Properties of Polycrystalline Si1 − xGex Films Grown by Ultrahigh Vacuum CVD Using Si2 H 6 and GeH4

Abstract

Polycrystalline films have been suggested as a promising alternative to the currently employed polycrystalline silicon (poly-Si) gate electrode for complementary metal oxide semiconductor field effect transistor technology due to lower resistivity, less boron penetration, and less gate depletion effect than that of poly-Si gates. We investigated the formation of poly- films by using ultrahigh vacuum chemical vapor deposition CVD with and gases, and studied their physical properties as well as electrical characteristics. The deposition rate and Ge content of poly- films increased linearly with the flux of up to a critical flux, while, above this critical flux, it is slightly changed. The resistivity of poly- films decreased as the Ge content increased, and was about one-half of that of poly-Si films at a Ge content of 45%. The capacitance-voltage measurements of metal oxide semiconductor capacitor structures with gates demonstrated that the flatband voltage of the films was lower than that of poly Si films by 0.2 V. In addition, the changes of flatband voltage with the dosage of boron and the sudden decrease of accumulation capacitance in the gate structure were investigated. Leakage current levels increased slightly due to the difference in with the increase of Ge content in poly films. © 2003 The Electrochemical Society. All rights reserved.