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In-Situ Sheet Resistance Sensor for Thin Film Head Lapping

IP.com Disclosure Number: IPCOM000035240D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 66K

Publishing Venue

IBM

Related People

Arnold, JC: AUTHOR [+4]

Abstract

The final height dimension of the active sensor stripe in MR heads controls several important performance parameters. In current practice, the height is controlled by lapping the head surface until a predetermined target resistance is reached on an Electrical Lapping Guide (ELG). Because of the complex shape of the MR elements, the target resistance is found by combining the pattern dimensions with a film sheet resistance measurement made at the wafer level immediately after deposition.

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In-Situ Sheet Resistance Sensor for Thin Film Head Lapping

The final height dimension of the active sensor stripe in MR heads controls several important performance parameters. In current practice, the height is controlled by lapping the head surface until a predetermined target resistance is reached on an Electrical Lapping Guide (ELG). Because of the complex shape of the MR elements, the target resistance is found by combining the pattern dimensions with a film sheet resistance measurement made at the wafer level immediately after deposition.

This approach has several shortcomings. First, the sheet resistance is only known to the wafer level, and no correction for small film thickness variations across the wafer can be made. Second, the sheet resistance value must be measured at a very early step in the process, and must be retained until it is needed for lapping. Third, the head is heated by friction during lapping, and the non-zero temperature coefficient of film resistivity introduces an unpredictable offset between the lapping resistance calculated from the original (cold) sheet resistance and the actual resistance measured on the lapping machine.

This structure eliminates these problems by providing a means of measuring and monitoring the sheet resistance during the lapping process. A large sensor band of the MR material is fabricated near the ELG. The sensor is placed such that it is in thermal contact with the ELG but is not damaged by the lapping. The d...