JP2010014432A - Film thickness measuring method - Google Patents

Abstract

An object of the present invention is to provide a thin film thickness measurement method capable of measuring a thin film thickness and detecting an abnormal value with high accuracy and in a short time with a simple configuration.
A method of measuring a film thickness of an uppermost layer of an evaluation sample using an X-ray diffractometer, wherein a film thickness reference value of a standard sample is determined using a film thickness measurement method other than the X-ray diffractometer. A reference value measuring step for measuring, a calibration information generating step for generating in advance calibration information 10 in which the characteristic amount detected from the X-ray diffraction intensity distribution of the standard sample and the film thickness reference value are associated, and an evaluation sample A distribution acquisition step S100 for acquiring the X-ray diffraction intensity distribution, a feature amount detection step S101 for detecting a feature amount from the X-ray diffraction intensity distribution acquired in the distribution acquisition step S100, and a detection in the feature amount detection step S101. A film thickness measuring method comprising: a film thickness calculating step S106 for calculating the film thickness of the uppermost layer of the evaluation sample from the measured feature amount and the calibration information 10.
[Selection] Figure 6

Description

  The present invention relates to a film thickness measuring method, and more particularly to a film thickness measuring method for measuring a film thickness of a semiconductor forming a multilayer structure with high speed and high accuracy.

  In recent years, in the manufacture of SOI substrates and MEMS (Micro Electro Mechanical Systems), attention has been focused on semiconductor substrate bonding technology. In this bonding technique, CMOS development using a HOT (Hybrid Crystal Orientation Technology) substrate in which silicon having a crystal plane orientation (100) and silicon having a crystal plane orientation (110) are bonded directly or via an insulating layer is active. It has become. As described above, in the substrate technology in which different materials are formed in a multilayer structure, the film thickness of the multilayer film is an important quality control characteristic.

  Conventionally, as a method for measuring a film thickness, there are a spectral emporometry method and a reflection spectroscopy method. In these methods, the state of reflected light, transmitted light, and refracted light changes depending on the crystal structure and surface state of the thin film, so the wavelength of incident light to the thin film and the refractive index, transmittance, and reflectance of the emitted light It is necessary to calculate a correlation equation and a correlation coefficient from the relationship, and it takes a considerable time to measure the film thickness. Further, when a transmission electron microscope is used, the measurement sample must be destroyed. Furthermore, in the above method, measurement is performed mainly using a light source having a wavelength of 1000 nm or less. However, when measuring a thick film having a measurement target film thickness of 1 μm or more of the multilayer film, the measurement becomes difficult because the absorption coefficient in the visible light region of 770 nm or less is large. A measurement method using the X-ray diffraction method is known for this problem, but since the crystal structure of the thin film has irregularities and is not smooth, an X-ray diffraction intensity capable of obtaining sufficient film thickness measurement accuracy is detected. Therefore, techniques disclosed in Patent Documents 1, 2, and 3 are disclosed.

  In Patent Document 1, in order to obtain a sufficient X-ray diffraction intensity in terms of measurement accuracy, each X-ray diffraction intensity is measured using four types of X-rays, and the measured value is calculated in a complementary manner. A technique that enables a wide range of measurement targets is disclosed. Patent Document 2 discloses a technique in which after a planarization layer is formed on a thin film, the thickness of the thin film including the planarization layer is measured by an X-ray diffraction method, and the thickness of the planarization layer is corrected. Has been. Further, Patent Document 3 discloses a technique for solving a measurement accuracy deficiency caused by a crystal structure by scanning an X-ray detector that detects an X-ray diffraction intensity by a thin film over a predetermined angle range.

Japanese Patent Laid-Open No. 7-27550 JP-A-5-256636 Japanese Patent Laid-Open No. 5-113322

  However, in Patent Document 1, the configuration is complicated in that four types of X-rays are used, and the cost increases. In Patent Document 2, if a planarization layer is formed for film thickness measurement, it becomes impossible to form a film on top of it. In Patent Document 3, since a statistical approximate expression is obtained, a considerable measurement time is required. As described above, these techniques disclosed in the related art require a large cost increase with a complicated configuration, a considerably long film thickness measurement time, and a long measurement time, so that the amount of X-ray irradiation varies. As a result, there is a problem that there is no thin film measurement method that satisfies all of the cost, measurement time, and measurement accuracy for performing film thickness measurement, such that the measurement accuracy decreases.

  The present invention has been made in view of the above problems, and is a film that enables high-speed and high-accuracy thin film thickness measurement with a simple configuration in measuring the film thickness of a thin film on a semiconductor substrate forming a multilayer structure. An object is to provide a thickness measurement method.

  In order to solve the above problems and achieve the object, the film thickness measuring method according to the present invention is configured as follows.

  (1) The film thickness measuring method according to the present invention is a method for measuring the film thickness of the uppermost layer of an evaluation sample having a multilayer film structure using an X-ray diffractometer, and is a film thickness other than the X-ray diffractometer. Using the measurement method, a reference value measuring step for measuring the film thickness reference value of the standard sample, and scanning the X-ray irradiation angle to the standard sample to obtain an X-ray diffraction intensity distribution, and from the X-ray diffraction intensity distribution A calibration information generation step for generating calibration information that associates the detected feature quantity with the film thickness reference value of the standard sample in advance, and an X-ray diffraction intensity distribution by scanning the X-ray irradiation angle on the evaluation sample A distribution acquisition step of acquiring a feature amount, a feature amount detection step of detecting a feature amount from the X-ray diffraction intensity distribution acquired in the distribution acquisition step, a feature amount detected in the feature amount detection step, and the calibration information To the top layer of the evaluation sample Characterized in that a film thickness calculating step of calculating the thickness.

  (2) In the film thickness measurement method described in (1) above, it is desirable that the feature amount is either a maximum value or an integral value of the X-ray diffraction intensity distribution.

  (3) In the film thickness measuring method according to the above (1) or (2), the film thickness reference value is preferably a film thickness measured by either a transmission electron microscope or a spectroscopic emsometry method. .

  (4) In the film thickness measuring method according to (1) to (3), the standard sample is preferably held in the X-ray diffraction apparatus.

  (5) In the film thickness measurement method according to (1) to (4), the standard sample and the evaluation sample are either a HOT (Hybrid Crystal Orientation Technology) substrate or an SOI (Silicon On Insulator) substrate. The uppermost layer preferably has a crystal plane orientation of (100) or (110) of silicon (Si).

