Microelectromechanical systems (MEMS) can provide an interface between the digital electronic world and the analog physical world. Depended on the transduction mechanisms, various micromechanical structures are designed to ensure the transductions with highest efficiency. As a consequence, MEMS devices have to be fabricated using a broad range of techniques, and often require integration with the CMOS circuitry. The feasibility of a new fabrication approach has been investigated in this thesis, which uses chemical mechanical polishing (CMP) and oxygen plasma assisted low temperature wafer bonding, to integrate prefabricated MEMS and CMOS devices. Fabricating MEMS and CMOS devices on separate wafers enables the optimisation of each technology separately. However, to integrate them requires low temperature bonding of processed wafers, connecting the bonded wafer pair and bringing the electrical signals to the top surface. Test structures have been used to investigate the feasibility of bonding MEMS and CMOS wafers to create an integrated system with electrical connections. Bonding and thinning of prefabricated wafers has been demonstrated using a CMP enabled surface planarisation process and plasma assisted low-temperature wafer bonding. Inter-wafer connections can be achieved using two fabrication methods. With oxide to oxide bonding method, resistances of 3.8 – 5.2 Ω have been obtained for the via chain test structures with 9-13 contact vias, whilst an average specific contact resistivity of 1.7 x 10<sup>-8</sup>Ω. <i>cm</i><sup>2</sup> has been achieved form the single via test structure. Direct electrical connections between wafers have also been implemented during the bonding anneal stage with an average contact resistance of 2.6x10<sup>-8</sup> Ω.cm<sup>2</sup>.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:653908 |
| Date | January 2007 |
| Creators | Lin, Huamao |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/12422 |
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