Thermal Analysis of an X-ray Irradiated Resist-Substrate Wafer.

LIGA is a relatively new technology used to pattern high aspect ratio microelectromechanical systems HARMEMS in a resist material, using X-ray radiation. Resist materials used in LIGA typically have conduction and thermal expansion properties that are very different from those of the substrate that supports them during the exposure process, and thermal deformations may limit the ability of the LIGA process to reproduce patterns accurately in the resist. A knowledge of the temperature distributions in the resist and substrate will facilitate the study of thermal deformations and their effects on the manufacturing process. The solution of analytical models of the temperature distributions in the resist-substrate system are presented. The primary models presented are a one-layer, two-dimensional model, and a two-layer model in one dimension. Boundary conditions are developed based on current practices used in the LIGA process. Subjects relating to the evaluation of the solutions are discussed, including the characteristics of series solutions and the development of computer programs to handle calculations. The results of some simple temperature measurement experiments performed at the Center for Advanced Microstructures and Devices CAMD are presented, along with a discussion of the relative merits of experimental, computational, and analytical methods of analysis.