Mask-substrate gap control system for exposure equipment

Abstract

Precise printed circuit boards (PCBs) and touch screen panels (TSPs) are produced by the proximity exposure patterning process. In the exposure patterning process, the smaller the gap between the mask and the substrate-under the condition that the mask and the substrate are not in contact-the higher the resolution of the pattern obtained. Unlike a substrate that is fixed on a rigid frame, in the exposure patterning process, only the edges of the mask are fixed, and therefore the center portion of the mask sags under its own weight (in a middle-sized mask, the self-weight deflection of the center portion is approximately 150 mu m to 200 mu m). Thus, the gap between the mask and the substrate is not constant, and as a result, the resolution of the pattern at the outer part of the mask is degraded. To compensate for this degradation in resolution, during this study, the table on which the substrate was fixed was deformed according to the sagging shape of the mask. The table deformation was performed using two methods. One method used employed an array of electromagnets that were installed under the ferromagnetic table on which the substrate was fixed. Another method used involved an array of actuator modules that directly deformed the duralumin table on which the substrate was fixed. Simulations and experiments were performed to validate this approach.