A microporous polycrystalline cubic boron nitride composite material and a method for producing the same

Abstract

The application relates to a microporous structure polycrystalline cubic boron nitride composite material and a preparation method thereof, and relates to the field of composite material preparation.The composite material comprises the following raw materials in percentage by mass: cubic boron nitride powder 50-80%, Ti 10-30%, Al powder 5-15%, and pore-forming agent 1-5%. The application is applied to chemical mechanical polishing technology, and the surface is provided with many empty spherical micropore closed unit structures; the micropores can collect processing removal objects, convey polishing liquid, and ensure chemical corrosion, etc., are favorable for improving polishing uniformity and polishing efficiency, high hardness of the PCBN polishing pad can obtain very high polishing efficiency, the hardness uniformity of the PCBN polishing pad is consistent, wear resistance and heat conductivity are excellent, physical mechanical properties of the material are obviously improved, on the basis of meeting strength and toughness, the PCBN polishing pad has lower endogenous heat and better dynamic performance, and is more suitable for working environments with high dynamic performance requirements such as high speed and high bearing.

Description

Technical Field

[0001] This invention relates to the field of composite material preparation, specifically to a microporous polycrystalline cubic boron nitride composite material and its preparation method. Background Technology

[0002] Chemical Mechanical Polishing (CMP) is widely used in integrated circuit manufacturing to create planar surfaces on semiconductor wafers, and is currently the best process technology for achieving global planarization. CMP combines the advantages of chemical and mechanical polishing, achieving both a near-perfect surface and a high polishing rate. The resulting flatness is two orders of magnitude higher than other methods, making it the only method capable of achieving global planarization. Polishing pads are a crucial component of the CMP system and a major consumable. The surface structure and microstructure of the polishing pad directly affect its performance, thus influencing the CMP process and its final result.

[0003] In existing technologies, polishing pads are generally made of polyurethane, which has both hydrophilic and hydrophobic properties. During the CMP process, the hydrophilic properties of polyurethane cause the polishing pad to combine with water molecules during the polishing process. Under the action of external force, the polishing pad rubs against the abrasive and water molecules, which easily causes wear on the polishing pad. After the polishing pad is worn, the polishing rate will be greatly reduced. In addition, polyurethane polishing pads have disadvantages such as complex manufacturing process, poor dynamic performance, and high internal heat generation, making it difficult to meet the polishing precision requirements of high-precision electronic devices for integrated circuits and wafer surfaces. Summary of the Invention

[0004] Based on the above shortcomings, this invention proposes a microporous polycrystalline cubic boron nitride composite material and its preparation method.

[0005] This invention provides the following technical solution:

[0006] A microporous polycrystalline cubic boron nitride composite material, by mass percentage, comprises the following raw materials: 50%-80% cubic boron nitride powder, 10%-30% Ti, 5%-15% Al powder, and 1%-5% pore-forming agent.

[0007] Preferably, the pore-forming agent is one of ammonium carbonate, ammonium bicarbonate, and urea.

[0008] Preferably, the particle size range of cubic boron nitride powder is 2-10 μm.

[0009] Another technical solution: A method for preparing microporous polycrystalline cubic boron nitride composite materials, the specific steps of which are as follows:

[0010] Step (1): Mix cubic boron nitride powder with Ti and Al powder according to the mass percentages described in claim 1, and add a pore-forming agent at the same time. After uniformly mixing the composite powder, transfer it into a graphite mold.

[0011] Step (2): The sample block was synthesized under high temperature and high pressure using a six-sided top press to obtain a porous polycrystalline cubic boron nitride composite material.

[0012] Preferably, in step (2): the synthesis pressure is 5-7 GPa, the sintering temperature is 1250-1450℃, and the holding time is 30-50 min.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] (1): This invention adds Al and Ti metal materials and pore-forming agents to CBN powder, resulting in a uniformly distributed microporous structure inside the material after sintering. Figure 1 Compared to polyurethane polishing pads, polycrystalline cubic boron nitride polishing pads offer superior wear resistance, thermal conductivity, and excellent thermal stability. The microporous structure within the material allows the polishing pad to maintain surface roughness and porosity for an extended period during polishing, prolonging its service life, reducing the frequency of polishing pad dressing, and improving its overall lifespan. Furthermore, the microporous structure imparts good elasticity to the polishing pad material. Increased elasticity leads to decreased hardness, which, when used for surface planarization of wafers, reduces scratches on the wafer surface and improves its surface performance.

