Measurement method of heavily doped P-type silicon wafer BMD, method and system for obtaining optimal thermal treatment conditions of silicon wafer growth BMD, and computer readable medium

Abstract

The invention provides a method for measuring the BMD of a heavily doped P-type silicon wafer, a method and a system for obtaining the optimal thermal treatment condition of the BMD of silicon wafer growth, and a computer readable medium, and belongs to the field of semiconductors. The method for measuring the BMD of the heavily-doped P-type silicon wafers comprises the following steps: providing a plurality of heavily-doped P-type silicon wafers, carrying out two-stage heat treatment on the silicon wafers under an aerobic condition, namely carrying out heat treatment at a first set temperature for a first set time, then heating to a second set temperature at a set temperature rise rate, and carrying out BMD measurement on the heavily-doped P-type silicon wafers under a second set temperature condition, so as to obtain the BMD of the heavily-doped P-type silicon wafers. And carrying out heating treatment for a second set time so as to grow BMD on the silicon wafer. And cleaning the silicon wafer on which the BMD grows. And measuring the silicon wafer to obtain the density and size of the BMD of the silicon wafer. According to the method, relatively accurate quantification is carried out on the maximum BMD density of the silicon wafer, so that the characteristics of the heavily doped P-type silicon wafer are evaluated, and the method has guiding significance for the subsequent processing technology.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method, system, computer-readable medium, and heavily doped P-type silicon wafer for obtaining optimal conditions for heat treatment of BMD growth in silicon wafers. Background Art

[0002] Bulk Micro-defect Density (BMD) is an important physical parameter of silicon wafers. The density of BMD in silicon wafers should not be too high or too low. A certain concentration of BMD can adsorb impurities on the surface of the silicon wafer into the body of the silicon wafer to form a surface clean area (Denuded zone), while too high a BMD density will cause the silicon wafer to warp during processing, such as during heat treatment. Too much BMD will cause leakage of the pn junction of components and reduce the minority carrier lifetime. In the process of silicon wafer production and device processing, a relatively accurate quantification of the maximum BMD density that can be formed on the silicon wafer is carried out to evaluate the characteristics of the heavily doped substrate, which has guiding significance for formulating the corresponding post-processing technology.

[0003] It should be noted that the information disclosed in the background technology section of the invention is only intended to deepen the understanding of the general background technology of the invention, and should not be regarded as an admission or suggestion in any form that the information constitutes prior art already known to those skilled in the art. Summary of the invention

[0004] The purpose of the present invention is to provide a method for measuring BMD of heavily doped P-type silicon wafers, a method, system and computer-readable medium for obtaining optimal conditions for heat treatment of BMD grown on silicon wafers, so as to solve the problem of how to measure the density and size of BMD grown on heavily doped P-type silicon wafers.

[0005] In order to solve the above technical problems, the present invention provides a method for measuring BMD of heavily doped P-type silicon wafers, comprising:

[0006] Providing a plurality of heavily doped P-type silicon wafers, subjecting the silicon wafers to a two-stage heat treatment under oxygen conditions, including heat treatment at a first set temperature for a first set time, and then heating to a second set temperature at a set heating rate, and heat treatment at the second set temperature for a second set time, so as to grow BMD on the silicon wafers;

[0007] Cleaning the silicon wafer on which the BMD is grown;

[0008] The silicon wafer is measured to obtain the density and size of the BMD of the silicon wafer.

[0009] Preferably, the oxygen content of the silicon wafer is in the range of 5-20 ppma, and the resistivity is in the range of 0.01-0.02 ohm.cm.

[0010] Preferably, the silicon wafer has defective particles, and the number of defective particles with a diameter of 37 nm on the surface of the silicon wafer ranges from 0 to 7000.

[0011] Preferably, the first set temperature range is 600-900° C., the first set time range is 30 min-300 min, the second set temperature range is 900-1200° C., and the second set time range is 10 h-20 h.

[0012] Preferably, the first set temperature range is 630-760° C., the first set time range is 100 min-200 min, the second set temperature range is 950-1100° C., and the second set time range is 14 h-18 h.

[0013] Preferably, the cleaned silicon wafer is split into two halves along the crystal direction of the silicon wafer, and a light scattering tomography volume micro-defect analyzer is used to measure the half silicon wafer to obtain the density and size of the BMD of the silicon wafer.

[0014] Preferably, during the two-stage heat treatment, the oxygen flow rate is 5-10 L / min.

[0015] Preferably, after the silicon wafer is subjected to two-stage heat treatment under oxygen conditions, an oxide film is formed on the surface of the silicon wafer, and the cleaning process of the silicon wafer on which the BMD is grown includes:

[0016] The silicon wafer is cleaned with a hydrofluoric acid solution having a concentration of 5 to 30% to remove the oxide film on the surface of the silicon wafer.

