Multi-layer superhard material chamfering grinding wheel and preparation method thereof

Abstract

The invention discloses a multi-layer superhard material chamfering grinding wheel and a preparation method thereof, belonging to the technical field of superhard material grinding wheels. The superhard material chamfering grinding wheel has a three-layer structure distributed from the outer circle to the base from the outside to the inside: the grinding layer contains abrasives for grinding substrate wafers; the reinforcement layer is used to form a core skeleton to hold the grinding layer and the buffer layer, and has high flexural strength and tensile strength to prevent large pieces of the grinding layer from breaking and falling off; the buffer layer is used to form a mesh structure to connect the grinding layer and the reinforcement layer in series, and has a certain elasticity, which can reduce the impact of the grinding force during workpiece grinding; the grinding wheel of the invention has a simple structure and is easy to operate; it can perform low-damage processing on semiconductor substrate wafers, reduce the rigidity of the superhard material chamfering grinding wheel and the semiconductor substrate wafer when they are in contact, and has a good processing effect. After processing, the chip size of the damaged layer of the substrate wafer can reach within 0.02 mm.

Description

Technical Field

[0001] The invention belongs to the technical field of superhard material grinding wheels, and particularly relates to a multi-layer superhard material chamfering grinding wheel and a preparation method thereof. Background Art

[0002] Superhard chamfering wheels are primarily used for machining the edges and corners of semiconductor substrate wafers. Concentric arc microgrooves are distributed across the outer circumference of the wheel, with dimensional accuracy required to within 0.01mm. Chamfering semiconductor substrate wafers is a form of profiling, where the abrasive within the arc microgrooves on the wheel's outer circumference micro-cuts the wafer's edges and corners until they perfectly conform to the internal shape of the microgrooves.

[0003] Currently, single-ring grinding wheels with metal, resin, and vitrified bonds are primarily used for chamfering semiconductor wafers. Semiconductor wafer materials such as gallium nitride and single-crystal silicon are generally brittle, making it difficult to balance longevity and grinding quality with existing superhard grinding wheels. If the grinding layer is too strong, the rigidity of the wheel can cause chipping or cracking at the wafer edge. If the wheel's rigidity is reduced, it will struggle to meet the strength requirements of high-speed grinding, leading to large-scale chipping and shedding.

[0004] The existing common solution is to sacrifice wafer yield to meet the grinding wheel strength requirements, but wafers processed using this method are prone to numerous scratches or gouges, leading to wafer loss. A multi-layer nested approach is used to prepare grinding wheel rings in layers. This approach leverages the properties of different materials to absorb the rigid impact of the outer layer through the inner layer, while the inner layer's high-strength structure holds the outer layer in place, achieving the goal of low-damage processing for semiconductor substrate wafers. However, there are no reports on the preparation of such multi-layer nested superhard material chamfered grinding wheels, and further research is needed. Summary of the Invention

[0005] To overcome the problems of the prior art, the present invention provides a multi-layer superhard material chamfering grinding wheel and its preparation method. In this preparation method, the grinding wheel ring portion is constructed from three layers of material. The resulting grinding wheel has a resin mesh structure and a ceramic skeleton structure within. This grinding wheel can be used to machine the edges and corners of semiconductor substrate wafers, achieving minimal damage.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A multi-layer superhard material chamfering grinding wheel, wherein the grinding wheel layers comprise a grinding layer, a reinforcing layer and a buffer layer from the outside to the inside, and the ring width of each layer from the outside to the inside ranges from 3 to 6 mm for the grinding layer, 1 to 2 mm for the reinforcing layer, and 0.3 to 0.6 mm for the buffer layer.

[0008] The grinding layer formula is a conventional composition in this field. For example, the grinding layer can adopt the following formula, which is composed of the following raw materials in parts by weight: 20-30 parts of abrasive, 56-80 parts of metal binder, and 3-7 parts of additives; the additive is one or a mixture of any proportion of sodium chloride, potassium chloride, sodium carbonate, and potassium carbonate; the particle size of the additive is ≤100 μm; the metal binder is composed of the following raw materials in parts by weight: 30-40 parts of copper powder, 25-35 parts of tin powder, and 1-5 parts of aluminum powder; the abrasive is diamond, and the diamond mesh size is 500-1500 mesh.

