Method and Apparatus for Preventing Galvanic Corrosion in Semiconductor Processing

Abstract

The present invention is related to a method and apparatus for cleaning a semiconductor substrate including on a surface of the substrate at least one structure comprising a first conducting or semiconducting material, surrounded by a layer of a second conducting or semiconducting material, said layer essentially extending over the totality of said surface, the first and second material being in physical contact, the method comprising the steps of: providing the substrate, positioning a counter-electrode facing the substrate surface, and supplying an electrolytic fluid to the space between the surface and the electrode, the counter-electrode acting as an anode in the galvanic cell defined by the substrate surface, the cleaning fluid and the counter-electrode.

1 . A method for cleaning a semiconductor substrate comprising:
 providing a substrate having a surface, a layer comprised of a second conducting or semiconducting material extending over substantially the entire surface of the substrate, and a structure comprised of a first conducting or semiconducting material in physical contact with said first layer such that said structure is on top of said layer or adjacent said layer;   positioning a counter-electrode facing said substrate surface; and   supplying an electrolytic fluid to the space between said substrate surface and the counter-electrode, said counter-electrode acting as an anode in the galvanic cell defined by the substrate surface, the cleaning fluid, and the counter-electrode.   
     
     
         2 . The method according to  claim 1 , wherein the counter-electrode acts as an anode by providing an electrochemical potential difference between the counter-electrode and the layer of a second conducting or semiconducting material. 
     
     
         3 . The method according to  claim 1 , further comprising the step of applying a voltage difference between the layer of a second conducting or semiconducting material and the counter-electrode, said voltage difference being applied so as to create or further enhance said counter-electrode acting as an anode. 
     
     
         4 . The method according to  claim 1 , wherein the counter-electrode is essentially inert with respect to the cleaning fluid. 
     
     
         5 . The method according to  claim 1 , wherein said structures are semiconductor structures and wherein said layer of a second conducting or semiconducting material is a metal layer. 
     
     
         6 . The method according to  claim 1 , wherein said fluid is supplied in one or more locations on the substrate surface covered by said electrode(s), and drained on another location on said surface, so that during the cleaning operation, a continuous stream of cleaning fluid is supplied over the surface to be cleaned. 
     
     
         7 . The method according to  claim 6 , wherein the substrate is a substantially circular wafer and the counter-electrode is substantially circular and arranged concentrically with respect to the wafer, and wherein the counter-electrode is provided with a hole in the center, the supply of fluid being provided through said hole, so that cleaning fluid flows outward from the center of the wafer surface to the edges, during the cleaning operation. 
     
     
         8 . The method according to  claim 1 , wherein said substrate rotates during the cleaning operation. 
     
     
         9 . An apparatus for cleaning a semiconductor substrate, while protecting a surface of the substrate by a cathodic protection mechanism, said apparatus comprising:
 a holder for holding a substrate, said holder comprising a means for clamping said substrate;   at least one counter-electrode, arranged to be placed facing said substrate surface; and   a means for supplying a cleaning fluid to the space between said counter-electrode and said surface.   
     
     
         10 . The apparatus according to  claim 9 , wherein said clamping means is in the form of at least one clamping pin arranged to clamp the substrate and to contact the surface to be cleaned, the apparatus further comprising a voltage source arranged to apply a voltage difference between said at least one clamping pin and said counter-electrode. 
     
     
         11 . The apparatus according to  claim 9 , wherein the means for supplying a cleaning fluid comprises at least one nozzle arranged to supply fluid to the space between the counter-electrode and the surface to be cleaned. 
     
     
         12 . The apparatus according to  claim 11 , wherein the holder is arranged for clamping a substantially circular substrate, and wherein a single counter-electrode is arranged to be placed facing the substrate, and wherein said counter-electrode comprises a central hole, a nozzle being arranged to supply the cleaning fluid through said hole, to the space between the counter-electrode and the surface to be cleaned. 
     
     
         13 . The apparatus according to  claim 9 , wherein the surface of the counter-electrode facing said substrate surface is flat and essentially parallel to said substrate surface. 
     
     
         14 . The apparatus according to  claim 9 , wherein the shape of the counter-electrode is optimized to obtain a distance between the counter-electrode and said surface, said distance not being constant but optimized in order to obtain an essentially uniform protection over the surface to be cleaned. 
     
     
         15 . The apparatus according to  claim 14 , wherein the counter-electrode has a concave-like shape, the distance between the counter-electrode and the surface to be cleaned being smaller in the center of said surface than on the outer edge of said surface. 
     
     
         16 . The apparatus according to  claim 9 , wherein a plurality of counter-electrodes are provided, arranged to be positioned facing the surface to be cleaned, and wherein means are provided to independently adjust the distance between each counter-electrodes and the surface to be cleaned. 
     
     
         17 . The apparatus according to  claim 9 , wherein said electrode is a platinum or platinum-covered electrode.