Method for simply and rapidly detecting defect density of silicon single crystal LDP

Abstract

The present application belongs to the technical field of semiconductor silicon single crystal defect detection, and particularly relates to a method for simply and rapidly detecting LDP defect density of silicon single crystal, which comprises the following steps: smearing copper nitrate solution on the surface of the silicon single crystal sample after cleaning, and performing high-temperature heat treatment on the silicon single crystal sample for a first preset time length; using mixed acid solution to etch the silicon single crystal sample after cooling for a second preset time length; using deionized water to wash away the mixed acid solution remaining on the surface of the silicon single crystal sample; and placing the silicon single crystal sample in a preferential etching solution for preferential etching for a third preset time length, and then using deionized water to clean the preferential etching solution on the surface of the silicon single crystal sample, so that the surface of the silicon single crystal sample with defects presents a clear and regular edge center aggregation ring or radius ring, and if the silicon single crystal sample has LDP defects, the LDP defect density can be calculated through the ring width of the center aggregation ring or radius ring, thereby improving the accuracy of the detection of the LDP defect density of the silicon single crystal.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor silicon single crystal defect detection, and in particular relates to a method for simply and quickly detecting the LDP defect density of a silicon single crystal. Background Art

[0002] In the field of semiconductor materials, silicon single crystals serve as the foundation of integrated circuits, and their quality directly determines their performance and reliability. However, various defects can arise during the growth and processing of silicon single crystals. Large dislocation pits (LDPs) are a typical interstitial silicon atom defect, primarily occurring in I-rich (interstitial-rich) regions of silicon single crystals.

[0003] LDP defects have a significant impact on integrated circuits. They not only reduce IC yield but also impact their electrical performance and reliability, thereby increasing production costs and reducing product competitiveness. Therefore, accurate and rapid detection and evaluation of LDP defects is crucial for improving silicon single crystal quality and ensuring integrated circuit performance. However, different manufacturers have varying requirements for the severity of LDP defects in silicon single crystals. LDP defect density is a key indicator of LDP defect severity. A higher LDP defect density indicates more severe LDP defects, while a lower LDP defect density indicates fewer LDP defects.

[0004] The traditional method for evaluating LDP defect density requires processing the silicon wafer into a polished state, then performing microscopic inspection under a microscope, and then manually counting the specific number of LDPs to calculate the density. This method takes a long time to detect and the accuracy of manual density counting is low. Summary of the Invention

[0005] In view of this, the present invention provides a method for simply and quickly detecting the LDP defect density of a silicon single crystal, so as to solve the technical problems of long detection time and low accuracy in the prior art.

[0006] To achieve the above objectives, this application adopts the following scheme:

[0007] A method for simply and quickly detecting LDP defects in silicon single crystals comprises the following steps:

[0008] S10. Cleaning the silicon single crystal sample to be tested;

[0009] S20 copper ion concentration of 700 ppma to 1000 ppma of copper nitrate solution is applied to the surface of the cleaned silicon single crystal sample, and then dried naturally;

[0010] S30. The dried silicon single crystal sample is subjected to a high-temperature heat treatment for a first preset time to diffuse the copper ions on the silicon single crystal sample, wherein the high-temperature heat treatment temperature is a first preset temperature, and then naturally cooled to room temperature;

[0011] S40. Cleaning the cooled silicon single crystal sample using a mixed acid solution for a second preset time to remove the copper nitrate solution and oxide film on the surface of the silicon single crystal sample;

[0012] S50 using deionized water to clean the silicon single crystal sample to remove the residual mixed acid solution on the surface of the silicon single crystal sample;

[0013] S60. The cleaned silicon single crystal sample is placed in a preferential etching solution and preferentially corroded for a third preset time;

[0014] S70. After the preferential etching, the surface of the silicon single crystal sample is cleaned of the preferential etching solution using deionized water and observed. If a central aggregation ring or a radius ring is present on the silicon single crystal sample, the silicon single crystal sample has an LDP defect. If no central aggregation ring or radius ring is present on the silicon single crystal sample, the silicon single crystal sample does not have an LDP defect.

