Silicon wafer grinding process for preventing edge chipping

Abstract

The application relates to the technical field of semiconductor material production, and in particular relates to a silicon wafer grinding process capable of preventing edge collapse, which comprises the following steps: S1, edge pretreatment: the edge of a pretreated silicon wafer is pre-ground to remove burrs, microcracks and cutting residues on the edge of the silicon wafer, and the edge of the silicon wafer is chamfered and pretreated; S2, stage-by-stage layered wafer grinding: a wafer surface to be ground of the silicon wafer is subjected to three-stage progressive wafer grinding, namely rough grinding, fine grinding and final grinding; during the wafer grinding process, composite wafer grinding liquid is continuously sprayed, the wafer grinding pressure of the edge area is different from that of the center area, and online dust removal treatment is carried out after each wafer grinding; and S3, edge grinding: the edge of the silicon wafer after wafer grinding is precisely ground to trim the micro edge collapse and burrs, so that the edge is smooth and flat, and the grinding mode is circumferential grinding, and the composite wafer grinding liquid is continuously sprayed during the grinding process.

Description

Technical Field

[0001] This invention relates to the field of semiconductor material manufacturing technology, and in particular to a silicon wafer grinding process to prevent edge collapse. Background Technology

[0002] Currently, silicon wafers are generally processed using conventional grinding processes. This process relies on grinding wheels to directly grind the entire silicon wafer. During processing, the silicon wafer edges experience concentrated and uneven stress. This problem is particularly pronounced for large-size, thin silicon wafers, easily leading to defects such as edge collapse and cracking. At the same time, the process tends to result in a thicker damage layer on the silicon wafer surface and poor overall flatness, presenting a dilemma where grinding efficiency and surface quality cannot be simultaneously achieved. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a silicon wafer grinding process that prevents edge collapse.

[0004] This invention provides the following technical solution: A silicon wafer grinding process to prevent edge collapse includes the following steps: S1. Edge pretreatment: The edges of the pretreated silicon wafer are pre-polished to remove burrs, micro-cracks and cutting residues from the silicon wafer edges. At the same time, the edges of the silicon wafer are chamfered. S2. Staged and Layered Grinding: The silicon wafer is subjected to three progressive grinding stages: rough grinding, fine grinding, and final grinding. After final grinding, the surface roughness Ra of the silicon wafer is ≤0.02μm, and the edge collapse is ≤0.001mm. Composite grinding fluid is continuously sprayed during the grinding process. The grinding pressure in the edge area is set differently from that in the center area. Online dust removal is performed after each grinding stage. S3. Edge Grinding: Precisely grind the edges of the silicon wafer after grinding to remove minor edge collapses and burrs, ensuring a smooth and flat edge. The grinding method is circumferential grinding, during which composite grinding fluid is continuously sprayed. After grinding, the edge collapse of the silicon wafer is ≤0.001mm, and the edge roughness Ra is ≤0.03μm.

[0005] In a further embodiment, in step S1, a flexible grinding head is used to pre-polish the edge of the pre-treated silicon wafer. The pressure is controlled at 0.01-0.02 MPa, the grinding speed is 800-1000 r / min, the grinding time is 1-2 min, and the grinding trajectory is a uniform circular motion around the edge of the silicon wafer with a linear speed of 2-3 m / s.

[0006] In a further embodiment, the flexible grinding head is made of polyurethane material, with diamond micro-powder with a particle size of 10-15μm attached to its surface.

[0007] In a further embodiment, in step S1, the chamfer angle of the chamfer pretreatment is 45°±5°, the chamfer width is 0.1-0.2mm, and the chamfer surface roughness Ra≤0.05μm.

[0008] In a further embodiment, in step S2, the thickness of each layer of the layer being removed is controlled to be 0.005-0.01 mm.

