CN115727774B - Calibration method and calibration sheet for measuring thickness of epitaxial layer by infrared spectrometer - Google Patents
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Abstract
The invention provides a calibration method and a calibration sheet for measuring the thickness of an epitaxial layer by an infrared spectrometer, wherein the calibration method comprises the steps of measuring the actually measured epitaxial thickness of a target standard sheet by the infrared spectrometer; determining the fitting thickness of the target standard piece based on the actually measured epitaxial thickness of the target standard piece and a preset fitting linear equation of an infrared spectrometer; the fitting linear equation is obtained by fitting a first epitaxial thickness based on a plurality of epitaxial standard wafers with different epitaxial thicknesses and a second epitaxial thickness based on a plurality of epitaxial standard wafers with different epitaxial thicknesses, wherein the first epitaxial thickness is obtained by testing through a calibrated flatness tester, and the second epitaxial thickness is obtained by testing through an infrared spectrometer; and when the difference value between the fitting thickness of the target standard piece and the first epitaxial thickness of the target standard piece is larger than a first preset threshold value, calibrating the infrared spectrometer by adopting the target standard piece. The invention provides a calibration standard of an infrared spectrometer and a calibration sheet for calibration.
Description
Technical Field
The invention relates to the technical field of semiconductor testing, in particular to a calibration method and a calibration sheet for measuring thickness of an epitaxial layer by an infrared spectrometer.
Background
There are typically three important parameters for measuring epitaxial quality, thickness, resistivity and surface defects, respectively, where the measurement of thickness and resistivity directly affects the voltage characteristics of the subsequent process.
At present, the thickness of an epitaxy is mainly tested by an infrared spectrometer, and the infrared spectrometer realizes non-contact measurement of the thickness of a thin film material by utilizing absorption, reflection, interference and the like when infrared light penetrates through a substance. In the test, a low-doped epitaxial layer is required to be deposited on a substrate wafer with high doping concentration, and the resistivity of the substrate layer with high doping concentration is required to be smaller than 0.02 ohm cm, because an infrared spectrum is incident on the epitaxial surface of silicon after passing through a Michelson interferometer, and the thickness of the epitaxial layer is calculated through analysis of interference patterns formed by reflected light of the infrared spectrum on the epitaxial surface and the substrate surface respectively.
Since the built-in algorithm of the infrared spectrometer directly affects the thickness of the epitaxial layer to be measured, the test value of the thickness of the epitaxial layer is only a reference value. However, there is no standard wafer of the thickness of the epitaxial layer, so the accuracy of the thickness of the epitaxial layer measured by the infrared spectrometer cannot be known. Typically, the epitaxial factory processes and samples from the customer, and only needs to ensure the stability of the infrared spectrometer, while less attention is paid to the accuracy of the thickness value of the epitaxial layer. When the infrared spectrometer needs to be calibrated, how to judge the calibration result does not have a definite calibration standard, so that a calibration method is needed to calibrate the infrared spectrometer timely and accurately.
Disclosure of Invention
The embodiment of the invention provides a calibration method and a calibration sheet for measuring the thickness of an epitaxial layer by an infrared spectrometer, which are used for solving the problem that whether the infrared spectrometer needs to be calibrated or not cannot be determined at present.
In a first aspect, an embodiment of the present invention provides a calibration method for measuring thickness of an epitaxial layer by using an infrared spectrometer, including:
measuring the actually measured epitaxial thickness of a target standard wafer by adopting an infrared spectrometer, wherein the target standard wafer is any one of a plurality of epitaxial standard wafers with different epitaxial thicknesses;
determining the fitting thickness of the target standard piece based on the actually measured epitaxial thickness of the target standard piece and a preset fitting linear equation of an infrared spectrometer; the fitting linear equation is obtained by fitting a first epitaxial thickness based on a plurality of epitaxial standard wafers with different epitaxial thicknesses and a second epitaxial thickness based on a plurality of epitaxial standard wafers with different epitaxial thicknesses, wherein the first epitaxial thickness is obtained by testing through a calibrated flatness tester, and the second epitaxial thickness is obtained by testing through an infrared spectrometer;
and when the difference value between the fitting thickness of the target standard piece and the first epitaxial thickness of the target standard piece is larger than a first preset threshold value, calibrating the infrared spectrometer by adopting the target standard piece.