[0017] Based on the same inventive concept, the present invention also provides a method for obtaining optimal conditions for heat treatment of BMD growth in silicon wafers, comprising:

[0018] Selecting a plurality of heavily doped P-type silicon wafers, splitting the silicon wafers into two wafers, and defining the two wafers split from the same silicon wafer as a control group silicon wafer and an experimental group silicon wafer;

[0019] A plurality of control group silicon wafers are subjected to a two-stage heat treatment, including heat treatment at 780° C. for 3 hours under oxygen conditions, and then heated to 1000° C. at a set heating rate, and heat treated at 1000° C. for 16 hours, and the BMD density and BMD size of each control group silicon wafer are obtained;

[0020] The silicon wafers in the experimental group are measured by the measurement method described above to obtain the BMD density and BMD size of each silicon wafer in the experimental group;

[0021] The BMD density and BMD size of the control group silicon wafers and the experimental group silicon wafers that are split from the same silicon wafer are compared to obtain target data with the relative difference in BMD size remaining unchanged and the largest relative difference in BMD density. The heat treatment conditions of the experimental group silicon wafers corresponding to the target data are the optimal BMD heat treatment conditions.

[0022] Preferably, comparing the BMD density and BMD size of a control group of silicon wafers and an experimental group of silicon wafers split from a plurality of the same silicon wafers comprises:

[0023] Obtaining the coordinates of the silicon wafers of the control group and the experimental group through the detection system;

[0024] The BMD density and BMD size of the control group silicon wafer and the experimental group silicon wafer with the same coordinates were compared.

[0025] Based on the same inventive concept, the present invention also provides a system for obtaining optimal conditions for heat treatment of BMD growth in silicon wafers, comprising:

[0026] An acquisition module is used to acquire the BMD density and BMD size of each control group silicon wafer; acquire the BMD density and BMD size of each experimental group silicon wafer;

[0027] The comparison module is used to compare the BMD density and BMD size of a control group silicon wafer and an experimental group silicon wafer that are split from a plurality of the same silicon wafers, and obtain target data with the relative difference of BMD size remaining unchanged and the relative difference of BMD density being the largest. The heat treatment condition of the experimental group silicon wafer corresponding to the target data is the optimal BMD heat treatment condition.

[0028] Based on the same inventive concept, the present invention also provides a computer-readable medium on which a program is stored, including:

[0029] When the program is executed, at least part of the steps in the method for obtaining the optimal conditions for BMD heat treatment as described above are performed.

[0030] Compared with the prior art, the method for measuring BMD of heavily doped P-type silicon wafers of the present invention has the following advantages:

[0031] The present invention provides a plurality of heavily doped P-type silicon wafers, and performs two-stage heat treatment on the silicon wafers under oxygen conditions, including heat treatment at a first set temperature for a first set time, and then heating to a second set temperature at a set heating rate, and heat treatment at the second set temperature for a second set time, so as to grow BMD on the silicon wafer. The silicon wafer with BMD grown is cleaned. The silicon wafer is measured to obtain the density and size of the BMD of the silicon wafer. By measuring the density and size of the BMD grown on the heavily doped P-type silicon wafer, a relatively accurate quantification of the maximum BMD density formed on the heavily doped P-type silicon wafer can be performed, so as to evaluate the characteristics of the heavily doped P-type silicon wafer as a heavily doped substrate, which has guiding significance for subsequent processing technology.

[0032] The method, system, and computer-readable medium for obtaining optimal conditions for thermal treatment of BMD growth for silicon wafers provided in the present invention all belong to the same inventive concept as the method for obtaining optimal conditions for thermal treatment of BMD growth for silicon wafers provided in the present invention. Therefore, the system for obtaining optimal conditions for thermal treatment of BMD growth for silicon wafers, the computer-readable medium, and the heavily doped P-type silicon wafer provided in the present invention have at least all the advantages of the method for obtaining optimal conditions for thermal treatment of BMD growth for silicon wafers provided in the present invention, and can perform a relatively accurate quantification of the maximum BMD density formed to evaluate the characteristics of the heavily doped P-type silicon wafer, which has guiding significance for subsequent processing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a comparison of BMD density obtained after heat treatment of lightly doped P-type silicon wafers at 780°C and heat treatment under different temperature conditions;

[0034] Figure 2 is a flow chart of a method for measuring BMD of a heavily doped P-type silicon wafer in one embodiment of the present invention;

[0035] Figure 3 is a schematic diagram of a structure in which a silicon wafer is split into two pieces in one embodiment of the present invention;

[0036] Figure 4 is a flow chart of a method for obtaining optimal conditions for heat treatment of BMD growth on a silicon wafer in one embodiment of the present invention;

[0037] Figure 5 It is a schematic diagram of a temperature curve of a nucleation heat treatment of a heavily doped P-type silicon wafer, BMD at 780° C. in one embodiment of the present invention;

[0038] Figure 6 It is a schematic diagram of a temperature curve of a nucleation heat treatment of a heavily doped P-type silicon wafer and BMD at different temperatures in one embodiment of the present invention;

[0039] Figure 7It is a BMD density comparison diagram obtained after heat treatment of a heavily doped P-type silicon wafer at 780° C. and heat treatment under different temperature conditions in one embodiment of the present invention;

[0040] Figure 8 This is a comparison diagram of BMD sizes obtained after heat treatment of a heavily doped P-type silicon wafer at 780° C. and heat treatment under different temperature conditions in one embodiment of the present invention;

