SIH4-WF6 GAS-PHASE NUCLEATED TUNGSTEN AS AN ADHESION LAYER IN BLANKETCHEMICAL-VAPOR-DEPOSITION FOR ULTRALARGE SCALE INTEGRATION

In this work, the thin tungsten film nucleated by an in situ SiH4-WF6 gas-phase reaction in the low pressure regime (100 mTorr) was investig ated and used as an adhesion layer to replace TiN in a blanket chemica l vapor deposition of tungsten (CVD-W) process. The deposition rate, s tep coverage, and film resistivity were studied as a function of the p rocess parameters. Deposition rates from 360 to over 3000 nm/min were observed and increased with increasing deposition pressure and tempera ture. Moreover, we found that the deposition rate fell to zero when th e temperature was less than 150 degrees C. Also. the gas-phase reactio n vanished when the SiH4/WF6 flow ratio was smaller than 1.6. On the o ther hand, the step coverage decreased with increasing deposition rate . Finally the tungsten film resistivity was 167 mu Omega-cm which was comparable to that of a sputtered TiN film (about 150 mu Omega-cm) and also exhibited good adhesion ability on oxide when the temperature wa s higher than 200 degrees C. Overall, the results indicate that this i n situ gas-phase nucleated tungsten film is an attractive replacement for TiN film in the blanket CVD-W technique because of reduced process complexity excellent step coverage, and low resistivity.