[0009] In a further embodiment, in step S2, the grinding disc is dressed once every 100 silicon wafers are processed. The dressing is done with a diamond dressing wheel at a speed of 1000 r / min for 5 min to ensure the flatness of the grinding disc and the uniformity of the abrasive grain distribution, and to control the wear of the grinding disc to ≤0.001 mm / 100 silicon wafers.

[0010] In a further embodiment, in step S2, Coarse grinding stage: Select a diamond abrasive grinding disc with a particle size of 40-60μm. The flatness of the grinding disc should be ≤0.0005mm. The edge of the grinding disc should have an arc-shaped transition structure with a transition radius of 0.1-0.2mm to prevent the edge of the grinding disc from scraping the silicon wafer and causing edge collapse. The grinding pressure in the central area should be controlled at 0.15-0.25MPa, and the grinding pressure in the edge area should be reduced to 0.10-0.15MPa. The grinding speed should be 1200-1500r / min. The contact angle between the grinding disc and the silicon wafer should be 0°±2°. The amount of material removed by grinding should be 70-80% of the total amount of material removed from the silicon wafer. After coarse grinding, the surface roughness Ra of the silicon wafer should be ≤0.2μm, and there should be no obvious edge collapse or cracking. Fine grinding stage: Select diamond abrasive grinding discs with a particle size of 15-25μm, the flatness of the grinding discs ≤0.0003mm, the grinding pressure in the central area is controlled at 0.08-0.12MPa, the grinding pressure in the edge area is reduced to 0.05-0.08MPa, the grinding speed is 1800-2200r / min, the contact angle between the grinding disc and the silicon wafer is 0°±1°, the grinding removal amount is 15-20% of the total removal amount of the silicon wafer, and the surface roughness Ra of the silicon wafer after fine grinding is ≤0.05μm, and the edge collapse amount is ≤0.002mm; Final grinding stage: Select diamond abrasive grinding discs with a particle size of 5-10μm, the flatness of the grinding discs ≤0.0002mm, the grinding pressure in the central area is controlled at 0.03-0.06MPa, the grinding pressure in the edge area is reduced to 0.02-0.03MPa, the grinding speed is 2500-3000r / min, the contact angle between the grinding disc and the silicon wafer is 0°, the grinding removal amount is 5-10% of the total removal amount of the silicon wafer, and the surface roughness Ra of the silicon wafer after final grinding is ≤0.02μm, and the edge collapse amount is ≤0.001mm.

[0011] In a further embodiment, in step S3, a diamond flexible grinding head with a particle size of 3-5 μm is used to precisely grind the edge of the silicon wafer after grinding. The contact angle between the grinding head and the edge of the silicon wafer is 30°-45°, the grinding pressure is 0.01-0.02 MPa and is monitored and adjusted in real time, the grinding speed is 2000-2200 r / min, the grinding time is 30-60 s, and the grinding linear speed is 1.5-2 m / s.

[0012] In a further embodiment, the composite grinding fluid is composed of the following components by mass percentage: 70-80% deionized water, 1-3% diamond micron powder, 5-8% polyethylene glycol, 3-5% triethanolamine, 2-4% borax, 0.5-1% preservative, and 0.3-0.8% anti-collapse agent. The anti-collapse agent is a mixture of silane coupling agent and nano-alumina in a mass ratio of 1:2. The silane coupling agent is KH-550 or KH-560, and the nano-alumina has a particle size of 50-100 nm. This enhances the lubricity, buffering properties, and adhesion of the grinding fluid, reduces the impact force of the grinding disc on the edge of the silicon wafer, and prevents grinding debris from adhering to the edge of the silicon wafer, thus avoiding secondary damage. The preservative is sodium benzoate or potassium sorbate, which can extend the service life of the grinding fluid and prevent it from deteriorating.

[0013] In a further embodiment, the composite polishing fluid spray flow rate is 8-12 L / min, the spray temperature is controlled at 25-30℃, the spraying method is annular multi-nozzle spraying, the distance between the nozzle and the silicon wafer surface is 10-15 mm, and the spraying angle is 45° to ensure that the polishing fluid covers the silicon wafer surface and edges. The spray flow rate in the edge area is 20-30% higher than that in the center area to ensure that the edge area is fully cooled and lubricated.

