SiC MOSFET栅极漏电流传输机制研究

Research on the Gate Leakage Current Transport Mechanisms of SiC MOSFET

通过拟合变温电流-电压试验数据,研究了SiCMOSFET的正向和反向栅极漏电流传输机制。1)正向和反向高偏压下的栅电流由FN(Fowler-Nordheim)隧穿机制主导,得到SiC/SiO_(2)界面的电子势垒高度范围分别为2.58~2.69eV和3.02~3.26eV。2)正向高偏压下,栅电流随温度的升高而逐渐增大的原因可解释为,当温度升高时原子围绕其平衡点做随机运动,即鞍点的高度开始波动,由于FN隧穿模型中电流密度和势垒高度的指数关系,势垒高度降低时电流密度的增加趋势远大于势垒高度升高时电流密度的减少趋势,因此随着温度升高,栅电流逐渐增大,平均势垒高度降低。3)反向高偏压下,由于碰撞电离产生了大量的电子-空穴对,注入到结型场效应晶体管(JFET)区栅极氧化物中的空穴浓度增大,势垒高度进一步降低,因此反向高偏压下势垒高度随温度升高下降的速度更快。

The forward and reverse gate leakage current transport mechanisms of SiC MOSFET have been investigated by fitting the temperature dependent current-voltage experimental data.1)The gate currents under high forward and reverse bias are dominated by FN(Fowler-Nordheim)tunneling mechanism,and the electron barrier heights of SiC/SiO_(2)interface are 2.58-2.69 eV and 3.02-3.26 eV,respectively.2)Under high forward bias,the gate current increases with temperature.This behavior is explained as following:with increasing temperature,the atoms move randomly around their equilibrium points,that is,the height of the saddle point begins to fluctuate.Due to the exponential relationship between the current density and the barrier height in the FN transport model,the increase trend of the current density when the barrier height decreases is much higher than the decrease of it when the barrier height increases.So as the temperature increases,the gate current increases gradually,and the average barrier height decreases.3)Under high reverse bias,owing to the large number of electron-hole pairs generated by impact ionization,the concentration of holes injected into the gate oxide of JFET region increases,and the barrier height decreases further.Therefore,the barrier height decreases more rapidly with increasing temperature under high reverse bias.