WO2023051617A1

WO2023051617A1 - Measurement method and system for nitrogen element in nitrogen-doped monocrystalline silicon

Info

Publication number: WO2023051617A1
Application number: PCT/CN2022/122176
Authority: WO
Inventors: 徐鹏; 李阳
Original assignee: 西安奕斯伟材料科技有限公司
Priority date: 2021-09-28
Filing date: 2022-09-28
Publication date: 2023-04-06
Also published as: CN113884462A; TW202246753A

Abstract

A measurement method and system for a nitrogen element in nitrogen-doped monocrystalline silicon. The measurement method comprises: after eliminating a thermal donor existing in a monocrystalline silicon detection sample, rapidly cooling the detection sample so as to enable an infrared spectrum base line to be smooth, wherein a nitrogen element is doped in the monocrystalline silicon detection sample (S201); using a Fourier transform infrared (FTIR) spectrometer to detect the detection sample of which infrared spectrum base line is reduced, to obtain the absorption peak intensity of a position corresponding to the existing form of the nitrogen element (S202); and determining the content of the nitrogen element in the monocrystalline silicon detection sample according to the obtained absorption peak intensity (S203).

Description

Method and system for measuring nitrogen in nitrogen-doped single crystal silicon

Cross References to Related Applications

This application claims priority to Chinese Patent Application No. 202111144242.4 filed in China on September 28, 2021, the entire contents of which are hereby incorporated by reference.

technical field

The embodiments of the present application relate to the technical field of wafer manufacturing, and in particular to a method and system for measuring nitrogen in nitrogen-doped single crystal silicon.

Background technique

At present, in the process of large-sized semiconductor-grade single-crystal silicon wafers, single-crystal silicon rods drawn by the Czochralski method are usually used. The Czochralski method involves melting polysilicon in a crucible made of quartz to obtain a silicon melt, immersing a single crystal seed in the silicon melt, and continuously lifting the seed to move away from the surface of the silicon melt, whereby the phase interface grow single crystal silicon rods.

In the conventional scheme of pulling single crystal silicon rods, nitrogen doping technology is usually used to dope a small amount of nitrogen into the single crystal silicon crystal, so as to suppress the cavity-type crystal originating particles (Crystal Originated Particle, which seriously affects the quality of integrated circuits) COP) defects to improve the yield of integrated circuits; it can also promote oxygen precipitation and secondary induced defects in Czochralski single crystal silicon rods, and generate high-quality clean areas in the active areas on the surface of silicon wafers obtained by subsequent cutting. In order to facilitate the removal of metal impurities in the process of manufacturing integrated circuit devices; and it can also improve the mechanical strength of silicon wafers. Reduce the probability of warpage and breakage of silicon wafers during the fabrication of integrated circuits, so as to reduce the manufacturing cost of integrated circuits.

It can be seen from the above that the degree of effect achieved by nitrogen-doped single crystal silicon is usually determined by the concentration of nitrogen. However, in the current conventional solutions, the doping amount of nitrogen element is usually precisely controlled to control the concentration of nitrogen, which cannot be aimed at the completed pull. Nitrogen element measurement was performed on nitrogen-doped single crystal silicon.

Contents of the invention

In view of this, the embodiment of the present application expects to provide a method and system for measuring nitrogen in nitrogen-doped single crystal silicon, which can measure the content of nitrogen in the drawn nitrogen-doped single crystal silicon.

The technical scheme of the embodiment of the application is realized in this way:

In the first aspect, the embodiment of the present application provides a method for measuring nitrogen in nitrogen-doped single crystal silicon, the method comprising:

After eliminating the thermal donors present in the single crystal silicon detection sample, rapidly cooling the detection sample to make the infrared spectrum baseline gentle; wherein, the single crystal silicon detection sample is doped with nitrogen;

Use the Fourier Transform Infrared Spectrometer FTIR to detect the detection samples with reduced infrared spectrum baseline, and obtain the absorption peak intensity corresponding to the position of the nitrogen element;

Determine the nitrogen element content in the single crystal silicon detection sample according to the obtained absorption peak intensity.