[0015] S80. Measuring the width of the central aggregation ring or the radius ring presented on the silicon single crystal sample, and calculating the LDP defect density based on the ring width, the LDP defect density is calculated by the following formula:

[0016] y=0.1131x-1.4485

[0017] Where: y is the LDP defect density and x is the ring width.

[0018] Preferably, in the step S10, the "cleaning the silicon single crystal sample to be tested" includes: using an alkaline cleaning solution to perform alkaline cleaning on the silicon single crystal sample to remove dirt and grease on the surface of the silicon single crystal sample.

[0019] Preferably, the alkaline washing solution is a NaOH solution with a mass concentration of 8% to 10%.

[0020] Preferably, in the step S20, the ratio of the mass of the copper nitrate solution applied to the surface of the silicon single crystal sample to the area of ​​the silicon single crystal sample is (2g to 3g): 7cm 2 .

[0021] Preferably, in S30, the first preset temperature is 850°C to 950°C.

[0022] Preferably, in S30, the first preset time length is 3 minutes to 5 minutes.

[0023] Preferably, in S40, the second preset time length is 3 minutes to 5 minutes.

[0024] Preferably, in S60, the preferential etching solution is Wright, and the Wright is composed of HF, HAc, CrO3, HNO3, and Cu(NO3)•3H2O with a mass concentration of 49%.

[0025] Preferably, in S60, the third preset time length is 1 min to 5 min.

[0026] Preferably, in S40, the mixed acid solution includes: HF with a mass concentration of 49%, HNO3 with a mass concentration of 70%, CH3COOH with a mass concentration of 99%, and H2O, and the proportions of HF, HNO3, CH3COOH, and H2O in the mixed acid solution are (10% to 15%): (20% to 35%): (10% to 20%): (20% to 40%).

[0027] In the above-mentioned method for simply and quickly detecting the LDP defect density of silicon single crystals, copper nitrate solution is applied to the surface of the cleaned silicon single crystal sample, and a high-temperature heat treatment is performed on it for a first preset time to diffuse the copper ions on the silicon single crystal sample, and a mixed acid solution is used to corrode the cooled silicon single crystal sample for a second preset time to remove the copper nitrate solution and the oxide film on the surface of the silicon single crystal sample, and deionized water is used to wash away the residual mixed acid solution on the surface of the silicon single crystal sample, and the sample is placed in a preferential etching solution for preferential etching for a third preset time to reveal the defects inside the silicon single crystal sample, and then deionized water is used to clean the preferential etching solution on the surface of the silicon single crystal sample. The above steps make the silicon single crystal sample with defects The surface of the crystal sample presents a clear central aggregation ring or radius ring with regular edges. After the inspection, it is only necessary to observe macroscopically whether the silicon single crystal surface presents a central aggregation ring or radius ring to determine whether the silicon single crystal sample has LDP defects. If there is an LDP defect, the LDP defect density is calculated by the ring width of the central aggregation ring or radius ring. Compared with the detection method in the prior art, this method does not need to process the silicon single crystal sample into a polished sheet, thereby improving the efficiency of silicon single crystal LDP defect density detection, and does not need to use a microscope to perform microscopic inspection on the silicon single crystal sample processed into a polished sheet, and manually count the specific number of LDPs, thereby avoiding large errors in manual counting, thereby improving the accuracy of silicon single crystal LDP defect density detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of a silicon single crystal sample showing a central aggregation ring in the present invention.

[0029] Figure 2Schematic diagram showing the radius ring of the silicon single crystal sample in the present invention.

[0030] Figure 3 This is a correlation diagram between the ring width and the LDP defect density in the present invention. DETAILED DESCRIPTION

[0031] To facilitate understanding of the present application, a more comprehensive description of the present application will be provided below with reference to the accompanying drawings. Preferred embodiments of the present application will also be described. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] A method for simply and quickly detecting LDP defects in silicon single crystals comprises the following steps:

[0034] S10. Clean the silicon single crystal sample to be tested, which is a 1 / 4 slug silicon wafer (12 inches), to remove surface dirt and oil to prevent the dirt and oil attached to the surface from affecting the accuracy of the test;

[0035] S20. Apply a copper nitrate solution having a copper ion concentration of 700 to 1000 ppma to the surface of the cleaned silicon single crystal sample and allow the copper nitrate solution on the surface of the silicon single crystal sample to dry naturally for 2 to 4 minutes. Place the silicon single crystal sample with the inscribed surface facing upward on a piece of dust-free paper to prevent stains on the surface of the silicon single crystal from being contaminated by placing it directly on a table.

