Patent Application
20100321835
Magnetic transducing heads typically include both a write element and a read element. The read element includes a magnetoresistive (MR), tunneling magnetoresistive (TMR) or giant magnetoresistive (GMR) element for reading information from a recording layer of a recording medium (e.g., a magnetic disc). The write element is configured to generate magnetic fields that align magnetic moments of the recording data to represent bits of data.
The write portion of a magnetic transducing head typically includes at least two poles, a main pole (or write pole) and at least one return pole. The main pole and return pole are separated by a gap layer at the surface facing the recording medium. The main pole and the return pole are connected to each other at a region distal from the recording medium by a back gap closer or back via. One or more layers of conductive coils are positioned between the main pole and the return pole, and are encapsulated by insulating layers.
To write data to the recording medium, an electric current is applied to the conductive coils to induce a magnetic field in the media under the main pole. By reversing the direction of the current through the coils, the polarity of the data written to the media is reversed, and a magnetic transition is written between two adjacent bits. The main pole defines the track width of the data written. More specifically, in perpendicular recording the magnetic signals are conducted through the trailing edge of the main pole in a manner that orients the magnetic moments of the recording medium perpendicularly to the surface of the recording media. The shape of the main pole is projected and reproduced on the magnetic medium during the write process. Thus, the track width is defined by the width of the main pole at the surface facing the recording medium (i.e. air bearing surface).
It is desired to increase the magnetic recording capacity of the media. One way to increase the recording capacity is to use smaller transitions (i.e. bits). In order to accommodate the smaller transitions, the width of the main pole at the medium confronting surface must also be reduced to increase the tracks per inch (TPI). At the same time, the field gradient of the main pole must be high so that the main pole can quickly switch the magnetic state of the magnetic medium. However, a smaller pole typically delivers a lower magnetic field and cannot write to hard media.
Additionally, side writing is another concern. Unwanted side writing may occur due to a change in skew angle as the transducing head travels in an arc across the magnetic medium. Side writing can cause adjacent track interference (ATI), which results in off track erasure of transitions recorded on the magnetic medium.
Side shields that extend the entire length of the main pole can be used to improve TPI by reducing the erase band. Side shields may be located adjacent to and spaced apart from the main pole and extend from the leading edge to the trailing edge of the main pole. Depending on their location, the magnetic material of these side shields may draw flux from the main pole, thus reducing the pole field of the main pole. Reduction in pole field is not a concern when the side shields are positioned far from the write pole, but the flux shunting becomes severe when the side shields are at a distance comparable to the distance between the main pole and the front shield. Such side shields degrade the recording ability of the main pole and a high quality signal cannot be achieved.
A magnetic writer includes a write pole, a first partial side shield and a second partial side shield. The write pole has a leading edge, a trailing edge, a first side and a second side. The first partial side shield is located on the first side of the write pole, and the second partial side shield is located on the second side of the write pole. The first partial side shield and the second partial side shield extend along side of the write pole from the trailing edge to a location intermediate that trailing edge and the leading edge so that the first partial side shield and the second partial side shield do not shield the leading edge.
Reader 12 and writer 14 can be multi-layered devices having featured formed by layered materials. In one example, as illustrated in
On reader 12, read gap 26 is defined on medium confronting surface 16 between terminating ends of bottom shield 22 and top shield 28. Read element 24 is positioned in read gap 26 adjacent medium confronting surface 16. Read gap 26 insulates read element 24 from bottom shield 22 and top shield 28. Read element 24 may be any variety of different types of read elements, such as a magnetoresistive (MR) element, a tunneling magnetoresistive (TMR) read element or a giant magnetoresistive (GMR) read element.
Transducing head 10 confronts magnetic medium 60 at medium confronting surface 16, such as an air bearing surface (ABS). Reader 12 and writer 14 are carried over the surface of magnetic medium 60, which is moved relative to transducing head 10 as indicated by arrow A such that main pole 34 leads second return pole 38 and trails first return pole 30. Writer 14 has leading edge 18 and trailing edge 20 defined by the movement of magnetic medium 60. Main pole 34 is used to physically write data to magnetic medium 60. In order to write data to magnetic medium 60, current is caused to flow through second conductive coil 42. The magnetomotive force in the coils causes magnetic flux to travel from main pole tip 48 through magnetic medium 60 to second return pole 38 and second magnetic stud 36 to provide a closed magnetic flux path. A similar process occurs for first conductive coil 40 and first return pole 30. The direction of the write field at the medium confronting surface of main pole tip 48, which is related to the state of the data written to magnetic medium 60, is controllable based on the direction that the current flows through second conductive coil 42.
