CN115727774A - Calibration method for measuring thickness of epitaxial layer by infrared spectrometer and calibration sheet - Google Patents
Calibration method for measuring thickness of epitaxial layer by infrared spectrometer and calibration sheet Download PDFInfo
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Abstract
The invention provides a calibration method for measuring the thickness of an epitaxial layer by an infrared spectrometer and a calibration sheet, 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 wafer based on the actually measured epitaxial thickness of the target standard wafer and a preset fitting linear equation of the infrared spectrometer; the fitting linear equation is obtained by fitting based on first epitaxial thicknesses of a plurality of epitaxial standard wafers with different epitaxial thicknesses and second epitaxial thicknesses of the plurality of epitaxial standard wafers with different epitaxial thicknesses, the first epitaxial thicknesses are obtained by testing through a calibrated flatness tester, and the second epitaxial thicknesses are obtained by testing through an infrared spectrometer; and when the difference value between the fitting thickness of the target standard wafer and the first epitaxial thickness of the target standard wafer is greater than a first preset threshold value, calibrating the infrared spectrometer by using the target standard wafer. 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 the thickness of an epitaxial layer by an infrared spectrometer.
Background
There are three important parameters for measuring epitaxial quality, namely thickness, resistivity and surface defects, wherein the measurement of thickness and resistivity directly affects the voltage characteristics of the subsequent process.
At present, the thickness of epitaxy is mainly tested by an infrared spectrometer, and the infrared spectrometer realizes non-contact measurement of the thickness of thin film materials by using the effects of absorption, reflection, interference and the like when infrared light penetrates through substances. During testing, a low-doped epitaxial layer needs to be deposited on a substrate wafer with high doping concentration, the resistivity of the substrate layer with high doping concentration is required to be less than 0.02 omega cm, because the infrared spectrum is incident to the silicon epitaxial surface 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 can directly influence the thickness of the measured epitaxial layer, the measured value of the thickness of the epitaxial layer is only a reference value. However, at present, there is no standard wafer for the thickness of the epitaxial layer, so the accuracy of the thickness of the epitaxial layer measured by the infrared spectrometer cannot be known. Generally, an epitaxial factory can process and send samples for verification according to samples provided by customers, only the stability of the infrared spectrometer needs to be ensured, and the accuracy of the thickness value of the epitaxial layer is concerned a little. When the infrared spectrometer needs to be calibrated, and how to judge the calibration result, there is no clear calibration standard, so that a calibration method is urgently needed to calibrate the infrared spectrometer timely and accurately.
Disclosure of Invention
The embodiment of the invention provides a calibration method for measuring the thickness of an epitaxial layer by an infrared spectrometer and a calibration sheet, which are used for solving the problem that whether the infrared spectrometer needs to be calibrated cannot be determined at present.
In a first aspect, an embodiment of the present invention provides a calibration method for measuring an epitaxial layer thickness by 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 wafer based on the actually measured epitaxial thickness of the target standard wafer and a preset fitting linear equation of the infrared spectrometer; the fitting linear equation is obtained by fitting based on first epitaxial thicknesses of a plurality of epitaxial standard wafers with different epitaxial thicknesses and second epitaxial thicknesses of the plurality of epitaxial standard wafers with different epitaxial thicknesses, the first epitaxial thicknesses are obtained by testing through a calibrated flatness tester, and the second epitaxial thicknesses are obtained by testing through an infrared spectrometer;
and when the difference value between the fitting thickness of the target standard wafer and the first epitaxial thickness of the target standard wafer is greater than a first preset threshold value, calibrating the infrared spectrometer by using the target standard wafer.
In a possible implementation manner, each epitaxial standard wafer with different epitaxial thicknesses is provided with a substrate reference wafer, and the central thickness of each epitaxial standard wafer is equal to the central thickness of the corresponding substrate reference wafer when the epitaxial preparation process is not carried out on each epitaxial standard wafer;
the calibration method further comprises:
testing the thickness of the target standard sheet by using a calibrated flatness tester, and recording the thickness as a first standard thickness;
testing the thickness of the substrate reference sheet of the target standard sheet by using the calibrated flatness tester, and recording the thickness 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 a difference between the first initial thickness and the second standard thickness; the first initial thickness is the thickness which is tested by a 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 of the target standard wafer 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 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.
In one possible implementation, the coefficients and the deviations in the fitted linear equation are the same for the linear equation in the test program of the infrared spectrometer, respectively.