In one possible implementation manner, each epitaxial standard wafer with different epitaxial thicknesses is provided with a substrate reference wafer, and the thickness of each epitaxial standard wafer is equal to the center thickness of the corresponding substrate reference wafer when the epitaxial preparation process is not performed;
the calibration method further comprises the following steps:
adopting a calibrated flatness tester to test the thickness of a target standard sheet, and marking the thickness as a first standard thickness;
the thickness of the substrate reference sheet of the target standard sheet is tested by adopting a calibrated flatness tester and is recorded as a second standard thickness;
recording the difference value of the first standard thickness and the second standard thickness as the actual measurement standard thickness of the target standard sheet;
and when the difference value between the actually measured standard thickness of the target standard wafer and the first epitaxial thickness of the target standard wafer is smaller than a second preset threshold value, determining that the target standard wafer is a normal epitaxial standard wafer.
In one possible implementation, the first epitaxial thickness is the difference between the first initial thickness and the second standard thickness; the first initial thickness is the thickness tested by the calibrated flatness tester for the first time after the epitaxial preparation of the target standard wafer is finished;
the second epitaxial thickness is the thickness tested by the infrared spectrometer for the first time after the epitaxial preparation of the target standard wafer is completed.
In one possible implementation, the independent variable in the fitted linear equation is the second epitaxial thickness obtained by infrared spectrometer testing, and the dependent variable in the fitted linear equation is the first epitaxial thickness obtained by calibrated flatness tester testing.
In one possible implementation, the coefficients and deviations in fitting the linear equations are the same as the coefficients and deviations, respectively, of the linear equations in the test procedure of the infrared spectrometer.
In one possible implementation, determining the fitting thickness of the target standard piece based on the measured epitaxial thickness of the target standard piece and a preset fitting linear equation of the infrared spectrometer includes:
and inputting the epitaxial thickness of the target standard piece into a fitting linear equation to obtain the fitting thickness of the target standard piece.
In one possible implementation, the plurality of epitaxial standard wafers of different epitaxial thicknesses comprises a plurality of epitaxial wafers of graded epitaxial thickness.
In one possible implementation, the plurality of epitaxial wafers of different epitaxial thicknesses includes an epitaxial wafer of minimum thickness that can be measured by an infrared spectrometer, and also includes an epitaxial wafer of maximum thickness that can be measured by an infrared spectrometer.
In a second aspect, embodiments of the present invention provide a calibration tile for calibrating an infrared spectrometer for measuring epitaxial layer thickness, comprising a plurality of sets of standard tiles,
each group of standard sheets at least comprises two substrates with the same central thickness, wherein one substrate is used as a substrate reference sheet, and the other substrate is used for preparing epitaxy with preset thickness on the substrate and is used as an epitaxy standard sheet; and the epitaxial thickness of the epitaxial standard wafer in each group of standard wafers is different.
In one possible implementation, the plurality of sets of standard pieces includes an epitaxial standard piece of minimum thickness that can be measured by an infrared spectrometer, and also includes an epitaxial standard piece of maximum thickness that can be measured by an infrared spectrometer.
The embodiment of the invention provides a calibration method and a calibration sheet for measuring the thickness of an epitaxial layer by an infrared spectrometer. And finally, when the difference value between the fitting thickness of the target standard piece and the first epitaxial thickness of the target standard piece is larger than a first preset threshold value, calibrating the infrared spectrometer by adopting the target standard piece. And comparing the fitting thickness of the target standard sheet obtained by fitting by adopting a preset fitting linear equation of the infrared spectrometer with the first epitaxial thickness of the target standard sheet, and determining whether the infrared spectrometer needs to be calibrated or not, if so, calibrating the infrared spectrometer by adopting the target standard sheet. Therefore, the problem that the existing infrared spectrometer does not have an explicit calibration standard can be effectively solved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of the testing principle of an infrared spectrometer;
FIG. 2 is a flowchart of an implementation of a calibration method for measuring epitaxial layer thickness by an infrared spectrometer according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of test data and a fitted linear equation provided by an embodiment of the present invention.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth such as the particular system architecture, techniques, etc., in order to provide a thorough understanding of the embodiments of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the following description will be made by way of specific embodiments with reference to the accompanying drawings.
As described in the background, there are three important parameters for measuring the epitaxial quality, namely thickness, resistivity and surface defects, wherein the thickness and resistivity directly affect the voltage characteristics of the subsequent process. At present, no standard sheet for correcting an infrared spectrometer exists in the industry, all the standard sheets are assigned based on the test result of the infrared spectrometer at home, and the test instrument is monitored periodically according to the value.
