Control and monitoring of optical thin films deposition in a Matrix Distributed Electron Cyclotron Resonance reactor^*

Laboratoire de Physique des Interfaces et des Couches Minces (UMR 7647, CNRS), École Polytechnique, 91128 Palaiseau, France

Corresponding author: daineka@poly.polytechnique.fr

Received: 24 November 2003
Revised: 21 August 2004
Accepted: 24 August 2004
Published online: 23 November 2004

Abstract

A range of silicon-based optical thin films have been deposited in a matrix distributed electron cyclotron resonance (MDECR) reactor. Process parameters were optimized in order to obtain optical quality thin films at low substrate temperatures and high deposition rates without post-deposition treatment. Stoichiometric silica films have been deposited at the rates up to 70 nm/min at temperatures lower than 150 °C. Oxynitride films with a controllable refractive index ranging from 1.46 to 1.86 have been obtained from SiH₄/O₂/N₂ mixtures. Real time process control by multichannel ellipsometry has been implemented and successfully applied for the deposition of silica, silicon oxynitrides and amorphous silicon. Better than 0.3% in thickness accuracy was achieved in high rate deposition of silica layers of various predefined thickness. Refractive indices were determined in real-time with an absolute precision of 0.005–0.02. The control algorithm was used for fabrication of multilayer optical filters. The results show that the MDECR concept coupled with real-time process control by ellipsometry can be technology of choice for the deposition of interference coatings.