Catalytic chemical vapor deposition method to prepare high quality hydro‐fluorinated amorphous silicon
01 Dec 1988-Journal of Applied Physics (American Institute of Physics)-Vol. 64, Iss: 11, pp 6505-6509
TL;DR: In this paper, a new type of chemical vapor deposition method, named "Catalytic-CVD" method, is presented, in which deposition gases are decomposed by catalytic or pyrolytic reaction between deposition gases and a heated catalyzer, and films are thermally grown on a substrate at temperatures lower than 300°C without any help from glow discharge plasma.
Abstract: A new type of chemical vapor deposition method, named ‘‘Catalytic‐CVD’’ method, is presented. In the method, deposition gases are decomposed by catalytic or pyrolytic reaction between deposition gases and a heated catalyzer, and films are thermally grown on a substrate at temperatures lower than 300 °C without any help from glow discharge plasma. Hydro‐fluorinated amorphous silicon (a‐Si:F:H) films are deposited by this method using both a SiF2 and H2 gas mixture and a SiH2F2 and H2 mixture. It is found that a very high quality a‐Si:F:H film can be obtained, and for instance, that the photosensitivity for AM‐1 of 100 mW/cm2 exceeds 106 and the spin density is as low as 6×1015 cm−3.
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TL;DR: In this paper, a new type of thermal chemical vapor deposition (CVD) method is presented, where material gases are decomposed by catalytic or pyrolytic reaction with a heated catalyzer, so that films can be deposited at temperatures less than 300°C without any plasma or photochemical excitation.
Abstract: A new type of thermal chemical vapor deposition (CVD) method is presented. In the method, material gases are decomposed by catalytic or pyrolytic reaction with a heated catalyzer, so that films can be deposited at temperatures less than 300 °C without any plasma or photochemical excitation, and the method is particularly called ‘‘Catalytic‐CVD.’’ Hydrogenated amorphous silicon films are deposited by this method, and the deposition mechanism is also investigated. It is found that device‐quality amorphous silicon films can be obtained and that inactive species, which are generated at the catalyzer and transported without gas‐phase reactions, are key species to make a high‐quality film by this method.
125 citations
TL;DR: The optical, electronic and structural properties of thin films deposited by Hot-Wire chemical vapor deposition with filament temperatures, Tfil, between 1500 and 1900 C from silane and hydrogen are studied in this paper.
Abstract: The optical, electronic and structural properties of thin films deposited by Hot‐wire chemical vapor deposition with filament temperatures, Tfil, between 1500 and 1900 °C from silane and hydrogen are studied. The substrate temperature, Tsub, was kept constant at 220 °C. Amorphous silicon films (a‐Si:H) are obtained at high filament temperatures, low deposition pressures and low hydrogen‐to‐silane flow rate ratio (Tfil∼1900 °C, p<30 mTorr and FH2/FSiH4≤1). At these deposition conditions, high growth rates are observed (rd≥10 As−1) both with and without hydrogen dilution, and no silicon deposition was observed on the filaments. However, if a lower filament temperature is used (Tfil∼1500 °C) a transition from a‐Si:H to microcrystalline silicon (μc‐Si:H) occurs as the pressure is decreased from above 0.3 Torr to below 0.1 Torr. The highest dark conductivity and lowest activation energy, of ∼1 Scm−1 and <0.1 eV, respectively, were observed for μc‐Si:H deposited at p∼50 mTorr. In this Tfil regime, μc‐Si:H growt...
50 citations
TL;DR: In this article, it was shown that the temperature dependence of the carbon deposition rate is similar to the sublimation rate of carbon from graphite and tungsten carbide.
Abstract: Pure glassy carbon films [no x‐ray photoelectron spectroscopy (XPS) detectable impurities above the 0.5% level] as thick as 25 000 A have been grown on nearby silicon substrates (T≳100 °C) as a result of reactions between a hot tungsten filament and cyclopentane. Above ∼2500 °C, cyclopentane‐tungsten reactions yield a liquid W/C eutectic which limits filament operation. Below ∼2500 °C, resistance changes of the filament and XPS spectra show such reactions form carbides and graphite. It is shown that the temperature dependence of the carbon deposition rate is similar to the sublimation rate of carbon from graphite and tungsten carbide. Moreover, it is also shown that C1, C2, and C3 (carbon monomers, dimers, and trimers) are evaporated from carbarized tungsten and also from graphite. These results suggest that carbon film growth is a consequence of evaporation of carbon from the carbarized tungsten filament, with steady‐state film deposition occurring as a result of a quasisteady state in the formation and ...
