Positive photoresists comprising a novolak resin made from 2,3-dimethyl phenol,2,3,5-trimethylphenol and aldehyde with no meta-cresol present

Granted: Jun 21, 1994 Filed: Mar 24, 1993

This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.