Abstract

Melting photoresist cylinders is an often described /l/ and effective method to produce microlenses. One of the possible application areas is optical communications where they serve as coupling elements between the light source and the fibre or between the fibre and the detector. In optical communications single mode fibres are preferred because of the absence of mode dispersion and mode noise. For this case the working wavelength lies in the infrared frequency band (e.g. 1300nm) and so resist lenses are not suited because of their high absorption coefficient. One possible solution is the use of silicon microlenses which can be obtained by reactive ion etching (RIE) of the resist lenses. In order to get well defined lenses an extensive study of the each parameters is necessary. The melting process of resist cylinders produces nearly ideal spherical lenses because of the surface tension. A “one to one" copy by RIE of such resist lens into silicon is not possible. Apart from die fact that it is difficult to obtain a selectivity of 1:1 between resist and silicon which would guarantee equal heights of resist and etched lens the main reason for this behaviour is the specific etch mechanism of the RIE. The etching process is of a chemical nature supported by ion bombardment.

© 1996 IEEE