In the heater module of the annealing unit in the semiconductor manufacturing equipment, failures frequently occur during the harsh thermal process. To investigate the thermal performance of the heater module at parametric conditions, the FEA thermal model of the heater module was developed and validated by comparing with the measurements. As a result, the axial temperature difference of the heater surface was carefully investigated. It was found that the effect of the heating pattern gap on the temperature difference of the heater surface was considerable.