Mechanical stability of spatial light modulators in microlithography

The Fraunhofer IPMS and Micronic Laser Systems AB have developed a technology for microlithography using spatial light modulation (SLM). This technology uses an array of micromirrors as a programmable mask, which allows parallel writing of 1 million pixels with a frame rate of up to 2 kHz. The SLM is fabricated at the IPMS using its high-voltage CMOS process. The mirrors are fabricated by surface micromachining using a polymer as sacrificial layer. The mirrors are operated in an analog mode to allow sub-pixel placement of pattern features. This paper describes the function of the SLM with an emphasis on the stability of the mirror deflection and a method to improve it which has been implemented.