A method for predicting the metal content of a guide tube based on single crystal silicon polished wafers

Abstract

A method for predicting the metal content of a guide tube based on a single-crystal silicon polishing sheet relates to the field of metal content prediction. The method comprises the following steps: S1, using a guide tube to be tested to draw a single-crystal silicon rod to be tested, processing the single-crystal silicon rod to be tested into a polishing sheet to be tested, detecting the diameter of the polishing sheet to be tested, and thereby calculating the distance parameter between the polishing sheet to be tested and the guide tube; S2, detecting the metal content of the single-crystal silicon polishing sheet to be tested; and S3, predicting the metal content of the guide tube to be tested using a guide tube prediction model. The present invention utilizes the high sensitivity of single-crystal silicon polishing sheets to metal content to accurately infer the metal content of the guide tube based on the metal content of the single-crystal silicon polishing sheet, thereby achieving non-destructive testing of the guide tube and ensuring accurate and reliable test results.

Description

Technical Field

[0001] The invention relates to the field of metal content prediction, in particular to a method for predicting the metal content of a guide tube based on a single crystal silicon polishing sheet. Background Art

[0002] As a key raw material in the semiconductor industry, single-crystal silicon polished wafers are trending towards high-end, intelligent, and green manufacturing. With the rapid development of emerging technologies such as 5G and artificial intelligence, demand for high-performance, high-purity single-crystal silicon polished wafers is growing rapidly. Controlling impurities in silicon, particularly metallic impurities, is crucial. For example, in high-end applications such as high-performance integrated circuits and solar cells, strict control of metallic impurities is crucial for ensuring device performance.

[0003] As one of the most important metal impurities, iron content is crucial for metal control. The iron content in polished monocrystalline silicon wafers significantly impacts devices. Iron impurities reduce minority carrier lifetime, impacting MOS device efficiency and potentially reducing device reliability. In batteries, iron impurities reduce the open-circuit voltage, short-circuit current, and quantum efficiency of monocrystalline silicon cells, thereby impacting cell performance. Therefore, strict control of iron content is crucial during the production of polished monocrystalline silicon wafers.

[0004] During the production of silicon polished wafers, metallic iron is primarily introduced from the graphite components of the single crystal furnace. As a key component of the single crystal furnace's graphite heat field, the guide tube is particularly crucial to the crystal pulling process. The guide tube is closest to the crystal ingot. At high temperatures, the metallic iron impurities within it diffuse through thermal radiation, gradually and evenly penetrating the ingot, impacting its quality. Furthermore, the current feedstock requirements in the single crystal silicon pulling process continue to increase, leading to rising costs. If the metal content of the guide tube exceeds the specified limit, contamination of the crystal ingot will occur, resulting in significant cost losses.

[0005] Currently, the metal content in draft tubes is typically tested using GDMS (glow discharge mass spectrometry), a destructive method. Therefore, graphite manufacturers often use GDMS testing on furnace samples that undergo the purification process alongside the draft tube. However, because the purification effect is significantly affected by factors such as placement within the purification furnace and airflow guidance, metal testing results from these furnace samples cannot accurately reflect the metal content of the draft tube itself, hindering precise control and testing.

[0006] Furthermore, manufacturers of single-crystal silicon polishing sheets are also required to test the metal content of the graphite guide tubes they purchase to assess whether they meet production requirements and material specifications. Accurately testing the metal content of the guide tubes and providing feedback to the manufacturer can serve as a warning to those manufacturers whose metal content exceeds standards. Summary of the Invention

[0007] In order to solve the problem of inaccurate detection results of the metal content of the guide tube in the prior art, the present invention provides a method for predicting the metal content of the guide tube based on a single crystal silicon polishing wafer.

[0008] In order to achieve the above object, the specific solution adopted by the present invention is: a method for predicting the metal content of a guide tube based on a single crystal silicon polishing wafer, comprising the following steps:

[0009] S1, using the guide tube to be tested to draw the single crystal silicon rod to be tested, and calculating the distance between the single crystal silicon polished sheet to be tested and the guide tube to be tested during the drawing process;

[0010] S2, processing the single crystal silicon rod to be tested into a single crystal silicon polished wafer to be tested, and detecting the metal content of the single crystal silicon polished wafer to be tested;

[0011] S3, predicting the metal content of the guide tube to be tested by using the guide tube prediction model;

[0012] Among them, the metal content to be predicted is the iron content, and the guide tube prediction model is G=1.23+0.264*L-0.0983*H+0.0866*L*H, G is the metal content of the guide tube to be tested, L is the distance parameter between the single crystal silicon polishing wafer to be tested and the guide tube to be tested, and H is the metal content of the single crystal silicon polishing wafer to be tested.

