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

Abstract

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 UV-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 UV-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

Fiber-chip coupling with silicon microlenses

“…Otherwise, in case the individual lenses need a serial origination e.g. by a direct writing process, an intermediate replication technique, [25], might be well adopted. From the application perspective almost arbitrary lens profiles are desired, especially lens profiles with conics and aspherical ones.…”

Wafer-Level Hybrid Integration of Complex Micro-Optical Modules

“…The direct replication of lens arrays onto detector arrays including lateral and axial alignment was already proposed [2]. In particular, selective UV curing using a partially UV-transparent replication tool allows for the electrical bonding of separated chips.…”

“…Lithography involves the structuring of several layers, aligned to each other, and, thus, offers an integration capability. More than ten years ago, UV polymer on glass replication [1] using a modified mask aligner as a lithography related fabrication tool was introduced as a precise and cost effective technology for the generation of wafer-scale miniaturized optical systems and for hybrid integration [2]. Parallel fabrication is especially useful in cases of miniaturized systems because one can obtain a high number of chips from a wafer and in cases where several structural layers have to be aligned to each other.…”

“…In the present paper we present a refined wafer-level fabrication technology involving UV polymer molding, coating and lithography which is based on earlier work [2] but is characterized by a much higher degree of variety and complexity. Within the frame of this paper, the main focus will be on the diversity of systems that have been realized using this technology, as well as on the fabrication details, range of parameters, and on the potential and limits of the approach.…”

Design of a micro-optical low coherent interferometer array for the characterisation of MEMS and MOEMS

“…The resulting resist profile is then transferred into the final optical structure by UV reaction moulding onto the backside of the lens substrate. The latter process will be performed in a special mask aligner on the whole wafer at once [7]. This gives sufficient alignment accuracy between the refractive lens positions and the diffractive correction structure.…”