  (6) In the film thickness measurement method according to the above (1) to (5), an X-ray intensity before being irradiated on the evaluation sample is detected, and the X-ray intensity is detected in the feature amount detection step. It is desirable to correct the feature amount.

  (7) In the film thickness measuring method according to the above (1) to (6), the film thickness of the uppermost layer is desirably 10 nm or more.

  (8) In the film thickness measurement method according to (2), the evaluation is performed by detecting either an angle half-value width or an angle rising width from the X-ray diffraction intensity distribution of the evaluation sample acquired in the distribution acquisition step. It is desirable to evaluate the crystallinity of the sample.

  Stores calibration information that correlates the characteristic amount determined from the X-ray diffraction intensity distribution of the thin film forming the multilayer structure with the film thickness reference value by a transmission electron microscope (TEM) or spectroscopic emsometry, and measures the film thickness Thin film thickness measurement that enables high-speed and high-accuracy film thickness measurement and abnormal value detection with a simple configuration by calculating the film thickness from the feature value and calibration information that are sometimes obtained from the X-ray diffraction intensity distribution Provide a method.

  Embodiments of a thin film thickness measuring method according to the present invention will be described below with reference to the accompanying drawings.

(First embodiment)
Hereinafter, the film thickness measuring method according to the first embodiment will be described in detail. FIG. 1 is a schematic diagram of an optical system of an X-ray diffraction apparatus 1 according to the first embodiment. The X-ray diffractometer 1 is an apparatus for measuring the film thickness of an evaluation sample formed on a semiconductor substrate, and includes an X-ray source 2, a monochromator 3, a sample 4, a scintillation counter 5, a slit 6, and a slit. 7, an absorber 8, and a sample rotation motor 9.

  The X-ray source 2 is a light source that emits X-rays to the evaluation sample on the substrate. For example, the target of the X-ray generation source uses copper (Cu). The monochromator 3 is a spectroscope that separates X-rays radiated from the X-ray source 2 into a single wavelength. For example, a spectral crystal or the like is used.

  Sample 4 is an evaluation sample to be measured for film thickness. Sample 4 is, for example, silicon (hereinafter referred to as Si) having a multilayered crystal structure, or a semiconductor such as germanium (Ge) or gallium (Ga). In the first embodiment, the embodiment has been described in which Si of crystal plane orientations (110), (220), and (440) is the object of film thickness measurement. The film thickness measurement method according to the first embodiment is more effective when the film thickness of the uppermost layer of the sample 4 is 10 nm or more.

  The sample rotation motor 9 is a drive motor for scanning the irradiation angle of X-rays irradiated on the sample 4. When the X-ray diffraction intensity of the sample 4 is measured, the sample 4 is rotationally driven in the direction A in FIG. 1 so that the X-ray irradiation angle with respect to the sample 4 is scanned over a wide range. By scanning the X-ray irradiation angle on the sample 4 (omega scan), the orientation of the crystal plane orientation of the sample 4 with respect to the X-ray irradiation direction is changed, and data for grasping the X-ray irradiation angle dependency is obtained. . This data is referred to as an X-ray diffraction intensity distribution. Quantifying the X-ray diffraction intensity distribution leads to grasping the crystal structure of the uppermost layer of the sample 4 and measuring the film thickness of the evaluation sample.

  The scintillation counter 5 measures the amount of X-ray radiation in order to detect the X-ray diffraction intensity of the sample 4. The scintillation counter 5 is a detector used to capture weak electric signals such as X-rays. For example, a fluorescent substance that reacts to X-rays and a photoelectron that detects weak photoelectrons generated from the fluorescent substance. And a multiplier.

  The slits 6 and 7 are optical members for irradiating the sample 4 with the X-rays emitted from the X-ray source 2 being focused.

  The absorber 8 has an intensity adjustment function for attenuating X-rays incident on the scintillation counter 5 within an appropriate range in the measurement range before measuring the X-ray diffraction intensity with the scintillation counter 5. In many cases, aluminum foil is used.

  FIG. 2 is a block diagram of the X-ray diffraction apparatus 1 according to the first embodiment. In FIG. 2, the X-ray diffraction apparatus 1 includes a correlation table 10, a correlation unit 11, a data calculation unit 12, a data output unit 13, and a measurement control unit 14 in addition to the above scintillation counter 5. I have.

  The correlation unit 11 manages calibration information described in the correlation table 10, and reads calibration information in which the maximum value of the X-ray diffraction intensity distribution and the film thickness reference value are associated with each other from the correlation table 10. Alternatively, it has a function of generating a correlation table 10 describing calibration information in advance. The generation of the correlation table 10 may be either a configuration in which a measurement operator manually inputs calibration information or a configuration in which an X-ray diffraction intensity distribution of a standard sample serving as a measurement reference is acquired and automatically created.

  The data calculation unit 12 calculates the film thickness of the evaluation sample from the calibration information that associates the maximum value of the X-ray diffraction intensity distribution with the film thickness reference value and the maximum value of the X-ray diffraction intensity distribution input from the scintillation counter 5. It has a numerical calculation function to calculate. As a specific configuration, it mainly includes a CPU (Central Processing Unit) and a ROM (Read Only Memory) storing an arithmetic program.

  The data output unit 13 has a data output function for displaying or printing out the film thickness of the evaluation sample calculated by the data calculation unit 12.

  The measurement control unit 14 has a function of issuing operation instructions to the scintillation counter 5, the correlation unit 11, the data calculation unit 12, and the data output unit 13 to control the operation of the entire X-ray diffraction apparatus 1. A specific configuration mainly includes a CPU (Central Processing Unit), a ROM (Read Only Memory) storing an operation control program, and the like, and is responsible for signal control of each of the above-described main parts. Note that the measurement control unit 14 may substitute for the information reading function and the numerical value calculation function instead of the correlation unit 11 and the data calculation unit 12. In this case, the correlation unit 11 and the data calculation unit 12 are not necessary.

  The correlation table 10 has different crystal structures for calibration information in which the maximum value of the X-ray diffraction intensity distribution of a standard sample is associated with a film thickness reference value by a transmission electron microscope (hereinafter referred to as TEM) or a spectroscopic emsometry method. This is a lookup table stored in advance for each. FIG. 3 is an explanatory diagram showing a storage structure of the correlation table 10 of the X-ray diffraction apparatus 1 according to the first embodiment. Correlation table 10 has data NO. And the maximum value of the X-ray diffraction intensity distribution and the film thickness reference value are provided in the table. The specific storage medium of the correlation table 10 is a DRAM (Direct Random Access Memory) having a predetermined storage capacity, a hard disk, or the like.

