Jurgen H. Daniel

Large-area MEMS fabrication with thick SU-8 photoresist applied to an x-ray image sensor array

ABSTRACT Micro-Electro-Mechanical System (MEMS) fabrication on large area substrates is promising for novel systemconcepts, but processes based on crystalline silicon cannot be used. Polymeric materials such as the thick photoresist SU-8are more appropriate for this purpose because their processing can be scaled to large areas. An X-ray image sensor arraybased on amorphous silicon on glass substrates was taken as an example to apply the SU-8 microfabrication technique. Weanticipate an improved performance of the imager. The resolution of the X-ray imager is expected to increase by patterning the X-ray conversion screen into cells, which match the sensor pixels of the imager, and SU-8 defines these cells. Furthermore, SU-8 functions as a thick interlayer dielectric with electroplated interconnects in order to decrease capacitivecoupling between different layers of the thin film electronics. This will decrease the electronic noise and result in a highersensitivity of the imager. The fabrication process with SU-8 will be described and challenging issues, especially whenconsidering large area substrates, will be discussed.Keywords: large area MEMS, micromachining, SU-8, HARMS, X-ray imager, interlayer dielectric, electroplating