Browse Prior Art Database

ELG device built with 4 terminal calibration

IP.com Disclosure Number: IPCOM000015185D
Original Publication Date: 2001-Sep-01
Included in the Prior Art Database: 2003-Jun-20
Document File: 3 page(s) / 139K

Publishing Venue

IBM

Abstract

Disclosed is an MR ELG device, having a built in electrical test structure, which provides a means for obtaining initial ELG lead resistance (RL). Lapping magneto-resistive (MR) recording head rows is controlled by electrical lapping guides (ELGs). ELG calibration is of prime importance in achieving proper stripe height. Differential stripe height calculations based on ELGs having two different stripe heights are used for determining such calibration constants associated with lead resistance (RL) and the product of sheet resistance and ELG track width (K). In order to calculate the constant (K), the constant (RL) must be known. In order to calculate the constant (RL), the exact height of the long and short ELG stripe must be known. Here lies the problem with differential calibration. The accuracy of this scheme is limited first by the practical issue of not being able to make 100% measurements. Second, it is limited by precision and accuracy of equipment used for determining height of each ELG stripe before constant (K) and (RL) can be calculated. Hence, this disclosure has an MR ELG device with a built in electrical test structure that provides a means for obtaining initial ELG lead resistance (RL). Once lead resistance is determined, constant (K) can be determined on a device by device basis. Because this method can be automated for 100% of the ELGs using a highly precise 4 point probe direct measurements, it is a direct and much more accurate way of determining lead resistance. Below in figure 1 is a four terminal ELG having built in method for obtaining lead resistance. 3 7 8

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 51% of the total text.

Page 1 of 3

ELG device built with 4 terminal calibration

     Disclosed is an MR ELG device, having a built in electrical test structure, which provides a means for obtaining initial ELG lead resistance (RL). Lapping magneto-resistive (MR) recording head rows is controlled by electrical lapping guides (ELGs). ELG calibration is of prime importance in achieving proper stripe height. Differential stripe height calculations based on ELGs having two different stripe heights are used for determining such calibration constants associated with lead resistance (RL) and the product of sheet resistance and ELG track width (K). In order to calculate the constant (K), the constant (RL) must be known. In order to calculate the constant (RL), the exact height of the long and short ELG stripe must be known. Here lies the problem with differential calibration. The accuracy of this scheme is limited first by the practical issue of not being able to make 100% measurements. Second, it is limited by precision and accuracy of equipment used for determining height of each ELG stripe before constant (K) and (RL) can be calculated. Hence, this disclosure has an MR ELG device with a built in electrical test structure that provides a means for obtaining initial ELG lead resistance (RL). Once lead resistance is determined, constant (K) can be determined on a device by device basis. Because this method can be automated for 100% of the ELGs using a highly precise 4 point probe direct measurements, it is a direct and much more accurate way of determining lead resistance.

     Below in figure 1 is a four terminal ELG having built in method for obtaining lead resistance.

3

7 8

4

5

     In this structure, ELG leads 1 and 2 extend downward and terminate at pads 3 and 4. As is fairly standard in MR devices, lead thickness is increased at 5 and 6 in areas away from eventual air bearing region by a layer. Likewise, such layer is added to the lower set of extended leads away from eventual air bearing region and terminating at pads 3 and 4. All subsequent MR and write element layers are then deposited as in normal process. As in MR and ELG devices, vias and additional metal are provided for pads 3 and 4 making it possible to route studs up through overcoat with final gold pad deposition to complete the assembly.

1

6

1 2

[This page contains 4 pictures or other non-text objects]

Page 2 of 3

     Lead resistance can be obtained at intermediate operations or at final wafer testing. This is achieved first by obtaining ELG sensor resistance (RS). For this, measurement, current in the order of 0.25 ma is passed from pad termination 3 to pad termination 4. At the same time, voltage is measured at pad termination 7 and termination 8. By ohm's law, a resistance value is obtained by the relationship between current and voltage. This resistance value is an MR sensor without lead resistance because, when current is passed through the ELG sensor by lower leads, and voltage measured at upper pads 7 and 8, voltage d...