Investigation on boron diffusion effects in buried oxide of Si nanocrystals (Si NCs) embedded Silicon-on-Insulator

Abstract

Si nanocrystals (Si NCs) embedded in an oxide matrix can introduce additional defects and stress, which enhances the dopant diffusion and trapping in buried oxide (BOX) layer that can be detrimental for device applications. In this paper, we have investigated the boron gettering effect of Si NCs in Silicon-on-Insulator (SOI) using Secondary Ion Mass Spectrometry (SIMS), Transmission Electron Microscopy (TEM). And image identification technique is used to analysis the Si NCs concentration in BOX. By analyzing the decline of threshold voltage and vanishing of kink effect of nMOSFET with different Si NCs concentration, it is found that the variation of boron concentration is induced by Si NCs. The higher annealing temperature and boron concentration in top Si can accelerate the boron diffusion velocity. The boron concentration rises almost tenfold in BOX layer when Si implantation dose increases from 5 × 1015 cm−2 to 5 × 1016 cm−2. The results indicate that the boron gettering effect is caused by Si NCs and highly related to the Si NCs induced defects and stress. This paper may offer a guidance for compensating the boron loss in SOI MOSFET fabricating process.