AVS 47th International Symposium
    Semiconductors Wednesday Sessions
       Session SC+EL+SS-WeM

Paper SC+EL+SS-WeM5
Etching of Polymer-like a-Si:H Films by Impact of H

Wednesday, October 4, 2000, 9:40 am, Room 306

Session: Passivation and Etching of Semiconductors
Presenter: T. Zecho, Universitaet Bayreuth, Germany
Authors: T. Zecho, Universitaet Bayreuth, Germany
B. Brandner, Universitaet Bayreuth, Germany
J. Biener, Max-Planck-Institut fuer Plasmaphysik (EURATOM Association), Germany
J. Kueppers, Max-Planck-Institut fuer Plasmaphysik (EURATOM Association), Germany
Correspondent: Click to Email
Etching of a-Si:H thin films with H atoms is a well known phenomenon from earlier studies. Nevertheless, the product distribution and the temperature dependence of the absolute etching rate could not be unambiguously determined. The present study was performed in order to quantify the etching rate by direct detection of the etching products during H admission and to determine to what extent higher silane species contribute to the etching process. A-Si:H films in a thickness range ca 1 to 100 nm were deposited at 300 K by ion-beam-deposition on a Pt(111) substrate and characterised by AES, TPD, HREELS and ELS. The films grow in a two-dimensional fashion and show a polymer like structure with a hydrogen content of about 40 %. The thermal stability of the films is limited by the formation of a Pt silicide commencing ab about 500 K which proceeds at the a-Si:H/Pt interface. In accordance with the exothermic formation of volatile silanes a constant etching rate of about 1 % between 100 K and 300 K was found with about equal contributions from the silane and higher silanes channels. In this temperature range even minor impurities lead to a decrease of the etching rate. From 300 K to 500 K the etching rate decreased roughly linear to 0.1 % due to the growing thermal instability of the higher silanes. Therefore at 500 K silane was the only detected etching product. The formation of both silane and higher silanes proceeds via a direct interaction of atomic hydrogen and the corresponding precursor species.