[0013] As a further optimization of the above technical solution, the distance parameter between the single crystal silicon polishing wafer to be tested and the guide tube to be tested is L, L=D1-D2, D1 is the diameter of the small diameter end of the guide tube to be tested, and D2 is the diameter of the single crystal silicon polishing wafer to be tested.

[0014] As a further optimization of the above technical solution, the diameter difference between the single crystal silicon rod to be tested and the single crystal silicon polished wafer to be tested is no more than 5 mm.

[0015] As a further optimization of the above technical solution, the method for detecting the metal content of the single crystal silicon polished wafer to be tested is the SPV surface photovoltage method.

[0016] As a further optimization of the above technical solution, the method for detecting the metal content of the single crystal silicon polished wafer to be tested is:

[0017] S201, selecting a standard flow guide tube with a metal content to be predicted ≤ 0.5 ppmw to draw a standard single crystal silicon rod, wherein the diameter of the standard single crystal silicon rod and the single crystal silicon rod to be measured are the same;

[0018] S202, processing the standard single crystal silicon rod into a standard single crystal silicon polished wafer;

[0019] S203, using the SPV method to detect a standard single crystal silicon polished wafer to obtain a 49-point reference spectrum of metals in the standard single crystal silicon polished wafer, and using the SPV method to detect a single crystal silicon polished wafer to be tested to obtain a 49-point test spectrum of metals in the single crystal silicon polished wafer to be tested;

[0020] S204, based on the 49-point test map and the 49-point reference map, the metal content H of the single crystal silicon polished wafer to be tested is obtained, where H={(H s1 -H J1 )+(H s2 -H J2 )+(H s3 -H J3 )+.......(H s49 -H J49 )} / 49,H sx is the metal content of the xth point in the 49-point test spectrum, H Jx It is the metal content of the x-th point in the 49-point reference spectrum, where x is any natural number between 1 and 49.

[0021] As a further optimization of the above technical solution, the method for establishing the guide tube prediction model is as follows: first, n guide tubes with different metal contents and the same size specifications are selected, where n is a natural number and n≥3; second, n guide tubes are used to draw lightly boron-doped single crystal silicon rods of different diameters; third, the lightly boron-doped single crystal silicon rods are processed into polished wafers, and the metal content of the polished wafers is tested; finally, sample blocks are taken from the small-diameter end of the guide tube after drawing the lightly boron-doped single crystal silicon rods, and the metal content of the guide tube is detected by GDMS. Mathematical statistical tools are used to perform regression analysis to obtain the guide tube prediction model.

[0022] As a further optimization of the above technical solution, the raw materials of the lightly boron-doped single crystal silicon rod are polycrystalline silicon and boron master alloy.

[0023] As a further optimization of the above technical solution, the method for establishing the guide tube prediction model is as follows: first, three guide tubes with different metal contents and the same size specifications are selected, and three lightly doped single crystal silicon rods with different diameters are drawn using each guide tube. The lightly doped single crystal silicon rods are then processed into polished wafers, and the metal content of the polished wafers is tested using the SPV surface photovoltage method.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention utilizes the high sensitivity of single crystal silicon polishing wafers to metal content, accurately infers the metal content of the guide tube through the metal content of the single crystal silicon polishing wafer, realizes non-destructive testing of the guide tube, and ensures that the test results are accurate and reliable.

[0026] In the detection method described in the present invention, a standard single crystal silicon rod is drawn by selecting a standard guide tube with a predicted metal content ≤0.5ppmw, and a 49-point reference map of the metal to be measured is obtained. The metal content H of the single crystal silicon polished wafer to be measured is obtained by combining the 49-point test map and the 49-point reference map. This can eliminate the error in the detection result caused by the metal contained in the raw materials for drawing the single crystal silicon rod, thereby improving the detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the three-dimensional structure of the guide tube;

[0028] Figure 2 This is a schematic diagram of the positional relationship between the guide tube and the single crystal silicon rod during the single crystal silicon rod pulling process;

[0029] Figure 3 It is a 49-point benchmark map for SPV detection;

[0030] Description of the accompanying drawings: 1. Guide tube, 2. Single crystal silicon rod. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further elaborated in detail below in conjunction with specific embodiments. Parts not described and disclosed in detail in the following embodiments of the present invention should be understood as existing technologies known or should be known to those skilled in the art.

