Process modulation to prevent structure erosion during gap fill

Abstract

High density plasma chemical vapor deposition and etch back processes fill high aspect ratio gaps without liner erosion or further underlying structure attack. The characteristics of the deposition process are modulated such that the deposition component of the process initially dominates the sputter component of the process. For example, reactive gasses are introduced in a gradient fashion into the HDP reactor and introduction of bias power onto the substrate is delayed and gradually increased or reactor pressure is decreased. In the case of a multi-step etch enhanced gap fill process, the invention may involve gradually modulating deposition and etch components during transitions between process steps. By carefully controlling the transitions between process steps, including the introduction of reactive species into the HDP reactor and the application of source and bias power onto the substrate, structure erosion is prevented.