Optical Alignment of Thin Film Heads using High-Contrast Targets

Optical Alignment of Thin Film Heads using High-Contrast Targets

      Disclosed is a means for obtaining very good information from
optical alignment targets during the photo process operations.

      During the fabrication steps of the thin film heads, the
alignment structures used to reference one photolithographic level to
a proceeding one are severely distorted.  The principal contributors
of the targets' degradation are the coating with dielectric layers
and the chemical and vacuum etchings of said layers.

      To produce the maximum possible acquity of the targets'
signals, the disclosed procedure is to etch an opening atop the
planarizing dielectric layers, thus enabling the optical patterning
tools to obtain sharp, diffracted signals from the original buried
targets.

      The opening of the planarizing layers is accomplished via a
photolithographic step followed by a chemical etching step.  Between
these layers of Al2O3 material, the etching solution is H2PO3
acid/H2O.  In the event that these layers are covered with a metallic
layer, this layer will have to be removed first with an appropriate
etching solution.

      Disclosed anonymously.