Implications of Surface Contaminants in a BPSG Deposition and Reflow Process

Abstract

Chemically vapor deposited borophosphosilicate glass (BPSG) has been widely used in microelectronic device fabrication as interlayer dielectric film due to its excellent planarization, gettering and flow properties. A BPSG reflow step, performed either in a diffusion furnace or a RTP reactor, normally follows the deposition step. With device geometry reducing to sub micron levels, there is an increasingly greater emphasis on detection and elimination of surface contaminants and sub micron defects particularly on deposited film. In this paper, we report on the implications of surface contaminants in a BPSG deposition/reflow process. The deposition and reflow processes have been carried out in an atmospheric-pressure CVD system and a vertical diffusion furnace respectively. Ellipsometric measurements, SIMS, TXRF, and vapor phase dissolution (VPD) methods have been used to detect both metallic and non-metallic contaminants as a function of both BPSG deposition and furnace reflow process parameters. It was found that surface contaminants emanating under specific deposition conditions can cause an uncontrolled, enhanced oxidation during the reflow process. Process modifications and in line defect monitoring schemes are discussed.