Modeling and parameter estimation in a single wafer rapid thermal reactor.

摘要

Rapid Thermal Processing (RTP) is an emerging technology in semiconductor processing where the wafer is heated to a high temperature in seconds as against hours commonly encountered in conventional furnaces. This technology is used in the Rapid Thermal Annealing, Oxidation, Nitridation and in Chemical Vapor Deposition. All of these operations share the common thermal processing technique, RTP.;This study concentrates on RTP in the commercial Rapro system developed by AG Associates. The primary interest is in investigating wafer temperature and temperature uniformity as a function of process operating conditions. Two-dimensional simulations of the coupled momentum and energy balance model were shown to predict process behavior sufficiently well. However, such models rely on computationally intensive fluid flow algorithms that severely limit their applicability to prediction. They were used to search for operating conditions that ensure primarily non-recirculating flow and lower volume of stagnant gas. Recirculating cells are common in RTP systems, particularly because strong buoyancy effects drive the flow characterized by high Grashof numbers, ;The fluid flow and energy balance model was reduced in stages to separate the dominant modes of heat transfer. Sensitivity of the model was studied with respect to the effect on the wafer temperature profile. Fluid flow effects were quite insignificant compared to the effect of ambient gas especially during the heat-up period of the RTP cycle. Energy balance models solved throughout the reactor are far more computationally efficient than the coupled flow and energy balance models. They also provide a higher accuracy level over pure radiation models published in existing RTP literature--a key result in this research effort.;The fundamental energy balance model was validated by dynamic temperature measurements from an instrumented four-inch wafer subjected to the RTP cycle. Model predictions compared favorably with the qualitative trends in experimental data. Experiments were also performed to develop simple empirical process models for the RTP process. Empirical models were unable to capture process nonlinearities encountered during multi-step wafer heating. However, they performed relatively well when operating conditions matched with those used in model development.