Formation of ultrathin silicon layers by PECVD and their modification for nanoelectronic and nanophotonic applications

Abstract

Nanoelectronic and nanophotonic applications have created a pressure on methods of fabrication double dielectric barriers stacks with ultrathin silicon layer located between dielectric layers. Among numerous possible methods, PECVD seems to be very promising. In order to increase possible number of applications, however, the ability to transform continuous silicon layer into nanocrystalline form in dielectric matrix is required. The work described below reports on experimental efforts to form such a structure by controlled high temperature recrystallization and oxidation of ultrathin PECVD silicon layer in the stack. The effects if high temperature annealing has been studied by spectroscopic ellipsometry. The applied model allowed for identification of composition and structural changes within the silicon PECVD layer due to different high temperature annealing processes applied. As a result of this study, it has been proved that it is feasible to fabricate complete two barrier stack consisting of ultrathin dielectric and silicon layers in one PECVD system without exposing samples to the ambient atmosphere. In order to reduce the PECVD silicon layer thickness to approximately 3 nm, we proposed using plasma oxidation in PECVD instead of PECVD oxide deposition. High temperature (especially in 1100°C) annealing in argon proved to allow formation of silicon nanocrystals in oxide matrix. Other effects resulting from high temperature annealing of fabricated stacks are also studied.