[0036] S30. Heat treating the dried silicon single crystal sample at high temperature for a first preset time to diffuse the copper ions on the silicon single crystal sample. The temperature during the high-temperature heat treatment is the first preset temperature, followed by natural cooling to room temperature. Specifically, the dried silicon single crystal sample can be placed on a quartz boat. When the temperature of the muffle furnace reaches the first preset temperature, the quartz boat is placed in the muffle furnace using a quartz boat fork. After the high-temperature heat treatment for a second time, the quartz boat is removed.

[0037] S40. Cleaning the cooled silicon single crystal sample using a mixed acid solution for a second preset time to remove the copper nitrate solution and oxide film on the surface of the silicon single crystal sample;

[0038] S50 using deionized water to clean the silicon single crystal sample to remove the residual mixed acid solution on the surface of the silicon single crystal sample;

[0039] S60. The cleaned silicon single crystal sample is placed in a preferential etching solution and preferentially corroded for a third preset time;

[0040] S70. After the preferential etching, the preferential etching solution on the surface of the silicon single crystal sample is cleaned with deionized water and observed (by macroscopic observation with the naked eye). If the silicon single crystal sample shows a central agglomeration ring or a radius ring, the silicon single crystal sample has LDP defects. If the silicon single crystal sample does not show such a ring, the silicon single crystal sample has LDP defects. Figure 1 and Figure 2 If the central aggregation ring or radius ring shown in , the silicon single crystal sample does not have LDP defects;

[0041] S80. Measuring the width of the central aggregation ring or the radius ring presented on the silicon single crystal sample, and calculating the LDP defect density based on the ring width, the LDP defect density is calculated by the following formula:

[0042] y=0.1131x-1.4485

[0043] Wherein: y is the LDP defect density, x is the ring width, and the 0.1131 and -1.4485 are coefficients calibrated through multiple experiments. Therefore, the LDP defect density calculated using this formula is highly accurate.

[0044] In the above-mentioned method for simply and quickly detecting the LDP defect density of silicon single crystals, a copper nitrate solution is applied to the surface of the cleaned silicon single crystal sample, and a high-temperature heat treatment is performed on it for a first preset time to diffuse the copper ions on the silicon single crystal sample. A mixed acid solution is used to corrode the cooled silicon single crystal sample for a second preset time to remove the copper nitrate solution and the oxide film on the surface of the silicon single crystal sample. Deionized water is used to wash away the residual mixed acid solution on the surface of the silicon single crystal sample, and the sample is placed in a preferential etching solution for preferential etching for a third preset time to reveal the defects inside the silicon single crystal sample. Deionized water is then used to etch the surface of the silicon single crystal sample. The silicon single crystal sample is cleaned with the preferential etching solution, and its surface is macroscopically observed to see whether a central aggregation ring or a radius ring is present, so as to determine whether it has LDP defects. If it has LDP defects, the LDP defect density is calculated by the ring width of the central aggregation ring or the radius ring. Compared with the detection method in the prior art, the present method does not need to process the silicon single crystal sample into a polished sheet, thereby improving the efficiency of the silicon single crystal LDP defect density detection, and does not need to use a microscope to perform microscopic detection on the silicon single crystal sample processed into a polished sheet, and manually count the specific number of LDPs, thereby avoiding large errors in manual counting, thereby improving the accuracy of the silicon single crystal LDP defect density detection.

[0045] Wherein, in said S10, said "cleaning the silicon single crystal sample to be tested" includes: using an alkaline cleaning solution to perform alkaline cleaning on the silicon single crystal sample to remove dirt and grease on the surface of the silicon single crystal sample.

[0046] Preferably, the alkaline washing solution is a NaOH solution with a mass concentration of 8% to 10%.

