Preliminary experiments for the fabrication of thermally actuated bimorph cantilever arrays on non-silicon wafers with vertical interconnects

This paper describes the first steps for the fabrication of low-cost cantilever arrays, developed at RAL, on non-silicon polymer substrates with vertical interconnects, produced at Profactor. The deflection and actuation of these cantilevers is based on the bimorph thermal actuation principle. The fabrication of the cantilever arrays requires many process steps which are presented in this article. The first step is the planarization between the via-holes interconnects with a uniform layer. This was achieved by spin coating of a thick (~58μm) SU-8 layer. In the subsequent step, two thin metal layers of Cr (500Å) and Au (1000Å) were thermally deposited and patterned, using UV lithography with a mask alignment process and wet etching. The following step was the coating of a 1μm structural Au layer, in which the deposited layer had a very poor adhesion. Alternative procedures were explored to overcome this problem in the future. Modifications of the photo masks design and the substrates will be carried out to make the RAL microcantilevers technology more compatible with Profactor substrates.