MODELING OF 3-DIMENSIONAL EFFECTS ON TEMPERATURE UNIFORMITY IN RAPID THERMAL-PROCESSING OF 8 INCH WAFERS

A three-dimensional steady-state model of the industry-standard AG Ass ociates 4108 Heatpulse Rapid Thermal Processing system has been develo ped for the study of thermal uniformity across 8 inch wafers. The mode l combines radiation energy transfer among all solid surfaces in the c hamber with energy transfer among the chamber materials and to the pro cess ambient. Surfaces included are those of the tungsten filaments of the lamps, the silicon wafer, the polysilicon annular thermal guard r ing, the quartz process tube, and the gold reflectors which surround t he lamps and process tube. These surfaces are divided into approximate ly 4800 individual surface elements for the radiation transfer allowin g very accurate thermal analysis. The model has previously been shown to provide very good agreement with experiment for temperature distrib utions across an 8 inch wafer. The model is presently used to make qua ntitative examinations of asymmetric effects occuring in a RTP chamber which cannot be examined by 2-dimensional models. Situations examined include the effect of nonuniform lamp power distributions. Also exami ned is tilting of the wafer with respect to the flow tube and reflecti ve chamber.