Polycrystalline silicon–germanium films on oxide using plasma-enhanced very-low-pressure chemical vapor deposition

Abstract

Si1−xGex thin films on oxide-coated Si substrates have been formed by plasma-enhanced very-low-pressure chemical vapor deposition. Two modes of deposition, thermal and plasma enhanced, were studied using SiH4 and GeH4 at temperatures ≤600 °C. In both cases, growth rates and grain sizes increase with Ge content, and the polycrystalline-to-amorphous transition temperature is lower for Si1−xGex than Si. Compared to thermal growth of polycrystalline Si1−xGex, plasma-enhanced deposition of poly-Si1−xGex promotes higher growth rates, smaller grain sizes, and direct deposition onto oxide, as well as improved structural properties such as a smoother surface and a more columnar grain texture. Plasma deposition of amorphous-Si1−xGex films followed by a crystallization anneal at 600 °C results in an even smoother surface morphology with grain sizes enhanced by an order of magnitude compared to plasma-deposited poly-Si1−xGex films.

Effects of Ge on Material and Electrical Properties of Polycrystalline Si1 − x Ge x for Thin‐Film Transistors

“…5. 16 Plasma-deposited poly-Sil_xGe= films have grains that are smaller by a factor of about three compared to polySt1_= G% films thermally grown at the same temperature of 500~ despite more than a doubling of film thickness. This reduction is due to the plasma process generating a higher concentration of initial nuclei which then lead to smaller final grain sizes.…”

Introduction

“…One possibility to increase the deposition rate is to use Plasma Enhanced CVD (PECVD) techniques. For the same deposition temperature and germanium content, a significant increase in growth rate can be achieved by employing PECVD [64]. For example, a PECVD SiGe deposited at 400 • C has almost the same deposition rate as Low Pressure CVD Fig.…”

Suppression of boron penetration by polycrystalline Si1−x−yGexCy in metal–oxide–semiconductor structures

“…2 In this letter, we demonstrate the use of polycrystalline Si 1ϪxϪy Ge x C y as part of a polycrystalline gate to improve the problem of boron penetration. 7 Samples were fabricated by first thermally oxidizing ͑100͒ silicon wafers in dry oxygen at 900°C for ϳ15 min, resulting in 80-90 Å oxides. 5 Polycrystalline Si 1Ϫx Ge x -based gates have previously been studied because it is possible to adjust the work function of the gate electrode by a few tenths of a volt by varying the germanium fraction.…”