Development of ultra-precision processing technology of novel semiconductor substrate applied to devices with nano-structure

本项目的研究目标是开发应用于未来纳米结构器件的新型半导体衬底（如砷化镓、碳化硅和金刚石单晶）的超精密加工技术。该技术的基本概念是固体催化和紫外线在抛光技术中的应用。所得结果如下：(1) GaAs亚基的超精密抛光。在分散TiO_2光催化剂粉末的GaAs晶片上照射紫外线10分钟。用XPS评价方法检测到由Ga_2O_3和As_2O_3组成的氧化膜。采用去除氧化膜的方法可以安全、高质量地抛光砷化镓。另一方面，H_2O_2生成的羟基自由基也可用于GaAs抛光。(2)碳化硅基板超精密抛光采用cr_2o_3砂轮对SiC单晶端部表面进行高质量、高效率的抛光。其去除率达到3微米/小时，抛光后的表面粗糙度低于Ra 0.3nm。采用CAICISS方法进行评价，发现无亚表面损伤。发现在紫外线照射下，石英盘可以抛光SiC单晶。研究了基于SiC半导体光化学反应的抛光机理。(3)金刚石单晶超精密抛光用石英盘在紫外线照射下对金刚石单晶（100）表面进行抛光。在抛光压力为70 MPa的条件下，去除率达到2微米/小时。抛光后的表面粗糙度在Ra 0.5nm以下。

The research target in this project is to develop the ultra-precision machining technology of novel semiconductor substrates, such as GaAs, silicon carbide and diamond single crystal, applied to future devices with nano-structure. The basic concept of the technology is application of solid catalysis and ultra-violet rays in polishing technology. The results obtained are as follows.(1)Ultra-precision polishing of GaAs substrateUltra-violet rays was irradiated on the GaAs wafer on which TiO_2 photocatalyst powder was dispersed for ten minutes. It is found that oxide film composed from Ga_2O_3 and As_2O_3 was detected by evaluation method of XPS. It is possible to polish GaAs by means of removing the oxide film with safety and high quality. On the other hand, hydroxyl-radical generated from H_2O_2 is also available for GaAs polishing.(2)Ultra-precision polishing of silicon carbide substrateSilicon terminated surface of SiC single crystal is polished with Cr_2O_3-grinding wheel to high quality and high efficiency. The stock removal rate of it achieves to 3 micrometer per hour and the surface roughness polished is below Ra 0.3nm. It was found that there is no sub-surface damage from the evaluation by CAICISS method.It was found that SiC single crystal can be polished with quartz disk under ultra-violet rays irradiation. The polishing mechanism of this based on photochemical reaction of SiC semiconductor.(3)Ultra-precision polishing of diamond single crystalThe (100) surface of diamond single crystal can be polished with quartz disk under ultra-violet rays irradiation. The stock removal rate is achieved to 2 micrometers per hour under the condition of polishing pressure of 70 MPa. The surface roughness of the surface polished is below Ra 0.5nm.