Improving Gate Oxide Integrity of Cobalt Silicided P-Type Polysilicon Gate Using Arsenic Implantation

The gate oxide integrity degradation due to the thermal instability of cobalt silicide ( CoSi2) in p-type polysilicon gate metal-oxide-semiconductor (MOS) capacitors is alleviated by arsenic implantation into p-type poly-Si gate. The thin gate oxides of p+-poly MOSFETs were severely degraded due to agglomeration of cobalt silicide at high temperature after silicidation. The degradation of thin gate oxide was found to be suppressed by the implantion of arsenic into p-type polysilicon gate. This is due to the fact that arsenic atoms segregate simultaneously into grain boundary and interface, and diffusion of decomposed cobalt along grain boundary was then retarded during agglomeration.