Properties Of Ge Films Grown Through Inductively Coupled Plasma Chemical Vapor Deposition On Sio2 Substrates

In this study, we investigated the physical and electrical characteristics of Ge polycrystalline films deposited directly onto SiO2-covered substrates using inductively coupled plasma chemical vapor deposition (ICP-CVD). The pure Ge films that we deposited at a relatively low temperature of 300 degrees C exhibited the same cubic structure, with primarily (111), (220), and (311) orientations identified from X-ray diffraction patterns, as those deposited at 400 degrees C. The use of such a low temperature not only prevented the plasma window of the chamber from overheating but also allowed crack-free, thicker films to be deposited more easily. The ability to deposit Ge films on SiO2 was closely linked to the hydrogen etching effect, as evidenced by the results obtained using X-ray photoelectron spectroscopy. Although the crystalline characteristics of the low-temperature as-deposited Ge films were somewhat poorer than those obtained at 400 degrees C, subsequent furnace annealing and rapid thermal annealing with a SiNx capping layer improved the crystalline quality significantly. These results, taken together with studies of the surface morphologies and dopant activation of the recrystallized Ge films, suggest that ICP-CVD might be a simple, powerful and reliable approach for the fabrication of polycrystalline Ge thin film transistors. (c) 2008 The Electrochemical Society.