI layer = 10 [nm], BOX layer = 15 [nm])
［ＳＯＩ層＝１０．５［ｎｍ］、ＢＯＸ層＝２０［ｎｍ］の場合］
　測定対象のＳＯＩウェーハの可視光の波長以上の波長領域の光に対する反射率の波長依存性を示すプロファイルＰ１をシミュレーションにより算出する（図４（Ａ）、（Ｂ）参照）。
　ＳＯＩ層の設定膜厚１０．５［ｎｍ］より１［ｎｍ］だけ厚いＳＯＩ層を有するＳＯＩウェーハの可視光以上の波長領域の光に対する反射率の波長依存性を示すプロファイルＰ２１をシミュレーションにより算出する（図４（Ａ）参照）。 [When SOI layer = 10.5 [nm], BOX layer = 20 [nm]]
A profile P1 indicating the wavelength dependence of the reflectance with respect to light in a wavelength region equal to or larger than the wavelength of visible light of the SOI wafer to be measured is calculated by simulation (see FIGS. 4A and 4B).
A profile P21 indicating the wavelength dependence of the reflectance with respect to light in a wavelength region equal to or greater than the visible light of an SOI wafer having an SOI layer thicker than the set thickness 10.5 [nm] of the SOI layer by 1 [nm] is calculated by simulation. (See FIG. 4A).
　ＢＯＸ層の設定膜厚２０［ｎｍ］より１［ｎｍ］だけ厚いＢＯＸ層を有するＳＯＩウェーハの可視光以上の波長領域の光に対する反射率の波長依存性を示すプロファイルＰ２２をシミュレーションにより算出する（図４（Ｂ）参照）。 A profile P22 indicating the wavelength dependence of the reflectance with respect to light in the wavelength region of visible light or higher of an SOI wafer having a BOX layer thicker by 1 [nm] than the set film thickness 20 [nm] of the BOX layer is calculated by simulation (FIG. 4 (B)).
　算出した両方のプロファイルＰ１、Ｐ２１の差のプロファイルＰ３１（＝Ｐ２１－Ｐ１）、及び、算出した両方のプロファイルＰ１、Ｐ２２の差のプロファイルＰ３２（＝Ｐ２２－Ｐ１）を算出し、該算出した差のプロファイルＰ３１、Ｐ３２がゼロとなるときの波長５４２［ｎｍ］、４７６［ｎｍ］をそれぞれλ１及びλ２と決定する（図４（Ｃ）参照）。 A difference profile P31 (= P21−P1) between both the calculated profiles P1 and P21 and a difference profile P32 (= P22−P1) between both the calculated profiles P1 and P22 are calculated. The wavelengths 542 [nm] and 476 [nm] when the profiles P31 and P32 become zero are determined as λ1 and λ2, respectively (see FIG. 4C).
［ＳＯＩ層＝１０［ｎｍ］、ＢＯＸ層＝１５［ｎｍ］の場合］
　測定対象のＳＯＩウェーハの可視光の波長以上の波長領域の光に対する反射率の波長依存性を示すプロファイルＰ１をシミュレーションにより算出する（図５（Ａ）、（Ｂ）参照）。 [When SOI layer = 10 [nm], BOX layer = 15 [nm]]
A profile P1 indicating the wavelength dependence of the reflectance with respect to light in a wavelength region equal to or larger than the wavelength of visible light of the SOI wafer to be measured is calculated by simulation (see FIGS. 5A and 5B).
　ＳＯＩ層の設定膜厚１０［ｎｍ］より１［ｎｍ］だけ厚いＳＯＩ層を有するＳＯＩウェーハの可視光以上の波長領域の光に対する反射率の波長依存性を示すプロファイルＰ２１をシミュレーションにより算出する（図５（Ａ）参照）。 A profile P21 indicating the wavelength dependence of the reflectance with respect to light in a wavelength region of visible light or higher of an SOI wafer having an SOI layer thicker than the set thickness 10 [nm] of the SOI layer by 1 [nm] is calculated by simulation (FIG. 5 (A)).
　ＢＯＸ層の設定膜厚１５［ｎｍ］より１［ｎｍ］だけ厚いＢＯＸ層を有するＳＯＩウェーハの可視光以上の波長領域の光に対する反射率の波長依存性を示すプロファイルＰ２２をシミュレーションにより算出する（図５（Ｂ）参照）。 A profile P22 indicating the wavelength dependence of the reflectance with respect to light in the wavelength region of visible light or higher of an SOI wafer having a BOX layer thicker than the set film thickness 15 [nm] of the BOX layer by 1 [nm] is calculated by simulation (FIG. 5 (B)).
