All photoresists have finite shelf lives where lithographic properties and performance remain within acceptable specified ranges. Slow but perceptible decomposition of the diazonaphthoquinone (DNQ) photoactive compounds (PAC) result in the evolution of nitrogen gas and acidic by-products which may begin to affect functional behavior. This study looks at the relative increase in acidity of aged PAC solutions using a very sensitive spectrophotometric measurement technique based upon Congo red indicator (see accompanying paper 3049- 49). The technique was used to assess the main resist component combinations which accelerate acid generation. Major effects indicated that particular combinations of PAC isomer and solvent greatly affected the reactive generation of acidic species in solution. In general, the 2,1,5 isomers of both novolac-based or hydroxylated benzophenone PACs were less stable than their 2,1,4 counterparts in all of the tests. The supposition that acidity was caused by PAC decomposition was substantiated by degassing studies which parallelled the acid measurements indicating that the 2,1,5 PACs were less stable than the 2,1,4 isomers. Results may be useful in formulating resists with extended shelf lives.

Date Published: 7 July 1997
PDF: 11 pages
Proc. SPIE 3049, Advances in Resist Technology and Processing XIV, (7 July 1997); doi: 10.1117/12.275857

Published in SPIE Proceedings Vol. 3049:
Advances in Resist Technology and Processing XIV
Regine G. Tarascon-Auriol, Editor(s)