[0041] Fig. 9 Schematic diagram showing the change of the relative difference of BMD density between the control group silicon wafer and the experimental group silicon wafer with different temperatures in one embodiment of the present invention;

[0042] Fig.10 Schematic diagram showing the change of the relative difference of BMD size between the control group silicon wafer and the experimental group silicon wafer as the temperature changes in one embodiment of the present invention;

[0043] Fig.11 It is a schematic diagram comparing the BMD density and BMD size of three heavily doped P-type silicon wafers obtained at a nucleation temperature of 650° C.-730° C. in one embodiment of the present invention with the BMD density and BMD size obtained by the heat treatment described in the SEMI M90-0821 standard document;

[0044] In the figure,

[0045] 100-control group silicon wafer; 200-experimental group silicon wafer;

[0046] 300-Gap. DETAILED DESCRIPTION

[0047] In order to make the purpose, advantages and features of the present invention clearer, the method for obtaining the optimal conditions for heat treatment of BMD growth in silicon wafers proposed by the present invention is further described in detail below in combination with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not in precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. It should be understood that the drawings in the specification do not necessarily show the specific structure of the present invention in proportion, and the illustrative features used to illustrate certain principles of the present invention in the drawings in the specification will also be slightly simplified. The specific design features of the present invention disclosed herein include, for example, specific dimensions, directions, positions and shapes, which will be determined in part by the specific application and use environment. And, in the embodiments described below, sometimes the same figure mark is used in common between different drawings to represent the same part or a part with the same function, and its repeated description is omitted. In this specification, similar numbers and letters are used to represent similar items, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0048] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0049] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0050] Before measuring the BMD density of silicon wafers, an oxidation annealing process is required before they can be detected. The SEMIM90-0821 standard document introduces a BMD oxidation nucleation process with a heat treatment of 3 hours at 780°C to obtain a clean area of ​​the annealed wafer. This method is applicable to wafers with a resistance greater than 0.01Ω·cm. However, this method is limited to annealed wafers and is not applicable to epitaxial wafers. In addition, the BMD detection method uses mixed acid etching and then takes pictures with a microscope for observation. The test accuracy is much lower than that of the light scattering tomography micro defect analyzer (i.e., LSTD machine) detection method. The SEMI MF1239-0305 annotation document introduces a two-step heat treatment process of heat treatment at 750°C for 4 hours and at 1050°C for 16 hours. The amount of oxygen precipitation is characterized by the difference in interstitial oxygen content tested by spectroscopy. However, this method is applicable to P- or N-type wafers, not to P+ type wafers. In addition, this method does not directly measure BMD data. The industry refers to the above two SEMI standards for BMD heat treatment methods.

[0051] The patent with the publication number KR20040050780A discloses a method for forming BMD nuclei of silicon wafers. The method for improving BMD uniformity is to set the nucleation temperature of heat treatment to 600-750℃. However, it is still unknown whether the nucleation at this temperature affects the average density of BMD of silicon wafers, and whether the BMD density obtained at this nucleation temperature can represent the true value of BMD. According to our previous experimental data, the average BMD density of silicon wafers did not change when the lightly doped substrate was nucleated at 580-830℃. We do not know whether this phenomenon is applicable to heavily doped substrates. Since the heavily doped substrate has a higher doping amount than the lightly doped substrate, the body micro defect density is much higher than that of the lightly doped substrate. Whether the BMD level formed under different temperature conditions is consistent needs further study. Therefore, it is necessary to make a relatively accurate quantification of the maximum BMD density that can be formed on the silicon wafer to evaluate the characteristics of the heavily doped substrate, which has guiding significance for the back-end IC processing technology.

[0052] Ginseng Figure 1 As shown, our previous experimental data show that lightly doped P-type silicon wafers (i.e. Figure 1 The BMD nucleation temperature of the P-substrate in the SEMIM90-0821 standard document has a relatively small effect on the BMD density. Compared with the heat treatment described in the SEMIM90-0821 standard document, the BMD density value falls on the 1:1 line. At different temperatures, such as 630-830℃ nucleation temperature, the average BMD density in the P-substrate does not change. For heavily doped P-type silicon wafers (i.e., P+ substrates), it is unknown whether the BMD density will change at different BMD nucleation temperatures. Therefore, for heavily doped P-type silicon wafers, a relatively accurate quantification of the maximum BMD density can be formed to evaluate the characteristics of the heavily doped substrate, which has guiding significance for formulating corresponding post-processing processes.

[0053] The core idea of ​​the present invention is to provide a method for measuring the BMD of heavily doped P-type silicon wafers to obtain the density and size of the BMD grown on the heavily doped P-type silicon wafers, so as to make a relatively accurate quantification of the maximum BMD density formed on the heavily doped P-type silicon wafers, so as to evaluate the characteristics of the heavily doped P-type silicon wafers as heavily doped substrates, which has guiding significance for subsequent processing technology.

[0054] In order to realize the above idea, the present invention provides a method for measuring BMD of heavily doped P-type silicon wafer. Figure 2 and Figure 3 A specific implementation of a method for measuring BMD of a heavily doped P-type silicon wafer is disclosed. The method for measuring BMD of a heavily doped P-type silicon wafer includes the following steps S11 to S14.

