Although Parylene C cannot be patterned lithographically like photoresists, it nevertheless extends the range of processing options by offering a set of properties that are suitable for microfabrication and are complementary to those of photoresists. The compatibility of Parylene C with several microfabrication processes was demonstrated in experiments in which a thin film of Parylene C was deposited on a silicon wafer, then several thin metal films were deposited and successfully patterned, utilizing the Parylene C pads as a sacrificial layer.
The term "parylene" — a contraction of "poly(para-xylene)" — denotes a family of vapor-deposited polymers. In Parylene C (the most common form of parylene), a chlorine atom is substituted for one of the hydrogen atoms on the benzene ring of each para-xylene moiety. Heretofore, parylenes have been used as conformal coating materials in diverse applications.
The unique combinations of processing properties of Parylene C that make it suitable for use in microfabrication are the following:
- It can be deposited to uniform submicron thickness.
- It is highly resistant to solvents and, therefore, able to survive wet processing.
- It can easily be patterned or removed by use of oxygen plasma.
- Because it cannot be easily patterned or removed by means other than oxygen plasma, it can withstand many dry etching processes.
- It has little or no outgassing and is fully functional at cryogenic temperatures.
This work was done by Michael Beamesderfer of Goddard Space Flight Center. This invention is owned by NASA, and a patent application has been filed. Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to the Patent Counsel, Goddard Space Flight Center, (301) 286-7351. Refer to GSC-14803-1.