[0009] Preferably, the reinforcement layer is composed of the following raw materials in parts by weight: 50-60 parts of aluminum oxide, 30-40 parts of copper powder, 4-6 parts of copper oxide, and 4-6 parts of titanium oxide.

[0010] Preferably, the buffer layer is composed of the following raw materials in parts by volume: 80-90 parts of epoxy resin, 5-15 parts of tin powder, and 3-5 parts of silicon carbide.

[0011] Preferably, the particle sizes of the aluminum oxide, copper oxide and titanium oxide are ≤50 μm, the particle size of the epoxy resin is ≤50 μm, the particle size of the copper powder and tin powder is ≤10 μm, and the particle size of the silicon carbide is ≤5 μm.

[0012] A method for preparing the above-mentioned multi-layer superhard material chamfering grinding wheel comprises the following steps:

[0013] 1) Take copper oxide, titanium oxide and aluminum oxide in proportion, add them into a mixing tank, fill with protective gas and seal it, and mix them evenly;

[0014] 2) Sintering the mixed material obtained in step 1) by heating to 1000-1200° C. and keeping the temperature for 8-12 hours to obtain an alumina ceramic material;

[0015] 3) crushing the alumina ceramic material from step 2), adding zirconium oxide balls, and placing the material into a ball mill for ball milling at a speed of 300-350 r / min for 4-8 hours to obtain alumina ceramic powder;

[0016] 4) Passing the alumina ceramic powder obtained in step 3) through a combined sieve to obtain alumina ceramic powder with a particle size in the range of 20 μm to 30 μm;

[0017] 5) adding copper powder to the sieved alumina ceramic powder obtained in step 4), transferring the mixture into a mixing tank, filling it with protective gas, sealing it, and mixing the mixture evenly to obtain a mixture;

[0018] 6) The mixture obtained in step 5) is placed in a mold and pressed into the required size of the reinforcement layer to obtain a cold-pressed blank ring of the reinforcement layer;

[0019] 7) Sintering the blank ring obtained in step 6) under a nitrogen atmosphere, raising the temperature to 900-1100° C. and holding the temperature for 2-4 hours to obtain a reinforced layer sintered ring;

[0020] 8) Epoxy resin, tin powder and silicon carbide are added to a mixing tank, filled with protective gas and sealed, and mixed evenly to obtain a composite mixture, wherein the protective gas is nitrogen;

[0021] 9) Take the grinding layer raw materials, add them into the mixing tank filled with protective gas and seal it to mix evenly;

[0022] 10) The reinforcement layer sintered ring obtained in step 7) is placed in a desired mold, the composite mixture obtained in step 8) is added to the inner side of the reinforcement layer and pressed once, and the grinding layer mixture obtained in step 9) is added to the outer side of the reinforcement layer and pressed to obtain a blank; the grinding wheel is produced according to conventional methods in the art.

[0023] The conventional method for preparing the grinding wheel in the field can refer to the existing technology, such as sintering the blank in step 10), filling it with hydrogen as a protective gas, heating it to 400-500°C at a rate of 100°C / h and keeping it warm for 1-2 hours, and then obtaining the various layers of the grinding wheel after the insulation is completed; bonding the various layers of the grinding wheel to the grinding wheel base to obtain a grinding wheel blank; processing the grinding wheel blank to the required dimensional accuracy as required to prepare a semi-finished grinding wheel; inspecting and dynamically balancing the semi-finished grinding wheel to obtain a multi-layer superhard material chamfering grinding wheel after meeting the accuracy requirements.

[0024] Preferably, the mixing time of step 1), step 5), step 8), and step 9) is 4-8 hours, and the protective gas is nitrogen; in step 3), the mass ratio of zirconia balls to alumina ceramic material is 1:1; the diameters of the zirconia balls are 5 mm, 7 mm, and 10 mm, and the mass ratio of the three diameters of zirconia balls is 1:1:1; the pressing pressure of step 6), step 9), and step 10) is 1000-2500 kg / cm 2 .