[0014] The beneficial effects of this invention are: This invention offers unique technical advantages in solving the problem of edge collapse in silicon wafers, while simultaneously considering grinding efficiency, surface quality, and production costs. Specifically, it addresses the core pain point of existing silicon wafer grinding processes—edge collapse—through a four-fold optimization design of "edge pretreatment + differentiated grinding parameters + edge finishing," forming a comprehensive edge quality control system. This system comprehensively suppresses edge collapse and cracking defects from the source, process, and end, strictly controlling the amount of edge collapse to within 0.001mm, reducing the incidence of edge cracking defects by over 99%. Compared to existing processes, edge quality is improved by over 75%, completely solving the industry problem of severe edge collapse during the grinding of large-size, thin silicon wafers, and filling the gap in precise edge quality control in existing processes.

[0015] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0017] This embodiment provides a silicon wafer grinding process to prevent edge collapse, including the following steps: S1. Edge Pre-treatment: A flexible grinding head is used to pre-grind the edges of the pre-treated silicon wafer. The grinding pressure is controlled at 0.01-0.02 MPa, the grinding speed is 800-1000 r / min, and the grinding time is 1-2 min. The grinding trajectory is a uniform circular motion around the edge of the silicon wafer at a linear speed of 2-3 m / s. This removes burrs, microcracks, and cutting residues from the silicon wafer edge. At the same time, the silicon wafer edge is chamfered pre-treated with a chamfer angle of 45°±5°, a chamfer width of 0.1-0.2 mm, and a chamfer surface roughness Ra≤0.05μm to avoid edge stress concentration and reduce the risk of edge collapse during the grinding process. The flexible grinding head is made of polyurethane material, and the surface of the grinding head is coated with diamond micropowder with a particle size of 10-15 μm to avoid damaging the silicon wafer edge during the pre-grinding process. S2. Staged Layered Grinding: A resin-bonded diamond grinding disc is used to perform three progressive grinding stages on the silicon wafer surface to be ground: rough grinding, fine grinding, and final grinding. Each grinding stage adopts a layered grinding method, with the thickness of each layer controlled at 0.005-0.01mm. Online dust removal is performed after each grinding stage, and the grinding parameters for the edge area are set differently from those for the center area. Composite grinding fluid is continuously sprayed during the grinding process to ensure sufficient cooling and lubrication of the silicon wafer surface and edges. During the grinding process, the grinding disc is dressed once every 100 silicon wafers are processed. The dressing is done with a diamond dressing wheel at a speed of 1000 r / min for 5 min to ensure the flatness of the grinding disc and the uniformity of the abrasive grain distribution, and to control the wear of the grinding disc to ≤0.001 mm / 100 silicon wafers. Coarse grinding stage: Select a diamond abrasive grinding disc with a particle size of 40-60μm. The flatness of the grinding disc should be ≤0.0005mm. The edge of the grinding disc should have an arc-shaped transition structure with a transition radius of 0.1-0.2mm to prevent the edge of the grinding disc from scraping the silicon wafer and causing edge collapse. The grinding pressure in the central area should be controlled at 0.15-0.25MPa, and the grinding pressure in the edge area should be reduced to 0.10-0.15MPa. The grinding speed should be 1200-1500r / min. The contact angle between the grinding disc and the silicon wafer should be 0°±2°. The amount of material removed by grinding should be 70-80% of the total amount of material removed from the silicon wafer. After coarse grinding, the surface roughness Ra of the silicon wafer should be ≤0.2μm, and there should be no obvious edge collapse or cracking.

