Study on the improved thermal stability of cobalt silicide film by using cryogenic carbon PAI

摘要

Cryogenic ion implantation process has received increasing attention because it provides better amorphization performance and less end-of-range defects. In this study, 20nm-thick CoSi film was formed on cryogenic carbon ion-implanted poly-Si substrate and the agglomeration behavior of CoSi film after high temperature RTA annealing was investigated by four-point-probe resistivity measurement. Results suggest that the thermal stability of CoSi film is greatly improved when cryogenic carbon pre-amorphization implant (PAI) with energy of 15keV and dose more than or equal to 2E15 ions/cm was performed on poly-Si substrate before CoSi formation. The suppression of agglomeration of CoSi film during 950°C RTA annealing is likely due to the homogeneous distribution of fine-grained CoSi film formed on fully amorphized poly-Si substrate. In addition, it was found that the microstructure of underlying poly-Si of stacked poly-Si substrate strongly affects the agglomeration behavior of CoSi film. The precise control of amorphization depth by adjusting carbon PAI energy can lead to improvement in CoSi thermal stability.