Rejuvenation method for ruthenium plating seed

Abstract

A method of rejuvenating a Ru plating seed layer during write pole fabrication in a PMR head is disclosed that involves forming an opening in a mold forming layer. A Ru seed layer is deposited by CVD within the opening and on a top surface of the mold forming layer. The substrate with the Ru seed layer is immersed in an acidic solution and an electric potential is applied for 1 to 2 minutes such that hydrogen is generated to reduce ruthenium oxides to Ru metal on the seed layer surface in an activation step. One or more surfactants are used to improve wettability of the Ru layer. The substrate is transferred directly to an electroplating solution without drying following the activation step to minimize exposure to oxygen that could regenerate oxides on the surface of the Ru layer. As a result, write pole voids and delamination are significantly reduced.

1 . A method of forming a write pole in a perpendicular magnetic recording head, comprising:
 (a) forming an opening in a mold forming layer having a top surface, said opening has a bottom that exposes a portion of a substrate and has sidewalls that extend from the top surface to said substrate;   (b) forming a Ru seed layer along the top surface and sidewalls, and on the bottom of the opening;   (c) immersing said substrate including said Ru seed layer in an acidic solution comprising at least one surfactant, said substrate is attached to a cathode that is electrically connected to an anode wherein both of said cathode and anode are immersed in said acidic solution;   (d) applying an electrical potential that is below a hydrogen evolution reaction condition for the Ru seed layer in said acidic solution to convert any ruthenium oxides on a surface of the Ru seed layer to Ru metal;   (e) removing said substrate from the acidic solution; and   (f) immersing said substrate in an electroplating solution and performing an electroplating process that deposits a magnetic material which fills said opening.   
     
     
         2 . The method of  claim 1  wherein the mold forming layer is a composite layer comprised of a lower alumina layer and an upper Ta layer. 
     
     
         3 . The method of  claim 1  wherein the Ru seed layer has a thickness between about 400 Angstroms and 700 Angstroms. 
     
     
         4 . The method of  claim 1  wherein the Ru seed layer is formed by a CVD deposition, ALD deposition, sputter deposition, or ion beam deposition technique. 
     
     
         5 . The method of  claim 1  wherein the acidic solution has a pH between about 0 and 7, a temperature between about 10° C. and 25° C., and is comprised of HCl or H 2 SO 4 . 
     
     
         6 . The method of  claim 1  wherein the at least one surfactant is sodium dodecyl sulfate or sodium lauryl sulfate and has a concentration in the acidic solution from 0 to about 1 gm/liter. 
     
     
         7 . The method of  claim 1  wherein the electrical potential is between about 0 and −0.8 volts and is applied for a period of about 1 to 2 minutes, said electrical potential depends on the pH and has a larger negative value as the pH becomes a higher positive number. 
     
     
         8 . The method of  claim 1  wherein the substrate is immersed in the electroplating solution without drying the substrate after step (d) is completed. 
     
     
         9 . The method of  claim 5  wherein the electroplating solution has a pH that matches the pH of the acidic solution employed in steps (c) and (d). 
     
     
         10 . The method of  claim 1  wherein the anode is comprised of Ni. 
     
     
         11 . The method of  claim 1  wherein the electrical potential is measured against a hydrogen reference electrode that is immersed in said acidic solution. 
     
     
         12 . A method of rejuvenating a Ru plating seed layer, comprising:
 (a) providing a substrate with a mold forming layer having a top surface thereon and an opening having sidewalls and a bottom surface in the mold forming layer in which a magnetic layer will be deposited in a subsequent step;   (b) forming a Ru plating seed layer along the top surface of the mold forming layer and on the sidewalls and bottom of the opening;   (c) immersing said substrate including said Ru seed layer in an acidic solution comprising at least one surfactant, said substrate is attached to a cathode that is electrically connected to an anode wherein both of said cathode and anode are immersed in said acidic solution; and   (d) applying an electrical potential that is below a hydrogen evolution reaction condition for the Ru seed layer in said acidic solution to convert any ruthenium oxides on a surface of the Ru seed layer to Ru metal.   
     
     
         13 . The method of  claim 12  wherein the mold forming layer is a composite layer comprised of a lower alumina layer and an upper Ta layer. 
     
     
         14 . The method of  claim 12  wherein the Ru seed layer has a thickness between about 400 Angstroms and 700 Angstroms. 
     
     
         15 . The method of  claim 12  wherein the Ru seed layer is formed by a CVD deposition, ALD deposition, sputter deposition, or ion beam deposition technique. 
     
     
         16 . The method of  claim 12  wherein the acidic solution has a pH between about 0 and 7, a temperature between about 10° C. and 25° C., and is comprised of HCl or H 2 SO 4 . 
     
     
         17 . The method of  claim 12  wherein electrical potential is between about 0 and −0.8 volts and is applied for a period of about 1 to 2 minutes, said electrical potential depends on the pH and has a larger negative value as the pH becomes a higher positive number. 
     
     
         18 . The method of  claim 12  wherein the at least one surfactant is sodium dodecyl sulfate or sodium lauryl sulfate and has a concentration in the acidic solution from 0 to about 1 gm/liter. 
     
     
         19 . The method of  claim 12  wherein the acidic solution is further comprised of a buffer agent to maintain the pH in a certain range. 
     
     
         20 . The method of  claim 12  wherein the electrical potential is measured against a hydrogen reference electrode that is immersed in said acidic solution.