[0018] Fine grinding stage: Select diamond abrasive grinding discs with a particle size of 15-25μm, the flatness of the grinding discs ≤0.0003mm, the grinding pressure in the central area is controlled at 0.08-0.12MPa, the grinding pressure in the edge area is reduced to 0.05-0.08MPa, the grinding speed is 1800-2200r / min, the contact angle between the grinding disc and the silicon wafer is 0°±1°, the grinding removal amount is 15-20% of the total removal amount of the silicon wafer, and the surface roughness Ra of the silicon wafer after fine grinding is ≤0.05μm, and the edge collapse amount is ≤0.002mm; Final grinding stage: Select diamond abrasive grinding discs with a particle size of 5-10μm, the flatness of the grinding discs ≤0.0002mm, the grinding pressure in the central area is controlled at 0.03-0.06MPa, the grinding pressure in the edge area is reduced to 0.02-0.03MPa, the grinding speed is 2500-3000r / min, the contact angle between the grinding disc and the silicon wafer is 0°, the grinding removal amount is 5-10% of the total removal amount of the silicon wafer, and the surface roughness Ra of the silicon wafer after final grinding is ≤0.02μm, and the edge collapse amount is ≤0.001mm.

[0019] S3. Edge Grinding: A diamond flexible grinding head with a particle size of 3-5μm is used to precisely grind the edges of the silicon wafer after grinding. The grinding method is circumferential grinding. The contact angle between the grinding head and the edge (peripheral surface) of the silicon wafer is 30°-45°. The grinding pressure is 0.01-0.02MPa, the grinding speed is 2000-2200r / min, the grinding time is 30-60s, and the grinding linear speed is 1.5-2m / s. During the grinding process, composite grinding fluid is continuously sprayed to avoid local high temperature that could cause edge cracking or collapse. Minor edge collapses and burrs are repaired to ensure a smooth and flat edge. After grinding, the edge collapse of the silicon wafer is ≤0.001mm, and the edge roughness Ra is ≤0.03μm.

[0020] In the staged, layered grinding process, the composite grinding fluid is composed of the following components by mass percentage: 70-80% deionized water, 1-3% diamond micron powder, 5-8% polyethylene glycol, 3-5% triethanolamine, 2-4% borax, 0.5-1% preservative, and 0.3-0.8% anti-collapse agent. The anti-collapse agent is a mixture of silane coupling agent and nano-alumina in a mass ratio of 1:2. The silane coupling agent is KH-550 or KH-560, and the nano-alumina has a particle size of 50-100 nm. This enhances the lubricity, buffering properties, and adhesion of the grinding fluid, reduces the impact force of the grinding disc on the silicon wafer edge, and prevents grinding debris from adhering to the silicon wafer edge, thus avoiding secondary damage. The preservative is sodium benzoate or potassium sorbate, which can extend the service life of the grinding fluid and prevent it from deteriorating. The grinding fluid spray flow rate is 8-12 L / min, the spray temperature is controlled at 25-30℃, and the spray flow rate in the edge area is 20-30% higher than that in the center area to ensure sufficient cooling and lubrication in the edge area. The spraying method is a ring-shaped multi-nozzle spray with 6-8 nozzles evenly distributed around the grinding disk. The distance between the nozzle and the silicon wafer surface is 10-15 mm, and the spray angle is 45° to ensure that the grinding fluid evenly covers the silicon wafer surface and edges.

[0021] The edge grinding utilizes a flexible diamond grinding head. The grinding head surface is electroplated with diamond micropowder, ensuring uniform powder distribution. The grinding head diameter is 5-8mm, and it can be replaced according to the chamfering dimensions of the silicon wafer edge. During the grinding process, the contact pressure between the grinding head and the silicon wafer edge is monitored and adjusted in real time to ensure the pressure remains stable between 0.01-0.02MPa. This prevents excessive pressure from causing edge collapse, and insufficient pressure from failing to correct minute defects.