[0047] Specifically, in S20, if the amount of the copper nitrate solution applied is too small, the above effect cannot be achieved, and if the amount of the copper nitrate solution applied is too large, resources will be wasted. Therefore, the ratio of the mass of the copper nitrate solution applied to the surface of the silicon single crystal sample to the area of ​​the silicon single crystal sample is 2g to 3g:7cm 2 Make the effect better.

[0048] Specifically, in S30, the first preset temperature is 850°C to 950°C; the first preset time is 3 min to 5 min; in S40, the second preset time is 3 min to 5 min; in S60, the third preset time is 1 min to 5 min.

[0049] Among them, in the S60, the preferred etching solution is wright, which is prepared according to the national standard ratio and consists of HF, HAc, CrO3, HNO3, and Cu(NO3)•3H2O with a mass concentration of 49%.

[0050] In S40, the mixed acid solution includes: HF with a mass concentration of 49%, HNO3 with a mass concentration of 70%, CH3COOH with a mass concentration of 99%, and H2O. The proportions of HF, HNO3, CH3COOH, and H2O in the mixed acid solution are (10% to 15%): (20% to 35%): (10% to 20%): (20% to 40%).

[0051] The following is a detailed description of the technical solutions and effects of the present invention. It should be noted that the following examples are only intended to further explain the present invention and do not limit the technical solutions of the present invention.

[0052] Experimental Example 1

[0053] Step 1: Take a 12-inch sample with LDP defect density measured by traditional methods and cleave it into four quarter-sized single crystal silicon samples. Take one of them for testing, clean the single crystal silicon sample with an 8% mass concentration NaOH solution as an alkaline cleaning solution, and then clean the NaOH solution on the surface of the single crystal silicon sample with deionized water;

[0054] Step 2: Place the cleaned single crystal silicon sample with the lettering facing up on a piece of dust-free paper, and apply a copper nitrate solution with a copper ion concentration of 700 ppma to 1000 ppma to the surface of the silicon single crystal sample. The ratio of the mass of the copper nitrate solution to the area of ​​the silicon single crystal sample is 2 g:7 cm 2 , let it stand for 2 minutes to dry;

[0055] Step 3: Place the single crystal silicon sample on a quartz boat. When the temperature of the muffle furnace rises to 900°C, use a quartz boat fork to place the quartz boat in the muffle furnace. After heat treatment for 4 minutes, take out the quartz boat and allow the single crystal silicon sample to cool naturally to room temperature.

[0056] Step 4: Clean the cooled silicon single crystal sample for 2 minutes using a mixed acid solution to remove the copper nitrate solution and oxide film on the surface of the silicon single crystal sample. The mixed acid solution comprises: HF with a mass concentration of 49%, HNO3 with a mass concentration of 70%, CH3COOH with a mass concentration of 99%, and H2O. The proportions of HF, HNO3, CH3COOH, and H2O in the mixed acid solution are 12%:32%:18%:38%;

[0057] Step 5: Cleaning the silicon single crystal sample with deionized water to remove the mixed acid solution remaining on the surface of the silicon single crystal sample;

[0058] Step 6: placing the cleaned silicon single crystal sample in a selective etching solution for selective etching for 4 minutes to reveal defects in the silicon single crystal sample;

[0059] Step 7: Clean the silicon single crystal sample with deionized water, blow off the water droplets on the surface with a water gun, and then send it to the darkroom of the inspection room for inspection. The central aggregation ring is shown on the silicon single crystal sample, indicating that the silicon single crystal sample has LDP defects;

[0060] Step 8: Measure the width of the central clustering ring on the silicon single crystal sample, which is 40 mm, and calculate the LDP defect density according to the following formula:

[0061] y=0.1131x-1.4485

[0062] Where: y is the LDP defect density, x is the ring width

[0063] The calculation results are as follows Figure 3 As shown, the method provided in this embodiment can not only determine the presence of LDP defects through macroscopic analysis with 100% accuracy, but also calculate the LDP defect density through ring width. Since this embodiment uses a truncated silicon single crystal rough slice as the silicon single crystal sample, the surface condition is poor. If the traditional detection method is used, the detection results will be affected by the interference of surface damage, resulting in low accuracy. However, the method provided in this embodiment uses a copper pendant and then selectively corrodes to observe defects in the silicon wafer body. This method is not affected by the surface condition and does not require the use of a microscope to manually count the specific number of LDPs to calculate the LDP defect density. A clear pattern can be observed only through macroscopic analysis, and the LDP defect density can be calculated through the ring width of the pattern, thereby improving detection efficiency and accuracy.