In a possible implementation manner, determining the fitting thickness of the target standard wafer based on the measured epitaxial thickness of the target standard wafer and a preset fitting linear equation of the infrared spectrometer includes:
and inputting the epitaxial thickness of the target standard wafer into a fitting linear equation to obtain the fitting thickness of the target standard wafer.
In one possible implementation, the plurality of epitaxial standard wafers with different epitaxial thicknesses comprises a plurality of epitaxial wafers with gradually changed epitaxial thicknesses.
In one possible implementation manner, the plurality of epitaxial standard wafers with different epitaxial thicknesses include an epitaxial standard wafer with the minimum thickness which can be measured by the infrared spectrometer, and an epitaxial standard wafer with the maximum thickness which can be measured by the infrared spectrometer.
In a second aspect, embodiments of the present invention provide a calibration sheet for calibrating a thickness of an epitaxial layer measured by an infrared spectrometer, comprising a plurality of sets of standard sheets,
each group of standard wafers at least comprises two substrates with the same center 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 and is used as an epitaxy standard wafer; and the epitaxial thicknesses of the epitaxial standard wafers in each group of standard wafers are different.
In a possible implementation manner, the plurality of groups of standard wafers comprise the epitaxial standard wafer with the minimum thickness which can be measured by the infrared spectrometer, and simultaneously comprise the epitaxial standard wafer with the maximum thickness which can be measured by the infrared spectrometer.
The embodiment of the invention provides a calibration method for measuring the thickness of an epitaxial layer by an infrared spectrometer and a calibration sheet. And finally, when the difference value between the fitting thickness of the target standard wafer and the first epitaxial thickness of the target standard wafer is larger than a first preset threshold value, calibrating the infrared spectrometer by using the target standard wafer. And determining whether the infrared spectrometer needs to be calibrated or not by comparing the fitting thickness of the target standard plate obtained by fitting through a preset fitting linear equation of the infrared spectrometer with the first epitaxial thickness of the target standard plate, and if the fitting thickness of the target standard plate is larger than a preset threshold value, calibrating the infrared spectrometer through the target standard plate. Therefore, the problem that the existing infrared spectrometer has no definite calibration standard can be effectively solved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
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 the thickness of an epitaxial layer 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 particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the 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.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the following description is made by way of specific embodiments with reference to the accompanying drawings.
As described in the background, there are three important parameters for measuring 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 the infrared spectrometer exists in the industry, evaluation is carried out on the basis of the test result of the infrared spectrometer at home, and the test instrument is monitored regularly according to the evaluation value.
First, a testing principle of an infrared spectrometer is briefly introduced, as shown in fig. 1, which is a schematic diagram of the testing principle of the infrared spectrometer, a common epitaxy is a single-layer epitaxy structure, and if an epitaxy thickness needs to be accurately measured, an epitaxy layer with a low doping concentration needs to be deposited on a substrate wafer with a high doping concentration, and measurement is performed by using an infrared reflection measurement technology. For the accuracy of measurement, it is required that the resistivity of the high-concentration substrate layer should be less than 0.02 Ω · cm, since the test mechanism is to make infrared spectrum pass through michelson interferometer and then enter the silicon epitaxial surface, and calculate the thickness of the epitaxial layer by analyzing the interference pattern formed by the reflected light of infrared spectrum on the epitaxial surface and the substrate surface, respectively. The lightly doped epitaxial layer is relatively transparent to the infrared spectrum of wavelengths in the range of 2.5 μm to 50 μm, but the heavily doped substrate acts as a reflective surface for this range, so infrared reflection techniques can be used to determine the thickness of the epitaxial layer.
Since the accuracy of the infrared spectrometer cannot be determined after the infrared spectrometer is used for a period of time, it is impossible to determine when the infrared spectrometer needs to be calibrated and how to calibrate the infrared spectrometer. Accordingly, a method for calibrating an infrared spectrometer is needed.
Before describing the calibration method, the calibration sheet provided by the present invention and the preparation process of the calibration sheet will be described.
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 center thickness of the substrate of the standard epitaxial wafer in each group is the same as that of the reference substrate in the group before the epitaxial process is not carried out. The central thickness of the substrate reference wafer of each group of standard wafers and the central thickness of the substrate of the epitaxial standard wafer are tested by adopting an ADE flatness tester through a CNAS calibration qualified mechanism. Other calibrated flatness testers may also be used for testing, and are not limited herein. The ADE flatness tester is introduced in this application.
