Deposition, characterization, reflow and analysis of undoped and boron trioxide/phosphorus pentoxide-doped germanosilicate glass films

Plasma Enhanced Chemical Vapor Deposition (PECVD) of undoped mixed GeO 2-SiO2 glass films in a horizontal tube reactor using germane, silane and oxygen has been studied. Doped films of the mixed GeO2-SiO 2 glass using diborane and phosphine have been studied as well. The glass films offer the potential for both trench etch-refill and interlevel dielectric applications. Film synthesis was carried out at 200°C using a dual coil inductively coupled plasma system. It was determined that the presence SiH4 was not necessary to catalyze the decomposition of GeH4 as required in a strictly thermal environment. Oxide film composition has been determined using Energy Dispersive X-Ray Spectroscopy (EDS) and Auger Energy Spectroscopy (AES). Charging effects usually observed in non-conducting films have been eliminated in the EDS analysis with the use of an Environmental Scanning Electron Microscope (N-SEM) operating at a partial pressure of 150 mTorr of oxygen. EDS and AES results indicate that the on-wafer and wafer-to-wafer compositional uniformity was +/-5% in a caged boat using 4 inch silicon wafers. Cross-sectional Scanning Electron Microscopy has been employed to study the compositional dependency of the flow behavior of the mixed GeO2-SiO2, P2O 5-GeO2-SiO2, B2O 3-GeO2-SiO2, and P2O5-B 2O3-GeO2-SiO2, glass films over silicon trenches under various ambient atmospheres. Reflows were performed at temperatures ranging from 500°C to 1050°C in various gas ambient atmospheres. As result of the work, a low temperature (∼600°C) reflow process was developed resulting in fully planar dielectric film. This process may have application for planarization of interlevel dielectric for ULSI integrated circuits, and is the subject of a patent application.