Effect of Carbon on the Formation of Cobalt Silicide and Thermal Stability for DRAM Application: A Comparative Study on PVD and CVD Methods

Abstract

The improved thermal stability of cobalt silicide (CoSi2) becomes pivotal with the introduction of a 4F2 cell architecture, featuring a vertical pillar transistor for DRAM application. To tackle this challenge, carbon preamorphization implantation (C PAI) was employed. This study systematically investigates the effects of C PAI on both the formation and thermal stability of CoSi2, taking into account distinct cobalt deposition methods, namely, physical vapor deposition (PVD) and chemical vapor deposition (CVD). Results demonstrate that the presence of carbon delays the nucleation temperature of CoSi2 approximately 50 °C and significantly enhances the morphology and thermal stability of CoSi2 for PVD Co. These observed effects can be explained by the segregation of carbon atoms at the grain boundaries and CoSi2/Si interface. However, the introduction of carbon has a detrimental effect for CVD Co. The variations in results are attributed to variations in the deposition mechanism. This insight provides valuable considerations for optimizing the thermal stability of CoSi2s in the context of future DRAM devices.