Method and system for detecting defects in a single crystal silicon ingot
By cutting silicon wafers from single-crystal silicon rods and then subjecting them to acid and SECCO etching to reveal defects, combined with visual and microscopic inspection, the problem of identifying NDP defects was solved, and the yield of silicon wafers was improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAN ESWIN MATERIAL TECHNOLOGY CO LTD
- Filing Date
- 2022-12-13
- Publication Date
- 2026-05-12
AI Technical Summary
Existing technologies struggle to identify and detect novel defects (NDPs) in single-crystal silicon rods caused by nitrogen nucleus precipitation. These defects affect silicon wafer performance and cannot be identified using traditional FPD and LDP detection methods.
The silicon wafer to be tested is prepared by cutting from the P-band region of a single-crystal silicon rod, thinning it by acid etching, and then etching with SECCO etching solution to reveal defects. The defect characteristics are then detected by visual inspection and microscopy to determine whether they are NDP defects.
It enables accurate identification of NDP defects, preventing defective silicon wafers from being shipped out and improving silicon wafer yield.
Smart Images
Figure CN115931863B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of silicon wafer defect detection technology, and more particularly to a method and system for detecting defects in single-crystal silicon rods. Background Technology
[0002] Single-crystal silicon rods prepared using the magnetic-field-applied Czochralski method (MCZ) often exhibit various crystal defects. Based on their formation mechanisms, these defects are typically categorized into vacancy defects and interstitial defects. After the crystal pulling process, preferential etching is generally performed to determine whether the single-crystal silicon rod contains flow pattern defects (FPD) and large dislocation pits (LDP). These two types of defects are also important criteria for determining whether the single-crystal silicon rod is crystal-original particle-free (COP).
[0003] With the gradual development of crystal pulling technology and the increasingly stringent requirements for bulk microdefects (BMDs) in silicon wafers, nitrogen-doped silicon (SiN) wafers are sometimes used during the crystal pulling process to control the number of BMDs and thus the internal getter capability of the silicon wafer. This is a common production method in epitaxial products. During this process, it was discovered that as the nitrogen content in the single-crystal silicon rod increases, a novel defect, different from FPDs and LDPs, appears in the P-band region where FPDs and LDPs do not occur. This defect occurs at locations with high pulling speeds and high nitrogen concentrations and can affect the performance of the silicon wafer, such as causing PN junction leakage, short circuits in slotted capacitors, or insulation failure. Therefore, this defect must be detected and identified in the single-crystal silicon rod to prevent silicon wafers containing this defect from being produced. Summary of the Invention
[0004] In view of this, embodiments of the present invention aim to provide a method and system for detecting defects in single-crystal silicon rods; capable of identifying nitrogen-generated defects (NDPs) during the detection stage of single-crystal silicon rods, thereby avoiding the possibility of defective silicon wafers being shipped out.
[0005] The technical solution of this invention is implemented as follows:
[0006] In a first aspect, embodiments of the present invention provide a method for detecting defects in a single-crystal silicon rod, the detection method comprising:
[0007] The silicon wafer to be tested is prepared by cutting the P-band region of a single-crystal silicon rod;
[0008] The silicon wafer to be tested is subjected to acid etching to reduce the surface thickness of the silicon wafer to remove the damaged layer on the surface of the silicon wafer.
[0009] The thinned silicon wafer to be tested was etched with SECCO etching solution to expose the defects in the silicon wafer to be tested.
[0010] Defects in the silicon wafer under test are detected, and when the characteristics of the defect meet the set conditions, it is determined to be an NDP defect.
[0011] Secondly, embodiments of the present invention provide a defect detection system for a single-crystal silicon rod, the detection system comprising:
[0012] A cutting device for cutting from the P-band region of a single-crystal silicon rod to prepare a silicon wafer to be tested;
[0013] An acid etching apparatus is used to perform acid etching on the silicon wafer to be tested to reduce the surface thickness of the silicon wafer to remove the damaged layer on the surface of the silicon wafer.
[0014] The SECCO etching apparatus is used to etch the thinned silicon wafer under test with SECCO etching solution to expose defects in the silicon wafer under test.