[0015] (2): This invention is applied to chemical mechanical polishing technology. Its surface features a closed-cell structure with numerous hollow spherical micropores. These micropores collect processing waste, transport polishing fluid, and ensure chemical corrosion, thus improving polishing uniformity and efficiency. The high hardness of the PCBN polishing pad allows for high polishing efficiency. The PCBN polishing pad exhibits uniform hardness, excellent wear resistance and thermal conductivity, significantly improving the physical and mechanical properties of the material. While meeting strength and toughness requirements, it also possesses lower internal heat generation and better dynamic performance, making it more suitable for high-speed, high-load, and other dynamic performance-critical working environments. Attached Figure Description

[0016] Figure 1 This invention provides a diagram of the microporous structure of the composite material after sintering.

[0017] Figure 2 XRD pattern of the composite material in Example 1.

[0018] Figure 3 Electron micrograph of the composite material in Example 1. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: 70% cubic boron nitride powder (particle size range 2-5 μm) by mass ratio was mixed with 20% Ti and 5% Al powder, and 5% pore-forming agent (ammonium carbonate) was added at the same time. After uniformly mixing the composite powder, it was transferred into a graphite mold and subjected to high temperature and high pressure synthesis at a synthesis pressure of 5 GPa and a synthesis temperature of 1300℃ to obtain a microporous polycrystalline cubic boron nitride composite material.

[0021] No residual phase of the pore-forming agent ammonium carbonate was detected in the phase composition results, which means that the addition of the pore-forming agent has no effect on the phase structure of the TiAl intermetallic compound porous material, and Figure 2 It can be seen that a relatively large amount of Al3Ti intermetallic compounds are produced. Figure 3 It can be seen that the micropores in the composite material structure are relatively uniformly distributed, and there are many closed-pore structures within the particles.

[0022] A 2-inch diameter silicon wafer was polished using a microporous polycrystalline cubic boron nitride composite polishing pad prepared in Example 1 on a ZYP200 polishing machine. Before polishing, the surface roughness Ra of the silicon wafer was 60 nm. The polishing pressure was 4 psi, the polishing pad rotation speed was 80 r / min, the workpiece rotation speed was 60 r / min, and the polishing time was 10 min. After polishing, the surface roughness of the silicon wafer became 21 nm. It is evident that the microporous polycrystalline cubic boron nitride composite polishing pad prepared in Example 1 exhibits high polishing efficiency and good polishing quality.

[0023] Example 2: 50% cubic boron nitride powder (particle size range 4-8 μm) by mass ratio was mixed with 10% Ti and 10% Al powder, and 3% pore-forming agent (ammonium carbonate) was added at the same time. The composite powder was uniformly mixed and then transferred into a graphite mold for high-temperature and high-pressure synthesis. The synthesis pressure was 6 GPa and the synthesis temperature was 1250℃ to obtain a microporous polycrystalline cubic boron nitride composite material.

[0024] A 2-inch diameter silicon wafer was polished using a microporous polycrystalline cubic boron nitride composite polishing pad prepared in Example 2 on a ZYP200 polishing machine. Before polishing, the surface roughness Ra of the silicon wafer was 60 nm. The polishing pressure was 4 psi, the polishing pad rotation speed was 80 r / min, the workpiece rotation speed was 60 r / min, and the polishing time was 10 min. After polishing, the surface roughness of the silicon wafer became 18 nm. It is evident that the microporous polycrystalline cubic boron nitride composite polishing pad prepared in Example 2 exhibits high polishing efficiency and good polishing quality.

[0025] Example 3: 60% by mass of cubic boron nitride powder (particle size range 6-10 μm) was mixed with 25% Ti and 15% Al powder, and 4% of pore-forming agent (ammonium carbonate) was added. The composite powder was uniformly mixed and then transferred into a graphite mold for high-temperature and high-pressure synthesis at a synthesis pressure of 7 GPa and a synthesis temperature of 1350℃ to obtain a microporous polycrystalline cubic boron nitride composite material.

[0026] A 2-inch diameter silicon wafer was polished using a polycrystalline cubic boron nitride composite polishing pad with the microporous structure prepared in Example 3 on a ZYP200 polishing machine. Before polishing, the surface roughness Ra of the silicon wafer was 60 nm. The polishing pressure was 4 psi, the polishing pad rotation speed was 80 r / min, the workpiece rotation speed was 60 r / min, and the polishing time was 10 min. After polishing, the surface roughness of the silicon wafer became 25 nm. It is evident that the microporous polycrystalline cubic boron nitride composite polishing pad prepared in Example 3 exhibits high polishing efficiency and good polishing quality.