  Hereinafter, the correlation table creation method will be described in detail. The X-ray diffraction intensity distribution is acquired by scanning the X-ray irradiation angle on the standard sample, and the maximum value is detected from the X-ray diffraction intensity distribution. On the other hand, the film thickness reference value is measured by using TEM or spectroscopic empometry method. In the case of film thickness measurement by TEM, the film thickness is measured about 10 points on the cross-sectional image of the standard sample, and an average value is obtained so as to reduce the position variation. The spectroscopic emsometry method is a method for measuring the thickness reference value of the standard sample by obtaining the elliptically polarized reflected light by obliquely incident linearly polarized light on the standard sample and analyzing the shape of the elliptically polarized light. .

  The standard sample is, for example, a HOT substrate by direct bonding comprising a top layer (active layer) Si (110) having a thickness of 10 to 5000 nm and a substrate Si (100) having a thickness of 775 nm. Prepare. An X-ray diffraction intensity distribution is collected by the Si (110) crystal plane of the uppermost layer of these substrates and the Si (220) crystal plane or Si (440) crystal plane located in the lower layer. On the other hand, a film thickness reference value by TEM is used for the film thickness. FIG. 4 is a graph showing the relationship between the maximum value of the X-ray diffraction intensity distribution of the uppermost Si crystal plane and the cross-sectional film thickness measured by TEM. In FIG. 4, the horizontal axis represents the maximum value of the X-ray diffraction intensity distribution of each Si crystal plane, and the vertical axis represents the measured cross-sectional film thickness by TEM of the same Si crystal plane. The mark (Δ) indicates data on the condition without an absorber of the Si (440) crystal plane. The mark (◯) indicates data on the condition that there is an absorber on the Si (220) crystal plane. A mark (□) indicates data on the condition of no absorber of the Si (220) crystal plane.

  FIG. 5 is an enlarged graph showing a region having a low X-ray diffraction intensity on the horizontal axis of the graph shown in FIG. As the film thickness of the uppermost layer increases due to X-ray absorption, the slope of the curve changes. However, for a thick evaluation sample having a top layer of 1 μm, for example, if Si (440) crystal plane diffraction in which the X-ray incident angle is large and the X-ray reaches deep into the substrate is used, the film is based on a highly linear curve. Thickness can be calculated and high measurement accuracy can be expected. Further, by providing the absorber 8 in the X-ray optical path, the mark (◯) for the condition with an absorber becomes data obtained by attenuating the mark (□) for the condition without an absorber in the horizontal axis direction of FIG. Some data is overranged in the mark (□) with no absorber 8 condition, but a lot of data is in the graph range with the mark (◯) in condition with the absorber 8. On the other hand, in the crystal plane orientation (440) thin film, since the X-ray diffraction intensity is relatively low even in the absence of the absorber 8, a lot of data is in the range. In this way, the measurement conditions of the film thickness are optimized by selectively using or not using the absorber 8 according to the characteristics of the crystal plane to be measured. In this way, a predetermined number of data is extracted from the graphs of FIGS. 4 and 5 to create the above-described correlation table 10.

  Hereinafter, the film thickness measurement procedure based on the X-ray diffraction intensity will be described in detail. FIG. 6 is a flowchart showing a film thickness measurement procedure according to the first embodiment. First, the correlation unit 11 receives the X-ray diffraction intensity from the scintillation counter 5 and acquires an X-ray diffraction intensity distribution (step S100). The correlation unit 11 detects the maximum value Imax from the X-ray diffraction intensity distribution (step S101). The correlation unit 11 searches the correlation table 10 for the maximum value Imax (step S102). If there is a value that matches the maximum value Imax as a result of the search (step S103: Yes), the correlation unit 11 instructs reading of the film thickness value on the correlation table 10 (step S104).

  On the other hand, if there is no value that matches the maximum value Imax (step S103: No), the correlation unit 11 reads data interpolation values I1 and I2 that satisfy I1 <maximum value Imax <I2 from the values on the correlation table 10, It transmits to the data calculation part 12 (step S105). The data calculation unit 12 calculates the film thickness value D from the data interpolation values I1 and I2 and the maximum value Imax and transmits it to the data output unit 13 (step S106). The data output unit 13 displays or prints out the film thickness value D (step S107).

Regarding the calculation of the film thickness value D in step S106, for example, a conventionally known calculation method such as linear interpolation, least square method, multidimensional regression, or the like can be considered, but the first embodiment can be performed using any method. This does not affect the applicability of the technique of the film thickness measurement method. Here, if linear interpolation is used as a calculation example, the film thickness value D can be calculated according to the following equation (1). However, at the X-ray diffraction intensities I1 and I2, the film thickness reference values on the correlation table 10 are D1 and D2, respectively.
D = (D1-D2) .Imax / (I1-I2) (1)

以下、上述のごとくＸ線回折強度分布の最大値から算出される測定膜厚と、ＴＥＭによる膜厚基準値との測定値を比較すると、表１のようになる。表１は、図４および図５に図示したＳｉ（４４０）結晶面のアブソーバなし条件、Ｓｉ（２２０）結晶面のアブソーバあり条件、Ｓｉ（２２０）結晶面のアブソーバなし条件の３種のデータを表記している。表１に示すように、各結晶面の測定膜厚とＴＥＭによる膜厚基準値の誤差は±３％以下であり、高精度の膜厚測定を可能とすることを実証している。また、上述した膜厚の測定には、複雑な解析が不要であるため１ポイント１０秒以下の短時間で測定可能であり、評価試料の面内１００ポイント測定で約１０分という高速測定を可能とする。

Table 1 below compares the measured film thickness calculated from the maximum value of the X-ray diffraction intensity distribution as described above and the measured film thickness reference value by TEM. Table 1 shows three types of data: the condition without an absorber for the Si (440) crystal plane, the condition with an absorber for the Si (220) crystal plane, and the condition without an absorber for the Si (220) crystal plane shown in FIGS. It is written. As shown in Table 1, the error between the measured film thickness of each crystal plane and the film thickness reference value by TEM is ± 3% or less, demonstrating that highly accurate film thickness measurement is possible. In addition, the above-mentioned film thickness measurement does not require complicated analysis, so it can be measured in a short time of 10 seconds or less for 1 point, and high-speed measurement of about 10 minutes is possible with 100 points measurement on the surface of the evaluation sample. And

  When the evaluation sample has a crystal structure that is relatively free of crystal distortion as used in the above-described correlation table 10 production, the above-described film thickness measurement method enables highly accurate film thickness measurement. However, when there is a stacking fault or the crystal structure has unevenness in a part of the region, an abnormal value may occur in the film thickness measurement. In the first embodiment, the abnormality in the film thickness measurement as described above using either the angle half-value width or the angle rise width of the sample 4 from the X-ray diffraction intensity distribution acquired in step S100 of FIG. It is possible to detect the value.

