Effects of processing pressure on device damage in RF biased ECR CVD

Charging effects were investigated in an electron cyclotron resonance (ECR) plasma-enhanced CVD system using a variety of techniques including CHARM-2 wafers (Lukaszek et al, 1994), SPORT wafers (Roche and McVittie, 1996) and full device antenna structures. In this work, we show two factors affecting the potential at the wafer surface which can be correlated to conditions where severe plasma damage is expected to occur. The CHARM-2 wafer data detected both the time-averaged (DC) and time-varying (AC) potentials. The DC component is shown to be a function of the applied wafer bias power while the AC component appears to be related to a low frequency potential fluctuation (a possible instability in the microwave generated magnetized plasma). Both of these signals can be reduced by increasing the processing pressure. Processes with higher pressure result in improved device damage immunity