Epitaxial growth of heavily B-doped SiGe films and interfacial reaction of Ti/B-doped SiGe bilayer structure using rapid thermal processing

Abstract

The low-temperature epitaxy of heavily B-doped Si1−xGex films has been carried out by rapid thermal chemical vapor deposition (RTCVD) using Si2H6, GeH4 and B2H6 in an H2 carrier gas. The B concentration in the films increases proportionally with increasing B2H6 partial pressure. Moreover, a high doping level of 3.6×1021 cm−3 was achieved at a growth temperature of 500°C. In the case of x=0.25, the strain within the deposited films measured by double crystal X-ray diffraction (XRD) decreases with increasing B content, which can be directly related to the decrease of the lattice constant by B incorporation to the substitutional lattice site. The substitutional B concentration estimated from the strain appears to be saturated at about 5×1020 cm−3. Furthermore, the interfacial reaction of a Ti/B-doped SiGe bilayer structure by rapid thermal annealing (RTA) and B redistribution around the Ti germanosilicide layer have been examined. It was found that, after RTA, a pileup of B atoms occurs at the C54-Ti(SiGe)2/Si interface and an abruptness of the C54-Ti(SiGe)2/Si interface for the Ti/B-doped SiGe is superior to that for the Ti/undoped SiGe. These results indicate that segregated B atoms at the interface cause a suppression of interfacial reaction of Ti/SiGe, which leads to an abrupt C54-Ti(SiGe)2/Si interface.