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.
Chemically amplified resists have been used in the EUV lithography. The basic additive, called a quencher, has been added to the resist formula to control acid diffusion. In this study, the effects of photodecomposable quencher (PDQ) concentration on the chemical gradient (an indicator for LER) in chemically amplified EUV resist processes were investigated. The chemical gradients were simulated on the basis of the sensitization and reaction mechanisms for different half-pitchs, sensitivities, photoacid generator (PAG) concentrations, PDQ concentrations, and the effective reaction radii for deprotection. The simulation results analyzed using least square, lasso, Ridge, and elastic net regressions are discussed.
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.
High-volume production of semiconductor devices by extreme ultraviolet (EUV) lithography has started since 2019. A high numerical aperture tool is planned to extend the use of EUV lithography. The trade-off relationships between resolution, line edge roughness (LER), and sensitivity are a significant concern for the extendability of EUV lithography. In previous study, the dependences of chemical gradient (an indicator of LER) on the half-pitch of line-and-space patterns, the sensitivity, the sensitizer concentration, and the effective reaction radius for deprotection were investigated using a simulation on the basis of the sensitization and reaction mechanisms of chemically amplified EUV resists. Although the relationships between resolution, LER, and sensitivity were formulated in the half-pitch range lager than 10 nm, they were deviated from the equations in the sub-10 nm half-pitch resolution region. Recently, the application of information science to the material engineering has attracted much attention. In this study, the feasibility of the application of machine learning to the analysis of trade-off relationships was investigated. The sub-10 nm region was fitted well using lasso.
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