　算出された両方のプロファイルＰ１、Ｐ２１の差のプロファイルＰ３１（＝Ｐ２１－Ｐ１）、及び、算出された両方のプロファイルＰ１、Ｐ２２の差のプロファイルＰ３２（＝Ｐ２２－Ｐ１）を算出し、該算出した差のプロファイルＰ３１、Ｐ３２がゼロとなるときの波長５０２［ｎｍ］、４３７［ｎｍ］をそれぞれλ１、λ２と決定する（図５（Ｃ）参照）。 A difference profile P31 (= P21−P1) between both calculated profiles P1 and P21 and a difference profile P32 (= P22−P1) between both calculated profiles P1 and P22 are calculated and calculated. Wavelengths 502 [nm] and 437 [nm] when the difference profiles P31 and P32 become zero are determined as λ1 and λ2, respectively (see FIG. 5C).
　そして上記のようにλ１、λ２を求めた後は、図１のＦ～Ｉと同様の工程を行い、ＢＯＸ層及びＳＯＩ層の膜厚分布を求めることができる。 Then, after obtaining λ1 and λ2 as described above, the same steps as FI to I in FIG. 1 can be performed to obtain the film thickness distribution of the BOX layer and the SOI layer.
　尚、λ１、λ２を求めるにあたり、ｔ［ｎｍ］だけ厚くする場合について説明してきたが、逆に、ｔ［ｎｍ］だけ薄くしてシミュレーションをすることにより求めることもできる。 In addition, in the case of obtaining λ1 and λ2, the case of increasing the thickness by t [nm] has been described, but conversely, it can also be obtained by performing the simulation by reducing the thickness by t [nm].
　以下、実施例及び比較例を示して本発明をより具体的に説明するが、本発明はこれらに限定されるものではない。 Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these.
（実施例）
　測定対象としてＳＯＩ層膜厚が１２［ｎｍ］、ＢＯＸ層膜厚が２５［ｎｍ］のＳＯＩウェーハ（直径３００［ｍｍ］）を用意し、このＳＯＩウェーハを本発明の測定方法によって膜厚分布測定を行った。この際、ＳＯＩ層とＢＯＸ層の膜厚の絶対値の膜厚測定を行う装置として、ＡＤＥ社製Ａｃｕｍａｐ（測定ビーム径：約３００μｍ）を使用した。 (Example)
An SOI wafer (diameter 300 [mm]) having an SOI layer thickness of 12 [nm] and a BOX layer thickness of 25 [nm] is prepared as a measurement object, and this SOI wafer is measured for film thickness distribution by the measurement method of the present invention. Went. At this time, Acumap (measurement beam diameter: about 300 μm) manufactured by ADE was used as an apparatus for measuring the film thickness of the absolute values of the SOI layer and the BOX layer.
　図１に示した工程のフローに従い、設定膜厚がＳＯＩ層＝１２［ｎｍ］、ＢＯＸ層＝２５［ｎｍ］のＳＯＩウェーハのプロファイルＰ１をシミュレーションにより算出した。次いで同じくシミュレーションにより、このＳＯＩウェーハのＳＯＩ層が１［ｎｍ］厚くなった場合のプロファイルＰ２１を算出した。そしてＰ１とＰ２１から、差のプロファイルＰ３１（＝Ｐ２１－Ｐ１）を算出し、Ｐ３１がゼロになる波長λ１を取得した。ここでは、λ１は６１５［ｎｍ］であった。 In accordance with the process flow shown in FIG. 1, a profile P1 of an SOI wafer having a set film thickness of SOI layer = 12 [nm] and BOX layer = 25 [nm] was calculated by simulation. Next, similarly, the profile P21 when the SOI layer of the SOI wafer becomes 1 [nm] thick was calculated by simulation. Then, a difference profile P31 (= P21−P1) is calculated from P1 and P21, and a wavelength λ1 at which P31 becomes zero is obtained. Here, λ1 was 615 [nm].
　さらに、上記のＳＯＩウェーハのＢＯＸ層が１［ｎｍ］厚くなった場合のプロファイルＰ２２をシミュレーションにより算出した。Ｐ１とＰ２２から、差のプロファイルＰ３２（＝Ｐ２２－Ｐ１）を算出し、Ｐ３２がゼロになる波長λ２を取得した。ここでは、λ２は５３０［ｎｍ］であった。すなわち、図３に示すグラフと同様の結果（λ１、λ２）を得た。 Furthermore, a profile P22 when the BOX layer of the SOI wafer is 1 [nm] thick was calculated by simulation. A difference profile P32 (= P22−P1) was calculated from P1 and P22, and a wavelength λ2 at which P32 becomes zero was obtained. Here, λ2 was 530 [nm]. That is, the same results (λ1, λ2) as the graph shown in FIG. 3 were obtained.