[0015] A detection device is used to detect defects in the silicon wafer under test, and when the characteristics of the defect meet the set conditions, it is determined to be an NDP defect.
[0016] This invention provides a method and system for detecting defects in monocrystalline silicon rods. After cutting the monocrystalline silicon rod to obtain a silicon wafer for testing and performing acid etching, the wafer is then etched again using a SECCO etching solution to expose defects. These defects are then detected, and the presence of nitrogen-doped silicon (NDP) defects in the monocrystalline silicon rod is confirmed when the characteristics of the defects meet predefined criteria. The detection method provided by this invention clearly identifies the characteristics of NDP defects and promptly detects them in nitrogen-doped monocrystalline silicon rods, preventing substandard silicon wafers from entering the market and improving wafer yield. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the internal defect distribution of a nitrogen-doped single-crystal silicon rod provided in an embodiment of the present invention;
[0018] Figure 2 This is a schematic flowchart of a method for detecting defects in a single-crystal silicon rod according to an embodiment of the present invention.
[0019] Figure 3 This is a schematic diagram of defects on the surface of a silicon wafer under visual inspection, provided in an embodiment of the present invention.
[0020] Figure 4 A schematic diagram of a ring-shaped NDP defect distribution provided in an embodiment of the present invention;
[0021] Figure 5 Another schematic diagram of a ring-shaped NDP defect distribution provided in an embodiment of the present invention;
[0022] Figure 6 A schematic diagram of NDP defect distribution in a combination of ring and disk shapes is provided for an embodiment of the present invention;
[0023] Figure 7 A schematic diagram of a disk-shaped NDP defect distribution provided in an embodiment of the present invention;
[0024] Figure 8 This is a schematic diagram of the NDP defect morphology provided in an embodiment of the present invention;
[0025] Figure 9 This is an enlarged schematic diagram of the NDP defect morphology provided in an embodiment of the present invention;
[0026] Figure 10 This is a schematic diagram of NDP defect density distribution provided in an embodiment of the present invention;
[0027] Figure 11 This is a schematic diagram of the NDP defect diameter provided in an embodiment of the present invention;
[0028] Figure 12 This is a schematic diagram of a defect detection system in a single-crystal silicon rod provided in an embodiment of the present invention. Detailed Implementation
[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
[0030] See Figure 1 This shows a diagram of the internal defect distribution of a nitrogen-doped single-crystal silicon rod. Specifically, as shown... Figure 1 As shown, the BMD density in a single-crystal silicon rod is equal to or greater than 1×10⁻⁶. 8 pcs / cm 3 The region is defined as containing an oxygen evolution-promoting region (hereinafter referred to as the "Pv region"), an OSF region, and a vacancy-rich region (hereinafter referred to as the "V-rich region"). The OSF region is also called the P-band region. Meanwhile, the BMD density is less than 1 × 10⁻⁶. 8 pcs / cm 3The region is defined as including the oxygen evolution suppression region (hereinafter referred to as the "Pi region"), the B-band region (hereinafter referred to as the "B-band region"), and the interstitial silicon enrichment region (hereinafter referred to as the "I-rich region"); while in the P region... V Region and P i The V / G value at the boundary location between regions is defined as (V / G) critical.
[0031] It has been discovered that with the gradual increase of nitrogen content, a novel defect appears in the P-band region where FPD and LDP do not occur. This defect has a significant impact on the performance of silicon wafers fabricated from monocrystalline silicon rods. Since this defect mainly occurs in the high-nitrogen-concentration portion of the monocrystalline silicon rod and is generated by nitrogen nucleus precipitation, it is called a nitrogen-generated defect (NDP). However, NDP defects cannot be identified using FPD and LDP detection methods. Therefore, this invention aims to provide a method for detecting NDP defects in monocrystalline silicon rods to promptly identify the defect during the monocrystalline silicon rod inspection stage, thereby preventing defective products from being exported.
