Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Wire contact – lead – or bond
Reexamination Certificate
2005-02-22
2005-02-22
Cao, Phat X. (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Wire contact, lead, or bond
C257S786000
Reexamination Certificate
active
06858943
ABSTRACT:
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.
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Garrett Stephen E.
Peterson Kenneth A.
Reber Cathleen A.
Cao Phat X.
Sandia Corporation
Watson Robert D.
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