AVS 58th Annual International Symposium and Exhibition
    Thin Film Division Thursday Sessions
       Session TF2-ThM

Paper TF2-ThM2
ISSG Chemistry Modeling to Understand Uniformity Issues in RTP

Thursday, November 3, 2011, 8:20 am, Room 110

Session: Modeling and Analysis of Thin Films
Presenter: Shailesh Gupta, Applied Materials, Inc.
Authors: S. Gupta, Applied Materials, Inc.
U. Kelkar, Applied Materials, Inc.
Correspondent: Click to Email
This paper describes three-dimensional flow/thermal/chemistry modeling efforts to study the silicon oxidation using In-Situ Steam Generation (ISSG). This 3D model incorporates 27 step gas phase reaction mechanism which is responsible for ISSG chemistry. The complex 3D geometry, supersonic flow, detailed chemistry pose major challenges to the model convergence and results in unrealistic results due to H2 and O2 exothermic reaction. Complex 3D geometry causes CFD model mesh size to become more than a million cells. The computational times to include all chemical reactions on a 3D complex flow problem are exorbitant. Thus a simple 2D RTP chamber model was built to examine the validity of gas phase reaction mechanism by comparing in-house simulation results with Professor Robert J. Kee, Colorado School of Mines [1] and to set the solver control parameters for stable solution in 3D. After a working 2D model, simple representative 3D model was built with very good quality structured mesh and the further geometric complexity was added in steps. The oxygen radical distribution predicted from the model matched very well with the oxide growth uniformity over a wide range of chamber pressure, gas flow rate, hydrogen fraction, and gas distributor geometry. At 5 torr, temperature distribution is dominated by wafer temperature as gas phase reaction is weak. At higher pressure exothermic gas phase reaction causes higher temperature above the wafer. There is weak gas phase reaction at 5 torr, resulting in low O atom number density. The O radicals diffuse in the chamber due to higher velocity at 5 torr where they recombine. At higher pressure flame ignites right at the edge of the wafer due to higher residence time resulting in very high O atom number density at the edge. This well calibrated simulation model was used in understanding and expanding process space by optimizing on several hardware and process variables using virtual prototyping before building the hardware.