Phosphorus Profile Control in Ge by Si Delta Layers

Abstract

The impact of Si spike layer on phosphorus diffusion in germanium is investigated. Ge cap/in-situ P-doped Ge/Ge buffer is deposited and post-annealed using PRCVD tool. In the case of samples without Si spikes, P diffusion/segregation and desorption from the Ge surface happened during Ge cap layer deposition at 550C resulting in dopant dose reduction and profile broadening. By interposing P-doped Ge by Si spikes, P diffusion is suppressed. The diffused P is piled-up at the position of the Si spikes. The P diffusion suppression effect by the Si spike is observed after postannealing even at 650C. XRD-RSM shows that the Si spike is pseudomorphic to Ge lattice. After postannealing, Si diffusion is observed but no Ge crystal degradation was evident. Enhanced Si diffusion is observed by presence of P. Based on these results, the P diffusion suppression seems to be caused by the replacement of substitutional Si by diffused P.