Ion Kinetics in Silane Plasmas
Abstract
The Kinetics of ion formation by electron impact and subsequent reaction in silane: noble-gas mixtures have been examined using pulsed ion cyclotron resonance (ICR) mass spectrometry with the objective of discerning the role played by ions in plasma reactors which deposit amorphous silicon films. Cross sections for ionization of the noble-gases and silane as well as dissociative attachment of electrons to silane are presented. The nascent ion species distribution formed by electron- impact in a plasma environment changes with time as a result of charge transfer reactions. Room-temperature rate constants for these reactions have been measured with the pulsed ICR techniques, and anomalous trend in reactivity down the eighth period has been identified. The general departure from the Langevin limiting rate for ion-molecule reactions is examined with ab initio electronic structure calculations and model is advanced which probes quantum mechanical constraints on electron transfer from silane to the noble cations. The model offers a consistent rationalization for the observed rate constants and product distributions and permits analysis of experimentally inaccessible processes such as ion-radical reactions: Parametric variation of the homogeneous ion kinetics with gas mixture, pressure, and excitation variation are explored for conditions typical of commercial deposition reactors.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 20, 1988
- Accession Number
- ADA200465
Entities
People
- Pete Haaland
Organizations
- Wright Laboratory