Present Status Of Hot Wire Chemical Vapor Deposition Technology

Abstract

AbstractIn the last few years, tremendous progress has been made in the field of Hot Wire Chemical Vapor Deposition (HWCVD): (1) It has been shown that there are no fundamental limitations in HWCVD with respect to substrate area. Using a periodic configuration of multiple short wires, good uniformity (± 7.5 %) has been demonstrated by Anelva over an area of 96 cm × 40 cm. (2) High quality microcrystalline Si can be produced. Solar cells in the n-i-p configuration are currently better than those made by PECVD. At Jülich, the efficiency of such cells is 9.4 %, and Utrecht has recently made the first HWCVD multibandgap triple junction solar cells, (3) HWCVD offers the potential of ultra high deposition rates. At NREL, a-Si:H has been deposited at rates in excess of 12 nm/s, and at Utrecht University μc-Si:H rates are in excess of 1 nm/s. (4) Thin film transistors (TFTs) with mobilities in excess of 1 cm2/Vs with an a-Si:H channel have been shown to be stable and μc-Si:H TFTs have been made with mobilities in excess of 40 cm2/Vs. (5) The efficient production of atomic H in HWCVD is beneficial in passivation processes, but it can also be applied in efficient etching processes. (6) Alloys of Si with various functions can be made, such as SiNx for antireflection and passivation coatings. Remarkably, all of the above results have been achieved without detailed knowledge about the primary reactions at the filament, the gas phase reactions, and the reactions with the growing film. The choice of filament material and its operation temperature have a large influence on the production of various reaction species and thus, on the structure of the resulting film. HWCVD is basically an ion-free deposition technique, which is an advantage for many kinds of thin films. HWCVD has also proven its feasibility in polymer deposition and nanotube formation.