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Implantable microelectronic device and method of manufactureRelated Patent Categories: Active Solid-state Devices (e.g., Transistors, Solid-state Diodes), Housing Or Package, With Desiccant, Getter, Or Gas FillingImplantable microelectronic device and method of manufacture description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070096281, Implantable microelectronic device and method of manufacture. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority of Provisional Patent Application No. 60/732,884, "Implantable Microelectronic Device and Method of Manufacture," filed Nov. 02, 2005, the disclosure of which is incorporated herein by reference. FIELD OF THE INVENTION [0003] The present invention is related to implantable medical devices, and is particularly related to implantable microelectronic devices. BACKGROUND OF THE INVENTION [0004] Biocompatibility is a critical concern for medical devices that are designed to be implanted in vivo. Biocompatibility is necessary to avoid adverse reactions in the subject, and to avoid device failure as a result of exposure to the corrosive saline body fluids and other substances in the tissue surrounding the implant. Where an implanted device includes one or more components that are not, themselves, biocompatible, it is known to provide hermetic sealing of such devices with a chemically inert coating to achieve biocompatibility, i.e., in order to avoid adverse reactions and device degradation. Many such implantable devices are intended to remain in place over long periods of time, imposing a long life requirement on the manner of hermetic sealing. [0005] Miniature implantable medical devices commonly include microelectronic components, such as integrated circuit chips fabricated on silicon substrates. Ion beam assisted deposition ("IBAD") of alumina, often referred to an aluminum oxide (Al.sub.2O.sub.3), has been proposed for hermetically sealing such devices. Alumina has good biocompatibility, and IBAD is a useful technique for depositing dense, adherent, defect-free conformal thin films. The use of IBAD to deposit alumina on implantable medical devices is described in U.S. Pat. No. 6,844,023, entitled "Alumina Insulation For Coating Implantable Components And Other Microminiature Devices," the disclosure of which is incorporated by reference. [0006] Most implantable microelectronic devices require means for connecting to the devices for purposes of supplying power to the device or for routing electrical signals to or from the device. Such devices include, for example, stimulators which operate by providing current to the surrounding tissue, and sensors which measure chemical or electrical properties of the surrounding tissue. When an insulator, such as alumina, is used as a coating on a device to provide hermetic sealing, a conductive path through the alumina to an external contact is typically required. For implantable devices fabricated on silicon using standard silicon processing technology, the contact pads on the device are normally copper or aluminum, neither of which is biocompatible. Thus, semiconductor device contact pads cannot simply be left exposed by patterning the surrounding alumina layer. [0007] A prior art structure addressing the need to provide means for connecting to a sealed, implantable electronic device is disclosed in U.S. Pat. No. 6,516,808, entitled "Hermetic Feedthrough For An Implantable Device," the disclosure of which is also incorporated by reference. The '808 patent depicts several embodiments of "hermetic" electrical feedthrough structures. Thus, the embodiment of FIGS. 5A and 5B of the patent show simple via structures, while the embodiments of FIGS. 6A, 6B and 7 show "serpentine" feedthrough structure which are said to provide greater "hermeticity." Implicit in the '808 patent's discussion of the serpentine feedthrough structures, and as confirmed by the inventors hereof, is the fact that the prior art simple via feedthrough structures are not adequately hermetic, particularly in applications where they will remain in vivo for a lengthy period. While use of a serpentine structure may overcome this inadequacy, such structures are generally more difficult to fabricate and, in some instances, consume valuable "real estate" on the surface of the device. [0008] Another approach to providing a hermetic electrical path through a conformal electrically insulating film is described in co-assigned U.S. Pat. No. 6,858,220, the disclosure of which is incorporated by reference. The '220 patent describes extremely thin (e.g., 40 nm) ultra-nanocrystalline diamond coatings wherein an electric path through the film is created by selective ion implantation. Unfortunately, this solution has limited applicability to extremely thin films that can be rendered suitably conductive by ion implantation. [0009] Accordingly, a structure which provides better hermetic