[0032] The present invention discloses a method for predicting the metal content of a guide tube based on a single crystal silicon polishing sheet, comprising the following steps:

[0033] S1: Using a flow guide to be tested, a single crystal silicon rod to be tested is drawn, and the single crystal silicon rod to be tested is processed into a single crystal silicon polished wafer to be tested. The distance parameter between the single crystal silicon polished wafer to be tested and the flow guide to be tested is calculated during the drawing process. Specifically, the single crystal silicon rod is processed into the single crystal silicon polished wafer to be tested through standard conventional processes such as cutting, tumbling, bonding, wire cutting, etching, grinding, and polishing.

[0034] The distance parameter between the single crystal silicon polishing wafer to be tested and the guide tube to be tested is L, L=D1-D2, D1 is the diameter of the small diameter end of the guide tube to be tested, and D2 is the diameter of the single crystal silicon polishing wafer to be tested.

[0035] When pulling the single crystal silicon rod to be tested, the existing rotary crystal pulling method is adopted, and the entire thermal field has a positioning setting. Before pulling the single crystal silicon rod to be tested, the seed crystal clamp above the guide tube is first aligned so that the single crystal silicon rod and the guide tube are coaxially distributed during the pulling process. Therefore, the pulled single crystal silicon rod to be tested is cylindrical, and the distance parameter L between the single crystal silicon polishing sheet to be tested and the guide tube to be tested is a fixed value in the same test.

[0036] S2, detecting the metal content of the single crystal silicon polished wafer to be tested.

[0037] The metal content of the single-crystal silicon polished wafer to be tested is determined using the SPV method. The metal to be tested is iron, and the SPV method for detecting metallic iron is an existing technology. Specifically, referring to the current industry standard "YS / T 679-2018: Surface Photovoltage Method for Determination of Minority Carrier Diffusion Length in Extrinsic Semiconductors," the diffusion length of the polished silicon wafer is measured using an SPV (surface photovoltage) instrument. The iron content in the polished silicon wafer can be accurately determined by measuring the attenuation change in the diffusion length before and after the iron-boron bond in the silicon is broken down using light pulses. The process of converting the diffusion length to the corresponding metal is not detailed here.

[0038] In order to avoid the influence of the metal elements to be measured in the basic components of the single crystal silicon rod when the single crystal silicon rod to be tested is pulled, thus affecting the prediction results of the metal content of the guide tube, when using the SPV method to detect the metal content of the single crystal silicon polished wafer to be tested, a standard single crystal silicon rod is first pulled to eliminate the influence of the metal elements to be measured in the basic components of the single crystal silicon rod, as follows:

[0039] S201, selecting a standard flow guide tube with a metal content to be predicted ≤ 0.5 ppmw to draw a standard single crystal silicon rod, wherein the diameter of the standard single crystal silicon rod and the single crystal silicon rod to be measured are the same, and the diameter of the polished wafer after processing is also the same;

[0040] S202, processing the standard single crystal silicon rod into a standard single crystal silicon polished wafer;

[0041] S203, using the SPV method to test a standard single crystal silicon polished wafer to obtain a 49-point reference spectrum of the metal to be tested, and using the SPV method to test the single crystal silicon polished wafer to obtain a 49-point test spectrum of the metal to be tested; it should be noted that both the 49-point reference spectrum and the 49-point test spectrum are spectrums obtained by testing 49 points on the single crystal silicon polished wafer using the SPV method;

[0042] S204, based on the 49-point test map and the 49-point reference map, the metal content H of the single crystal silicon polished wafer to be tested is obtained, where H={(H s1 -H J1 )+(H s2 -H J2 )+(H s3 -H J3 )+.......(H s49 -H J49 )} / 49,H sx is the metal content of the xth point in the 49-point test spectrum, H Jx It is the metal content of the x-th point in the 49-point reference spectrum, where x is any natural number between 1 and 49.

