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

Abstract

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