Mechanism of Extreme Ultraviolet Photoresist Development with a Supercritical CO₂ Compatible Salt

Abstract

The mechanism of developing an extreme ultraviolet (EUV) commercial photoresist with supercritical carbon dioxide (scCO2) and a CO2 compatible salt (CCS) solution was studied. The cloud point of CCS in CO2 and the pressure at which the photoresist dissolves in CCS/scCO2 were determined for temperatures between 35 and 50 degrees C. For this temperature range, it was found that the CCS cloud point ranges between 11.2 and 16.1 MPa, while the photoresist dissolution point ranges from 15.5 to 21.3 MPa. The kinetics of the CCS/scCO2 development was modeled using a simplified rate equation, where the rate-limiting steps were photoresist dissolution and mass transfer. The effects of temperature, mass transfer, pressure, and CCS concentration on photoresist removal rate were further explored experimentally using a high-pressure quartz crystal microbalance (QCM). Increasing temperature (35-50 degrees C) at a constant fluid density of 0.896 g/mL was found to increase the removal rate following an Arrhenius behavior with a photoresist dissolution energy of activation, Ea, equal to 79.0 kJ/mol. The removal was zero order in CCS concentration, signifying photoresist phase transfer, photoresist mass transfer, or both were rate limiting. Mass transfer studies showed that circulation enhanced the photoresist removal rate, but that the mass transfer coefficient was independent of temperature from 35 degrees C to 50 degrees C. In pressure studies, increasing pressure (27.6-34.5 MPa) at a constant temperature of 40 degrees C increased the removal rate by enhancing the fluid density, but at 50 degrees C increasing pressure had little effect on the removal rate. When the total CCS concentration was in large global excess over the number of Bronsted acid groups in the polymer (2400:1 at 5 mM CCS concentration), the mass of photoresist removed varied linearly with time. At lower CCS concentrations but still in global excess of the number of Bronsted acid groups, the photoresist removal slowed (0.5 mm CCS, approximately 240:1) or was prevented (0.03 Mm CCS, approximately 15:1) due to partitioning of the CCS between the CO(2)-rich phase and the film. The CCS partitioning into the resist was found to decrease with increasing temperature, revealing an enthalpy-driven CCS absorption.

Synthesis and structural characterization of CO2-soluble oxidizers [Bu4N]BrO3 and [Bu4N]ClO3 and their dissolution in cosolvent-modified CO2 for reservoir applications

“…There is precedent for dissolving ionic compounds by uorinating either the cation or both the cation and anion. 28 Fluorinated alkylammonium cations are expected to be moderately soluble, but the scale of the application would prevent widespread adoption due to the cost prohibitive nature of uorinated compounds. There is some evidence for improving the solubility of salts in CO 2 by exchanging alkali cations for tetraalkylammonium cations.…”

Sorption of CO2 and a CO2 Compatible Salt into an Extreme Ultraviolet Photoresist Film on a SiO2 Substrate

“…QCM apparatus: (A) CO 2 cylinder, (B1−B5) valves, (C) syringe pump with water jacket, (D) preheating coil, (E) pressure transducer, (F) QCM high pressure cell, (G) thermocouple, (H) stand, (I) circulator and heater for water bath, (J) water bath, (K) phase lock oscillator, (L) frequency counter, (M) signal conditioning connector block, (N) computer, (O) feed through connection, (P) high pressure feed through, (Q) O-ring, and (R) quartz crystal. , …”

“…For the sorption measurements with the photoresist film, 1−2 h were needed for equilibration. The setup and conversion of frequency to mass are given in more detail elsewhere. , …”

“…The setup and conversion of frequency to mass are given in more detail elsewhere. 6,21 Results and Discussion CO 2 and CO 2 /CCS Adsorption onto the Bare SiO 2 Substrate. With only CO 2 added to the QCM cell by step pressurization, the amount of excess CO 2 adsorbed onto the QCM crystal SiO 2 substrate was measured.…”

Effect of Acrylic and Epoxy Hybrid Crosslinker on the Mechanical Strength of Photocurable Resin for 3D Printing

“…Only one layer (micrometer scale) is cured at a time and is very thin; therefore, it is possible to form high-definition and smooth surfaces [4]. By taking advantage of this feature, SLA is applied to photoresists [5] and dental materials [6]. Research on shape memory [7] and self-healing [8] materials is also in progress.…”