TABLE OF CONTENTS Doped polycrystallinc silicon (poly-Si) is commonly used as gate material in MOS structures and as contact material for bipolar transistors. Poly-SiGe film has emerged as a new material for advanced CMOS technology and low temperature thin film transistor (TFT) fabrication for large area display electronics. Commonly used source gases for deposition of poly-SiGe are SiH4 and GeH 4 in the temperature range 400 600 C.
Rapid thermal CVD has been employed to grow poly-SiGe films [5]. However, these films suffer from higher oxygen content and difficulty of nucleation on oxide. VLPCVD has been found to yield high quality films on oxidized Si substrates at a lower temperature (400 600 C) and at pressures < 4 mTorr using an rf power of 4 W only. Compared to LPCVD, the plasma enhanced deposition technique gives higher growth rate, smaller grain sizes, direct deposition on oxide, and improved structural properties such as smoother surface and a more columnar grain structure.
King and Saraswat [165] have used the conventional LPCVD technique to deposit poly crystalline Si 1 ? xGe x films of different compositions at 625 C and at pressures between 0.1 to 0.2 Torr using SiH 4 and GeH 4 as the precursor gas sources. The films were heavily doped with boron and phosphorus by ion implantation at a dose of 4 10 15 cm ?2 with energy 20 keV for boron and 60 keV for phosphorus and annealed at 900 C for...