Reader 12 reads data from magnetic medium 60. In operation, magnetic flux from a surface of magnetic medium 60 causes rotation of a magnetization vector of read element 24, which in turn causes a change in electrical resistivity of read element 24. The change in resistivity of read element 24 can be detected by passing a current through read element 24 and measuring a voltage across read element 24. Shields 22 and 28, which may be made of a soft ferromagnetic material, guide stray magnetic flux from medium layer 66 away from read element 24 outside the area of medium layer 66 directly below read element 24.
In writer 14, first return pole 30, second return pole 38, first magnetic stud 32, and second magnetic stud 36 can comprise soft magnetic materials, such as NiFe. Conductive coils 40 and 42 can comprise a material with low electrical resistance, such as Cu. Main pole body 46 can comprise a high moment soft magnetic material, such as CoFe. First magnetic stud 32 magnetically couples main pole 34 to first return pole 30, and second magnetic stud 36 magnetically couples main pole 34 to second return pole 38. First conductive coil 40 surrounds first magnetic stud 32 and passes through the gap between first return pole 30 and main pole 34. Similarly, second conductive coil 42 surrounds second magnetic stud 36 and passes through the gap between main pole 34 and second return pole 38.
Magnetic medium 60 is shown merely for purposes of illustration, and may be any type of medium that can be used in conjunction with transducing head 10, such as composite media, continuous/granular coupled (CGC) media, discrete track media, and bit-patterned media.
Reader 12 and writer 14 are shown merely for purposes of illustrating a construction that may be used in a transducing head 10 and variations on the designs may be made. For example, a single trailing return pole may be provided on writer 14 instead of the shown dual return pole writer configuration.
Partial side shields 70 are self-aligned in the cross-track direction, and are equally positioned on either side of main pole 48. Partial side shields 70 shield only a portion of main pole 48; partial side shields 70 do not extend the entire length of main pole 48. Main pole 48 has top pole length (TPL) Lp, and side shields 70 have side shield length Ls. First and second partial side shields 70a and 70b are spaced apart from main pole 48 by an equal distance labeled ds. Distance ds between side shields 70 and main pole 48 can also be referred to as the side shield gap. As illustrated, side shield length Ls is less than TPL Lp so that side shields 70 do not extend the entire length of main pole 48. In a specific example, side shield length Ls is about less than or equal to half of TPL Lp. In another example, side shield length Ls is between about 100 nm and 150 nm and TPL Lp is about 200 nm.
Partial side shields 70 can be at least partially enclosed by insulating layers or side shield gap material 74. Insulating layers 74 separate partial side shields 70 from main pole 48 and form part of the side shield gaps. Insulating layers 74 are formed from non-magnetic materials, such as but not limited to alumina, chromium and combinations thereof.
Spacers 76 extend along either side of main pole 48, and are located under or beneath partial side shields 70. Spacers 76 provide a step for partial side shields 70 to be built upon, and prevent partial side shields 70 from extending the entire length of main pole 48. Together, spacers 76 and partial side shields 70 extend the entire length of main pole 48. The length of partial side shields 70 can be controlled by adjusting the depth or thickness of spacers 76. Spacers 76 are formed from non-magnetic material 78. Seed layer 80 may partially surround non-magnetic material 78 of spacers 76. Seed layer 80 is formed of a conductive, non-magnetic material. Seed layer 80 provides a conductive layer on to which spacers 76 are plated. Spacers 76 do not adversely affect the magnetic signal from main pole 48 because spacers 76 are formed from non-magnetic material. Because magnetic material is only present in partial side shields 70 and not in spacers 76, and because partial side shields 70 extend only a portion of the length of main pole 48, main pole 48 has an improved pole field compared to a main pole having side shields which extend the entire length of the main pole.
Partial side shields 70 are located at trailing edge 20 of main pole 48. Partial side shields 70 at trailing edge 20 improve the tracks per inch (TPI) of the transducing head at low skew. Partial side shields 70 are formed from a magnetic material such as a nickel, cobalt or iron alloy having a high magnetic moment. The magnetic material of partial side shields 70 draw flux from main pole 48, thus reducing the pole field so that there is less magnetic signal to write to the magnetic medium. By only shielding a portion of main pole 48 with partial side shields 70, the pole field is improved as compared to a main pole having shields that extend the entire top pole length (TPL). Modeling has suggested that a main pole having partial side shields 70, which are located at trailing edge 20 and which extend about 50% of TPL, will improve the pole field by about 5-7% when compared to a main pole having side shields that extend the entire length of the TPL under the same current.
