阅读说明：本技术 一种外延片厚度测量方法及测量系统 (Epitaxial wafer thickness measuring method and system ) 是由 张凌云 金柱炫 于 2020-05-25 设计创作，主要内容包括：本公开提供了一种外延片厚度测量方法及测量系统,该外延片厚度测量方法通过傅里叶红外变换光谱分析仪来测定待测外延片的厚度,所述方法包括：根据所述待测外延片的厚度范围值,选择参考外延片,参考外延片与待测外延片的性能参数的各参数差值小于或等于阈值,性能参数包括电阻率、掺杂浓度、表面性质；设定傅里叶红外变换光谱分析仪的配方参数；傅里叶红外变换光谱分析仪测量得到参考外延片的参考光谱图及待测外延片的样品光谱图,以获取对照光谱图；根据配方参数确定对照光谱图中的特征波段,进行分析计算,得到待测外延片的厚度测定结果。本公开提供的外延片厚度测量方法及测量系统,能够提高测量结果准确性,可实现对大尺寸外延片厚度测量。(The invention provides an epitaxial wafer thickness measuring method and a measuring system, wherein the epitaxial wafer thickness measuring method is used for measuring the thickness of an epitaxial wafer to be measured through a Fourier infrared conversion spectrum analyzer, and the method comprises the following steps: selecting a reference epitaxial wafer according to the thickness range value of the epitaxial wafer to be tested, wherein the difference value of each parameter of the performance parameters of the reference epitaxial wafer and the epitaxial wafer to be tested is less than or equal to a threshold value, and the performance parameters comprise resistivity, doping concentration and surface property; setting the formula parameters of a Fourier infrared conversion spectrum analyzer; measuring by a Fourier infrared transform spectrum analyzer to obtain a reference spectrogram of a reference epitaxial wafer and a sample spectrogram of an epitaxial wafer to be detected so as to obtain a reference spectrogram; and determining the characteristic wave band in the reference spectrogram according to the formula parameters, and performing analysis calculation to obtain the thickness measurement result of the epitaxial wafer to be measured. The epitaxial wafer thickness measuring method and the epitaxial wafer thickness measuring system can improve the accuracy of the measuring result and can realize the thickness measurement of the large-size epitaxial wafer.)

1. An epitaxial wafer thickness measuring method is characterized in that the method is used for measuring the thickness of an epitaxial wafer to be measured through a Fourier infrared transform spectrum analyzer, and the method comprises the following steps:

selecting a reference epitaxial wafer according to the thickness range value of the epitaxial wafer to be tested, wherein the difference value of each parameter of the performance parameters of the reference epitaxial wafer and the epitaxial wafer to be tested is less than or equal to a threshold value, and the performance parameters comprise resistivity, doping concentration and surface property;

setting the formula parameters of the Fourier infrared transformation spectrum analyzer;

the Fourier infrared conversion spectrum analyzer measures to obtain a reference spectrogram of the reference epitaxial wafer and a sample spectrogram of the epitaxial wafer to be detected so as to obtain a reference spectrogram;

and determining a characteristic wave band in the comparison spectrogram according to the formula parameters, and performing analysis calculation to obtain a thickness measurement result of the epitaxial wafer to be measured.

2. The epitaxial wafer thickness measurement method of claim 1,

according to the method, when a reference epitaxial wafer is selected according to the thickness range value of the epitaxial wafer to be tested, the epitaxial wafer to be tested and the reference epitaxial wafer meet the following preset relation:

when the thickness n of the epitaxial layer to be tested is greater than or equal to 0.3 mu m and less than or equal to 2 mu m, selecting the thickness of the reference epitaxial wafer to be greater than or equal to 10 mu m;

and when the thickness n of the epitaxial layer to be measured is greater than 2 μm, selecting the thickness Ref of the reference epitaxial wafer as Ref ═ n +/-10 μm, or Ref ═ 0.

3. The epitaxial wafer thickness measurement method of claim 1,

in the method, setting the formula parameters of the Fourier infrared transform spectrum analyzer specifically comprises the following steps:

the formula parameters comprise: a center peak exclusion window, a reference edge peak exclusion window, and an edge peak minimum height; setting the width of the central peak exclusion window to be larger than the width of the whole peak of the central peak of the comparison spectrogram, setting the width of the reference edge peak exclusion window to be larger than the width of the whole peak of the edge peak in the reference spectrogram, and setting the signal intensity of the minimum height of the edge peak to be larger than the signal intensity of the minimum height of the edge peak in the comparison spectrogram.

4. The epitaxial wafer thickness measurement method of claim 1,

in the method, the scanning mode of the Fourier infrared transform spectrum analyzer is as follows: and scanning at least 9 sampling points on the epitaxial wafer to be tested, wherein each sampling point is scanned for at least 5 times.

