Diagnostic Study of VHF Plasma and Deposition of Hydrogenated Amorphous Silicon Films

Abstract
The role of the excitation frequency in processing plasma is investigated through comparative experiments of VHF and RF plasma by means of plasma diagnostics and deposition charaterisitcs of a-Si:H films. Electron temperature, electron density and the shape of the tail of the electron energy distribution function (EEDF) are evaluated from the Langmuir probe measurement. EEDF is also discussed based on optical emission spectra measured by He, H2SiH4plasma. The frequency effect is explained in terms of the effect of ω/ν on EEDF. Structural and electrical properties of a-Si:H films deposited both by VHF and RF plasma are also investigated. The favorable condition for obtaining device-quality a-Si:H films is discussed in connection with the plasma structure.