Catalytic chemical vapor deposition(Cat-CVD) is a method of depositing thin films using radicals formed by the catalytic clacking of gas molecules on a heated catalyzer. Despite its simple configuration, the Cat-CVD can form highly-dense films with a high deposition rate, and realize excellent interface quality between a deposited film and a substrate due to its plasma-damage-less feature. The usage of appropriate source gas and a catalyzer material enables us to form Al2O3, GaN, and organic films such as poly-tetra-fluoro-ethylene(PTFE) as well as Si-related films. The problem of catalyzer aging, which becomes an obstacle for efficient mass-production, could be solved by the careful selection of catalyzer temperature and/or the removal of a surface degraded layer by post-annealing. The Cat-CVD technology has a wide field of application such as electronic devices, encapsulation films against moisture or oxygen, water-repellent coatings, and the removal of carbon-containing layers using highly-dense hydrogen radicals.
Organic catalytic CVD (O-Cat-CVD) is an extension of the conventional Cat-CVD technique to organic substances. O-Cat-CVD utilizes metal organic (MO) compounds as CVD sources and provides various types of organic-inorganic hybrid materials at low substrate temperature below 200oC. The growth instrument using high-melting-temperature metal filaments seems to be simple and easily scaled up. Chemical reactions at the hot filament, vapor phase reactions and substrate surface reaction must be taken into account. Although deep understanding is necessary to the mechanism of O-Cat-CVD growth, the method is quite promising as a key thin-film growth method in the industry like film-based electronics which provides various types of flexible devices such as flexible OLED and flexible solar cells using plastic film substrates.
Free radical species, such as H, O, OH, CH3, and SiH3, can be ejected efficiently to the gas phase by catalytic decomposition of material gases on heated metal surfaces. The detailed reaction mechanisms for the production of these radicals are still hard to be specified, but the mechanisms can be presumed by measuring the radical densities in the gas phase under various conditions. In this review, the results on the detection of these radical species are summarized, and the possible mechanisms taking place on the catalyst surfaces are discussed. The experimental procedures to identify the radical species are also reviewed shortly. In the production of Si atoms from SiH4, the rate determining step changes from Si desorption to SiH4 adsorption with the increase in the catalyst temperature. In the decomposition of H2O, the OH desorption energy depends on the surface coverage. In O2 systems, decomposition takes place not only on the metal surfaces, but also on the second adsorbed layers.
There are a lot of demands for the semiconductor manufacturing process of large-scale integrated circuit(LSI) and LSI package. Especially, low temperature processes for surface cleaning are strongly required. In this paper, we introduce a novel cleaning technology of various metals using atomic hydrogen generated by a heated catalyzer, hot wire (HW) method. In the case of solder bump cleaning in semiconductor packaging, the oxide layer on the Sn surface was completed reduced, and it was confirmed the effectiveness in improving the flip-chip bonding by the atomic hydrogen treatment. In the case of Cu nano ink-jet wiring, the resistivity was drastically decreased by the atomic hydrogen treatment.
Carbon nanowall(CNW) is a carbon nanomaterial that has a wall structure consisting of graphite, which stands on a substrate. Owing to this structure, the CNW shows interesting characteristics such as a large surface area and a high aspect ratio. Therefore, CNW is expected to be used as capacitor electrodes and electron field emitters. Catalytic chemical vapor deposition(Cat-CVD) has advantages including the use of convenient and low-cost equipment and the high decomposition rate of the source gas. This method has been used in the deposition of diamond, silicon films and carbon nanotubes. We used this method for the deposition of CNWs. In this paper, I present the preparation of CNWs by Cat-CVD including discuss of the growth of CNWs.