sealing of a feedthrough between an implantable microelectronic device and the surface of an encapsulating insulator is needed. SUMMARY OF THE INVENTION [0010] In a first aspect, the present invention is directed to an implantable microelectronic device having an electrical contact pad that is made of a non-biocompatible material; a plurality of thin, biocompatible, patterned conductive layers formed over the electrical contact pad, the top surface of the patterned conductive layers defining an electrical contact, and the first conductive layer being in direct contact with the electrical contact pad; a biocompatible electrically insulating material hermetically surrounding the device, the electrically insulating material having an aperture wherein the electrical contact is positioned. Preferably the electrically insulating material is a biocompatible ceramic, such as alumina, and the patterned conductive layers comprise one or more platinum layers formed on one or more titanium layers. The microelectronic device may be an integrated circuit chip, such that the electrical contact pad is aluminum or copper. Preferably, the first patterned conductive layer is larger in its lateral dimensions than the contact pad, such that the layer extends beyond the edge of the contact pad, forming a shoulder. [0011] In another aspect the present invention is directed to an implantable device, comprising a microelectronic device having a conductive contact pad surrounded by electrically insulating material, at least one patterned titanium layer formed on the contact pad and extending beyond the edge of the contact pad, at least one patterned platinum layer formed over the titanium layer, the platinum layer having an exposed upper contact surface, and an alumina layer hermetically surrounding the microelectronic device and the patterned layers, the alumina layer having an aperture which exposes the upper contact surface. Preferably, the device has a plurality of patterned titanium layers and a plurality of patterned platinum layers, and one of the patterned titanium layer defines a shoulder. [0012] In another aspect the present invention is directed to a method of making an implantable device having an electrical contact, comprising: (1) providing an electrical device having a contact pad, (2) forming a plurality of biocompatible, patterned conductive layers over the contact pad, the plurality of conductive layers having a first layer formed on the contact pad and a top electrical contact surface, (3) forming a hermetic, biocompatible electrically insulating layer over the resulting structure, and (4) forming an aperture in the electrically insulating layer to expose the electrical contact surface. Preferably, the hermetic, biocompatible electrically insulating layer is a ceramic material, such as alumina, formed by ion beam assisted deposition. Likewise, preferably the patterned conductive layers are formed by ion beam assisted deposition of metals, such as titanium and platinum, and at least one patterned conductive layer is larger than the contact pad such that it extends beyond the edge of the contact pad. In addition, preferably, at least one of the patterned conductive layers has a shoulder. The step of forming an aperture preferably comprises use of laser machining. A sacrificial layer may optionally be formed over the top electrical contact surface, such that the top electrical contact surface is protected during subsequent processing. Thereafter, the sacrificial layer may be removed. BRIEF DESCRIPTION OF THE DRAWINGS [0013] The foregoing aspects and the attendant advantages of this invention will become more readily apparent by reference to the following detailed description when taken in conjunction with the accompanying drawings, wherein: [0014] FIG. 1 is a cross-sectional view of an embodiment of the present invention. [0015] FIG. 2A is a cross-sectional view of the embodiment of FIG. 1 at an interim step during fabrication. [0016] FIG. 2B is a cross-sectional view of the embodiment of FIG. 1 at a later step of fabrication. [0017] FIG. 3 is a cross-sectional view of an alternate embodiment of the present invention having a built up electrode. [0018] FIG. 4 is a cross-sectional view of an alternate embodiment of the present invention showing the mask deposition. [0019] FIG. 5 is a cross-sectional view of an alternate embodiment of the present invention showing the mask patterning. [0020] FIG. 6 is a cross-sectional view of an alternate embodiment of the present invention showing the material deposition. Continue reading about Implantable microelectronic device and method of manufacture... Full patent description for Implantable microelectronic device and method of manufacture Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Implantable microelectronic device and method of manufacture patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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