Etching a substrate: processes – Masking of a substrate using material resistant to an etchant – Mask is multilayer resist
Reexamination Certificate
1999-06-14
2001-09-11
Gulakowski, Randy (Department: 1746)
Etching a substrate: processes
Masking of a substrate using material resistant to an etchant
Mask is multilayer resist
C216S076000, C438S717000, C360S313000
Reexamination Certificate
active
06287476
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 and metal overspray on top of the passivation layer to reduce temperature.
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.) and U.S. Pat. No. 4,782,414 (Krounbi) that show an thick insulating layer
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over a 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. 5,256,249 (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. 5,668,335 (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 MR heads.
However, an improved method to remove heat
40
from a MR sensor and accurately defining the MR stripe width is still needed.
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 by an anodizing process before 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 sensor current from shunting through the overspray portion of the lead and a heat conductor to allow MR heat to dissipate through the overspray and lead.
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. An important feature of the invention is that the passivation layer is formed by an electrochemical (e.g., anodizing) process prior to the development of the lift off structure. The passivation layer is an electrical insulator (prevents the Sensor current from shunting through the overspray and a heat conductor to allow MR heat to dissipate through the overspray.
A method to form a passivation layer using an electrochemical process over a MR Sensor so that the passivation layer defines the MR track width. The passivation layer is preferably formed by anodizing the MR sensor. The passivation layer is an electrical insulator (preventing Sensor current (I) from shunting through the overspray) and a heat conductor to allow MR heat to dissipate away from the M sensor through the overspray.
The method comprises: forming a passivation layer on the MR sensor; the passivation layer formed using an electrochemical process. Then we spinning-on and printing a lift-off photoresist structure over the passivation layer. The passivation layer is etched to remove the passivation layer not covered by the lift-off structure thereby defining a track width of the MR sensor. Then we deposit a lead layer over the passivation layer and M sensor. The lift-off structure is removed where by the passivation layer defines a track width. The passivation layer is an electrical insulator that prevents sensor current (I) form shunting through overspray layers while allowing heat to dissipate through to the lead layer.
The present invention achieves these benefits in the context of known process technology. However, a further understanding of the nature and advantages of the present invention may be realized by reference to the latter portions of the specification and attached drawings.
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), Fontanna et al.
patent: 5595637 (1997-01-01), Tench et al.
patent: 5634260 (1997-06-01), Nix et al.
patent: 5658469 (1997-08-01), Jennison
patent: 5747198 (1998-05-01), Kamijima
patent: 5753131 (1998-05-01), Choukh et al.
patent: 5843521 (1998-12-01), Ju et al.
patent: 6007731 (1999-12-01), Han et al.
patent: 6103073 (2000-07-01), Thayamballi
patent: 6181532 (2001-01-01), Dovek et al.
Chang Jei-Wei
Chen Mao-Min
Han Cherng-Chyi
Ju Kochan
Kao Shou-Chen
Ackerman Stephen B.
Gulakowski Randy
Headway Technologies Inc.
Saile George O.
Smetana Jiri
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