Micromachining has potential applications for large area image sensors and displays, but conventional micro-electro-mechanical system (MEMS) technology based on crystalline silicon wafers cannot be used. Instead, large area devices use deposited films on glass substrates. This presents many challenges for MEMS, both with regard to materials for micromachined structures and to integration with large area electronic devices. We are exploring the novel thick photoresist SU-8 as well as plating techniques for the fabrication of large area MEMS. As an example of its application, we have employed this MEMS technology to improve the performance of an amorphous silicon based x-ray image sensor array. SU-8 is explored as the structural material for the x-ray conversion screen and as a thick interlayer dielectric for the thin film readout electronics of the imager. Plating techniques are employed to metallize the deep contact vias in SU-8. Processing challenges that are particularly important for large area fabrication will be addressed.