[0032] See Figure 2 This invention illustrates a method for detecting defects in a single-crystal silicon rod according to an embodiment of the present invention. The detection method includes:
[0033] S201. Cutting the P-band region of a single-crystal silicon rod to prepare the silicon wafer to be tested;
[0034] S202. The silicon wafer to be tested is subjected to acid etching to reduce the surface thickness of the silicon wafer to remove the damaged layer on the surface of the silicon wafer.
[0035] S203. The thinned silicon wafer to be tested is etched with SECCO etching solution to make the defects in the silicon wafer to be tested visible.
[0036] S204. Detect defects in the silicon wafer to be tested, and determine that the defect is an NDP defect when the characteristics of the defect meet the set conditions.
[0037] for Figure 2 The technical solution described involves cutting a single-crystal silicon rod to obtain a silicon wafer for testing, followed by acid etching. Then, a SECCO etching solution is used to etch the silicon wafer again, revealing defects. These defects are then detected, and if the characteristics of the defects meet predefined criteria, the presence of NDP defects in the single-crystal silicon rod can be confirmed. The detection method provided by this invention clearly identifies the characteristics of NDP defects and promptly detects them in nitrogen-doped single-crystal silicon rods, preventing substandard silicon wafers from entering the market and improving wafer yield.
[0038] for Figure 2 In some possible implementations of the technical solution shown, the step of acid etching the silicon wafer under test to reduce its surface thickness and remove the damaged layer on the surface of the silicon wafer under test includes:
[0039] The silicon wafer under test was subjected to acid etching treatment using an etching solution composed of HF solution with a mass concentration of 29% to 49% and HNO3 solution with a mass concentration of 40% to 70% at a volume ratio of 1:10 to 2:5, so that the surface thickness of the silicon wafer under test was reduced by more than 150 μm.
[0040] In some examples of the above implementation, the acid corrosion duration is 1 min to 2 min, and the corrosion rate is controlled at 100 μm / min to 150 μm / min.
[0041] Preferably, in the specific implementation process, the above-mentioned acidic corrosion solution is prepared by mixing 49% HF solution and 70% HNO3 solution at a volume ratio of 1:5.
[0042] It should be noted that acid etching of the silicon wafer surface can remove metallic impurities and the oxide film, preventing interference with subsequent testing. Furthermore, in practice, to ensure the etching rate is controlled between 100 μm / min and 150 μm / min, the concentrations and mixing volume ratios of the HF and HNO3 solutions can be adjusted according to the specific circumstances.
[0043] for Figure 2 In some possible implementations of the technical solution, the step of etching the thinned silicon wafer with SECCO etching solution to expose defects in the silicon wafer includes:
[0044] The thinned silicon wafer was etched using a SECCO etching solution, which is a mixture of 29%–49% HF solution and 60%–100% K2CrO4 solution in a volume ratio of 1:5 to 1:2, so that the surface thickness of the silicon wafer was further reduced by more than 20 μm, thereby revealing the defect.
[0045] In some examples of the above implementation, the continuous corrosion time of the SECCO corrosion solution is 5 min to 20 min, and the corrosion rate is controlled at 1 μm / min to 1.4 μm / min.
[0046] Preferably, in the specific implementation process, the above-mentioned SECCO corrosion solution is prepared by mixing 49% HF solution and 60% K2CrO4 solution at a volume ratio of 1:5.
[0047] It should be noted that when etching the silicon wafer under test with SECCO etching solution after acid etching, the etching time can be selected according to the thickness of the silicon wafer under test so that the surface of the silicon wafer under test is etched to more than 20μm, thereby enabling the NDP defect to be detected.
[0048] for Figure 2 In some possible implementations of the technical solution shown, the step of detecting defects in the silicon wafer under test, and determining that the defect is an NDP defect when its characteristics meet set conditions, includes:
[0049] The silicon wafer to be tested, after being thinned again, is placed under a visual inspection device for visual inspection to observe whether there are high-density and symmetrical defect clusters on the surface of the silicon wafer to be tested.
[0050] When a cluster of defects with a high density and symmetrical pattern appears on the surface of the silicon wafer under test, the distribution, morphology and density of the defects are detected by microscope. When the distribution, morphology and density of the defects all meet the set conditions, the defects are determined to be NDP defects.