[0025] The multi-layer superhard material chamfering grinding wheel is used in the processing of semiconductor substrate wafers for processing the edges and corners of semiconductor substrate wafers.

[0026] The innovations of this invention lie in: 1) Selection and fabrication of the reinforcement layer material: Extensive experiments have revealed that alumina ceramics possess excellent mechanical strength, but their hexagonal close-packed structure makes them difficult to bond tightly with metal / resin materials through sintering. Using titanium oxide as a sintering aid, the copper powder / alumina powder mixture is heated to 1100-1200°C, undergoing liquid-phase sintering of the copper powder and solid-phase sintering of the alumina particles. The liquid copper acts as a barrier to separate the alumina grains. After cooling and pressing, the reinforcement layer is co-sintered with the buffer layer and working layer. The liquid tin in the buffer layer enters the intergranular spaces between the reinforcement layer particles and alloys with the copper encapsulating the alumina ceramic, enhancing the bond strength and achieving a tight bond between the phases, with the alumina ceramic providing structural strength. 2) Selection and fabrication of the buffer layer material: Epoxy resin has good elasticity and fluidity, but resin materials struggle to form a solid bond with metals and ceramics. To leverage its elastic properties, a certain proportion of tin and silicon carbide micropowders are added. During sintering with the reinforcement layer material, the resin forms a liquid phase in the first stage, entering the pores of the intermediate reinforcement layer. In the second stage, tin forms a liquid phase. In the third stage, copper-tin alloying occurs. Under external pressure and capillary forces, the resin liquid, along with some of the copper-tin alloy liquid, reaches the interface between the intermediate reinforcement layer and the outer working layer. In the fourth stage, the outer working layer and the copper-tin alloy phase at the interface sinter together to form a unified whole. This utilizes the properties of the resin material to connect the various layers of the grinding wheel, maximizing the advantages of each material. 3) A multi-layered nested structure of buffer network layer, reinforcement skeleton layer, and grinding working layer. After sintering, the epoxy resin in the inner buffer layer forms a network structure within the gaps between the ceramic particles in the reinforcement layer and the pores of the working layer. The resin network and the copper-tin alloy network intertwine, and silicon carbide micropowder is dispersed within the network for reinforcement. A ring of alumina ceramic skeleton is inserted between the networks, providing structural strength. The resin and alloy networks within the skeleton connect the substrate and the working layer, forming an elastic network throughout the grinding wheel and a ceramic skeleton structure that supports the entire wheel. The resin network of the structure provides elasticity, the alloy network provides bonding force, the ceramic skeleton provides structural strength, the silicon carbide micropowder strengthens the connections, and the working layer provides grinding ability. It has excellent elasticity, mechanical strength and outstanding grinding processing performance.

[0027] Compared with the existing technology, the beneficial effects of the present invention are: 1. The grinding wheel formula and processing technology of the present invention are simple and easy to operate; 2. By establishing a multi-layer mesh skeleton structure, while maintaining efficient processing of semiconductor substrate wafers, the flexural strength and tensile strength of the internal working layer of the grinding wheel are increased, the rigidity of the working layer of the grinding wheel is reduced, and a certain degree of elasticity is provided, which can reduce the impact of grinding forces during workpiece grinding, thereby achieving the goal of efficient and low-damage processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the structure of the grinding wheel in the embodiment;

[0029] Figure 2 Schematic diagram of semiconductor substrate wafer processing, the embodiment and comparative example tests use the same processing method;

[0030] Figure 3 、 Figure 4 Scanning electron microscope photographs of different magnifications of the interface between the reinforcement layer and the buffer layer in Example 1;

[0031] Figure 1 Middle: 1. Grinding layer, 2. Reinforcement layer, 3. Buffer layer, 4. Matrix. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below in conjunction with the embodiments. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The grinding wheel model used in this solution is 1FF1V / 9 D202×T20×H30×X6, where: D represents the diameter of the grinding wheel, T represents the thickness of the grinding layer, H represents the diameter of the inner hole of the grinding wheel, and X represents the width of the grinding layer, and the unit is mm. The particle sizes of aluminum oxide, copper oxide, and titanium oxide are ≤50 μm, with the median particle size of copper oxide powder and titanium oxide powder being 5 μm, and the median particle size of aluminum oxide powder being 10 μm. The particle sizes of copper powder and tin powder are ≤10 μm, with the median particle size of copper powder being 5 μm, and the median particle size of tin powder being 5 μm. The particle size of epoxy resin is ≤50 μm, with the median particle size of epoxy resin being 2 μm. The particle size of silicon carbide is ≤5 μm, with the median particle size of silicon carbide powder being 3.5 μm. The grinding wheel base is made of aluminum alloy.