[0055] Step S11: Provide a plurality of heavily doped P-type silicon wafers, and perform two-stage heat treatment on the silicon wafers under oxygen conditions, including heat treatment at a first set temperature for a first set time, and then heating to a second set temperature at a set heating rate, and heat treatment at the second set temperature for a second set time to form BMD on the silicon wafers.

[0056] Specifically, refer to Figure 2 As shown, the heavily doped P-type silicon wafer is a single crystal silicon wafer. The oxygen content of the silicon wafer ranges from 5 to 20 ppma (NewASTM ppma), and the resistivity is 0.01 to 0.02 ohm.cm. In this embodiment, the P-type silicon wafer is a silicon wafer doped with P-type impurities such as boron (B) and gallium (GA), and the resistivity is used to characterize the doping concentration of the silicon wafer, and the resistivity ranges from 0.01 to 0.02 ohm.cm. The silicon wafer has defective particles. Since the more defective particles, the more BMDs are formed, in this embodiment, the number of defective particles with a diameter of 37 nm on the surface of the silicon wafer ranges from 0 to 7000.

[0057] The silicon wafer is subjected to a two-stage heat treatment under oxygen conditions, including heat treatment at a first set temperature for a first set time, and then heated to a second set temperature at a set heating rate, and heat treated at the second set temperature for a second set time to form BMD on the silicon wafer, including:

[0058] First, under oxygen conditions, the silicon wafer is heat treated at a first set temperature for a first set time. Under an oxygen flow rate of 5-10L / min, the silicon wafer is placed in a furnace tube. The temperature of the furnace tube is adjusted to the first set temperature, and the heat treatment is continued for the first set time. The first set temperature range is 600-900°C. The first set time range is 30min-300min. That is, the first set temperature range can be 600°C, 630°C, 700°C, 760°C, 780°C, 770°C, 785°C, 800°C, 900°C, or any temperature value in the range of 600-900°C. The first set time can be 30min, 180min, 100min, 200min, 300min, or any time in the range of 30min-300min. In this embodiment, preferably, the first set temperature range is 630-760°C, and the first set time is 100min-200min.

[0059] Then, under oxygen conditions, the silicon wafer is heat-treated at a second set temperature for a second set time to form BMD on the silicon wafer. Oxygen is continuously introduced into the furnace tube, and the oxygen flow rate is 5-10L / min. The furnace tube is heated to the second set temperature at a rate of 10°C / min, and heat-treated for a second set time under this temperature condition to grow BMD. The second set temperature range is 900-1200°C. The second set time range is 10h-20h. That is, the second set temperature range can be 900°C, 9500°C, 1000°C, 1100°C, 1200°C, or any temperature value in the range of 900-1200°C. The second set time can be 10h, 14h, 18h, 20h, or any time in the range of 10h-20h. In this embodiment, preferably, the second set temperature range is 950-1100°C, and the second set time range is 14h-18h.

[0060] After the above two-stage heat treatment, BMD grows inside the silicon wafer.

[0061] Step S12: cleaning the silicon wafer on which the BMDs are grown.

[0062] Specifically, refer to Figure 2 As shown, after the silicon wafer undergoes two-stage heat treatment, an oxide film is formed on the surface of the silicon wafer. Since the oxide film affects the subsequent BMD measurement, it is necessary to remove the oxide film on the surface of the silicon wafer. The silicon wafer is cleaned with a hydrofluoric acid solution with a concentration of 10% to remove the oxide film on the surface of the silicon wafer. Of course, other cleaning solutions can also be used to remove the oxide layer on the surface of the silicon wafer. For example, a mixture of hydrochloric acid and hydrogen peroxide can be used to remove the oxide layer. As long as the oxide layer can be removed, no specific requirements are made for the selection of the cleaning solution. Preferably, the silicon wafer is cleaned with a hydrofluoric acid solution with a concentration of 10% to remove the oxide film on the surface of the silicon wafer to avoid affecting the BMD measurement results.

[0063] Step S13: splitting the cleaned silicon wafer into two halves along the crystal direction of the silicon wafer.

[0064] Specifically, refer to Figure 2 and Figure 3 As shown, the cleaned silicon wafer is split into two halves along the crystal direction of the silicon wafer. After selecting the required single crystal silicon wafer, each silicon wafer is split into two pieces along its crystal direction. During the process of straightening the silicon wafer, one side of the silicon wafer has a notch 300 that represents the crystal direction of the silicon wafer. <100> For example, the crystal direction of the silicon wafer is the direction of 45° away from the notch 300. For splitting the silicon wafer of other crystal directions into two pieces along the crystal direction, those skilled in the art are already familiar with the specific operation, which will not be described in detail here.

[0065] Step S14: measuring half of the silicon wafer to obtain the density and size of the BMD of the silicon wafer.

[0066] Specifically, refer to Figure 2 and Figure 3 As shown, a half-wafer is loaded into the LSTD machine for testing. During the test, there are multiple test points at the radial position of the half-wafer close to the split plane. Two adjacent test points can be equal or unequal. Preferably, the radial position is selected as follows Figure 3 For example, 19 test points can be selected to measure the half-wafer to obtain the BMD density and BMD size of each half-wafer. Each test point has a corresponding coordinate in the silicon wafer. The BMD density is the number of BMDs generated per cubic centimeter, in units of ea / cm 3 BMD is a spherical structure. BMD size is the diameter of BMD.

