Tuning of SiO2/Si interface by a hybrid plasma process combining oxidation and atom-migration

Abstract

As a common oxide-semiconductor interface, SiO2/Si plays an important role in silicon-based electronics and optoelectronics. In order to effectively obtain an ultra-smooth and thin SiO2/Si interface, a hybrid tuning process based on inductively coupled plasma (ICP) was proposed, which combined oxidation (plasma-OX) and atom-migration manufacturing (plasma-AMM). In plasma-OX process, a thick oxide film was rapidly prepared on Si wafer surface in 2 min, which included a SiO2 layer on the top and a SiOx (x < 2) layer between the top layer and the bulk crystalline silicon (c-Si). In subsequent plasma-AMM process, ICP steadily delivered energy to the Si wafer surface and induced the migration of unsaturated Si from SiOx layer to c-Si, which enhanced the crystallization of silicon wafer. The roughness of SiO2/Si interface was reduced to Sa 0.171 nm at 620 W in 5 min. However, a 2–3 nm thickness SiOx layer still existed, and several defects causing by residual thermal stress can be observed. Further optimizing plasma-AMM process by setting multi-step slow cooling, the SiOx layer can be almost completely decomposed. The interface roughness Sa was reduced to <0.1 nm and the interface thickness was reduced to 1–2 atom layer. Both OX and AMM process were conducted in the same setup, which is convenient for switching. This study proposed and demonstrated the feasibility of a hybrid plasma tuning process, which provided an efficient tuning technology at atomic level for semiconductor interface.