EFFECT OF THE PHASE-TRANSITION OF TI SILICIDE ON THE THERMAL-STABILITY OF SI-INTERFACE IN THE CU CUTI2/TI/SI CONTACT SYSTEM/

In an attempt to realize a stable Cu metallization in Si-LSI, a Cu/CuT i2/Ti/Si contact system was prepared and its thermal stability was stu died. As a result, although the phase transition from the intermediate CuTi2 phase to the CuTi phase was observed with increasing annealing temperature in the contact system, the interface between the metalliza tion layers (Cu and CuTi) and Si in the system suppressed the excess d iffusion of Si at temperatures up to 570 degrees C. The reason is that the Ti silicide formed at the Si interface acts as an Si diffusion ba rrier until its chemical state transforms into TiSi2, which is the fin al phase of Ti silicide. However, the contact system failed due to a d irect chemical reaction between Ti and/or Cu in CuTi and Si which diff used into the upper layer through TiSi2 when Ti silicide at Ti/Si inte rface formed TiSi2 at 600 degrees C. Then the contact system resulted in the phase-separated bilayer structure of silicide. It was revealed from these results with the thermal stability of this contact system i s related closely to the phase transition of the Ti silicide layer at the Si interface with increasing annealing temperature.