Comparative analysis of thermally induced degradation of condensation-grown (1 0 0)Ge0.75Si0.25/SiO2 interfaces by electron spin resonance

Abstract

An electron spin resonance study has been carried out on the influence of isochronal annealing on the GeSi/SiO2 interfaces of the condensation grown (100)Si/SiO2/Ge0.75Si0.25/SiO2 structure. The thermal interface stability has been monitored in terms of the evolution of occurring paramagnetic interface defects, in particular, here involving the Ge dangling bond GePb1 point defect, previously identified as a detrimental interface trap. This reveals thermal post-growth interface degradation, initiating from annealing at the temperature ∼440°C onward, identified as substantial generation of GePb1 interface traps in addition to those naturally introduced into the system during sample manufacturing. In terms of GePb1 density, the interface thus appears only robust for thermal treatment in vacuum up to 440°C. For Tan reaching ∼520°C, a drastic degradation occurs as exposed by an about two-fold increase in GePb1 density, which state is maintained up to Tan∼900°C. Annealing in H2 (∼1atm) has a similar effect, except that the interface degrades more gradually. Above 900°C, the structure's integrity gradually collapses because of disintegration (Ge escape) of the SiGe layer. As to device implementation, the data indicate that temperatures of processing steps in O-deficient ambient should be kept below ∼440°C.