First, the test principle of an infrared spectrometer is briefly described, as shown in fig. 1, which is a schematic diagram of the test principle of the infrared spectrometer, and if the epitaxial thickness needs to be accurately measured, an epitaxial layer with low doping concentration needs to be deposited on a substrate wafer with high doping concentration, and infrared reflection measurement technology is used for measurement. For measurement accuracy, the resistivity of the high-concentration substrate layer is required to be less than 0.02 Ω·cm, because the test mechanism is that infrared spectrum is incident on the silicon epitaxial surface after passing through the michelson interferometer, and the thickness of the epitaxial layer is calculated by analyzing interference patterns formed by reflected light of the infrared spectrum on the epitaxial surface and the substrate surface, respectively. Lightly doped epitaxial layers are relatively transparent to the infrared spectrum at wavelengths in the range of 2.5 μm to 50 μm, but heavily doped substrates act as reflective surfaces for this range, so infrared reflection techniques can be used to determine the thickness of the epitaxial layer.
Because the infrared spectrometer cannot judge the accuracy of the test after being used for a period of time, the infrared spectrometer cannot be determined when the infrared spectrometer needs to be calibrated and how to calibrate the infrared spectrometer. Thus, there is a need for a method for calibrating an infrared spectrometer.
Before describing the calibration method, the calibration sheet and the preparation process of the calibration sheet provided by the invention are described first.
The calibration sheet of the infrared spectrometer comprises a plurality of groups of standard sheets, and each group of standard sheets comprises at least one substrate reference sheet and one epitaxial standard sheet. The epitaxial standard wafers in each group have the same center thickness of the substrate as the center thickness of the substrate reference wafer in the group before the epitaxial process is not performed. The center thicknesses of the substrate reference wafer and the substrate of the epitaxial standard wafer of each group of standard wafers are tested by adopting an ADE flatness tester through a mechanism with CNAS calibration qualification. Other calibrated flatness testers may also be used, without limitation. The ADE flatness tester is used for introduction in the application.
The traceability is achieved by arranging at least one substrate reference wafer and an epitaxial standard wafer in each group of standard wafers. If the substrate reference sheet is not arranged, the epitaxial standard sheet is only arranged, the epitaxial standard sheet cannot be restored to the state before epitaxy after epitaxy is grown, and once the level of the ADE flatness tester is changed, the thickness of the epitaxial standard sheet is also changed, and whether the epitaxial standard sheet is changed or the ADE flatness tester is not leveled can not be determined, so that the substrate reference sheet needs to be stored for long-term use. Therefore, the epitaxial standard wafer and the substrate reference wafer of each group can be sent to a mechanism for calibration with metering qualification at any time, so that whether the epitaxial standard wafer has abrasion or not can be determined, and whether the epitaxial standard wafer can be continuously used for calibration or not can be determined.
After selecting a plurality of groups of substrates with the same central thickness from the substrates, at least 2 substrates are arranged in each group, the central thicknesses of all the substrates in each group are required to be the same, and the central thicknesses of the substrates in different groups can be the same or different, and the method is not limited herein.
After a plurality of groups of substrates are selected, at least one substrate is selected from each group of substrates for epitaxy, and the epitaxial thickness of each group of substrates is unequal. The multi-group standard pieces comprise the epitaxial standard pieces with the minimum thickness which can be measured by the infrared spectrometer, and also comprise the epitaxial standard pieces with the maximum thickness which can be measured by the infrared spectrometer. The thickness of each group of epitaxial standard wafers can be prepared on the basis of the epitaxial standard wafers with the minimum thickness which can be measured by an infrared spectrometer, and the thickness is 5 mu m at intervals until the maximum thickness of 150 mu m-200 mu m of the energy side of the infrared spectrometer to be calibrated is reached.
