This paper shows a new process guideline of high thermal budget process with Si 300 mm wafer in order to eliminate the dislocations. In the case of IGBT, high thermal budget process such as oxidation, diffusion, etc., cause large stress in wafer, and make dislocation propagation, slip, then degrade the device performance and yield. This degradation is enhanced with increasing wafer diameter, and becomes more serious for 300 mm process than that of 200 mm. We clarify the relation between the process condition (time-temperature profile) and dislocation behavior quantitatively under high thermal budget process, and propose the guideline to optimize the process condition. The optimized process minimizes the dislocation propagation in 300 mm Si wafer as same as that in 200 mm Si wafer with the conventional process condition.