Method and plating bath for depositing a magnetic film

Abstract

A cobalt-iron-boron (CoFeB) film ( 100 ) is electrolessly deposited on a substrate ( 150 ) using a chloride plating bath. The plating bath may include a primary metal in a concentration of between approximately 0.05 moles per liter and approximately 0.4 moles per liter, a secondary metal in a concentration of between approximately 0.005 moles per liter and approximately 0.04 moles per liter, a complexing agent in a concentration of between approximately 0.15 and approximately 0.8 moles per liter, a pH buffer in a concentration of between approximately 0.5 and approximately 1.5 moles per liter, and a reducing agent in a concentration of between approximately 0.05 and approximately 0.25 moles per liter.

1 . A method comprising:
 providing a substrate;   forming a seed layer on the substrate; and   electrolessly depositing a CoFeB film over the seed layer using a chloride bath.   
     
     
         2 . The method of  claim 1  wherein:
 the CoFeB film has a hard-axis coercivity no greater than approximately 2 Oe and a resistivity no greater than approximately 53 μOhm-cm.   
     
     
         3 . The method of  claim 1  further comprising:
 applying a magnetic field to a surface of the substrate.   
     
     
         4 . The method of  claim 1  wherein:
 the CoFeB film is electrolessly deposited in the absence of an external magnetic field.   
     
     
         5 . The method of  claim 1  further comprising:
 performing a thermal anneal on the CoFeB film.   
     
     
         6 . The method of  claim 5  wherein:
 following the thermal anneal the CoFeB film has a hard-axis coercivity no greater than approximately 0.5 Oe and a resistivity no greater than approximately 39 μOhm-cm.   
     
     
         7 . The method of  claim 1  further comprising:
 adjusting or maintaining a pH of the chloride bath such that it is between approximately 8.3 and approximately 9.7; and   adjusting or maintaining a temperature of the chloride bath such that it is between approximately 50 and approximately 85 degrees Celsius.   
     
     
         8 . A plating bath comprising:
 a primary metal in a concentration of between approximately 0.05 moles per liter and approximately 0.4 moles per liter;   a secondary metal in a concentration of between approximately 0.005 moles per liter and approximately 0.04 moles per liter;   a complexing agent in a concentration of between approximately 0.15 and approximately 0.8 moles per liter;   a pH buffer in a concentration of between approximately 0.5 and approximately 1.5 moles per liter; and   a reducing agent in a concentration of between approximately 0.05 and approximately 0.25 moles per liter.   
     
     
         9 . The plating bath of  claim 8  wherein:
 a pH level of the plating bath is between approximately 8.3 and approximately 9.7.   
     
     
         10 . The plating bath of  claim 8  wherein:
 a temperature of the plating bath is between approximately 50 degrees and approximately 85 degrees Celsius.   
     
     
         11 . The plating bath of  claim 8  wherein:
 the primary metal comprises cobalt (II) chloride.   
     
     
         12 . The plating bath of  claim 8  wherein:
 the secondary metal comprises iron (II) sulfide.   
     
     
         13 . The plating bath of  claim 8  wherein:
 the complexing agent comprises citrate.   
     
     
         14 . The plating bath of  claim 8  wherein:
 the pH buffer comprises ammonium chloride.   
     
     
         15 . The plating bath of  claim 8  wherein:
 the reducing agent comprises dimethylamineborane.