[0022] In this embodiment, the staged and layered grinding process adopts a three-stage progressive mode of "coarse grinding - fine grinding - final grinding". It accurately matches the abrasive particle size, grinding pressure and grinding speed of different grinding stages, focuses on optimizing the grinding parameters of the edge area, adopts a center-edge differentiated pressure control strategy, and uses a special composite grinding fluid. Simultaneously, two special processes, edge pretreatment and edge finishing, are added to form a full-process edge quality control system of "pretreatment-grinding-finishing", which realizes efficient, low-damage and edge collapse prevention processing of silicon wafers.

[0023] This embodiment can significantly suppress edge collapse and chipping defects during silicon wafer grinding, with the edge collapse amount strictly controlled within 0.001mm, reducing the occurrence rate of edge chipping defects by more than 99%. At the same time, it reduces the thickness of the damaged layer on the silicon wafer surface to below 0.5μm, improves the flatness of the silicon wafer to within 0.001mm, and the surface roughness Ra≤0.02μm, ensuring the processing accuracy of subsequent etching, polishing and other processes. It is suitable for the mass production needs of large-size semiconductor silicon wafers of 150-300mm and thin-size semiconductor silicon wafers of 0.3-0.8mm. Compared with the existing process, the silicon wafer processing yield is improved by more than 15%, which has good industrial application value and promotion prospects.

[0024] The above description is only a specific embodiment of the present invention, but the structural features of the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A silicon wafer grinding process to prevent edge collapse, characterized in that, Includes the following steps: S1. Edge pretreatment: The edges of the pretreated silicon wafer are pre-polished to remove burrs, micro-cracks and cutting residues from the silicon wafer edges. At the same time, the edges of the silicon wafer are chamfered. S2. Staged and layered grinding: The silicon wafer is ground in three progressive stages: rough grinding, fine grinding and final grinding. After final grinding, the surface roughness Ra of the silicon wafer is ≤0.02μm and the edge collapse is ≤0.001mm. Composite grinding fluid is continuously sprayed during the grinding process. The grinding pressure in the edge area is set differently from that in the center area. Online dust removal is performed after each grinding stage. S3. Edge Grinding: Precisely grind the edges of the silicon wafer after grinding to remove minor edge collapses and burrs, ensuring a smooth and flat edge. The grinding method is circumferential grinding, during which composite grinding fluid is continuously sprayed. After grinding, the edge collapse of the silicon wafer is ≤0.001mm, and the edge roughness Ra is ≤0.03μm.

2. The silicon wafer grinding process for preventing edge collapse according to claim 1, characterized in that, In step S1, a flexible grinding head is used to pre-polish the edge of the pre-treated silicon wafer. The pressure is controlled at 0.01-0.02 MPa, the grinding speed is 800-1000 r / min, the grinding time is 1-2 min, and the grinding trajectory is a uniform circular motion around the edge of the silicon wafer with a linear speed of 2-3 m / s.

3. The silicon wafer grinding process for preventing edge collapse according to claim 2, characterized in that, The flexible grinding head is made of polyurethane and has diamond micro powder with a particle size of 10-15μm attached to its surface.

4. The silicon wafer grinding process for preventing edge collapse according to claim 1, characterized in that, In step S1, the chamfer angle of the chamfer pretreatment is 45°±5°, the chamfer width is 0.1-0.2mm, and the chamfer surface roughness Ra≤0.05μm.

5. A silicon wafer grinding process for preventing edge collapse according to claim 4, characterized in that, In step S2, the thickness of each layer of the layer being removed is controlled to be 0.005-0.01 mm.

6. The silicon wafer grinding process for preventing edge collapse according to claim 4, characterized in that, In step S2, the grinding disc is dressed once every 100 silicon wafers are processed. The dressing is done with a diamond dressing wheel at a speed of 1000 r / min for 5 min to ensure the flatness of the grinding disc and the uniformity of the abrasive grain distribution, and to control the wear of the grinding disc to ≤0.001 mm / 100 silicon wafers.

