Evolution with thickness of the structure of the polycrystalline silicon (poly-Si) films prepared at 300 °C has been studied by plasma decomposition of SiF4/SiH4/H2 source gases. The poly-Si films with varied thickness are characterized mainly by Raman spectroscopy, x-ray diffraction (XRD), and supplementarily by reflection high-energy electron diffraction, transmission electron microscopy, Fourier-transform infrared (FT-IR) spectroscopy, electron-spin resonance (ESR), and secondary-ion-mass spectroscopy (SIMS) measurements. The crystalline fraction of the film was calculated to be 87% by deconvoluting the Raman spectra. The grains indicated a strong 〈110〉 preferred orientation by XRD. The thickness (d) dependence of the diffracted (220) intensity is divided into three regions: an incubation region (d<200 nm, region 1), a linear region (200 nm ≤d<300–500 nm, region 2) where the deposition parameter (SiF4 flow rate, substrate temperature, and rf power) dependence is weak, and a linear region with steeper (or more moderate) slopes (300–500 nm≤d, region 3) where the deposition parameter dependence is large. The measurements of the angular distribution of the 〈110〉 grains reveal that they contain slanting ones by more than 4° in region 2, while they disappear in region 3. The FT-IR and SIMS measurements for typical samples (Ts = 300 °C, 300 Pa) indicate that the grain boundaries are passivated by hydrogen in the bonding configurations of Si—Hn (n=1–3) and its concentration is approximately 3 at. %. The residual fluorine in the film is found to be much fewer (6×1019 cm−3) than hydrogen. It is found that the density of unpassivated dangling bonds indicates a low value of 1.1×1017 cm−3 for the film with d=280 nm by ESR measurements. The origin of the preferred orientation is also discussed on the basis of a model in which nucleation, ledge formation, and etching processes are considered.

We have systematically characterized oxygen (O) and carbon (C) impurities in undoped gallium aluminum arsenide ( Al x Ga1- x As) epitaxial layers grown by organometallic vapor-phase epitaxy (OMVPE). The concentrations of O and C impurities are evaluated by secondary-ion mass spectroscopy. For x≤0.63 the increase rate of O concentration, [O], with x is nearly proportional to the flow rate of trimethylaluminum (TMA), indicating that the oxygen is contained in the TMA molecules. In contrast, [O] and [C] increase superlinearly with x for x≥0.83, and particularly, [O] exceeds 1018 cm-3. The vibration mode of Al–O bonds is observed at 900–1050 cm-1 for the x=0.83 sample using Fourier-transformation infrared measurements. The superlinear increase of [O] with x is attributed to the increased adsorption of residual O2 or H2O molecules. The mechanism of the superlinear increase is discussed in terms of statistic consideration of the –Al– arrangement on the Al x Ga1- x As surface. Hall measurements show that the hole concentration markedly decreases for x>0.63 and the Al x Ga1- x As layer becomes semi-insulating, which was attributed to hole compensation by the O-related deep hole traps. The hole mobility also decreases in the same x range.

Plasma etching of ITO (In2O3:Sn indium tin oxide) thin films has been performed using a CH4/H2 plasma. Etching occurs above a substrate temperature (T s) of 60°C and the etch rate increases with increasing T s, while amorphous like or polymer-like carbon deposits onto the ITO films below 60°C. The apparent activation energy of the etching is 4.12 kcal/mol (0.18 eV). This small activation energy suggests that the desorption of produced volatiles is the rate-limiting process. Fine ITO patterns (1.5 µmL/S) were obtained using this gas mixture.

Polycrystalline-Si (poly-Si) films have been prepared on glass substrates (Corning 7059) at a very low temperature (300°C) by conventional plasma chemical vapor deposition (plasma CVD) using SiF4/SiH4/H2 gases. The crystallinity was characterized by X-ray diffraction, reflection high-energy electron diffraction (RHEED), transmission electron microscopy (TEM) and Raman spectroscopy measurements. The effect of the SiH4 flow rate on crystallization proved to be large. The films indicated a strong <110>-preferred orientation. The crystalline fraction was estimated to be more than 80%. The average and maximum grain sizes were estimated to be 60 nm and 130 nm, respectively.

The effects of phosphine doping on the electronic and structural properties of polycrystalline silicon (poly-Si) films prepared by plasma chemical vapour deposition using SiF4/SiH4/H2 gases have been investigated. With increasing doping ratio, the conductivity rapidly increases and takes a maximum value of 80 S·cm-1 at [PH3]/[SiH4](=γ)∼1.7×10-2, while it decreases at larger doping ratios. This change is found to be caused mainly by the change in the carrier density, by Hall measurements. X-ray diffraction and transmission electron microscopy indicate that this electronic change is associated with the change in the preferred orientation of grains from <110> to <111> with a slight decrease in grain size, and the structural change from crystalline to amorphouslike with increasing γ.