DETAILED DESCRIPTION

[0027] Although the following detailed description contains many specifics for the purposes of illustration, anyone of ordinary skill in the art will appreciate that many variations and alterations to the following details are within the scope of the invention. Accordingly, the following preferred embodiment of the invention is set forth without any loss of generality to, and without imposing limitations upon, the claimed invention.

[0028] A preferred configuration of a first embodiment of the present invention is shown in FIG. 2 , which is a cross-sectional schematic diagram of a MR sensing head 200 . The MR sensing head 200 includes a CIP sensor 226 on the bottom, a longitudinal bias stack 230 on the top and an insulating layer 218 separating the CIP sensor 226 and the longitudinal bias stack 230 . The CIP sensor 226 includes a ferromagnetic free layer 212 on the top, a ferromagnetic pinned layer 208 , a spacer layer 210 between the ferromagnetic pinned layer 208 and the ferromagnetic free layer 212 , and an anti-ferromagnetic (AFM) layer 206 adjacent to the ferromagnetic pinned layer 208 . The longitudinal bias stack 230 includes a ferromagnetic bias layer 220 and an AFM bias layer 222 . The MR sensing head 200 further includes two abutted leads 228 located on both sides of the CIP sensor 226 , a bottom gap 204 between the AFM layer 206 and a bottom shield 202 , and a top gap 224 located on top of the AFM bias layer 222 of the longitudinal bias stack 230 .

[0029] The ferromagnetic free layer 212 is about 20 Å-50 Å thick and typically contains Ni, Fe, Co or their alloys. The ferromagnetic pinned layer 208 is about 10 Å-50 Å thick and typically contains Co or CoFe. The spacer layer 210 is 10 Å-30 Å thick and typically contains Cu and its alloys. The AFM layer 206 is about 50 Å-200 Å thick and typically contains an alloy consisting of Mn, such as NiMn, IrMn, PtMn, or FeMn. Two abutted leads 228 are typically made of conducting materials, such as Ta, Al, Au, W, Ru, Rh, Ti and Pt, with thicknesses between 20 Å and 400 Å. Bottom shield 202 is typically made of ferromagnetic material, such as NiFe, NiFeCo, FeN, and FeAlSi with a thickness of 0.5 μm-3 μm. The bottom and top gaps 204 and 224 are typically made of alumina. The thickness of the bottom gap 204 is between 20 Å and 300 Å.

[0030] The ferromagnetic bias layer 220 is about 20 Å-50 Å thick and typically contains Co or CoFe, and the AFM bias layer 222 is about 30 Å-200 Å thick and typically contains an alloy consisting of Mn, such as NiMn, IrMn, PtMn, or FeMn.

[0031] The insulating layer 218 is typically made of metal oxide, such as oxide of Al, Ta, Ni, or NiFe and contains a first insulating portion 214 on top of the CIP sensor 226 and second insulating portions 216 on top of the abutted leads 228 . The insulating layer 218 electrically isolates the ferromagnetic free layer 212 from the longitudinal bias stack 230 , and thus the leads 228 do not make direct electrical contact to the longitudinal bias stack 230 . As a result, the effect of the current shunted by the longitudinal bias stack 230 is greatly reduced, thus the signal response for the CIP sensor 226 is enhanced. The first insulating portion 214 has an effective barrier resistance of greater than 200 Ω-μm ² , so a good electrical isolation between the ferromagnetic free layer 212 and the ferromagnetic bias layer 220 can be achieved. In addition, for in-stack bias to work, i.e., for the interlayer magnetostatic coupling field from the ferromagnetic bias layer 220 to interact effectively with the ferromagnetic free layer 212 , the separation between the ferromagnetic free layer 212 and the ferromagnetic bias layer 220 must be small. Typically, the thickness of the first insulating portion 214 is between 2 Å and 100 Å. The second insulating portions 216 are thicker than the first insulating portion 214 . The thickness of the second insulating portions 216 is between 30 Å and 600 Å. Since the second insulating portions 216 are thick, these portions can serve as part of the top gap 224 . Therefore, the thickness of the top gap 224 can be reduced significantly, which is inherent with a potential narrow gap capability. Typically, the thickness of the top gap is between zero and 300 Å.

