A silicon microcantilever biosensor fabricated on SOI wafers using a two-step releasing approach

This paper reports the fabrication of a piezoresistive microcantilever biosensor using a unique two-step front-side releasing method, which combines anisotropic etching and isotropic etching. The microcantilever sensors are fabricated on single crystalline SOI wafers to exploit the high piezoresistive coefficients. The anisotropic etching exposes the sidewalls beneath the microcantilevers, and the following isotropic etching undercuts the substrate and suspends the microcantilevers. Thin and uniform microcantilevers with a yield of 100% have been successfully fabricated. Significant improvement in releasing efficiency of 10 times higher than the conventional backside releasing has been achieved. Detection of Immunoglobulin G (IgG) specific binding down to 0.2 mug/ml with the microcantilever sensor demonstrates the potential applications as a biosensor for biomolecular specific binding detection.