[0033] Example 1

[0034] A multi-layer superhard material chamfering grinding wheel, such as Figure 1 As shown, from the outside to the inside, it includes a grinding layer 1, a reinforcing layer 2, a buffer layer 3 and a base 4. The ring width of each layer from the outside to the inside is: grinding layer 6mm, reinforcing layer 2mm, buffer layer 0.6mm.

[0035] The formula of the grinding layer adopts the formula of the abrasive layer in Example 9 of CN 108527174A.

[0036] The reinforcement layer is composed of the following raw materials in parts by weight: 50 parts of aluminum oxide, 40 parts of copper powder, 6 parts of copper oxide, and 4 parts of titanium oxide;

[0037] The buffer layer is composed of the following raw materials in parts by volume: 80 parts of epoxy resin, 15 parts of tin powder, and 5 parts of silicon carbide.

[0038] The preparation method of the multi-layer superhard material chamfering grinding wheel comprises the following steps:

[0039] 1) Take copper oxide, titanium oxide and aluminum oxide in proportion, add them into a nitrogen-protected mixing tank and seal and mix for 4 hours;

[0040] 2) sintering the mixed material obtained in step 1) by heating to 1200° C. and keeping the temperature for 8 hours to obtain an alumina ceramic material;

[0041] 3) Crush the alumina ceramic material from step 2), add zirconia balls, and place in a ball mill for ball milling. The mass ratio of zirconia balls to alumina ceramic material is 1:1. The diameters of the zirconia balls are 5 mm, 7 mm, and 10 mm, and the mass ratio of the three diameters is 1:1:1. The milling speed is 350 rpm and the milling time is 4 hours. After ball milling, alumina ceramic powder is obtained.

[0042] 4) Passing the alumina ceramic powder obtained in step 3) through a combined sieve to obtain alumina ceramic powder with a particle size in the range of 20 μm to 30 μm;

[0043] 5) adding copper powder to the sieved alumina ceramic powder obtained in step 4), transferring the mixture into a mixing tank, filling it with nitrogen, sealing it, and mixing for 4 hours to obtain a mixture;

[0044] 6) Place the mixture obtained in step 5) into a mold and press it at a pressure of 1500 kg / cm 2 Pressing to the required size of the reinforcement layer to obtain a cold-pressed blank ring of the reinforcement layer;

[0045] 7) Sintering the blank ring obtained in step 6) under a nitrogen atmosphere, raising the temperature to 1100° C. and holding the temperature for 2 hours to obtain a reinforced layer sintered ring;

[0046] 8) Take epoxy resin powder, tin powder and silicon carbide powder in proportion, add them into a mixing tank, fill it with nitrogen and seal it, and mix them for 4 hours to obtain a composite mixture;

[0047] 9) According to Example 9 in CN 108527174A, the grinding layer raw materials were taken and added to a mixing tank filled with nitrogen, which was sealed and mixed evenly;

[0048] 10) Place the reinforced layer sintered ring obtained in step 7) into the required mold, and add the composite mixture obtained in step 8) inside the reinforced layer. Press at a pressure of 1500kg / cm 2 After a pressing operation, the grinding layer mixture is added to the outside of the reinforcement layer, and the grinding wheel is prepared according to the subsequent method to obtain a multi-layer superhard material chamfering grinding wheel wrapped with a resin-copper-tin alloy network structure and supported by an alumina ceramic skeleton. The scanning electron microscope photo of the interface between the reinforcement layer and the buffer layer is shown in detail. Figure 3 and Figure 4 , Figure 3 、 Figure 4In the figure, A represents metal and resin powders. After sintering, they flow into the gaps between ceramic particles within the reinforcing skeleton layer, forming a network structure where the metal and resin powders adhere and encapsulate the ceramic particles. B represents bulk granular ceramics. After sintering at a lower temperature, they develop interconnected pores, forming a skeleton structure with gaps. This structure is then encapsulated by the resin and metal powders during the subsequent sintering of the buffer network layer. Sintering allows the buffer layer to flow and penetrate the interface between the two layers, achieving a tight bond between the two materials.

