Patent ID: 8597490

Claim:
A method of manufacturing a gas electron multiplier (GEM), said GEM comprising an insulating sheet having first and second surfaces, first and second metal layers provided on top of said first and second surface, respectively, and a plurality of throughholes extending through said insulating sheet and said first and second metal layers, said method comprising the following steps: preparing a blank sheet comprising an insulating sheet provided with first and second metal layers on its first and second surfaces, respectively, said first and second metal layers having an initial thickness; a first metal layer hole forming step in which the first metal layer is patterned by means of photolithography to form holes through said first metal layer, an insulating sheet hole forming step, in which the holes formed in the first metal layer are extended through the insulating layer by etching from the first surface side; and a second metal layer hole forming step, in which the holes formed in the first metal layer and the insulating sheet are extended through the second metal layer, said second metal layer hole forming step comprising an electrochemical etching process in which a voltage is applied between the second metal layer and an electrode immersed in the etchant, said voltage being chosen such that only the second metal layer is etched, while the first metal layer remains substantially unaffected.