Growth and characterization of hydrogenated amorphous silicon prepared using a combined hot wire and electron cyclotron resonance plasma deposition technique

Abstract

Hot Wire Chemical Vapor Deposition (HWCVD) is an emerging technology in semiconductor materials thin film deposition due to the high growth rates and reasonable electronic properties attainable using this method. To improve the electronic characteristics of material grown by the HWCVD method, neutral ion bombardment during growth was introduced as it is shown to be beneficial in Plasma Enhanced Chemical Vapor Deposition (PECVD). Neutral ion bombardment was accomplished by using remote Electron Cyclotron Resonance (ECR) plasma and the entire deposition technique is termed ECR-HWCVD. The ECR-HWCVD films were compared to HWCVD materials deposited without ion bombardment grown at similar conditions in the same reactor using a 10.5 cm filament to substrate distance to minimize substrate heating by radiation during deposition. The growth rate is halved when ion bombardment is added to HWCVD, however it remains four times greater than the highest quality ECR-PECVD films. Also, ECR-HWCVD material exhibited better electronic properties as shown by Urbach energy, photosensitivity, hydrogen content, microstructure parameters, and space charge limited current defect measurements. In addition, the effect of substrate temperature on hydrogen content and material microstructure was investigated. Both hydrogen content and the microstructure parameter R decreased as substrate temperature increased; and when ion bombardment was added to the deposition conditions, the microstructure parameter decreased regardless of substrate temperature.