[0064] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should all be included in the scope of protection of the present invention.

Claims

1. A method for simply and quickly detecting the LDP defect density of a silicon single crystal, characterized in that: The following steps are involved: S10. Cleaning the silicon single crystal sample to be tested; S20 copper ion concentration of 700 ppma to 1000 ppma of copper nitrate solution is applied to the surface of the cleaned silicon single crystal sample, and then dried naturally; S30. The dried silicon single crystal sample is subjected to a high-temperature heat treatment for a first preset time to diffuse the copper ions on the silicon single crystal sample, wherein the high-temperature heat treatment temperature is a first preset temperature, and then naturally cooled to room temperature; S40. Cleaning the cooled silicon single crystal sample with a mixed acid solution for a second predetermined time to remove the copper nitrate solution and oxide film on the surface of the silicon single crystal sample, wherein the ratio of HF, HNO3, CH3COOH, and H2O in the mixed acid solution is (10% to 15%): (20% to 35%): (10% to 20%): (20% to 40%). S50 using deionized water to clean the silicon single crystal sample to remove the residual mixed acid solution on the surface of the silicon single crystal sample; S60. Placing the cleaned silicon single crystal sample in a preferential etching solution for preferential etching for a third preset time, wherein the preferential etching solution is wright, and the wright comprises HF, HAc, CrO3, HNO3, and Cu(NO3)•3H2O; S70. After the preferential etching, the surface of the silicon single crystal sample is cleaned of the preferential etching solution using deionized water and observed. If a central aggregation ring or a radius ring is present on the silicon single crystal sample, the silicon single crystal sample has an LDP defect. If no central aggregation ring or radius ring is present on the silicon single crystal sample, the silicon single crystal sample does not have an LDP defect. S80. Measuring the width of the central aggregation ring or the radius ring presented on the silicon single crystal sample, and calculating the LDP defect density based on the ring width, the LDP defect density is calculated by the following formula: y=0.1131x-1.4485 Where: y is the LDP defect density and x is the ring width.

2. The method for simply and quickly detecting the LDP defect density of a silicon single crystal according to claim 1, characterized in that: In the S10, the "cleaning the silicon single crystal sample to be tested" includes: using an alkaline cleaning solution to perform alkaline cleaning on the silicon single crystal sample to remove dirt and grease on the surface of the silicon single crystal sample.

3. The method for simply and quickly detecting the LDP defect density of a silicon single crystal according to claim 2, characterized in that: The alkaline washing solution is a NaOH solution with a mass concentration of 8% to 10%.

4. The method for simply and quickly detecting the LDP defect density of a silicon single crystal according to claim 1, characterized in that: In the step S20, the ratio of the mass of the copper nitrate solution applied to the surface of the silicon single crystal sample to the area of ​​the silicon single crystal sample is (2 g to 3 g): 7 cm 2 .

5. The method for simply and quickly detecting the LDP defect density of a silicon single crystal according to claim 1, characterized in that: In the step S30 , the first preset temperature is 850° C. to 950° C.

6. The method for simply and quickly detecting the LDP defect density of a silicon single crystal according to claim 1, wherein: In S30, the first preset duration is 3 minutes to 5 minutes.

7. The method for simply and quickly detecting the LDP defect density of a silicon single crystal according to claim 1, wherein: In the S40, the second preset time length is 3 minutes to 5 minutes.

8. The method for simply and quickly detecting the LDP defect density of a silicon single crystal according to claim 1, wherein: In S60, the third preset time length is 1 minute to 5 minutes.

9. The method for simply and quickly detecting the LDP defect density of a silicon single crystal according to claim 1, characterized in that: In the S40, the mixed acid solution includes: HF with a mass concentration of 49%, HNO3 with a mass concentration of 70%, CH3COOH with a mass concentration of 99%, and H2O.

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