Elastic interconnection micro contact stuctures-manufacture and characterisation

Abstract: ...The task that was put to the author of this thesis was to find solutions for manufacturing of single elastic micro bump contacts as well as complete elastic sockets and interconnections down to the carrier substrate. Use of more or less standard equipment and methods in electronic industry was a demand too. The casting mold was made in Si by anisotropic wet etching of Si wafers in KOH, and in order to manage and keep preferred distance between casting mold and the currier substrate small columns of SU 8 photo resist were made on the mold as well. For prevention of silicone elastomer sticking to the mold, Parylene was deposited on to the mold. Additionally, making of via holes is treated in this work. Two techniques were tried practically. Laser drilling has shown some potential but RIE of silicone elastomer was found to be more useful so far. Deposition of required metal layers was realized by sputtering and patterning was conducted by applying electro plated photo resist and exposing in a low divergence light mask aligner. Some limited characterization of manufactured elastic micro bump contacts by measuring their contact resistance is also reported. Some advantages of elastic micro bump contact based structures relative to already existing similar interconnection techniques is discussed. Some discussions concerning remaining technological problems and thin film contact resistance estimation issues are presented as well as the promising results, up to 45 000 contact points per cm2, achieved by scaling down the structures.

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