  Hereinafter, a detailed description will be given of the first embodiment relating to the detection of abnormal values in film thickness measurement. FIG. 7 is a graph illustrating Example 1 relating to detection of abnormal values in film thickness measurement of two different crystal planes. The crystal plane 1 is relatively free of crystal disturbance and has an X-ray diffraction intensity peak at a predetermined angle. On the other hand, the crystal plane 2 has an X-ray diffraction intensity peak smaller than that of the crystal plane 1 because the crystal is more disordered than the crystal plane 1. When the film thickness measurement is performed on the crystal plane 1 and the crystal plane 2 with the maximum value, the crystal plane 2 has an abnormal value different from the actual film thickness. The crystal plane 2 has a half-value width 0.048 that is wider than the angle half-value width 0.043 of the X-ray diffraction intensity distribution of the crystal plane 1. Therefore, in the case of Example 1 shown in FIG. 7, it is more effective as a film thickness measurement method if an abnormal value is detected from the angle half-value width of the X-ray diffraction intensity distribution.

  In addition, a second embodiment related to detection of abnormal values in film thickness measurement will be described in detail. FIG. 8 is a graph illustrating Example 2 relating to detection of abnormal values in film thickness measurement of two different crystal planes. The crystal plane 3 is relatively free of crystal disturbance and has an X-ray diffraction intensity peak at a certain angle. On the other hand, the crystal plane 4 has an X-ray diffraction intensity peak equivalent to that of the crystal plane 1, but the rise to the peak is abrupt. When film thickness measurement is performed on the crystal plane 3 and the crystal plane 4 with the maximum value, the crystal plane 4 has an abnormal value different from the actual film thickness. The crystal plane 4 has a rising width F2 that is narrower than the angular rising width F1 of the X-ray diffraction intensity distribution of the crystal plane 3. Therefore, in the case of Example 2 shown in FIG. 8, if an abnormal value is detected by the angle rising width of the X-ray diffraction intensity distribution, it is more effective as a film thickness measurement method.

  As described above, according to the X-ray diffraction apparatus 1 according to the first embodiment, the film thickness of the evaluation sample having different crystal faces such as the crystal face 1, the crystal face 2, the crystal face 3, or the crystal face 4. In the case of measuring the film thickness, it is possible to detect an abnormal value of the film thickness measurement by detecting either the angle half-value width or the angle rising width from the X-ray diffraction intensity distribution of the evaluation sample. Such an abnormal value detection of the film thickness measurement is effective particularly in a case where a product abnormality is detected in the production line.

  As described above, according to the first embodiment, the correlation table associating the maximum value of the X-ray diffraction intensity distribution by a plurality of standard samples with the film thickness reference value by the TEM or spectroscopic emsometry method is provided. Memorize and detect the maximum value, half-width of angle, or angle rise width from the X-ray diffraction intensity distribution of the evaluation sample, thereby enabling high-speed and high-accuracy film thickness measurement and abnormal value detection with a simple configuration A thickness measurement method is provided.

(Second embodiment)
Hereinafter, the second embodiment will be described in detail. The difference between the second embodiment and the first embodiment is the feature amount stored in the correlation table 15. The correlation table 15 is a look-up table that stores calibration information in which the integrated value of the X-ray diffraction intensity distribution scanned at the X-ray irradiation angle is associated with the film thickness reference value by the TEM. In addition, since it is the same as that of the X-ray-diffraction apparatus concerning 1st Embodiment about components other than the correlation table 15, description is abbreviate | omitted.

  FIG. 9 is a block diagram of the X-ray diffraction apparatus 16 according to the second embodiment. In FIG. 9, the X-ray diffraction apparatus 16 includes a correlation table 15, and other components and their operations are the same as those in the first embodiment, and a description thereof is omitted. FIG. 10 is an explanatory diagram showing the storage structure of the correlation table 15 according to the second embodiment. The correlation table 15 stores, for each different crystal plane, calibration information in which the integral value of the X-ray diffraction intensity distribution of the standard sample is associated with the film thickness reference value by the TEM. The operation of reading data from the correlation table 15 and calculating the film thickness value is the same measurement procedure as that of the X-ray diffraction apparatus 1 according to the first embodiment, and thus the description thereof is omitted.

  First, as an evaluation sample, for example, a HOT substrate (crystal plane 6) by direct bonding composed of an uppermost layer Si (110) having a thickness of about 300 nm and a substrate Si (100) having a thickness of 775 nm is prepared. In the surface layer of about 100 nm, which is the uppermost layer of the HOT substrate, there are many stacking faults inserted when the HOT substrate is formed. When such a sample is measured, distortion occurs in the uppermost layer due to stacking faults, and this disorder of the crystal causes a decrease in the peak of the X-ray diffraction intensity. The HOT substrate was processed at 1200 ° C. for 1 hour in an argon (Ar) atmosphere to prepare a sample from which stacking faults on the crystal plane 6 were removed (crystal plane 5). FIG. 11 is a graph showing an X-ray diffraction intensity distribution obtained by angle scanning in the X-ray diffraction apparatus 16 according to the second embodiment. FIG. 11 shows the relationship between the X-ray irradiation angle and the X-ray diffraction intensity for two types of crystal planes. The crystal plane 5 is relatively free from crystal disturbance and has an X-ray diffraction intensity peak at a certain predetermined angle. On the other hand, the crystal plane 6 has an X-ray diffraction intensity peak smaller than that of the crystal plane 5 because the uppermost layer has more strain than the crystal plane 5. When measuring the film thickness of the crystal plane 5 and the crystal plane 6, the integral values G1 and G2 detected from the X-ray diffraction intensity distribution are used as feature amounts. By adopting the integral value, even when the film thicknesses of the crystal plane 5 and the crystal plane 6 having different crystal structures are measured as shown in FIG. 11, it is possible to measure the film thickness with high accuracy in consideration of the effect of stacking faults. Become.