In the second aspect, an embodiment of the present application provides a measurement system for nitrogen in nitrogen-doped single crystal silicon, the system includes: an elimination part, a baseline reduction part, a Fourier transform infrared absorption spectrometer FTIR and a determination part; wherein,

The elimination part is configured to eliminate thermal donors present in the single crystal silicon detection sample;

The baseline lowering portion is configured to lower the infrared spectrum baseline of the test sample after thermal donor elimination is completed;

The FTIR is configured to detect the detection sample that has reduced the baseline of the infrared spectrum, and obtain the intensity of the absorption peak corresponding to the position of the nitrogen element;

The determination part is configured to determine the content of nitrogen element in the single crystal silicon detection sample according to the obtained absorption peak intensity.

The embodiment of the present application provides a method and system for measuring nitrogen in nitrogen-doped single crystal silicon; by eliminating thermal donors and flattening the infrared spectrum baseline, the infrared absorption peaks corresponding to various forms of nitrogen are more accurate It is obviously detected, so that the nitrogen element in nitrogen-doped single crystal silicon can be accurately measured based on FTIR.

Description of drawings

Fig. 1 is a schematic diagram of a kind of infrared spectrum curve provided by the embodiment of the present application;

Fig. 2 is a schematic flow chart of a method for measuring nitrogen in nitrogen-doped single crystal silicon provided by the embodiment of the present application;

Figure 3 is a schematic diagram of another infrared spectrum curve provided by the embodiment of the present application;

Fig. 4 is a schematic composition diagram of a measurement system for nitrogen in nitrogen-doped single crystal silicon provided by the embodiment of the present application.

Detailed ways

The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

Spectral analysis is usually used to identify substances and determine their chemical composition, structure or relative content. At present, the most common spectral analysis technique is to detect chemical bonds in molecules by using Fourier Transform Infrared Spectroscopy (Fourier Transform InfRared spectroscopy, FTIR) to generate infrared absorption spectra of solids, liquids or gases. Samples (such as solids, liquids or gases), measure the transmitted or reflected light intensity for each wavelength, and then qualitatively or quantitatively analyze and determine the type and quantity of substances contained in the sample based on the spectral information. Since such spectral analysis technology can obtain test results without destroying the sample, it is widely used in the content testing of elements or components in the semiconductor industry, especially in the measurement of carbon and oxygen content.

For single crystal silicon rods obtained by Czochralski method using nitrogen doping technology, since the doped nitrogen does not exist in a single form, the positions of the infrared absorption peaks corresponding to various forms of existence are different. For example Generally speaking, nitrogen exists mostly in the form of NN pairs in single crystal silicon rods, but some nitrogen elements also exist in the form of nitrogen-oxygen complexes, such as NNO and NNO2 complexes. Take these three forms of existence as examples , the positions of the corresponding infrared absorption peaks are different, they are 963cm ^-1 , 996cm ^-1 and 1018cm ^-1 , respectively. Among them, the intensity of the infrared absorption peaks corresponding to NNO and NNO2 complexes is usually relatively weak and can be detected or measured The probability also decreases. In addition, the infrared absorption peaks based on impurities such as thermal donors also exist between 900cm ^-1 and 1000cm ^-1 , coupled with the influence of the infrared spectrum baseline, all the infrared spectrum measurements of various forms of nitrogen Accuracy is affected. Taking the infrared spectrum schematic diagram shown in Figure 1 as an example, the black thick line curve in the figure represents the actual infrared spectrum curve, and the black thin line in the figure is the corresponding NN pair obtained by analysis and fitting based on the actual infrared spectrum curve. , NNO and NNO2 complex infrared absorption peak curves, the black dotted line represents the impurity absorption peak curve schematic diagram, as can be seen from Figure 1, NN pairs, NNO and NNO2 complex infrared absorption peak curve baselines are obviously inconsistent, reducing the In addition, the impurity absorption peaks are obviously located near the infrared absorption peaks of NN pairs, NNO and NNO2 complexes, which will also affect the analysis and judgment of the infrared absorption peaks of NN pairs, NNO and NNO2 complexes.

Therefore, the current conventional scheme cannot accurately measure the nitrogen element in nitrogen-doped single crystal silicon based on FTIR.