7. The silicon wafer grinding process for preventing edge collapse according to claim 1, characterized in that, In step S2 Coarse grinding stage: Use diamond abrasive grinding discs with a particle size of 40-60μm. The flatness of the grinding discs should be ≤0.0005mm. The edges of the grinding discs should have an arc-shaped transition structure with a transition radius of 0.1-0.2mm to prevent the edges of the grinding discs from scraping the silicon wafer and causing edge collapse. The grinding pressure in the central area should be controlled at 0.15-0.25MPa, and the grinding pressure in the edge area should be reduced to 0.10-0.15MPa. The grinding speed should be 1200-1500r / min. The contact angle between the grinding disc and the silicon wafer should be 0°±2°. The amount of material removed by grinding should be 70-80% of the total amount of material removed from the silicon wafer. After coarse grinding, the surface roughness Ra of the silicon wafer should be ≤0.2μm, and there should be no obvious edge collapse or cracking. Fine grinding stage: Select diamond abrasive grinding discs with a particle size of 15-25μm, the flatness of the grinding discs ≤0.0003mm, the grinding pressure in the central area is controlled at 0.08-0.12MPa, the grinding pressure in the edge area is reduced to 0.05-0.08MPa, the grinding speed is 1800-2200r / min, the contact angle between the grinding disc and the silicon wafer is 0°±1°, the grinding removal amount is 15-20% of the total removal amount of the silicon wafer, and the surface roughness Ra of the silicon wafer after fine grinding is ≤0.05μm, and the edge collapse amount is ≤0.002mm; Final grinding stage: Select diamond abrasive grinding discs with a particle size of 5-10μm, the flatness of the grinding discs ≤0.0002mm, the grinding pressure in the central area is controlled at 0.03-0.06MPa, the grinding pressure in the edge area is reduced to 0.02-0.03MPa, the grinding speed is 2500-3000r / min, the contact angle between the grinding disc and the silicon wafer is 0°, the grinding removal amount is 5-10% of the total removal amount of the silicon wafer, and the surface roughness Ra of the silicon wafer after final grinding is ≤0.02μm, and the edge collapse amount is ≤0.001mm.

8. The silicon wafer grinding process for preventing edge collapse according to claim 1, characterized in that, In step S3, a diamond flexible grinding head with a particle size of 3-5μm is used to precisely grind the edge of the silicon wafer after grinding. The contact angle between the grinding head and the edge of the silicon wafer is 30°-45°, the grinding pressure is 0.01-0.02Mpa and is monitored and adjusted in real time, the grinding speed is 2000-2200r / min, the grinding time is 30-60s, and the grinding linear speed is 1.5-2m / s.

9. A silicon wafer grinding process for preventing edge collapse according to claim 1, characterized in that, The composite grinding fluid is composed of the following components by mass percentage: 70-80% deionized water, 1-3% diamond micron powder, 5-8% polyethylene glycol, 3-5% triethanolamine, 2-4% borax, 0.5-1% preservative, and 0.3-0.8% anti-collapse agent. The anti-collapse agent is a mixture of silane coupling agent and nano-alumina in a mass ratio of 1:

2. The silane coupling agent is KH-550 or KH-560, and the nano-alumina has a particle size of 50-100 nm. This enhances the lubricity, buffering properties, and adhesion of the grinding fluid, reduces the impact of the grinding disc on the edge of the silicon wafer, and prevents grinding debris from adhering to the edge of the silicon wafer, thus avoiding secondary damage. The preservative is sodium benzoate or potassium sorbate, which can extend the service life of the grinding fluid and prevent it from deteriorating.

10. A silicon wafer grinding process for preventing edge collapse according to claim 9, characterized in that, The composite polishing fluid has a spray flow rate of 8-12 L / min, a spray temperature of 25-30℃, and is sprayed using a ring-shaped multi-nozzle system. The distance between the nozzle and the silicon wafer surface is 10-15 mm, and the spray angle is 45° to ensure that the polishing fluid covers the silicon wafer surface and edges. The spray flow rate in the edge area is 20-30% higher than that in the center area to ensure that the edge area is adequately cooled and lubricated.