Atomic layer deposition (ALD) using multiwafer batch reactors has now emerged as the manufacturing process of choice for modern microelectronics at a massive scale. Stringent process requirements of thin film deposition uniformity within wafer (WiW) and wafer–wafer (WTW) in the batch, film conformity along submicrometer wafer features, thin film quality, and the utilization of expensive precursors in the reactor dictate ALD reactor design and process parameter optimization. This paper discusses a particle-based direct-simulation Monte Carlo (DSMC) of the full reactor scale simulation that overcomes the low Knudsen number limitation of typical continuum computational fluid dynamics approaches used for modeling low-pressure ALD reactors. A representative industrial multiwafer batch reactor used for the deposition of Si-based thin films with N2 and Si2Cl6 (hexachlorodisilane) as process feed gases with pressures in the range 43–130 Pa and a uniform reactor temperature of 600 °C is simulated. The model provides detailed insights into the flow physics associated with the transport of the precursor species from the inlets, through wafer feed nozzles, into the interwafer regions, and finally through the outlet. The reactor operating conditions are shown to be in the slip/transitional flow regime for much of the reactor volume and especially the feed gas nozzle and interwafer regions (where the Knudsen number approaches ∼0.2), justifying the need for a high-Knudsen number DSMC approach as in this work. For the simulated conditions, the nonuniformity of precursor species immediately above the wafer surface is predicted to be within <1% for a given wafer and <2% across the entire multiwafer stack. Results indicate that higher pressure degrades WiW and WTW uniformity. A reactor flow efficiency is defined and found to be ∼99%, irrespective of the chamber pressure.
<div class="section abstract"><div class="htmlview paragraph">The electric or hybrid vehicles need fast switching operation in order to ensure the quick-response of the motors. This process is carried out by compact direct-current contactors which are designed to perform the switching over multiple cycles. During the contact separation, the gas between the contacts breaks down and the resulting thermal arc provides a conductive channel that sustains the current. Until the arc is quenched, the current continues to flow through the contacts despite the physical separation. This unintended flow of current could lead to a larger response time than the safe operation limits. We perform high-fidelity simulation of thermal arc in hydrogen-nitrogen mixture environment under external magnetic field of 1 Tesla. The hydrogen enrichment level is kept at 0%, 40%, 50% and 80%. The contacts are separated at 8 m/s. It is demonstrated that the increase in hydrogen concentration leads to smaller arc lifetime thereby improving the circuit interruption performance.</div></div>
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