Fluorine barrier properties of bias-sputtered tungsten films

Fluorine diffusion barrier properties of bias-sputtered tungsten films and titanium nitride films are compared for use in interconnects in silicon int egrated circuits. Typical vertical interconnect film stacks consist of tung sten (chemical vapor deposition/diffusion barrier/titanium. Chemical vapor deposition of tungsten using tungsten hexafluorine (WF6) leads to fluorine contamination in the film stack. Tungsten films 380 nm thick were deposited on 100 nm titanium films protected by either 10 nm thick bins-sputtered tu ngsten or 10 nm thick TiN diffusion barrier films. The dose of fluorine in the titanium films protected by TiN was measured to be 3.0 (+/- 0.6) x 10(1 3) atoms/cm(2) vs. 5.0 (+/- 1.0) x 10(14) atoms/cm(2) in the titanium film protected by sputtered tungsten. We extract an upper bound for the diffusiv ity of fluorine in sputtered tungsten films to be similar to 4 x 10(-14) cm (2)/s at 410 degrees C. Variation in fluorine dose in the titanium film wit h sputtered tungsten film thickness and tungsten chemical vapor deposition conditions is discussed. The superior fluorine barrier property and lower r esistivity of sputtered tungsten films make them a good candidate to replac e titanium nitride for via applications in silicon integrated circuits. (C) 2000 The Electrochemical Society. S0013-4651(99)07-050-0. All rights reser ved.