超薄栅氧化层n-MOSFET软击穿后的导电机制

Conduction mechanism of ultra-thin gate oxide n-MOSFET after soft breakdown

研究了恒压应力下超薄栅氧化层n型金属-氧化物-半导体场效应晶体管(n-MOSFET)软击穿后的导电机制.发现在一定的栅电压Vg范围内,软击穿后的栅电流Ig符合Fowler-Nordheim隧穿公式,但室温下隧穿势垒b的平均值仅为0·936eV,远小于Si/SiO2界面的势垒高度3·15eV.研究表明,软击穿后,处于Si/SiO2界面量子化能级上的电子不隧穿到氧化层的导带,而是隧穿到氧化层内的缺陷带上.b与缺陷带能级和电子所处的量子能级相关;高温下,激发态电子对隧穿电流贡献的增大导致b逐渐降低.

The conduction mechanism of ultra-thin gate oxide n-metal-oxide-semiconductor field effect transistor (n-MOSFET) after soft breakdown is studied in this paper. It is found that in a certain range of gate voltage V-g, the gate current I-g follows the Fowler-Nordheim-like tunneling mechanism, and the experimental tunneling barrier phi(b) is 0.936 eV in average, which is much smaller than the interface barrier of Si/SiO2. We think that after soft breakdown, the electrons existing in the quantization energy levels of the Si/SiO2 interface, not directly tunnel to the oxide conduction band, but tunnel to the oxide defect band. phi(b) is determined by both the defect band energy level and the quantization energy level of the tunneling electrons. With rising experimental temperature, the tunneling of high energy level electron is also increasing, which reduces phi(b) gradually.