[0049] Example 2

[0050] Compared with the preparation method of Example 1, the grinding wheel provided in this embodiment has the following ring widths from the outside to the inside: grinding layer 3mm, reinforcement layer 1mm, buffer layer 0.6mm. Some preparation parameters are adjusted as follows:

[0051] The reinforcement layer is composed of the following raw materials in parts by weight: 60 parts of aluminum oxide, 30 parts of copper powder, 6 parts of copper oxide, and 4 parts of titanium oxide;

[0052] Step 1) Mixing time 8h; Step 2) Holding temperature 1000℃, holding time 12h; Step 3) Ball milling speed 300 r / min, ball milling time 8h; Step 5) Mixing time 8h; Step 7) Holding temperature 900℃, holding time 4h; Step 10) Pressing pressure 1000 kg / cm 2 .

[0053] Example 3

[0054] Compared with the preparation method of Example 1, the grinding wheel provided in this embodiment has the following ring widths from the outside to the inside: grinding layer 3mm, reinforcement layer 1mm, buffer layer 0.3mm. Some preparation parameters are adjusted as follows:

[0055] The buffer layer is composed of the following raw materials in parts by volume: 90 parts of epoxy resin, 7 parts of tin powder, and 3 parts of silicon carbide.

[0056] Step 8) Mixing time is 8 hours; Step 10) Pressing pressure is 2500 kg / cm 2 .

[0057] Comparative Example 1

[0058] The grinding wheel provided in this comparative example omitted the preparation of the buffer layer and the reinforcement layer, and was directly prepared according to the grinding wheel preparation method of Example 9 in CN 108527174A.

[0059] Comparative Example 2

[0060] Compared with Example 1, the grinding wheel provided in this comparative example has the same grinding layer and reinforcing layer as that in Example 1, and the buffer layer is omitted.

[0061] The preparation method was adjusted as follows:

[0062] Cancel step 8). In step 10), cancel the operation of "adding the composite mixture obtained in step 8) into the inner side of the reinforcement layer", and the subsequent steps remain unchanged.

[0063] Comparative Example 3

[0064] Compared with Example 1, the grinding wheel provided in this comparative example does not make any adjustments to the grinding layer and the buffer layer, and steps 1) to 7) of preparing the reinforcement layer are omitted.

[0065] The preparation method is adjusted as follows: steps 1) to 7) of reinforcing layer preparation are cancelled, and in step 10), the reinforcing layer is cancelled and the buffer layer and grinding layer materials are added in sequence. The contents of the other steps remain unchanged.

[0066] Detection method:

[0067] 1) The grinding wheels prepared in Examples 1-3 of the present invention and Comparative Examples 1-3 were respectively mounted on a Tokyo Seimitsu W-GM-4200 chamfering machine to process a 2-inch silicon carbide substrate. Figure 2 As shown, the grinding wheel speed is 2400 rpm, the substrate speed is 1.5 rpm, the grinding feed is 0.1 mm, and pure water is used as the coolant;

[0068] 2) Record the substrate yield and the single groove life of the grinding wheel, that is, the number of substrates processed when the grinding wheel groove shape changes. The results are shown in Table 1:

[0069] Table 1 Test results of superhard material chamfering grinding wheel

[0070]

[0071] Through grinding tests, it was found that the multi-layer superhard material chamfering grinding wheels described in Examples 1-3 of the present invention have good processing effects, the processed silicon carbide substrates have little damage, and the yield rate is high. The grinding wheel prepared in Example 1 has a long service life.

