Performance and processing line integration of a silicon molecular beam epitaxy system

Abstract

Abstract Silicon molecular beam epitaxy (MBE) has been shown to be a promising technology for ultralow temperature epitaxy. Its capability to deposit strained Si-Ge layers and superlattices has received much attention. In this paper, the design, performance tests and processing line integration of a silicon MBE system capable of handling waters of 150 mm diameter is described. Several parameters, such as particle density, deposition uniformity, background doping, etch pit density and metallic contamination, have been carefully monitored during the first year of operation. These parameters are important acceptance criteria for the integration of silicon MBE into a standard processing line. The deposition uniformity across 140 mm was within 2%. Extensive measurements on the particulates identified the major source to be the first handling of wafers outside the cassette. Levels below 100 cm -2 are found. The background doping has been reduced from around 10 16 to 10 15 cm -3 . Strong reductions have been observed for the metallic contaminants tantalum and chromium. The system has been used as part of a standard processing line for the fabrication of thin, low temperature epitaxial layers. Two examples, epitaxial emitters for bipolar transistors, and p-i-n diodes, are given.