INFLUENCE OF CONTACT TREATMENTS ON THE ELECTRICAL CHARACTERISTICS OF SHALLOW-JUNCTION TITANIUM-BASED CONTACTS

Abstract

A comparison of the electrical characteristics of Al-Si/TiW/TiSi2/Si, Al-Si/TiW/Ti/Si and Al-Si/Si contact structures has been carried out. The influence of a contact implantation and anneal on the electrical characteristics of the TiSi2 contacted shallow junctions has also been investigated. Compared with the Al-Si/TiW/TiSi2/Si contact system, the Al-Si/TiW/Ti/Si contact was shown to be a more suitable metalization scheme for the shallow junction contact technology, due to its lower contact resistance and junction leakage as well as its simplicity of fabrication process. The contact resistance of the Ti/n+-Si system was found to be lower than that of the TiSi2/n+-Si system. The low contact resistance of Ti/n+-Si is attributed to the presence of a uniform amorphous interlayer as well as significantly less influence of As on Ti/a-alloy/n+-Si compared to TiSi2/n+-Si. A contact anneal was found to reduce contact resistance for both TiSi2/n+-Si and TiSi2/p+-Si contact systems. With an additional P+ implantation and anneal, the contact resistances are drastically reduced for the n+-Si contacts. On the other hand, a B+ contact implantation and anneal did not significantly improve the contact performance of the TiSi2/p+-S system. The difference is thought to arise from the lower degree of recovery of B+ implantation damage resulted from the contact implantation of TiSi2/p+-Si contact compared to that of TiSi2/n+-Si contact. The addition of the contact P+ implantation increased the total dopant concentration underneath the surface to such an extent that it leads to a reduction in contact resistance.