in the Water Recycling module
The Chemical Reaction module facilitates analysis and control of your simulated thin film deposition process. In this module we concentrate on a specific chemical vapor deposition (CVD) reaction, described by the reaction SiH4 (g) ==> Si (s) + 2H2 (g), such that the input reactant silane (SiH4) produces elemental (polycrystalline) silicon (Si) film growth on the wafer, along with release of a gaseous H2 product. Clearly, the reaction is indicated by depletion of SiH4, production of H2, and deposition of Si.
For a chemical process like low pressure chemical vapor deposition (CVD), film growth requires two components, the presence of the appropriate reactive gases and the appropriate growth temperature. Capability to achieve both conditions has already been established in previous Gas Flow and Heat Transfer modules: the SiH4 inlet system provides the reactant species needed, while the various provisions for wafer heating enable the requisite wafer temperature needed for CVD film growth. In both cases, it is your setting and adjustment of equipment controls which determines the time-dependent behavior of the SiH4 partial pressure and the wafer temperature, as the exercises and your free exploration will demonstrate. Processes are complex in part because of this dynamics, namely that there are no direct, real-time adjustments of the critical process parameters, but rather only their changes in time following changes in equipment settings.
A chemical reaction panel is provided to display key parameters crucial to the deposition process. It includes wafer temperature, SiH4 partial pressure, and the consequent deposition rate and total film thickness. Again, all these parameters change in time in response to your adjustment of equipment settings. For convenience, the chemical reaction panel also includes a button to reset the integrated deposited film thickness to zero.