For each group of standard pieces, firstly, an ADE flatness tester calibrated by a mechanism with CNAS calibration qualification is selected to test the thickness of an epitaxial standard piece in each group of standard pieces, and the thickness is marked as B 1 、B 2 、B 3 、B 4 … … the thickness of the substrate reference sheet in each group of standard sheets was measured by using the calibrated ADE flatness tester and is denoted as A 1 、A 2 、A 3 、A 4 … … the thickness of the epitaxial standard wafer in each group of standard wafers is recorded as B 1 -A 1 、B 2 -A 2 、B 3 -A 3 、B 4 -A 4 … …, for facilitating the subsequent calculation, B 1 -A 1 、B 2 -A 2 、B 3 -A 3 、B 4 -A 4 … … is denoted as Y 1 、Y 2 、Y 3 、Y 4 ……。
Then, the thickness of the epitaxial standard wafer in each group of standard wafers is tested by an infrared spectrometer and is marked as X 1 、X 2 、X 3 、X 4 ……。
Finally, utilize X 1 、X 2 、X 3 、X 4 … … and Y 1 、Y 2 、Y 3 、Y 4 … … performing linear fitting, wherein the fitted linear equation is y=ax+b, the values of a and b are obtained, and the values of a and b are written into the linear equation in the infrared spectrometer machine test program. The independent variable in the fitted linear equation is the second epitaxial thickness obtained by testing with an infrared spectrometer, and the independent variable in the fitted linear equation is the first epitaxial thickness obtained by testing with a calibrated ADE flatness tester.
After a linear equation in an infrared spectrometer machine test program is determined and a plurality of groups of calibration sheets are prepared, the calibration sheets can be used for judging whether the infrared spectrometer needs to be calibrated after the infrared spectrometer is used for a period of time.
The test for the thickness of the epitaxial wafer and the substrate sheet is not limited to the ADE flatness tester.
The following mainly describes a calibration method for measuring the thickness of an epitaxial layer by using an infrared spectrometer provided by the embodiment of the invention. Referring to fig. 2, a flowchart of an implementation of a calibration method for measuring thickness of an epitaxial layer by using an infrared spectrometer according to an embodiment of the present invention is shown, and the details are as follows:
and S210, measuring the actually measured epitaxial thickness of the target standard wafer by adopting an infrared spectrometer.
The target standard wafer is any one of a plurality of epitaxial standard wafers with different epitaxial thicknesses.
Specifically, the epitaxial standard wafers with different epitaxial thicknesses can include a plurality of epitaxial wafers with gradually-changed epitaxial thicknesses, and also can be a plurality of epitaxial wafers with unequal epitaxial layer thicknesses prepared according to preset thicknesses. The infrared spectrometer also comprises an epitaxial standard wafer with the minimum thickness which can be measured by the infrared spectrometer, and also comprises an epitaxial standard wafer with the maximum thickness which can be measured by the infrared spectrometer.
For example, one is prepared every 5 μm on the basis of an epitaxial standard wafer of minimum thickness that can be measured by an infrared spectrometer until a maximum thickness of 150 μm-200 μm on the energy side of the infrared spectrometer to be calibrated is reached.
And S220, determining the fitting thickness of the target standard piece based on the actually measured epitaxial thickness of the target standard piece and a preset fitting linear equation of an infrared spectrometer.
The fitting linear equation is obtained by fitting a first epitaxial thickness of the epitaxial standard wafers with different epitaxial thicknesses and a second epitaxial thickness of the epitaxial standard wafers with different epitaxial thicknesses, wherein the first epitaxial thickness is obtained by testing through a calibrated flatness tester, and the second epitaxial thickness is obtained by testing through an infrared spectrometer.
Specifically, the first epitaxial thickness is the difference between the first initial thickness and the second standard thickness. The first initial thickness is the thickness tested by the calibrated flatness tester for the first time after the epitaxial preparation of the target standard wafer is completed. The second epitaxial thickness is the thickness tested by the infrared spectrometer for the first time after the epitaxial preparation of the target standard wafer is completed.
After the values of a and b in the fitting linear equation y=ax+b are determined, the coefficients of the linear equation in the test program of the infrared spectrometer are set to be the same as a, and the deviation of the linear equation in the test program is set to be the same as b. Here, the fitting process of the preset fitting linear equation of the infrared spectrometer is not described herein.
And after obtaining the actually measured epitaxial thickness of the target standard wafer, bringing the actually measured epitaxial thickness of the target standard wafer into a fitting linear equation to obtain the fitting thickness of the target standard wafer.
And step S230, when the difference value between the fitting thickness of the target standard piece and the first epitaxial thickness of the target standard piece is larger than a first preset threshold value, calibrating the infrared spectrometer by adopting the target standard piece.
Wherein, after the first epitaxial thickness of the target standard wafer is the preparation of the target epitaxial standard wafer, the thickness B of the target epitaxial standard wafer is tested by adopting a calibrated flatness tester 1 Thickness A of substrate reference sheet with target epitaxial standard sheet tested by adopting calibrated flatness tester 1 Is the difference B of (2) 1 -A 1 And (3) preserving the infrared spectrometer as one of the judging standards for judging whether the infrared spectrometer needs to be calibrated later.
