Conformally encapsulated multi-electrode arrays with seamless insulation

Abstract

Thin-film multi-electrode arrays (MEA) having one or more electrically conductive beams conformally encapsulated in a seamless block of electrically insulating material, and methods of fabricating such MEAs using reproducible, microfabrication processes. One or more electrically conductive traces are formed on scaffold material that is subsequently removed to suspend the traces over a substrate by support portions of the trace beam in contact with the substrate. By encapsulating the suspended traces, either individually or together, with a single continuous layer of an electrically insulating material, a seamless block of electrically insulating material is formed that conforms to the shape of the trace beam structure, including any trace backings which provide suspension support. Electrical contacts, electrodes, or leads of the traces are exposed from the encapsulated trace beam structure by removing the substrate.

We claim: 
     
         1 . A method of fabricating an electrode array, comprising:
 suspending at least one thin-film electrically conductive trace beam(s) over a substrate, wherein the trace beam(s) is suspended by at least one support portion(s) thereof in contact with the substrate;   encapsulating the suspended trace beam(s) in a seamless coating of an electrically insulating material; and   removing the substrate to expose an electrically conductive surface of the support portion(s) of the encapsulated trace beam(s).   
     
     
         2 . The method of  claim 1 ,
 wherein the trace beam(s) is suspended by selectively removing scaffold material upon which the trace beam(s) is formed while the support portion(s) of the trace beam(s) remains in contact with the substrate.   
     
     
         3 . The method of  claim 2 ,
 wherein the scaffold material is a portion of the substrate.   
     
     
         4 . The method of  claim 3 ,
 wherein the selectively removed portion of the substrate is a sacrificial layer adjacent a release layer of the substrate.   
     
     
         5 . The method of  claim 4 , further comprising:
 forming at least one via opening(s) through the sacrificial layer to the release layer; and   forming a thin-film electrically conductive layer on the sacrificial layer and in the via opening(s) so that removal of the sacrificial layer forms at least one post(s) of the trace beam(s) which remains in contact with the release layer.   
     
     
         6 . The method of  claim 4 ,
 wherein the removing step includes releasing the support portion(s) from the release layer of the substrate.   
     
     
         7 . The method of  claim 3 ,
 wherein the portion of the substrate is selectively removed by isotropic etch to form substrate columns in contact with the support portion(s) of the trace beam(s).   
     
     
         8 . The method of  claim 1 ,
 further comprising providing at least one trace backing(s) to reinforce the trace beam(s) in suspension, and   wherein the trace beam(s) and the trace backing(s) together are encapsulated with the electrically insulating material.   
     
     
         9 . The method of  claim 8 ,
 wherein the trace backing(s) and multiple trace beams form a multi-tiered trace beam stack that is suspended over the substrate and encapsulated with the electrically insulating material.   
     
     
         10 . The method of  claim 8 ,
 further comprising providing an adhesion promoting layer between the trace backing(s) and the electrically insulating material.   
     
     
         11 . The method of  claim 1 ,
 wherein the trace beam(s) is encapsulated by vapor deposition.   
     
     
         12 . The method of  claim 1 ,
 further comprising joining two or more of the encapsulated trace beams together with an electrically insulating material.   
     
     
         13 . The method of  claim 1 ,
 further comprising forming an adhesion promoting layer on the suspended trace beam prior to encapsulation.   
     
     
         14 . The method of  claim 13 ,
 wherein the adhesion promoting layer is vapor-deposited on the suspended trace beam prior to encapsulation.