5. The epitaxial wafer thickness measurement method of claim 1,

before the fourier infrared transform spectrum analyzer measures and obtains the reference spectrogram of the reference epitaxial wafer and the sample spectrogram of the epitaxial wafer to be measured, the method further comprises the following steps:

correcting the Fourier infrared conversion spectrum analyzer, and specifically comprises the following steps:

when the 'correction test' option of the Fourier infrared conversion spectrum analyzer is not checked, a reference standard epitaxial wafer for correction is adopted, and the thickness value of the reference standard epitaxial wafer for correction is measured under the condition that the Fourier infrared conversion spectrum analyzer is set to be the formula parameter;

correcting against a standard reference plate authentication value by using a linear equation f (x) ax + b, wherein a is a linear value and b is a constant term;

and after the correction is finished, checking a correction test option to measure the thickness of the epitaxial wafer to be measured.

6. The epitaxial wafer thickness measurement method of claim 1,

in the method, the fourier-infrared-transform spectrum analyzer measures a reference spectrogram of the reference epitaxial wafer and a sample spectrogram of the epitaxial wafer to be measured, and specifically includes:

the Fourier infrared conversion spectrum analyzer pre-stores reference spectrogram data of the reference epitaxial wafer with different thicknesses, measures a sample spectrogram of the epitaxial wafer to be detected, and obtains the reference spectrogram according to the pre-stored reference spectrogram data and the sample spectrogram of the epitaxial wafer to be detected.

7. The epitaxial wafer thickness measurement method of claim 6,

the method further comprises the following steps: and updating the spectrogram data of the reference epitaxial wafer, which is prestored in the Fourier infrared transformation spectrum analyzer, before measuring the thickness of the epitaxial wafer to be measured.

8. The method for measuring the thickness of the epitaxial wafer according to claim 2, further comprising verifying the thickness measurement result of the epitaxial wafer to be measured after obtaining the thickness measurement result of the epitaxial wafer, specifically comprising:

selecting an epitaxial wafer sample wafer with a known thickness, a first reference epitaxial wafer and a second reference epitaxial wafer, wherein the thickness of the first reference epitaxial wafer and the thickness of the epitaxial wafer sample wafer meet the preset relationship, and the thickness of the second reference epitaxial wafer and the thickness of the epitaxial wafer sample wafer do not meet the preset relationship;

measuring to obtain a first reference spectrogram of the first reference epitaxial wafer and the epitaxial wafer sample wafer according to the set formula parameters by the Fourier infrared transform spectrum analyzer, and analyzing and calculating the first reference spectrogram to obtain a first thickness measurement result of the epitaxial wafer sample wafer;

measuring a second reference spectrogram of the second reference epitaxial wafer and the epitaxial wafer sample wafer according to the set formula parameters by the Fourier infrared transform spectrum analyzer, and analyzing and calculating the second reference spectrogram to obtain a second thickness measurement result of the epitaxial wafer sample wafer;

and comparing and analyzing the first thickness measurement result and the second thickness measurement result to verify the reliability of the thickness measurement result of the epitaxial wafer to be tested.

9. The epitaxial wafer thickness measurement method of any one of claims 1 to 8,

the diameter size range of the epitaxial wafer to be measured is 150-450 mm.

10. An epitaxial wafer thickness measurement system, comprising a fourier-ir transform spectrum analyzer, the fourier-ir transform spectrum analyzer comprising:

the reference epitaxial wafer selection unit is used for selecting a reference epitaxial wafer according to the thickness range value of the epitaxial wafer to be tested, wherein the difference value of each parameter of the performance parameters of the reference epitaxial wafer and the epitaxial wafer to be tested is smaller than or equal to a threshold value, and the performance parameters comprise resistivity, doping concentration and surface property;

the formula parameter setting unit is used for setting formula parameters;

the measuring unit is used for measuring and obtaining a reference spectrogram of the reference epitaxial wafer and a sample spectrogram of the epitaxial wafer to be measured so as to obtain a comparison spectrogram;

and the processor is used for determining the characteristic wave band in the comparison spectrogram according to the formula parameters, and performing analysis calculation to obtain the thickness measurement result of the epitaxial wafer to be measured.

Technical Field

The invention relates to the technical field of semiconductors, in particular to a method and a system for measuring the thickness of an epitaxial wafer.

Background

Epitaxy is a technique of depositing a thin layer of ordered single crystal silicon on a polished single crystal substrate according to the crystal orientation of the substrate, the newly grown single crystal layer is an epitaxial layer, and the substrate with the epitaxial layer is called an epitaxial wafer.

Epitaxial wafers have higher wafer quality than polished wafers because they grow a single crystal silicon thin film on a polished wafer substrate by chemical deposition under vacuum conditions that is free of defects and impurities, eliminating surface and bulk defects introduced by the polished wafer during crystal growth and machining. The epitaxial wafer is mainly applied to devices with precise characteristics and small size. Therefore, the wafer quality is very demanding, and the key index of the epitaxial wafer quality is the uniformity control of the epitaxial layer thickness and resistivity.

In order to characterize the uniformity of the epitaxial layer, it is very important to obtain the thickness of the epitaxial layer through simple and efficient measurement. In addition, as the demand for product yield and profit margin of the chip industry is increasing, the size demand of the epitaxial wafer is also increasing. Therefore, the epitaxial wafer tends to be produced in a large size, so that the utilization rate of chip production can be improved, the cost is saved, and the profit is improved.