In order to reduce the influence of the infrared absorption peak of impurities and the infrared spectrum baseline on the measurement of nitrogen element content, the embodiment of the present application expects to eliminate the thermal donor and smooth the infrared spectrum baseline to make the infrared absorption corresponding to the various forms of nitrogen element The peaks are detected more clearly, so that the accurate measurement of nitrogen in nitrogen-doped single crystal silicon can be carried out based on FTIR.

Based on the above description, see FIG. 2, which shows a method for measuring nitrogen in nitrogen-doped single crystal silicon provided by the embodiment of the present application. The method may include:

S201: After eliminating the thermal donors present in the single crystal silicon detection sample, rapidly cooling the detection sample so that the infrared spectrum baseline is flat; wherein, the single crystal silicon detection sample is doped with nitrogen;

S202: Using FTIR to detect the detection sample with a flattened infrared spectrum baseline, and obtain the intensity of the absorption peak at a position corresponding to the existence form of nitrogen;

S203: Determine the nitrogen element content in the single crystal silicon detection sample according to the obtained absorption peak intensity.

For the technical solution shown in Figure 1, in some possible implementations, in order to increase the probability of nitrogen being detected, the single crystal silicon detection sample can be selected as a thicker sample. In this embodiment, the sample's The thickness can be selected from 5mm to 10mm.

For the technical solution shown in FIG. 1 , in some possible implementations, the nitrogen element exists in the form of N-N pairs and nitrogen-oxygen complexes.

Regarding the above implementation manner, in some examples, the nitrogen-oxygen complex includes an NNO complex and an NNO2 complex.

For the above implementations and examples, in some examples, the absorption peak position corresponding to the NN pair is 963 cm ^-1 , the absorption peak position corresponding to the NNO complex is 996 cm ^-1 , and the NNO2 complex corresponds to The position of the absorption peak is 1018cm ^-1 .

For the technical solution shown in Figure 1, it should be noted that the thermal donor is usually formed by oxygen elements in the temperature range of 350°C to 500°C. Based on this, in the embodiment of the present application, in order to eliminate the thermal donor, The sample can be heated to exceed the above temperature range and maintained for a period of time to eliminate the thermal donor in the sample. After the elimination, the sample that has eliminated the thermal donor can be rapidly cooled to avoid the regeneration of the thermal donor. Usually, That is, the cooling rate of rapid cooling can be selected from 100°C/min to 200°C/min, and the optional coolant is liquid helium; After the heat donor, the test sample is rapidly cooled to make the infrared spectrum baseline gentle, including:

heating the test sample to 650°C, and continuing to heat for 30 minutes to 60 minutes, to remove the thermal donor in the test sample;

The test sample from which the hot donors have been removed is cooled by liquid helium to rapidly cool the test sample to flatten the infrared spectrum baseline.

For the above implementation, it should be noted that after the thermal donor is eliminated, the thermal donor impurity peaks in the range of 900 ^-1 to 1000 cm ^-1 in the infrared spectrum will be correspondingly removed, avoiding the impurity peaks in the spectrum from being sensitive to nitrogen. The influence of element-related absorption peaks makes it easier to determine the position of nitrogen-related absorption peaks. In addition, using liquid helium to cool the test sample after removing the thermal donor, in addition to avoiding the regeneration of the thermal donor, can also make the infrared spectrum baseline of the test sample relatively flat compared with normal temperature. Understandably, since the infrared absorption peak intensity of the nitrogen-oxygen complex, such as the NNO complex and the NNO2 complex, is relatively weak, a relatively gentle infrared spectrum baseline can make the infrared absorption peak intensity of the nitrogen-oxygen complex relative to the baseline There is a significant improvement, which in turn increases the probability that the infrared absorption peak of the nitrogen-oxygen complex is detected. Taking the infrared spectrum diagram shown in Figure 3 as an example, the black thick line curve in the figure represents the actual infrared spectrum curve, and the black thin line in the figure is the corresponding NN pair obtained by analysis and fitting based on the actual infrared spectrum curve. , NNO and NNO2 complex infrared absorption peak curves. It can be seen from Figure 3 that due to the removal of the thermal donor, the peak of the impurity thermal donor does not exist, and the rest of the infrared absorption is very weak at low temperature, the baseline is relatively flat, and there are form-related absorption peaks for nitrogen, such as The infrared absorption peaks of NN pairs, NNO and NNO2 complexes become narrower and easier to be detected and analyzed,

Through the above implementation, it should be noted that after eliminating the thermal donors in the sample and making the infrared spectrum baseline gentle, the sample can be detected by FTIR; in detail, based on the nitrogen The absorption peak positions corresponding to the various possible forms of existence of the element can be used to obtain the absorption peak intensity values at the corresponding positions. Quantitatively analyze the nitrogen content corresponding to various forms of nitrogen.