  As described above, according to the second embodiment, the correlation table of the integral value detected from the X-ray diffraction intensity distribution of a plurality of standard samples and the film thickness reference value by the TEM or spectroscopic emsometry method is stored. By calculating the film thickness value from the integral value detected from the X-ray diffraction intensity distribution of the evaluation sample and the correlation table, high-speed and high-accuracy film thickness measurement that takes into account the effects of stacking faults can be achieved with a simple configuration. Provided is a method for measuring a film thickness.

(Third embodiment)
Hereinafter, the third embodiment will be described in detail. The third embodiment is different from the first embodiment in that a sample support 21 is provided, and the sample 4 and the calibration substrate 22 are provided on the sample support 21. FIG. 12 is a schematic diagram of an optical system of the X-ray diffraction apparatus 20 according to the third embodiment. The X-ray diffractometer 20 is a device for measuring the film thickness of an evaluation sample formed on a semiconductor substrate, and includes an X-ray source 2, a monochromator 3, a sample 4, a scintillation counter 5, a slit 6, and a slit. 7, an absorber 8, a sample rotation motor 9, a sample support 21, and a calibration substrate 22. The same reference numerals as those in the first embodiment denote the same components, and detailed description thereof is omitted.

  The sample support 21 holds the sample 4 and the calibration substrate 22 and is configured to move in the B direction with the calibration substrate 22 in the X-ray irradiation optical path during calibration and the sample 4 in the X-ray irradiation optical path during measurement. It has become. The calibration substrate 22 is a sample having a known crystal structure in which the maximum value of the X-ray diffraction intensity distribution and the film thickness reference value by TEM are measured in advance before being installed in the X-ray diffraction apparatus 20. In the third embodiment, the calibration substrate 22 is either a HOT (Hybrid Crystal Orientation Technology) substrate or an SOI (Silicon On Insulator) substrate, and the uppermost layer is made of silicon (Si). If the crystal plane orientation of either (100) or (110) is included, it is effective for the evaluation of crystallinity including film thickness measurement. In this case, the sample 4 is preferably a substrate similar to the calibration substrate 22.

  FIG. 13 is a block diagram of the X-ray diffraction apparatus 20 according to the third embodiment. In FIG. 13, the X-ray diffractometer 20 includes a scintillation counter 5, a correlation table 23, a correlation unit 24, a data calculation unit 25, a data output unit 26, and a measurement control unit 27.

  The measurement control unit 27 is the same as the measurement control unit 14, and issues operation instructions to the scintillation counter 5, the correlation unit 24, the data calculation unit 25, and the data output unit 26 to control the operation of the entire X-ray diffraction apparatus 20. It has a function to control. A specific configuration mainly includes a CPU (Central Processing Unit), a ROM (Read Only Memory) storing an operation control program, and the like, and is responsible for signal control of each of the above-described main parts.

  The correlation unit 24 is the same as the correlation unit 11 and reads calibration information in which the maximum value of the X-ray diffraction intensity distribution stored in the correlation table 23 is associated with the film thickness reference value, or describes the calibration information. A correlation table 23 to be generated in advance. Regarding the generation of the correlation table 23, the measurement operator manually inputs calibration information of the calibration substrate 22 and the standard sample, or acquires and automatically creates the X-ray diffraction intensity distributions of the calibration substrate 22 and the standard sample. Any of the configurations may be used. The data calculation unit 25 is the same as the data calculation unit 12 and has a function of calculating the film thickness of the sample 4 to be measured. The data output unit 26 is the same as the data output unit 13, and displays or prints out the film thickness of the sample 4 calculated by the data calculation unit 25.

  The correlation table 23 is a lookup table that stores calibration information in which the maximum value of the X-ray diffraction intensity distribution is associated with the film thickness reference value by TEM. FIG. 14 is an explanatory diagram showing a storage structure of the correlation table 23 of the X-ray diffraction apparatus 20 according to the third embodiment. Further, the correlation table 23 stores the maximum value of the X-ray diffraction intensity distribution of the calibration substrate 22 installed in the X-ray diffractometer 20 in association with the film thickness reference value by TEM. In FIG. Reference numeral 1 denotes data (Imem, Tmem) of the calibration substrate 22. A specific storage medium includes a DRAM (Direct Random Access Memory) having a predetermined capacity.

  Hereinafter, the film thickness measurement procedure of the X-ray diffraction apparatus 20 according to the third embodiment will be described in detail. FIG. 15 is a flowchart showing a film thickness measurement procedure of the X-ray diffraction apparatus 20 according to the third embodiment. First, the correlation unit 24 inputs the X-ray diffraction intensity of the calibration substrate 22 from the scintillation counter 5 and acquires the X-ray diffraction intensity distribution (step S200). The correlation unit 24 detects the maximum value Icor from the X-ray diffraction intensity distribution of the calibration substrate 22 (step S201). The correlation unit 24 calculates and stores the correction term Imem / Icor from the stored value Imem and the maximum value Icor on the correlation table 23 (step S202).

  Subsequently, the correlation unit 24 inputs the X-ray diffraction intensity of the sample 4 from the scintillation counter 5 and acquires the X-ray diffraction intensity distribution (step S203). The correlation unit 24 detects the maximum value Imax from the X-ray diffraction intensity distribution of the sample 4 (step S204). An appropriate value Imax · (Imem / Icor) is calculated (step S205). The correlation unit 24 searches the correlation table 23 for an appropriate value Imax · (Imem / Icor) (step S206). If there is a value that matches the appropriate value Imax · (Imem / Icor) as a result of the search (step S206: Yes), the correlation unit 24 instructs reading of the film thickness value on the correlation table 23 (step S207).

  On the other hand, if there is no value that matches the appropriate value Imax · (Imem / Icor) (step S206: No), the correlation unit 24 obtains I3 <Imax · (Imem / Icor) <I4 from the values on the correlation table 23. The data interpolation values I3 and I4 are read out and transmitted to the data calculation unit 25 (step S208). The data calculation unit 25 calculates the film thickness value D from the data interpolation values I3 and I4 and Imax · (Imem / Icor) and transmits it to the data output unit 26 (step S209). The data output unit 26 displays or prints out the film thickness value D (step S210).

