ANALYSES OF THERMAL-STRESSES AND CONTROL SCHEMES FOR FAST TEMPERATURERAMPS OF BATCH FURNACES

This work studies fast temperature ramps of batch furnaces under diffe rent control schemes based on thermal and stress analyses, ri thermal model is first developed to predict temperature distributions on silic on wafers during ramping processes. Thermoelastic model of stresses is then used to predict the onset of slip-line generation under dynamic conditions, Three control schemes, one based on a maximum allowable wi thin-wafer temperature difference, one with a constant cooling rate, a nd the third based on the condition for onset of slip generation, are then analyzed. The results show that in order to achieve the highest r amp rates while maintaining defect-free wafer processing, the ultimate criterion for temperature control of the furnaces should be the condi tion for the onset of defect generation instead of the conventional sc heme based on constant ramp rates.