Relation between Defects on 4H-SiC Epitaxial Surface and Gate Oxide Reliability
Relation between Defects on 4H-SiC Epitaxial Surface and Gate Oxide Reliability
复制标题
4H-SiC外延表面缺陷与栅氧化层可靠性的关系
DOI：
10.4028/www.scientific.net/msf.740-742.745
复制
发表时间：
2013
期刊：
影响因子：
--
通讯作者：
M. Kitabatake
中科院分区：
文献类型：
--
作者：
J. Sameshima;O. Ishiyama;Atsushi Shimozato;K. Tamura;H. Oshima;T. Yamashita;T. Tanaka;N. Sugiyama;H. Sako;J. Senzaki;H. Matsuhata;M. Kitabatake
在没有阶梯聚束的 n 型 4° 离轴 4H-SiC(0001) 晶圆上对 MOS 电容器进行的时间相关介电击穿 (TDDB) 测量显示出威布尔分布图中的特定击穿。通过观察生长的SiC-外延片表面，用共焦显微镜确认了两种外延表面缺陷：梯形和条形缺陷。包括这些缺陷的上游线的MOS电容器的电荷击穿(Qbd)几乎与磨损击穿区域的值相同。另一方面，MOS电容器的栅氧化层击穿发生在下游线路。研究表明，这些缺陷的特定部分会导致氧化物可靠性下降。 MOS结构的横截面TEM图像显示，下游线上MOS电容器的栅氧化层厚度不均匀。此外，对生长态和氧化态SiC外延表面的AFM观察表明，通过氧化工艺，下游线的表面粗糙度比生长态大3-4倍。
Time-dependent dielectric breakdown (TDDB) measurement of MOS capacitors on an n-type 4 ° off-axis 4H-SiC(0001) wafer free from step-bunching showed specific breakdown in the Weibull distribution plots. By observing the as-grown SiC-epi wafer surface, two kinds of epitaxial surface defect, Trapezoid-shape and Bar-shape defects, were confirmed with confocal microscope. Charge to breakdown (Qbd) of MOS capacitors including an upstream line of these defects is almost the same value as that of a Wear-out breakdown region. On the other hand, the gate oxide breakdown of MOS capacitors occurred at a downstream line. It has revealed that specific part of these defects causes degradation of oxide reliability. Cross-sectional TEM images of MOS structure show that gate oxide thickness of MOS capacitor is non-uniform on the downstream line. Moreover, AFM observation of as-grown and oxidized SiC-epitaxial surfaces indicated that surface roughness of downstream line becomes 3-4 times larger than the as-grown one by oxidation process.