  Regarding the calculation of the film thickness value D in step S209, the film thickness D can be calculated by adding the correction term Imem / Icor to the same concept as the film thickness measurement method according to the first embodiment. As with the film thickness measurement method according to the first embodiment, any method used for the calculation method does not affect the feasibility of the film thickness measurement method according to the third embodiment.

Here, similarly to the film thickness measurement method according to the first embodiment, when linear interpolation is used as a calculation example, the mathematical expression (1) according to the first embodiment is transformed into the following expression (2). . However, the X-ray diffraction intensities I3 and I4 are values on the correlation table 23 such that I3 <Imax · (Imem / Icor) <I4. The film thickness values on the correlation table 23 associated with I3 and I4 are D3 and D4, respectively.
D = (D3-D4) .Imax. (Imem / Icor) / (I3-I4) (2)
In the third embodiment, the configuration of one calibration substrate 22 has been described in detail. However, the configuration is not limited to one. A configuration in which a plurality of calibration substrates are provided in the apparatus to further improve measurement accuracy is also possible.

  Further, the X-ray diffraction intensity distribution input from the scintillation counter 5 is corrected by the correction term Imem / Icor, and the half width of the angle or the angle rising width is detected from the corrected X-ray diffraction intensity distribution. It is possible to provide the same abnormal value detection function as in the embodiment.

  As described above, according to the third embodiment, the correlation table in which the maximum value of the X-ray diffraction intensity distribution in the plurality of standard samples including the calibration substrate is associated with the film thickness reference value by the TEM is stored. In addition, the correction term is calculated from the maximum value of the X-ray diffraction intensity distribution of the calibration substrate during measurement, and the film thickness value is calculated from the maximum value, correction term, and correlation table of the X-ray diffraction intensity distribution of the evaluation sample. The film thickness measurement method enables high-speed and high-accuracy film thickness measurement and abnormal value detection by reducing measurement errors due to fluctuations in the X-ray source and X-ray detector with a simple configuration for various evaluation samples I will provide a.

(Fourth embodiment)
Hereinafter, the film thickness measuring method according to the fourth embodiment will be described in detail. The X-ray diffractometer 30 according to the fourth embodiment is different from the first embodiment in that an X-ray monitor sensor 31 is provided in the optical path before the sample 4 is irradiated with X-rays. is there. In the fourth embodiment, the X-ray intensity before irradiation of the sample 4 is detected, and the maximum value detected from the X-ray diffraction intensity distribution of the sample 4 is corrected by the X-ray intensity.

  FIG. 16 is a schematic diagram of an optical system of an X-ray diffraction apparatus 30 according to the fourth embodiment. In FIG. 16, an X-ray diffraction apparatus 30 is an apparatus that measures the film thickness of an evaluation sample formed on a semiconductor substrate. An X-ray monitor sensor 31, an X-ray source 2, a monochromator 3, a sample 4, and the like. A scintillation counter 5, a slit 6, a slit 7, an absorber 8, and a sample rotation motor 9 are provided. The X-ray monitor sensor 31 is provided on the optical path before the sample 4 is irradiated with X-rays, and detects the X-ray direct intensity before the sample 4 is irradiated. The X-ray monitor sensor 31 uses, for example, an X-ray count proportional tube, a semiconductor counter tube, or a scintillation counter. The same reference numerals as those in the first embodiment denote the same elements, and detailed description thereof is omitted.

  FIG. 17 is a block diagram of an X-ray diffraction apparatus 30 according to the fourth embodiment. In FIG. 17, an X-ray diffraction apparatus 30 includes a scintillation counter 5, an X-ray monitor sensor 31, a correlation table 32, a correlation unit 33, a data calculation unit 34, a data output unit 35, and a measurement control unit. 36.

  The correlation table 32 is the same as the correlation table 10, and is a lookup table that stores calibration information in which the maximum value of the X-ray diffraction intensity distribution is associated with the film thickness reference value by the TEM or spectroscopic method. is there. A specific storage medium includes a DRAM (Direct Random Access Memory) having a predetermined capacity.

  FIG. 18 is an explanatory diagram showing a storage structure of the correlation table 32 of the X-ray diffraction apparatus 30 according to the fourth embodiment. Similar to the correlation table 10, the correlation table 32 stores the maximum value of the X-ray diffraction intensity distribution and the film thickness value in association with each other, and further stores the X-ray direct intensity Xmem when these measurements are performed. Has been.

  The correlation unit 33 is the same as the correlation unit 11 and reads calibration information in which the maximum value of the X-ray diffraction intensity distribution stored in the correlation table 32 is associated with the film thickness reference value or describes the calibration information. The correlation table 32 is generated in advance. Regarding the generation of the correlation table 32, either a configuration in which a measurement operator manually inputs calibration information or a configuration in which an X-ray diffraction intensity distribution of a standard sample serving as a measurement reference is acquired and automatically created may be used. The data calculation unit 34 is the same as the data calculation unit 12 and has a function of calculating the film thickness of the evaluation sample to be measured. The data output unit 35 is the same as the data output unit 13 and has a function of displaying or printing out the film thickness of the evaluation sample calculated by the data calculation unit 34.

  The measurement control unit 36 is the same as the measurement control unit 14, and issues operation instructions to the scintillation counter 5, the X-ray monitor sensor 31, the correlation unit 33, the data calculation unit 34, and the data output unit 35, and X-ray diffraction It has a function of controlling the operation of the entire device 30. A specific configuration mainly includes a CPU (Central Processing Unit), a ROM (Read Only Memory) storing an operation control program, and the like, and is responsible for signal control of each of the above-described main parts.

  Hereinafter, the film thickness measurement procedure according to the fourth embodiment will be described in detail. FIG. 19 is a flowchart showing a film thickness measurement procedure according to the fourth embodiment. First, the correlation unit 33 inputs the X-ray direct intensity Xmea before the sample 4 is irradiated with X-rays from the X-ray monitor sensor 31 (step S300). The correlation unit 33 calculates a correction term Xmem / Xmea from the X-ray direct intensities Xmem and Xmea stored in the correlation table 32 (step S301). The correlation unit 33 stores the correction term Xmem / Xmea (step S302).

