Screening of Si-H bonds during plasma processing

This work investigates the screening of Si-H bonds at the Si-SiO ₂ interface in an n-channel MOSFET due to plasma charging damage. Since CMOS devices are subjected to high field electron injection during plasma processing, this condition was emulated by subjecting the devices to current stress (both gate injection and substrate injection). With the source and drain terminals reverse biased by a screening potential during stress, representing the impact from source and drain antenna, a decrease in stress-induced interface state density formation was noticed. Observed interface state density D _it before and after the high field injection, therefore, demonstrates an effective screening of the source and the drain edges. During gate injection the Si-H bond concentration, estimated using a model based on a simple first order kinetic equation, is inversely proportional to measured D_it at effective screening potentials. In substrate injection, however, the Si-H concentration does not relate to D_it creation. Similar trends were observed for transistors with different antenna ratios. Subsequent hot carrier stress confirms that the screening is mainly due to protected drain edges. These results suggest that effective screening of Si-H bonds is possible during plasma processing.