STI fill effect on poly-poly comb IL

Increasing ETD ratio for HDP oxide from 0.10 to 0.16 resulted in increasing film stress; film became more compressive. An increase in HF RF setting typically causes an increase in sputtering that may cause additional process induced damage or defects resulting in poorer oxide film quality, but the oxide wet etch rate ratio remain similar with increase in ETD which indicated no change in oxide quality. However, increasing etch to deposition ratio of HDP CVD film was demonstrated to improve gap fill of STI as indicated by a reduction in poly-poly comb shorts.