Photoresists: Then, Now and The Future
As you know, photoresists are a very important part
of what you do, and although you may not have realized
it, photoresist technology is now 170 years old. In
what follows, I would like to lead you in a narrative
though some highlights of this history.
If you happen to travel to France and visit the city of
Lyon, you will see a wonderful museum dedicated to
the art and science of photography. Then, on display, is
an example of probably the first photoresist material,
an asphaltum, discovered by Niepce in 1826. The
records show that 14 years later, Becquerel produced
the first sensitized natural colloid photoresist, gelatin
sensitized with dichromate, and for this, he received
one of the first British Patents, number 565.
In the earlier days, attention was mostly focused on
proteins such as gelatin, fish glue, albumin and casein.
To this day, gelatin is still used in the screen stencil
industry, and fish glue and casein are still used in photochemical
machining. As you can imagine, the use of
naturally-occurring proteins can lead to unpredictability
and inconsistency in a process. Therefore, the
next step forward was to try to utilized synthetic colloids
and polymers as the matrix.
Dr. Melvin A. Lipson, Lipson Associates