Fall 1995
Dr. Melvin A. Lipson, Lipson Associates
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.