In the related art, the currently adopted epitaxial wafer thickness measurement method has different degrees of defects:

1. the existing epitaxial wafer measuring method has the defects that the measuring result is inaccurate along with the fact that the thickness of an epitaxial wafer is thinner and thinner;

2. for large-size epitaxial wafers, especially 300mm (12 inch) epitaxial wafers, no related technology exists for the thickness measurement method.

Disclosure of Invention

The embodiment of the disclosure provides a method and a system for measuring the thickness of an epitaxial wafer, which can improve the accuracy of a measurement result and can realize the thickness measurement of a large-size epitaxial wafer.

The technical scheme provided by the embodiment of the disclosure is as follows:

the embodiment of the disclosure provides an epitaxial wafer thickness measuring method, which is used for measuring the thickness of an epitaxial wafer to be measured through a Fourier infrared conversion spectrum analyzer, and comprises the following steps:

selecting a reference epitaxial wafer according to the thickness range value of the epitaxial wafer to be tested, wherein the difference value of each parameter of the performance parameters of the reference epitaxial wafer and the epitaxial wafer to be tested is less than or equal to a threshold value, and the performance parameters comprise resistivity, doping concentration and surface property;

setting the formula parameters of the Fourier infrared transformation spectrum analyzer;

the Fourier infrared conversion spectrum analyzer measures to obtain a reference spectrogram of the reference epitaxial wafer and a sample spectrogram of the epitaxial wafer to be detected so as to obtain a reference spectrogram;

and determining a characteristic wave band in the comparison spectrogram according to the formula parameters, and performing analysis calculation to obtain a thickness measurement result of the epitaxial wafer to be measured.

In an exemplary embodiment, in the method, when a reference epitaxial wafer is selected according to the value of the thickness range of the epitaxial wafer to be measured, the epitaxial wafer to be measured and the reference epitaxial wafer satisfy the following predetermined relationship:

when the thickness n of the epitaxial layer to be tested is greater than or equal to 0.3 mu m and less than or equal to 2 mu m, selecting the thickness of the reference epitaxial wafer to be greater than or equal to 10 mu m;

and when the thickness n of the epitaxial layer to be measured is greater than 2 μm, selecting the thickness Ref of the reference epitaxial wafer as Ref ═ n +/-10 μm, or Ref ═ 0.

In an exemplary embodiment, the method for setting the recipe parameters of the fourier-infrared-transform spectrum analyzer specifically includes:

the formula parameters comprise: a center peak exclusion window, a reference edge peak exclusion window, and an edge peak minimum height; wherein the central peak exclusion window is set to be greater than the width of the entire peak of the central peak of the reference spectrogram, the reference edge peak exclusion window is set to be greater than the width of the entire peak of the edge peak in the reference spectrogram, and the signal intensity of the minimum height of the edge peak is set to be greater than the signal intensity of the minimum height of the edge peak in the reference spectrogram.

In an exemplary embodiment, in the method, the scanning mode of the fourier-infrared transform spectrum analyzer is as follows: and scanning at least 9 sampling points on the epitaxial wafer to be tested, wherein each sampling point is scanned for at least 5 times.

Before the fourier-infrared-transform spectrum analyzer measures the reference spectrum of the reference epitaxial wafer and the sample spectrum of the epitaxial wafer to be measured, the method further includes:

correcting the Fourier infrared conversion spectrum analyzer, and specifically comprises the following steps:

when the 'correction test' option of the Fourier infrared conversion spectrum analyzer is not checked, a reference standard epitaxial wafer for correction is adopted, and the thickness value of the reference standard epitaxial wafer for correction is measured under the condition that the Fourier infrared conversion spectrum analyzer is set to be the formula parameter;

correcting against a standard reference plate authentication value by using a linear equation f (x) ax + b, wherein a is a linear value and b is a constant term;

and after the correction is finished, checking a correction test option to measure the thickness of the epitaxial wafer to be measured.

In an exemplary embodiment, in the method, the obtaining, by the fourier-infrared transform spectrometer, a reference spectrogram of the reference epitaxial wafer and a sample spectrogram of the epitaxial wafer to be measured includes:

the Fourier infrared conversion spectrum analyzer pre-stores reference spectrogram data of the reference epitaxial wafer with different thicknesses, measures a sample spectrogram of the epitaxial wafer to be detected, and obtains the reference spectrogram according to the pre-stored reference spectrogram data and the sample spectrogram of the epitaxial wafer to be detected.

Illustratively, the method further comprises: and updating the spectrogram data of the reference epitaxial wafer, which is prestored in the Fourier infrared transformation spectrum analyzer, before measuring the thickness of the epitaxial wafer to be measured.