[0032] It is known that achieving single domain stability for the ferromagnetic free layer 212 necessitates simultaneously achieving single domain stability in the ferromagnetic bias layer 220 . This occurs through their mutual interaction, which includes both interlayer magnetostatic coupling and edge magnetostatic coupling. Since the interlayer magnetostatic coupling field H _F is usually opposite to the edge magnetostatic coupling field H _D , one way to maximize the net longitudinal bias field H _bias is to minimize the edge magnetostatic coupling field H _D . By making the edges of the ferromagnetic bias layer 220 far away from the edges of the ferromagnetic free layer 212 , the edge magnetostatic coupling field H _D will be reduced to approximately zero. As shown in FIG. 2 , the width along the off-track direction of the ferromagnetic bias layer 220 , or the width of the longitudinal bias stack 230 , is greater than the width along the off-track direction of the ferromagnetic free layer 212 , or the track-width of the CIP sensor 226 . Typically, the track-width of the CIP sensor 226 is between 0.1 μm and 0.4 μm, and the width of the longitudinal bias stack 230 is greater than 0.5 μm.

[0033] The CIP sensor 226 of the MR sensing head 200 has the ferromagnetic free layer 212 on top of the sensor. It is known that the signal (e.g., ΔR/R) of CIP sensors strongly depends on their underlayer properties, such as grain size and interfacial smoothness. Therefore, the signal response of the CIP sensors can be maximized by optimizing the underlayer properties.

[0034] FIG. 3A is a graph showing the interlayer magnetostatic coupling H _F as a function of the resistance R _j , where R _j is defined as a product of the resistance and the area of the first insulating portion 214 . As shown in FIG. 3 A, an interlayer magnetostatic coupling field H _F of 160 Oe can be obtained with a large R _j of 4000 Ω-μm ² . As R _j increases to 50 kΩ-μm ² , a large H _F of 70 Oe can still be achieved. It indicates that the first insulating portion 214 can be used to apply a substantial and controllable longitudinal bias to the ferromagnetic free layer 212 via H _F while the amount of the current shunting by the longitudinal bias stack 230 is negligible because of its large R _j . Furthermore, the large increment of the H _F does not necessarily degrade the soft magnetic properties of the ferromagnetic free layer 212 . As shown in FIG. 3 B, the measured coercivity Hc _free of the ferromagnetic free layer 212 actually remains relatively small, only 12 Oe with 160 Oe of H _F .

[0035] FIG. 4 is a graph showing a micromagnetic model for the CIP sensor 226 with 0.1 μm track-width and a total gap of 0.065 μm. The CIP sensor is stabilized by an interlayer magnetostatic coupling H _F of 140 Oe. The micromagnetic model proves that a uni-directional force created by surface charges, such as H _F and direct exchange coupling, can be used to stabilize the ferromagnetic free layer as long as the amount of the interlayer magnetostatic coupling field is sufficiently large.

[0036] A series of the steps of a process for making the MR sensing head of the type depicted in FIG. 2 are shown in FIGS. 5 A- 5 H. As shown in FIG. 5A, a CIP sensor stack 500 is first deposited. The CIP sensor stack 500 includes a ferromagnetic free layer 512 on the top, a ferromagnetic pinned layer 508 , a metal spacer layer 510 between the ferromagnetic free layer 512 and the ferromagnetic pinned layer 508 , and an anti-ferromagnetic (AFM) layer 506 adjacent to the ferromagnetic pinned layer 508 . The CIP sensor stack 500 further includes a protecting layer or cap 514 adjacent to the ferromagnetic free layer 512 , a bottom gap 504 between the AFM layer 506 and a bottom shield 502 . All layers of the CIP sensor stack 500 are preferably deposited by typical vacuum deposition techniques, such as ion beam deposition, RF or DC magnetron sputtering deposition, evaporation deposition, or MBE deposition.

