Behaviour of Bombarded Ar at Surface and Bonded Interface of Copper

Abstract

Argon ion bombardment is known to be effective in removing all surface contaminations and oxides and improving the quality of diffusion bonds. However, recent work has shown that the accelerating voltage used during the ion bombardment significantly affected the bond strength. This work has been carried out to investigate the behaviour of argon at the surface and bonded copper interface after argon ion bombardment. To investigate changes at the surface and the bonded interface, surface composition, surface morphology, gas in voids at the interface were monitored using Auger spectroscopy, reflection high energy electron diffraction (RHEED), and mass spectroscopy. This study shows that an increase in time or accelerating voltage of ion bombardment results in much surface damage by the increase in surface roughness and crystal disorder due to the ions the penetrating the surface and displacing atoms. Argon entrapped at the surface layer diffuses into the voids at bond-line of joints which are made using specimens treated by the argon ion bombardment. The presence of argon in the voids is one reason for the deterioration of the joints, in the specimens bombarded at a high accelerating voltage. When the specimens treated by ion bombardment are heated, argon gas is released from the surface. Heat treatment of specimens treated by ion bombardment is effective in restoring the surface to its original order and producing joints free from voids at the bond-line.