Microwave assisted magnetic recording head with trailing shield heat sink

A magnetic write head having a heat sink structure located adjacent to a trailing magnetic shield. The heat sink structure prevents heat generated by the magnetic oscillator current from causing damage to and reducing reliability of the magnetic write head. The trailing magnetic shield is substantially aligned with the magnetic oscillator, allowing the heat sink structure to wrap around the sides and back of the trailing magnetic shield and to provide good heat conduction away from the write pole, magnetic oscillator and trailing magnetic shield. The heat sink structure can be constructed of a material such as Ru, TiN, Cu, Au, Ag and AlN, and is preferably constructed of Au, which has excellent thermal properties.

FIELD OF THE INVENTION

The present invention relates to magnetic data recording and more particularly to a microwave assisted magnetic recording head having a trailing shield heat sink structure for dissipating heat produced by electrical current flowing through a spin torque oscillator.

BACKGROUND

At the heart of a computer is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk and an actuator that swings the suspension arm to place the read and write heads over selected tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating, but when the disk rotates air is swirled by the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic impressions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.

The write head includes at least one coil, a write pole and one or more return poles. When current flows through the coil, a resulting magnetic field causes a magnetic flux to flow through the coil, which results in a magnetic write field emitting from the tip of the write pole. This magnetic field is sufficiently strong that it locally magnetizes a portion of the adjacent magnetic media, thereby recording a bit of data. The write field then, travels through a magnetically soft under-layer of the magnetic medium to return to the return pole of the write head.

A magnetoresistive sensor such as a Giant Magnetoresistive (GMR) sensor or a Tunnel Junction Magnetoresistive (TMR) sensor can be employed to read a magnetic signal from the magnetic media. The magnetoresistive sensor has an electrical resistance that changes in response to an external magnetic field. This change in electrical resistance can be detected by processing circuitry in order to read magnetic data from the magnetic media.

SUMMARY

The present invention provides a magnetic write head that includes a magnetic write pole, a trailing magnetic shield and a magnetic oscillator located between the trailing magnetic shield and the write pole. A heat sink structure is formed adjacent to the trailing magnetic shield so as to conduct heat away from the trailing magnetic shield.

The trailing magnetic shield can be formed with a columnar shape that has first and second laterally opposed sides and a back side that is opposite the media facing surface, and wherein the first and second sides and back side are all substantially aligned with the magnetic oscillator. The heat sink structure can be constructed of a material having a thermal conductivity of at least 4.0 E+08 pWum° C. such as Ru, TiN, Cu, Au, Ag or AlN and is preferably constructed of Au, which has good thermal conductivity.

The heat sink structure, located adjacent to the trailing magnetic shield advantageously conducts heat away from the trailing magnetic shield and also from the magnetic oscillator and write pole while also allowing the write pole to be properly insulated by a non-magnetic, electrically insulating side gap material.

These and other features and advantages of the invention will be apparent upon reading of the following detailed description of the embodiments taken in conjunction with the figures in which like reference numeral indicate like elements throughout.

DETAILED DESCRIPTION

Referring now toFIG. 1, there is shown a disk drive100. The disk drive100includes a housing101. At least one rotatable magnetic disk112is supported on a spindle114and rotated by a disk drive motor118. The magnetic recording on each disk may be in the form of annular patterns of concentric data tracks (not shown) on the magnetic disk112.

During operation of the disk storage system, the rotation of the magnetic disk112generates an air bearing between the slider113and the disk surface122, which exerts an upward force or lift on the slider. The air bearing thus counter-balances the slight spring force of the suspension115and supports the slider113of and slightly above the disk surface by a small, substantially constant spacing during normal operation.

FIG. 2shows a side, cross sectional view of a magnetic head200that includes a read head202and a write head204. The read head202can include a magnetic sensor206such as a giant magnetoresistive (GMR) sensor or tunneling magnetoresistive (TMR) sensor that can be sandwiched between lower and upper magnetic shields208,210. The space between the read head202and write head204can be filled with a non-magnetic, electrically insulating material such as alumina212, as can the space between the shields210,208behind the read sensor206.

The write head204can include a magnetic write pole214that can extend to a media facing surface MFS. The magnetic write head204can also include a magnetic return pole216that can be magnetically connected with the write pole214at a region removed from the media facing surface MFS by a magnetic back gap layer218and optional magnetic shaping layer220. A magnetic trailing shield222can be located at the media facing surface MFS near the trailing edge of the write pole214, and can be connected with the back portion of the write head204by a trailing magnetic return pole224. The trailing magnetic shield222can be separated from the trailing edge of the write pole214by a magnetic oscillator230that will be discussed in greater detail herein below.

