Phosphorus Profile Control in Ge by Si Delta Layers

摘要

germanium (Ge) is investigated. A Ge cap / in-situ P-doped Ge /Ge buffer layer stack is deposited and post-annealed using a singlewafer reduced pressure chemical vapor deposition (RPCVD) tool.The P doping level in Ge is ～5×10~(19) cm~(-3). In the case of sampleswithout Si delta layer, P diffusion / segregation and desorptionfrom the Ge surface happened during Ge cap layer deposition at550°C resulting in dopant dose reduction and profile broadening.By interposing the P-doped Ge layer by Si delta layers, the Pdiffusion is suppressed. The diffused P is piled-up at the positionof the Si delta layers. The P diffusion suppression effect by the Sidelta layer is observed after postannealing even at 650°C. Thiseffect is pronounced by increasing the Si dose. XRD-reciprocalspace mapping shows that the Si delta layer is pseudomorphic tothe Ge lattice, indicating that the Si atoms are on lattice site. Afterpostannealing, Si diffusion is observed but no Ge crystaldegradation was evident. Enhanced Si diffusion is observed bypresence of P. Based on these results, the P diffusion suppressionseems to be caused by the replacement of substitutional Si bydiffused P.