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Magnetoresistive Head with Integrated Varistor for ESD/EOS Protection

IP.com Disclosure Number: IPCOM000014696D
Original Publication Date: 2000-Apr-01
Included in the Prior Art Database: 2003-Jun-20
Document File: 1 page(s) / 32K

Publishing Venue

IBM

Abstract

Described is a magnetic recording head having a magnetoresistive read sensor combined with a layer that provides varistor action in a structure that is essentially a metal oxide varistor (MOV) to protect the magnetoresistive read element from the deleterious effects of electrostatic discharge (ESD) and electrical overstress (EOS). The novel feature of the invention is the incorporation of a MOV in an integrated fashion into the head structure by disposing it in proximity to elements of the read sensor circuit susceptible to ESD/EOS damage with minimal impact on the overall mask layout and design. Through the use of existing lead or sensor metallurgy as one electrode in contact with the layer providing varistor action, and other structures serving as grounded counter-electrodes, it is possible to shunt to ground electrical transients that would otherwise damage a sensor which is becoming increasingly ESD/EOS sensitive due to the device scaling that attends the demands of ever increasing areal recording densities.

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Magnetoresistive Head with Integrated Varistor for ESD/EOS Protection

   Described is a magnetic recording head having a magnetoresistive read sensor
combined with a layer that provides varistor action in a structure that is
essentially a metal oxide varistor (MOV) to protect the magnetoresistive read
element from the deleterious effects of electrostatic discharge (ESD) and
electrical overstress (EOS). The novel feature of the invention is the
incorporation of a MOV in an integrated fashion into the head structure by
disposing it in proximity to elements of the read sensor circuit susceptible to
ESD/EOS damage with minimal impact on the overall mask layout and design. Through
the use of existing lead or sensor metallurgy as one electrode in contact with
the layer providing varistor action, and other structures serving as grounded
counter-electrodes, it is possible to shunt to ground electrical transients that
would otherwise damage a sensor which is becoming increasingly ESD/EOS sensitive
due to the device scaling that attends the demands of ever increasing areal
recording densities.

   A preferred embodiment of the invention comprises a nominally 45 x 45 micron
square ZnO layer, 20 microns thick, disposed under a contact stud structure of
the head, and above a grounded metallic counter-electrode. Calculations based on
the I-V, i. e. current-voltage, characteristic of ZnO varistors indicate that
this structure would provide protection from voltage transients exceeding

2nominally 300 mV, and sustained current densities from 0.5 mA/cm to 1.0x103 A/cm2
. This structure works in a passive, high-resistance mode under normal operation
of the head; but, when a voltage transient as described above occurs...