Claims

1. A method for preparing a multi-layer superhard material chamfering grinding wheel, characterized in that: The multi-layer superhard material chamfering grinding wheel includes a base and a grinding wheel layer. The grinding wheel layer includes a grinding layer, a reinforcement layer and a buffer layer from the outside to the inside. The ring width of each layer from the outside to the inside ranges from 3 to 6 mm for the grinding layer, 1 to 2 mm for the reinforcement layer, and 0.3 to 0.6 mm for the buffer layer. The reinforcement layer is composed of the following raw materials in parts by weight: 50-60 parts of aluminum oxide, 30-40 parts of copper powder, 4-6 parts of copper oxide, and 4-6 parts of titanium oxide. The buffer layer is composed of the following raw materials in parts by volume: 80-90 parts of epoxy resin, 5-15 parts of tin powder, and 3-5 parts of silicon carbide. The steps include: 1) Take copper oxide, titanium oxide and aluminum oxide in proportion, add them into a mixing tank, fill with protective gas and seal it, and mix them evenly; 2) Sintering the mixed material obtained in step 1) by heating to 1000-1200° C. and keeping the temperature for 8-12 hours to obtain an alumina ceramic material; 3) crushing the alumina ceramic material from step 2), adding zirconium oxide balls, and placing the material into a ball mill for ball milling at a speed of 300-350 r / min for 4-8 hours to obtain alumina ceramic powder; 4) Passing the alumina ceramic powder obtained in step 3) through a combined sieve to obtain alumina ceramic powder with a particle size in the range of 20 μm to 30 μm; 5) adding copper powder to the sieved alumina ceramic powder obtained in step 4), transferring the mixture into a mixing tank, filling it with protective gas, sealing it, and mixing the mixture evenly to obtain a mixture; 6) The mixture obtained in step 5) is placed in a mold and pressed into the required size of the reinforcement layer to obtain a cold-pressed blank ring of the reinforcement layer; 7) Sintering the blank ring obtained in step 6) under a nitrogen atmosphere, raising the temperature to 900-1100° C. and holding the temperature for 2-4 hours to obtain a reinforced layer sintered ring; 8) Epoxy resin, tin powder and silicon carbide are added to a mixing tank, filled with protective gas and sealed, and mixed evenly to obtain a composite mixture, wherein the protective gas is nitrogen; 9) Take the grinding layer raw materials, add them into the mixing tank filled with protective gas and seal it to mix evenly; 10) The reinforcement layer sintered ring obtained in step 7) is placed in a desired mold, the composite mixture obtained in step 8) is added to the inner side of the reinforcement layer, and pressed once, and the grinding layer mixture obtained in step 9) is added to the outer side of the reinforcement layer, and pressed to obtain a blank; 11) The blank from step 10) is sintered, filled with hydrogen as a protective gas, and heated to 400-500°C and held at that temperature for 1-2 hours. After the holding period, the various layers of the grinding wheel are obtained. The various layers of the grinding wheel are bonded to a grinding wheel base to obtain a grinding wheel blank. The grinding wheel blank is processed to the required dimensional accuracy as required to prepare a semi-finished grinding wheel. The semi-finished grinding wheel is inspected and dynamically balanced. Once the required accuracy is achieved, it becomes a multi-layer superhard material chamfering grinding wheel.

2. The method for preparing a multi-layer superhard material chamfering grinding wheel according to claim 1, wherein: The particle sizes of the aluminum oxide, copper oxide and titanium oxide are ≤50 μm, the particle size of the epoxy resin is ≤50 μm, the particle size of the copper powder and tin powder is ≤10 μm, and the particle size of the silicon carbide is ≤5 μm.

3. The method for preparing a multi-layer superhard material chamfering grinding wheel according to claim 1, wherein: The mixing time of step 1), step 5), step 8), and step 9) is 4-8 hours, and the protective gas is nitrogen.

4. The method for preparing a multi-layer superhard material chamfering grinding wheel according to claim 1, wherein: In step 3), the mass ratio of the zirconia balls to the alumina ceramic material is 1:1; the diameters of the zirconia balls are 5 mm, 7 mm, and 10 mm, and the mass ratio of the three diameters of the zirconia balls is 1:1:

1.

5. The method for preparing a multi-layer superhard material chamfering grinding wheel according to claim 1, characterized in that: Step 6) and step 10) the pressing pressure is 1000-2500kg / cm 2 .

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