Micro-optical elements and their integration to glass and optoelectronic wafers

Polymer replication technique enables for low cost devices even in the case of aspheric or irregular shaped surfaces, submicron or other challenging structures. The use of W-reaction moulding on semiconductors, glass or other inorganic substrates as the replication technique leads to a high degree of stability and allows for the simultaneous integration of optoelectronics or ion exchanged GRIN elements. Thin polymer layers on inorganic substrates show high flatness and lower wavefront deviations with respect to all-polymer elements. They show low lateral shrinkage during the UV-polymerisation, and the lateral thermal expansion is determined by the substrate. Furthermore, sensitive substrates can be used because the process does not involve high mechanical stress or elevated temperatures. Original structures for the replication masters are fabricated by different resist technologies. Subsequently, they are proportionally transferred by dry etching (RIE) into glass or silicon, or, the resist structure is transformed into a metal master by electroplating. The utilisation of W-transparent replication tools allows for the use of opaque substrates (i.e. detectors). Locally UV-transparent replication tools enable a combination of replication and resist technology (leading to elements with new features) or can protect sensitive areas like bond pads from being coated with optical layers. The fabrication of isolated polymer elements on arbitrary substrates is an advantage of UV-reaction moulding against injection moulding or hot embossing.