Method for anisotropic etching of structures in conducting materials

Abstract

A method for plating an electrically conductive substance, which includes the steps of contacting the electrically conductive substance with a plating agent in dilute solution, in which the plating agent is present in a concentration of 200 mM at most, and subjecting the plating agent adjacent to the electrically conducive substance to an electric field.

1 . A method for anisotropic etching of a structure in an electrically conductive substance to be etched by means of an etchant which in concentrated solution is usable for isotropic etching of structures in the substance to be etched, characterised by the steps of 
 contacting the substance to be etched with the etchant in a solution which is so diluted that the etchant is unusable for isotropic etching of structures; and    subjecting the etchant adjacent to the substance to be etched to an electric field of such a strength that anisotropic etching of said structure in the substance to be etched is accomplished.    
     
     
         2 . The method for etching as claimed in    claim 1   , wherein the etchant is present in a concentration of 200 mM at most.  
     
     
         3 . The method as claimed in    claim 1    or    2   , wherein the etchant, in concentrated solution, is capable of etching the substance in the absence of an electric field.  
     
     
         4 . The method for etching as claimed in any one of claims  1 - 3 , wherein the capability of the etchant, in dilute solution, of etching the substance to be etched in the absence of an electric field is 5 nm/s at most, preferably 3 nm/s at most.  
     
     
         5 . The method for etching as claimed in any one of the preceding claims, wherein the strength of the electric field is such that the etchant, in dilute solution, is given an increased etching rate which is preferably doubled, and more preferred is at least ten times greater than in the absence of the electric field.  
     
     
         6 . The method as claimed in any one of the preceding claims, wherein the etchant in dilute solution is present in a concentration of 100 mM at most, preferably in a concentration of 50 mM at most, and more preferred in a concentration below 10 mM.  
     
     
         7 . The method as claimed in any one of the preceding claims, wherein the etchant is an ionic substance having the capability of reacting in an etching manner with the substance to be etched.  
     
     
         8 . The method as claimed in any one of the preceding claims, wherein the step of subjecting the etchant to an electric field comprises contacting an electrode with the etchant and applying a voltage between the electrode and the substance to be etched.  
     
     
         9 . The method as claimed in    claim 8   , wherein the electrode is arranged at a distance from the surface to be etched, the distance being 3 cm at most and preferably 1 cm at most, and more preferred 1 mm at most.  
     
     
         10 . The method as claimed in    claim 8    or    9   , wherein the applied voltage between the electrode and the substance to be etched is at least 0.5 V, preferably at least 1 V and more preferred at least 1.5 V, and 10 V at most, preferably 5 V at most and more preferred 3 V at most.  
     
     
         11 . The method as claimed in any one of claims  8 - 10 , wherein the electrode has a tapering portion directed to the electrically conductive substance and arranged at a distance of 10 nm at most from the substance to be etched.  
     
     
         12 . The method for etching as claimed in any one of the preceding claims, wherein etching is carried out during a plurality of first periods, between which the electric field changes.  
     
     
         13 . The method for etching as claimed in    claim 12   , wherein the electric field, between said first periods, is of reversed direction during second periods.  
     
     
         14 . The method as claimed in    claim 13   , wherein plating is accomplished during said second periods, substance to be etched being returned.  
     
     
         15 . The method for etching as claimed in any one of claims  12 - 14 , wherein between said first periods, measurement of the etched depth is carried out during third periods, in which no electric field affects the etchant.  
     
     
         16 . The method for etching as claimed in any one of claims  12 - 15 , wherein said first periods are as great as the time interval therebetween and amount to 200 ms at most, preferably 100 ms at most, and at least 10 ms, preferably at least 50 ms.  
     
     
         17 . An etching fluid, characterised in that it comprises an etchant in dilute solution, in which the etchant is present in a concentration of 200 mM at most, preferably 100 mM at most and more preferred 20 mM at most.  
     
     
         18 . Use of an etching fluid as claimed in    claim 17    for producing structures which are 50 μm or less.  
     
     
         19 . An apparatus for carrying out the method as claimed in any one of claims  1 - 16 .  
     
     
         20 . A method for plating an electrically conductive substance, characterised by the steps of 
 contacting the electrically conductive substance with a plating agent in dilute solution, in which the plating agent is present in a concentration of 200 mM at most, and    subjecting the plating agent adjacent to the electrically conductive substance to an electric field.    
     
     
         21 . A method for plating a structure on an electrically conductive substance to be plated by means of a plating agent which in concentrated solution is usable for isotropic plating of structures on the substance to be plated, characterised by the steps of 
 contacting the substance to be plated with the plating agent in a solution which is so diluted that the plating agent becomes unusable for isotropic plating of structures, and    subjecting the plating agent adjacent to the substance to be plated to an electric field of such a strength that an anisotropic plating of the substance to be plated is accomplished at a plating rate which is relevant for producing said structure on the substance to be plated.    
     
     
         22 . The method as claimed in any one of    claim 20    or    21   , wherein plating occurs during a plurality of second periods, between which etching occurs during a plurality of first periods.