　これらの結果に基づき、５３０［ｎｍ］の波長λ２の光を使って、ＳＯＩウェーハのＳＯＩ層の外周領域約３ｍｍを、ピクセルサイズ２．５６［μｍ］にてウェーハ中心方向からウェーハ外周方向に向けてテラス部（ＳＯＩ層のない最外周部）にわたるまで、反射光強度測定を行った。
　図６（Ａ）の上図は、反射光強度測定を行ったＳＯＩ層の外周領域の顕微鏡像を示したものである。白線で囲まれた長方形領域が反射光強度を測定した領域であり、その測定領域内の微小な凹凸を示す波線は反射光強度の測定結果を示している。その波線の縦軸目盛を拡大して表記したグラフが図６（Ａ）の下図である。 Based on these results, using the light of wavelength λ2 of 530 [nm], the outer peripheral area of the SOI layer of the SOI wafer is directed from the wafer center direction to the wafer outer periphery direction at a pixel size of 2.56 [μm]. The reflected light intensity was measured over the terrace (the outermost periphery without the SOI layer).
The upper diagram in FIG. 6A shows a microscopic image of the outer peripheral region of the SOI layer for which the reflected light intensity was measured. A rectangular area surrounded by a white line is an area where the reflected light intensity is measured, and a wavy line indicating minute irregularities in the measurement area indicates a measurement result of the reflected light intensity. A graph in which the vertical scale of the wavy line is enlarged is shown in the lower part of FIG.
　図６（Ｂ）は、図６（Ａ）の下図の点線で囲まれた領域（約３００μｍ）の横軸を拡大して表記したものであり、約３００μｍ幅の直線領域における各ピクセルの反射光強度分布（すなわち、約３００μｍ幅の直線領域におけるＳＯＩ層の相対的な膜厚分布に相当）を示している。縦軸は反射光強度、横軸は測定領域内の位置を示している。 FIG. 6B is an enlarged view of the horizontal axis of the region (about 300 μm) surrounded by the dotted line in the lower diagram of FIG. 6A, and the reflected light of each pixel in the linear region having a width of about 300 μm. The intensity distribution (that is, equivalent to the relative film thickness distribution of the SOI layer in a linear region having a width of about 300 μm) is shown. The vertical axis represents the reflected light intensity, and the horizontal axis represents the position in the measurement region.
　次に、ＳＯＩ層とＢＯＸ層の膜厚の絶対値の膜厚測定を行う装置（ここでは、ＡＤＥ社製Ａｃｕｍａｐ）の測定ビーム径に合わせて、この直線領域を直径とする円形領域（直径約３００μｍ）の各ピクセル毎の反射光強度を求めた（平均反射光強度Ｒｍ＝３２４０．１２）。 Next, in accordance with the measurement beam diameter of an apparatus for measuring the absolute thickness of the SOI layer and the BOX layer (here, Acumap manufactured by ADE), a circular region having a diameter of this linear region (diameter of about 300 μm) was determined for each pixel (average reflected light intensity Rm = 3240.12).
　同様に、６１５［ｎｍ］の波長λ１の光を使って、上記と同一領域（直径約３００μｍの円形領域）における各ピクセルの反射光強度を測定した（平均反射光強度Ｒｍ＝３０３６．２３）。尚、図７（Ｂ）は、図６（Ｂ）と同様に、直径約３００μｍの円形領域のうちの約３００μｍ幅の直線領域における各ピクセルの反射光強度分布（すなわち、約３００μｍ幅の直線領域におけるＢＯＸ層の相対的な膜厚分布に相当）を示している。 Similarly, using the light of wavelength λ1 of 615 [nm], the reflected light intensity of each pixel in the same area (circular area having a diameter of about 300 μm) was measured (average reflected light intensity Rm = 3036.23). 7B is similar to FIG. 6B, the reflected light intensity distribution of each pixel in a linear region having a width of about 300 μm in a circular region having a diameter of about 300 μm (that is, a linear region having a width of about 300 μm). Corresponds to the relative film thickness distribution of the BOX layer).
