Areal Density Improvement of Perpendicular Magnetic Recording (PMR) Write Head by Tuning Magnetic Flux Loops

• US 20170148473A1
• Filed: 11/20/2015
• Published: 05/25/2017
• Est. Priority Date: 11/20/2015
• Status: Active Grant

• Current Assignee: Headway Technologies Incorporated (TDK Corporation)
• Original Assignee: Headway Technologies Incorporated (TDK Corporation)
• Inventors: Wei, Yaguang, Tang, Yuhui, Dovek, Moris, Liu, Yue
• Granted Patent: US 9,754,612 B2
• Time in Patent Office: Days
• CPC Class Codes: G11B 5/1278 specially adapted for magnetisations perpendicular to the surface of the record carrier
• CPC Class Codes: G11B 5/3116 Shaping of layers, poles or gaps for improving the form of the electrical signal transduced, e.g. for shielding, contour effect, equalizing, side flux fringing, cross talk reduction between heads or between heads and information tracks G11B5/3113, G11B5/245 take precedence
• CPC Class Codes: G11B 5/3123 by using special coil configurations or conductors
• CPC Class Codes: G11B 5/315 Shield layers on both sides of the main pole, e.g. in perpendicular magnetic heads

Abstract

A PMR writer is disclosed wherein magnetic flux return from a magnetic medium to a main pole is substantially greater through a trailing shield structure than through a leading shield and return path layer (RTP). Magnetic impedance is increased between the RTP and main pole in the leading return loop by modifying the size and shape of the back gap connection (BGC), by decreasing Bs in the RTP or reducing its thickness, or by removing one or more layers in the BGC and replacing with dielectric material or non-magnetic metal to form a dielectric gap between the RTP and main pole. As a result, area density control and bit error rate are improved over a conventional dual write shield (DWS) structure comprising two flux return pathways. Moreover, adjacent track erasure is maintained at a level similar to a DWS design.

Claims

1. A PMR writer, comprising:

(a) a first trailing shield layer formed on a write gap and adjoining an air bearing surface (ABS), the write gap contacts a top surface of a front portion of a main pole layer at the ABS;

(b) a second (PP3) trailing shield that adjoins a top surface of the first trailing shield layer and extends toward a back end of the PMR writer where the PP3 trailing shield contacts a top yoke formed on a top surface of a back portion of the main pole layer;

(c) a leading shield with a top surface contacting a bottom surface of a leading gap at the ABS, the leading gap has a top surface adjoining a bottom surface of the front portion of the main pole layer at the ABS;

(d) a leading shield connector (LSC) that contacts a bottom surface of the leading shield and extends from the ABS toward a back end of the PMR writer;

(e) a shield connector that is recessed from the ABS and adjoins a bottom surface of the LSC and a top surface of a return path layer (RTP);

(f) the RTP with an ABS facing side that is recessed from the ABS and with a top surface that is parallel to the main pole layer bottom surface; and

(g) a back gap connection (BGC) that is a via filled with a magnetic material and connects the top surface of the RTP to a bottom surface of the back portion of the main pole layer wherein a magnitude of magnetic flux in a return pathway from a magnetic medium through the leading shield, SLC, shield connector, RTP, and BGC to the main pole layer is substantially less than a magnitude of magnetic flux returning from the magnetic medium to the main pole layer through the first trailing shield and PP3 trailing shield.

2. The PMR writer of claim 1 wherein the back gap connection has a cross-sectional area from a top-down view of about 6 microns² or less.

3. The PMR writer of claim 1 wherein the back gap connection has a substantially long bar shape from a down-track view wherein two sides are formed parallel to the ABS or are aligned orthogonal to the ABS and are separated by a distance of about 1-2 microns.

4. The PMR writer of claim 1 wherein the RTP has a magnetization saturation value substantially less than 10 kG.

5. The PMR writer of claim 1 wherein the RTP has a thickness from about 0.4 to 0.6 microns.

6. The PMR writer of claim 2 wherein the RTP has a saturation magnetization value substantially less than 10 kG, or a thickness from about 0.4 to 0.6 microns.

7. The PMR writer of claim 3 wherein the RTP has saturation magnetization value substantially less than 10 kG or a thickness from about 0.4 to 0.6 microns.

8. The PMR writer of claim 4 wherein the magnetization saturation value is achieved by incorporating a non-magnetic element that is Hf, Zr, Nb, Mo, Ti, Cr in a magnetic alloy employed for the RTP.

9. A PMR writer, comprising:

(a) a first trailing shield layer formed on a write gap and adjoining an air bearing surface (ABS), the write gap contacts a top surface of a front portion of a main pole layer at the ABS;

(b) a second (PP3) trailing shield that adjoins a top surface of the first trailing shield layer and extends toward a back end of the PMR writer where the PP3 trailing shield contacts a top yoke formed on a top surface of a back portion of the main pole layer;

(c) a leading shield with a top surface contacting a bottom surface of a leading gap at the ABS, the leading gap has a top surface adjoining a bottom surface of the front portion of the main pole layer at the ABS;

(d) a leading shield connector (LSC) that contacts a bottom surface of the leading shield and extends from the ABS toward a back end of the PMR writer;

(e) a shield connector (S2C) that is recessed from the ABS and adjoins a bottom surface of the LSC and a top surface of a return path layer (RTP); and

(f) the RTP with an ABS facing side that is recessed from the ABS and with a top surface that is parallel to the main pole layer bottom surface, there is a dielectric gap between the RTP top surface and the main pole layer to prevent a magnetic connection therebetween such that a magnitude of magnetic flux in the RTP is substantially less than a magnitude of magnetic flux returning from the magnetic medium to the main pole layer through the first trailing shield and PP3 trailing shield.