[0067] The density and size of the BMDs grown on heavily doped P-type silicon wafers are measured by the above-mentioned measurement method, so that a relatively accurate quantification of the maximum BMD density formed on the heavily doped P-type silicon wafers can be made, so as to evaluate the characteristics of the heavily doped P-type silicon wafers as heavily doped substrates, which has guiding significance for subsequent processing technology.

[0068] In order to realize the above idea, the present invention provides a method for obtaining the optimal heat treatment conditions for BMD growth in silicon wafers. Figures 3 to 11 A specific implementation of a method for obtaining optimal conditions for heat treatment of BMD growth on a silicon wafer is disclosed. The method for obtaining optimal conditions for heat treatment of BMD growth on a silicon wafer includes the following steps S21 to S26.

[0069] Step S21: selecting a plurality of heavily doped P-type silicon wafers, splitting the silicon wafers into two pieces, and defining the two pieces split from the same silicon wafer as a control group silicon wafer 100 and an experimental group silicon wafer 200.

[0070] Specifically, refer to Figure 3 and Figure 4 As shown, a plurality of heavily doped P-type silicon wafers (hereinafter referred to as "silicon wafers") are selected. The silicon wafer is a P-type substrate doped with elements such as boron and aluminum. And the P-type substrate is heavily doped. The oxygen content of the silicon wafer ranges from 5ppma to 20ppma. The resistivity is 0.01ohm.cm-0.02ohm.cm. The resistivity is used to characterize the amount of doping in the silicon wafer substrate. The silicon wafer has defective particles, and the number of defective particles with a diameter of 37nm on the surface of the silicon wafer ranges from 0 to 7000.

[0071] After selecting the required silicon wafers, each silicon wafer is split into two pieces along its crystal direction. During the process of straightening the silicon wafer, one side of the silicon wafer has a notch 300 that represents the crystal direction of the silicon wafer. <100> Taking a silicon wafer with a crystal orientation as an example, the crystal orientation direction is the direction of 45° away from the notch 300, which is the crystal orientation direction of the silicon wafer. For silicon wafers with other crystal orientations that are split into two pieces along their crystal orientation direction, those skilled in the art are already familiar with the specific operation and will not be described in detail here. The two silicon wafers split from the same silicon wafer are defined as a control group silicon wafer 100 and an experimental group silicon wafer 200, respectively.

[0072] Step S22: subjecting multiple control group silicon wafers to a two-stage heat treatment, including heat treatment at 780°C for 3 hours under oxygen conditions, and then heating to 1000°C at a set heating rate, and heating treatment at 1000°C for 16 hours.

[0073] Specifically, refer to Figure 5 As shown. Before transporting a plurality of control group silicon wafers 100 to the furnace tube, oxygen needs to be introduced into the furnace tube at a rate of 5-10L / min. Next, transport a plurality of control group silicon wafers 100 to the furnace tube and perform heat treatment according to the heat treatment method described in the SEMIM90-0821 standard document. The heat treatment process includes two stages. The first stage is to heat the furnace tube to 780°C and heat treat it for 3 hours under this temperature condition so that BMD begins to nucleate. The second stage is to heat the furnace tube to 1000°C at a rate of 10°C / min and heat treat it for 16 hours under this temperature condition so that BMD grows. Of course, the furnace tube can also be heated to 1000°C at a rate of 20°C / min, or 30°C / min, etc., and no specific limitation is made here. In this embodiment, preferably, the furnace tube is heated at a rate of 10°C / min.

[0074] Step S23 : cleaning the plurality of control group silicon wafers 100 after the two-stage heat treatment, and measuring them after cleaning to obtain the BMD density and BMD size of each control group silicon wafer 100 .

[0075] Specifically, refer to Figures 3 to 5As shown. After the two-stage heat treatment, the oxide layer on the surface of multiple control group silicon wafers 100 is cleaned. For example, a hydrofluoric acid solution with a concentration of 5 to 30% can be used to clean the silicon wafer to remove the oxide film on the surface of the silicon wafer. Of course, other cleaning solutions can also be used to remove the oxide layer on the surface of the silicon wafer. For example, a mixture of hydrochloric acid and hydrogen peroxide can be used to remove the oxide layer. As long as the oxide layer can be removed, there is no specific requirement for the selection of cleaning solution. Preferably, a hydrofluoric acid solution with a concentration of 10% is used to clean the silicon wafer to remove the oxide film on the surface of the silicon wafer. Then, the control group silicon wafer 100 is loaded into the LSTD machine for detection. During the detection, there are multiple test points at the radial position of the half-wafer control group silicon wafer 100 close to the split plane. Two adjacent test points may be equal or unequal. Preferably, at this radial position, select Figure 3 For example, 19 test points can be selected to measure the half-wafer control group silicon wafer 100 to obtain the BMD density and BMD size of each half-wafer control group silicon wafer 100. Each test point has a corresponding coordinate in the silicon wafer. The BMD density is the number of BMDs generated per cubic centimeter, and the unit is ea / cm 3 BMD is a spherical structure. BMD size is the diameter of BMD. The BMD density and BMD size of each control group silicon wafer 100 are recorded as BMD 密度对照组 and BMD 大小对照组 .