[0037] The CIP sensor stack 500 is then patterned using a photoresist mask 516 to define a track-width of the CIP sensor 501 as shown in FIG. 5B . The materials in the unmasked regions 518 of the CIP sensor stack 500 are removed using subtractive techniques, such as ion beam milling, chemically-assisted ion beam milling, sputter etching, or reactive ion etching with the endpoint terminating within the bottom gap 504 as shown in FIG. 5C . The unmasked regions 518 are then deposited with leads 520 , which preferably have shallow angle, as shown in FIG. 5D . The deposition of leads can be done using typical vacuum deposition techniques as described above. As shown in FIG. 5D, a quantity of leads 519 is also deposited onto the top and sidewalls of the photoresist mask 516 .

[0038] As shown in FIG. 5 E, thick oxide layers 522 , such as alumina, are deposited on top of leads 520 , and a quantity of oxide 523 is also deposited onto the top of the leads 519 . However, the quantities of leads 519 and oxide 523 are removed along with the photoresist mask 516 in a subsequent lift-off process. Alternatively, the thick oxide layers can be formed by heavily oxidizing upper portions of the leads 520 . In this case, the upper portions of leads 520 preferably contain metals that can be easily oxidized, such as Al, Ta, Ni and NiFe, and thus, the leads 520 may contain a bilayer or a trilayer of metals, such as Ta/Au/Ta or Ta/Au/Al.

[0039] As shown in FIG. 5 F, the photoresist mask 516 is removed in a lift-off process. The cap 514 is then removed using subtractive techniques, followed by re-deposition of a thin layer 524 of metals that can be easily oxidized, such as Al and Ta, on top of the ferromagnetic free layer 512 . Alternatively, the thin layer 524 can be formed by direct deposition of metal oxides. The thin metal layer 524 is then oxidized by plasma, thermal or air oxidation to form a highly resistive oxide barrier layer 526 on top of the CIP sensor 500 as shown in FIG. 5G . Alternatively, the cap layer 514 is not removed from the CIP sensor stack, and the highly resistive oxide barrier layer 526 is formed by oxidizing the cap layer 514 .

[0040] As shown in FIG. 5H, a longitudinal bias stack 528 is deposited on the thick oxide layer 522 and thin oxide layer 526 , and a top gap 530 of insulating materials is deposited on the longitudinal bias stack 528 . The top gap 530 can be extremely thin since the thick oxide layers 522 can serve as part of the top gap 530 . The longitudinal bias stack 528 includes a ferromagnetic bias layer 532 and an AFM bias layer 534 .

[0041] FIGS. 5 I- 5 L show the steps of a process for patterning the stripe height and the stitch leads of the MR sensing head formed in the step of FIG. 5H . The stripe height of the MR sensing head is first defined (not shown). The stitch leads are then defined using a photoresist mask 536 , and materials in the unmasked regions are removed using subtractive techniques with the endpoint going through the thick oxide layer 522 as shown in FIG. 5I . Thin insulation layers 538 , such as alumina, are deposited on the leads 520 , and the photoresist mask 536 is removed as shown in FIG. 5J . Another photoresist mask 540 is deposited on top of the MR sensing head and the insulation layers 538 , and the material of the insulation layers 538 in the unmasked regions are removed using subtractive techniques as shown in FIG. 5K . Stitch leads 542 and insulation layers 544 are then deposited followed by the lift-off of the photoresist mask 540 as shown in FIG. 5L .

[0042] An alternative configuration of the first embodiment is shown in FIG. 6 A, which is a cross-sectional schematic diagram of a MR sensing head 600 . As shown in FIG. 6 A, MR sensing head 600 includes a CIP sensor 602 on the top, a longitudinal bias stack 606 on the bottom and an insulating layer 604 separating the CIP sensor 602 and the longitudinal bias stack 606 . The CIP sensor 602 includes a ferromagnetic free layer 614 at the bottom, a ferromagnetic pinned layer 618 , a nonmagnetic spacer layer 616 between the ferromagnetic free layer 614 and the ferromagnetic pinned layer 618 , and an AFM layer 620 adjacent to the ferromagnetic pinned layer 618 . The longitudinal bias stack 606 includes a ferromagnetic bias layer 612 and an AFM bias layer 610 . The MR sensing head further includes a protecting layer or cap 708 on top of the CIP sensor 602 , and oxide layers 622 and abutted leads 624 disposed on both sides of the CIP sensor 602 . The materials and thicknesses of layers of the MR sensing head 600 are similar to those of the MR sensing head 200 as described above.

