Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Coating selected area
Reexamination Certificate
1999-06-14
2001-08-14
Gorgos, Kathryn (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Coating selected area
C205S122000
Reexamination Certificate
active
06274025
ABSTRACT:
BACKGROUND OF INVENTION
1) Field of the Invention
This invention relates generally to fabrication of bit lines and more particularly to the fabrication of a Magnetoresistive head (MR) for a Magnetic disk drive and more particularly to a method for forming a passivation layer over a MR sensor layer.
2) Description of the Prior Art
The prior art discloses a magnetic transducer referred to as a magnetoresistive (MR) sensor or head which has been shown to be capable of reading data from a magnetic surface at great linear densities. A MR sensor detects magnetic field signals through the resistance changes of a read element made from a magnetoresistive material as a function of the amount and direction of magnetic flux being sensed by the element.
Current MR heads are manufactured by using a lift-off process to deposit lead layers and define reader track. See e.g., U.S. Pat. No. 5,658,469(Jennison) that shows a lift-off method for improving the photoresist lift-off block shape.
Numerous prior art MR sensors have been developed, and these prior art MR sensors have been effective to meet prior art requirements. However, the drive toward increased recording density has led to the requirement for narrower recording tracks and increased linear recording density along the track. The small MR sensors which are necessary to meet these requirements cannot be made with the use of the prior art techniques.
The importance of overcoming the various deficiencies noted above is evidenced by the extensive technological development directed to the subject, as documented by the relevant patent and technical literature. The closest and apparently more relevant technical developments in the patent literature can be gleaned by considering RE34,099(Krounbi et al.) that shows an thick insulating layer over a MR sensor.
U.S. Pat. No. 5,256,249(Hsie et al.) discloses a method for forming a MR sensor having a track wide oxide layer overlying the MR sensor.
U.S. Pat. No. 5,658,469(Jennison) shows a method for improving the photoresist lift-off block shape to form a consistent undercut.
U.S. Pat. No. 5,568,335(Fontana et al.), U.S. Pat. No. 5,491,600(Chen et al.) and U.S. Pat. No. 5,747,198(Kamijima) show a photoresist lift-off processes to form a MR heads.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method to form a passivation layer over a MR Sensor so that the passivation layer defines the track width.
It is an object of the present invention to provide a method to form a passivation layer over a MR Sensor so that the passivation layer is formed simultaneously with the development of the lift off structure.
It is an object of the present invention to provide a method to form a passivation layer over a MR Sensor so that the passivation layer is an electrical insulator (prevents MR sensor current from shunting through the overspray and a heat conductor to allow MR heat to dissipate through the overspray.
To accomplish the above objectives, the present invention provides a method to form a passivation layer over a MR Sensor so that the passivation layer defines the track width. A key step of the invention is that the passivation layer is formed simultaneously with the development of the lift off structure in a novel developer/oxidizer solution. The passivation layer is an electrical insulator that prevents Sensor current (I) from shunting through the overspray lead portion and a heat conductor to allow MR heat to dissipate through the overspray.
Key features of the invention are: 1) passivation layer is formed by a chemical process during the development of the photoresist lift-off structure by oxidizing the MR sensor. 2) passivation layer is thin to allow heat to dissipate from the MR sensor but prevents MR current.
Additional objects and advantages of the invention will be set forth in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of instrumentalities and combinations particularly pointed out in the append claims.
REFERENCES:
patent: Re. 34099 (1992-10-01), Krounbi et al.
patent: 4782414 (1988-11-01), Krounbi et al.
patent: 5256249 (1993-10-01), Hsie et al.
patent: 5491600 (1996-02-01), Chen et al.
patent: 5568335 (1996-10-01), Fontana et al.
patent: 5658469 (1997-08-01), Jennison
patent: 5747198 (1998-05-01), Kamijima
patent: 5763108 (1998-06-01), Chang et al.
patent: 5901432 (1999-05-01), Armstrong et al.
patent: 6103073 (2000-08-01), Thayamballi
Chang Jei-Wei
Chen Mao-Min
Han Cherng-Chyi
Ju Kochan
Kao Shou-Chen
Ackerman Stephen B.
Gorgos Kathryn
Headway Technologies Inc.
Saile George O.
Smith-Hicks Erica
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