Based on the above description, in some possible implementations, the determination of the nitrogen element content in the single crystal silicon detection sample according to the obtained absorption peak intensity includes:

According to the conversion coefficient corresponding to the position of the absorption peak intensity and the corresponding absorption peak intensity value, the nitrogen content corresponding to various forms of nitrogen element existence is obtained;

The nitrogen content corresponding to all forms of the nitrogen element is summed to obtain the nitrogen element content in the single crystal silicon detection sample.

For the above implementation, it should be noted that according to the detection results of FTIR, the corresponding absorption peak intensity can be obtained from the absorption peak position corresponding to the form of nitrogen in the infrared spectrum. For various forms of nitrogen, such as NN pairs, NNO complexes and NNO2 complexes, in order to obtain the corresponding nitrogen content, it is necessary to convert the corresponding absorption peak intensities through mathematical processing. In this application In the embodiment, the conversion coefficient can be set correspondingly for various forms of nitrogen in advance, for example, the corresponding conversion coefficient of NN pair can be selected as 1.83×10 ¹⁷ cm ² , and the corresponding conversion coefficient of NNO complex can be selected as 3.04× The corresponding conversion coefficients of 10 ¹⁷ cm ² and NNO2 complexes can be selected as 0.84×10 ¹⁷ cm ² ; then, after obtaining the absorption peak intensities corresponding to the various forms of nitrogen, the corresponding conversion coefficients above can be used to convert the respective The corresponding absorption peak intensities are converted into their corresponding nitrogen contents; after obtaining the nitrogen contents corresponding to the various forms of nitrogen element, the overall nitrogen content in the sample can be calculated by summation.

Based on the same inventive concept as the aforementioned technical solution, see FIG. 4 , which shows a measurement system 40 of nitrogen in nitrogen-doped single crystal silicon provided by an embodiment of the present application. The system 40 includes: an elimination part 401, a gentle baseline part 402, Fourier transform infrared absorption spectrometer FTIR 403 and determination part 404; wherein,

The elimination part 401 is configured to eliminate thermal donors present in the single crystal silicon detection sample;

a flattened baseline portion 402 configured to lower the infrared spectrum baseline of the test sample after completion of thermal donor elimination;

FTIR 403, which is configured to detect the detection sample with reduced infrared spectrum baseline, and obtain the absorption peak intensity corresponding to the position of the nitrogen element;

The determination part 404 is configured to determine the content of nitrogen element in the single crystal silicon detection sample according to the obtained absorption peak intensity.

For the above technical solution, it should be noted that in the embodiment of the present application, the FTIR 403 at least includes an infrared light source, a beam splitter, an interferometer, a sample cell, a detector, a data processing system, a recording system, etc. In short, It is to use an interferometer such as a Michelson interferometer to obtain the interferogram of the incident light, and then perform a Fourier mathematical transformation through a data processing system to transform the time domain function interferogram into an infrared spectrogram. The determining part 404 may specifically be a computer system connected to the FTIR 403, capable of data processing. In the current common FTIR system, the above two components are usually presented as a whole product, which is not specifically limited or described in this embodiment of the present application.

For the above technical solutions, in some examples, the elimination part 401 can be specifically a heater capable of temperature control and having a holding cavity. After the detection sample is placed in the holding cavity, the eliminating part 401 is configured as heating the test sample to 650°C, and continuing to heat for 30 minutes to 60 minutes, to remove the thermal donor in the test sample;

The gentle baseline part 402 can specifically be a cooler capable of temperature detection, and the selected coolant in the cooler can be selected as liquid helium, or other coolants that will not react with the test sample can be selected. The gentle baseline part 402 is configured to cool the detection sample from which the thermal donors have been removed by liquid helium, so as to rapidly cool the detection sample to make the infrared spectrum baseline gentle.

