Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making named article
Reexamination Certificate
2000-09-28
2002-07-09
Rosasco, S. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making named article
Reexamination Certificate
active
06416936
ABSTRACT:
The subject matter of the present invention is related to that disclosed in U.S. Pat. No. 5,485,334 for “Magnetoresistive Device and Method Having Improved Barkhausen Noise Suppression”; U.S. Pat. No. 5,532,892 for “Soft Adjacent Layer Biased Magnetoresistive Device Incorporating a Natural Flux Closure Design Utilizing Coplanar Permanent Magnet Thin Film Stabilization”; U.S. Pat. No. 5,573,809 for “Process for Forming a Magnetoresistive Device”; U.S. Pat. No. 5,608,593 for “Shaped Spin Valve Type Magnetoresistive Transducer and Method for Fabricating the Same Incorporating Domain Stabilization Technique”; U.S. Pat. No. 5,634,260 for “Method of Making a Magnetoresistive Device Having Improved Barkhausen Noise Suppression”; U.S. Pat. No. 5,637,235 for “Shaped Spin Valve Type Magnetoresistive Transducer and Method for Fabricating the Same Incorporating Domain Stabilization Technique”; U.S. Pat. No. 5,639,509 for “Process for Forming a Flux Enhanced Magnetic Data Transducer”; U.S. Pat. No. 5,654,854 for “Longitudinally Biased Magnetoresistive Sensor Having a Concave Shaped Active Region to Reduce Barkhausen Noise by Achieving a Substantially Single Magnetic Domain State”; U.S. Pat. No. 5,658,469 for “Method for Forming Re-Entrant Photoresist Lift-Off Profile for Thin Film Device Processing and a Thin-Film Device Made Thereby”; and U.S. Pat. No. 5,668,688 for “Current Perpendicular-to-the-Plane Spin Valve Type Magnetoresistive Transducer”, the disclosures of which are herein specifically incorporated by this reference.
BACKGROUND OF THE INVENTION
The present invention relates, in general, to the field of magnetoresistive (“MR”) and giant magnetoresistive (“GMR”) read/write heads. More particularly, the present invention relates to a technique for top surface imaging for top pole tip width control in MR write head processing.
Top pole tip definition for the write transducer portion of a read/write head and its critical dimension (“CD”) control currently present major challenges in thin film MR/GMR head processing. As the demand for ever more storage capacity in disk drives intensifies resulting in the need for real recording densities of on the order of 20,000 to 35,000 tracks per inch (“TPI”) and greater, future generations of these heads must then exhibit a track width which is increasingly reduced while nevertheless maintaining a high stack height for performance reasons.
As a consequence, these constraints imply that the critical dimensions of the top pole tip of the write head must be in the sub-micron range of on the order of 0.30 to 0.8 microns (“&mgr;m”). However, utilizing current thin film photolithography techniques and steppers, it is extremely difficult to pattern tip widths of such narrow dimensions while also providing high aspect ratios and vertical profiles together with tight critical dimension control due to the limitation of resolution inherent in a conventional thick photoresist pattern of on the order of 6.0 &mgr;m-10.0 &mgr;m. While conventional processing can be used in conjunction with a slider level pole trim operation as one way to achieve a sub-micron write track width, such an operation is extremely costly in a manufacturing environment with the further possibility that it can easily result in damage to the associated MR and/or GMR read sensor.
SUMMARY OF THE INVENTION
In accordance with the technique of the present invention a top surface imaging technique for top pole tip width control is disclosed in which a multi-layer structure is employed to define the thick photoresist with much improved dimensional control. To this end, a relatively thin upper photoresist layer is patterned with much improved resolution, an intermediate layer of ceramic or metal is then defined utilizing the upper photoresist layer as a reactive ion etching (“RIE”) mask, with the intermediate layer then being used as an etching mask to define the bottom-most thick photoresist layer by a second RIE process. As a consequence, a much improved sub-micron pole tip width along with a high aspect ratio and vertical profile is provided together with much improved critical dimension control.
In operation, the technique of the present invention allows current stepper and process technology to be expanded beyond conventional resolution limits due to the fact that it effectively transfers the difficulties inherent in thick photoresist definition to another relatively thin photoresist pattern definition, utilizing a RIE process to define the resultant critical dimensions. Overall, the technique of the present invention provides a number of advantages including the provision of high aspect ratio and vertical properties in a sub-micron pole tip, increased optical resolution utilizing conventional stepper equipment and improved critical dimension control. Stated another way, the technique of the present invention, in utilizing a relatively thin patterned photoresist layer for the critical pattern definition followed by a reactive ion etching operation to accurately transfer the pattern from an upper surface through an intermediate and underlying thick photoresist layer, allows one to effectively pattern the thick photoresist layer by only exposing the upper thin photoresist layer. The use of the patterned thin photoresist layer in conjunction with the intermediate layer and underlying thick photoresist layer ultimately provides much improved trackwidth control while concomitantly extending the useful lifetime of current stepper technology. The technique of the present invention also provides greater head design flexibility since less stringent process requirements are needed to achieve a given desired stack height.
Particularly disclosed herein is a process for forming a pole tip in a data transducer write head, and an upper pole of a read/write head made thereby, which comprises: providing a substrate; applying a first photoresist layer overlying the substrate; applying an intermediate layer overlying the first photoresist layer; applying a second photoresist layer overlying the intermediate layer, the second photoresist layer being relatively thinner than the first photoresist layer; patterning the second photoresist layer to produce an opening therein; etching the intermediate layer utilizing the opening as a mask; further etching the first photoresist layer through the opening utilizing the intermediate layer as another mask; forming the pole tip within the opening etched in the first photoresist layer; and removing the first and second photoresist layers and the intermediate layer to expose the pole tip.
Further disclosed herein is a read/write head for a computer mass storage device wherein an upper pole thereof is made by the process of: providing a multilayer structure comprising a first relatively thick photoresist layer overlying a gap layer of the read/write head, an intermediate layer overlying the first relatively thick photoresist layer and a second relatively thin photoresist layer overlying the intermediate layer; patterning the second relatively thin photoresist layer to provide an opening therein to the intermediate layer; etching the intermediate layer and the first relatively thick photoresist layer within the opening to the gap layer; forming the upper pole within the opening etched in the first relatively thick photoresist layer; and removing the first relatively thick and second relatively thin photoresist layers and the intermediate layer.
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Jennison Michael J.
Pan Wei
Burton Carol W.
Hogan & Hartson LLP
Kubida William J.
Matsushita-Kotobuki Electronics Industries, Ltd.
Rosasco S.
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