Low-Temperature Growth of Polycrystalline Ge Films on SiO2 Substrate by HDPCVD

Abstract

Pure and high-quality polycrystalline Ge films have been deposited directly onto fully SiO 2 covered substrates by high-density plasma chemical vapor deposition ͑HDPCVD͒ 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 ͑111͒, ͑220͒, and ͑311͒ 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 GeH 4 /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.Ge has attracted more and more attention due to its wide applications in ultralarge scale integration ͑ULSI͒ and booming nanotechnologies. Ge/Si and SiGe/Si heterostructures have been used in high-performance devices because of their higher electron and hole mobility compared to Si. 1-5 Three-dimensional Ge islands formed on Si surfaces by solid-phase epitaxy technique have also been demonstrated to have great potential in the fabrication of nanostructures. 6 In addition, Ge-on-insulators ͑GOI͒ is especially desired for achieving extremely high performance metal oxide silicon field-effect transistors ͑MOSFET͒ with sufficiently low leakage current. 7,8 However, for thin film transistor ͑TFT͒ applications, successful Ge thin film deposition on SiO 2 substrates using chemical vapor deposition ͑CVD͒ techniques has not been demonstrated so far due to the extremely long incubation times needed. [9][10][11][12][13][14][15] In the present study, we demonstrate the deposition of polycrystalline Ge films directly onto fully SiO 2 covered Si substrates with nearly no incubation time by using high-density plasma CVD ͑HD-PCVD͒ technique at 400°C. X-ray photoelectron spectroscopy ͑XPS͒ and Auger electron spectroscopy ͑AES͒ analyses show that the deposition of very pure Ge thin films can be achieved without significantly detectable O and C incorporations. X-ray diffraction ͑XRD͒ patterns clearly illustrate that the deposited Ge films are of cubic structure with primarily ͑111͒, ͑220͒, and ͑311͒ orientations, respectively, and are mainly composed of small grains with sizes around 14 nm calculated from full width at half-maximum ͑fwhm͒. Moreover, the results of high-resolution transmission electron microscopy ͑HRTEM͒ analysis firmly show that only very short incubation time is needed for the deposition. Because CVD has the advantage of uniformity control over other techniques such as sputtering 16 and e-gun deposition, 17,18 which is highly important in mass production, this technique, therefore, provides a simple, power...

Properties of Ge Films Grown Through Inductively Coupled Plasma Chemical Vapor Deposition on SiO[sub 2] Substrates

“…Figure 1 displays XPS spectra of the as-grown Ge films deposited at 300 and 400°C. Consistent with our previous findings, 20 a very sharp Ge peak was clearly evident for each sample at a binding energy of 29.2 eV, with a small shoulder at higher binding energy, which we attribute to the formation of surface GeO 2 through oxidation when the sample was exposed to air. The AES profile of the Ge film deposited at 300°C ͑Fig.…”

“…18,19 In this paper, we report the physical and electrical properties of Ge films deposited at 300°C using inductively coupled plasma ͑ICP͒-CVD techniques. In a previous study, we demonstrated that the deposition could be performed at 400°C, 20 but such a high temperature caused overheating of the plasma windows ͑the top plate for plasma generation͒ and led to the formation of an abundance of particles, which is obviously detrimental to the quality of the Ge films. Increasing the cooling interval from run to run could relieve the overheating of the plasma window, but it would decrease the throughput of the production.…”

O3-TEOS CVD Film Formation on Thermal SiO2Pre-Coated with Ethanol

“…It has been reported that in CVD processes, a delay occurs before film growth starts. [32][33][34] Saga et al reported that an organic contaminant adsorbed on silicon surfaces causes a delay in film growth during low-pressure chemical vapor deposition (LP-CVD) processes. 32 These findings support our observation that the Si-OR surface generated by ethanol treatment had a delay on the light-etched thermal SiO 2 as shown in Figure 2.…”

Plasma nanofabrications and antireflection applications

“…As the Si-O bonds are broken by the ion bombardment, the incubation time of Ge on SiO 2 is reduced from many hours to only a few seconds. Figure 1 shows an example that a polycrystalline Ge layer was deposited successfully on SiO 2 by inductively coupled plasma chemical vapour deposition (ICPCVD) for 10 min [10].…”