Transient ALD simulations for a multi-wafer reactor with trenched wafers

For a large multi-wafer vertical batch ALD reactor, transient, 3-dimensional, multi-scale simulations have been performed for the TEMAH pulse step during a HfO2 ALD process. A bi-directional, multi-scale coupling has been established between continuum reactor scale simulations and molecular trench scale simulations. For describing the molecular deposition process inside narrow deep trenches, two different models have been developed and implemented as boundary condition for the flow simulation: an analytical model based on the model proposed by Gordon, and a numerical Knudsen diffusion model. Both trench models have been validated against DSMC simulation results for a single trench. Based on the 3D reactor simulation results, important timescales in the complete process are identified. It is found that several timescales are of the same order of magnitude, rendering predictions based on engineering rules more difficult. Timescales for trenched wafers are found to be much larger than for flat wafers, leading to much longer required cycle times

Simulation and validation of SiO2_2 LPCVD from TEOS in a vertical 300 mm multi-wafer reactor

Combining a slightly modified version of the chemical reaction mechanism for silicon-dioxide LPCVD from TEOS as proposed by Coltrin and coworkers, and the commercially available CFD program CFD-ACE+, a 21) model has been derived for gas flow, transport phenomena and deposition chemistry in the ASM A412 vertical 300mm multiwafer reactor. Silicon-dioxide deposition from TEOS is strongly influenced by gas-phase reactions, producing a reactive intermediate that is responsible for the majority of deposition. This phenomenon underlines the importance of the chemistry model in simulations. As a result of the gas phase intermediate, strong radial non-uniformities are observed. The simulation results have been validated against experimental growth rate data for various process conditions