Browse Prior Art Database

PLANARIZED MR HEAD

IP.com Disclosure Number: IPCOM000013051D
Original Publication Date: 2000-Feb-01
Included in the Prior Art Database: 2003-Jun-12
Document File: 3 page(s) / 56K

Publishing Venue

IBM

Abstract

In the present day thin film magnetic head fabrication there are several processing issues to be considered. The most critical of the process parameters is the dimension of the second ferromagnetic pole tip which defines the size of the written track. That size is the one that controls the "Track per Inch" or track recording density. The pole tip fabrication deals with a lithographic step where the size of the final pole tip is obtained in a thick layer of photoresist . It is extremely important that all the key parameters controlling the photo exposure of said resist layer are controlled and maintained nominal through wafer to wafer processing. Besides the classical photo parameters of exposure dose, focus, and the development cycle the most important parameter left is resist coating uniformity and mean thickness. The thin film heads are made with structures such as Cu coils and resist insulators defining the back edge of the pole region. The back edge slanted profile may be of a thickness between 5 to 10 um at the top of the insulation stack for single layer coils. The entire insulation stack (with the coils within) also is fabricated atop two other thick structures. One is the First Shield of the read head (S1) generally of a thickness of 2 to 4um. The second one (which is placed just under the insulation stack) is the Second Shield (S2) and first ferromagnetic layer (P1) of a merged write head. This last one generally of a plated permalloy of a thickness between 3 to 4um.

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PLANARIZED MR HEAD

   In the present day thin film magnetic head fabrication there are several
processing issues to be considered. The most critical of the process parameters
is the dimension of the second ferromagnetic pole tip which defines the size of
the written track. That size is the one that controls the "Track per Inch" or
track recording density. The pole tip fabrication deals with a lithographic step
where the size of the final pole tip is obtained in a thick layer of photoresist
. It is extremely important that all the key parameters controlling the photo
exposure of said resist layer are controlled and maintained nominal through wafer
to wafer processing. Besides the classical photo parameters of exposure dose,
focus, and the development cycle the most important parameter left is resist
coating uniformity and mean thickness. The thin film heads are made with
structures such as Cu coils and resist insulators defining the back edge of the
pole region. The back edge slanted profile may be of a thickness between 5 to 10
um at the top of the insulation stack for single layer coils. The entire
insulation stack (with the coils within) also is fabricated atop two other thick
structures. One is the First Shield of the read head (S1) generally of a
thickness of 2 to 4um. The second one (which is placed just under the insulation
stack) is the Second Shield (S2) and first ferromagnetic layer (P1) of a merged
write head. This last one generally of a plated permalloy of a thickness between
3 to 4um.

 The combined step between the first and second shields (P1) could be as thick as
6um or more. If we combine the step problem just described with the insulation
stack behind the pole tip region we obtain a very dramatic source for resist
coating non-uniformities. The resist coating variation does result in pole tip
size variation or impossibility of fabrication altogether. We can try methods of
stack height reduction by altering the design of the inductive head such as was
done in the Low Profile and/or Sunken Designs. In both cases the emphasis was to
lower the sensitivity of the insulation stack to produce uneven resist coatings.
Still a very large source of coating non-uniformity resides with the S1/S2
processing step.

 By modifying the photoresist mask used to insulate the coils (under and on top)
we can simultaneously add the same photoresist layer at the coils reg...