The crystallization of undoped amorphous silicon films deposited by low‐pressure chemical vapor deposition in the temperature range 580–530 °C and annealed from 550 to 950 °C has been studied by transmission electron microscopy. The average grain size of the crystallized films depends on the annealing temperature and the deposition conditions. The nucleation rate of new grains during annealing decreases as the deposition temperature decreases from 580 to 545 °C and/or when the deposition rate increases. The final grain size is also influenced by the annealing temperature with the largest grain size obtained at low annealing temperatures. A simple model is described which explains the dependence of grain size on the annealing temperature. An average grain size of 500 nm has been obtained in a 200‐nm film deposited at 545 °C and annealed at 550 °C.

Large grain polycrystalline silicon by low‐temperature annealing of low‐pressure chemical vapor deposited amorphous silicon films

We present a thorough study of the microstructure, texture, intrinsic stress, surface, and interface morphology of transition metal nitride (mainly TiN but also CrN) films grown on Si by reactive sputter deposition, with emphasis to the mechanisms of adatom migration on the surface and subplantation of energetic species. In order to study the effects of adatom mobility and the subplantation probability we vary the ion energy and growth temperature. For the experimental part of this work we used nondestructive, statistically reliable x-ray techniques (diffraction, reflectivity, scattering). The x-ray results are compared and correlated with supporting data of in situ spectroscopic ellipsometry as well as Monte Carlo simulations of the irradiation effects and surface diffusion of adatoms. We found that the texture and the surface and interface morphology are sensitive to the mechanism of dissipation of the impinging ions. If the energy is enough to overcome the subplantation threshold (∼50eV), then the film...

Surface kinetics and subplantation phenomena affecting the texture, morphology, stress, and growth evolution of titanium nitride films

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.

Structural properties of polycrystalline silicon films prepared at low temperature by plasma chemical vapor deposition

Structure and crystal growth of undoped, as‐deposited, and annealed silicon films prepared by chemical vapor deposition (CVD) and low‐pressure chemical vapor deposition (LPCVD) of silane have been studied with use of x‐ray diffraction, Raman spectroscopy, and scanning electron microscopy (SEM). The grain size and a complete texture analysis are performed on CVD films grown at atmospheric pressure and temperature range 600≤Td≤805 °C, LPCVD films grown in the pressure range 0.1≤Pd≤2 Torr and temperature range 500≤Td≤650 °C and annealed amorphous CVD and LPCVD films near Ta=600 °C. We obtain systematically amorphous, strong 〈220〉 polycrystalline, and inhomogeneous partially crystallized films 〈111〉 or 〈311〉 oriented depending on the deposition conditions. The presence of a given texture is explained by a model which takes into account the specific free surface energies of the starting equilibrium forms and the extinction of some crystalline planes by {111} slow growing facets. The appearance of the 〈220〉 tex...

Structure and crystal growth of atmospheric and low-pressure chemical-vapor-deposited silicon films

Solid phase crystallization of thin films of undoped amorphous Si prepared by plasma enhanced chemical vapor deposition has been studied by transmission electron microscopy (TEM). From the TEM images, the thermodynamic parameters for the amorphous and crystalline phases were extracted. These parameters were compared with those previously reported for evaporated, chemical vapor deposited, and self‐implanted amorphous Si. We conclude that the thermodynamic parameters are very similar for different amorphous Si films, although the initial structure of the films is comparatively different from one to another. To explain this, the existence of an intermediate amorphous state is assumed and discussed.

Solid phase crystallization of thin films of Si prepared by plasma‐enhanced chemical vapor deposition

Crystallization study of chemically vapour-deposited amorphous silicon films by in situ x-ray diffraction

The NASA K2 mission that succeeded the nominal Kepler mission observed several hundreds of thousands of stars during its operations. While most of the stars were observed in single campaigns of 80 days, some of them were targeted for more than one campaign. We perform an asteroseismic study of a sample of eight solar-like stars observed during K2 Campaigns 6 and 17. We first extract the light curves for the two campaigns using two different pipelines, EVEREST and Lightkurve. The seismic analysis is done on the combined light curve of C6 and C17 where the gap between them was removed and the two campaigns were stitched together. We determine the global seismic parameters of the solar-like oscillations using two different methods (A2Z pipeline and the apollinaire code). We perform the peak-bagging of the modes to characterize their individual frequencies. By combining the frequencies with the Gaia DR2 effective temperature and luminosity, and metallicity for five of the targets, we determine the fundamental parameters of the targets using the IACgrids based on the MESA code. While the masses and radii of our targets probe a similar parameter space compared to the Kepler solar-like stars with detailed modeling, we find that for a given mass our more evolved stars seem to be older compared to previous seismic stellar ensembles. We calculate the stellar parameters using two different grids of models, incorporating and excluding the treatment of diffusion, and find that the results agree generally within the uncertainties, except for the ages. The seismic radii and the Gaia DR2 radii present an average difference of 4% with a dispersion of 5%. Although the agreement is quite good, the seismic radii are slightly underestimated compared to Gaia DR2 for our stars, the disagreement being greater for the more evolved ones.

N. Proust

Papers

Structure and crystal growth of atmospheric and low-pressure chemical-vapor-deposited silicon films

Crystallization study of chemically vapour-deposited amorphous silicon films by in situ x-ray diffraction

Multi-campaign asteroseismic analysis of eight solar-like pulsating stars observed by the K2 mission