And comparing the difference value of the fitting thickness of the target standard sheet and the first epitaxial thickness of the target standard sheet with a preset threshold value to determine whether the infrared spectrometer needs to be calibrated.
In addition, since the epitaxial standard wafer needs to be used for calibrating the infrared spectrometer frequently, abrasion or deformation can also occur, and the epitaxial standard wafer needs to be detected to determine whether the epitaxial standard wafer meets the requirements of the calibration wafer.
And if the epitaxial standard wafer meets the requirement of the calibration wafer, verifying by adopting a substrate reference wafer corresponding to the epitaxial standard wafer. The epitaxial standard wafers and the substrate reference wafers in each group of standard wafers can be sent to a metering center with calibration qualification periodically every year, and the center thickness of the epitaxial standard wafers and the substrate reference wafers is tested by adopting a flatness tester.
If the center thickness of the epitaxial standard wafer is tested by adopting a flatness tester, the thickness is C 1 The center thickness of the substrate reference sheet is measured by adopting a flatness tester to be D 1 The epitaxial thickness of the epitaxial standard wafer at the current moment is C 1 -D 1 When C 1 -D 1 First epitaxial thickness B with the set of remaining calibration sheets 1 -A 1 And when the difference value of the target standard wafer is smaller than a second preset threshold value, determining that the target standard wafer is a normal epitaxial standard wafer.
Therefore, the problem that the current epitaxial thickness meter has no international standard can be solved, the accuracy and the stability of the infrared spectrometer can be calibrated and monitored by using the calibration sheet, and the reproducibility of the calibration sheet is provided.
The test for the thickness of the epitaxial wafer and the substrate sheet is not limited to the ADE flatness tester. The thickness of the epitaxial layer measured by the flatness tester is not limited to the calibration of the infrared spectrometer, and the thickness of the epitaxial layer measured by the infrared spectrometer can be used for evaluating the accuracy of the thickness non-uniformity of the epitaxial layer measured by the infrared spectrometer.
The following description will take a specific example:
the test results of the 25 groups of calibration sheets are tested, and the obtained linear fitting equation is as follows: y=1.0109X-0.3188, the independent variable is the second epitaxial thickness measured by infrared spectrometer test, and the dependent variable in the fitted linear equation is the first epitaxial thickness measured by calibrated ADE flatness tester test. The preparation process of each standard sheet is not described herein.
Then, the infrared spectrometer is calibrated by using 7 groups of calibration sheets, the calibration result is shown in table 1, the difference between the calibrated data and the fitted linear equation is shown in fig. 3, the horizontal axis in fig. 3 is the epitaxial thickness tested by using the infrared spectrometer, and the vertical axis is the first epitaxial thickness reserved for each group of calibration sheets.
Table 1 calibration data
In this embodiment, d'/d-1 is not more than.+ -. 0.3%, and the infrared tester is considered to be stable without abnormality, and no calibration is required.
However, if d '/d-1 exceeds.+ -. 0.3%, the infrared spectrometer is deemed to be calibrated with a calibration plate until d'/d-1 does not exceed.+ -. 0.3%.
According to the calibration method for measuring the thickness of the epitaxial layer by the infrared spectrometer, firstly, the actually measured epitaxial thickness of the target standard sheet is measured by the infrared spectrometer, and then, the fitting thickness of the target standard sheet is determined based on the actually measured epitaxial thickness of the target standard sheet and a preset fitting linear equation of the infrared spectrometer. And finally, when the difference value between the fitting thickness of the target standard piece and the first epitaxial thickness of the target standard piece is larger than a first preset threshold value, calibrating the infrared spectrometer by adopting the target standard piece. And comparing the fitting thickness of the target standard sheet obtained by fitting by adopting a preset fitting linear equation of the infrared spectrometer with the first epitaxial thickness of the target standard sheet, and determining whether the infrared spectrometer needs to be calibrated or not, if so, calibrating the infrared spectrometer by adopting the target standard sheet. Therefore, the problem that the existing infrared spectrometer does not have an explicit calibration standard can be effectively solved.
It should be understood that the sequence number of each step in the foregoing embodiment does not mean that the execution sequence of each process should be determined by the function and the internal logic, and should not limit the implementation process of the embodiment of the present invention.
The above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention, and are intended to be included in the scope of the present invention.