Illustratively, the method further includes verifying the thickness measurement result of the epitaxial wafer to be measured after obtaining the thickness measurement result of the epitaxial wafer, and specifically includes:

selecting an epitaxial wafer sample wafer with a known thickness, a first reference epitaxial wafer and a second reference epitaxial wafer, wherein the thickness of the first reference epitaxial wafer and the thickness of the epitaxial wafer sample wafer meet the preset relationship, and the thickness of the second reference epitaxial wafer and the thickness of the epitaxial wafer sample wafer do not meet the preset relationship;

measuring to obtain a first reference spectrogram of the first reference epitaxial wafer and the epitaxial wafer sample wafer according to the set formula parameters by the Fourier infrared transform spectrum analyzer, and analyzing and calculating the first reference spectrogram to obtain a first thickness measurement result of the epitaxial wafer sample wafer;

measuring a second reference spectrogram of the second reference epitaxial wafer and the epitaxial wafer sample wafer according to the set formula parameters by the Fourier infrared transform spectrum analyzer, and analyzing and calculating the second reference spectrogram to obtain a second thickness measurement result of the epitaxial wafer sample wafer;

and comparing and analyzing the first thickness measurement result and the second thickness measurement result to verify the reliability of the thickness measurement result of the epitaxial wafer to be tested.

Illustratively, the diameter size range of the epitaxial wafer to be tested is 150-450 mm.

The embodiment of the present disclosure further provides an epitaxial wafer thickness measurement system, including fourier infrared transform spectrum analyzer, fourier infrared transform spectrum analyzer includes:

the reference epitaxial wafer selection unit is used for selecting a reference epitaxial wafer according to the thickness range value of the epitaxial wafer to be tested, wherein the difference value of each parameter of the performance parameters of the reference epitaxial wafer and the epitaxial wafer to be tested is smaller than or equal to a threshold value, and the performance parameters comprise resistivity, doping concentration and surface property;

the formula parameter setting unit is used for setting formula parameters;

the measuring unit is used for measuring and obtaining a reference spectrogram of the reference epitaxial wafer and a sample spectrogram of the epitaxial wafer to be measured so as to obtain a comparison spectrogram;

and the processor is used for determining the characteristic wave band in the comparison spectrogram according to the formula parameters, and performing analysis calculation to obtain the thickness measurement result of the epitaxial wafer to be measured.

The beneficial effects brought by the embodiment of the disclosure are as follows:

according to the epitaxial wafer thickness measuring method and the epitaxial wafer thickness measuring system, the corresponding reference epitaxial wafer is selected according to the thickness range value of the epitaxial wafer to be measured, the characteristic wave band of the reference spectrogram is selected by setting the formula parameters of the Fourier infrared conversion spectrum analyzer, and therefore analysis and calculation are carried out according to the reference epitaxial wafer and the reference spectrogram of the epitaxial wafer to be measured, and the thickness of the epitaxial wafer to be measured is determined. The measuring method is rapid, convenient and accurate in measuring result, overcomes the defect that the thickness of the epitaxial wafer, especially the thickness of the epitaxial wafer with very thin thickness (for example, the thickness is 0.3-2 microns), is inaccurate in measuring in the prior art, is reliable in measuring result, is beneficial to efficient production, is beneficial to saving production cost of enterprises, and increases profits; the measurement method and the measurement system provided by the embodiment of the disclosure can be applied to the thickness measurement of epitaxial wafers with various sizes, and particularly, can be applied to the thickness measurement of large-size epitaxial wafers (for example, epitaxial wafers with the diameter size of 300mm or more than 300 mm), thereby solving the technical problem that the thickness measurement of the large-size epitaxial wafers cannot be performed in the prior art.

Drawings

Fig. 1 shows a schematic flow chart of an epitaxial wafer thickness measurement method provided in an embodiment of the present disclosure.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present disclosure more apparent, the technical solutions of the embodiments of the present disclosure will be described clearly and completely with reference to the drawings of the embodiments of the present disclosure. It is to be understood that the described embodiments are only a few embodiments of the present disclosure, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the disclosure without any inventive step, are within the scope of protection of the disclosure.

Unless otherwise defined, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure belongs. The use of "first," "second," and similar terms in this disclosure is not intended to indicate any order, quantity, or importance, but rather is used to distinguish one element from another. Also, the use of the terms "a," "an," or "the" and similar referents do not denote a limitation of quantity, but rather denote the presence of at least one. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.

Before the detailed description of the epitaxial wafer measurement method and the measurement system provided by the embodiments of the present disclosure, the following description is necessary for the related art:

