Electrochemical etching

Abstract

Methods to etch a workpiece are described. In one embodiment, a workpiece is disposed within an etchant solution having a composition comprising a dilute acid and a non-ionic surfactant. An electric field is generated within the etchant solution to cause an anisotropic etch pattern to form on a surface of the workpiece.

1 . A method, comprising: 
 disposing a workpiece within an etchant solution having a composition comprising a dilute acid and a non-ionic surfactant; and    generating an electric field within the etchant solution to cause an anisotropic etch pattern to form on a surface of the workpiece.    
     
     
         2 . The method of  claim 1 , wherein the dilute acid is selected from a group consisting of citric acid and oxalic acid.  
     
     
         3 . The method of  claim 1 , wherein the non-ionic surfactant comprises an alkyl ethoxylate or an alkyl ethoxylate blend.  
     
     
         4 . The method of  claim 3 , wherein the alkyl ethoxylate includes a C7-C10 alkyl chain and a molecular weight of about 550.  
     
     
         5 . The method of  claim 1 , wherein the etchant solution comprises a citric acid and an alkyl ethoxylate blend.  
     
     
         6 . The method of  claim 1 , wherein the dilute acid of the etchant solution has a pH value between about 2 to 4 and a pK value greater than 2.  
     
     
         7 . The method of  claim 1 , wherein disposing further comprises submerging the workpiece in a bath of the etchant solution, the bath also having an electrode disposed adjacent to the workpiece, the electrode and workpiece coupled to a power supply.  
     
     
         8 . The method of  claim 7 , wherein generating the electric field further comprises applying a current between about 0.05 amp to 2.0 amp to the electrode and workpiece.  
     
     
         9 . The method of  claim 7 , wherein generating the electric field further comprises applying a current density between about 50-150 mA/cm 2 .  
     
     
         10 . The method of  claim 8 , wherein applying the current further comprises generating an etch rate between about 5 nm/sec to about 20 nm/sec.  
     
     
         11 . The method of  claim 7 , wherein submerging further comprises forming a space about 1 mm to about 10 mm between the workpiece and the electrode.  
     
     
         12 . The method of  claim 8 , wherein applying the current produces an aspect ratio value of greater than 1 for an etch depth relative to an etch width on the surface of the workpiece.  
     
     
         13 . The method of  claim 1 , wherein the workpiece comprises a disk substrate, and wherein disposing further comprises plating a NiP layer over the disk substrate.  
     
     
         14 . The method of  claim 13 , wherein plating further comprises depositing an embossable layer over the NiP layer.  
     
     
         15 . The method of  claim 14 , wherein depositing further comprises imprinting the embossable layer with a stamper having a template of an etch pattern to be formed on the NiP layer.  
     
     
         16 . The method of  claim 15 , wherein the etch pattern comprises a DTR pattern.  
     
     
         17 . The method of  claim 16 , wherein stamping further comprises ashing the embossable layer to expose the NiP layer in the recessed areas.  
     
     
         18 . The method of  claim 17 , wherein generating the electric field further comprises forming a plurality of recessed areas on the surface of the NiP layer corresponding to the DTR pattern.  
     
     
         19 . A method, comprising: 
 disposing a workpiece within an etchant solution having a composition comprising a dilute acid, a non-ionic surfactant, and an adsorbate; and    generating an electric field within the etchant solution to cause an anisotropic etch pattern to form on a surface of the workpiece.    
     
     
         20 . The method of  claim 19 , wherein the adsorbate comprises alkylbenzene sulfonic acid.  
     
     
         21 . The method of  claim 19 , wherein the adsorbate comprises 2-benzimidazole proprionic acid.  
     
     
         22 . The method of  claim 19 , wherein the dilute acid is selected from a group consisting of citric acid and oxalic acid.  
     
     
         23 . The method of  claim 19 , wherein the non-ionic surfactant comprises an alkyl ethoxylate or an alkyl ethoxylate blend.  
     
     
         24 . The method of  claim 23 , wherein the alkyl ethoxylate includes a C7-C10 alkyl chain and a molecular weight of about 550.  
     
     
         25 . The method of  claim 19 , wherein the etchant solution comprises a citric acid, an alkyl ethoxylate blend, and an alkylbenzene sulfonic acid.  
     
     
         26 . The method of  claim 19 , wherein the dilute acid of the etchant solution has a pH value between about 2 to 4 and a pK value greater than 2.  
     
     
         27 . The method of  claim 19 , wherein disposing further comprises submerging the workpiece in a bath of the etchant solution, the bath also having an electrode disposed adjacent to the workpiece, the electrode and workpiece coupled to a power supply.  
     
     
         28 . The method of  claim 27 , wherein generating the electric field further comprises applying a current between about 0.05 amp to 2.0 amp to the electrode and workpiece.  
     
     
         29 . The method of  claim 27 , wherein generating the electric field further comprises applying a current density between about 50-150 mA/cm 2 .  
     
     
         30 . The method of  claim 28 , wherein applying the current further comprises generating an etch rate between about 5 nm/sec to about 20 nm/sec.  
     
     
         31 . The method of  claim 27 , wherein submerging further comprises forming a space about 1 mm to about 10 mm between the workpiece and the electrode.  
     
