Monitoring photoresist dissolution in supercritical carbon dioxide using a quartz crystal microbalance

Zweber, Amy E.; Carbonell, Ruben G.

doi:10.1117/12.655659

Cited by 3 publications

(8 citation statements)

References 22 publications

(24 reference statements)

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“…Complete details of the QCM apparatus and development procedure were discussed in detail elsewhere. 3 The cell temperature and pressure were monitored with a thermocouple and pressure transducer. Previous results have shown that the CCS development rate is directly proportional to temperature 5 , and that complete photoresist removal in less than one minute is possible at 80°C 4 .…”

Section: Development Proceduresmentioning

confidence: 99%

“…3,4 This paper addresses what effects using a preconditioning CO 2 drying step before development and using a hexamethyldisilazane (HMDS) adhesive coating have on the photoresist removal rate and the effectiveness of photoresist removal.…”

Section: Introductionmentioning

confidence: 99%

“…1, 2 To understand the kinetics and overall mechanism of photoresist dissolution into the high pressure CCS/scCO 2 solution, a quartz crystal microbalance (QCM) was previously used to measure the effects of temperature, pressure, and density on the photoresist removal rate. 3,4 In this paper, the effects of a CO 2 drying step before development and an adhesive coating on the photoresist removal rate and the formation of residual photoresist droplets were studied at 50°C and 5000 psi. The results implied that neither the CO 2 drying step nor the HMDS coating had an effect on the bulk photoresist removal rate.…”

mentioning

confidence: 99%

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Photoresist dissolution into a CO 2 compatible salt and CO 2 solution: investigation of processing conditions

Zweber

Wagner²,

Carbonell

2007

SPIE Proceedings

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New lithographic techniques are being implemented to help further reduce feature sizes in microelectronics. A technique for the development of standard extreme ultraviolet (EUV) photoresists in a carbon dioxide compatible salt (CCS) and supercritical carbon dioxide (scCO 2 ) solution is being investigated to reduce line edge roughness and image collapse of high aspect ratio features. 1, 2 To understand the kinetics and overall mechanism of photoresist dissolution into the high pressure CCS/scCO 2 solution, a quartz crystal microbalance (QCM) was previously used to measure the effects of temperature, pressure, and density on the photoresist removal rate. 3,4 In this paper, the effects of a CO 2 drying step before development and an adhesive coating on the photoresist removal rate and the formation of residual photoresist droplets were studied at 50°C and 5000 psi. The results implied that neither the CO 2 drying step nor the HMDS coating had an effect on the bulk photoresist removal rate. It was also found that using an HMDS adhesive coating reduces residual photoresist droplet size on the substrate due to the lower substrate / photoresist surface energy.

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Section: Development Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Photoresist dissolution into a CO 2 compatible salt and CO 2 solution: investigation of processing conditions

Zweber

Wagner²,

Carbonell

2007

SPIE Proceedings

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“…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. , …”

Section: Methodsmentioning

confidence: 99%

“…One technique that achieves reduction of both pattern collapse and LWR utilizes supercritical carbon dioxide (scCO 2 ) and a carbon dioxide compatible salt (CCS) to develop standard EUV photoresists. − The CCS/scCO 2 one-step development process takes advantage of the low surface energy of scCO 2 to help prevent image collapse and the plasticizing properties of CO 2 in the polymer to help reduce LWR. The effects of temperature, mass transfer, pressure, and CCS concentration on photoresist removal rate were previously explored using a high pressure quartz crystal microbalance (QCM) . The QCM studies in this paper provide details of adsorption, absorption, and diffusion behavior of CO 2 and the CCS at 35 and 50 °C.…”

Section: Introductionmentioning

confidence: 99%

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

2009

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The development of standard extreme ultraviolet (EUV) lithography photoresists with a CO2 compatible salt (CCS) and supercritical carbon dioxide (scCO2) solution has several advantages over typical trimethylammonium hydroxide development, including reduced image collapse and line width roughness in the resulting microchip features. The mechanism and characteristics of the CCS/scCO2 development process are currently being examined. In this paper, the sorption behavior of CO2 and the CCS onto a bare SiO2 surface and into the photoresist was studied using a quartz crystal microbalance (QCM). From the adsorption studies of CO2 and CCS/CO2 onto a bare SiO2 surface, it was found that the CCS begins to adsorb at 8.0 MPa at a temperature of 35 degrees C and at 9.4 MPa at a temperature of 50 degrees C. The adsorption of the CCS was favored and driven by entropy changes. The absorption of CO2 into the glassy photoresist resin was also measured with QCM and found comparable to CO2 absorption in glassy polystyrene for 35 and 50 degrees C up to a pressure where the photoresist is believed to dewet from the substrate. The diffusion behavior during CO2 absorption was found to be comparable to that of small fluorescent molecule diffusion in a CO2 swollen polystyrene.

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

Zweber

Wagner²,

DeYoung

et al. 2009

Langmuir

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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.

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Monitoring photoresist dissolution in supercritical carbon dioxide using a quartz crystal microbalance

Cited by 3 publications

References 22 publications

Photoresist dissolution into a CO 2 compatible salt and CO 2 solution: investigation of processing conditions

Photoresist dissolution into a CO 2 compatible salt and CO 2 solution: investigation of processing conditions

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

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

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Monitoring photoresist dissolution in supercritical carbon dioxide using a quartz crystal microbalance

Cited by 3 publications

References 22 publications

Photoresist dissolution into a CO 2 compatible salt and CO 2 solution: investigation of processing conditions

Photoresist dissolution into a CO 2 compatible salt and CO 2 solution: investigation of processing conditions

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

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

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Product

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

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