[0027] Example 4: 80% cubic boron nitride powder (particle size range 3-7 μm) by mass ratio was mixed with 30% Ti and 8% Al powder, and 1% pore-forming agent (ammonium carbonate) was added at the same time. The composite powder was uniformly mixed and then transferred into a graphite mold for high-temperature and high-pressure synthesis at a synthesis pressure of 5.5 GPa and a synthesis temperature of 1450℃ to obtain a microporous polycrystalline cubic boron nitride composite material.

[0028] A 2-inch diameter silicon wafer was polished using a microporous polycrystalline cubic boron nitride composite polishing pad prepared in Example 4 on a ZYP200 polishing machine. Before polishing, the surface roughness Ra of the silicon wafer was 60 nm. The polishing pressure was 4 psi, the polishing pad rotation speed was 80 r / min, the workpiece rotation speed was 60 r / min, and the polishing time was 10 min. After polishing, the surface roughness of the silicon wafer became 20 nm. It is evident that the microporous polycrystalline cubic boron nitride composite polishing pad prepared in Example 4 exhibits high polishing efficiency and good polishing quality.

[0029] Comparative Example 1

[0030] A 2-inch diameter silicon wafer was polished using a domestically produced polyurethane polishing pad on a ZYP200 polishing machine. Before polishing, the surface roughness Ra of the silicon wafer was 60 nm. The polishing pressure was 4 psi, the polishing pad rotation speed was 80 r / min, the workpiece rotation speed was 60 r / min, and the polishing time was 10 min. After polishing, the surface roughness of the silicon wafer became 42 nm.

[0031] Abrasion resistance tests were conducted on Examples 1-4.

[0032] The microporous polycrystalline cubic boron nitride composite materials prepared in Examples 1-4 were respectively made into standard cutting tools CNMN120716S05020. Then, the wear ratio was tested according to the current national industry standard (JB3235-83). The wear ratio was measured using a standard grinding wheel TL80#Z2AP100×16×20 on a JS71-A type wear ratio tester. The grinding wheel linear speed was 25m / s, the grinding wheel wear was not less than 25g, and the sample wear was not less than 0.2mg.

[0033] Table 1. Test results of the wear ratio of cutting tools

[0034] Knife raw materials Example 1 Example 2 Example 3 Example 4 Wear ratio 14860 13500 12930 13390

[0035] Thermal conductivity tests were conducted on Examples 1-4.

[0036] This test example tested the thermal conductivity of the composite materials in Examples 1-4. The test conditions were as follows: the thermal conductivity of the composite materials was tested using a laser thermal conductivity meter (Netzsch LFA457), the heating rate was 10K / min, and the temperature was increased from room temperature to 800℃.

[0037] The thermal conductivity of the composite material obtained in Example 1 is 190 W / (K·M).

[0038] The thermal conductivity of the composite material obtained in Example 2 is 220 W / (K·M).

[0039] The thermal conductivity of the composite material obtained in Example 3 is 230 W / (K·M).

[0040] The thermal conductivity of the composite material obtained in Example 4 is 205 W / (K·M).

[0041] The thermal conductivity of polyurethane polishing pads used in existing CMP processes is 0.018-0.024 W / (K·M).

[0042] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A microporous polycrystalline cubic boron nitride composite material, characterized in that, By mass percentage, it includes the following raw materials: 50%-80% cubic boron nitride powder, 10%-30% Ti, 5%-15% Al powder, and 1%-5% pore-forming agent; The pore-forming agent is one of ammonium carbonate, ammonium bicarbonate, and urea. The preparation method of microporous polycrystalline cubic boron nitride composite material, the specific steps are as follows: Step (1): Mix cubic boron nitride powder with Ti and Al powder according to the above mass percentage, and add a pore-forming agent at the same time. After the composite powder is evenly mixed, transfer it into a graphite mold. Step (2): The sample block was synthesized under high temperature and high pressure using a six-sided top press to obtain a porous polycrystalline cubic boron nitride composite material.

2. The microporous polycrystalline cubic boron nitride composite material according to claim 1, characterized in that, The particle size range of the cubic boron nitride powder is 2-10 μm.

3. The microporous polycrystalline cubic boron nitride composite material according to claim 1, characterized in that, In step (2): the synthesis pressure is 5-7 GPa, the sintering temperature is 1250-1450℃, and the holding time is 30-50 min.

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