A 3-D thermo-elastic finite element model was established in this paper to study the transient behavior of thermal expansion and the distribution of thermal stress in a wafer by the absorption of exposure energy during the exposure process. The analysis procedure of investigating the thermal expansion of the wafer including the transient behavior in a single exposure region, the thermal interactions between neighboring exposure regions to the variation of exposure energy, the interval of exposure locations, and ends with the interval of exposure time under continuous exposure. The results indicate that the thermal deformation gradient of the wafer can be improved by adjusting the location interval and the time interval between the neighboring exposure regions, Widening the interval of exposure locations has a greater impact in improving the thermal deformation of wafer than extending the interval of exposure time between the image fields. The physical phenomenon can serve as a supporting reference tool for engineers in planning exposure paths, and the simulation model can serve as an analysis tool to understand the behavior during the exposure process.