Browse Prior Art Database

Precision Electrical Grind Gauge for Magnetic Read/Write Heads

IP.com Disclosure Number: IPCOM000039155D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 38K

Publishing Venue

IBM

Related People

Stephens, GB: AUTHOR

Abstract

Numerous prior articles and patents illustrate the basic concept of measuring the resistance of an element laid down on a substrate with a thin film magnetic or other magnetic sensor for the purpose of measuring changes in resistance as a grinding operation, to achieve the desired final dimensions, is carried out. U. S. Patent 3,821,815 describes such methods and systems. Similar material showing other variations of the techniques employed are shown in [1-7]. The present article describes another technique in which a plurality of stepwise resistance changes will be generated as the grinding operation proceeds.

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Precision Electrical Grind Gauge for Magnetic Read/Write Heads

Numerous prior articles and patents illustrate the basic concept of measuring the resistance of an element laid down on a substrate with a thin film magnetic or other magnetic sensor for the purpose of measuring changes in resistance as a grinding operation, to achieve the desired final dimensions, is carried out. U. S.

Patent 3,821,815 describes such methods and systems. Similar material showing other variations of the techniques employed are shown in [1-7]. The present article describes another technique in which a plurality of stepwise resistance changes will be generated as the grinding operation proceeds. These avoid the sudden discontinuous step to an infinite resistance by opening a grind bar as in some of the prior art and also provide a convenient means of graduated measurement which could be indicated by pulses or stepwise increases in resistivity that can be counted rather than measured in the analog fashion. The figure is illustrative. A silicon substrate 1 has been provided in photolithographic and diffusion ion implantation steps and the like with an emitter 2 forming the sensitive area for a magnetically sensitive transistor. Collectors 3 and a base contact 4 complete the structure. It is necessary to abrade the surface in the direction of the arrow 5, perhaps to a level h1 in which the emitter 2 and the collectors 3 are not touched.

Since this may be on the order of 200 nanometers or less, very precise control of the grinding process is necessary. Beginning with an initial thickness hn, aluminum shorting bars 6 that connect discrete segments along a continuous diffused resistor 7 are gradually ground away in the grinding process. This gradually unshorts more and more of the resistor 7 and increases the resistance that can be measured between leads 8 in a stepwise, discretely controlled manner. The grinding machinery can b...