in the related art, the thickness measurement result of the epitaxial wafer in the currently known epitaxial wafer thickness measurement method is inaccurate, especially for the epitaxial wafer with very thin thickness and large size. For example, there is a conventional method for measuring the thickness of an epitaxial wafer by reflection interference analysis using a fourier transform infrared spectrophotometer, which includes the steps of: preparing a semiconductor substrate; stacking an epitaxial wafer as a measurement object on a semiconductor substrate, and measuring an interferogram of the measurement object and an interferogram of the semiconductor substrate to obtain a reference interferogram by using the fourier transform infrared spectrophotometer; calculating a sample spectrum of the measurement object and a reference spectrum of the semiconductor substrate by performing fourier transform on the interferogram of the measurement object and the reference interferogram, respectively; the thickness of the measurement object is obtained by analyzing the sample spectrum and the reference spectrum. In the measurement method, the spectrum of the semiconductor substrate is used as a reference spectrum, and as the epitaxial wafer is thinner and thinner, the central peak (centerburst) and the edge peak (sideburst) on the sample spectrogram are closer and closer, so that the measurement result of the thickness of the thin layer is inaccurate. Therefore, the method overcomes the defects of the prior art method, conforms to the market trend, and focuses on solving the method for measuring the thickness of the epitaxial thin layer. In addition, in the related art, a method for testing the thickness of a large-size epitaxial wafer, for example, an epitaxial wafer with a diameter of 300mm, is not described, and therefore, how to improve the accuracy of the measurement result of the thickness of the epitaxial wafer and how to measure the thickness of the large-size epitaxial wafer are technical problems which need to be solved urgently.

In order to solve the above technical problem, embodiments of the present disclosure provide an epitaxial wafer thickness measurement method and an epitaxial wafer measurement system, which can improve the accuracy of epitaxial wafer thickness measurement and can be suitable for large-size epitaxial wafer thickness measurement.

According to the method for measuring the thickness of the epitaxial wafer, the thickness of the epitaxial wafer to be measured is measured through a Fourier Transform Infrared Spectrometer (FTIR).

The Fourier infrared conversion spectrum analyzer mainly comprises an infrared light source, a beam splitter, an interferometer, a sample cell, a detector, a computer data processing system, a recording system and the like, is a typical representative of an interference infrared spectrometer, is different from the working principle of a dispersion infrared spectrometer, does not have a monochromator and a slit, obtains an interferogram of incident light by utilizing a Michelson interferometer, and then converts a time domain function interferogram into a frequency domain function graph (an infrared spectrogram) through Fourier mathematical conversion. The Fourier transform infrared spectrometer mainly comprises a Michelson interferometer and a computer. The michelson interferometer has the main function of dividing light emitted by a light source into two beams to form a certain optical path difference, and then combining the beams to generate interference, wherein the obtained interference pattern function contains all frequency and intensity information of the light source. The distribution of the intensity of the original light source according to the frequency can be calculated by using a computer to carry out Fourier transform on the interferogram function. The method overcomes the defects of low resolving power, small light energy output, narrow spectral range, long measuring time and the like of the dispersion type spectrometer. It can not only measure the absorption and reflection spectrum of various gas, solid and liquid samples, but also can be used for short-time chemical reaction measurement. At present, the infrared spectrometer is widely applied to the fields of electronics, chemical engineering, medicine and the like.

(1) Light source: the fourier transform infrared spectrum analyzer is provided with a plurality of light sources for measuring spectra in different ranges. Tungsten filament or iodine tungsten lamps (near infrared), silicon carbon rods (mid infrared), high pressure mercury lamps and thoria lamps (far infrared) are commonly used. In the fourier transform infrared spectrum analyzer used in the method for measuring the thickness of the epitaxial wafer provided by the embodiment of the disclosure, the adopted light source is an infrared ceramic light source.

(2) A beam splitter: the beam splitter is a key element of the michelson interferometer. The function is to divide the incident beam into two parts of reflection and transmission, then to make it compound, if the movable mirror makes the two beams to create a certain optical path difference, the compound beam can create constructive or destructive interference.

The requirements for the beam splitter are: the incident beam should be transmitted and reflected half-way at wavenumber v, when the amplitude of the modulated beam is at a maximum. According to different use wave band ranges, corresponding surface coatings are added on different medium materials to form the beam splitter.

(3) A detector: detectors used in fourier transform infrared spectrometers are typically titanium Triglyphnate (TGS), barium strontium niobate, mercury cadmium telluride, indium antimonide, and the like. In the fourier transform infrared spectrometer used in the method for measuring the thickness of the epitaxial wafer provided by the embodiment of the disclosure, the adopted detector is a DTGS detector, the DTGS detector is an infrared detector manufactured by utilizing the characteristic that the polarization of triglycine sulfate crystal (TGS for short) changes along with the temperature, and the infrared detector is called as a DTGS detector after being subjected to deuteration treatment. The DTGS detector includes a KRS-5 window (thallium bromide iodide infrared window) and a KBr (potassium bromide) spectroscope in the spectrometer.

(4) A data processing system: the core of the data processing system of the Fourier transform infrared spectrometer is a computer, and the data processing system has the functions of controlling the operation of the instrument, collecting data and processing the data.