The traceability is realized by arranging at least one substrate reference wafer and at least one epitaxial standard wafer in each group of standard wafers. If the substrate reference wafer is not arranged and only the epitaxial standard wafer is arranged, the epitaxial standard wafer cannot be restored to the state before epitaxy after growth and epitaxy, once the level of the ADE flatness tester changes, the thickness of the epitaxial standard wafer also changes, and whether the thickness of the epitaxial standard wafer is caused by the change of the epitaxial standard wafer or the non-leveling of the ADE flatness tester cannot be determined, so that the substrate reference wafer 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 with measurement qualification for calibration at any time, and whether the epitaxial standard wafer is worn or not can be determined and can be continuously used for calibration or not.
After a plurality of groups of substrates with the same center thickness are selected from the substrates, at least 2 substrates are provided in each group, the center thicknesses of all the substrates in each group are required to be the same, and the center thicknesses of the substrates in different groups can be the same or different, which 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 epitaxy thickness of each group of substrates is different. The multiple groups of standard wafers comprise an epitaxial standard wafer with the minimum thickness which can be measured by the infrared spectrometer and an epitaxial standard wafer with the maximum thickness which can be measured by the infrared spectrometer. The thickness of each group of epitaxial standard wafers can be prepared one by one at intervals of 5 mu m on the basis of the epitaxial standard wafer with the minimum thickness which can be measured by the infrared spectrometer until the maximum thickness of the infrared spectrometer to be calibrated on the energy side is 150 mu m-200 mu m.
For each group of standard wafers, firstly, an ADE flatness tester calibrated by a CNAS calibration mechanism is selected to test the thickness of the epitaxial standard wafers in each group of standard wafers, and the thickness is marked as B 1 、B 2 、B 3 、B 4 8230the thickness of the substrate reference sheet in each set of standard sheets was measured using the calibrated ADE flatness tester and is designated A 1 、A 2 、A 3 、A 4 823060, and the thickness of the standard epitaxial wafer in each group of standard wafers is marked as B 1 -A 1 、B 2 -A 2 、B 3 -A 3 、B 4 -A 4 \8230, (8230); for convenience of later calculation, B is 1 -A 1 、B 2 -A 2 、B 3 -A 3 、B 4 -A 4 \823060: \8230notedY 1 、Y 2 、Y 3 、Y 4 ……。
Then, an infrared spectrometer is adopted to test the thickness of the epitaxial standard wafers in each group of standard wafers, and the thickness is recorded as X 1 、X 2 、X 3 、X 4 ……。
Finally, using X 1 、X 2 、X 3 、X 4 823060 1 、Y 2 、Y 3 、Y 4 \8230, and linear fitting to obtain linear equation Y = aX + b, calculating values a and b, and writing a and b into the linear equation in the test program of the infrared spectrometer. The independent variable in the fitting linear equation is the second epitaxial thickness obtained through the test of the infrared spectrometer, and the dependent variable in the fitting linear equation is the first epitaxial thickness obtained through the test of the calibrated ADE flatness tester.
After the linear equation in the test program of the infrared spectrometer machine is determined and the plurality of calibration sheets are prepared, the calibration sheets can be used for judging whether the infrared spectrometer needs to be calibrated or not after the infrared spectrometer is used for a period of time.
It should be noted that the test of the thickness of the epitaxial wafer and the substrate wafer is not limited to the ADE flatness tester.
The following mainly describes a calibration method for measuring the thickness of an epitaxial layer by an infrared spectrometer provided by the embodiment of the invention. Referring to fig. 2, it shows a flowchart of an implementation of the calibration method for measuring the thickness of the epitaxial layer by using the infrared spectrometer provided by the embodiment of the present invention, which is detailed as follows:
and step 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 plurality of standard epitaxial wafers with different epitaxial thicknesses may include a plurality of epitaxial wafers with gradually changed epitaxial thicknesses, or may be a plurality of epitaxial wafers with different epitaxial thicknesses prepared according to a preset thickness. The device also comprises an epitaxial standard wafer with the minimum thickness which can be measured by the infrared spectrometer, and an epitaxial standard wafer with the maximum thickness which can be measured by the infrared spectrometer.
For example, preparing one epitaxial standard wafer every 5 μm on the basis of the minimum thickness which can be measured by the infrared spectrometer until the maximum thickness of 150 μm-200 μm on the energy side of the infrared spectrometer to be calibrated is reached.
Step S220, determining the fitting thickness of the target standard wafer based on the actually measured epitaxial thickness of the target standard wafer and a preset fitting linear equation of the 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, 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 a difference between the first initial thickness and the second standard thickness. The first initial thickness is the thickness which is 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 of the target standard wafer tested by the infrared spectrometer for the first time after the epitaxial preparation of the target standard wafer is completed.
After determining the values of a and b in the fitted linear equation Y = aX + b, 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 in detail here.
