Improved PECVD pre-metal oxide liner deposition process with low residual charge non-uniformity in film to avoid excessive PID

Abstract

Current plasma enhanced chemically vapor deposited pre-metal dielectrics (PECVD PMD) such as tetraethylorthosilicate (TEOS) oxide, tend to accommodate a high residual charge non-uniformity. This circumstance can readily instigate degradation to gate oxide integrity and quality by means of plasma induced damage (PID), and the PID effects are even worse when the TEOS oxide is employed as a liner coating the transistor rows. In addition, the oxide conformance to the underlying feature(s) is also found to be less than satisfactory approx. 30% and voids were observed in between conducting lines and at corners of features. This work, nevertheless, reports briefly on an improved PECVD TEOS oxide deposition process that is capable to deposit oxides with appreciable step coverage of > 50% and zero residual charge non-uniformity. The optimized process derives after a comprehensive study of the intricate relationship among several process parameters, namely the gas pressure, the power density, the oxygen/TEOS mole ratio and the gas flow value.