Atmospheric pressure chemical vapor deposition of blanket tungsten films on silicon substrates for integrated circuit applications

Abstract

Atmospheric pressure chemical vapor deposition (APCVD) of tungsten films using WF6/H2 chemistry has been studied. A statistical design of experiments approach and a surface response methodology were used to determine the most important process parameters and to obtain the best quality film possible in the parameter range studied. It was found that the deposition rate depends strongly on WF6 flow rate, temperature, and the interaction between hydrogen flow rate and temperature. The resistivity was found to have a strong dependence on WF6 and H2 flow rates and temperature. An activation energy of 0.4 eV was calculated for the reaction rate limited growth regime. Empirical equations for predicting the deposition rate and resistivity were obtained. The resistivity decreases with both increasing film thickness and grain size. The films grown in the studied process parameter range indicate that (110) is the preferred orientation for films deposited with low WF6/H2 flow rate ratios at all deposition temperatures (350–450°C), whereas, the (222) orientation dominates at high WF6/H2 flow ratios and high deposition temperatures. Also, the grain size is larger for (222) oriented films than for (110) oriented films. The results of this study suggest that high-quality, thin film tungsten can be deposited using APCVD.