     
         32 . The method of  claim 28 , wherein applying the current produces an aspect ratio value of greater than 1 for an etch depth relative to an etch width on the surface of the workpiece.  
     
     
         33 . The method of  claim 19 , wherein the workpiece comprises a disk substrate, and wherein disposing further comprises plating a NiP layer over the disk substrate.  
     
     
         34 . The method of  claim 33 , wherein plating further comprises depositing an embossable layer over the NiP layer.  
     
     
         35 . The method of  claim 34 , wherein depositing further comprises imprinting the embossable layer with a stamper having a template of a etch pattern to be formed on the NiP layer.  
     
     
         36 . The method of  claim 35 , wherein the etch pattern comprises a DTR pattern.  
     
     
         37 . The method of  claim 34 , wherein stamping further comprises ashing the embossable layer to expose the NiP layer in the recessed areas.  
     
     
         38 . The method of  claim 37 , wherein generating the electric field further comprises forming a plurality of recessed areas on the surface of the NiP layer corresponding to the DTR pattern.  
     
     
         39 . An electrochemical etchant, comprising: 
 a solution of about 0.35% to about 3.5% of a dilute acid and a non-ionic surfactant.    
     
     
         40 . The etchant of  claim 39 , wherein the non-ionic surfactant comprises an alkyl ethoxylate blend with a C7 to C10 alkyl chain and a molecular weight of about 550.  
     
     
         41 . The etchant of  claim 39 , wherein the dilute acid comprises citric acid and the non-ionic surfactant comprises an alkyl ethoxylate blend.  
     
     
         42 . The etchant of  claim 39 , wherein the dilute acid has a pH value between about 2 to 4 and a pK value greater than 2.  
     
     
         43 . The etchant of  claim 39 , wherein the dilute acid is selected from a group comprising citric acid and oxalic acid.  
     
     
         44 . An electrochemical etchant, comprising: 
 a solution of about 0.35% to about 3.5% of a dilute acid, a non-ionic surfactant, and a nickel adsorbate.    
     
     
         45 . The etchant of  claim 44 , wherein the non-ionic surfactant comprises an alkyl ethoxylate blend with a C7 to C10 alkyl chain and a molecular weight of about 550.  
     
     
         46 . The etchant of  claim 44 , wherein the dilute acid comprises citric acid, the non-ionic surfactant comprises an alkyl ethoxylate blend, and the nickel adsorbate comprises an alkylbenzene sulfonic acid.  
     
     
         47 . The etchant of  claim 44 , wherein the dilute acid has a pH value between about 2 to 4 and a pK value greater than 2.  
     
     
         48 . The etchant of  claim 1 , wherein the dilute acid is selected from a group comprising citric acid and oxalic acid.  
     
     
         49 . The etchant of  claim 44 , wherein the nickel adsorbate is selected from a group comprising alkylbenzene sulfonic acid and 2-benzimidazole proprionic acid.  
     
     
         50 . An apparatus, comprising: 
 means for disposing a workpiece within an etchant solution having a composition comprising a dilute acid and a non-ionic surfactant; and    means for generating an electric field within the etchant solution to cause an anisotropic etch pattern to form on a surface of the workpiece.    
     
     
         51 . The apparatus of  claim 50 , wherein the dilute acid is selected from a group consisting of citric acid and oxalic acid.  
     
     
         52 . The apparatus of  claim 50 , wherein the non-ionic surfactant comprises an alkyl ethoxylate or an alkyl ethoxylate blend.  
     
     
         53 . The apparatus of  claim 50 , wherein means for disposing further comprises means for submerging the workpiece in a bath of the etchant solution, the bath also having an electrode disposed adjacent to the workpiece, the electrode and workpiece coupled to a power supply.  
     
     
         54 . The apparatus of  claim 53 , wherein means for generating the electric field further comprises means for applying a current between about 0.05 amp to 2.0 amp to the electrode and workpiece.  
     
     
         55 . The apparatus of  claim 54 , wherein means for applying the current further comprises means for generating an etch rate between about 5 nm/sec to about 20 nm/sec.  
     
     
         56 . The apparatus of  claim 54 , wherein means for applying the current produces an aspect ratio value of greater than 1 for an etch depth relative to an etch width on the surface of the workpiece.  
     
     
         57 . The apparatus of  claim 50 , wherein the workpiece comprises a disk substrate, and wherein means for disposing further comprises means for plating a NiP layer over the disk substrate.  
     
     
         58 . The apparatus of  claim 57 , wherein means for plating further comprises means for depositing an embossable layer over the NiP layer.  
     
     
         59 . The apparatus of  claim 58 , wherein means for depositing further comprises means for imprinting the embossable layer with a stamper having a template of a etch pattern to be formed on the NiP layer to form raised areas and recessed areas on the embossable layer.  
     
     
         60 . The apparatus of  claim 59 , wherein means for stamping further comprises means for ashing the embossable layer to expose the NiP layer in the recessed areas.  
     
     
         61 . The apparatus of  claim 60 , wherein means for generating the electric field further comprises means for forming a plurality of recessed areas on the surface of the NiP layer corresponding to a DTR pattern.