Sputtered aluminum film on copper substrate: Investigation on the growth kinetics, intrinsic stress, and interfacial bonding

Abstract

For modest applications in electronic devices where copper and aluminum are the metals of choice, the problem of providing thermal barrier coating (TBC) on metallic Al or Cu substrate is presently addressed in this investigation. Using copper substrates, this study aims to explore the feasibility of depositing ceramic-TBC using sputtering, an old but hitherto untested method in such an application where the usual processing methods are thermal spray, powder processing, chemical vapor deposition, and combustion synthesis. With the final objective of growing ceramic layer on metallic substrate in mind, this paper reports the results of a preliminary investigation involving the growth of aluminum films on copper substrates: its interface bonding, surface, and intrinsic stresses.
Experimental data show that films grown at 300-500°C exhibit the best (almost crack-free) surfaces, least stresses, and good interfacial bonding. These films stand the least amount of risk of spallation during thermal cycling, making them the best base layer for the subsequent growth of a thermal barrier coat which is a ceramic material, in this case alumina.