(100)GERMANIUM Silicon Layers Produced by Heated Ion Implantation.

The possibility of producing high crystalline quality germanium silicon layers by heated ion implantation of silicon <100> was investigated. An understanding of the implantation damage evolution with increasing germanium fluence was first developed. The damage in the implanted layers was characterized using proton and doubly ionized helium channeling spectrometry. For room temperature implants, an amorphous layer is formed at a fluence of about 1 times 10^{14} cm ^{-2}, while for heated implants, dynamic annealing balances the damage production and prevents the formation of an amorphous layer except at the very surface of the implant. The residual damage production rate at the surface was found to depend on the pre-existing residual disorder. Variations of the implant temperature (300^circC, 380^ circC), dose rate (1 muA/cm2,.2 muA/cm2), and energy (40 keV, 60 keV) did not modify significantly the evolution of the residual damage with fluence. After a 10 minute, 1010^circ C annealing, the crystalline quality of the germanium silicon layers was investigated by doubly ionized Rutherford Backscattering Spectrometry (RBS) and by proton and doubly ionized helium channeling spectrometry. For room temperature implants, layers with peak concentrations up to 7% showed a good crystalline quality while the high concentration layer (16% peak concentration) showed significant residual damage. The final quality of the < 100> heated implants was consistently and substantially lower than that of the room temperature implants. Varying the implant temperature, dose rate and energy did not produce significant improvements, nor did a modification of the annealing schedule (two 10 minutes steps at 850^circC and 1010^circC). The fact that the room temperature implants produced consistently better final quality layers than the heated implants for <100> substrates is in contrast with the results obtained for <111> substrates. A possible explanation based on the hypothesis that a localized thermal process drives the damage evolution is developed. Finally, to potentially produce defect free thinner layers with a higher germanium concentration, the recommendation is made to concentrate further research efforts on low energy implants.