Effects of high-temperature rapid thermal annealing on the residual stress of LPCVD-polysilicon thin films

Abstract

The effects of regular furnace and high-temperature rapid thermal annealing (RTA) on the residual stress of LPCVD-polysilicon thin films were investigated. The as-deposited 0.5 mu m thick polysilicon films had an initial compressive stress of about 340 MPa, and the residual stress was relaxed quickly after a few cycles of RTA at the higher temperatures. The stress variation with annealing time at temperatures of 900-1150 degree C was analyzed. Using X-ray diffraction (XRD), micro-Raman spectroscopy and transmission electron microscopy (TEM), the changes in the microstructure of the thin films, induced by the RTA, during the stress relaxation were studied. Compared to regular furnace annealing, rapid thermal annealing can reduce stress in a short time and is an effective method for releasing the residual stress in polysilicon thin films.