Characterization of silicon dioxide and phosphosilicate glass deposited films

Abstract

Silicate glasses, both undoped and lightly doped with phosphorus, prepared by a low pressure plasma enhanced chemical vapor deposition (PECVD) system using tetraethylorthosilicate or silane as silicon sources and atmospheric pressure chemical vapor deposition technique using silane, were evaluated. The three analyzed phosphosilicate films were nominally 4.0 wt % doped. All the samples were deposited in the temperature range of 350–420 °C. Their main properties such as refractive index, density, wet etch rate, stress, step coverage, moisture resistance, and infrared absorption are reported. Infrared absorption measurements were performed on both as-deposited and annealed films (430 °C for 15 min in N2) to investigate the presence of water and Si–OH groups, as well as P=O and Si–O bond interactions. The P-doped films were tested as final passivation layers on 1 Mbit erasable programmable read only memory devices mounted in ceramic packages. Similar electrical results have been obtained with three different phosphosilicate glass films. However, the most reliable results after assembly and packaging were obtained for films deposited by PECVD technique using tetraethylorthosilicate as the source of silicon in the films.