Double layer patterning and technique for making a magnetic recording head

Abstract

Double photolithography is used to produce an under-layer of protective and filtering photoresist over a substrate that will have channels milled with a FIB. Secondary layers are applied with precision on top of the first layer in order to define the precise patterns to be milled and to provide targeting and alignment fiducials.

I claim:  
     
         1 . A method comprising: 
 providing a first layer of photoresist on a substrate;    providing a second layer of photoresist on an upper surface of the first layer to define a target area; and    milling the target area with a milling device.    
     
     
         2 . The method of  claim 1 , wherein the substrate includes a thin film on at least a portion of an upper surface of the substrate, wherein the first layer of photoresist is provided over at least a portion of the thin film.  
     
     
         3 . The method of  claim 1 , wherein the first layer of photoresist is provided over substantially all of an upper surface of the substrate.  
     
     
         4 . The method of  claim 1 , wherein the first layer of photoresist is provided over substantially all of an upper surface of the substrate except for at least one predefined area of the substrate that is exposed to provide grounding for the milling device.  
     
     
         5 . The method of  claim 1 , further comprising hard baking the first layer of photoresist prior to applying the second layer of photoresist.  
     
     
         6 . The method of  claim 1  wherein the second layer of photoresist includes a plurality of target areas each defined by an independent portion of the second layer.  
     
     
         7 . The method of  claim 1 , wherein the second layer of photoresist defines a writing gap for a magnetic recording head.  
     
     
         8 . The method of  claim 1 , wherein the second layer of photoresist defines a timing based writing gap for a magnetic recording head.  
     
     
         9 . The method of  claim 1 , wherein the first and second layer of photoresist are positioned so that any milling of the target area will result in boundaries milled through photoresist despite beam shifting.  
     
     
         10 . The method of  claim 1 , wherein the second layer includes at least one fiducial mark for aligning the orientation of the milling device.  
     
     
         11 . The method of  claim 10 , wherein the fiducial mark is also used to set up the milling device to correct for focusing, astigmatism and magnification errors.  
     
     
         12 . The method of  claim 1  wherein the milling device is a focused ion beam.  
     
     
         13 . A recording head made by the method of  claim 1 .  
     
     
         14 . Magnetic recording media written by a head made by the method of  claim 1 .  
     
     
         15 . The method of  claim 1 , further comprising depositing a layer of conductive material over the first and the second layer of the photoresist.  
     
     
         16 . The method of  claim 15  wherein the conductive material is metal.  
     
     
         17 . The method of  claim 16  wherein the metal is FeNi.  
     
     
         18 . The method of  claim 1 , wherein the target area is a general representation of a pattern to be milled.  
     
     
         19 . The method of  claim 1 , wherein the target area is an identifiable mark to provide an origin for a coordinate system.  
     
     
         20 . The method of  claim 19  wherein the milled pattern is determined with respect to the identifiable mark based on the coordinate system.  
     
     
         21 . A method comprising: 
 depositing a first layer of photoresist over an upper surface of a substrate of a partially formed magnetic recording head having a magnetically permeable thin film defining at least a portion of the upper surface;    depositing a second layer of photoresist over a portion of the first layer of photoresist, wherein the second layer defines a gap pattern to be milled to form a timing based writing gap through the thin film;    aligning a milling device to the defined gap pattern; and    milling the gap pattern.    
     
     
         22 . The method of  claim 21 , further comprising hard baking the first layer of photoresist.  
     
     
         23 . The method of  claim 21 , wherein a portion of the upper surface remains uncovered by the first layer of photoresist so the that milling device can be grounded to the upper surface.  
     
     
         24 . The method of clam  21  wherein the alignment occurs visually.  
     
     
         25 . The method of  claim 21  wherein the alignment occurs based on pattern recognition.  
     
     
         26 . The method of  claim 21  wherein milling the gap includes using a focused ion beam.  
     
     
         27 . The method of  claim 21  wherein the alignment occurs based on numerical coordinates and a determined origin.  
     
     
         28 . The method of  claim 21 , wherein milling includes milling boundaries and each boundary is milled through photoresist.  
     
     
         29 . The method of  claim 28 , wherein each boundary is milled through photoresist despite any beam shift that occurs during milling.  
     
     
         30 . The method of  claim 21 , wherein depositing the second layer includes providing multiple independent portions of the second layer, wherein each independent portion includes a defined gap pattern to be milled.  
     
     
         31 . The method of  claim 21 , wherein depositing the second layer includes providing an independent fiducial mark.  
     
