High precision electrochemical micromachining based on confined etchant layer technique

High-quality products come from high-quality instrument. We present here an optimized instrument for electrochemical micromachining, in which a granite bridge base, a macro–micro dual driven positioning stage and a force-displacement sensing module are combined to promote dramatically the tool–workpiece alignment, in-situ monitoring and product quality. As a testing experiment, a polymethylmethacrylate (PMMA) microlens array with a diameter of 110 μm and a height of 3.5 μm has been transferred successfully onto the surface of an n-GaAs wafer by the confined etchant layer technique (CELT). The machining tolerance is about 3.4 nm and the surface roughness is lower than 8.0 nm. Moreover, the presented techniques have significance in the precise electrochemical instruments for not only micromachining but also scanning electrochemical probe techniques.

► High-quality GaAs microlens array is fabricated with a tolerance of 3.4 nm and a surface roughness of 8.0 nm.
► New mechanical designs are adopted to promote tool-workpiece alignment, in-situ monitoring and product quality.