[0043] Alternatively, a MR sensing head can include overlaid leads as shown in FIG. 6B . MR sensing head 601 includes a CIP senor 602 , a longitudinal bias stack 606 , an insulating layer 604 , cap 608 and oxide layers 622 similar to those of the MR sensing head 600 . MR sensing head 601 further includes insulating layers 623 disposed on both sides of the CIP sensor 602 and overlaid leads 625 located on top of the insulating layers 623 .

[0044] A process of making the MR sensing head of the type depicted in FIG. 6A is shown in FIGS. 7 A- 7 E. As shown in FIG. 7A, a layered structure 700 , which includes CIP sensor stack 702 on top of a longitudinal bias stack 704 and an insulating barrier layer 705 separating the CIP sensor stack 702 and the longitudinal bias stack 704 , is first deposited. The CIP sensor stack 702 includes a ferromagnetic free layer 706 on the bottom, a ferromagnetic pinned layer 710 , a non-magnetic spacer layer 708 between the ferromagnetic free layer 706 and the ferromagnetic pinned layer 710 , and an AFM layer 712 adjacent to the ferromagnetic pinned layer 710 . The CIP sensor stack 702 also includes a cap 714 on top of the AFM layer 712 . The longitudinal bias stack 704 includes a ferromagnetic bias layer 716 on top of an AFM bias layer 718 . All layers of the layered structure 700 are preferably deposited by typical vacuum deposition techniques as described above. The insulating barrier layer 705 can be formed by the deposition of a metal layer, such as Al, Ta, Ni or NiFe, and following by plasma, thermal or air oxidation to form a highly resistive barrier layer between the ferromagnetic bias layer 716 and the ferromagnetic free layer 706 .

[0045] The CIP sensor stack 702 is then patterned using a photoresist mask 720 to define a track-width of the CIP sensor as shown in FIG. 7B . The materials in the unmasked regions 722 of the CIP sensor stack 702 are removed using subtractive techniques with the endpoint terminating within the spacer layer 708 or the ferromagnetic pinned layer 710 . As shown in FIG. 7 B, the endpoint terminates within the spacer layer 708 . The material in the remaining portions 724 of the spacer layer 708 and portions of the ferromagnetic free layer 706 in the unmasked regions is controllably oxidized as shown in FIG. 7C . Oxidation is required because it would be virtually impossible to do an ion milling that stops in the insulating barrier layer 705 .

[0046] Leads 726 are then deposited in the unmasked regions 722 as shown in FIG. 7D . The deposition of leads 726 can be done using typical vacuum deposition techniques. As shown in FIG. 7D, a quantity of leads 725 is also deposited onto the top and sidewalls of the photoresist mask 720 . However, this quantity of leads is removed along with the photoresist mask 720 in a lift-off process as shown in FIG. 7E . If lead overlay designs, as shown in FIG. 6 B, are used, the insulating layers, such as alumina, are deposited in the unmasked regions after the oxidation followed by a second lithography step to form the leads. An advantage of this method is that the formation of the MR sensing head is achieved with an in-situ deposition of the layers of the CIP sensor and the longitudinal bias structure.

[0047] In a second embodiment of the present invention, the MR sensing heads of the types depicted in FIGS. 2 and 6 A- 6 B are incorporated in the disk drive systems 800 as shown in FIG. 8 . Disk drive 800 includes a magnetic recording disk 802 connected to a motor 804 and MR sensing head 806 connected to an actuator 808 . The motor 804 spins the magnetic recording disk 802 with respect to the MR sensing head 806 . The actuator 808 moves the MR sensing head 806 across the magnetic recording disk 802 so the MR sensing head 806 may access different regions of magnetically recorded data on the magnetic recording disk 802 .

[0048] It will be clear to one skilled in the art that the above embodiment may be altered in many ways without departing from the scope of the invention. Accordingly, the scope of the invention should be determined by the following claims and their legal equivalents.