The integration of mono-crystalline silicon micro-mirrors on CMOS for SLM applications

Spatial light modulators (SLMs) based on micro-mirrors for use in DUV lithography and adaptive optics need very high mirror planarity as well as mirror stability. We will present results of new micro-mirror arrays, consisting of monocrystalline silicon, which is a material to fulfil these requirements. As all mirrors of the SLM can be separately activated by an underlying CMOS circuit, the integration of CMOS and MEMS must be achieved, which results in certain restrictions on processing temperatures and the compatibility of materials. Therefore a special low temperature bonding technology has been developed, using an adhesive polymer. This technique provides the transfer of a 300nm thin mono-crystalline silicon layer to the CMOS wafer using only 250°C. First silicon micro-mirrors have been made and characterized using pure adhesive polymer (PMGI), improvements using a mix of an inorganic material with a thin bond-polymer benzocyclobutene BCB) on top are in development. Both approaches and their results will be discussed and presented in detail.