Hotplate For Photoresist Baking

Lithograghy and its relative techniques play a very important role in MEMS fabrication processes, Spin coating and baking are an indispensable working procedure before and after the lithography process. Oven and hotplate are often employed in order to enhance adhesion between the film and the substrate, stabilize sensitivity of film and improve the abrasion resistance when the film touches a mask in contact exposure. Because it is easy to obtain good uniformity along thickness of film with the use of hotplate, hotplate is very commonly applied in thick film.Surface temperature uniformity, control precision and rise time are main performances of hotplate. Foreign hotplate has nice quality, but high price often stays us away from it, while we have less choices in domestic ones yet. A hotplate that has high control precision, uniformity and rise time is designed for the research work of our lab.On the basis of substantive information about that, the structure of hotplate, combination of each parts, materials and heaters of hotplate are selected according to the hotplate's demand, then FEM is applied to analyzing the surface temperature. After plenty of simulations with ANSYS software and regulating heating position, arrangement of heaters could meet the need of uniformity, which result from optimizing design. The good uniformity was obtained by the result of the temperature.According to step-response experiment, math model of the hotplate was set up and the temperature of controlling system including temperature detection circuit, PD controller, voltage pulse-wide transforming circuit and executor was designed. PD parameters satisfying the precision of hotplate are obtained after debug.The system performance tests and error analysis was put up at 90℃ and 120℃ that is very often used, the results show that the rise time is less than 20 min, and control precision is within± 1℃, and that the requirement of the hotplate is met..