Spring 1988
Photoforming Intricate Articles in Thickened High Definition Photoresist
The well established process of photoforming1 can
be used to make metal components with intricate
plan-view detail in the range of a few micrometres.
Such articles include transmission electron
microscope specimen grids. Fig 1. aperture discs for
use in electron optics, evaporation masks2 and
micro-Fresnel zone plates 5.
The ratio (thickness/resolvable line width) of
features. eg bars and gaps. in photoformed articles is
defined as the aspect ratioJ . Established production
[echnology has been used [0 produce articles
approximately 10J1m thick with an aspect ratio of
approximately 1.0, eg Fig 1(c). There is. however. a
requirement for components with features in the
range 5 11m. or less. with an aspect ratio of about
2.0, ie a thickness of about 10Jim, tor adequate
mechanical strength. There is also a requirement for
thicker components, up to 50 11m. which retain as
much fine detail as possible,
The present work shows that photoforming can
be used to produce components from 10 10 30/lm
thick with an aspect ratio of 2.0, or higher in some
cases.
Dr. David Allen and P.J. Hampson, Cranfield Institute of Technology
