Hajime Shirai, Takeshi Arai and Takuya Nakamura

Faculty of Engineering, Saitama University, 255, Shimo-Okubo, Urawa, Saitama 338, Japan

shirai@sacs.sv.saitama-u.ac.jp

Major issues associated with the manufacture of hydrogenated microcrystalline silicon (uc-Si:H) thin films using current deposition processes are low deposition rate, the control of the film crystallinity and morphology for practical large-scaled electronic devices such as solar cell and thin film transistors (TFTs). Generally, it is difficult to improve the deposition rate, as far as RF plasma-enhanced chemical vapor deposition (RF-PECVD) technique is concerned from SiH4 highly diluted in H2. So far, several approaches have been made to improve the deposition rate of uc-Si:H and poly-Si using low-pressure and high-density plasmas, including electron cyclotron resonance (ECR) plasma, helicon wave plasma and plasma gun CVD with magnetic fields. Among these plasma sources, ECR plasma CVD gas been successfully applied for the thin film deposition of highly photoconductive hydrogenated amorphous silicon (a-Si:H), a-SiGex:H and uc-Si:Cx alloy films. However, high electron temperature and the impinging ion bombardment do damage film surface and the interface properties because of high energy electron and ions, though a stable plasma is sustained under low pressure condition. This paper reports the generation of uniform, high-density and low-temperature microwave plasma (2.45GHz) combined with a spokewise antenna and its application to large-scaled mc-Si:H thin film formation. This discharge produces a high density of more than 1011cm-3 , and uniform density variation of less than +5% (20 cm in diameter) in Ar plasma with no magnetic fields. In addition, it produces highly crystallized and photoconductive mc-Si:H film from dichlorosilane (Si2H2Cl2), H2 and Ar mixture at deposition rate of more than 5 A/s.