Electrostatic effect on the dissolution kinetics of poly(4-hydroxystyrene) in alkaline aqueous solution

Abstract

The effects of pH and ionic strength on the dissolution behavior of poly(4-hydroxystyrene) (PHS) in alkaline solution were studied to gain a fundamental understanding of the dissolution of chemically amplified resists. Tetramethyl ammonium hydroxide, which is a standard developer in recent lithography, and its corresponding salts were used. Dynamic light scattering (DLS) and quartz crystal microbalance (QCM) methods were used to study the state of PHS chains in solution and the dissolution behavior of PHS films, respectively. In DLS, higher pH and ionic strength caused PHS chains to become more dispersed owing to an increase in the number of dissociated acidic groups and the resulting increase in repulsive force. The results of the QCM method showed that the diffusion of the polymer into the liquid phase from the film corresponds to an increase in the number of dissociated acidic groups, but not correspond to the magnitude of transient swelling.

Dissolution dynamics of partially protected poly(4-hydroxystyrene) in tetraalkylammonium hydroxide aqueous solution

“…Note that the dissolution mode in a diluted TMAH developer has been reported to change to a dissolution mode similar to the TProAH developer at a thickness larger than 500 nm in the narrow TMAH concentration range. 30,31) The effect of PHS film thickness on dissolution and swelling behavior in TEAH was analyzed. When the protection ratio was low, the thickness dependence of the dissolution rate (the slope of the frequency change) was small, as shown in Fig.…”

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

“…12,14) In this study, such a change in dissolution kinetics is called the dissolution mode change. The TAAH concentration, 12,14,15) the protection ratio of the hydroxyl groups of PHS, 12,14,15) the decomposition of acid generators dispersed in PHS films, 13,17) the molecular weight, 18) the polydispersity, 19) the electrostatic interaction, 20) and the interaction of PHS with the underlayer 21) have been investigated from the viewpoint of their effects on the PHS dissolution kinetics.…”

Dissolution dynamics of poly(4-hydroxystyrene) in potassium hydroxide (KOH) and sodium hydroxide (NaOH) aqueous solutions investigated by quartz crystal microbalance (QCM) method

“…Tetrabutylammonium hydroxide (TBAH) is a typical organic alkali for the alternative alkaline developer. [16][17][18][19][20] The fundamentals of the dissolution dynamics in tetraalkylammonium hydroxide (TAAH) aqueous solution have been investigated in terms of the TAAH concentration, [20][21][22] the protection ratio of the hydroxyl groups of PHS, [20][21][22] the decomposition of acid generators dispersed in PHS films, 23,24) the molecular weight of PHS, 25) the polydispersity of PHS, 26) the electrostatic interaction of ionized PHS, 27) and the interaction of PHS with the underlayer. 28) Among them, the molecular size of the tetraalkylammonium cation was reported to significantly affect the dissolution dynamics of PHS films.…”