　一方、ＡＤＥ社製Ａｃｕｍａｐにより、上記の反射光強度を測定した領域（直径約３００μｍの円形領域）とほぼ一致する領域のＳＯＩ層とＢＯＸ層の膜厚の絶対値を測定したところ、それぞれ、１２．３３ｎｍ、２４．９５ｎｍであった。これらの絶対値と、上記円形領域の各ピクセルの反射光強度を用い、前述の式（１）を用いた算出法により、その領域のＳＯＩ層とＢＯＸ層の膜厚の絶対値の膜厚分布を算出した。 On the other hand, when the absolute values of the thicknesses of the SOI layer and the BOX layer in the region substantially coincident with the region where the reflected light intensity was measured (circular region having a diameter of about 300 μm) were measured by Acumap manufactured by ADE, respectively, .33 nm and 24.95 nm. Using these absolute values and the reflected light intensity of each pixel in the circular region, the thickness distribution of the absolute values of the SOI layer and BOX layer in that region is calculated by the above-described equation (1). Was calculated.
　図６（Ｃ）は、図６（Ａ）の一部分におけるＳＯＩ層の膜厚分布を示すグラフであり、図６（Ｂ）の結果と、測定領域に含まれるＳＯＩ層の膜厚の平均値である１２．３３ｎｍとから算出されたものである。図６（Ｃ）からわかるように、ＳＯＩ層の膜厚分布が絶対値で求められた。 FIG. 6C is a graph showing the thickness distribution of the SOI layer in a part of FIG. 6A, and shows the result of FIG. 6B and the average value of the thickness of the SOI layer included in the measurement region. It is calculated from a certain 12.33 nm. As can be seen from FIG. 6C, the thickness distribution of the SOI layer was obtained as an absolute value.
　図７（Ｃ）は、図７（Ａ）の一部分におけるＢＯＸ層の膜厚分布を示すグラフであり、図７（Ｂ）の結果と、測定領域に含まれるＢＯＸ層の膜厚の平均値である２４．９５ｎｍとから算出されたものである。図７（Ｃ）からわかるように、ＢＯＸ層の膜厚分布が絶対値で求められた。 FIG. 7C is a graph showing the film thickness distribution of the BOX layer in a part of FIG. 7A, and shows the result of FIG. 7B and the average value of the film thickness of the BOX layer included in the measurement region. It is calculated from a certain 24.95 nm. As can be seen from FIG. 7C, the thickness distribution of the BOX layer was obtained as an absolute value.
　また、測定領域中のＳＯＩ層及びＢＯＸ層の膜厚の平均値、最大値、最小値、Ｐ－Ｖ値（すなわち、最大値と最小値の差）、標準偏差を以下の表１に示した。 Table 1 below shows the average value, maximum value, minimum value, PV value (that is, the difference between the maximum value and minimum value), and standard deviation of the film thickness of the SOI layer and BOX layer in the measurement region. .
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　以上のように、従来の膜厚測定方法（ＡＤＥ社製Ａｃｕｍａｐ）では、直径約３００μｍの測定ビーム径のスポット１点の平均値としてのみ測定可能であったＳＯＩ層及びＢＯＸ層の膜厚の絶対値が、本発明の方法を用いることにより、μｍオーダーの高い空間分解能で、精度よく膜厚分布の測定が可能となることがわかった。 As described above, with the conventional film thickness measurement method (Acumap manufactured by ADE), the absolute values of the film thickness of the SOI layer and the BOX layer, which could be measured only as an average value of one spot having a measurement beam diameter of about 300 μm in diameter. It was found that by using the method of the present invention, the film thickness distribution can be accurately measured with a high spatial resolution on the order of μm.
　なお、本発明は、上記実施形態に限定されるものではない。上記実施形態は、例示であり、本発明の特許請求の範囲に記載された技術的思想と実質的に同一な構成を有し、同様な作用効果を奏するものは、いかなるものであっても本発明の技術的範囲に包含される。 Note that the present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

