Recrystallization and oxidation - competing processes during PECVD ultrathin silicon layer high temperature annealing

In this work we have studied relations between three competing effects that take place during high temperature annealing of PECVD ultrathin silicon layer, namely: amorphous silicon recrystallization, amorphous silicon oxidation and oxidation of just received crystalline silicon in the first few minutes of this process. Understanding very complex relations between these kinetics is essential to allow for conscious manipulating of annealing and/or oxidation parameters in order to achieve different results, depending on the application in mind. The presented below results are, to our knowledge, the first attempt to address these issues.

I. Introduction

Depending on application, different requirements on physical structure and properties of silicon ultrathin layer in double oxide barrier structure can be given. The most intriguing case is possibility of obtaining silicon nano-crystals (nanodots) in the dielectric (oxide) matrix, which can be achieved by very careful recrystallization and oxidation processes [e.g. [1] – [7]]. As both of these processes require high temperature, they can take place at the same time, simultaneously, providing appropriate conditions are satisfied. The main difference between the conditions needed for them is presence of oxygen which obviously is required for oxidation process. It has to be realized that oxygen free conditions are very difficult to achieve. Hence, even in neutral gas annealing case this process can be expected. This work is supposed to provide grounds for practical use of annealing and/or oxidation of PECVD ultrathin silicon layers to fabricate different nanoelectronic and nanophotonic devices.