Relative to a full side shield, the partial side shield design gains write field at the expense of exposing the leading edge. At low skew conditions, partial side shields 70 increases TPI by reducing the erasure band of main pole 48. However, exposing leading edge at high skew conditions can lead to ATI (adjacent track interference). Therefore the concept of partial side shields is more attractive to recording systems in which skew and ATI are less of a concern.
Insulating layers or side shield gap material 82 partially surround magnetic material 72 and non-magnetic material 78. Insulating layers 82 are formed from non-magnetic materials, such as but not limited to alumina, chromium and combinations thereof. Insulating layers 82 separate main pole 48 from partial side shields 70. Insulating layers 82 together with insulating layers 74 form the side shield gaps between main pole 48 and partial side shields 70. Alternatively, insulating layers 74 may not be present so that the side shield gaps are formed only by insulating layer 82.
Write gap 84 is located on top of main pole 48. Write gap 84 is adjacent to main pole 48 and is opposite substrate 86. Write gap 84 separates main pole 48 at trailing edge 20 from other features that may be present on a writer, such as a front shield (not shown). Write gap 84 is formed from a non-magnetic material such as alumina, chromium (Cr) and combinations thereof.
Alumina layers 85 are located adjacent to partial side shields 70 and spacers 76 and opposite from main pole 48. Alumina layers 85 are non-magnetic. Alumina layers 85 insulate the sides of partial side shields 70.
First, as illustrated in
Write gap material 92 is a non-magnetic material such as alumina, chromium (Cr) and combinations thereof. First and second stop layer 94 and 98, respectively, are inductively coupled plasma (ICP) etch stop layers such that first and second stop layers 94 and 98 are not removed by ICP etching. In one example, first and second stop layers 94 and 98 are formed from chromium. Sacrificial layer 96 must have a low argon etch rate as will be described later. In one example, sacrificial layer 96 contains alumina or amorphous carbon (a-carbon). Hard mask material 100 is used to pattern write pole material 90 to shape main pole 48. In one example, hard mask material 100 is alumina. It should be noted that a transducing head is formed in layers. Therefore, substrate 86 contains previously formed layers of a transducing head.
The thickness of write pole material 90 determines the length of main pole 48 at the medium facing surface. Similarly, the thickness of write gap material 92 determines the length of write gap 84 (the distance between main pole 48 and the feature formed on top of main pole 48). In one example, write pole material 90 is about 200 nm thick, write gap material 92 is about 30 nm thick, first stop layer 94 is between about 10 nm and about 15 nm thick, second stop layer 98 is about 30 nm thick and hark mask material 100 is about 1 um thick. The thickness of sacrificial layer 96 is based upon the desired length of partial side shields 70 and the mill rates of several materials as will be explained below. In one example, sacrificial layer 96 is between about 20 nm and about 30 nm thick.
After layered structure 88 has been formed, a photolithography process is used to pattern hard mask material 100. Photolithography uses light to transfer a pattern from a photomask to a light sensitive photoresist on the surface of hard mask material 100. With the photoresist in place, hard mask material 100 is etched using inductively coupled plasma (ICP) etching. ICP etching will remove the selected areas of hard mask material 100 that are not covered with the photoresist. ICP etching will not remove second stop layer 98; ICP etching will only remove hard mask material 100.
Following ICP etching of hard mask material 100, the exposed second stop layer 98 is removed using an ion milling technique. Based on the pattern formed in hard mask material 100, the ion milling will remove selected portions of second stop layer 98, sacrificial layer 96, first stop layer 94, write gap material 92, write pole material 90 and substrate 86. As illustrated in
As shown in
Plating of non-magnetic material 78 results in an uneven or mushroom shaped top surface. The write element is planarized to level the surface. In one example, write element can be planarized using chemical-mechanical planarization (CMP) until second stop layer 98 is reached. The polishing time of the CMP process is calculated such that the write element is polished down to second stop layer 98. Second stop layer 98 creates a level surface on the write element at a predetermined distance from the top of main pole 48. The predetermined distance may be adjusted by adjusting the thicknesses of second stop layer 98 and, additionally or alternatively, the thickness of at least one of the layers below second stop layer 98 (i.e. sacrificial layer 96, first stop layer 94).
Next, as shown in
The mill rate difference determines the thickness of sacrificial layer 96 deposited on substrate 86. In one example, the ratio of the thickness of sacrificial layer 96 to the desired depth of cavities 104 (and thus the length of partial side shields 70) is 1:5. In this case, sacrificial layer 96 having a thickness between 20 nm and 30 nm will produce cavities 104 having a depth between 100 nm and 150 nm, respectively. The described milling process does not require additional patterning of the substrate to form cavities 104, eliminating the possibility of misalignment of partial side shields 70. The resulting partial side shields 70, which are deposited in cavities 104, are self-aligned in the cross track direction.