Claims (9)

  1. 　基板の表面上に形成された第一薄膜と、該第一薄膜の表面上に形成された第二薄膜とを有する薄膜付ウェーハの前記第一薄膜及び第二薄膜の少なくともいずれか一方の膜厚分布を測定する薄膜付ウェーハの膜厚分布の測定方法であって、
    　前記測定対象の薄膜付ウェーハの可視光の波長以上の波長領域の光に対する反射率の波長依存性を示すプロファイルＰ１をシミュレーションにより算出する工程を有し、
    　前記測定対象の薄膜付ウェーハの前記第二薄膜の設定膜厚Ｔ２よりｔ［ｎｍ］だけ薄い、又は厚い第二薄膜を有する薄膜付ウェーハの可視光以上の波長領域の光に対する反射率の波長依存性を示すプロファイルＰ２１をシミュレーションにより算出するサブステップと、前記算出した両方のプロファイルＰ１、Ｐ２１の差のプロファイルＰ３１（＝Ｐ２１－Ｐ１）を算出し、該算出した差のプロファイルＰ３１がゼロとなるときの波長λ１を求めるサブステップとにより、前記波長λ１を求める工程と、
    　前記測定対象の薄膜付ウェーハの前記第一薄膜の設定膜厚Ｔ１よりｔ［ｎｍ］だけ薄い、又は厚い第一薄膜を有する薄膜付ウェーハの可視光以上の波長領域の光に対する反射率の波長依存性を示すプロファイルＰ２２をシミュレーションにより算出するサブステップと、前記算出した両方のプロファイルＰ１、Ｐ２２の差のプロファイルＰ３２（＝Ｐ２２－Ｐ１）を算出し、該算出した差のプロファイルＰ３２がゼロとなるときの波長λ２を求めるサブステップとにより、前記波長λ２を求める工程と、
    　のうち、少なくともいずれか一方の工程を有し、
    　前記測定対象の薄膜付ウェーハ表面の一部領域である照射領域に対して、単一波長である前記波長λ１及び波長λ２の少なくともいずれか一方の光を照射する工程と、
    　前記照射領域からの反射光を前記波長λ１及び波長λ２の少なくともいずれか一方に対して検出して前記照射領域を多数に分割したピクセル毎の反射光強度を測定することによって、前記照射領域内の前記波長λ１及び波長λ２の少なくともいずれか一方に対する反射光強度分布を求める工程と、
    　前記波長λ１に対する反射光強度分布から前記照射領域内における前記第一薄膜の相対値で表された膜厚分布を算出することと、前記波長λ２に対する反射光強度分布から前記照射領域内における前記第二薄膜の相対値で表された膜厚分布を算出することの少なくともいずれか一方を行う工程と、
    　前記第一薄膜及び前記第二薄膜の膜厚の少なくともいずれか一方の絶対値を測定可能な膜厚測定装置を用いて、前記照射領域内の前記第一薄膜及び前記第二薄膜の少なくともいずれか一方の膜厚の絶対値を測定する工程と、
    　該測定された膜厚の絶対値と、前記第一薄膜の相対値で表された膜厚分布及び前記第二薄膜の相対値で表された膜厚分布の少なくともいずれか一方に基づいて、前記照射領域内の前記第一薄膜の絶対値で表された膜厚分布及び前記照射領域内の前記第二薄膜の絶対値で表された膜厚分布の少なくともいずれか一方を算出する工程と、
    　を有することを特徴とする薄膜付ウェーハの膜厚分布の測定方法。     Film thickness of at least one of the first thin film and the second thin film of a wafer with a thin film having a first thin film formed on the surface of the substrate and a second thin film formed on the surface of the first thin film A method for measuring the film thickness distribution of a wafer with a thin film for measuring the distribution,
    A step of calculating by simulation a profile P1 indicating the wavelength dependence of the reflectance with respect to light in a wavelength region equal to or greater than the wavelength of visible light of the wafer with a thin film to be measured;
    Wavelength dependence of reflectance with respect to light in a wavelength region greater than or equal to visible light of a wafer with a thin film having a second thin film that is thinner or thicker than the set film thickness T2 of the second thin film of the wafer with the thin film to be measured. The sub-step of calculating the profile P21 indicating the characteristics by simulation and the difference profile P31 (= P21−P1) between the two calculated profiles P1 and P21, and the calculated difference profile P31 is zero A step of determining the wavelength λ1 by a sub-step of determining the wavelength λ1 of
