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GMR system called "abc Calibration" for predicting stripe height and controlling KissLap Operations

IP.com Disclosure Number: IPCOM000014917D
Original Publication Date: 2001-Sep-13
Included in the Prior Art Database: 2003-Jun-20
Document File: 2 page(s) / 194K

Publishing Venue

IBM

Abstract

Disclosed is a Calibration System for GMR sub-micron track width devices that resolves the non-linear character of the Inverse of Stripe Height versus Resistance relationship: 1/SH f(R), hence allows precise Stripe Height prediction and disposition before and after final Kisslap operation. To meet giant magneto-resistive (GMR) head aerial density requirements, thickness of leads have been reduced to permit thinner total read gaps. This has resulted in current crowding at upper GMR lead junction area. Partial milling process, involving deposition of leads before milling MR stripes, further contributes to current crowding. As a result, GMR resistance change as a function of stripe height, lead resistance (RL), and slope constant (K) which is the product of track width and MR sheet resistance, can no longer be resolved by linear equations. Disclosed is a calibration system comprised of wafer MR devices having two different stripe heights with corresponding resistance measurements together with an intermediate resistance test at the end of a pre-Kisslap stripe height lap operation. The initial height of the two MR stripes are 5.0 and 3.0 microns. These two stripe heights repeat in an alternating pattern from one side of the row to the other, where, at the end of wafer process, resistance measurements are made and passed on for later calibration. A third set of resistance values are supplied at the end of the first lapping process referred to as (BCL).

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  GMR system called "abc Calibration" for predicting stripe height and controlling KissLap Operations

   Disclosed is a Calibration System for GMR sub-micron track width devices that resolves the non-linear character of the Inverse of Stripe Height versus Resistance relationship: 1/SH = f(R), hence allows precise Stripe Height prediction and disposition before and after final Kisslap operation.

To meet giant magneto-resistive (GMR) head aerial density requirements, thickness of leads have been reduced to permit thinner total read gaps. This has resulted in current crowding at upper GMR lead junction area. Partial milling process, involving deposition of leads before milling MR stripes, further contributes to current crowding. As a result, GMR resistance change as a function of stripe height, lead resistance (RL), and slope constant
(K) which is the product of track width and MR sheet resistance, can no longer be resolved by linear equations.

   Disclosed is a calibration system comprised of wafer MR devices having two different stripe heights with corresponding resistance measurements together with an intermediate resistance test at the end of a pre-Kisslap stripe height lap operation. The initial height of the two MR stripes are 5.0 and 3.0 microns. These two stripe heights repeat in an alternating pattern from one side of the row to the other, where, at the end of wafer process, resistance measurements are made and passed on for later calibration. A third set of resistance values are supplied at the end of the first lapping process referred to as (BCL).

   The chart below shows resistance versus the reciprocal of stripe height where, resistance at 5.0 um, 3.0 um and end of BCL is displayed. MR devices prior to GMR would typically plot as the linear function of Slope K as shown. Calibration could easily be achieved by linear equations resolved by two stripe heights. However, change in lead resistance as a function of stripe height forces the total resistance (GMR plus leads) into the non-linear function also shown.

   Th...