A comparison of cl₂and hbr/cl₂-based polysilicon etch chemistries: Impact on sio₂and si substrate damage

The damage produced in thin SiO₂/Si structures after plasma exposure in Cl₂-based or HBr/Cl₂-based reactive ion etching environments is examined. The etch chemistries and parameters used were those of a poly-Si gate overetch. In this study, the damage present in the SiO₂and Si substrate after these etch exposures and that remaining after a 900°C 1 hour Ar anneal is examined for both etch chemistries. Oxide reliability is shown to be affected even by the more benign etch, even after the annealing. On the other hand, Si substrate defects are annealed out to low levels after a 700°C 1 hour anneal for both chemistries. These defects are, however, present in numbers that are large enough to affect generation lifetimes either immediately after etch or at intermediate annealing temperatures.