Thin film protective layer with buffering interface

Abstract

A method for sputtering a thin film protective layer that allows the protective layer (overcoat) to be ultra-thin with improved durability over prior art films is disclosed. The method reduces kinetic energy of the ions of the overcoat material during the initial period of deposition to form a buffering interface which reduces the interpenetration of the atoms of the protective layer into the underlying film. In the method of the invention the sputtering of the overcoat preferably begins with zero (or very low) voltage applied to the underlying film resulting in minimal ion implantation in the underlying film. The “high energy” phase of the process begins with increases in the magnitude of the negative bias voltage applied to the underlying film. The higher energy imparted to ions in the plasma result in a denser and harder film being formed over the initial buffer layer. The protective layer preferably comprises carbon and nitrogen. The protective layer structure of the invention is preferably used over a magnetic layer on thin film magnetic media.

1 . An article with a thin film layer structure comprising: 
 a conductive thin film; and    a protective layer formed on the conductive thin film, the protective layer comprising carbon and nitrogen and having a lower density nearer the conductive thin film and a higher density nearer a surface of the protective layer.    
     
     
         2 . The article of  claim 1  wherein the conductive film is ferromagnetic.  
     
     
         3 . The article of  claim 2  wherein the atomic percentage of nitrogen is from 5 to 25 atomic percent.  
     
     
         4 . The article of  claim 2  wherein the protective layer is from 0.5 to 9 nanometers thick.  
     
     
         5 . The article of  claim 2  wherein the conductive thin film is an alloy of cobalt.  
     
     
         6 . A method of depositing thin films comprising the steps of: 
 depositing a conductive thin film layer on an article;    depositing a buffer layer on the conductive thin film layer comprising carbon and nitrogen while applying a bias voltage from zero to a first negative voltage applied to the conductive thin film layer for a first time period;    changing the bias voltage to a second negative voltage, the second negative voltage being greater in magnitude than the first negative voltage; and    depositing a thin film layer comprising carbon and nitrogen on the buffer layer while the bias voltage is the second negative voltage for a second time period.    
     
     
         7 . The method of  claim 6  wherein the conductive thin film layer is ferromagnetic.  
     
     
         8 . The method of  claim 7  further comprising the steps of applying holding the article at a first set of points while depositing the conductive thin film layer and applying bias voltage through a second set of points different from the first set of points while depositing the thin film layer comprising carbon and nitrogen.  
     
     
         9 . The method of  claim 8  further comprising the steps of rotating the article after depositing the conductive thin film layer and before depositing the buffer layer and applying the second negative voltage to the conductive film through the second set of points where the conductive thin film layer was not subject to shadowing during deposition.  
     
     
         10 . The method of  claim 7  wherein the second negative voltage is a dc voltage from −50 v to −400 v.  
     
     
         11 . The method of  claim 7  wherein the second negative voltage is a pulsed voltage from ground to −400 v.  
     
     
         12 . The method of  claim 7  wherein a thickness of layers comprising carbon and nitrogen is from 0.5 to 9 nm.  
     
     
         13 . The method of  claim 7  wherein the second time period is longer than the first time period.  
     
     
         14 . The method of  claim 13  wherein the second time period is approximately four times as long as the first time period.  
     
     
         15 . The method of  claim 6  wherein a thickness of layers comprising carbon and nitrogen is from 0.5 to 9 nm, the second negative voltage is a dc voltage from −50 v to −400 v and the method further comprises the step of applying the second negative voltage to the conductive thin film layer at one or more points where the conductive thin film layer was not subject to shadowing during deposition.  
     
     
         16 . A disk drive comprising: 
 a magnetic transducer including a read and a write head for reading and writing magnetic transitions;    a spindle; and    a thin film disk mounted on the spindle to rotate in a confronting position in relation to the magnetic transducer, the thin film disk including magnetic material in which the magnetic transducer writes magnetic transitions; and    a overcoat comprising carbon and nitrogen over the magnetic material, the overcoat having a buffer layer of a lower density adjacent to the magnetic material and layer of higher density at a surface of the overcoat.    
     
     
         17 . The disk drive of  claim 16  wherein the atomic percentage of nitrogen in the overcoat is from 5 to 25 atomic percent.  
     
     
         18 . The disk drive of  claim 16  wherein the overcoat is from 0.5 to 9 nanometers thick.  
     
     
         19 . The disk drive of  claim 16  wherein the magnetic material is an alloy of cobalt.  
     
     
         20 . The disk drive of  claim 16  wherein the atomic percentage of nitrogen in the overcoat is from 5 to 25 atomic percent and the overcoat is from 0.5 to 9 nanometers thick.