    Wavelength dependence of reflectance for light in a wavelength region greater than or equal to visible light of a wafer with a thin film having a first thin film that is thinner or thicker than the set film thickness T1 of the first thin film of the wafer with a thin film to be measured A sub-step of calculating a profile P22 indicating the characteristics by simulation and a difference profile P32 (= P22−P1) between the two calculated profiles P1 and P22, and when the calculated difference profile P32 becomes zero A step of determining the wavelength λ2 by a sub-step of determining the wavelength λ2 of
    At least one of the steps,
    Irradiating at least one of the wavelengths λ1 and λ2 with a single wavelength to an irradiation region that is a partial region of the surface of the wafer with a thin film to be measured;
    By detecting the reflected light from the irradiation region with respect to at least one of the wavelength λ1 and the wavelength λ2 and measuring the reflected light intensity for each pixel obtained by dividing the irradiation region into a large number, Obtaining a reflected light intensity distribution for at least one of the wavelengths λ1 and λ2,
    Calculating a film thickness distribution represented by a relative value of the first thin film in the irradiation region from the reflected light intensity distribution with respect to the wavelength λ1, and calculating the film thickness distribution in the irradiation region from the reflected light intensity distribution with respect to the wavelength λ2. Performing at least one of calculating the film thickness distribution represented by the relative value of the two thin films;
    Using a film thickness measuring device capable of measuring an absolute value of at least one of the film thicknesses of the first thin film and the second thin film, at least one of the first thin film and the second thin film in the irradiation region Measuring the absolute value of one film thickness;
    Based on at least one of the absolute value of the measured film thickness, the film thickness distribution represented by the relative value of the first thin film, and the film thickness distribution represented by the relative value of the second thin film, Calculating at least one of the film thickness distribution represented by the absolute value of the first thin film in the irradiation region and the film thickness distribution represented by the absolute value of the second thin film in the irradiation region;
    A method for measuring a film thickness distribution of a wafer with a thin film, comprising:
  2. 　前記測定対象の薄膜付ウェーハがＳＯＩウェーハであり、前記第一薄膜が埋め込み酸化膜層であり、前記第二薄膜がシリコン単結晶からなるＳＯＩ層であることを特徴とする請求項１に記載の薄膜付ウェーハの膜厚分布の測定方法。 The wafer with a thin film to be measured is an SOI wafer, the first thin film is a buried oxide film layer, and the second thin film is an SOI layer made of a silicon single crystal. A method for measuring the film thickness distribution of a wafer with a thin film.
  3. 　前記波長λ１及び波長λ２の少なくともいずれか一方は、可視光波長から選択された単一の波長であることを特徴とする請求項１又は請求項２に記載の薄膜付ウェーハの膜厚分布の測定方法。 The measurement of the film thickness distribution of the wafer with a thin film according to claim 1 or 2, wherein at least one of the wavelengths λ1 and λ2 is a single wavelength selected from visible light wavelengths. Method.
