Understanding the interaction of resist materials with the underlayers is important for the development of highly resolving resist materials. The effect of the surface free energy of the organic underlayer on the dissolution kinetics of poly(4-hydroxystyrene) (PHS) film in a tetramethylammonium hydroxide (TMAH) aqueous developer was investigated by the quartz crystal microbalance (QCM) method. By using 0.95 wt% TMAH standard developer, we observed the correlation between the polar component of the surface free energy of the underlayer and the interaction area of the QCM chart (impedance) near the end of PHS dissolution. The interaction area was defined by the product of impedance change and time. The interaction of the hydroxyl groups of PHS with the underlayer increased with the polar component of the surface free energy of the underlayer. The analytical method developed in this study is useful for the investigation of the resist-underlayer interaction during development.
Tetramethylammonium hydroxide (TMAH) aqueous solutions has been used as a developer for chemically amplified resists (CARs), dissolving polymer with polar groups generated by exposure. Although the dissolution kinetics of CARs has been widely studied, it is necessary to understand molecular-level information such as interaction between polymer chains, to consider the dissolution of thin and minute resist films that are used nowadays. In this study, we used dynamic light scattering (DLS) to study the state of PHS chains in TMAH aqueous solution. The effect of the concentration of each ionic species on dispersion of PHS chains was investigated using solutions whose base concentrations were changed by two methods: dilution with pure water and neutralization with acid. PHS chains were well dispersed as the base concentration and ionic strength of the solution increased, while they aggregated as these two factors decreased. We also studied the dissolution behavior of PHS films under nearly identical conditions using quartz crystal microbalance (QCM). The dissolution of the films was also affected by the two factors described above. In addition to this, with the decrease in the above two factors, we observed formation of large swollen layer as we have reported in the past. We assumed these effects on dissolution of films were mainly due to the acid-base equilibrium at the solid-liquid interface.
Photoresists have been widely used as patterning materials for electric devices such as displays and semiconductor. Understanding pattern formation mechanism is essential for the efficient development of resist materials. In this study, we investigated the dissolution kinetics of poly(4-hydroxystyrene) (PHS) with weight-average molecular weights (Mw) of 9000-30000 and molecular weight distribution (Mw/Mn) of 1.07-1.20. The dissolution kinetics of PHS films was observed in tetramethylammonium hydroxide (TMAH) aqueous developers using a quartz crystal microbalance (QCM) method. The TMAH concentration was changed from 0 to 2.38 wt%. The obtained data were analyzed using polynomial regression to clarify the effects of Mw and Mw/Mn on the dissolution kinetics of PHS films. From the results of analysis, both dissolving and swelling behavior largely depended on Mw/Mn. Mw had a little effect on the dissolving, and however, had a large effect on the swelling in dilute TMAH aqueous solution.
In the development of highly resolving and highly sensitive resist materials, stochastic phenomena (LER and stochastic defect generation) are a critical issue. In this study, the dependence of the transient swelling layer formation of resist backbone polymer on its molecular weight and dispersion was investigated for the development of highly resolving resist materials. The dissolution kinetics was measured for different molecular weights and dispersions using quartz crystal microbalance (QCM) method. The relationship between transient swelling layer and stochastic defect formation is discussed.
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