[0076] Step S24: Divide the plurality of experimental silicon wafers 200 into n groups, and subject each group of experimental silicon wafers 200 to a two-stage heat treatment, including heating each group at a set temperature of t under oxygen conditions. n The first set time is heat-treated under the conditions, and then heated to the second set temperature at a set heating rate, and the second set time is heat-treated under the second set temperature conditions, wherein n is an integer greater than 1, and each group of t n The temperature conditions are different, and t n The value range is 630℃≤t n ≤830℃.

[0077] Specifically, refer to Figures 3 to 6 As shown. Multiple experimental group silicon wafers 200 are divided into multiple groups, and each group of experimental group silicon wafers 200 are subjected to two-stage heat treatment. Before the multiple experimental group silicon wafers 200 are transported to the furnace tube, oxygen needs to be introduced into the furnace tube at a rate of 5-10L / min. Then, the multiple experimental group silicon wafers 200 are transported to the furnace tube for heat treatment. The heat treatment includes two stages. The first stage is to heat the furnace tube of the first group of multiple experimental group silicon wafers 200 to t 1 , and at t1 The heat treatment is carried out for 3 hours at a temperature condition to allow BMD to begin nucleation. The second stage is to heat the furnace tube to 1000°C at a rate of 10°C / min and heat treat for 16 hours at this temperature condition to allow BMD to grow. 1 ≤830℃.

[0078] Next, the temperature of the second group of experimental silicon wafers was raised to t 2 , and at t 2 The temperature was set to 30 °C for 3 hours to allow BMD to begin nucleation. Then, the furnace was heated to 1000 °C at a rate of 10 °C / min and heat treated at this temperature for 16 hours to allow BMD to grow. 1 ≠t 2 , and 630℃≤t 2 ≤830℃.

[0079] As above, during the first stage heat treatment of the nth (where n is an integer greater than 1) group of multiple experimental group silicon wafers 200, the furnace tube of the nth group of multiple experimental group silicon wafers 200 is heated to t n , and at t n The temperature was set to 630°C for 3 hours to allow BMD to nucleate. Then, the furnace was heated to 1000°C at a rate of 10°C / min and heat treated for 16 hours at this temperature to allow BMD to grow. n ≤830℃.

[0080] As a preference of this embodiment, the plurality of experimental groups of silicon wafers 200 are divided into 6 groups. The set temperature t 1 =830℃. The set temperature of the second group is t 2 =790℃. The set temperature of the third group is t 3 =760℃. The set temperature of the fourth group is t 4 =730℃. The set temperature of the fifth group is t 5 = 680°C. The set temperature of the sixth group is t 6 =630°C. The following will explain the multiple experimental silicon wafers 200 into 6 experimental silicon wafers 200. Figure 6 As shown, in Figure 6 The temperatures at c in the figure are curves formed by heat treatment for 3 hours at 830°C, 790°C, 760°C, 730°C, 680°C, and 630°C, respectively. At this curve, BMD begins to nucleate.

[0081] Step S25: cleaning the plurality of experimental silicon wafers 200 after the two-stage heat treatment, and measuring them after cleaning to obtain the BMD density and BMD size of each experimental silicon wafer 200.

[0082] Specifically, refer to Figures 3 to 8 After the oxide layer on the surface of the experimental group silicon wafer 200 is removed by cleaning, each group of experimental group silicon wafers 200 is subjected to BMD measurement at the test points with the same coordinates as those in step S2 using a light scattering tomography volume micro defect analyzer. The half-chip experimental group silicon wafer 200 also has coordinates corresponding to the half-chip control group silicon wafer 100 as shown in FIG. Figure 3 The test points in area b. In order to keep consistent with the coordinates of the test points of the control group silicon wafer 100, 19 test points are selected for the test points of the experimental group silicon wafer 200, and each test point corresponds to the test point of the control group silicon wafer 100. The coordinate points corresponding to the 19 test points of the experimental group silicon wafer 200 are the same as the coordinates of the control group silicon wafer 100. The BMD density and BMD size of the test points at the same coordinate points of the control group silicon wafer 100 and the experimental group silicon wafer 200 are obtained, and are recorded as BMD 密度实验组 and BMD 大小实验组 .

[0083] from Figure 7 It can be seen that the nucleation temperature has a significant effect on the heavily doped P-type silicon wafer (i.e. Figure 7 The P+ substrate BMD density in the heat treatment process is greatly affected. Compared with the heat treatment process described in the SEMI M90-0821 standard document, the P+ substrate BMD density increases significantly at 630-760℃, and the maximum value of the P+ substrate BMD nucleation density is obtained at 680℃. In the temperature range of 780-830℃, as the temperature increases, the P+ substrate BMD density decreases. However, from Figure 8 It can be seen that in the temperature range of 630℃-830℃, the BMD size of the P+ substrate does not show obvious changes.

