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Release resistant electrical interconnections for MEMS devices

United States Patent

February 22, 2005
View the Complete Patent at the US Patent & Trademark Office
Sandia National Laboratories - Visit the Intellectual Property Management and Licensing Website
A release resistant electrical interconnection comprising a gold-based electrical conductor compression bonded directly to a highly-doped polysilicon bonding pad in a MEMS, IMEMS, or MOEMS device, without using any intermediate layers of aluminum, titanium, solder, or conductive adhesive disposed in-between the conductor and polysilicon pad. After the initial compression bond has been formed, subsequent heat treatment of the joint above 363 C creates a liquid eutectic phase at the bondline comprising gold plus approximately 3 wt % silicon, which, upon re-solidification, significantly improves the bond strength by reforming and enhancing the initial bond. This type of electrical interconnection is resistant to chemical attack from acids used for releasing MEMS elements (HF, HCL), thereby enabling the use of a "package-first, release-second" sequence for fabricating MEMS devices. Likewise, the bond strength of an Au--Ge compression bond may be increased by forming a transient liquid eutectic phase comprising Au-12 wt % Ge.
Peterson; Kenneth A. (Albuquerque, NM), Garrett; Stephen E. (Albuquerque, NM), Reber; Cathleen A. (Corrales, NM)
Sandia Corporation (Albuquerque, NM)
10/ 396,879
March 25, 2003
FEDERALLY SPONSORED RESEARCH The United States Government has rights in this invention pursuant to Department of Energy Contract No. DE-AC04-94AL85000 with Sandia Corporation.