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

The improved thermal stability of cobalt silicide (CoSi <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{2}}$</tex-math> </inline-formula> ) becomes pivotal with the introduction of a 4F <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text{2}}$</tex-math> </inline-formula> 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 CoSi <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{2}}$</tex-math> </inline-formula> , 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 CoSi <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{2}}$</tex-math> </inline-formula> approximately 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> C and significantly enhances the morphology and thermal stability of CoSi <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{2}}$</tex-math> </inline-formula> for PVD Co. These observed effects can be explained by the segregation of carbon atoms at the grain boundaries and CoSi <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{2}}$</tex-math> </inline-formula> /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 CoSi <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text{2}}$</tex-math> </inline-formula> s in the context of future DRAM devices.