[0084] Step S26: Compare the BMD density and BMD size of the control group silicon wafer 100 and the experimental group silicon wafer 200 which are split from the same silicon wafer, and obtain target data in which the relative difference of BMD size remains unchanged and the relative difference of BMD density is the largest. The heat treatment condition of the experimental group silicon wafer 200 corresponding to the target data is the optimal BMD heat treatment condition.

[0085] Specifically, refer to Figure 3 , Figure 4 ,as well as Figures 9 to 11As shown, the coordinates of the control group silicon wafer 100 and the coordinates of the experimental group silicon wafer 200 are obtained through the detection system. The BMD density and BMD size of the control group silicon wafer 100 and the experimental group silicon wafer 200 with the same coordinates are compared. The BMD density and BMD size data of the control group silicon wafer 100 and the experimental group silicon wafer 200 split from the same silicon wafer are compared. The target data in which the relative difference in BMD size remains unchanged and the relative difference in BMD density is the largest is obtained. Then, the heat treatment condition of the experimental group silicon wafer 200 corresponding to the target data is the optimal BMD heat treatment condition. Among them, the relative difference in BMD density (%) = (BMD 密度实验组 -BMD 密度对照组 ) / BMD 密度对照组 * 100. Relative difference in BMD size (%) = (BMD 大小实验组 -BMD 大小对照组 ) / BMD 大小对照组 *100.

[0086] from Fig. 9 It can be seen that when the nucleation temperature is in the range of 630-760℃, the relative difference of BMD density of P+ substrate increases significantly. In the temperature range of 760-830℃, as the temperature increases, the relative difference of BMD density of P+ substrate decreases. Fig.10 It can be seen that within the temperature range of 630°C-830°C, the relative difference in the BMD size of the P+ substrate does not show obvious changes.

[0087] Continue to participate Fig.11 As shown, Fig.11 It can be seen that for wafer 1 (i.e., Fig.11 Wafer1 in the figure), Wafer2 (i.e., Fig.11 Wafer2) and Wafer3 (i.e., Fig.11 As can be seen from Wafer3 in the figure (11a), the BMD density and BMD size of three heavily doped P-type silicon wafers obtained by the heat treatment described in the SEMI M90-0821 standard document are shown in Figure 11b. The BMD density and BMD size of three heavily doped P-type silicon wafers obtained at a nucleation temperature of 650℃-730℃ are compared with the BMD density and BMD size obtained by the heat treatment described in the SEMI M90-0821 standard document. The BMD density increases significantly, while the BMD size does not change significantly.

[0088] From the above description, it can be seen that, preferably, the optimal nucleation temperature on a P+ substrate is 630° C.-760° C. More preferably, the optimal nucleation temperature on a P+ substrate is 650-730° C.

[0089] The method for obtaining the optimal heat treatment conditions for BMD growth on a silicon wafer disclosed in this embodiment can not only find that for heavily doped P-type silicon wafers, the BMD density will change at different BMD nucleation temperatures, but also form a relatively accurate quantification of the maximum BMD density, obtain the optimal heat treatment conditions for the BMD density, evaluate the characteristics of the heavily doped substrate, and have guiding significance for formulating the corresponding post-processing technology.

[0090] To realize the above idea, this embodiment also discloses a system for obtaining optimal conditions for heat treatment of BMD growth in silicon wafers, including:

[0091] An acquisition module, used to acquire the BMD density and BMD size of each control group silicon wafer 100; acquire the BMD density and BMD size of each experimental group silicon wafer 200;

[0092] The comparison module is used to compare the BMD density and BMD size of a control group silicon wafer 100 and an experimental group silicon wafer 200 that are split from a plurality of the same silicon wafers, and obtain target data in which the relative difference in BMD size remains unchanged and the relative difference in BMD density is the largest. The heat treatment condition of the experimental group silicon wafer 200 corresponding to the target data is the optimal BMD heat treatment condition.

[0093] To realize the above idea, the embodiment further discloses a computer-readable medium on which a program is stored, including:

[0094] When the program is executed, at least part of the steps in the method for obtaining the optimal conditions for BMD heat treatment as described above are performed.

[0095] To realize the above idea, this embodiment also discloses a heavily doped P-type silicon wafer, comprising:

[0096] The silicon wafer is heat-treated using the heat treatment conditions obtained by the method for obtaining the optimal BMD heat treatment conditions as described above, so as to grow BMD on the silicon wafer.

[0097] The system for obtaining optimal conditions for thermal treatment of BMD growth of silicon wafers, the computer-readable medium, and the heavily doped P-type silicon wafer provided in this embodiment all belong to the same inventive concept as the method for obtaining optimal conditions for thermal treatment of BMD growth of silicon wafers provided in this embodiment. Therefore, the system for obtaining optimal conditions for thermal treatment of BMD growth of silicon wafers, the computer-readable medium, and the heavily doped P-type silicon wafer provided in this embodiment at least have all the advantages of the method for obtaining optimal conditions for thermal treatment of BMD growth of silicon wafers provided in this embodiment, and can make a relatively accurate quantification of the maximum BMD density formed to evaluate the characteristics of the heavily doped P-type silicon wafer, which has guiding significance for subsequent processing technology.

