Room temperature oxidation of Cu/Si0.76Ge0.24 annealed at 200 to 300 degrees C

Abstract

The Cu3Si-catalyzed oxidation behavior of Cu/Si0.76Ge0.24 after annealing at a temperature of 200-300 degrees C was studied using transmission electron microscopy (TEM). For the Cu/Si0.76Ge0.24 samples annealed at 200 degrees C and followed by exposure in air for 1-4 weeks an SiO2 layer embedded with precipitates containing Cu, Ge, Si, and O was formed on the surface of the Cu-3(Si1-xGex) film. During exposure the Cu atoms released from Cu-3(Si1-xGex) by oxidation diffused down to the residual Si0.76Ge0.24 film and subsequently the Si substrate to form. new Cu-3(Si1-xGex) and Cu3Si, respectively. After exposure for 5-6 weeks not only the oxidation of the surface layer became severe but also the growth of the buried SiO2 layer was initiated at the Cu-3(Si1-xGex)/Cu3Si interface. Concurrently, the Cu3Si-catalyzed oxidation of Si by inward movement of the SiO2/Si interface was also observed. As compared with the annealed Cu/Si samples the presence of Ge significantly lowered the oxidation rate of the annealed Cu/Si0.76Ge0.24 samples. Higher temperature annealing promoted the oxidation rate because of Ge segregation out of the Cu-3(Si1-xGex) layer and the formation of a larger fraction of the Cu-3(Si1-xGex)/Cu3Si interface where the buried SiO2 layer was initially formed. (C) 1999 Elsevier Science S.A. All rights reserved.