High-aspect-ratio vertical surface profiler using sensitive displacement detection by optomecanical probe

This paper proposes an optomechanical surface profiler for high aspect ratio vertical walls. The profiler consists of a bulk silicon micro cantilever probe with a vertical mirror at its end and an integrated sheath fiberguide to insert thinned optical fiber, all fabricated by deep reactive ion etching (DRIE). The probe reflects light by integrated vertical mirror and detects the surface contact point by measuring light power attenuation, which decreases according to the overdrive distance from the contact point. A new stair-shape vertical mirror showed a high (-7.3 dBm/mum) power-to-overdrive sensitivity at 3.5 mum overdriving displacement. Together with an original neck-pinched cantilever design, the proposed profiler showed a potential superiority to conventional piezoresistive detection method and applicability to narrower entrance high aspect ratio structures.