Capped reflow process to avoid contact autodoping and supress tungsten

Abstract

This invention provides a method of preventing contact autodoping and supressing tungsten silicide peeling during the reflow cycle for a borophosphosilicate glass insulating layer during fabrication of large scale integrated circuits. The invention uses a thin oxide layer to protect the contact areas during the reflow cycle. The thin oxide layer is thin enough to allow satisfactory reflow of the borophosphosilicate glass insulating layer and thick enough to prevent autodoping and tungsten silicide peeling. The thin oxide layer is also thin enough so that process time required to remove the thin oxide layer is not a significant increase in process time. The thin oxide layer thickness is controlled by depositing a helium diluted tetraethoxysilane vapor and oxygen using chemical vapor deposition.