The prevention of charge damage on thin gate oxide from high density plasma deposition

In this paper, thin gate oxide charge damage caused by high-density-plasma (HDP) deposition of inter-metal dielectric (IMD) was studied. In a nonoptimized HDP process, it is easy to generate nonuniform plasma charges. The plasma charges flow along metal lines, contact holes, and poly-gates to damage the gate oxide. This causes degradation of gate oxide quality and MOS device performance. A multiple-step HDP deposition process is demonstrated in this work which prevents plasma damage, by introducing an in-situ low etch-to-deposition (E/D) ratio thin oxide layer before conventional HDP gap-fill. A mechanism of plasma charge induced damage on gate oxide quality due to HDP chemical vapor deposited (CVD) dielectric deposition is proposed.