[0043] S3, predicting the metal content of the guide tube to be tested by using the guide tube prediction model.

[0044] The guide tube prediction model is G=1.23+0.264*L-0.0983*H+0.0866*L*H, where G is the metal content of the guide tube to be tested, L is the distance parameter between the single crystal silicon polishing wafer to be tested and the guide tube to be tested, and H is the metal content of the single crystal silicon polishing wafer to be tested.

[0045] It should be noted that: by selecting a standard guide tube with a metal content to be measured ≤0.5ppmw to draw a standard single crystal silicon rod, and obtaining a 49-point reference map of the metal to be measured, combining the 49-point test map and the 49-point reference map to obtain the metal content increment of the single crystal silicon polished wafer to be measured, and inputting the metal content increment as the metal content of the single crystal silicon polished wafer to be measured into the guide tube prediction model, the error caused by the metal contained in the raw materials for drawing the single crystal silicon rod can be eliminated, thereby improving the detection accuracy.

[0046] The process of establishing the guide tube prediction model is as follows: first, n guide tubes with different metal contents and the same size specifications are selected, where n is a natural number and n≥3; second, n guide tubes are used to draw lightly boron-doped single crystal silicon rods of different diameters; third, the lightly boron-doped single crystal silicon rods are processed into polished wafers, and the metal content of the polished wafers is tested using the SPV method; finally, sample blocks are taken from the small diameter end of the guide tube after drawing the lightly boron-doped single crystal silicon rods, and the metal content of the guide tubes is tested by GDMS. Mathematical statistical tools are used to perform regression analysis to obtain the guide tube prediction model.

[0047] Specifically, the process of establishing a draft tube prediction model for detecting the iron content in the draft tube includes the following steps:

[0048] First, three draft tubes 1 with different iron contents and the same size specifications were selected for cleaning and calcination. The inner diameter of the small diameter end of the draft tube 1 was 250 mm.

[0049] Secondly, three guide tubes were used to draw lightly boron-doped single-crystal silicon rods of different diameters; each guide tube was used to draw three lightly boron-doped single-crystal silicon rods, for a total of nine lightly boron-doped single-crystal silicon rods; the raw materials for the lightly boron-doped single-crystal silicon rods were polycrystalline silicon and boron master alloy. Because the iron content of lightly boron-doped single-crystal silicon rods can be accurately tested, they can accurately reflect the trace iron content in the silicon rods. In contrast, if heavily boron-doped single-crystal silicon rods are used, the test cannot be carried out because the impurity content is too high, resulting in inaccurate test results. In this case, the high concentration of iron and other impurities will interfere with the normal operation of the testing instrument, making the test data lose its reference value.

[0050] Next, the lightly doped single crystal silicon rods were processed into polished wafers, and the iron content of the polished wafers was tested using the SPV method. When testing the iron content of the polished wafers, 49 points were taken on the polished wafers.

[0051] During the process of pulling single crystal silicon rods, due to the heat radiation effect of the guide tube at high temperature, the iron content of the guide tube will be evenly radiated to the single crystal silicon rod through the rotating single crystal silicon rod.

[0052] Depend on Figure 1 、 2 It can be seen that the guide tube 1 is conical, with a large diameter end and a small diameter end. When in use, the large diameter end is upward and the small diameter end is downward. The distance parameter L between the guide tube 1 and the single crystal silicon polishing sheet is: the difference between the inner diameter of the small diameter end of the guide tube 1 and the diameter of the polishing sheet processed by the single crystal silicon rod 2.

[0053] Finally, samples were taken from the small diameter end of the guide tube after pulling the lightly boron-doped single crystal silicon rod, and the iron content was tested by GDMS. Mathematical statistical tools were used to perform regression analysis to obtain the guide tube prediction model.

[0054] Table 1 shows the SPV49 point full scan results obtained by pulling lightly boron-doped single crystal silicon rods of different diameters using guide tubes with different iron contents.