24 citations
TL;DR: In this article, a kinetic growth model for hot-wire chemical vapor deposition in the Tfil∼1200°C regime is proposed, and the Optoelectronic properties are controlled by the substrate temperature Tsub, and show different dependences for new and old filaments.
Abstract: Hydrogenated amorphous silicon, a‐Si:H, is deposited from silane and hydrogen by hot‐wire chemical vapor deposition using a tungsten wire filament at a temperature Tfil=1200 °C. Film properties depend on whether the films were deposited using filaments with an accumulated deposition time lower than 90 min (‘‘new’’ filaments) or longer than 90 min (‘‘old’’ filaments). The deposition rate for films deposited with ‘‘new’’ filaments is 4 times higher than that for aged filaments. For ‘‘new’’ filaments, a monotonic increase of the growth rate, rd, with the pressure is observed, as well as a maximum of rd for FH2/FSiH4 close to unity. The optoelectronic properties are controlled by the substrate temperature Tsub, and show different dependences for ‘‘new’’ and ‘‘old’’ filaments. The Urbach band tail energy, Eu, is lower for films deposited with ‘‘new’’ filaments. A kinetic growth model for hot‐wire chemical vapor deposition in the Tfil∼1200 °C regime is proposed.
21 citations
References
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TL;DR: In this paper, a simple model based on the existence of internal electric fields is suggested to explain the exponential part of the absorption edge observed in many amorphous semiconductors.
1,150 citations
TL;DR: In this paper, it was shown that substitutional doping of an amorphous semiconductor is possible and can provide control of the electronic properties over a wide range, which corresponds to a movement of the Fermi level of 1·2 eV.
Abstract: It is shown that substitutional doping of an amorphous semiconductor is possible and can provide control of the electronic properties over a wide range. a-Si and Ge specimens have been prepared by the decomposition of silane (or germane) in a radio-frequency (r.f.) glow discharge. Doping is achieved by adding carefully measured amounts of phosphine or diborane, between 5 × 10−6 and 10−2 parts per volume, to obtain n- or p-type specimens. The room temperature conductivity of doped a-Si specimens can be controlled reproducibly over about 10 orders of magnitude, which corresponds to a movement of the Fermi level of 1·2 eV. Ion probe analysis on phosphorus doped specimens indicates that about half the phosphine molecules in the gaseous mixture introduce a phosphorus atom into the Si random network; it is estimated that 30–40% of these will act as substitutional donors. The results also show that the number of incorporated phosphorus atoms saturates at about 3 × 1019 cm−3, roughly equal to the number ...
624 citations
TL;DR: In this article, a new method of producing high quality hydrogenated amorphous silicon (a-Si:H) films was presented, without using any plasmas or photochemical excitation, but using only thermal and catalytic reactions between deposition-gas and heated tungsten catalyzer.
Abstract: A new method of producing high quality hydrogenated amorphous silicon (a-Si:H) films is presented. An SiH4. and H2 gas mixture is decomposed without using any plasmas or photochemical excitation, but using only thermal and catalytic reactions between deposition-gas and a heated tungsten catalyzer. Photoconductivity of films produced by this methodreaches 10-3 (Ωcm)-1 and photosensitivity exceeds 105 for illumination of AM-1 light of 100 mW/cm2.
151 citations
TL;DR: Amorphous silicon (a•Si) films are deposited at about 320˚C by a new thermal chemical vapor deposition method as mentioned in this paper, where the gas mixture of intermediate species SiF2 and H2, decomposed thermally by the catalytic reaction, is used as a material gas.
Abstract: Amorphous silicon (a‐Si) films are deposited at about 320 °C by a new thermal chemical vapor deposition method. In this method, the gas mixture of intermediate species SiF2 and H2, decomposed thermally by the catalytic reaction, is used as a material gas. It is found that the photosensitivity of the a‐Si film for AM1 of 100 mW/cm2 exceeds over 106 and that the spin density is as low as 1.5×1016 cm−3 for the film deposited with a rate of several A/s.
114 citations