Introduction

The bombardment of a growing film with energetic ions has been observed to produce improvements in a number of properties of thin films and coatings such as enhanced adhesion, densification of films grown at low substrate temperatures, modification of residual stresses in the films, change in texture (orientation) of the film and disruption of columnar grain structures. The earliest systematic studies of these effects are found in the work of Mattox (1) in the early 60's. Today a wide variety of thin film deposition and coating processes such as biased sputtering, activated reactive evaporation, ion plating, cathodic arc deposition, plasma assisted chemical vapor deposition and ion-beam assisted deposition all make use of energetic ions to enhance the properties of the deposited films (2). In spite of the widespread interest in this approach, the understanding of the physical processes producing these beneficial effects is rather poorly understood.

The U.S. Naval Research Laboratory has undertaken a program to identify and characterize the major processes occurring during ion-beam assisted deposition (IAD) so they may be used more effectively in all deposition processes. The IAD process consists of a vapor flux produced by evaporation or sputtering, a flux of energetic ions produced by an ion gun and in some cases a reactive atmosphere. Ion-beam assisted deposition was selected for study because of the ability to independently control the major process variables — vapor flux, ion flux, and their relative, rates; ion energy, substrate temperature and the pressure (and purity) of the atmosphere.

0 0

Post a comment