  Subsequently, the correlation unit 33 inputs the X-ray diffraction intensity of the sample 4 from the scintillation counter 5 and acquires the X-ray diffraction intensity distribution (step S303). The correlation unit 33 detects the maximum value Imax from the X-ray diffraction intensity distribution (step S304). The correlation unit 33 calculates an appropriate value Imax · (Xmem / Xmea) (step S305). The correlation unit 33 searches the correlation table 32 for an appropriate value Imax · (Xmem / Xmea) (step S306). If there is a value that matches the appropriate value Imax · (Xmem / Xmea) as a result of the search (step S307: Yes), the correlation unit 33 instructs reading of the film thickness value on the correlation table 32 (step S308).

  On the other hand, if there is no value that matches the appropriate value Imax · (Xmem / Xmea) (step S307: No), the correlation unit 33 obtains I5 <Imax · (Xmem / Xmea) <I6 from the values on the correlation table 32. The data interpolation values I5 and I6 are read out and transmitted to the data calculation unit 34 (step S309). The data calculation unit 34 calculates the film thickness value D from the data interpolation values I5 and I6 and the appropriate value Imax · (Xmem / Xmea) and transmits it to the data output unit 35 (step S310). The data output unit 35 displays or prints out the film thickness value D (step S311).

  Regarding the calculation of the film thickness value D in step S310, the film thickness D can be calculated by adding the correction term Xmem / Xmea to the same idea as the film thickness measurement method according to the first embodiment. As with the film thickness measurement method according to the first embodiment, any method used for the calculation method does not affect the feasibility of the film thickness measurement method according to the fourth embodiment.

Here, similarly to the film thickness measurement method according to the first embodiment, if linear interpolation is used as a calculation method example, the mathematical expression (1) according to the first embodiment is transformed into the following expression (3). To do. However, the X-ray diffraction intensities I5 and I6 are I5 <Imax · (Xmem / Xmea) <I6. The film thickness values on the correlation table 32 associated with I5 and I6 are D5 and D6, respectively.
D = (D5-D6) .Imax. (Xmem / Xmea) / (I5-I6) (3)

  As a result of measuring the film thickness as described above, the measurement accuracy is greatly improved as compared to before introducing the fourth embodiment. Here, a HOT substrate by direct bonding comprising an uppermost layer Si (110) having a thickness of 200 nm and a substrate Si (100) having a thickness of 775 nm was prepared. While obtaining the X-ray diffraction intensity distribution for the uppermost Si (110) crystal plane of this HOT substrate and the Si (220) crystal plane below it to detect the maximum value, the X-ray intensity before irradiation of the HOT substrate was detected. . Depending on the detected X-ray intensity, measurement was performed 16 times (total 30 hours) every 2 hours under two conditions, with and without correction of the X-ray diffraction intensity of the HOT substrate. FIG. 20 is a graph showing the improvement effect of the film thickness measurement method according to the fourth embodiment. The horizontal axis represents the elapsed time of film thickness measurement, and the vertical axis represents the difference from the average value of the X-ray intensity. X-rays emitted from the X-ray source 2 are sensitive to temperature fluctuations. Accordingly, when the X-ray intensity correction is not performed, the difference from the average value of about 4% at the maximum is improved. When the X-ray intensity correction is performed, the difference is improved from the average value of ± 1% or less. This is because the collision of the electron beam with the target sample of the X-ray source 2 and the state of thermal vibration inside the sample and the monochromator change due to temperature fluctuations.

  Further, the X-ray diffraction intensity distribution input from the scintillation counter 5 is corrected by the correction term Xmem / Xmea based on the above-mentioned X-ray direct intensity, and the half width of the angle or the angle rising width is detected from the corrected X-ray diffraction intensity distribution. Thus, it is possible to provide an abnormal value detection function similar to that of the first embodiment.

  As described above, according to the fourth embodiment, the correction term is calculated from the X-ray direct intensity before irradiation of the evaluation sample and the X-ray direct intensity before irradiation of the standard sample stored when the correlation table is created. By calculating the film thickness value from the maximum value of the X-ray diffraction intensity distribution of the evaluation sample, the correction term, and the correlation table, the X-ray radiation amount of the evaluation sample having a different crystal structure can be obtained with a simple configuration. Provided is a film thickness measurement method capable of reducing an error due to fluctuation and enabling high-speed and high-accuracy film thickness measurement and abnormal value detection.

  In the first embodiment to the fourth embodiment, the feature amount of the X-ray diffraction intensity distribution selected in advance and the film thickness reference value are associated with each other and stored in a lookup table, and data interpolation is performed during measurement. Details have been described as the configuration for calculating the film thickness value. If the storage capacity of the lookup table is increased, the data interval can be made closer, and it goes without saying that the above-described data interpolation is not necessary.

  In the first to fourth embodiments, the embodiment has been described as storing the calibration information of the feature amount and the film thickness reference value in the lookup table. However, the feature amount and the film thickness are described. A configuration in which a regression equation by multi-dimensional regression, hyperbola regression, logarithmic regression or exponential regression is obtained in advance from the calibration information of the reference value, the form and coefficient of the regression equation are stored as a calibration function, and the film thickness value is calculated by the calibration function during measurement. The same effect can be obtained. Further, the same effect can be obtained by obtaining the calibration function using the least square method. These methods of calculating the film thickness value do not affect the feasibility of the technique of the film thickness measuring method according to the present invention.

  The film thickness measurement program executable by the X-ray diffractometer according to the present invention is a CD-ROM, flexible disk (FD), CD-R, DVD (Digital Versatile) in an installable or executable file. The program is recorded on a computer-readable recording medium such as a disk.

  The film thickness measurement program executable by the film thickness measurement method according to the present invention may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. . Further, a film thickness measurement program executable by the film thickness measurement method according to the present invention may be provided or distributed via a network such as the Internet.

  In addition, a film thickness measurement program that can be used in the above-described embodiments may be provided by being incorporated in advance in a ROM or the like.

  The film thickness measurement program capable of executing the film thickness measurement method that can be used in all the embodiments described above includes the above-described units (correlation unit, correlation table, data calculation unit, data output unit, measurement control unit) ). In addition, as actual hardware, the CPU reads the film thickness measurement program from a computer-readable recording medium and executes it, so that the above-described units are loaded on the main storage device, and a correlation unit, a correlation table, A data calculation unit, a data output unit, and a measurement control unit are generated on the main storage device. Thereafter, the arithmetic processing of the film thickness measuring method according to the present invention is executed.

