Low-Temperature LPCVD of Polycrystalline Ge[sub x]Si[sub 1−x] Films with High Germanium Content

Abstract

A study of low-pressure chemical vapor deposition (LPCVD) of normalGexnormalSi1−x (x<0.65) films was carried out. The films were deposited on thermally oxidized silicon wafers at deposition temperatures of 430–480°C . Pure GenormalH4 and SinormalH4 (or normalSi2normalH6 ) gas sources were used. It has been found that the reactive sticking probability ratio between GenormalH4 and SinormalH4 varies between 11 and 3.5, depending on both the deposition temperature and film composition. An increase of germanium content from 40 to 60 atom % caused a sharp increase of deposition rate. The polycrystalline layers mainly contained (110)- and (111)-oriented grains. The (111)-oriented grains were overgrown by the (110)-oriented grains at 430°C after a film thickness of about 100nm . Reducing the total pressure below 10Pa led to a dominance of (111)-oriented grains. A relative GenormalH4 depletion in the downstream direction influenced both the composition and crystallinity of the layers, and the deposition rate. To minimize the depletion effect, normalSi2normalH6 has been used instead of SinormalH4 . No improvement has been obtained but the depletion from normalSi2normalH6 occurred instead of the depletion from GenormalH4 . A proper mixture of SinormalH4 , normalSi2normalH6 , and GenormalH4 can be suggested to compensate the depletion effects.

Vapor-Liquid-Solid Growth of Si1-xGex and Ge/Si1-xGex Axial Heterostructured Nanowires

“…Therefore, even though the amount of Si 2 H 6 is lower in the gas phase, it adsorbs more efficiently on the droplet than GeH 4 and thereby reduces the Ge/Si ratio in the Au liquid compared to the gas phase, for example, at the highest GeH 4 partial pressure, 0.05% disilane in the gas phase supplies about 20% of Si in the nanowires. The sticking coefficient of GeH 4 has been reported to be lower than that of Si 2 H 6 for the case of Si 1-x Ge x thin film deposition where the germane to disilane sticking probability was calculated as 0.4 at 430ºC and x ~ 0.5 (14). This may be the case for nanowires as well, although the sticking coefficients of the molecules on the liquid droplet are expected to be much higher (15).…”

Synthesis and Characterization of Boron Thin Films Using Chemical and Physical Vapor Depositions

“…Results are therefore machine and material dependent. In fact, similar to the deposition techniques employed in this work to realize boron thin films, over the last decades for a variety of thin films/materials and/or deposition techniques investigations/characterizations/optimizations were performed by MESA + affiliated academic research groups [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. This work is dedicated to research in the realization of boron thin films and focuses on typical film characteristics of films obtained with various deposition techniques.…”

CMOS-MEMS post processing compatible capacitively transduced GeSi resonators

“…This calls for a change of structural materials, as the monocrystalline and polycrystalline silicon, commonly employed as structural layer in microresonators, require processing incompatible with backend technology [8,9]. Germanium-silicon alloys are an attractive alternative, as they are deposited in polycrystalline form at temperatures below 450 °C [10]; under similar conditions silicon deposits in amorphous form.…”