Effect Of The Ion Implantation On 4H-SiC MOS Interface

Due to the excellent performance under high temperature, high frequency, high power and high radiation condition, SiC is considered as a potential"third generation"material. And it is also the only chemical compound, which can grow natural oxide dielectric. But, because of intrinsic characteristic and lagging process technology, the interface states density of SiO2/SiC is far higher than SiO2/Si MOSFET's. This is main cause of the low channel mobility and high 1/f noise. In this thesis, the major work is to reduce the interface states density of SiO2/SiC by optimizing the MOS technology focusing on SiC MOS capacitance.The MOS process is firstly investigated based on current condition. Three different MOS capacitances are fabricated based on the principle of validity and simplicity. These include first sample by wet oxidation and annealing in N2 atmosphere, sencond sample by ion implantation with nitrogen, wet oxidation and annealing in N2 atmosphere, and third sample by ion implantation with nitrogen/aluminium, wet oxidation and annealing in N2 atmosphere.The C-V and I-V characteristics of the SiC MOS capacitor fabricated above are also measured and also analysed. Interface stataes density of all the samples is obtained by Quasi-Static C-V method. The results show that the pre-implanted with nitrogen prior to wet oxidation could effectively reduce the interface states density of SiO2/SiC to the number magnitude of 1011cm-2eV-1. Large negative charges introduced by wet oxidation also could compensate the positive charge infused by N+-ions, which reduce the flatband voltage. The density of oxide trapped charges is also calculated by high frecquency C-V with hysteresis. The outcomes demonstrate that Al+ implantation prior to oxidation could slightly raised interface states density, but could effectually reduce the oxide trapped charges density. Finally, I-V characteristics of all the samples are also discussed. Ion implantation will worsen the compactness of SiO2 and decrease breakdown characteristics of the samples.