Solution for the electroplating of soft magnetic Co-Fe-Ni alloys

Abstract

The present invention provides a Co—Fe—Ni plating solution comprising salts of Co, Fe and Ni and a stabilizing agent. The stabilizing agent has at least one citrate salt in an amount effective to act as a stabilizing agent. The present invention also provides a method for forming a thin Co—Fe—Ni alloy plated magnetic film with high saturation magnetization and low coercivity using the citrate-based Co—Fe—Ni plating solution.

1 . A Co—Fe—Ni plating solution comprising salts of Co, Fe and Ni and a stabilizing agent, wherein the stabilizing agent comprises at least one citrate salt in an amount effective to act as a stabilizing agent.  
     
     
         2 . The Co—Fe—Ni plating solution according to  claim 1 , wherein the Co—Fe—Ni plating solution has a pH greater than or equal to about 3.5.  
     
     
         3 . The Co—Fe—Ni plating solution according to  claim 2 , wherein the pH is between about 3.5 and about 8.  
     
     
         4 . The Co—Fe—Ni plating solution according to  claim 3 , wherein the pH is about 5.3.  
     
     
         5 . The Co—Fe—Ni plating solution according to  claim 1 , wherein the salt of Ni has a concentration in the range of about 0.05M to about 0.4M.  
     
     
         6 . The Co—Fe—Ni plating solution according to  claim 1 , wherein the salt of Ni is NiSO 4 .  
     
     
         7 . The Co—Fe—Ni plating solution according to  claim 6 , wherein NiSO 4  has a concentration of about 0.3M.  
     
     
         8 . The Co—Fe—Ni plating solution according to  claim 1 , wherein the salt of Co has a concentration in the range of about 0.01M to about 0.2M.  
     
     
         9 . The Co—Fe—Ni plating solution according to  claim 1 , wherein the salt of Co is CoSO 4 .  
     
     
         10 . The Co—Fe—Ni plating solution according to  claim 9 , wherein CoSO 4  has a concentration of about 0.08M.  
     
     
         11 . The Co—Fe—Ni plating solution according to  claim 1 , wherein the salt of Fe has a concentration in the range of about 0.005M to about 0.05M.  
     
     
         12 . The Co—Fe—Ni plating solution according to  claim 1 , wherein the salt of Fe is FeSO 4 .  
     
     
         13 . The Co—Fe—Ni plating solution according to  claim 12 , wherein FeSO 4  has a concentration of about 0.015M.  
     
     
         14 . The Co—Fe—Ni plating solution according to  claim 1 , wherein the citrate salt has a concentration in the range of about 0.05M to about 0.4M.  
     
     
         15 . The Co—Fe—Ni plating solution according to  claim 1 , wherein the citrate salt is sodium citrate, potassium citrate or ammonium citrate.  
     
     
         16 . The Co—Fe—Ni plating solution according to  claim 15 , wherein potassium citrate has a concentration of about 0.206M.  
     
     
         17 . The Co—Fe—Ni plating solution according to  claim 15 , wherein ammonium citrate has a concentration of about 0.395M.  
     
     
         18 . The Co—Fe—Ni plating solution according to  claim 1 , further comprising a pH buffering agent.  
     
     
         19 . The Co—Fe—Ni plating solution according to  claim 18 , wherein the pH buffering agent has a concentration in the range of about 0.1M to about 0.4M.  
     
     
         20 . The Co—Fe—Ni plating solution according to  claim 18 , wherein the pH buffering agent is H 3 BO 3 .  
     
     
         21 . The Co—Fe—Ni plating solution according to  claim 20 , wherein H 3 BO 3  has a concentration of about 0.4M.  
     
     
         22 . The Co—Fe—Ni plating solution according to  claim 1 , further comprising a surfactant.  
     
     
         23 . The Co—Fe—Ni plating solution according to  claim 22 , wherein the surfactant has a concentration in the range of about 0.01 g/L to about 0.05 g/L.  
     
     
         24 . The Co—Fe—Ni plating solution according to  claim 23 , wherein the surfactant is sodium lauryl sulfate.  
     
     
         25 . The Co—Fe—Ni plating solution according to  claim 24 , wherein sodium lauryl sulfate has a concentration of about 0.01 g/L.  
     
     
         26 . A method for forming a thin Co—Fe—Ni alloy plated magnetic film comprising: 
 (a) providing a substrate to be plated;    (b) immersing the substrate in a Co—Fe—Ni plating solution according to  claim 1;  and    (c) applying a plating current.    
     
     
         27 . The method according to  claim 26 , wherein the substrate is a Si wafer coated with Ti/Au blanket metallizations, and wherein the substrate has Au as a seed layer for plating.  
     
     
         28 . The method according to  claim 26 , wherein the plating current is applied using a method selected from one or more of direct current, pulsed current, pulsed reversed current and pulsed conditioned current.  
     
     
         29 . The method according to  claim 28 , wherein the plating current is pulsed current.  
     
     
         30 . The method according to  claim 29 , wherein the pulsed current has a duty cycle of 10 ms with 0.3 ms of on-time (t on ) and 9.7 ms of off time.