RELATED PATENT APPLICATIONS

This application is related to the following: U.S. Pat. Nos. 10,418,054; 10,777,220; and 10,643,640; which are assigned to a common assignee and herein incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to a PMR write head configured to have a capacitive one turn (C1T) coil design where a capacitor (C_bot) is applied across the bottom (bucking) coil and is compatible with various base writer structures so that the writer behaves like a typical 1+1T writer at low frequency writing, but performs as a 1+0.xT writer at high frequency where the bucking coil contributes only a portion of its full power, and like a 1+0T writer in an overshoot region where the write current passes through the capacitor to shunt the bottom loop, thereby enabling better trailing shield gradient, signal to noise ratio (SNR), and bit error rate (BER) while maintaining saturation speed, adjacent track interference (ATI) and wide adjacent track erasure (WATE).

BACKGROUND

A PMR write head typically has a main pole layer with a small surface area (pole tip) at an ABS, and coils that conduct a current and generate a magnetic flux in the main pole such that the magnetic flux exits through the pole tip and enters a magnetic medium (disk) adjacent to the ABS. Magnetic flux is used to write a selected number of bits in the magnetic medium and typically returns to the main pole (MP) through two pathways including a trailing loop and a leading (bottom) loop. The trailing loop is comprised a trailing shield structure (TH1) with a front side at the ABS, and an uppermost (PP3) trailing shield (TS) that may be recessed from the ABS and arches over the driving coil to connect with a top yoke (TY). In some designs, the PP3 TS is exposed at the ABS for fewer process steps when WATE from the PP3 TS, and PP3 TS to TH1 is manageable, and a larger metal surface is exposed at the ABS to satisfy thermo-mechanical (T/M) requirements. The TY adjoins a top surface of the MP above a back gap connection (BGC). The trailing loop is also known as the top driving loop and delivers magnetic flux to the MP tip to write positive and negative field into magnetic media. The leading (bottom) loop has a leading shield with a side at the ABS and in some schemes is connected to a return path (RTP) having a front side recessed from the ABS. The RTP extends back to the BGC and enables magnetic flux in the leading loop pathway to return from the leading shield at the ABS and through the BGC to the MP.

Dual write shield (DWS) designs that feature complete leading and trailing loops were invented for faster saturation speed and better WATE by reducing stray field in side shields and in the leading shield and trailing shields. However, a non-DWS (nDWS) design where essentially all of the leading loop is removed except for the leading shield has proven beneficial in providing a better return field at the MP trailing edge thereby improving field gradient, BER, and ADC compared with a DWS scheme. At low frequency, a DWS design with a “strong” bottom loop will help write field strength and improve low frequency writability without trailing shield gradient trade off. At high frequency, however, a strong bottom loop may cause less flux return to the trailing shield (TS), worse TS field gradient, and a degradation in high frequency SNR and BER.

To achieve areal density in a hard disk drive (HDD) beyond 2 terabytes per platter (TBPP) for conventional PMR in near line applications, OD high data rate (HDR) performance up to 3.4 gigabytes per second (Gbps) or 1.7 gigahertz (GHz) is essential and critical. A one turn coil design (1+1T) with one turn in each of the bucking and driving coils has demonstrated better HDR performance than a two turn coil design (1+1+2T or 2+2T) because of less electrical inductance and a more compact magnetic loop with shorter yoke length (YL). Magneto-motive force (MMF) of a one turn coil design is half that of a 2+2T design. Under direct current (DC) or low frequency alternating current (AC) applications, a one turn coil writer requires two times the current of a two turn coil writer to drive a head to the same magnetic field level. However, under high frequency for HDR applications, the 1+1T design has demonstrated an advantage in reaching the same magnetic field level with 1.2-1.5 times the current of a two turn coil design for 1.75 TBPP applications with a data rate up to 3.1 Gbps (1.55 GHz). An improved 1+1T design was disclosed in related U.S. Pat. No. 10,643,640 with an ultimate double yoke (uDY) for the top yoke and with multiple base writer schemes that delivers a faster writer with a lower lw0-pk (0 to peak current) at outer diameter (OD) operation. However, a writer is needed with better trailing shield gradient, SNR, and BER while maintaining saturation speed, ATI and WATE during high frequency operation for an overall improvement in HDR performance.

