Modeling and experimental verification of the 300 mm Ar anneal process

Abstract

We demonstrate a new model for simulating thermal and gravitational induced stress appearing in state of the art 300 mm argon annealing processes. Purpose of this work is to predict the allowable ramp rates in a vertical batch furnace system. The gravitational induced bending stress is modeled by using methods from structural mechanics like common finite element modeling. Calculation of the important specular reflecting radiation component – transporting extra radiation energy to the wafer center between the spacing of two horizontally oriented wafers – was achieved by using finite volume methods known from fluid dynamics. A reduction of the total resolved shear stress could be determined from our model if specular reflection is taken into account and thus allowing higher ramp rates. We furthermore demonstrate new experimental data for the upper yield stress of 300 mm Si-ingots with different boron and nitrogen co-doping levels. Especially at high temperatures, the upper yield stress of high ohmic material drops down significantly thus making it necessary to use planar support geometries to diminish the gravitational induced bending stress.