高温氧化对SiC MOS器件栅氧可靠性的影响

SiC金属氧化物半导体(MOS)器件中SiO2栅氧化层的可靠性直接影响器件的功能.为了开发高可靠性的栅氧化层,将n型4H-SiC (0001)外延片分别在1 200,1 250,1 350,1 450和1 550℃5种温度下进行高温干氧氧化实验来制备SiO2栅氧化层.在室温下,对SiC MOS电容样品的栅氧化层进行零时击穿(TZDB)和与时间有关的击穿(TDDB)测试,并对不同干氧氧化温度处理下的栅氧化层样品分别进行了可靠性分析.结果发现,在1 250℃下进行高温干氧氧化时所得的击穿场强和击穿电荷最大,分别为11.21 MV/cm和5.5×10-4 C/cm2,势垒高度(2.43 eV)最接近理论值.当温度高于1 250℃时生成的SiO2栅氧化层的可靠性随之降低.

Effect of High Temperature Oxidation on the Gate Oxide Reliability of SiC MOS Devices

The performance of SiC metal oxide semiconductor (MOS) devices is directly affected by the reliability of the SiO2 gate oxide layer.In order to develop the high-reliability gate-oxide layer,the ntype 4H-SiC (0001) epitaxial wafers were subjected to high temperature dry oxygen oxidation experiments at 1 200,1 250,1 350,1 450 and 1 550 ℃,respectively,to prepare the SiO2 gate oxide layer.The time-zero dielectric breakdown (TZDB) and time-dependent dielectric breakdown (TDDB) tests were performed on the gate oxide layer of SiC MOS capacitor samples at room temperature.And the reliability of the gate oxide layer samples under different dry oxidation temperatures was also analyzed.The results show that the values of the breakdown field strength and the breakdown charge reach the maximum at the oxidation temperature of 1 250 ℃,which are 11.21 MV/cm and 5.5× 10-4 C/cm2,respectively,and the value of the barrier height (2.43 eV) is closest to the theoretical one.The reliability of the SiO2 gate oxide layer degrades as the oxidation temperature exceeds 1 250 ℃.