ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.349732
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