As shown in the drawings, the method for measuring the thickness of the epitaxial wafer provided by the embodiment of the disclosure includes the following steps:

step S01, selecting a reference epitaxial wafer (Referencewafer) according to the thickness range value of the epitaxial wafer to be tested, wherein the difference value of each parameter of the performance parameters of the reference epitaxial wafer and the epitaxial wafer to be tested is less than or equal to a threshold value, and the performance parameters comprise resistivity, doping concentration and surface property;

step S02, setting Recipe parameters (Recipe) of the Fourier transform infrared spectrum analyzer;

step S03, the Fourier infrared conversion spectrum analyzer measures and obtains a reference spectrogram of the reference epitaxial wafer and a sample spectrogram of the epitaxial wafer to be measured so as to obtain a reference spectrogram;

and step S04, determining the characteristic wave band in the comparison spectrogram according to the formula parameters, and performing analysis calculation to obtain the thickness measurement result of the epitaxial wafer to be measured.

According to the epitaxial wafer thickness measuring method provided by the embodiment of the disclosure, the thickness of the epitaxial wafer is measured through the Fourier infrared conversion spectrum analyzer, firstly, according to the thickness range value of the epitaxial wafer to be measured, a reference epitaxial wafer with a corresponding thickness is selected according to a certain corresponding relation, then, the characteristic wave band of a reference spectrogram is selected by setting the formula parameters of the Fourier infrared conversion spectrum analyzer, and therefore, the analysis calculation is carried out according to the reference spectrograms of the reference epitaxial wafer and the epitaxial wafer to be measured, and the thickness of the epitaxial wafer to be measured is determined. The measuring method is rapid, convenient and accurate in measuring result, overcomes the defect that the thickness of the epitaxial wafer, especially the thickness of the epitaxial wafer with very thin thickness (for example, the thickness is 0.3-2 microns), is inaccurate in measuring in the prior art, is reliable in measuring result, is beneficial to efficient production, is beneficial to saving production cost of enterprises, and increases profits; in addition, the method for measuring the thickness of the epitaxial wafer provided by the embodiment of the disclosure can be applied to the thickness of epitaxial wafers with various sizes, for example, epitaxial wafers with the diameter size of 150-450 mm, and it should be particularly noted that the method for measuring the thickness of the epitaxial wafer provided by the embodiment of the disclosure can be applied to the thickness measurement of large-size epitaxial wafers (for example, large-size epitaxial wafers with the diameter size of 300mm or above 300 mm), thereby solving the technical problem that the thickness measurement of the large-size epitaxial wafer cannot be performed in the prior art.

The method for measuring the thickness of the epitaxial wafer provided by the embodiment of the disclosure is explained in more detail below.

In an embodiment provided by the present disclosure, in step S01, different thicknesses of the reference epitaxial wafer are selected for the to-be-tested epitaxial wafers with different thicknesses, and specifically, the to-be-tested epitaxial wafer and the reference epitaxial wafer satisfy the following predetermined relationship:

when the thickness n of the epitaxial layer to be tested is greater than or equal to 0.3 mu m and less than or equal to 2 mu m, selecting the thickness of the reference epitaxial wafer to be greater than or equal to 10 mu m;

and when the thickness n of the epitaxial layer to be measured is greater than 2 μm, selecting the thickness Ref of the reference epitaxial wafer as Ref ═ n +/-10 μm, or Ref ═ 0.

According to the scheme, under the condition that no problem exists in FTIR machine hardware equipment and light source facilities, the main factor influencing the thickness measurement result is the selection of the reference epitaxial wafer, and the reference epitaxial wafer is used as a reference, so that the performance parameters of the reference epitaxial wafer are as follows: the difference value of each parameter of the resistivity, the doping concentration, the surface property and the like is less than or equal to the threshold value, namely, the performance parameter of the reference epitaxial wafer is consistent with the epitaxial wafer to be measured as far as possible, so that the influence of other interference factors on the measurement thickness result can be eliminated, and the accuracy of the measurement result is improved.

In addition, in the above scheme, the reference epitaxial wafers with different thicknesses are selected according to the to-be-measured epitaxial wafers with different thicknesses, and compared with the related art in which all to-be-measured samples with different thicknesses are analyzed through the same reference spectrogram, the accuracy of the epitaxial wafer thickness measurement result is greatly improved. Particularly, the measurement result is more accurate for the epitaxial wafer with the thickness of 0.3-2 microns.

In the epitaxial wafer measuring method provided by the embodiment of the disclosure, the thickness of the related epitaxial wafer to be measured can be in the range of 0.3-200 microns, and the diameter of the related epitaxial wafer can reach 300 mm.

In some embodiments, the substrate silicon Wafer of the epitaxial Wafer to be tested is a Double polished Wafer (Double-sided polished Wafer) and a P + type silicon Wafer with a thickness of about 775um, and the epitaxial layer to be tested is a B-doped monocrystalline film deposited on the substrate silicon Wafer at a deposition temperature of about 1130 ℃. Of course, the above is merely an example, and the specific structure type of the epitaxial wafer is not limited.

In addition, in the method for measuring the thickness of the epitaxial wafer provided by the present disclosure, in step S02, the setting of the recipe parameters of the fourier-infrared-transform spectrum analyzer specifically includes:

the formula parameters comprise: a center peak exclusion window, a reference edge peak exclusion window, and an edge peak minimum height; wherein the central peak exclusion window is set to be greater than the width of the entire peak of the central peak of the reference spectrogram, the reference edge peak exclusion window is set to be greater than the width of the entire peak of the edge peak in the reference spectrogram, and the signal intensity of the minimum height of the edge peak is set to be greater than the signal intensity of the minimum height of the edge peak in the reference spectrogram.