  4. 　前記ピクセルの一辺のサイズを、前記波長λ１又は波長λ２の１／２以上１００［μｍ］以下とすることを特徴とする請求項１から請求項３のいずれか一項に記載の薄膜付ウェーハの膜厚分布の測定方法。 4. The thin film-coated wafer according to claim 1, wherein a size of one side of the pixel is not less than ½ and 100 [μm] of the wavelength λ <b> 1 or the wavelength λ <b> 2. Measuring method of film thickness distribution.
  5. 　前記照射領域をデバイス製造工程のリソグラフィー露光サイトに一致させることを特徴とする請求項１から請求項４のいずれか一項に記載の薄膜付ウェーハの膜厚分布の測定方法。 The method for measuring a film thickness distribution of a thin film-attached wafer according to any one of claims 1 to 4, wherein the irradiation region is matched with a lithography exposure site in a device manufacturing process.
  6. 　前記第一薄膜及び第二薄膜の少なくともいずれか一方の前記相対値で表された膜厚分布を算出する前記照射領域を、前記薄膜付ウェーハの面内の複数箇所に設定することにより、全面における絶対値で表された膜厚分布を求めることを特徴とする請求項１から請求項５のいずれか一項に記載の薄膜付ウェーハの膜厚分布の測定方法。 By setting the irradiation region for calculating the film thickness distribution represented by the relative value of at least one of the first thin film and the second thin film at a plurality of locations within the surface of the wafer with the thin film, 6. The method for measuring a film thickness distribution of a thin film-attached wafer according to claim 1, wherein a film thickness distribution expressed by an absolute value is obtained.
  7. 　前記膜厚測定装置が、分光エリプソ法又は反射分光法を使用した装置であることを特徴とする請求項１から請求項６のいずれか一項に記載の薄膜付ウェーハの膜厚分布の測定方法。 The method for measuring a film thickness distribution of a thin film-attached wafer according to any one of claims 1 to 6, wherein the film thickness measuring apparatus is an apparatus using a spectroscopic ellipso method or a reflection spectroscopic method. .
  8. 　前記波長λ１及び前記波長λ２のうち、前記波長λ１のみを求めることによって、前記第一薄膜の絶対値で表された膜厚分布のみを算出することを特徴とする請求項１から請求項７のいずれか一項に記載の薄膜付ウェーハの膜厚分布の測定方法。 8. The film thickness distribution represented by the absolute value of the first thin film is calculated by obtaining only the wavelength λ <b> 1 out of the wavelength λ <b> 1 and the wavelength λ <b> 2. The measuring method of the film thickness distribution of the wafer with a thin film as described in any one.
  9. 　前記波長λ１及び前記波長λ２のうち、前記波長λ２のみを求めることによって、前記第二薄膜の絶対値で表された膜厚分布のみを算出することを特徴とする請求項１から請求項７のいずれか一項に記載の薄膜付ウェーハの膜厚分布の測定方法。 8. The film thickness distribution represented by the absolute value of the second thin film is calculated by obtaining only the wavelength λ 2 out of the wavelengths λ 1 and λ 2. 8. The measuring method of the film thickness distribution of the wafer with a thin film as described in any one.
PCT/JP2016/005126 2016-01-14 2016-12-14 Method for measuring film thickness distribution of wafer with thin film WO2017122248A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2016005617A JP2017125782A (en) 2016-01-14 2016-01-14 Method for measuring film thickness distribution of wafer with thin film
JP2016-005617 2016-01-14

