Abstract
We evaluated plasma enhanced chemical vapor deposited (PECVD) W/sub x/N as a potential copper barrier. Ultrathin (100 /spl Aring/) PECVD W/sub x/N films with N/W stoichiometry ranging from 0.2 to 1.0 and resistivities between 200-1000 /spl mu//spl Omega/-cm were deposited utilizing WF/sub 6/-N/sub 2/-H/sub 2/ chemistry. The thermal stability of the films as a Cu barrier was evaluated by annealing the Si-W/sub x/N-Cu stacks at temperatures up to 700/spl deg/C. Barrier failure was detected by sheet resistance measurements and surface SIMS. The thermal stability was correlated with N/W ratio and fluorine content as determined by RBS and temperature programmed desorption mass spectroscopy, respectively. Tests showed that films with N/W ratios between 0.3 and 0.4 were stable up to 690/spl deg/C, while incorporated fluorine was seen to have a detrimental effect on barrier stability. Film conformality was optimized using design of experiments techniques. The highest step coverage was obtained at low deposition temperature, low N/sub 2/ flow and high H/sub 2/ flow.
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