In the above scheme, the result of the thickness measurement of the epitaxial wafer is mainly characterized by the edge peak (Sideburst) in the spectrogram, and therefore, uniqueness of the edge peak (Sideburst) in the spectrogram is required to be ensured, so when determining the characteristic band in the Reference spectrogram, that is, when setting a Center-burst Exclusion Window (Center-burst Exclusion Window) and a Reference edge peak Exclusion Window (Reference edge Exclusion Window), it is required to ensure that the Center peak Exclusion Window is larger than the width of the whole peak of the Center peak in the Reference spectrogram, the Reference edge peak Exclusion Window is larger than the width of the whole peak of the edge peak in the Reference spectrogram, and the signal intensity of the Minimum Height of the edge peak of the epitaxial wafer (EPI Minimum edge peak Height) is ensured to be larger than the signal intensity of the Minimum Height of the edge peak in the Reference spectrogram. If the measured data is not very stable, the data stability can be increased by adjusting the Number of scanning times (Number of Scans) of the Fourier transform infrared spectrum analyzer.

According to the scheme, the precision measurement of the thickness of the epitaxial wafer can be realized by precisely controlling the reference epitaxial wafer slicing quality and the spectrum peak window of the FTIR equipment, and the measured thickness range of the epitaxial wafer can reach 0.3-200 microns.

In addition, in the method for measuring the thickness of the epitaxial wafer provided by the embodiment of the disclosure, the scanning mode of the fourier infrared transform spectrum analyzer is as follows: and scanning at least 9 sampling points on the epitaxial wafer to be tested (namely, 9-point test pattern), wherein each sampling point is scanned at least 5 times (namely, 5 scan). It is understood that, in practical applications, the scanning mode of the fourier-infrared transform spectrum analyzer is not limited thereto.

In addition, in the method for measuring the thickness of the epitaxial wafer provided by the embodiment of the disclosure, the fourier infrared transform spectrum analyzer is used for measuring to obtain the reference spectrogram of the reference epitaxial wafer and the sample spectrogram of the epitaxial wafer to be measured, and the method specifically includes:

the Fourier infrared conversion spectrum analyzer pre-stores reference spectrogram data of the reference epitaxial wafer with different thicknesses, measures a sample spectrogram of the epitaxial wafer to be detected, and obtains the reference spectrogram according to the pre-stored reference spectrogram data and the sample spectrogram of the epitaxial wafer to be detected.

According to the scheme, the reference spectrogram data of the reference epitaxial wafer with different thicknesses can be stored in the memory of the Fourier infrared conversion spectrum analyzer in advance, so that the thickness range value of the epitaxial wafer to be measured can be set during measurement, and the reference spectrogram data of the reference epitaxial wafer with the corresponding thickness can be directly obtained.

In addition, in the epitaxial wafer thickness measuring method provided by the embodiment of the disclosure, before the thickness of the epitaxial wafer to be measured is measured, the spectrogram data of the reference epitaxial wafer pre-stored in the fourier-infrared transform spectrum analyzer is updated. The data update frequency can be determined according to practical application, for example, in a production line, before measurement, the operation is repeated for 1 time every day, and the measurement is performed on the reference slice to ensure that the data stored in the memory is the latest operation data result.

In addition, in the method for measuring the thickness of the epitaxial wafer provided by the present disclosure, for each reference epitaxial wafer, a calibration is performed, that is, before the step S03, the method further includes:

and 021, correcting (correcting) the Fourier infrared transform spectrum analyzer.

The step 021 specifically includes:

when the option of 'calibration test' of the Fourier transform infrared spectrum analyzer is not checked, a calibration reference epitaxial wafer provided by a factory is adopted, and the thickness value of the calibration reference epitaxial wafer is measured under the condition that the Fourier transform infrared spectrum analyzer is set to be the formula parameter;

correcting against a Standard Reference plate authentication value (QS Standard Reference verified Values) using a Linear equation f (x) ax + b, where a is a Linear value (Linear Term) and b is a Constant Term (Constant Term);

after the correction is completed, when the current Reference epitaxial wafer (Reference) is used for Measurement next time, a 'correction Measurement' option needs to be checked so as to measure the thickness of the epitaxial wafer to be measured.

In addition, the method for measuring the thickness of the epitaxial wafer further comprises the following steps,

and step S05, after the thickness measurement result of the epitaxial wafer is obtained, verifying the thickness measurement result of the epitaxial wafer to be measured.