And after the actual measurement epitaxial thickness of the target standard wafer is obtained, the actual measurement epitaxial thickness of the target standard wafer is brought into a fitting linear equation, and the fitting thickness of the target standard wafer can be obtained.
And step S230, when the difference value between the fitting thickness of the target standard wafer and the first epitaxial thickness of the target standard wafer is larger than a first preset threshold value, calibrating the infrared spectrometer by using the target standard wafer.
After the first epitaxial thickness of the target standard wafer is the target epitaxial standard wafer, testing the thickness B of the target epitaxial standard wafer by using a calibrated flatness tester 1 And testing the thickness A of the substrate reference wafer of the target epitaxial standard wafer by using the calibrated flatness tester 1 Difference value B of 1 -A 1 And the residual value is used as one of the judgment standards for subsequently judging whether the infrared spectrometer needs to be calibrated.
And comparing the difference value of the fitting thickness of the target standard wafer and the first epitaxial thickness of the target standard wafer with a preset threshold value to determine whether the infrared spectrometer needs to be calibrated.
In addition, since the epitaxial standard wafer is often used for calibrating the infrared spectrometer and is also worn or deformed, 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 standard epitaxial wafer meets the requirements of the calibration wafer, verifying by using a substrate reference wafer corresponding to the standard epitaxial wafer. The epitaxial standard wafers and the substrate reference wafers in each group of standard wafers can be periodically sent to a measurement center with calibration qualification every year, and a flatness tester is adopted to test the center thickness of the epitaxial standard wafers and the substrate reference wafers.
If the center thickness of the epitaxial standard wafer is measured by adopting a flatness tester to be C 1 And the central thickness of the substrate reference sheet is measured by the flatness tester to be D 1 If the epitaxial thickness of the standard epitaxial wafer at the current moment is C 1 -D 1 When C is present 1 -D 1 With the remaining first epitaxial thickness B of the set of calibration plates 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 existing epitaxial thickness gauge has no international standard can be overcome, 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.
It should be noted that the test of the thickness of the epitaxial wafer and the substrate wafer is not limited to the ADE flatness tester. The epitaxial layer thickness measured by the flatness tester is not limited to the calibration of an infrared spectrometer and can be used for evaluating the accuracy of the thickness nonuniformity of the epitaxial layer measured by the infrared spectrometer.
The following description will be given by taking a specific example as an example:
the linear fitting equation obtained from the test results of 25 sets of calibration sheets is: y =1.0109X-0.3188, the independent variable being the second epitaxial thickness measured by the infrared spectrometer, and the dependent variable in the fitted linear equation being the first epitaxial thickness measured by the calibrated ADE flatness tester. The preparation process of each set of standard tablets is not described in detail herein.
Then, 7 sets of calibration sheets are used for calibrating the infrared spectrometer, 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 the infrared spectrometer, and the vertical axis is the first epitaxial thickness retained by each set of calibration sheets.
TABLE 1 calibration data
In this example, d'/d-1 is not more than. + -. 0.3%, and it can be said that the infrared tester is stable and free from abnormality, and calibration is not required.
However, if d '/d-1 exceeds. + -. 0.3%, the infrared spectrometer is deemed to be calibrated and the calibration is performed with the calibration plate until d'/d-1 does not exceed. + -. 0.3%.
The calibration method for measuring the thickness of the epitaxial layer by the infrared spectrometer comprises the steps of firstly, measuring the actual measurement epitaxial thickness of a target standard wafer by the infrared spectrometer, and then determining the fitting thickness of the target standard wafer based on the actual measurement epitaxial thickness of the target standard wafer and a preset fitting linear equation of the infrared spectrometer. And finally, when the difference value between the fitting thickness of the target standard wafer and the first epitaxial thickness of the target standard wafer is larger than a first preset threshold value, calibrating the infrared spectrometer by using the target standard wafer. And comparing the fitting thickness of the target standard plate obtained by fitting the preset fitting linear equation of the infrared spectrometer with the first epitaxial thickness of the target standard plate to determine whether the infrared spectrometer needs to be calibrated, and if the fitting thickness of the target standard plate is larger than a preset threshold value, calibrating the infrared spectrometer by using the target standard plate. Therefore, the problem that the existing infrared spectrometer has no definite calibration standard can be effectively solved.
It should be understood that, the sequence numbers of the steps in the foregoing embodiments do not imply an execution sequence, and the execution sequence of each process should be determined by functions and internal logic of the process, and should not limit the implementation process of the embodiments of the present invention in any way.