10. The PMR writer of claim 9 wherein the dielectric gap comprises one or more of the following:

(a) a first insulation layer that contacts a top surface of the RTP and with an ABS facing side that adjoins a back side of the shield connector;

(b) a second insulation layer formed on the first insulation layer and wherein a bucking coil layer having a plurality of turns is formed, a top surface of the second insulation layer is coplanar with a top surface of the bucking coil layer and a top surface of the shield connector;

(c) a third insulation layer formed on the second insulation layer and with an ABS facing surface adjoining a back side of the LSC, and having a thickness in a down-track direction essentially equal to a thickness of the LSC; and

(d) a fourth insulation layer formed on the third insulation layer and with an ABS facing side adjoining a back side of the leading shield and a thickness in a down-track direction essentially equal to a thickness of the leading shield.

11. The PMR writer of claim 10 wherein the dielectric gap further comprises a non-magnetic metal formed in a portion of the second insulation layer, and between the back portion of the main pole layer and a back portion of the RTP.

12. The PMR writer of claim 9 wherein the leading shield, LSC, shield connector, and RTP are made of a magnetic material with a saturation magnetization value of about 10 kG to 16 kG.

13. The PMR writer of claim 9 wherein the PP3 trailing shield and an upper portion of the first trailing shield are made of a magnetic material with a saturation magnetization value of about 16 kG to 19 kG.

14. The PMR writer of claim 13 wherein the first trailing shield includes a lower portion contacting the write gap that is made of a hot seed layer with a saturation magnetization value greater than 19 kG.

15. The PMR writer of claim 9 further comprised of a bottom yoke that contacts a bottom surface of the main pole layer and has an ABS facing side that adjoins a back side of the leading gap.

16. The PMR writer of claim 11 wherein the non-magnetic metal is Cu and is not connected to the bucking coil layer in the second insulation layer.

17. A method of forming a PMR writer, comprising:

(a) forming a return path layer (RTP) with front side facing a first plane that is aligned in a down-track direction;

(b) forming a first insulation layer on a top surface of the RTP;

(c) forming a second insulation layer on the first insulation layer, and a bucking coil layer with a plurality of turns in the second insulation layer;

(d) forming a shield connector at the first plane such that the first insulation layer has a front side adjoining a lower back side portion of the shield connector that magnetically connects the RTP top surface to a bottom surface of a leading shield connector (LSC), the second insulation layer has a front side adjoining an upper back side portion of the shield connector, and a top surface that is coplanar with a top surface of the bucking coil layer and with a top surface of the shield connector;

(e) forming a third insulation layer on the second insulation layer, and the LSC in the third insulation layer at the first plane, a front side of the third insulation layer adjoins a back side of the LSC, and the third insulation layer has a down-track thickness essentially equal to a thickness of the LSC;

(f) forming a fourth insulation layer on the third insulation layer, and a leading shield in the fourth insulation layer at the ABS, the fourth insulation layer has a front side adjoining a back side of the leading shield, and has a down-track thickness essentially equal to a thickness of the leading shield;

(g) forming a main pole layer above the fourth insulation layer, a front portion of the main pole layer is separated from a top surface of the leading shield by a leading gap, and there is a dielectric gap comprised of one or more of the first through fourth insulation layers formed between a back portion of the main pole layer and a back portion of the RTP to prevent a magnetic connection between a top surface of the RTP and the main pole layer; and

(h) performing a lapping process to form an ABS along the first plane such that the main pole layer, leading shield, leading gap, and LSC have a front side at the ABS.

18. The method of claim 17 further comprised of forming a non-magnetic metal within a portion of the second insulation layer in the dielectric gap.

19. The method of claim 18 wherein the non-magnetic metal is copper.

20. The method of claim 17 wherein the leading shield, LSC, shield connector, and RTP are made of a 10 kG to 16 kG magnetic material.

21. The method of claim 17 further comprised of forming a trailing shield structure including a first trailing shield with a bottom surface contacting a top surface of a write gap, and with a top surface adjoining a bottom surface of a PP3 trailing shield, the write gap separates the first trailing shield and main pole layer at the ABS, and the PP3 trailing shield is magnetically connected to the back portion of the main pole layer through a top yoke.

22. The method of claim 21 wherein the first trailing shield is comprised of a lower hot seed layer made of a magnetic material with saturation magnetization greater than 19 kG, and an upper 16 kG to 19 kG magnetic layer.

23. The method of claim 18 wherein the non-magnetic metal is not electrically connected to the plurality of turns in the bucking coil layer.