Low Pressure Deposition of Doped SiO2 by Pyrolysis of Tetraethylorthosilicate (TEOS): I . Boron and Phosphorus Doped Films

Abstract

Borophosphosilicate glass (BPSG) with high dopant levels has been obtained by combining the low pressure TEOS‐borosilicate glass (BSG) and phosphosilicate glass (PSG) processes at an optimum deposition temperature of 620°C. The process has been improved with regard to uniformity and run‐to‐run stability by introducing the trimethlyborate used for the boron doping from the front end, while the phosphine employed requires a quartz injector. The BPSG layers exhibit good chemical stability and flow properties at 850°C as well as an excellent step coverage. The wet etch rate of BPSG and BSG is not changed by a anneal. Experiments with BPSG and BSG showed that a void free trench filling is only feasible for trenches with tapered walls, but a heat‐treatment at 900°C reduces the cavities to small bubbles in the trench center and planarizes the surface. By using a rapid anneal system, an elimination of the bubbles as well as a totally planarized surface can be achieved with a 1100°C, 30s pulse for BSG with 6 weight percent boron.