Relationship between poly(4-hydroxystyrene) (PHS) and tetramethylammonium hydroxide (TMAH) concentrations during the development of PHS films in TMAH aqueous solution studied by a quartz crystal microbalance (QCM) method

Abstract

The development (the dissolution of resist films in developer) is an important process of lithography. However, the details of the dissolution of resist polymers remain unclarified. In this study, the viscosity of 2.38 wt% tetramethylammonium hydroxide (TMAH) aqueous solution with poly(4-hydroxystyrene) (PHS) was investigated by a quartz crystal microbalance method. The relationship between PHS concentration and the viscosity of 2.38 wt% TMAH aqueous solution with PHS was measured. The kinetics (temporal change) of viscosity and PHS concentration during development was clarified. The maximum PHS concentration reachable during development approximately corresponded to the TMAH concentration independently of the film thickness.

Dissolution dynamics of poly(4-hydroxystyrene-co-methacrylic acid) in tetraalkylammonium hydroxide aqueous solutions

“…In the case of PHS films, the concentration of hydroxystyrene units under the saturated condition approximately agreed with the alkaline concentration. 25) The proportionality constants obtained from the calibration curves are listed in Table II. At monomer concentrations lower than the saturated concentration, the monomer concentration is proportional to the impedance change caused by the change in monomer concentration.…”

“…At monomer concentrations lower than the saturated concentration, the monomer concentration is proportional to the impedance change caused by the change in monomer concentration. 25) The baselines of impedance charts obtained by the QCM method were determined by fitting the following equation to the experimental data. 21)…”

“…24) The impedance change is related to the viscosity change of films and/or developers. 25) When the polymer concentration C p is lower than the concentration of saturated solution C saturation , the relationship between impedance change ΔZ and C p can be expressed by…”

“…α Z and C saturation were obtained in accordance with the reported procedure. 25) In this study, C p is expressed using an average monomer molecular weight M ave defined by…”

“…The details of measurement procedures have been reported elsewhere. 17,25) The dynamic light scattering (DLS) analysis was carried out using a nanoPartica SZ-100V2 from HORIBA. PHSMA was dissolved in TAAH aqueous solutions.…”