[0098] In summary, the above embodiments provide detailed descriptions of different configurations of the method for obtaining the optimal conditions for heat treatment of BMD growth in silicon wafers. Of course, the above description is only a description of the preferred embodiments of the present invention, and is not any limitation to the scope of the present invention. The present invention includes but is not limited to the configurations listed in the above embodiments. Those skilled in the art can draw inferences based on the contents of the above embodiments. Any changes and modifications made by those of ordinary skill in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A method for measuring BMD of heavily doped P-type silicon wafer, characterized in that: include: Providing a plurality of heavily doped P-type silicon wafers, subjecting the silicon wafers to a two-stage heat treatment under oxygen conditions, including heat treatment at a first set temperature for a first set time, and then heating to a second set temperature at a set heating rate, and heat treatment at the second set temperature for a second set time, so as to grow BMD on the silicon wafers; Cleaning the silicon wafer on which the BMD is grown; The silicon wafer is measured to obtain the density and size of the BMD of the silicon wafer.

2. The method for measuring BMD of heavily doped P-type silicon wafer according to claim 1, characterized in that: The oxygen content of the silicon wafer is in the range of 5-20 ppma, and the resistivity is 0.01-0.02 ohm.cm.

3. The method for measuring BMD of heavily doped P-type silicon wafer according to claim 1, characterized in that: The silicon wafer has defective particles, and the number of defective particles with a diameter of 37 nm on the surface of the silicon wafer ranges from 0 to 7000.

4. The method for measuring BMD of heavily doped P-type silicon wafer according to claim 1, characterized in that: The first set temperature range is 600-900° C., the first set time range is 30 min-300 min, the second set temperature range is 900-1200° C., and the second set time range is 10 h-20 h.

5. The method for measuring BMD of heavily doped P-type silicon wafer according to claim 4, characterized in that: The first set temperature range is 630-760° C., the first set time range is 100 min-200 min, the second set temperature range is 950-1100° C., and the second set time range is 14 h-18 h.

6. The method for measuring BMD of heavily doped P-type silicon wafer according to claim 1, characterized in that: The cleaned silicon wafer is split into two halves along the crystal direction of the silicon wafer, and a light scattering tomography volume micro defect analyzer is used to measure the half silicon wafer to obtain the density and size of the BMD of the silicon wafer.

7. The method for measuring BMD of heavily doped P-type silicon wafer according to claim 1, characterized in that: During the two-stage heat treatment, the oxygen flow rate is 5-10L / min.

8. The method for measuring BMD of heavily doped P-type silicon wafer according to claim 1, characterized in that: After the silicon wafer is subjected to two-stage heat treatment under oxygen conditions, an oxide film is formed on the surface of the silicon wafer. The cleaning process of the silicon wafer on which the BMD is grown includes: The silicon wafer is cleaned with a hydrofluoric acid solution having a concentration of 5 to 30% to remove the oxide film on the surface of the silicon wafer.

9. A method for obtaining optimal heat treatment conditions for BMD growth on silicon wafers, characterized in that: include: Selecting a plurality of heavily doped P-type silicon wafers, splitting the silicon wafers into two wafers, and defining the two wafers split from the same silicon wafer as a control group silicon wafer and an experimental group silicon wafer; A plurality of control group silicon wafers are subjected to a two-stage heat treatment, including heat treatment at 780° C. for 3 hours under oxygen conditions, and then heated to 1000° C. at a set heating rate, and heat treated at 1000° C. for 16 hours, and the BMD density and BMD size of each control group silicon wafer are obtained; Measuring the silicon wafers in the experimental group using the measurement method according to any one of claims 1 to 8 to obtain the BMD density and BMD size of each silicon wafer in the experimental group; The BMD density and BMD size of the control group silicon wafers and the experimental group silicon wafers that are split from the same silicon wafer are compared to obtain target data with the relative difference in BMD size remaining unchanged and the largest relative difference in BMD density. The heat treatment conditions of the experimental group silicon wafers corresponding to the target data are the optimal BMD heat treatment conditions.

10. The method for obtaining optimal heat treatment conditions for BMD growth on silicon wafers according to claim 9, characterized in that: The comparing the BMD density and BMD size of a control group of silicon wafers and an experimental group of silicon wafers obtained by splitting a plurality of the same silicon wafers comprises: Obtaining the coordinates of the silicon wafers of the control group and the experimental group through the detection system; The BMD density and BMD size of the control group silicon wafer and the experimental group silicon wafer with the same coordinates were compared.

11. A system for obtaining optimal conditions for heat treatment of BMD growth on a silicon wafer, comprising: An acquisition module is used to acquire the BMD density and BMD size of each control group silicon wafer; acquire the BMD density and BMD size of each experimental group silicon wafer; The comparison module is used to compare the BMD density and BMD size of a control group silicon wafer and an experimental group silicon wafer that are split from a plurality of the same silicon wafers, and obtain target data with the relative difference of BMD size remaining unchanged and the relative difference of BMD density being the largest. The heat treatment condition of the experimental group silicon wafer corresponding to the target data is the optimal BMD heat treatment condition.

12. A computer-readable medium having a program stored thereon, characterized in that: include: When the program is executed, at least part of the steps in the method for obtaining optimal conditions for BMD heat treatment as claimed in claim 9 or 10 are performed.

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