[0055] Table 1:

[0056] Test number Actual metal content measured outside the guide tube G / ppmw Diameter of lightly boron-doped single crystal silicon polishing wafer D / mm Distance parameter between lightly boron-doped single crystal silicon polishing sheet and guide tube *L / cm <![CDATA[SPV 49-point result H*E9 / (atoms / cm 3 ) <!-- 4 -->]]> 1 3.2 157 9.3 0.9 2 3.2 193 5.7 4 3 3.2 218 3.2 10 4 7.5 155 9.5 3.8 5 7.5 195 5.5 6.9 6 7.5 213 3.7 23 7 15.3 150 10 15 8 15.3 189 6.1 29.8 9 15.3 227 2.3 133.1

[0057] The data in Table 1 were analyzed by MINITAB to establish a regression equation to obtain the guide tube prediction model. Through mathematical statistics and regression equation, the R value (goodness of fit) was obtained to be 96%, and the P value was <0.001, indicating a significant correlation.

[0058] The prediction model of the guide tube is obtained: G=1.23+0.264*L-0.0983*H+0.0866*L*H

[0059] G is the actual metal content of the guide tube, L is the distance parameter between the single crystal silicon polishing wafer and the guide tube, and H is the SPV 49-point test result.

[0060] It should be noted that: 1) the method of measuring the metal content of a polished wafer using the SPV method at 49 points is referred to as SPV49 points. The specific locations of the 49 points are common knowledge in the art;

[0061] 2) According to actual experiments, it takes thousands of hours for the iron content of the guide tube to diffuse and decrease slightly, so the iron content loss in drawing a batch of lightly doped single crystal silicon rods can be ignored. After drawing the lightly boron-doped single crystal silicon rods, a sample block at the small diameter end of the guide tube is taken and the iron content is tested using GDMS to characterize the iron content of the guide tube; and the trace iron radiated by the heat of the guide tube acts on the lightly boron-doped single crystal silicon rods and can be significantly reflected on the lightly boron-doped single crystal silicon rods. Therefore, the present invention utilizes the high sensitivity of the single crystal silicon polishing sheet to the metal content, and accurately infers the metal content of the guide tube through the metal content of the polishing sheet, thereby realizing non-destructive testing of the guide tube and ensuring accurate and reliable test results.

[0062] During the production of single-crystal silicon, the metal content of the single-crystal silicon polishing sheet and the guide tube is of different orders of magnitude. Assuming a metal content of 1 ppmw in the guide tube, the corresponding metal concentration is approximately 2.5E16. When using this guide tube to pull a single-crystal silicon ingot, the guide tube radiates metal toward the single-crystal silicon ingot. At this time, the iron content in the polishing sheet is approximately 5E10, a difference of approximately one million times. By measuring the iron content of the single-crystal silicon polishing sheet and analyzing the iron content of the guide tube, non-destructive testing of the guide tube is possible, providing accurate test results.

[0063] Application Example 1

[0064] S1: Use the guide tube to be tested to draw the single crystal silicon rod to be tested, process the single crystal silicon rod to be tested into the single crystal silicon polished wafer to be tested, and calculate the distance parameter L between the single crystal silicon polished wafer to be tested and the guide tube to be tested.

[0065] The diameter of the single crystal silicon polished wafer to be tested drawn by the guide tube to be tested is D2=189mm, the diameter of the small diameter end of the guide tube to be tested is D1=250mm, and the distance parameter L between the single crystal silicon polished wafer to be tested and the guide tube to be tested is 6.1cm.

[0066] S2: Detect the metallic iron content of the single crystal silicon polished wafer to be tested.

[0067] A standard flow guide tube with a metallic iron content of ≤0.5ppmw is selected to draw a standard single crystal silicon rod, and the diameter of the standard single crystal silicon rod and the single crystal silicon rod to be tested are the same;

[0068] Processing standard single crystal silicon rods into standard single crystal silicon polished wafers;

[0069] The SPV method is used to detect the standard single crystal silicon polished wafer to obtain a 49-point reference spectrum of the metal iron to be tested. The SPV method is used to detect the single crystal silicon polished wafer to be tested to obtain a 49-point test spectrum of the metal iron to be tested. Figure 3 This is the 49-point reference map tested by the SPV method. The test points of the 49-point test map tested by the SPV method are the same as those of the reference map.

[0070] Table 2 below shows the specific location and map data of each test point at SPV49 (taking 6 o'clock as an example).