SUMMARY

One objective of the present disclosure is to provide a PMR writer with a 1+1T coil layout that behaves like a 1+1T writer at low frequency, a 1+0.xT writer at high frequency, and a 1+0T writer in an overshoot region of the write scheme.

Another objective of the present disclosure is to provide a PMR writer according to the first objective that is compatible with various base writer designs.

A third objective of the present disclosure is to provide a method of fabricating a PMR writer that satisfies the first two objectives.

These objectives are achieved by configuring a PMR writer in a capacitive one turn (C1T) design wherein a C1T capacitor (C_bot) is applied across the bottom coil in a 1+1T coil scheme, and may have one electrode connected to the center tap (interconnect between top and bottom coils), and a second electrode connected to the bottom coil pad to shunt the bottom coil at high frequency. Optionally, the C1T capacitor may be formed below the reader in a combined read-write head but this scheme is not preferred because the capacitor needs to be built at the beginning of the head process before the reader, and vias are required to be built all the way up for connections to the center tap and bottom coil pad. The capacitance of the C1T capacitor is maintained from 0.1-1 nanoFarad (nF), and preferably from 0.1-0.5 nF for the 1+1T writers described in the embodiments of the present disclosure. The C1T capacitor is preferably comprised of a material such as TaOx, TiOx, TiO2, or Al doped TiO2(ATO) having a dielectric constant >10. The area and thickness of the C1T capacitor are adjusted to achieve the desired target capacitance. For example, a C1T capacitor made of TaOx and with a thickness ≤75 nm and an area ≥0.0155 mm2delivers a capacitance of around 50 pF (picoFarad).

In some embodiments, the writer may have a so-called ultimate double yoke (uDY) scheme where a top yoke (TY) extension is formed below the driving coil and has a down-track thickness equal to that of the TY back portion that is below the uppermost (PP3) trailing shield, and has a yoke length (YL) of 2 to 2.6 microns from the ABS to the TY front side. The TY extension front side is separated from a backside of the second trailing shield (TS) also known as the write shield (WS) by a dielectric layer. The uDY design enables faster saturation speed and improved ATI/WATE performance that is needed for 2TBPP applications.

The writer structure is not limited to a single PMR writer, but may also be incorporated in each writer of a selectable dual writer (SDW), or in each writer of a selectable triple writer (STW) on a slider. Writers in the SDW or STW schemes may have shared PP3 TS, WS, side shields (SS), and leading shields (LS), but a separate first TS (hot seed layer), TY/TY extensions, MP, tapered bottom yokes, and bottom yokes. The “selectable” aspect of a SDW or STW relates to selectively activating the writer with the better/best performance while the one or more other writers remain inactive during a write process.

The present disclosure also encompasses a method for fabricating a capacitor below a bottom coil in a PMR writer. The process flow begins by providing a first insulation layer above a RTP. A first photoresist mask is formed on the first insulation layer from the eventual ABS plane to a first height (h). Next, a bottom electrode layer (BE) is deposited on the first insulation layer and a BE front portion is aligned below where the center tap will eventually be deposited. After the first photoresist mask is removed, a second photoresist mask is formed from the ABS plane to a second height (h1) where h1>h so that the BE front portion is protected. Then, the C1T capacitor such as TiOx with a 500 Angstrom thickness, for example, and a top electrode layer (TE) are sequentially deposited on unprotected regions of the BE. The second photoresist mask is removed and then a third photoresist mask with openings corresponding to the desired bucking coil shape is formed on the first insulation layer, front BE portion, and on the BE/C1T capacitor/TE stack beyond the second height from the ABS plane. Thereafter, the bucking coil is plated and a chemical mechanical polish (CMP) process is performed to provide a planar top surface. A center portion of the bucking coil contacts the BE front portion, and in a subsequent step, the center tap will be deposited on the bucking coil center portion. Moreover, a back portion of the bucking coil (bucking coil lead) contacts the TE on the BE/C1T capacitor/TE stack. At this point, the third photoresist mask is removed and a well known process of record (POR) is followed to complete the writer structure. The method described above has the capacitor BE contacting the bottom coil below the center tap, and the capacitor TE contacting the bucking coil lead or pad. Although the bucking coil and capacitor have substantial overlap in the exemplary embodiment, they may have no overlap area in an alternative embodiment where a first lead connects the bucking coil center portion with the TE, and a second lead connects the BE and bucking coil pad.

