Improving the electrical integrity of Cu-CoSi/sub 2/ contacted n/sup +/p junction diodes using nitrogen-incorporated Ta films as a diffusion barrier

The study on improving the electrical integrity of Cu-CoSi/sub 2/ contacted-junction diodes by using the reactively sputtered TaN/sub x/ as a diffusion barrier is presented in this paper. In this study, the Cu (300 nm)-CoSi/sub 2/ (50 nm)/n/sup +/p junction diodes were intact with respect to metallurgical reaction up to a 350/spl deg/C thermal annealing while the electrical characteristics started to degrade after annealing at 300/spl deg/C in N/sub 2/ ambient for 30 min. With the addition of a 50-nm-thick TaN/sub x/ diffusion barrier between Cu and CoSi/sub 2/, the junction diodes were able to sustain annealing up to 600/spl deg/C without losing the basic integrity of the device characteristics, and no metallurgical reaction could be observed even after a 750/spl deg/C annealing in a furnace. In addition, the structure of TaN/sub x/ layers deposited on CoSi/sub 2/ at various nitrogen flow rates has been investigated. The TaN/sub x/ film with small grain sizes deposited at nitrogen flow ratios exceeding 10% shows better barrier capability against Cu diffusion than the others.