Ultrathin oxynitride films for CMOS technology

Abstract

In this work, a review of possible methods of oxynitride film formation will be given. These are different combinations of methods applying high-temperature oxidation and nitridation, as well as ion implantation and deposition techniques. The layers obtained using these methods differ, among other aspects in: nitrogen content, its profile across the ultrathin layer, ... etc., which have considerable impact on device properties, such as leakage current, channel mobility, device stability and its reliability. Unlike high-temperature processes, which (understood as a single process step) usually do not allow the control of the nitrogen content at the silicon-oxynitride layer interface, different types of deposition techniques allow certain freedom in this respect. However, deposition techniques have been believed for many years not to be suitable for such a responsible task as the formation of gate dielectrics in MOS devices. Nowadays, this belief seems unjustified. On the contrary, these methods often allow the formation of the layers not only with a uniquely high content of nitrogen but also a very unusual nitrogen profile, both at exceptionally low temperatures. This advantage is invaluable in the times of tight restrictions imposed on the thermal budget (especially for high performance devices). Certain specific features of these methods also allow unique solutions in certain technologies (leading to simplifications of the manufacturing process and/or higher performance and reliability), such as dual gate technology for system-on-chip (SOC) manufacturing.

Keywords

• MOS technology
• gate stack,
• ultrathin oxynitride layers
• high temperature processing
• plasma processing