In a disk drive, a magnetic recording head is made of read and write elements. The write element is used to record and erase data bits arranged in circular tracks on the disk while the read element plays back a recorded magnetic signal. The magnetic recording head is mounted on a slider which is connected to a suspension arm, the suspension arm urging the slider toward a magnetic storage disk. When the disk is rotated the slider flies above the surface of the disk on a cushion of air which is generated by the rotating disk.
The read element is generally made of a small stripe of multilayer magnetic thin films which have either magnetoresistance (MR) effect or giant magnetoresistance (GMR) effect, namely which changes resistance in response to a magnetic field change such as magnetic flux incursions (bits) from magnetic storage disk. Recorded data can be read from a magnetic medium because the external magnetic field from the recorded medium (the signal field) causes a change in the direction of magnetization in the read element, which in turn causes a change in resistance in the read element and a corresponding change in the sensed current or voltage.
FIGS. 1 and 2 illustrate examples of a conventional composite type thin-film magnetic head 10. FIG. 1 is a cross-sectional view of the head 10 perpendicular to the plane of the air bearing surface (ABS). FIG. 2 shows the slider 11 flying above the disk 13.
In these figures, the reference numeral 12 denotes a substrate, 15 denotes an undercoating, 20 denotes a lower shield layer of the MR reproducing head part (also known as a read head), 21 denotes an upper shield layer of the MR head part, which can also act as a lower pole of an inductive recording head part (also known as write head), 22 denotes a MR layer provided through an insulating layer 23 between the lower shield layer 20 and the upper shield layer 21, 26 denotes a write gap layer, 27 denotes a lower insulating layer deposited on the upper shield layer 21, 28 denotes a coil conductor formed on the lower insulating layer 27, 29 denotes an upper insulating layer deposited so as to cover the coil conductor 28, 30 denotes an upper pole, and 34 denotes a pad that would connect the read or write coil to other components in the drive. In general, there would be a plurality of pads 34 on the slider 11. Note that the pad 34 connects directly to the coil conductor 28. The upper pole 30 is magnetically connected with the lower pole (upper shield layer) 21 at its rear portion so as to constitute a magnetic yoke together with the lower pole 21.
As recording density and data transfer rate have increased over the past a few years, critical dimensions in the recording device such as track width read and write gap and coil size have decreased accordingly. Also, the fly height between the air bearing surface (ABS) 32 and the media have become smaller and smaller. For reference, recording heads with 40 GB/in2 products typically have fly heights of about 12 nanometers. This fly height will continue to decrease in the future. This reduction in head critical dimensions and fly height, while beneficial to magnetic performance, also comes with cost of mechanical reliability.
As shown in FIG. 3, on a typical slider 11, a layer of diamond-like carbon (DLC) 40 is added to the ABS 32 as a protective layer for tribological and environmental protection reasons, e.g., to protect the device from damage from mechanical contact with the disk 13 as well as corrosion. The layer of DLC 40 is adhered to the device by a layer of a silicon-containing adhesive 42. When such a protective coating is deposited onto the slider ABS 32, an interface between the adhesive film 42 and substrate 11 forms and usually results in formation of an alloy intermetallic compound from parent element/alloy constituents. Particularly, interfacial metal-silicide intermetallics are formed between the head magnetic device 11 and the carbon overcoat (COC) film 40. Such interfacial metal-silicide intermetallics are usually paramagnetic and constitute a paramagnetic deadlayer 44 increasing the effective or true magnetic spacing during use. Because the heads are designed to function at a nominal magnetic spacing, the silicide layer alters the properties of the device from the optimum design. Therefore, it is of great importance to reduce this intermetallic layer thickness by sharpening the interface between the adhesive layer 42 and device 11.
What is therefore needed is a method for creating a COC in which the magnetic deadlayer is minimized. In this way, the effective magnetic spacing can be reduced for the same physical magnetic distance. A reduction of magnetic spacing would directly contribute to improvement in head read and overwrite performance in a drive.
USPTO Backgrounds
USPTO Backgrounds