Browse Prior Art Database

Three stripe calibration system

IP.com Disclosure Number: IPCOM000015184D
Original Publication Date: 2001-Sep-13
Included in the Prior Art Database: 2003-Jun-20
Document File: 2 page(s) / 373K

Publishing Venue

IBM

Abstract

Disclosed is a wafer having elements with 3 different stripe heights repeating across rows as in figure 2. Stripe heights would be in the order of 3 um, then, 1.5 um, then, 1 um, repeating successively until each row is populated. At final wafer measurement, resistance is recorded for each row. For the purpose of this disclosure, on a row by row basis these sets of resistance values will be used to resolve calibration equations. Figure 1 3.0 um 1/SH .33 um

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Three stripe calibration system

     Disclosed is a wafer having elements with 3 different stripe heights repeating across rows as in figure 2. Stripe heights would be in the order of 3 um, then, 1.5 um, then, 1 um, repeating successively until each row is populated. At final wafer measurement, resistance is recorded for each row. For the purpose of this disclosure, on a row by row basis these sets of resistance values will be used to resolve calibration equations.

Figure 1

3.0 um

1/SH = .33 um

1.5 um

1/SH = .66 um

1.0 um

1/SH = 1.0 um

     To meet aerial density requirements for giant magneto-resistive (GMR) heads, thickness of leads have been reduced to permit thinner total read gaps. This has resutled in current crowding at upper GMR lead junction area. Partial milling process involving deposition of leads before milling MR stripes, also contributes to current crowding. Such current crowding produces an increase in resistance as a function of stripe height. Combined with GMR resistance change as a function of stripe height, lead resistance (RL) and slope constant (K) can no longer be resolved by linear equations. Hence, this disclosure describes a set of product GMR devices which enables non-linearity to be resolved by a second degree polynomial equation capable of calibrating to predict stripe height.

     Resistance average of 3.0 um devices, 1.5 um devices and 1.0 um devices are used for calibration equations. The graph below shows an example of the three average resistan...