Hardware Reference
In-Depth Information
The head-microactuator-slider assembly is fabricated in an integrated fab-
rication process described below.
1. Releasing slots on back of the silicon wafer are etched by DRIE. There are
two etching steps, one for releasing movable parts (including springs and
head plate) and the other for reducing the height of the wire structures.
Different heights of the structures can thus be formed from the backside
of the wafer.
2. The patterned silicon wafer is bonded to a slider wafer using adhesive
bonding. The thickness of the SU-8 bonding layer is approximately 10
3. Magnetic heads are fabricated together with its microactuator processes
on the front-side of the silicon wafer. Silicon dioxide (SiO 2 )layer is used
as hard etching mask to fabricate microactuator structures.
4. The silicon-AlTiC bonded wafers are diced into bars and air-bearing rails
are fabricated on the dicing surface which is perpendicular to the wafer
5. DRIE is used to release the movable part of the microactuator.
The frequency response of such an electrostatic microactuator driving the
headisshowninFigure3.70. Theresponseismeasuredonaprobesta-
tion [136]. Figure 3.71 highlights the movable part that has the 1st resonant
frequency at 15.4 kHz in the XZ plane in an FEM model.
3.6.4 Microactuator for Controlling Head-Media Spacing
With the increase of recording density of HDD to above 100 Gb/in 2 ,acon-
stant flying height of approximately 10 nm or smaller is required. Variations
in flying height are contributed by (1) manufacturing tolerances, (2) environ-
mental changes such as atmospheric pressure change, and (3), slider localized
heating by writing current induced slider crown and chamber variation, and
many more. Adjustment of the spacing between the read/write head and the
recording media, i.e., the height (z-direction) of the read/write head with re-
spect to the slider can be effectuated using a microactuator integrated in the
slider. Such a possibility was studied in tandem with the study of lowering the
slider flying height [223].
Onesuchdesignadoptstheconfiguration of an active head slider with
PZT unimorph cantilever structure which can be fabricated monolithically
using silicon micro machining. The active head sliders were fabricated using
micro machining process, which includes spin-coating of the sol-gel PZT, ABS
etching, and deep RIE for forming cantilevers of about 50 µm thickness. The
usual pads on the slider generate high pressure to support the load. The
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