Papers by Keyword: VHF PECVD

Abstract: P-type microcrystalline silicon films prepared by electron cyclotron resonance（ECR）PECVD are studied here. Silane diluted with Ar (SiH4/Ar=1/19) is used as a source gas and diborane (B2H6) diluted with H2 (100ppm) as doping gases. The effect of flow rate of doping gas on the microstructures and electrical properties of the films were investigated. Raman spectroscopy and X-ray diffraction were used to determine the film structure; AFM was employed to characterize the film surface topography; Hall measurements were carried out on the doped films to determine the carrier type, carrier concentration, and Hall mobility. The optical quality was measure by transmission spectrum.

Abstract: Nanocrystalline silicon films have been fabricated from SiH4 diluted with H2 in very high frequency (40.68 MHz) plasma enhanced chemical vapor deposition system at low temperatures (250oC). The influence of pressure on the structural properties of nanocrystalline silicon films has been investigated. The experimental results reveal that a very high hydrogen dilution is needed to crystallize the film grown at high pressure. If the hydrogen dilution is not high enough, the film could also be crystallized through lowering the pressure. Furthermore, the crystallinity and grain size increase with decreasing the pressure. These results could be attributed to the increase of ion bombardment energy and the higher atomic hydrogen flux toward the growing film surface at lower pressures.

Abstract: Silicon oxynitride films were deposited in very-high-frequency (40.68 MHz) plasma enhanced chemical vapor deposition (VHF-PECVD), and subsequently annealed between 400 and 1200°C in N2 ambient. The effect of annealing temperature on the PL characteristics of the samples was investigated. The experimental results reveal that a broad PL peak around 430 nm (2.88eV) appears in all of the samples. The maximum intensity of this broad PL peak was obtained in the sample annealed at 400°C. The PL characteristics of the annealed samples were discussed.

Abstract: The silicon nitride films have been deposited by Electron Cyclotron Resonance-plasma enhanced chemical vapor deposition (ECR-PECVD) method at low temperature, and the pure nitrogen is introduced into the ECR chamber as the plasma gas, the silane(Ar diluted, Ar:SiH4=19:1) is used as precursor gas. The optimum deposition parameters of SiN films for photovoltaic application as an efficient antireflection coating(ARC) have been investigated. The actual composition of the films will be varied with the deposition conditions, such as gas flow rate ratio(N2/SiH4), substrate temperature, and microwave power. The effect of deposition parameters on the optical performance of SiN films was determined by Ellipsometry. The Si-N and N-H stretching characteristic peaks of SiN films have been observed by FTIR spectroscopy. Results shown that uniform silicon nitride films with low hydrogen content can be deposited at high deposition rate(10.7nm/min), and the refractive index increased with the increasing of substrate temperature and microwave power. The film shows good optical properties (refractive index is 2.0 or so) and satisfied surface quality (average roughness is 1.45nm) when the deposition parameter is 350oC and microwave power is 650W.

Abstract: 4H-SiC MOSFET devices with low temperature dry thermal oxidation (1050 °C 1 h) and TEOS plasma enhanced CVD deposited oxides on 4H-SiC substrates have been analysed in this paper. MOSFET transistors have been fabricated on the 4H-SiC (0001) Si face. The mobility improvement (up to 38-45 cm2/Vs) is remarkable compared with standard oxidation (<10 cm2/Vs). In addition, very high (but controversial) field-effect mobilities of around 216 cm2/Vs have also been extracted for MOSFETs fabricated on the (11-20) face. Taking into account the threshold voltage and the sub-threshold slope (S), we can see that we have three different ways to increase the mobility. First, by using (11-20) face material as already proposed. Second, by reducing the interface trap density as done with the low temperature thermal oxidation plus deposited oxide. And third, under the most favorable conditions with adequate TEOS deposition conditions. In this last case, the mobility improvement seems to be related with the gate current leakage more than (or together with) an interface traps reduction of the gate insulator.