The step S05 specifically includes:

selecting an epitaxial wafer sample wafer with a known thickness, a first reference epitaxial wafer and a second reference epitaxial wafer, wherein the thickness of the first reference epitaxial wafer and the thickness of the epitaxial wafer sample wafer meet the preset relationship, and the thickness of the second reference epitaxial wafer and the thickness of the epitaxial wafer sample wafer do not meet the preset relationship;

measuring to obtain a first reference spectrogram of the first reference epitaxial wafer and the epitaxial wafer sample wafer according to the set formula parameters by the Fourier infrared transform spectrum analyzer, and analyzing and calculating the first reference spectrogram to obtain a first thickness measurement result of the epitaxial wafer sample wafer;

measuring a second reference spectrogram of the second reference epitaxial wafer and the epitaxial wafer sample wafer according to the set formula parameters by the Fourier infrared transform spectrum analyzer, and analyzing and calculating the second reference spectrogram to obtain a second thickness measurement result of the epitaxial wafer sample wafer;

and comparing and analyzing the first thickness measurement result and the second thickness measurement result to verify the reliability of the thickness measurement result of the epitaxial wafer to be tested.

One specific verification process is illustrated below:

and according to the set formula parameters, taking 2 first reference epitaxial wafers and second reference epitaxial wafers with different thicknesses as examples, and respectively measuring the thickness of the same epitaxial wafer to be measured. The scanning mode of the Fourier infrared conversion spectrum analyzer is as follows: test 9 sample points (9Point), each sample Point scanned 5 times, each data scan 8 scans.

The thickness of the first reference epitaxial wafer is 0, and the thickness of the epitaxial wafer to be measured is 1.254 um; the thickness of the second reference epitaxial wafer is 20, and the thickness of the epitaxial wafer to be measured is 1.254 um.

Two groups of results obtained after the thickness of the epitaxial wafer to be measured is measured by adopting the first reference epitaxial wafer and the second reference epitaxial wafer are shown in the following table 1:

TABLE 1

Parameter(s)	First reference epitaxial wafer	Second reference epitaxial wafer
			Maximum thickness Measurement (MAX)	1.291	1.265
Measurement thickness Maximum (MIN)	1.268	1.255
			Mean value (AVERAGE)	1.274	1.260
Standard deviation (STDEV)	0.006	0.002
			Great difference (RANGE)	0.023	0.010
Repeatability (Repeatability)	0.48％	0.17％
			Reproducibility (Reroducibility)	1.81％	0.82％

From the above two sets of results, it can be seen that:

when the thickness of the reference epitaxial wafer is 0, the measurement result of the epitaxial wafer to be measured with the thickness of 1.254um is poor, the repeatability and the reproducibility are too high, and the measurement result exceeds the specification of the measurement requirement; when the thickness of the reference epitaxial wafer is 20, the measurement result of the epitaxial wafer to be measured with the thickness of 1.254um is obviously improved, the repeatability and the reproducibility are obviously reduced, the repeatability and the reproducibility result are both less than 1%, and the reliability and the stability are very good.

Therefore, the method for measuring the thickness of the epitaxial wafer provided by the embodiment of the disclosure can improve the accuracy of the measured thickness result of the epitaxial wafer by accurately controlling the thickness and the material of the reference epitaxial wafer and accurately regulating and controlling the spectrum peak window of the FTIR device, and the range of the thickness lateral quantity of the epitaxial wafer can reach 0.3-200um, and is suitable for measuring the thickness of large-size epitaxial wafers, such as epitaxial wafers with the diameter size of 300 mm.

The embodiment of the present disclosure further provides an epitaxial wafer thickness measurement system, including fourier infrared transform spectrum analyzer, fourier infrared transform spectrum analyzer includes:

the reference epitaxial wafer selection unit is used for selecting a reference epitaxial wafer according to the thickness range value of the epitaxial wafer to be tested, wherein the difference value of each parameter of the performance parameters of the reference epitaxial wafer and the epitaxial wafer to be tested is smaller than or equal to a threshold value, and the performance parameters comprise resistivity, doping concentration and surface property;

the formula parameter setting unit is used for setting formula parameters;

the measuring unit is used for measuring and obtaining a reference spectrogram of the reference epitaxial wafer and a sample spectrogram of the epitaxial wafer to be measured so as to obtain a comparison spectrogram;

and the processor is used for determining the characteristic wave band in the comparison spectrogram according to the formula parameters, and performing analysis calculation to obtain the thickness measurement result of the epitaxial wafer to be measured.

The epitaxial wafer thickness measurement system further comprises a memory for storing reference spectral data of a reference epitaxial wafer.

The following points need to be explained:

(1) the drawings of the embodiments of the disclosure only relate to the structures related to the embodiments of the disclosure, and other structures can refer to the common design.

(2) For purposes of clarity, the thickness of layers or regions in the figures used to describe embodiments of the present disclosure are exaggerated or reduced, i.e., the figures are not drawn on a true scale. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" or "under" another element, it can be "directly on" or "under" the other element or intervening elements may be present.

(3) Without conflict, embodiments of the present disclosure and features of the embodiments may be combined with each other to arrive at new embodiments.

The above is only a specific embodiment of the present disclosure, but the scope of the present disclosure is not limited thereto, and the scope of the present disclosure should be determined by the scope of the claims.