Low-cost maskless grayscale lithography using a new photo-definable polyimide for polymer MEMS applications

We present the novel use of a positive-tone photosensitive polyimide for the rapid production of grayscale features using a maskless lithography system including several sample geometries to illustrate the general capabilities of this method. Commonly used in the fabrication of MEMS and other micro-scale devices, polyimide films are known for their extreme mechanical and thermal stability. Unfortunately, photo-definable polyimides historically have possessed significantly limiting critical properties, i.e. decreased elongation, low tensile strength and high film stresses. The use of a new polyimide, HD-8820, overcomes these limitations and allows direct patterning of polyimide into complex geometries without the need for imprinting, plasma etching or other secondary processing steps. The entire fabrication sequence, from CAD file to cured structure, can take only 4 hours making this a fast, low-cost method of producing polymer MEMS devices with excellent mechanical properties.