Wafer counter-bonding for integrating cte-mismatched substrates and its application to MEMS tuneable metamaterials

This paper presents symmetrical counter-bonding as a method for integrating multiple substrates of non-compatible thermo-mechanical properties. This technique is successfully applied to fabricate MEMS tuneable high-impedance surfaces combining four substrates of two otherwise fabrication-incompatible materials (silicon and AF45 glass) on a wafer-level. A large-scale high-impedance surface with 200×52 array elements with a pitch of 350µm and a total size of 70×18mm2 has been fabricated and the microwave properties of the devices have successfully been characterized at 70–114GHz. Furthermore, micron-sized surface waviness in the glass substrates, induced by the thermal cycling under mechanical stress in the bonding process, has been investigated during temperature cycling.

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