[0051] In some examples of the above implementation, when a high-density, symmetrically patterned defect cluster appears on the surface of the silicon wafer under test, the distribution, morphology, and density of the defects are detected using a microscope. When the distribution, morphology, and density of the defects all meet the set conditions, the defects are determined to be NDP defects, including:
[0052] When a high-density, symmetrically patterned defect cluster appears on the surface of the silicon wafer under test, the defect is determined to be an NDP defect if the characteristics of the defect simultaneously meet the following three conditions:
[0053] The defects are distributed in a disk-shaped, ring-shaped, or a combination of disk-shaped and ring-shaped patterns.
[0054] The defect is described as a black, circular hole with a metallic luster at the center and no bright spots of any particular shape.
[0055] The density of the defect is greater than 100 ea / cm 2 .
[0056] Specifically, the aforementioned visual inspection device can be a high-brightness lamp. When the etched silicon wafer is placed under the high-brightness lamp, visual inspection is performed to observe... Figure 3When the surface of the silicon wafer under test has a high density of defects in a symmetrical pattern (as indicated by the solid arrow in the figure), it indicates that the silicon wafer under test may have NDP defects.
[0057] On the other hand, to determine whether a symmetrically patterned defect in the silicon wafer under test is an NDP defect, the wafer needs to be observed and inspected under a microscope. When scanning along the diameter of the silicon wafer, the defect is determined to be an NDP defect if the wafer meets the following three conditions:
[0058] (1) Specifically, as follows Figures 4 to 7 As shown, the defects are distributed in a disc-shaped, annular, or combination of disc-shaped and annular patterns.
[0059] (2) Figure 8 As shown, the defect is a black circular hole (indicated by the solid arrow in the image), and as... Figure 9 As shown, the center of the defect exhibits a metallic luster and has no bright spots of a special shape;
[0060] (3) Figure 10 As shown, the defect density is greater than 100 ea / cm². 2 .
[0061] In some examples of the above implementations, the diameter of the NDP defect is 5μm to 12μm. It should be noted that the diameter of the NDP defect will vary depending on the duration of the corrosion. Figure 11 As shown, the diameter of the NDP defect in this embodiment of the invention is 8.3 μm.
[0062] See Figure 12 This illustrates the composition of a defect detection system 120 in a single-crystal silicon rod provided by an embodiment of the present invention. The detection system 120 includes:
[0063] Cutting device 1201, the cutting device is used to cut from the P-band region of a single crystal silicon rod to prepare a silicon wafer to be tested;
[0064] An acid etching apparatus 1202 is used to perform acid etching on the silicon wafer to be tested to reduce the surface thickness of the silicon wafer to remove the damaged layer on the surface of the silicon wafer.
[0065] The SECCO etching apparatus 1203 is used to etch the thinned silicon wafer under test with SECCO etching solution so that defects in the silicon wafer under test can be revealed.
[0066] The detection device 1204 is used to detect defects in the silicon wafer under test, and when the characteristics of the defect meet the set conditions, it is determined to be an NDP defect.
[0067] In some examples, the detection device 1204 includes a visual inspection device 12041 and a microscopic inspection device 12042; wherein,
[0068] The visual inspection device 12041 is used to observe whether there are high-density and symmetrical defect clusters on the surface of the silicon wafer to be tested.
[0069] The microscopic inspection device 12042 is used to detect the distribution, morphology and density of defects with high density and symmetrical pattern on the surface of the silicon wafer under test using a microscope. When the distribution, morphology and density of the defects meet the set conditions, the defects are determined to be NDP defects.
[0070] It should be noted that the technical solutions described in the embodiments of the present invention can be combined arbitrarily without conflict.
