Wafer-scale needle array

Abstract

Methods for wafer-scale fabrication of needle arrays can include mechanically modifying a wafer to produce a plurality of vertically-extending columns. The columns are etched to round and reshape the columns into substantially uniformly shaped needles. Needle arrays having needle width non-uniformity of less than about 3% and length non-uniformity of less than about 2% can be produced.

1 . A method for wafer-scale fabrication of needle arrays comprising:
 providing a wafer;   mechanically modifying the wafer to produce a plurality of vertically-extending columns;   etching the wafer to reshape the vertically-extending columns under conditions suitable to produce a plurality of substantially uniformly shaped needles from the plurality of vertically-extending columns; and   separating the wafer into a plurality of individual needle arrays after etching.   
     
     
         2 . The method of  claim 1 , wherein mechanically modifying the wafer further comprises defining a plurality of sacrificial columns to provide a substantially uniform column sidewall area density across the wafer. 
     
     
         3 . The method of  claim 2 , further comprising removing the sacrificial columns after etching the wafer. 
     
     
         4 . The method of  claim 1 , wherein etching the wafer further comprises:
 immersing the wafer in an etching solution;   rotating the wafer in the etching solution in a first direction; and   stirring the etching solution with a stirrer in a second direction opposite to the first direction.   
     
     
         5 . The method of  claim 4 , wherein immersing the wafer in etching solution further comprises placing the wafer in a holder. 
     
     
         6 . The method of  claim 5 , wherein placing the wafer in a holder further comprises providing an o-ring gasket between the back side of the wafer and the holder to prevent contact between the back side of the wafer and the etching solution. 
     
     
         7 . The method of  claim 5 , wherein placing the wafer in a holder further comprises placing a plurality of wafers into a common holder and simultaneously etching the plurality of wafers. 
     
     
         8 . The method of  claim 1 , wherein the uniformly shaped needles have a width non-uniformity of less than about 5%. 
     
     
         9 . The method of  claim 8 , wherein the uniformly shaped needles have a width non-uniformity of less than about 3%. 
     
     
         10 . The method of  claim 1 , wherein the uniformly shaped needles have a length non-uniformity of less than about 5%. 
     
     
         11 . The method of  claim 1 , wherein the uniformly shaped needles have a length non-uniformity of less than about 2%. 
     
     
         12 . The method of  claim 1 , wherein the plurality of substantially uniformly shaped needles include extra rows of sacrificial needles formed from extra rows of sacrificial columns in the plurality of vertically-extending columns. 
     
     
         13 . The method of  claim 1 , further comprising depositing electrically conductive material on the uniformly shaped needles. 
     
     
         14 . The method of  claim 1 , further comprising depositing electrically insulative material on the uniformly shaped needles except at tip portions of the needles.