THE EFFECTS OF SCREEN OXIDE AND LOW-TEMPERATURE BPSG ANNEAL ON TITANIUM SALICIDE FORMATION

In this paper, we report extensive study of Ti-salicide performed to m eet the requirements of deep submicron devices such as high temperatur e stability, low resistivity, junction leakage current, and compatibil ity with current processing steps. We have found that oxygen induced l ocal agglomeration of Ti-salicide causes degradation of sheet resistan ce and leakage current under high temperature annealing. We have exami ned the nucleation and growth of Ti-salicide on polysilicon and active region with and without screen oxide. We found that sample without sc reen oxide shows uniform morphology al the polysilicon and silicon sur face. The local agglomeration of Ti-salicide can be explained by oxyge n knock-in effect. It is known that oxygen can be incorporated during lightly doped drain (LDD) ion implantation. Due to this oxygen, the el ectrical characteristics of Ti-salicide are significantly degraded. Co mpared with control sample, sheet resistance and junction leakage of T i-salicide junction with screen oxide are significantly higher. This b ehavior can be explained by local agglomeration induced Shottky juncti on behavior. (C) 1997 Elsevier Science S.A.