Akihiro Ikeda*, Hidenori Nagashima, Kazuyuki Kouno, Noriaki Yoshikawa, Keiichi Tshukamoto and Yukinori Kuroki

Graduate School of Information Science and Electrical Engineering
Kyushu University, Fukuoka, 812-8581, Japan
a_ikeda@ed.kyushu-u.ac.jp

Hydrogen plasma is interested for cleaning of high aspect ratio structure on semi-conductor surface at low temperature. We investigate the influence on the electrical characteristics of MOS capacitor exposed to Inductively Coupled hydrogen Plasma (ICP). Hydrogen plasma exposure and sequential 400 C annealing in N2 reduces interface state density at Si/SiO2. Hydrogen atom can terminate the dangling bond at Si/SiO2 interface and electrically passivate the defect. On the other hand, hydrogen plasma exposure causes the degradation of the gate oxide for electron current injection. For the sample exposed to hydrogen plasma, the time for 50% cumulative failure is 0.2 sec at stress voltage of 11MV/cm. This value is about one thousand times smaller than the time for the sample without hydrogen plasma exposure. It is found that more electron traps are appeared with electron injection for the sample exposed to hydrogen plasma comparison with the sample without hydrogen plasma exposure. Hydrogen plasma generates many defects in oxide lattice structure, also passivates the defects such as dangling bond and makes many Si-OH and Si-H groups in oxide. However, this hydrogen in the oxide might be easily depassivated by non elastic collision to hot electron and generates electron traps. Thus, hydrogen plasma exposure is effective for the improvement of the electrical characteristics at Si/SiO2 interface, but causes the degradation of the oxide for electron injection. In this paper, XPS chemical analysis of the oxide and relation between plasma parameter and electrical characteristics of MOS capacitor are also discussed.