Optimization and characterization of wafer-level adhesive bonding with patterned dry-film photoresist for 3D MEMS integration

A wafer-level adhesive bonding process based on Ordyl SY300, an acrylic permanent dry-film photoresist, is systematically optimized and characterized. Silicon and Pyrex wafers are bonded with a structured 120 μm thick layer of Ordyl. A bond yield of 95% and a tensile bond strength of 13.36 MPa are measured. Membrane-covered cavity structures, that maintain low vacuum pressures in the range of a few kPa over a period of several months, demonstrate leak tightness. The process is applied to fabricate a novel thermopneumatic microvalve with an integrated Peltier-cooler chip for direct temperature control. A wafer-level bond with an Ordyl layer thickness of 20 μm is used for the valve chamber and a chip–wafer bond with 120 μm thick Ordyl is used to integrate a commercial micro-scale Peltier cooler. Test results indicate the functionality of the microvalve, demonstrating the suitability of Ordyl bonding for 3D MEMS fabrication.