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

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 CoSi₂ film was formed on cryogenic carbon ion-implanted poly-Si substrate and the agglomeration behavior of CoSi₂ film after high temperature RTA annealing was investigated by four-point-probe resistivity measurement. Results suggest that the thermal stability of CoSi₂ film is greatly improved when cryogenic carbon pre-amorphization implant (PAI) with energy of 15keV and dose more than or equal to 2E15 ions/cm² was performed on poly-Si substrate before CoSi₂ formation. The suppression of agglomeration of CoSi₂ film during 950°C RTA annealing is likely due to the homogeneous distribution of fine-grained CoSi₂ 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 CoSi₂ film. The precise control of amorphization depth by adjusting carbon PAI energy can lead to improvement in CoSi₂ thermal stability.