     
         32 . The method of  claim 21 , further comprising depositing a layer of conductive material over the first and the second layer of the photoresist.  
     
     
         33 . The method of  claim 32  wherein the conductive material is metal.  
     
     
         34 . The method of  claim 33  wherein the metal is Fe Ni.  
     
     
         35 . The method of  claim 21 , wherein the deposited second layer includes a general representation of a pattern to be milled.  
     
     
         36 . A recording head made by the method of  claim 21 .  
     
     
         37 . Magnetic recording media written by a head made by the method of  claim 21 .  
     
     
         38 . The magnetic recording media of  claim 37  wherein the recording media is tape.  
     
     
         39 . A method comprising; 
 depositing a first layer of photoresist over an upper surface of a substrate of a partially formed multi-channel magnetic recording head having a magnetically permeable thin film defining at least a portion of the upper surface;    forming the first layer of photoresist by soft baking the first layer of photoresist;    depositing photoresist alignment patterns on top of the first layer of photoresist and over a subgap of each channel, wherein the alignment patterns define timing based gap patterns over each subgap to be milled;    depositing at least one photoresist fiducial in an area between channels;    adjusting a focused ion beam based on the fiducial to orientate and adjust the focused ion beam relative to the substrate;    aligning the focused ion beam visually to one alignment pattern; and    milling the gap patterns through the thin film wherein any boundary milled is milled through photoresist regardless of beam shift.    
     
     
         40 . A recording head made by the method of  claim 39 .  
     
     
         41 . Magnetic recording media written by a head made by the method of  claim 39 .  
     
     
         42 . The magnetic recording media of  claim 41  wherein the recording media is tape.  
     
     
         43 . A substrate for forming a magnetic recording head comprising: 
 a first magnetically permeable member;    a second magnetically permeable member;    a generally magnetically impermeable member disposed between the first and second magnetically permeable members forming a head substrate and defining a subgap area on one surface of the head substrate;    a magnetically permeable thin film disposed over at least the subgap area;    a first layer of photoresist deposited over at least a portion of the one surface and covering at least a portion of the subgap area;    an alignment pattern formed from a second layer of photoresist deposited over the first layer of photoresist, wherein the alignment pattern defines writing gaps to be milled over the subgap area and the alignment pattern is positioned so that boundaries defined during milling of the writing gaps are defined through photoresist regardless of beam shift.    
     
     
         44 . The substrate of  claim 43 , further comprising a fiducial pattern for alignment of a milling device and formed from a layer of photoresist deposited on top of the first layer of photoresist.  
     
     
         45 . The substrate of  claim 43  wherein the substrate comprises a plurality of channels and a separate alignment pattern is provided for each channel.  
     
     
         46 . The substrate of  claim 43  wherein the alignment pattern defines an origin for a coordinate system.  
     
     
         47 . The substrate of  claim 43  further comprising a conductive layer over the first and the second layers of photoresist.  
     
     
         48 . The substrate of  claim 47  wherein the conductive layer is metal.  
     
     
         49 . The substrate of  claim 48  wherein the metal is FeNi.  
     
     
         50 . The substrate of  claim 43  wherein the alignment pattern is approximately representative of a pattern to be milled.  
     
     
         51 . A method comprising: 
 providing a first masking layer on a substrate;    providing a second masking layer on an upper surface of the first masking layer to define a target area; and    milling the target area with a milling device.    
     
     
         52 . The method of  claim 51 , wherein the substrate includes a thin film on at least a portion of an upper surface of the substrate, wherein the first masking layer is provided over at least a portion of the thin film.  
     
     
         53 . The method of  claim 51 , wherein the first masking layer is provided over substantially all of an upper surface of the substrate.  
     
     
         54 . The method of  claim 51 , wherein the first masking layer is provided over substantially all of an upper surface of the substrate except for at least one predefined area of the substrate that is exposed to provide grounding for the milling device.  
     
     
         55 . The method of  claim 51  wherein the second masking layer includes a plurality of target areas each defined by an independent portion of the second layer.  
     
     
         56 . The method of  claim 51 , wherein the second masking layer defines a writing gap for a magnetic recording head.  
     
     
         57 . The method of  claim 51 , wherein the second masking layer defines a timing based writing gap for a magnetic recording head.  
     
     
         58 . The method of  claim 51 , wherein the first and second masking layers are positioned so that any milling of the target area will result in boundaries milled through a masking layer despite beam shifting.