Next, as illustrated in
After partial side shields 70 are formed, the write element can be backfilled and planarized down to sacrificial layer 96. Planarization levels deposited insulating layer 74 and magnetic material 72 at the surface.
Next, as shown in
The write element can be subjected to downstream processing, such as the formation of a front shield on top of write pole 48, at any time after sacrificial layer 96 and first stop layer 94 have been removed. Alternatively, first stop layer 94 may be left on write pole 48 as a control layer during further downstream processing.
In summary, as shown in
In step 122, a layered structure is formed. As described above, layered structure 88 can be formed by depositing write pole material 90 on substrate 86, followed by write gap material 92, first stop layer 94, sacrificial material 96, second stop layer 98 and hard mask material 100. Next, in step 124, the layered structure is patterned. For example, layered structure 88 can be patterned by using a photolithography process to transfer a pattern hard mask material 100, followed by an etching technique, such as IPC etching, to remove selected areas of hard mask material 100 not covered with the photoresist.
After the layered structure is patterned, selected portions of the layered structure are removed in step 126 to form a main or write pole and recesses. As described above, based on the pattern of hard mask material 100, ion milling can be used to remove selected portions of write pole material 90, write gap material 92, first stop layer 94, sacrificial material 96 and second stop layer 98 to form main pole 48, which has recesses 102 on either side.
Next, in step 128, non-magnetic material is deposited in the recesses. Deposition of the non-magnetic material can include depositing an insulating layer, such as insulating layer 82, and a seed layer, such as seed layer 80, in the recesses, followed by plating of a non-magnetic material, such as non-magnetic material 78. After depositing the non-magnetic material in the recesses, the write element is planarized to create a level or flat surface in step 130.
In step 132, selected portions of the non-magnetic material are removed to form cavities in the recesses. For example, as described above, non-magnetic material 78 can be removed by ion milling, and the length of the milling process and the milling rates of the materials determine the length of partial side shields 70.
In step 134, partial side shields are deposited in the cavities. Deposition of the partial side shields can include depositing an insulating layer, such as insulating layer 74, and magnetic material, such as magnetic material 72, in the cavities, such as cavities 104. Alternatively, deposition of the partial side shields can include only depositing magnetic material so that the partial side shields do not include the insulating layer. The write pole has a leading edge and a trailing edge. The partial side shields are deposited between a location intermediate the trailing edge and the leading edge of the write pole and the trailing edge of the write pole so that the partial side shields do not shield the leading edge of the write pole.
Finally, the write element is backfilled and planarized in step 136, and selected layers of layered structure 88 are removed in step 38. For example, sacrificial layer 96 and first stop layer 94 can be removed by IPC etch. In another example, residual write pole material 106 and residual write gap material 108 can be removed by ion etching.
The method described above provides a controllable step height upon which self-aligning (in the cross-track direction) partial side shields 70 are built. Partial side shields 70 are built upon features formed during the formation of main pole 48 such that a second photoresist patterning to define partial side shields 70 is not used. Sacrificial layer 96 protects desired features on the write element, and allows cavities 104 to be milled without an additional patterning process, thus eliminating the potential for misalignment of cavities 104 and partial side shields 70. The resulting partial side shields 70 are uniform in shape and size and are symmetric about main pole 48.
Additionally, the method provides control of length Ls of partial side shields 70. Length Ls of partial side shields 70 with respect to length Lp of main pole 48 may be adjusted according to different design criteria by adjusting the milling time, the mill rate difference between non-magnetic material 78 and sacrificial layer 96 and the thickness of the layers deposited on substrate 86, such as sacrificial layer 96. In one example, partial side shields 70 extend along side of main pole 48 from trailing edge 20 to an intermediate point located between trailing edge 20 and leading edge 18. In another example, partial side shields 70 extend from trailing edge 20 of main pole 48 and have length Ls about equal to or less than about half of length Lp of main pole 48. By providing partial side shields 70 at trailing edge 20 of main pole 48 and not covering main pole 48 at leading edge 18, the pole field is improved, as compared to side shields that extend the entire length of the main pole under the same current. The resulting main pole 48 has an improved tracks per inch (TPI) at low skew.
The method also provides a well controlled space between partial side shields 70 and main pole 48 (illustrated in
Further, the method provides a self-aligned writer gap 84 on top of main pole 48. By layering write gap material 92 on write pole material 90 and sacrificial layer 96 on write gap material 92, writer gap 84 may be defined at the same time as main pole 48. Additionally, writer gap 84 is present during the formation of partial side shields 70 so that partial side shields 70 may be formed immediately adjacent to writer gap 84 (i.e. there is no disconnect between partial side shields 70 and write gap 84).
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.
