The Study Of In Situ Etching Process Of 4H-SiC Epitaxial Growth

Silicon carbide(Si C) as a new generation of semiconductor materials, to compare with the traditional semiconductor materials has lots of excellent properties, such as wide band gap, high breakdown electric field, high temperature resistance, resistance to radiation, etc. And it is widespread attention at home and abroad because the device made by Si C can work in some harsh environment. 4H-Si C gets much more attention because of the high electron mobility and low anisotropy in commercial Si C materials. High power 4H- Si C device has a strong competitive power to compare with the traditional semiconductor device. And it can be widely used in many important areas such as aerospace, petroleum and geological exploration, military weapon systems, transportation, etc.Epitaxial film growth is a key to the 4H-Si C device manufacturing process and it has a very important influence to the device quality. By chemical vapor deposition(CVD) can well control many parts of the 4H-Si C epitaxial growth such as the thickness, doping, growth rate, crystal quality, etc. So it is mainly use CVD method to produce the 4H-Si C epitaxial films. In situ etching is an important step before the CVD grown process. Through in situ etching can make Si C substrate has a good surface topography and surface roughness before growth. And it has directly affect to the quality of the epitaxial film on the subsequent growth of 4H-Si C.This article mainly research on to get substrate surfaces which are in favor of the subsequent growth of epitaxial layer by changing the in situ etching conditions. It was found that for 0° substrate, when the etching time is too short(5min), the steps on the substrate surface are too narrow. While when the etching time is too long(15min), the steps on the substrate surface are not uniform and height difference is too large. When etching temperature is too high(1500℃&1600℃), the steps on the substrate surface are too narrow and extremely uneven. So my conclusion is that to get better 0° substrate by using the etching conditions as: 1400℃ etching temperature, 10 min etching time, 100 mbar etching pressure, 20 + 40 l/min flow.For 4°substrate, when the etching time is too short(5min), the substrate surface is too rough because the excess ion on the substrate surface are not been eliminated completely. While when the etching time is too long(15min), the substrate surface is been excessive etching. When etching temperature is 1500℃, the steps on the substrate surface are most uniform and flat. So my conclusion is that to get better 4° substrate by using the etching conditions as: 1500℃ etching temperature, 10 min etching time, 100 mbar etching pressure, 20 + 40 l/min flow. From the further experiments we found that because the evaporation rate of Si atoms is fast, when passes in the propane as protective gas, 4° substrate would get better surface steps. While, neither in carbon-rich environment nor in silicon-rich environment would 4° substrate get better surface steps. So 4° substrate only need to be etched under the condition of pure hydrogen. Further experiments find out that, for 0°substrate when passed the hydrogen and into etching will get better substrate surface; for 4°substrate we just need passed the pure hydrogen into etching. Through this research on in situ etching we can improve the quality of Si C epitaxial layers.