Dynamic magnetic information storage or retrieval – Fluid bearing head support – Disk record
Reexamination Certificate
1999-05-11
2001-06-26
Ometz, David L. (Department: 2652)
Dynamic magnetic information storage or retrieval
Fluid bearing head support
Disk record
C029S603070
Reexamination Certificate
active
06252741
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF INVENTION
1. Field of Invention
The present invention is directed to a method for enhancing the electrical resistivity of at least a region of a ceramic substrate. The present invention also is directed to a ceramic substrate having a region of enhanced electrical resistivity that is provided by the method of the invention. In addition, the present invention relates to thin film magnetic recording heads having inductive or magnetoresistive sensors and wherein the heads' electronic layers are disposed on a region of substrate of a ceramic material, the region having enhanced electrical resistivity relative to the remainder of the substrate and composed predominantly of the ceramic material. The region of enhanced electrical resistivity may be provided by the method of the present invention.
The method of the invention finds application in any field in which it is desirable to enhance the electrical resistivity of at least a region of a ceramic substrate. An example of a specific application of the present method is in the production of inductive and magnetoresistive (AMR, giant magnetoresistive, or spin valve) thin film magnetic recording heads.
2. Background of Invention
Ceramic materials are commonly used as a substrate in the production of inductive and magnetoresistive thin film magnetic recording heads. One subset of these ceramic materials is composed primarily of alumina (Al
2
O
3
) and titanium carbide (TiC). A particular example of this type of ceramic material, commonly referred to as “AlTiC”, includes about 60-80% by weight alumina and about 20-40% by weight titanium carbide, along with the possible intentional addition of other components in minor amounts. AlTiC provides excellent machinablity when subjected to the several shaping processes (slicing, lapping, polishing, etc.) used to form the recording head and its air bearing surface (ABS).
In general, thin film magnetic recording heads are produced as follows. The AlTiC or other ceramic material employed as the substrate in head production is typically provided in a wafer or “puck” form. A series of thin film layers are formed on a surface of the raw wafer, typically using lithography processes comprising one or more steps of seed layer deposition, photoresist, permalloy electroplating, resist stripping, seed layer removal, sputter coating, and removal of metallic and insulating films. The thin film layers formed on the wafer include the magnetic pole elements of the recording head, and the several thin film layers formed on the wafer are referred to collectively herein as the “electronic layer” to contrast that layer with the ceramic substrate material. The ceramic substrate material merely acts to support the electronic layer and does not participate electronically in the read/write process. After the electronic layer is formed on the wafer, the wafer is separated into single rows of devices, called rowbars, by executing spaced parallel cuts through the thickness of the finished wafer. Each rowbar will include a portion of the ceramic wafer and the portion of the electronic layer that has been formed thereon.
The configuration of the magnetic read and write poles within the electronic layer is critical to the proper performance of the head. After each rowbar is sawed from the finished wafer, it is mounted on a transfer tool and the freshly sawed edge of the rowbar is carefully lapped back to adjust the dimensions of the electronic layer. The lapped surface of the electronic layer of the rowbar, with the magnetic pole tips just exposed, becomes the operative end of the head that will fly closest to the rotating magnetic media, on the trailing edge of the magnetic recording head. After the lapping procedure, a number of air bearing surfaces are formed along an exposed ceramic surface of the rowbar. Each rowbar is then sawed into discrete units, each discrete unit including a portion of the ceramic wafer and the portion of the electronic layer formed thereon. Each discrete unit includes magnetic read and write poles and an ABS and is referred to as a magnetic recording head or a “slider”. If a magnetic recording head is to be used in a disc drive, it is mounted to a suspension. The combination of the head and the suspension, known as a “head/gimbal assembly”, is then incorporated into the hard disc drive. The suspension determines the pitch, roll, normal force, and height of the magnetic recording head relative to the magnetic media. Magnetic recording heads also may be utilized in video or tape devices, in which case they are not mounted to a suspension.
When a magnetic recording head is mounted to a suspension, it is oriented so that the ABS will face the magnetic media when the head/gimbal assembly is assembled into the disc drive. The ABS is designed to allow the magnetic recording head to aerodynamically fly over the magnetic media in microinch proximity as the media rotates, allowing the magnetic poles of the electronic layer to magnetically interact with the magnetic media. The suspension positions the magnetic recording head over the magnetic media so that the electronic layer is at a trailing edge of the magnetic recording head relative to the surface of the rotating magnetic media. The distance between a magnetic pole at the trailing edge of the magnetic recording head and the surface of the rotating magnetic media is referred to as the “flying height”. In general, lessening the flying height increases the performance of the head.
The ceramic material from which the wafer is composed must have an electrical resistivity that is low enough to allow dissipation of static electricity accumulation during read/write performance. Wafers composed of ceramic materials having sufficiently low electrical resistivity, such as AlTiC wafers, are too conductive to allow the electronic layer to be built directly on the surface of the ceramic material. Therefore, in the production of magnetic recording heads using AlTiC as the wafer material, a thick (3-10 &mgr;m) electrically insulating layer of alumina (typically amorphous alumina) is formed intermediate the ceramic wafer and the electronic layer. The electrically insulating layer is commonly referred to as an “undercoat” layer or “basecoat”, and it must be deposited on a surface of the ceramic wafer before the electronic layer is formed. The process of undercoat formation is very costly. For example, the process of forming an alumina undercoat layer on an AlTiC wafer requires the use of a clean room and costly sputtering equipment, and the proper loading of the wafers into the sputtering apparatus is both time-consuming and critical to the process. During the sputtering process, the ceramic wafer is placed on a water cooled fixture. To effectively cool the wafer, indium-gallium liquid is manually applied between the wafer and water cooled fixture to establish intimate thermal contact. The indium-gallium liquid must be manually wiped off when the coating process is complete. The process of applying and removing the indium-gallium liquid is time-consuming, and any residue left on the wafer surface is a source of contamination for subsequent processes. After the undercoat layer has been deposited, the entire undercoat surface must be planarized, typically by lapping or chemical-mechanical polishing. The undercoat layer also must be adjusted to a specified thickness, surface roughness, and flatness before the undercoat layer's exposed surface receives the build up of the electronic layer thereon. The entire undercoat layer deposition process may take as long as 10 hours, depending on the thickness requirement.
FIG. 1
is a representation of a portion of a conventional magnetic recording head and shows the position of the head relative to the rotating magnetic media during read/write performance. The ABS
10
of the magnetic recording head
12
opposes the magnetic medium
14
. The magnetic recording head
12
inclu
Chen Tianjie
Greenleaf Technologies
Kirkpatrick & Lockhart LLP
Ometz David L.
LandOfFree
Thin film magnetic recording head with treated ceramic... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Thin film magnetic recording head with treated ceramic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thin film magnetic recording head with treated ceramic... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2442131