<title>Dissolution kinetics of high-resolution novolac resists</title>

Abstract

Dissolution kinetics, as well as the formation mechanism of a surface insoluble layer produced by dipping into TMAH (tetramethylammonium hydroxide) developer, have been investigated. In the previous paper, we mentioned that dissolution rate characteristics of high resolution novolac resist are clearly divided into three regions. To investigate this dissolution mechanism, we evaluated the temperature dependence of R (Dissolution rate) by changing the exposure dose, PAC (photoactive compound equals dissolution inhibitor) and the TMAH concentration. From Arrhenius Plots of these resist systems, it is considered that R is determined by two competitive reactions in the presence of TMAH; i.e., (a) the complex formation between PAC and novolac resin which produces dissolution inhibition effect, (b) TMAH induced deprotonation of phenolic hydroxy groups in novolac resin which accelerates the dissolution of the resist. Furthermore, we also describe the formation mechanism of a surface insoluble layer produced by dipping into a TMAH developer followed by water rinse, on the basis of the dissolution time of this layer (ts). The resist surface was also analyzed by using FT-IR (Fourier transform infrared spectroscopic measurement) and XPS (X-ray photoelectron spectroscopy). As a result, it was found that (a) water rinse is essential for the surface insoluble layer formation, (b) the ts value is not directly correlated with PAC accumulation in the resist surface and (c) the ts value becomes longer when the amount of penetrated TMAH into the resist increases. These results suggest that the surface insoluble layer is produced via water rinse of PAC-novolac complex described above.