[0071] Table 2:

[0072] Serial number X Cooxd.(mm) Y Coord.(mm) <![CDATA[49-point basic map data H J > <![CDATA[49-point test spectrum data H s > <![CDATA[SPV 49-point increment H z > 1 0 0 5.59E+09 9.46E+09 3.87E+09 2 22.46 0 5.87E+09 2.76E+10 2.18E+10 3 15.88 15.88 8.07E+09 1.51E+10 7.08E+09 4 0 22.46 4.94E+09 5.97E+09 1.03E+09 5 -15.88 15.88 8.35E+09 2.17E+10 1.34E+10 6 -22.46 0 5.70E+09 2.59E+10 2.02E+10 7 -15.88 -15.88 3.87E+09 5.00E+09 1.14E+09 8 0 -22.46 8.00E+09 2.54E+10 1.74E+10 9 15.88 -15.88 6.64E+09 3.04E+10 2.37E+10 10 44.92 0 6.28E+09 2.35E+10 1.72E+10 11 41.5 17.19 2.70E+09 3.76E+09 1.06E+09 12 31.76 31.76 5.69E+09 7.98E+10 7.41E+10 13 17.19 41.5 7.80E+09 2.17E+10 1.39E+10 14 0 44.92 6.00E+09 4.07E+10 3.47E+10 15 -17.19 41.5 8.25E+09 1.27E+10 4.42E+09 16 -31.76 31.76 6.86E+09 2.10E+10 1.42E+10 17 -41.5 17.19 8.99E+09 1.19E+11 1.10E+11 18 -44.92 0 5.34E+09 2.62E+10 2.09E+10 19 -41.5 -17.19 8.66E+09 1.42E+11 1.33E+11 20 -31.76 -31.76 8.81E+09 8.26E+10 7.37E+10 21 -17.19 -41.5 7.14E+09 2.17E+10 1.46E+10 22 0 -44.92 7.07E+09 6.47E+10 5.77E+10 23 17.19 -41.5 6.87E+09 1.31E+10 6.21E+09 24 31.76 -31.76 1.71E+09 2.60E+09 8.83E+08 25 41.5 -17.19 7.37E+09 1.41E+11 1.34E+11 26 67.38 0 5.61E+09 3.42E+11 3.37E+11 27 65.08 17.44 8.32E+09 2.91E+11 2.82E+11 28 58.35 33.69 6.16E+09 2.97E+11 2.91E+11 29 47.64 47.64 6.91E+09 2.45E+11 2.38E+11 30 33.69 58.35 8.64E+09 1.74E+11 1.65E+11 31 17.44 65.08 8.83E+09 1.10E+11 1.02E+11 32 0 67.38 8.75E+09 2.19E+11 2.10E+11 33 -17.44 65.08 8.25E+09 1.11E+11 1.03E+11 34 -33.69 58.35 6.55E+09 2.15E+11 2.09E+11 35 -47.64 47.64 5.84E+09 9.40E+10 8.82E+10 36 -58.35 33.69 8.82E+09 3.25E+11 3.16E+11 37 -65.08 17.44 5.97E+09 2.85E+11 2.79E+11 38 -67.38 0 7.12E+09 3.89E+11 3.82E+11 39 -65.08 -17.44 6.86E+09 1.74E+11 1.67E+11 40 -58.35 -33.69 7.70E+09 2.16E+11 2.09E+11 41 -47.64 -47.64 7.27E+09 2.33E+11 2.26E+11 42 -33.69 -58.35 7.50E+09 1.83E+11 1.75E+11 43 -17.44 -65.08 8.54E+09 6.47E+10 5.62E+10 44 0 -67.38 5.23E+09 2.87E+11 2.82E+11 45 17.44 -65.08 7.76E+09 1.71E+11 1.63E+11 46 33.69 -58.35 6.05E+09 2.22E+11 2.16E+11 47 47.64 -47.64 8.93E+09 2.32E+11 2.23E+11 48 58.35 -33.69 6.96E+09 2.28E+11 2.21E+11 49 65.08 -17.44 7.97E+09 1.34E+11 1.26E+11 Summary / / / / 1.20E+11

[0073] The iron content of the polishing sheet is H, H={(H s1 -H J1 )+(H s2 -H J2 )+(H s3 -H J3)+.......(H s49 -H J49 )} / 49=(H z1 +H z2 +H z3 +……H z49 ) / 49.