A non-magnetic, electrically conductive write coil226, shown in cross section inFIG. 2, can pass above and below the write pole214. The write coil226can be embedded in an electrically insulating, non-magnetic material such as alumina228. When an electrical current flows through the write coil226the resulting magnetic field causes a magnetic flux to flow through the write pole214. This results in a magnetic write field being emitted from the tip of the magnetic write pole214, The write field travels though the magnetic media (not shown inFIG. 2) and then returns to the return pole216and the trailing magnetic return pole224. Because the return poles216,224have a much larger cross section at the media facing surface MFS than does the write pole214, the magnetic write field returning to the return poles216,224does not erase the previously recorded bit.

As higher data density requirements require ever smaller recorded bits of data, the magnetic bits become inherently unstable. In order to make the bits more stable, the magnetic media can be constructed to have a higher magnetic anisotropy. However, this increase in magnetic anisotropy also makes the media harder to write to, requiring larger magnetic write field strength. The necessarily smaller size of the write pole214exacerbates this problem by making it even harder to generate a sufficiently strong magnetic write field.

One way to overcome this dilemma is through the use of microwave assisted magnetic recording (MAMR) A magnetic layer in the magnetic oscillator230oscillates its magnetization by the feeding of current there-through and generates a high frequency magnetic field. This high frequency magnetic field temporarily lowers the magnetic anisotropy of the magnetic media making it easier to write to with less magnetic write field. An electrical current can be supplied to the magnetic oscillator in order to cause the magnetic oscillator230to generate its magnetization's oscillation and the high frequency magnetic field. This electrical current can be supplied by circuitry234that can be electrically connected with, for example, the magnetic return pole224and back gap layer218. An electrically insulating layer235can be provided at the back portion of the write head204to prevent the electrical current from being shunted through the back of the write head204. Therefore, the electrical current flows through the write pole214and through the magnetic oscillator230to the trailing magnetic shield222.

One challenge that arises as a result of the use of the magnetic oscillator230is that the electrical current flowing through the magnetic oscillator230, as well as the write pole214, and trailing magnetic shield222heats up these structures. Heating of the write pole214results in performance degradation, such as that due to oxidation of the write pole214. In addition, this heating can result in removal of the carbon overcoat (not shown) that is used to protect the slider during operation. This removal of the carbon overcoat greatly reduces the lifespan of the magnetic data recording system.

One way to prevent such heating is by providing a heat sink structure. A heat sink structure is a structure that is constructed of a thermally conductive material that can conduct heat away from the write pole214, spin torque oscillator230and trailing magnetic shield222. While it might seem desirable to place such a heat sink structure at the sides of the write pole214, other necessary structure around the write pole make the use of such a heat sink structure problematic and inefficient. For example, a non-magnetic side shield material is desired to prevent adjacent track interference, and an electrically insulating, non-magnetic side wall is needed to separate the write pole214from the side shield, in order to allow the write pole214to function properly and also to allow the current to flow from the write pole214to through the spin torque oscillator230without being shunted through the magnetic side shields.

This can be understood more clearly with reference toFIG. 3, which shows an enlarged view of the write pole214and surrounding structure as viewed from the media facing surface. As seen inFIG. 3the write pole214can have a triangular (or trapezoidal) shape as viewed from the air bearing surface. A magnetic side shield structure302is formed at the sides of and below the write pole214. The side shield structure302is separated from the sides of the write pole214by a non-magnetic side gap structure304, In addition, an optional insulation layer312may be provided between the side shield structure302and the heat sink structure306. The side gap structure304must be made of a material that is both non-magnetic and electrically insulating, such as alumina (Al2O3). Unfortunately, the magnetic material of the side shield structure302is not an ideal heat sink material, since such magnetic materials do not have as high a thermal conductivity as other more suitable materials such as Au. In addition, the side gap structure304(such as alumina) is an even worse conductor, so that it traps heat within the write pole214.

However, the structure shown inFIGS. 3 and 4overcomes this problem by providing a novel heat sink structure that removes heat from the trailing magnetic shield222,FIG. 3is a view as seen from the media facing surface, andFIG. 4is a top down view of the trailing shield222and surrounding heat sink structure306as seen from line4-4ofFIG. 3. As seen inFIG. 3, the trailing shield222is narrow and tall, having a width W measure between first and second laterally opposed sides310that is substantially aligned with the width of the trailing edge308of the write pole214and substantially aligned with the spin torque oscillator230. However, the trailing shield222need not be precisely aligned with the trailing edge308of the write pole214and spin torque oscillator230. The heat sink structure306extends laterally from each side310of the trailing magnetic shield222, and preferably physically contacts the sides of the trailing magnetic shield222. InFIG. 4it can be seen that the trailing magnetic shield222has a back edge402that is opposite the media facing surface MFS. The trailing magnetic shield has a depth D that is defined by the distance between the media facing surface MFS and the back edge402. Preferably, the depth D is significantly larger than the width W.