Claims (9)
1. A method for calibrating thickness of an epitaxial layer measured by an infrared spectrometer, comprising:
measuring the actually measured epitaxial thickness of a target standard wafer by adopting an infrared spectrometer, wherein the target standard wafer is any one of a plurality of epitaxial standard wafers with different epitaxial thicknesses, each epitaxial standard wafer with different epitaxial thicknesses is provided with a substrate reference wafer, and the thickness of each epitaxial standard wafer is equal to the center thickness of the corresponding substrate reference wafer when the epitaxial preparation process is not carried out;
determining the fitting thickness of the target standard piece based on the actually measured epitaxial thickness of the target standard piece and a preset fitting linear equation of the infrared spectrometer; the fitting linear equation is obtained by fitting a first epitaxial thickness based on a plurality of epitaxial standard wafers with different epitaxial thicknesses and a second epitaxial thickness based on the epitaxial standard wafers with different epitaxial thicknesses, wherein the first epitaxial thickness is obtained by testing through a calibrated flatness tester, and the second epitaxial thickness is obtained by testing through an infrared spectrometer;
when the difference value between the fitting thickness of the target standard sheet and the first epitaxial thickness of the target standard sheet is larger than a first preset threshold value, calibrating the infrared spectrometer by adopting the target standard sheet;
wherein, still include:
adopting a calibrated flatness tester to test the thickness of the target standard sheet, and marking the thickness as a first standard thickness; the thickness of the substrate reference sheet of the target standard sheet is tested by adopting a calibrated flatness tester and is recorded as a second standard thickness; recording the difference value of the first standard thickness and the second standard thickness as the actual measurement standard thickness of the target standard sheet; and when the difference value between the actually measured standard thickness of the target standard wafer and the first epitaxial thickness of the target standard wafer is smaller than a second preset threshold value, determining that the target standard wafer is a normal epitaxial standard wafer.
2. The calibration method of claim 1, wherein the first epitaxial thickness is a difference between a first initial thickness and the second standard thickness; the first initial thickness is the thickness tested by a calibrated flatness tester for the first time after the epitaxial preparation of the target standard wafer is completed;
and the second epitaxial thickness is the thickness tested by the infrared spectrometer for the first time after the epitaxial preparation of the target standard wafer is finished.
3. The method of calibrating according to claim 1, wherein the independent variable in the fitted linear equation is the second epitaxial thickness obtained by the infrared spectrometer test, and the dependent variable in the fitted linear equation is the first epitaxial thickness obtained by the calibrated flatness tester test.
4. A method of calibrating according to claim 3, wherein the coefficients and deviations in the fitted linear equation are the same as the coefficients and deviations, respectively, of the linear equation in the test procedure of the infrared spectrometer.
5. The method of calibrating according to claim 3, wherein the determining the fitting thickness of the target standard piece based on the measured epitaxial thickness of the target standard piece and a preset fitting linear equation of the infrared spectrometer comprises:
and inputting the epitaxial thickness of the target standard piece into the fitting linear equation to obtain the fitting thickness of the target standard piece.
6. The method of calibrating according to claim 1, wherein the plurality of epitaxial standard wafers of different epitaxial thicknesses comprises a plurality of epitaxial wafers of graded epitaxial thickness.
7. The method of calibrating according to claim 6, wherein the plurality of epitaxial wafers of different epitaxial thicknesses comprises an epitaxial wafer of a minimum thickness that can be measured by the infrared spectrometer, and further comprises an epitaxial wafer of a maximum thickness that can be measured by the infrared spectrometer.
8. A calibration sheet for calibrating an infrared spectrometer to measure the thickness of an epitaxial layer, comprising a plurality of sets of standard sheets, each set of standard sheets being used for the calibration method for an infrared spectrometer to measure the thickness of an epitaxial layer according to any one of claims 1 to 7;
each group of standard wafers at least comprises two substrates with the same central thickness, wherein one substrate is used as a substrate reference wafer, and the other substrate is used for preparing an epitaxy with a preset thickness on the substrate reference wafer to serve as an epitaxy standard wafer; and the epitaxial thicknesses of the epitaxial standard wafers in each group of standard wafers are different.
9. The calibration tile of claim 8, wherein the plurality of sets of standard tiles comprise epitaxial standard tiles of a minimum thickness that can be measured by the infrared spectrometer, and further comprising epitaxial standard tiles of a maximum thickness that can be measured by the infrared spectrometer.
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