[0074] S3: Predict the metallic iron content of the guide tube to be tested using the guide tube prediction model G=1.23+0.264*L-0.0983*H+0.0866*L*H.

[0075] Finally, a sample from the small diameter end of the guide tube to be tested was taken for GDMS testing to verify the accuracy of the metallic iron content predicted by the guide tube prediction model.

[0076] In this application example, the metal iron content of the guide tube to be tested obtained according to the guide tube prediction model, the metal iron content of the guide tube to be tested obtained by GDMS testing, and the intermediate test data are shown in Table 3 below:

[0077] Table 3:

[0078] project <![CDATA[SPV 49-point result * E9 / atoms / cm 3 > Diameter of the single crystal silicon rod to be tested after rolling / mm The distance parameter between the single crystal silicon polishing wafer to be tested and the guide tube to be tested is L / cm The metallic iron content in the guide tube to be tested obtained according to the guide tube prediction model / ppmw The metallic iron content in the guide tube to be tested obtained by GDMS / ppmw Deviation range / % Application Example 1 5.1 189 6.1 5.03 4.9 2.5%

[0079] As shown in Table 3, the metallic iron content predicted using the present invention's prediction method differs from that obtained using GDMS by less than 5%, remaining within a controllable range. This demonstrates that the metal content of the flow guide can be accurately estimated based on the metal content of the polishing pad, enabling nondestructive testing of the flow guide with accurate and reliable results.

[0080] It should be noted that the diameter of the single crystal silicon rod to be tested after tumbling in Table 3 is the diameter of the polished sheet prepared from the single crystal silicon rod to be tested. Since the diameter of the single crystal silicon rod is not completely consistent throughout, there may be tiny irregular shapes and slight defects on the surface. In order to avoid these problems, it is necessary to tumble and process it to produce a standard circular polished sheet. During the tumbling process, the removal amount is maintained at no more than 5 mm (that is, the diameter difference between the single crystal silicon rod to be tested and the single crystal silicon polished sheet to be tested is no more than 5 mm) to reduce the impact of the tumbling operation on the metal content of the single crystal silicon rod. In addition, in other processes of the present invention for processing single crystal silicon rods into single crystal silicon polished sheets, the diameter difference between the single crystal silicon rod and the corresponding polished sheet is maintained at no more than 5 mm.

[0081] Application Example 2

[0082] The overall method of Application Example 2 is the same as that of Application Example 1, with the main differences being the selected guide tube to be tested and the diameter of the single crystal silicon rod to be pulled to be tested being different from those in Application Example 1.

[0083] In this application example 2, the metal iron content of the guide tube to be tested obtained according to the guide tube prediction model, the metal iron content of the guide tube to be tested obtained by GDMS testing, and the intermediate test data are shown in Table 4 below:

[0084] Table 4:

[0085] project <![CDATA[SPV 49-point result * E9 / atoms / cm 3 > Diameter of the single crystal silicon rod to be tested after rolling / mm The distance parameter between the single crystal polished wafer to be tested and the guide tube to be tested is L / cm The metallic iron content in the guide tube to be tested obtained according to the guide tube prediction model / ppmw The metallic iron content in the guide tube to be tested obtained by GDMS / ppmw Deviation range / % Application Example 2 34 207 4.3 11.68 12.2 4.5%

[0086] As shown in Table 4, the metallic iron content predicted using the present invention's prediction method differs from that obtained using GDMS by less than 5%, remaining within a controllable range. This demonstrates that the metal content of the guide tube can be accurately estimated based on the metal content of the polishing pad, enabling nondestructive testing of the guide tube with accurate and reliable results.

[0087] Comparative Example 1

[0088] GDMS was used to test the iron content of the furnace sample of the guide tube in Application Example 1. The iron content of the furnace sample of the guide tube in Application Example 1 was 4.0 ppmw, which had a deviation range of (4.9-4.0) / 4.9*100%=18.36% from the metal iron content in the guide tube to be tested by GDMS, which was much larger than the iron content of the guide tube obtained by the prediction method of the present invention.

