Silicon Carbide Wafer Bonding

Abstract

p-sic layers produced on Si substrates by rapid thermal chemical vapor deposition have been transferred onto oxidized Si substrates by bonding and etchback. For SiC films with a mean surface roughness of about 20 A, room temperature bonding to smooth oxidized Si wafers is possible under the influence of an external force. For 4 in. diam substrates, bonding of —85% of the area was obtained. Sections of the SiC/Si layer of the bonded pair peeled off when the Si substrate of the SiC layer is thinned down to -450 pin and below. This is probably caused by the low interface fracture energy due to trapped air at the bonding interface and by outgassing from the thermal oxide of SiC in addition to the film stress. Multistep annealing at 1100°C between KOH etches of the Si substrate can enhance the interface fracture energy of the bonded pairs. A densification step of the SiC thermal oxide after dry oxidation helps to reduce the trapped gas in the oxide. Auger and transmission electron microscopy results have verified that the transferred SiC layer retains its original properties. © 1994, The Electrochemical Society, Inc. All rights reserved.