ATMOSPHERIC-PRESSURE CHEMICAL-VAPOR-DEPOSITION OF BLANKET TUNGSTEN FILMS ON SILICON SUBSTRATES FOR INTEGRATED-CIRCUIT APPLICATIONS

Atmospheric pressure chemical vapor deposition (APCVD) of tungsten fil ms using WF6/H-2 chemistry has been studied. A statistical design of e xperiments approach and a surface response methodology were used to de termine the most important process parameters and to obtain the best q uality film possible in the parameter range studied. It was found that the deposition rate depends strongly on WF6 flow rate, temperature, a nd the interaction between hydrogen flow rate and temperature. The res istivity was found to have a strong dependence on WF6 and H-2 flow rat es and temperature. An activation energy of 0.4 eV was calculated for the reaction rate limited growth regime. Empirical equations for predi cting the deposition rate and resistivity were obtained. The resistivi ty decreases with both increasing film thickness and grain size. The f ilms grown in the studied process parameter range indicate that (110) is the preferred orientation for films deposited with low WF6/H-2 flow rate ratios at all deposition temperatures (350-450 degrees C), where as, the (222) orientation dominates at high WF6/H-2 flow ratios and hi gh deposition temperatures. Also, the grain size is larger for (222) o riented films than for (110) oriented films. The results of this study suggest that high-quality, thin film tungsten can be deposited using APCVD.