Implantable microelectronic device and method of manufacture

Abstract

An implantable hermetically sealed microelectronic device, and method of manufacture are disclosed. The microelectronic device of the present invention is hermetically encased in a insulator, such as alumina formed by ion bean assisted deposition (“IBAD”), with a stack of biocompatible conductive layers extending from a contact pad on the device to an aperture in the hermetic layer. In a preferred embodiment, one or more patterned titanium layers are formed over the device contact pad, and one or more platinum layers are formed over the titanium layers, such that the top surface of the upper platinum layer defines an external, biocompatible electrical contact for the device. Preferably, the bottom conductive layer is larger than the contact pad on the device, and a layer in the stack defines a shoulder.

1 . A microelectronic device, comprising: 
 a microelectronic device having an electrical contact pad thereon,    at least one thin patterned conductive layer formed over said electrical contact pad, the top surface of said at least one patterned conductive layers defining an external electrical contact surface, wherein the first layer of said at least one patterned conductive layer is in direct contact with said electrical contact pad,    an electrically insulating material hermetically surrounding said microelectronic device, said electrically insulating material having an aperture wherein said external electrical contact surface is positioned.    
   
   
       2 . The microelectronics device of  claim 1  wherein said at least one thin patterned conductive layer and said insulating material are biocompatible.  
   
   
       3 . The microelectronic device of  claim 2  wherein said electrically insulating material is a ceramic.  
   
   
       4 . The microelectronic device of  claim 3  wherein said ceramic is alumina, Zirconia, or aluminum nitride.  
   
   
       5 . The microelectronic device of  claim 3  wherein said ceramic is alumina.  
   
   
       6 . The microelectronic device of  claim 3  wherein said electrically insulating material is a metal oxide.  
   
   
       7 . The microelectronic device of  claim 3  wherein said electrically insulating material is a polymer.  
   
   
       8 . The microelectronic device of  claim 2  wherein a first layer of said at least one patterned conductive layer comprise gold, nickel, or chromium.  
   
   
       9 . The microelectronic device of  claim 2  wherein a first layer of said at least one patterned conductive layer comprise a titanium layer.  
   
   
       10 . The microelectronic device of  claim 2  wherein a second layer of said at least one patterned conductive layer comprise at least one biocompatible metal.  
   
   
       11 . The microelectronic device of  claim 2  wherein said at least one patterned conductive layer comprise a platinum layer.  
   
   
       12 . The microelectronic device of  claim 7  comprising a platinum layer formed over said titanium layer.  
   
   
       13 . The microelectronic device of  claim 2  wherein said at least one patterned conductive layer comprise at least one platinum layer formed over at least one titanium layer.  
   
   
       14 . The microelectronic device of  claim 1  wherein said substrate comprising a microelectronic device is an integrated circuit chip and said electrical contact pad is aluminum, aluminum alloy, copper or copper alloy.  
   
   
       15 . The microelectronic device of  claim 1  wherein a first patterned conductive layer is larger in its lateral dimensions than said electrical contact pad, such that said patterned conductive layer extends beyond the edge of said contact pad.  
   
   
       16 . The microelectronic device of  claim 15  wherein said first patterned conductive layer is titanium and at least one overlying conductive layer is platinum.  
   
   
       17 . The microelectronic device of  claim 15  wherein one of said conductive layers defines a shoulder.  
   
   
       18 . A device, comprising: 
 a microelectronic device located on a silicon substrate, said microelectronic device having a conductive contact pad surrounded by electrically insulating material,    at least one patterned first metal layer formed on said contact pad and extending beyond the edge of said contact pad,    at least one patterned second metal layer formed over said first metal layer, said second metal layer having an exposed upper contact surface,    an electrically insulating material layer hermetically surrounding said microelectronic device and said patterned layers, said electrically insulating material layer having an aperture which exposes said upper contact surface.    
   
   
       19 . The implantable device of  claim 18  wherein the first metal layer comprises at least one patterned titanium layer.  
   
   
       20 . The implantable device of  claim 18  wherein the second layer comprises at least one patterned platinum layer.  
   
   
       21 . The implantable device of  claim 18  wherein said first layer defines a shoulder.  
   
   
       22 . A method of making a device having an electrical contact, comprising the steps of: 
 providing an electrical device having a contact pad,    forming at least one patterned conductive layer over said contact pad, said at least one conductive layer having a first layer formed on said contact pad and a top electrical contact surface,    hermetically encasing the resulting structure in an electrical insulator,    forming an aperture in said electrical insulator to expose said electrical contact surface.    
   
   
       23 . The method of  claim 22  where said electrical contact surface and said electrical insulator are biocompatible.  
   
   
       24 . The method of  claim 22  wherein said step of hermetically encasing the structure in a biocompatible insulator comprises ion beam assisted deposition of a ceramic material.  
   
   
       25 . The method of  claim 22  wherein the step of forming at least one patterned conductive layer comprises ion beam assisted deposition of at least one metal.  
   
   
       26 . The method of  claim 22  wherein at least one of said patterned metal layers is titanium or titanium alloy.  
   
   
       27 . The method of  claim 22  wherein at least one of said patterned metal layers is platinum or platinum alloy.  
   
   
       28 . The method of  claim 22  wherein at least one patterned layer of titanium and at least one patterned layer of platinum are formed by beam assisted deposition.  
   
   
       29 . The method of  claim 22  wherein said first patterned conductive layer is larger than said contact pad such that it extends beyond the edge of said contact pad.  
   
   
       30 . The method of  claim 22  wherein the step of forming an aperture comprises laser machining.  
   
   
       31 . The method of  claim 22  further comprising the steps of forming a sacrificial layer over said top electrical contact surface, such that the top electrical contact surface is protected during subsequent processing and, thereafter, removing said sacrificial layer.  
   
   
       32 . The method of  claim 22  wherein one of said conductive layers defines a shoulder.  
   
   
       33 . The method of  claim 22  further comprising filling said aperture with metal.