Reaction mechanism discrimination using experimental film profiles in features

Film profiles in features on patterned substrates are employed as a tool to test proposed reaction mechanisms for low pressure chemical vapor deposition processes. Simulated film profiles in long trenches generated using EVOLVE, a physically based deposition process simulator, are compared to experimental film profiles to determine whether a particular mechanism or rate form should be rejected. We consider two examples: (1) silicon dioxide deposition from tetraethoxysilane (TEOS), and (2) tungsten deposition from hydrogen reduction of tungsten hexafluoride. Of three proposed mechanisms for the deposition of silicon dioxide from TEOS, we find that the mechanism in which TEOS undergoes heterogeneous decomposition with inhibition by a strongly adsorbing byproduct provides the best fit to the experimental profiles. In the second example, we demonstrate that a mechanism that assumes a single rate limiting step is apparently not valid for tungsten depositions involving features that close. A semi-empirical rate expression is presented which can be used to simulate depositions up to and beyond feature closure.