The optical system schematic diagram of the X-ray-diffraction apparatus 1 concerning 1st embodiment. 1 is a block diagram of an X-ray diffraction apparatus 1 according to a first embodiment. Explanatory drawing which shows the memory structure of the correlation table 10 of the X-ray diffraction apparatus 1 concerning 1st embodiment. The graph which shows the relationship between the maximum value of X-ray diffraction intensity distribution of Si thin film, and the cross-sectional film thickness measured value by TEM. The graph which expanded and showed the area | region where the measured value of the graph shown in FIG. 4 is low. The flowchart which shows the film thickness measurement procedure concerning 1st embodiment. The graph explaining Example 1 regarding the abnormal value detection of the film thickness measurement of 2 types of different crystal planes. The graph explaining Example 2 regarding the abnormal value detection of the film thickness measurement of 2 types of different crystal planes. The block diagram of the X-ray-diffraction apparatus 16 concerning 2nd embodiment. Explanatory drawing which shows the memory structure of the correlation table 15 concerning 2nd embodiment. The graph which shows the X-ray diffraction intensity distribution which carried out the angle scan in the X-ray-diffraction apparatus 16 concerning 2nd embodiment. The optical system schematic diagram of the X-ray-diffraction apparatus 20 concerning 3rd embodiment. The block diagram of the X-ray-diffraction apparatus 20 concerning 3rd embodiment. Explanatory drawing which shows the memory structure of the correlation table 23 of the X-ray-diffraction apparatus 20 concerning 3rd embodiment. The flowchart which shows the film thickness measurement procedure of the X-ray-diffraction apparatus 20 concerning 3rd embodiment. The optical system schematic of the X-ray-diffraction apparatus 30 concerning 4th embodiment. The block diagram of the X-ray-diffraction apparatus 30 concerning 4th embodiment. Explanatory drawing which shows the memory structure of the correlation table 32 of the X-ray-diffraction apparatus 30 concerning 4th embodiment. The flowchart which shows the film thickness measurement procedure concerning 4th embodiment. The graph which shows the improvement effect of the film thickness measuring method concerning 4th embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 X-ray diffraction apparatus 2 X-ray source 3 Monochromator 4 Sample 5 Scintillation counter 6 Slit 7 Slit 8 Absorber 10 Correlation table 11 Correlation part 12 Data calculation part 13 Data output part 14 Measurement control part 15 Correlation table 20 X-ray Diffraction device 21 Sample support table 22 Calibration substrate 23 Correlation table 24 Correlation unit 25 Data calculation unit 26 Data output unit 27 Measurement control unit 30 X-ray diffraction device 31 X-ray monitor sensor 32 Correlation table 33 Correlation unit 34 Data Calculation unit 35 Data output unit 36 Measurement control unit A Sample rotation direction B Sample support table movement direction Imax Maximum value of X-ray diffraction intensity distribution Icor Maximum value of X-ray diffraction intensity distribution with respect to calibration substrate Imem X with respect to calibration substrate Line diffraction intensity Detected value of X-ray direct intensity at the time of measurement Xmea Xmem Detected value of X-ray direct intensity at the time of creating the correlation table 32 I1 Approximate value I2 smaller on the correlation table 10 Larger value on the correlation table 10 Imax approximate value I3 The smaller Imax approximate value I4 on the correlation table 23 The larger Imax approximate value I5 on the correlation table 23 The smaller Imax approximate value I6 on the correlation table 32 On the correlation table 32 Larger Imax approximate value D1 Film thickness value D2 corresponding to I1 on the correlation table 10 Film thickness value D3 corresponding to I2 on the correlation table 10 Film thickness value D4 corresponding to I3 on the correlation table 23 On the relation table 23 Film thickness value D5 corresponding to 4 Film thickness value D6 corresponding to I5 on the correlation table 32 Film thickness value D corresponding to I6 on the correlation table 32 Film thickness measurement value F1 of the evaluation sample X-ray of the crystal plane 3 Angle rise width F2 of diffraction intensity distribution Angle rise width G1 of X-ray diffraction intensity distribution on crystal plane 4 Integral value G2 of X-ray diffraction intensity distribution on crystal plane 5 Integral value of X-ray diffraction intensity distribution on crystal plane 6

Claims (8)

A method for measuring the film thickness of the uppermost layer of an evaluation sample having a multilayer film structure using an X-ray diffractometer,
A reference value measuring step for measuring a film thickness reference value of a standard sample using a film thickness measuring method other than an X-ray diffractometer;
Calibration in which an X-ray diffraction intensity distribution is acquired by scanning an X-ray irradiation angle on the standard sample, and a feature amount detected from the X-ray diffraction intensity distribution is associated with the film thickness reference value of the standard sample A calibration information generation step for generating information in advance;
A distribution acquisition step of acquiring an X-ray diffraction intensity distribution by scanning an X-ray irradiation angle on the evaluation sample;
A feature amount detection step of detecting a feature amount from the X-ray diffraction intensity distribution acquired in the distribution acquisition step;
A film thickness measurement method comprising: a film thickness calculation step of calculating a film thickness of the uppermost layer of the evaluation sample from the feature quantity detected in the feature quantity detection step and the calibration information.   The film thickness measurement method according to claim 1, wherein the feature amount is either a maximum value or an integral value of the X-ray diffraction intensity distribution.   The film thickness measurement method according to claim 1 or 2, wherein the film thickness reference value is a film thickness measured by either a transmission electron microscope or a spectroscopic emsometry method.   The film thickness measuring method according to claim 1, wherein the standard sample is held in the X-ray diffraction apparatus. The standard sample and the evaluation sample are either a HOT (Hybrid Crystal Orientation Technology) substrate or an SOI (Silicon On Insulator) substrate,
5. The film thickness measurement according to claim 1, wherein the uppermost layer has a crystal plane orientation of (100) or (110) of silicon (Si). Method.   6. The X-ray intensity before being irradiated on the evaluation sample is detected, and the feature quantity detected in the feature quantity detection step is corrected based on the X-ray intensity. The film thickness measuring method according to item.   The film thickness measuring method according to claim 1, wherein the film thickness of the uppermost layer is 10 nm or more. 3. The crystallinity of the evaluation sample is evaluated by detecting either an angle half width or an angle rising width from the X-ray diffraction intensity distribution of the evaluation sample acquired in the distribution acquisition step. The film thickness measuring method as described.

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