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We have investigated the thermal stability of nickel monogermanide (NiGe) films formed by rapid thermal annealing on both single- and polycrystalline Ge substrates. We found that the NiGe phase is the only one present after nickel germanidation in the temperature range 400–700°C. A fairly uniform NiGe film formed on the single-crystalline Ge; it possessed excellent resistivity (15.6μΩcm) and was thermally stable up to 550°C, but it degraded rapidly at higher temperatures as a result of agglomeration. In contrast, the NiGe film formed on the polycrystalline Ge exhibited much poorer thermal stability, possibly because of polycrystalline Ge grain growth, which resulted in columnar NiGe grains interlaced with Ge grains that had a dramatically increased sheet resistance. As a result, we observed that the sheet resistances of NiGe lines subjected to annealing at 500°C depended strongly on the linewidth when this width was comparable with the grain size of the polycrystalline Ge.

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...

Thermochemical behavior of hydrogen in hafnium silicate films on Si

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