Very-low-pressure deposition by electron cyclotron resonance plasma chemical vapor deposition method

Abstract

This paper presents the deposition characteristics of the electron cyclotron resonance plasma chemical vapor deposition from the viewpoint of very-low-pressure operation, taking an instance of the deposition of amorphous boron films from diborane and hydrogen mixtures. The films were deposited at very low pressures, e.g., 0.1 Pa, and at low substrate temperatures below 600 °C. This very-low-pressure deposition is made possible by virtue of radicals produced by the discharge. Deposition characteristics have been studied by observing the dependence of the deposition rate on various parameters of the preparation. As a result, this deposition is characterized by a heterogeneous reaction with respect to predominant collisions of radicals and characterized by a mass-transfer controlled reaction with respect to rate-controlling factors. The feature of very-low-pressure deposition, however, modifies the mass-transfer controlled reaction with respect to the pressure range at which the reaction holds and with respect to the pressure dependence of the deposition rate. This modification can be explained in terms of lowering the efficiency of the mass transport onto the substrate at very low pressures.