A wide range of molecular weights (3500 to 240000) of poly(p- vinyl)phenol was studied. Polymer dissolution rate vs. molecular weight followed a simple kinetic equation, with the kinetic order m equals2.0. The photospeed of the resist was not strongly affected by the starting resin molecular weight; however, resolution decreased rapidly with increasing M_w. Also, the higher the starting molecular weight, the greater the tendency for the resist to form microbridges between features. The microbridges could be as long as 1.0micrometers for the highest molecular weight resin, M_w equals240000. The lowest molecular weight resins, M_w <EQ5000, showed no evidence of microbridges even at the resolution limit of the stepper, 0.32micrometers , with 0.14N development. However, higher normality developer, such as 0.26N TMAH, showed microbridges across 0.42micrometers features with M_w equals3500 resin. For comparison, a m,p-cresol novolak, also 3500 molecular weight, showed no evidence of microbridging in the higher normality developer. The reason for this difference is that the novolak does not crosslink as effectively as PVP does. Based on extraction experiments, it has been shown that the molecular weight at a sizing dose is 164000 for PVP and 6500 for the novolak. Thus, the novolak must react with the melamine primarily through an intrachain reaction, whereas the PVP- melamine reaction is an interchain reaction. Finally, a mechanism for microbridge formation is discussed.

Date Published: 16 May 1994
PDF: 12 pages
Proc. SPIE 2195, Advances in Resist Technology and Processing XI, (16 May 1994); doi: 10.1117/12.175332

Published in SPIE Proceedings Vol. 2195:
Advances in Resist Technology and Processing XI
Omkaram Nalamasu, Editor(s)