The above-mentioned embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present 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 solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the embodiments of the present invention, and they should be construed as being included therein.
Claims (10)
1. A calibration method for measuring the thickness of an epitaxial layer by an infrared spectrometer is characterized by comprising the following steps:
measuring the actually measured epitaxial thickness of a target standard wafer by using 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 wafer based on the actually measured epitaxial thickness of the target standard wafer and a preset fitting linear equation of the infrared spectrometer; the fitting linear equation is obtained by fitting based on first epitaxial thicknesses of a plurality of epitaxial standard wafers with different epitaxial thicknesses and second epitaxial thicknesses of the plurality of epitaxial standard wafers with different epitaxial thicknesses, the first epitaxial thicknesses are obtained by testing through a calibrated flatness tester, and the second epitaxial thicknesses are obtained by testing through the infrared spectrometer;
and when the difference value between the fitting thickness of the target standard wafer and the first epitaxial thickness of the target standard wafer is larger than a first preset threshold value, calibrating the infrared spectrometer by using the target standard wafer.
2. The calibration method according to claim 1, wherein each epitaxial standard wafer with different epitaxial thicknesses is provided with a substrate reference wafer, and each epitaxial standard wafer is equal to the central thickness of the corresponding substrate reference wafer when the epitaxial preparation process is not carried out;
the calibration method further comprises:
testing the thickness of the target standard sheet by using a calibrated flatness tester, and recording as a first standard thickness;
testing the thickness of the substrate reference sheet of the target standard sheet by using a calibrated flatness tester, and recording the thickness as a second standard thickness;
recording the difference value of the first standard thickness and the second standard thickness as the measured 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.
3. The calibration method of claim 2, 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 which is tested by a calibrated flatness tester for the first time after the epitaxial preparation of the target standard wafer is finished;
and the second epitaxial thickness is the thickness of the first time of testing by adopting the infrared spectrometer after the epitaxial preparation of the target standard wafer is finished.
4. The calibration method of claim 1, wherein the independent variable in the fitted linear equation is the second epitaxial thickness measured by the infrared spectrometer and the dependent variable in the fitted linear equation is the first epitaxial thickness measured by the calibrated flatness tester.
5. The calibration method according to claim 4, wherein the coefficients and the deviations in the fitted linear equation are the same as the coefficients and the deviations, respectively, of the linear equation in the test program of the infrared spectrometer.
6. The calibration method of claim 4, wherein determining the fitted thickness of the target standard plate based on the measured epitaxial thickness of the target standard plate and a preset fitted linear equation of the infrared spectrometer comprises:
and inputting the epitaxial thickness of the target standard wafer into the fitting linear equation to obtain the fitting thickness of the target standard wafer.
7. The calibration method of claim 1, wherein the plurality of epitaxial standard wafers of different epitaxial thicknesses comprises a plurality of epitaxial wafers of graded epitaxial thicknesses.
8. The calibration method of claim 7, wherein the plurality of epitaxial standard wafers of different epitaxial thicknesses includes an epitaxial standard wafer of a minimum thickness that the infrared spectrometer can measure and also includes an epitaxial standard wafer of a maximum thickness that the infrared spectrometer can measure.
9. A calibration sheet for calibrating the thickness of an epitaxial layer measured by an infrared spectrometer is characterized by comprising a plurality of groups of standard sheets,
each group of standard wafers at least comprises two substrates with the same center thickness, wherein one substrate is used as a substrate reference wafer, and the other substrate is used for preparing epitaxy with a preset thickness on the substrate and is used as an epitaxy standard wafer; and the epitaxial thicknesses of the epitaxial standard wafers in each group of standard wafers are different.
10. The calibration sheet of claim 9, wherein the plurality of sets of standard sheets include an epitaxial standard sheet with a minimum thickness measurable by the infrared spectrometer and an epitaxial standard sheet with a maximum thickness measurable by the infrared spectrometer.
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| US6573999B1 (en) * | 2000-07-14 | 2003-06-03 | Nanometrics Incorporated | Film thickness measurements using light absorption |
| CN101403604A (en) * | 2008-10-22 | 2009-04-08 | 中国科学院上海技术物理研究所 | Extension thin film surface protection test technology |
| CN102376534A (en) * | 2010-08-26 | 2012-03-14 | 上海华虹Nec电子有限公司 | Manufacturing method of standard sheet for silicon epitaxial film thickness test |
| JP2018182211A (en) * | 2017-04-19 | 2018-11-15 | 株式会社Sumco | Measuring method for epitaxial layer thickness of epitaxial silicon wafer, and manufacturing method of epitaxial silicon wafer |
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