RF Recrystallization of Polycrystalline Silicon on Fused Silica for MOSFET Devices

Abstract

A new zone melting recrystallization method that uses an RF‐heated carbon susceptor in fabrication of silicon on insulator (SOI) structures has been developed. A fused silica substrate, on which a 0.5–1.0 μm thick polycrystalline silicon film had been deposited, was encapsulated with a 1.2 μm thick layer. This was moved across the carbon susceptor, which had a narrow high temperature zone. The continuous silicon films that were recrystallized had grains several tenths to a few millimeters wide, a few centimeters long, and a film orientation of (100). The electron mobility of MOSFET's fabricated on the films was about 700–1000 cm2/Vs, which was higher than that of (100) orientated bulk single‐crystal silicon. However, as some cracks occurred in the film, it was formed as islands and then the islands were recrystallized. This recrystallized silicon was a single crystal with an orientation of (111) and showed no cracks. The electron field effect mobility of the islands was about 300–600 cm2/Vs, which was smaller than that of the recrystallized continuous film because of the (111) orientation. In order to obtain silicon without cracks and with an orientation of (100), a method that connected the polycrystalline silicon islands with narrow strips was proposed based on a thermal connection of silicon.