Increased Magneto Resistive Head Temperature Stability

Increased Magneto Resistive Head Temperature Stability

      This article describes a method to increase the temperature
stability of a Magneto Resistive (MR) head on wafer level.

      Normally, MR head products are tested before implementation
using temperatures of about 200-220 degrees C and more for
approximately 24 hours to simulate that the heads still operate even
under elevated temperatures.

      However, it was shown that many of the heads fail the test at a
temperature level of 220 degrees C showing ABS delamination.  This,
in turn, affects the head operation and leads to a non functional
file.

      It could be shown that delamination occurs due to the amount
of redeposition at the side of the permalloy 1 layer.  Redeposition
is originated during MR head manufacture by several sputter-etch
processes.  It is accumulated at the side wall because of the
negative wall angle present.  This negative wall angle avoids a
redeposition cleaning of the various seedlayers during sputter-etch.
Redeposition at the sidewall of P1, which is mostly affected, is the
cause for delamination because of its large amount.  During the
temperature cycle this redeposition oxidizes.  A channel to the
isolation stack is formed and this connection between the air bearing
surface, and the element stack leads to a physical change of the
stack and finally to delamination.

      This reliability problem can be solved by avoiding redeposition
accumulation at the sid...