Low-temperature growth of polycrystalline Ge films on SiO₂ substrate by HDPCVD

Pure and high-quality polycrystalline Ge films have been deposited directly onto fully SiO₂ covered substrates by high-density plasma chemical vapor deposition (HDPCVD) system. Only a tiny amount of O and C near the surface has been observed from X-ray photoelectron spectroscopy and Auger electron spectroscopy data, which may come from surface oxidation and contamination. Very pure Ge composition has been achieved in the bulk of the films. The cubic structure with primarily (111), (220), and (311) orientations of the Ge films is mainly composed of fine grains and can be unambiguously identified from X-ray diffraction patterns. Furthermore, successful Ge film depositions with nearly no incubation time are demonstrated using a mixture of GeH₄/H ₂ as process gas at 400°C. Thickness vs. time analysis was performed by high-resolution transmission electron microscopy. The HDPCVD technique used was able to provide a simple, powerful, and reliable approach in the fabrication of polycrystalline Ge thin film transistors.