High Voltage SiC Power Transistor having High Quality Gate Insulator Formed by Microwave Excited Plasma

通过微波激发高密度等离子体形成的SiO_2薄膜中的碳原子去除，在低于1000[℃]的工艺温度下获得了高质量的栅氧化层。微波激发的高密度等离子体能产生O^* 自由基，从而在低温（<500[℃]）条件下在Si（100）、（110）、（111）等表面上形成固定电荷密度低、界面陷阱密度小的高质量SiO_2薄膜和多晶Si。然而，仅在400[℃]下的O^* 氧化不能形成高质量的氧化物，其含有10^<19>[atmos/cm ^3]的许多碳原子和10^ [cm^ ]的高固定电荷密度<12><-2>。经1000 ℃ N_2退火后，碳含量和固定电荷密度可降低一个数量级。采用双簇射板结构的微波激励高密度等离子体系统，在CVD沉积SiO_2后，可以得到所需厚度的高SiO_2薄膜。另一方面，在400[℃]下，CVD多晶硅和随后的O^* 氧化相结合可以在SiC表面形成高质量的SiO_2薄膜。与在SiC表面直接氧化的SiO_2膜相比，该方法中SiO_2膜中的界面陷阱和固定电荷密度也降低了一个数量级。结果表明，在低于1000[℃]的低温下，可以在SiC表面形成高质量的SiO_2薄膜，采用射频-直流耦合溅射系统，在400[℃]下在Si（100）表面沉积SiC薄膜，在950[℃]下进行N_2退火，可以得到SiC（111）晶相这表明SiC晶体可以在低于1000[℃]的工艺温度下形成。

High quality gate oxides are realized in the process temperature less than 1000[℃] by removal of carbon atoms from SiO_2 films formed by microwave excited high-density plasma. The microwave excited high-density plasma can generate the O^* radical, as a result, it can form the high quality SiO_2 films which have low fixed charge density and low int ire trap density on every Si surface such as (100), (110), (111), and polycrystalline Si at low temperature (<500[℃]). However, only O^* oxidation at 400[℃] cannot form the high quality oxides, which contain many carbon atoms of 10^<19> [atmos/cm^3] and high fixed charge density of 10^<12>[cm^<-2>]. The carbon content and the fixed charge density can be reduced one order of magnitude by N_2 annealing at 1000[℃]. The high SiO_2 films of desired film thickness can be formed by following CVD SiO_2 deposition using the dual shower plate structure microwave excited high-density plasma system. On the other hand combination of CVD Poly-Si and following O^* oxidation can form the high quality SiO_2 films on SiC surface at 400[℃]. In this method, the interface trap and fixed charge densities in the SiO_2 film can also reduced one order of magnitude compared with SiO_2 films directly oxidized by O^* oxidation on SiC surface. These indicate that the high quality SiO_2 films can be formed on SiC surface at low temperature less than 1000[℃].SiC films are deposited on Si(100) surface at 400[℃] using by RF-DC coupled sputter system The crystal of SiC(111) are appeared by N_2 annealing at 950[℃] after the deposition This suggests that the SIC crystal can be formed at the process temperature less than 1000[℃].