For the above technical solution, in some examples, the determination part 404 is configured to obtain the nitrogen content corresponding to various forms of nitrogen element according to the conversion coefficient corresponding to the position of the absorption peak intensity and the corresponding absorption peak intensity value ;as well as,

It should be noted that: the technical solutions described in the embodiments of the present application may be combined arbitrarily if there is no conflict.

The above is only a specific implementation of the application, but the scope of protection of the application is not limited thereto. Anyone familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the application. Should be covered within the protection scope of this application. Therefore, the protection scope of the present application should be determined by the protection scope of the claims.

Claims

A method for measuring nitrogen in nitrogen-doped single crystal silicon, said method comprising:

After eliminating the thermal donors present in the single crystal silicon detection sample, rapidly cooling the detection sample to make the infrared spectrum baseline gentle; wherein, the single crystal silicon detection sample is doped with nitrogen;

Use the Fourier Transform Infrared Spectrometer FTIR to detect the detection samples with reduced infrared spectrum baseline, and obtain the absorption peak intensity corresponding to the position of the nitrogen element;

Determine the nitrogen element content in the single crystal silicon detection sample according to the obtained absorption peak intensity.
The method according to claim 1, wherein the thickness of the single crystal silicon detection sample is 5 mm to 10 mm.
The method according to claim 1, wherein, after eliminating the thermal donor present in the single crystal silicon detection sample, rapidly cooling the detection sample so that the infrared spectrum baseline is smooth, comprising:

heating the test sample to 650°C, and continuing to heat for 30 minutes to 60 minutes, to remove the thermal donor in the test sample;

The test sample from which the hot donors have been removed is cooled by liquid helium to rapidly cool the test sample to flatten the infrared spectral baseline.
The method according to claim 1, wherein the nitrogen element exists in the form of N-N pairs and nitrogen-oxygen complexes.
The method according to claim 4, wherein the nitroxide complex comprises NNO complex and NNO2 complex.
The method according to claim 5, wherein the absorption peak position corresponding to the NN pair is 963 cm -1 , the absorption peak position corresponding to the NNO complex is 996 cm -1 , and the absorption peak position corresponding to the NNO2 complex is The position of the absorption peak is 1018cm -1 .
The method according to claim 1, wherein said determining the nitrogen element content in the single crystal silicon detection sample according to the obtained absorption peak intensity comprises:

According to the conversion coefficient corresponding to the position of the absorption peak intensity and the corresponding absorption peak intensity value, the nitrogen content corresponding to various forms of nitrogen element existence is obtained;

The nitrogen content corresponding to all forms of the nitrogen element is summed to obtain the nitrogen element content in the single crystal silicon detection sample.
A system for measuring nitrogen in nitrogen-doped single crystal silicon, the system includes: an elimination part, a baseline reduction part, a Fourier transform infrared absorption spectrometer FTIR and a determination part; wherein,

The elimination part is configured to eliminate thermal donors present in the single crystal silicon detection sample;

The baseline lowering portion is configured to lower the infrared spectrum baseline of the test sample after thermal donor elimination is completed;

The FTIR is configured to detect the detection sample that has reduced the baseline of the infrared spectrum, and obtain the intensity of the absorption peak corresponding to the position of the nitrogen element;

The determination part is configured to determine the content of nitrogen element in the single crystal silicon detection sample according to the obtained absorption peak intensity.
The system according to claim 8, wherein the elimination part is configured to heat the detection sample to 650° C. for 30 minutes to 60 minutes, so as to remove the heat donor in the detection sample;

The baseline lowering part is configured to cool the detection sample from which the thermal donor has been removed by liquid helium, so as to quickly cool the detection sample to make the infrared spectrum baseline gentle.
The system according to claim 8, wherein the determination part is configured to obtain the nitrogen content corresponding to various forms of nitrogen element according to the conversion coefficient corresponding to the position of the absorption peak intensity and the corresponding absorption peak intensity value ;as well as,

The nitrogen content corresponding to all forms of the nitrogen element is summed to obtain the nitrogen element content in the single crystal silicon detection sample.