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 N2 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.

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