大尺寸单晶金刚石磨抛一体化加工研究

金刚石因其优异的物理性质被视为下一代半导体材料,然而其极高的硬度、脆性和耐腐蚀性导致其加工困难,尤其是对于大尺寸的化学气相沉积(chemical vapor deposition, CVD)单晶金刚石(SCD)晶片而言,目前还缺乏一种高效、低成本的磨抛加工方法。本文提出一种基于工件自旋转的同心双砂轮磨抛一体化加工技术,在一次装夹中,先采用金刚石磨料的陶瓷内圈砂轮磨削单晶金刚石晶片表面,将单晶金刚石表面迅速平坦化,后采用金刚石与CuO混合磨料的外圈溶胶-凝胶(sol-gel,SG)抛光轮抛光单晶金刚石晶片表面,使其在较短时间内完成从原始生长面(Sa约46 nm)到原子级表面精度(Sa＜0.3 nm)的加工。磨削加工中,硬质金刚石磨料的陶瓷砂轮高速划擦金刚石晶片表面,在强机械作用下获得较大的材料去除以及纳米级的光滑单晶金刚石表面,同时引起进一步的表面非晶化;SG抛光加工中,硬质金刚石磨料高速划擦单晶金刚石表面形成高温高压环境,进一步诱导CuO粉末与单晶金刚石表面的非晶碳发生氧化还原反应,实现反应抛光。磨抛一体化的加工技术为晶圆级的单晶、多晶金刚石的工业化生产提供借鉴。

Integrated Processing of Grinding and Polishing for Large-Size Single Crystal Diamond

Due to its excellent physical properties, diamond is regarded as a next-generation semiconductor material. However, its extremely high hardness, brittleness, and corrosion resistance cause the diamond difficult to process, especially for large-size chemical vapor deposition (CVD) single crystal diamonds (SCD). Currently, researchers have not explored an efficient and low-cost method for ultra-precision processing diamond wafers. Based on the rotary infeed surface grinding, integrated processing technology of grinding and polishing by the concentric double grinding wheel was proposed in this paper. In one clamping, the SCD surface is flattened by the inner ring ceramic grinding wheel that the abrasive is diamond, and then the surface after grinding is polished by sol-gel (SG) polishing wheel that the abrasives are diamond mixed with CuO. In the processing of grinding and polishing integration, the surface roughness of SCD can be reduced from about 46 nm to less than 0.3 nm in a short time. In the grinding, the ceramic grinding wheel with diamond abrasive scratches the SCD surface at high speed. The strong mechanical action causes the large material removal, obtains nano-level smooth surface of SCD, and causes the surface amorphization. In the SG polishing, the diamond abrasive scratches the SCD surface at high speed to form a high-temperature and high-pressure environment, which further induces the oxidation-reduction reaction between the CuO powder and the amorphous carbon for realizing reactive polishing. The integrated processing technology of grinding and polishing provides a reference for the industrial production of SCD wafers and polycrystalline diamond (PCD) wafers in the future.