[0071] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A method for detecting defects in a single-crystal silicon rod, characterized in that, The detection method includes: The silicon wafer to be tested is prepared by cutting the P-band region of a single-crystal silicon rod; The silicon wafer to be tested is subjected to acid etching to reduce the surface thickness of the silicon wafer to remove the damaged layer on the surface of the silicon wafer. The thinned silicon wafer to be tested was etched with SECCO etching solution to expose the defects in the silicon wafer to be tested. Defects in the silicon wafer under test are detected, and when the characteristics of the defect meet the set conditions, it is determined to be an NDP defect. The process includes detecting defects in the silicon wafer under test, and classifying a defect as an NDP defect when its characteristics meet set conditions, including: When a high-density, symmetrically patterned cluster of defects appears on the surface of the silicon wafer under test, the defect is determined to be an NDP defect if the characteristics of the defect simultaneously meet the following three conditions: The defects are distributed in a disk-shaped, ring-shaped, or a combination of disk-shaped and ring-shaped patterns. The defect is described as a black, circular hole with a metallic luster at the center and no bright spots of any particular shape. The density of the defects is greater than 100ea / cm².
2. The detection method according to claim 1, characterized in that, The step of acid etching the silicon wafer under test to reduce its surface thickness and remove the damaged layer on the surface of the silicon wafer includes: The silicon wafer under test was subjected to acid etching treatment using an etching solution composed of HF solution with a mass concentration of 29% to 49% and HNO3 solution with a mass concentration of 40% to 70% at a volume ratio of 1:10 to 2:5, so that the surface thickness of the silicon wafer under test was reduced by more than 150µm.
3. The detection method according to claim 2, characterized in that, The duration of the acidic corrosion is 1 min to 2 min, and the corrosion rate is controlled at 100 µm / min to 150 µm / min.
4. The detection method according to claim 1, characterized in that, The step of etching the thinned silicon wafer with SECCO etching solution to expose defects in the silicon wafer includes: The thinned silicon wafer was etched using a SECCO etching solution, which is a mixture of 29% to 49% HF solution and 60% to 100% K2CrO4 solution in a volume ratio of 1:5 to 1:2, so that the surface thickness of the silicon wafer was further reduced by more than 20µm, thereby revealing the defect.
5. The detection method according to claim 4, characterized in that, The continuous corrosion time of the SECCO corrosion solution is 5 min to 20 min, and the corrosion rate is controlled at 1 µm / min to 1.4 µm / min.
6. The detection method according to claim 1, characterized in that, The step of detecting defects in the silicon wafer under test, and determining that a defect is an NDP defect when its characteristics meet set conditions, further includes: The silicon wafer to be tested, after being thinned again, is placed under a visual inspection device for visual inspection to observe whether there are high-density and symmetrical defect clusters on the surface of the silicon wafer to be tested. When a cluster of defects with a high density and symmetrical pattern appears on the surface of the silicon wafer under test, the distribution, morphology and density of the defects are detected by microscope.
7. The detection method according to claim 1, characterized in that, The diameter of the NDP defect is 5µm to 12µm.
8. A defect detection system for a single-crystal silicon rod, characterized in that, The detection system includes: A cutting device for cutting from the P-band region of a single-crystal silicon rod to prepare a silicon wafer to be tested; An acid etching apparatus is used to perform acid etching on the silicon wafer to be tested to reduce the surface thickness of the silicon wafer to remove the damaged layer on the surface of the silicon wafer. The SECCO etching apparatus is used to etch the thinned silicon wafer under test with SECCO etching solution to expose defects in the silicon wafer under test. The detection device is used to detect defects in the silicon wafer under test. When the characteristics of the defect meet the set conditions, it is determined to be an NDP defect. The detection device is further configured to determine that a defect is an NDP defect when a high-density, symmetrically patterned defect cluster appears on the surface of the silicon wafer under test, and the defect simultaneously meets the following three conditions: The defects are distributed in a disk-like, ring-like, or combination of disk-like and ring-like shapes. The defect is described as a black, circular hole with a metallic luster at the center and no bright spots of any particular shape. The density of the defects is greater than 100ea / cm².
9. The detection system according to claim 8, characterized in that, The detection device includes a visual inspection device and a microscopic inspection device; wherein... The visual inspection device is used to observe whether there are high-density and symmetrical defect clusters on the surface of the silicon wafer under test; The microscopic inspection device is used to detect the distribution, morphology and density of defects when a high-density, symmetrically patterned defect cluster appears on the surface of the silicon wafer under test using a microscope.