In this work we presented the influence of the thermal treatments in polymer employed in microelectronics and Micro Electro Mechanical System (MEMS) process. The thermal steps can cause adhesion failure, pin holes problems, hillocks and increase of stress in the devices structures. We studied three polymers type based in Novolac and PMMA matrix. These materials was analyzed by technique analyze thermal DSC (Differential Scanning Calorimetry) and the stress mechanical was measurement by substrate curvature. With those analyses we can possible obtained a relationship by a polymer glass transition and mechanical stress observed in structures of microelectronics devices.