Patent ID: 7951300

Claim:
A method of wafer-scale fabrication of high-aspect ratio needle arrays comprising: providing a mono-crystalline silicon wafer; sawing the wafer on a back side along a first plurality of lines to produce a plurality of mesas; forming glass between the plurality of mesas; sawing the wafer on a front side along a second plurality of lines to a depth sufficient to intersect the glass to produce a plurality of vertically-extending columns, the vertically-extending columns arranged into a plurality of individual arrays of columns separated by sacrificial columns; placing the wafer into a holder so the plurality of vertically-extending columns are exposed and the back side of the wafer is sealed within the holder; immersing the wafer into an etching solution having a mixture of hydrofluoric acid and nitric acid; simultaneously stirring the etching solution in one direction with a stirrer while rotating the wafer in an opposite direction for a first time interval to reshape the vertically-extending columns into rounded columns; positioning the wafer into the etching solution with the vertically-extending columns in an upward position for a second time interval to produce a plurality of substantially uniformly shaped needles from the plurality of rounded columns; and separating the wafer into a plurality of individual needle arrays after etching.