In situ study of hydrogen silsesquioxane dissolution rate in salty and electrochemical developers

In order to better characterize the development of the electron-beam resist hydrogen silsesquioxane (HSQ), the authors used a quartz crystal microbalance (QCM) to study its rate of dissolution in situ. The authors determined the effect of both salt concentration and applied electric potential on the development rate of HSQ. The development rates were measured by spinning HSQ directly onto a quartz crystal resonator, and then developing in a QCM microfluidic module. In order to more directly observe the effect of electric potentials on the HSQ development rate, a film of HSQ was partially cross-linked in an O-2 plasma asher and then developed in the QCM flow module with a salt-free NaOH solution. As the partially cross-linked HSQ slowly developed, electric potentials were applied and removed from the crystal allowing the observation of how the development rate increased upon the application of a positive electric potential. The increased development rate caused by both the addition of salt ions and a positive electric potential suggests that the rate may be limited by a build-up of negative charge on the HSQ. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3644339]