[0089] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for predicting the metal content of a guide tube based on a single crystal silicon polishing wafer, characterized in that: The following steps are involved: S1, using a guide tube to be tested to draw a single crystal silicon rod to be tested, processing the single crystal silicon rod to be tested into a single crystal silicon polished wafer to be tested, detecting the diameter of the single crystal silicon polished wafer to be tested and calculating the distance parameter between the single crystal silicon polished wafer to be tested and the guide tube to be tested; S2, detecting the metal content of the single crystal silicon polished wafer to be tested; S3, predicting the metal content of the guide tube to be tested by using the guide tube prediction model; Among them, the metal content to be predicted is the iron content, and the guide tube prediction model is G=1.23+0.264*L-0.0983*H+0.0866*L*H, G is the metal content of the guide tube to be tested, L is the distance parameter between the single crystal silicon polishing wafer to be tested and the guide tube to be tested, and H is the metal content of the single crystal silicon polishing wafer to be tested.

2. The method for predicting the metal content of a guide tube based on a single crystal silicon polishing wafer according to claim 1, characterized in that: The calculation method of the distance parameter between the single crystal silicon polishing wafer to be tested and the guide tube to be tested is: L= (D1-D2), D1 is the diameter of the small diameter end of the guide tube to be tested, and D2 is the diameter of the single crystal silicon polishing wafer to be tested.

3. The method for predicting the metal content of a guide tube based on a single crystal silicon polishing wafer according to claim 1, characterized in that: The diameter difference between the single crystal silicon rod to be tested and the single crystal silicon polished wafer to be tested is not greater than 5 mm.

4. The method for predicting the metal content of a guide tube based on a single crystal silicon polishing wafer according to claim 1, characterized in that: The method for detecting the metal content of the single crystal silicon polished sheet to be tested is the SPV surface photovoltage method.

5. The method for predicting the metal content of a guide tube based on a single crystal silicon polishing wafer according to claim 1, characterized in that: The metal content detection method of the single crystal silicon polished wafer to be tested is: S201, selecting a standard flow guide tube with a metal content to be predicted ≤ 0.5 ppmw to draw a standard single crystal silicon rod, wherein the diameter of the standard single crystal silicon rod and the single crystal silicon rod to be tested are the same; S202, processing the standard single crystal silicon rod into a standard single crystal silicon polished wafer; S203, using the SPV method to detect a standard single crystal silicon polished wafer to obtain a 49-point reference spectrum of metals in the standard single crystal silicon polished wafer, and using the SPV method to detect a single crystal silicon polished wafer to be tested to obtain a 49-point test spectrum of metals in the single crystal silicon polished wafer to be tested; S204, based on the 49-point test map and the 49-point reference map, the metal content H of the single crystal silicon polished wafer to be tested is obtained, where H={(H s1 -H J1 )+(H s2 -H J2 )+(H s3 -H J3 )+.......(H s49 -H J49 )} / 49,H sx is the metal content of the xth point in the 49-point test spectrum, H Jx It is the metal content of the x-th point in the 49-point reference spectrum, where x is any natural number between 1 and 49.

6. The method for predicting the metal content of a guide tube based on a single crystal silicon polishing wafer according to claim 5, characterized in that: The method for establishing the guide tube prediction model is as follows: first, n guide tubes with different metal contents and the same size are selected, where n is a natural number and n≥3; second, lightly boron-doped single crystal silicon rods of different diameters are drawn using the n guide tubes; third, the lightly boron-doped single crystal silicon rods are processed into polished wafers, and the metal content of the polished wafers is tested; finally, sampling blocks are taken from the small-diameter end of the guide tubes after drawing the lightly boron-doped single crystal silicon rods, and the metal content of the guide tubes is tested by GDMS. Mathematical statistical tools are used to perform regression analysis to obtain the guide tube prediction model.

7. The method for predicting the metal content of a guide tube based on a single crystal silicon polishing wafer according to claim 5, characterized in that: The raw materials of lightly boron-doped single crystal silicon rods are polycrystalline silicon and boron master alloy.

8. The method for predicting the metal content of a guide tube based on a single crystal silicon polishing wafer according to claim 5, characterized in that: The method for establishing the guide tube prediction model is as follows: first, three guide tubes with different metal contents and the same size are selected, and three lightly doped single crystal silicon rods with different diameters are drawn using each guide tube. The lightly doped single crystal silicon rods are then processed into polished wafers, and the metal content of the polished wafers is tested using the SPV surface photovoltage method.

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