Semiconductor device manufacturing: process – Semiconductor substrate dicing
Reexamination Certificate
2002-03-07
2004-06-29
Nguyen, Thanh (Department: 2813)
Semiconductor device manufacturing: process
Semiconductor substrate dicing
C438S033000, C438S068000, C438S462000, C438S463000
Reexamination Certificate
active
06756287
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for fabricating a slider including a notch. In particular, it relates to a method of slicing a slider wafer without chipping a base coat of the wafer.
Air bearing sliders have been extensively used in disc drives to position a transducing head above a rotating disc. The transducing head is typically carried by the slider. Conventionally, head positioning is accomplished by operating an actuator arm with a large-scale actuation motor, such as a voice coil motor (VCM), to radially position the slider over a track on a disc. Typically, disc drive systems include a suspension assembly attached to the actuator arm for supporting and positioning the slider. The suspension assembly includes a load beam attached to the actuator arm and a gimbal disposed at the opposite end of the load beam. The air bearing slider carrying the transducing head is mounted to a flex circuit material disposed upon the gimbal. This type of suspension assembly is used with both magnetic and nonmagnetic discs. The VCM rotates the actuator arm and the suspension assembly to position the transducing head over a desired radial track of the disc.
In order for the disc drive to read and write data from the transducing head, conductive traces are disposed along the flex circuit material of the suspension assembly for the disc drive to electrically communicate with the slider. The traces extend along the gimbal and end at flex on suspension (FOS) bond pads formed adjacent to the slider. The slider has a trailing edge with bond pads disposed on the trailing edge such that an electrical connection can be made between the traces and the slider. Typically, gold ball bonds are used to provide the connection between the FOS bond pads and the slider bond pads. Difficulties have arisen in prior art systems for attaching the slider to the gimbal, and in particular with respect to aligning the slider bond pads to the FOS bond pads.
Generally, the slider is placed on the gimbal with respect to a load point on the load beam. The load beam has a dimple located at its distal end which serves as the load point. The gimbal is attached to the load beam such that it balances about the dimple. Although placing the slider with respect to the dimple minimizes the degradation of the slider's fly height above the disc, the slider bond pads are often either too far away or too far forward of the FOS bond pads. Misalignment of the slider bond pads with the FOS bond pads results in an increased tolerance stack up of the slider with respect to the FOS bond pads.
One solution for improving alignment between the slider bond pads and the FOS bond pads is to include wafer process assembly features on the slider. These features include a notch on the slider and a bond pad extension for the slider bond pad. The notch is typically formed on the slider body during slider processing.
In prior art systems, the slider body is formed during slider processing from a substrate, known as a wafer. The wafer is multi-layered and comprised of a substrate topped by a base coat and an overcoat. Initially, a notch is formed in the slider by removing a portion of the overcoat from slice lanes extending across the wafer in a first direction. The wafer is then sliced with a mechanical wheel along the slice lanes, or rows, into a plurality of slider bars. Furthermore, the mechanical wheel may be used to remove the overcoat to form the notch. Each slider bar includes a plurality of individual slider bodies. The slider bars are cut along a plurality of dice lanes to form individual slider bodies. The dice lanes extend across the wafer in a direction substantially perpendicular to the slice lanes.
The mechanical wheel used to slice the wafer and/or remove the overcoat causes fracturing and chipping of the base coat. The fractures and chips of the base coat extend into the slider body and underneath the overcoat causing damage to the slider body. Over time the base coat degrades and eventually disappears from the slider body. Degradation of the base coat has damaging effects on the electric and overall performance of the slider. Furthermore, the mechanical slice of the wafer creates a poorly-defined slice edge of the slider which leads to further chipping of the base coat. Chipping of the base coat and partial chipping by a poorly-defined slice edge creates hard particles and contamination in the disc drive which leads to the disc drive crashing.
A method for fabricating a slider is needed in the art that eliminates fracturing and chipping of the base coat during slicing of the wafer and creates a well defined and clear edge on the slider.
BRIEF SUMMARY OF THE INVENTION
The present invention is a method for forming sliders for use in a disc drive actuation system. The method comprises providing a wafer formed of a substrate having a base coat and an overcoat. Wafer-level notch lanes having a first width extend across the wafer in a first direction. The overcoat is removed from the wafer-level notch lanes. The wafer is sliced along a portion of the waferlevel notch lanes through the base coat to form a channel. The wafer is mechanically sliced through the substrate along slice lanes that extend across the wafer in the first direction to differentiate the wafer into bars. The bars are cut in a second direction substantially perpendicular to the first direction to form the sliders.
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Gallup Paul E.
Jones Gordon M.
Khlif Mohamed Salah H.
Ramdular Jumna P.
Ramdular Ruperta T.
Kinney & Lange , P.A.
Nguyen Thanh
Ramdular Ruperta T.
Seagate Technology LLC
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