As can be seen inFIG. 4, the heat sink structure306wraps around the magnetic trailing shield structure222so that it contacts the sides310as well as the back edge402of the magnetic trailing shield structure222. The heat sink structure306is constructed of a material having a high thermal conductivity. The heat sink structure306preferably has a thermal conductivity of at least 4.0 E+08 pWum° C., and is preferably constructed of Au, which has excellent thermal conductivity on the order of 6.00 E+08 pW/um° C. Other suitable materials include Ru, an alloy of Au and another material. Cu or an alloy of Cu and another material, or Nitrides such as AlN.

FIG. 12is a table that shows the thermal properties of Au and various other materials that can be used in a write head. InFIG. 12, the column labeled STO shows the thermal properties of a spin torque oscillator. The column labeled TS/SS shows the thermal properties of a trailing shield and side shield structure constructed of a Ni45Fe54alloy. The column labeled MP shows the thermal properties of a main magnetic write pole constructed of Ni80Fe20alloy. The column labeled Cu(HS) shows the thermal properties of a heat sink structure constructed of Cu, and the column labeled Au(HS) shows the thermal properties of a heat sink structure constructed of Au. The column labeled AlOx shows the thermal properties of aluminum oxide which could be used to form an insulation layer such as the side gap layer304ofFIG. 3. The column labeled Altic (N58) shows the thermal properties of an aluminum titanium carbide material (AlTiC) that can be used as a slider body material. As can be seen, Au has a much higher thermal conductivity than any of the other materials making up the write head and has a significantly high thermal conductivity than even Cu. In addition, Au has a much lower specific heat density than any of the other materials. For this reason, the heat sink structure306(FIGS. 3 and 4) is preferably constructed of Au.

As discussed above with reference toFIGS. 3 and 4, the trailing magnetic shield222has sides310that are substantially aligned with the trailing edge308of the write pole214and also substantially aligned with the spin torque oscillator230. This arrangement provides optimal heat transfer properties for removing heat from the write pole214, spin torque oscillator230and trailing magnetic shield222. However, the trailing shield does not necessarily have to have a width that aligns with the write pole214and spin torque oscillator230. The trailing magnetic shield222could have a width that is substantially larger than the write pole214and spin torque oscillator. This would result in less than optimal thermal properties, but might be desirable for magnetic shielding performance purposes as a matter of design choice.

FIGS. 5a-11bshow a magnetic write head in various intermediate stages of manufacture in order to illustrate a possible method for manufacturing a heat sink structure such as that described above.FIGS. 5a, 6a, 7a, 8a, 9a, 10a, and 11aare cross sectional side views.FIGS. 5b, 6b, 7b, 8b, 9b, 10b, and 11bare cross sectional views of a media facing surfing surface plane as indicated by the dashed line denoted MFS inFIG. 5a. As those skilled in the art will appreciate, the media facing surface plane is a location at which the media facing surface will be located once slicing and lapping operations have been performed for the finished magnetic head structure.

With reference toFIGS. 5aand 5b, a magnetic write pole502is formed. The write pole502can be constructed by a damascene process such that it is formed in a trench in a magnetic shield material504with a layer of non-magnetic, electrically insulating material506between the write pole502and the shield material504. The write pole502can be formed with tapered leading and trailing edges as shown or without such tapers. A spin torque oscillator508can be formed over a portion of the write pole502, and an insulating fill layer510can be formed over the write pole502and shield material504in areas surrounding the spin torque oscillator508.

With reference now toFIGS. 6aand 6b, an electroplating frame mask602is formed over write pole502and insulation layer510. The electroplating frame mask can be formed of a photolithographically patterned photoresist and is formed with an opening that is configured to define a trailing magnetic shield. As shown inFIGS. 6aand 6b, the opening in the mask602can be configured to substantially align with the spin torque oscillator, although exact alignment is not absolutely necessary, and some variation or deviation can be tolerated.

With reference now toFIGS. 7aand 7b, a magnetic material702is electroplated over the mask602and into the opening in the mask602. The magnetic material702can be a Ni—Fe alloy, such as Ni45Fe54so as to provide good magnetic properties for use as a magnetic shield. After electroplating, the mask602can be lifted off, leaving a structure as shown inFIGS. 8aand 8b. The mask liftoff process can be one or more of ion milling, chemical lift-off or CO2“snow”. The lift-off of the mask leaves a columnar magnetic shield structure over the spin torque oscillator508. Then, with reference toFIGS. 9aand 9b, a heat sink material (preferably Au)902is deposited. Then, with reference toFIGS. 10aand 10b, a chemical mechanical polish (CMP) stop layer1002is deposited over the heat sink material902. The CMP stop layer1002is preferably Ru.

Then, a chemical mechanical polishing is performed, leaving a structure as shown inFIGS. 11aand 11b. The chemical mechanical polishing removes the raised portion of the heat sink material902and CMP stop layer1002over the shield, and exposes the top of the shield702, but may leave some of the CMP stop material1002in the field region away from the shield702, as shown inFIG. 11. The above processes, then, result in a magnetic shield702that is surrounded at its sides and back by an efficient heat sink material such as Au.