Publications (1)

Publication Number Publication Date
WO2017122248A1 true WO2017122248A1 (en) 2017-07-20

Family

ID=59312004

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2016/005126 WO2017122248A1 (en) 2016-01-14 2016-12-14 Method for measuring film thickness distribution of wafer with thin film

Country Status (3)

Country Link
JP (1) JP2017125782A (en)
TW (1) TW201736799A (en)
WO (1) WO2017122248A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021065499A1 (en) * 2019-10-03 2021-04-08 信越半導体株式会社 Method for measuring film thickness distribution of wafer having thin film

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20200033723A1 (en) * 2018-07-30 2020-01-30 Taiwan Semiconductor Manufacturing Co., Ltd. Semiconductor Manufacturing Apparatus and Method Thereof
WO2022172532A1 (en) * 2021-02-09 2022-08-18 浜松ホトニクス株式会社 Film thickness measuring device and film thickness measuring method

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH1076464A (en) * 1996-08-30 1998-03-24 Canon Inc Polishing method and polishing device using therewith
JP2011249621A (en) * 2010-05-28 2011-12-08 Shin Etsu Handotai Co Ltd Evaluation method of wafer with thin film
JP2013137205A (en) * 2011-12-28 2013-07-11 Shin Etsu Handotai Co Ltd Film thickness distribution measurement method
JP2016114506A (en) * 2014-12-16 2016-06-23 信越半導体株式会社 Evaluation method of wafer with thin film

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH1076464A (en) * 1996-08-30 1998-03-24 Canon Inc Polishing method and polishing device using therewith
JP2011249621A (en) * 2010-05-28 2011-12-08 Shin Etsu Handotai Co Ltd Evaluation method of wafer with thin film
JP2013137205A (en) * 2011-12-28 2013-07-11 Shin Etsu Handotai Co Ltd Film thickness distribution measurement method
JP2016114506A (en) * 2014-12-16 2016-06-23 信越半導体株式会社 Evaluation method of wafer with thin film

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021065499A1 (en) * 2019-10-03 2021-04-08 信越半導体株式会社 Method for measuring film thickness distribution of wafer having thin film
JP2021060208A (en) * 2019-10-03 2021-04-15 信越半導体株式会社 Measuring method of film thickness distribution of thin film wafer
JP7160779B2 (en) 2019-10-03 2022-10-25 信越半導体株式会社 Method for measuring film thickness distribution of wafer with thin film
EP4040106A4 (en) * 2019-10-03 2023-11-15 Shin-Etsu Handotai Co., Ltd. Method for measuring film thickness distribution of wafer having thin film
US11965730B2 (en) 2019-10-03 2024-04-23 Shin-Etsu Handotai Co., Ltd. Method for measuring film thickness distribution of wafer with thin films

Also Published As

Publication number Publication date
TW201736799A (en) 2017-10-16
JP2017125782A (en) 2017-07-20

Similar Documents

Publication Publication Date Title
JP5365581B2 (en) Evaluation method of wafer with thin film
CN108463877B (en) System and method for extended infrared spectroscopic ellipsometry
JP5660026B2 (en) Film thickness distribution measurement method
CN110062952B (en) Simultaneous multiple angle spectroscopy
CN110313059A (en) For measuring the method and system of thick film and high aspect ratio structures
TW200938964A (en) Method and apparatus for angular-resolved spectroscopic lithography characterization
TWI673487B (en) Metrology system, metrology apparatus and metrology method
JP6952033B2 (en) Non-contact thermal measurement of VUV optics
WO2017122248A1 (en) Method for measuring film thickness distribution of wafer with thin film
TWI716422B (en) Method and assembly for determining the thickness of a layer in a sample stack
JP6520795B2 (en) Film thickness distribution measurement method
JP5502227B1 (en) Film thickness distribution measurement method
JP2009204313A (en) Apparatus and method for film thickness measurement
JP2016114506A (en) Evaluation method of wafer with thin film
JP5108447B2 (en) Semiconductor surface strain measuring apparatus, method and program
JP7160779B2 (en) Method for measuring film thickness distribution of wafer with thin film
WO2017141299A1 (en) Film-thickness-distribution measuring method
JP2005337927A (en) Film thickness measuring method and film thickness measuring instrument

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 16884852

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 16884852

Country of ref document: EP

Kind code of ref document: A1