Screening of Si-H bonds during plasma processing

CMOS devices are subjected to high-field electron injection during plasma processing [1]. This work investigates the screening of Si-H bonds during high field stress degradation in an n-channel MOSFET. To emulate the plasma processing conditions, devices were subjected to current stress (both gate injection and substrate injection) and the source and drain terminals were reverse biased by a screening potential. The screening potentials can be generated at the source and drain terminals during plasma processing due to effective antennas, connected to these terminals [2]. Subsequent hot carrier stress was carried out to evaluate the screening effect [3]. Interface state density D_it was measured before and after the high field injection using charge-pumping technique [4]. The Si-H bond concentration is directly related to interface state density (D_it) and we estimated the Si-H bond concentration using a model [5]-[6] based on a simple first order kinetic equation. Si-H concentration is a function of this screening potential and it was compared with that of the interface state densities (D_it). Activation energy of 2 eV that dissociates hydrogen from the interface was used in our calculation. It was observed that screening of the drain edges was effective for both gate injection and substrate injection at specific screening potentials. The screening potential is found to be in the order of 1.5 V to 2 V for gate injection and 1 to 1.5 V for substrate injection as seen in figure I and 2 [3] for three types of antenna ratios used.