A STUDY ON THE THERMODYNAMICS AND KINETICS OF TUNGSTEN DEPOSITION BY WF6 AND GeH4

Abstract

In this paper a thermodynamic and kinetic study of the new deposition process of tungsten on Silicon (100) from tungsten hexafluoride (WF6) and germane (GeH4) is presented. Thermodynamic calculations as well as experiments show, that the reaction occurring during deposition is : [MATH] The growth rate as a function of process parameters is obtained for selective depositions in the temperature range from 600 to 800 K, and a total pressure range from 150 to 1000 mTorr. Experiments show that the germane reduction of tungsten hexafluoride is 0.9 order in WF6, - 0.2 order in GeH4 and zero order in H2. The activation energy is 34 kJ/mol. These kinetic data of the GeH4/WF6 process differ markedly from the kinetics of the recently much studied SiH4/WF6 process. A fascinating observation is that the deposition rate does not change when SiH4 is added to the GeH4/WF6 mixture, while, on the contrary, a small amount of GeH4 reduces the growth rate from a SiH4/WF6 mixture considerably. The kinetic differences between the at first sight similar GeH4/WF6 and SiH4/WF6 process are used to get a better insight in both processes.