Phase Behavior and Modeling of CO<sub>2</sub>/Methanol/Tetramethylammonium Bicarbonate and CO<sub>2</sub>/Methanol/Tetramethylammonium Bicarbonate/Water Mixtures at High Pressures

Levitin, Galit; Bush, David; Eckert, Charles A.; Hess, Dennis W.

doi:10.1021/je0302351

Cited by 16 publications

(12 citation statements)

References 42 publications

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“…Under these conditions, the mixture is in a single phase. 18 The sample was then rinsed in methanol and dried under vacuum. The FTIR spectrum of this sample was compared to the spectrum of an untreated sample; results are shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Compatibility of high pressure cleaning mixtures with a porous low dielectric constant film: A positronium annihilation lifetime spectroscopic study

Myneni

Peng

Gidley

et al. 2005

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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High pressure CO2 based cleaning mixtures have recently been proposed as an environmentally benign approach for postplasma etch residue removal. These mixtures must remove etch residues without damaging the low-k dielectric film that will be used to isolate interconnect structures in future generation devices. In this work, the compatibility of a CO2-based mixture with a porous low-k film is evaluated. Positronium annihilation lifetime spectroscopy (PALS) is used to monitor the change in pore size and film chemistry in a porous methyl silsesquioxane film after treatments under several different elevated pressure conditions. Spectroscopic ellipsometry and infrared spectroscopy are used to complement the PALS technique in order to better understand cleaning mixture effects on the dielectric film. CO2–TMAHCO3–methanol mixtures cause negligible changes in pore dimensions and bulk composition of the film. The high pressure treatments cause a small decrease in positronium formation which may be attributed to contamination in the high pressure system.

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Section: Resultsmentioning

confidence: 99%

Compatibility of high pressure cleaning mixtures with a porous low dielectric constant film: A positronium annihilation lifetime spectroscopic study

Myneni

Peng

Gidley

et al. 2005

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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“…Composition of the GXL was assumed to be at equilibrium; thus, a vapor liquid-phase diagram based on CO 2 and the particular additive allowed determination of the fluid composition. 16 Thin films for removal studies were formed on silicon wafers by spin casting from a PHOST solution ͑15 mass % in propylene glycol methyl ether acetate, Mw = 12,000, PDI = 6.4͒ at 800 rpm. Prior to spin casting, the silicon wafer was cleaned by immersion in dilute ͑1:50͒ hydrofluoric acid to remove the native oxide layer.…”

Section: Methodsmentioning

confidence: 99%

Photoresist and Residue Removal Using Gas-Expanded Liquids

Song

Spuller

Levitin

et al. 2006

J. Electrochem. Soc.

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Rapid technology development and demands for state-of-the-art generations of integrated circuits bring new challenges to microelectronic device manufacture. Specifically, decreasing dimension sizes may limit the effectiveness of liquid-based removal of photoresist and plasma etch residues. In addition, the hazardous solvents currently in use pose environmental concerns. Gasexpanded liquids ͑GXLs͒ and supercritical fluids may offer cleaning or residue removal approaches that overcome some of the drawbacks of current surface preparation methods. Removal of PHOST ͑polyhydroxystyrene͒ photoresist films has been demonstrated with CO 2 -expanded ethanol ͑up to 75 mol % CO 2 ͒, indicating that the inclusion of CO 2 does not inhibit photoresist removal. In situ interferometry measurements of the PHOST layers allowed insight into the removal mechanism. The GXL mixtures were also invoked to remove post-plasma etch residues using CO 2 -expanded TMAHCO 3 /CH 3 OH. At a temperature of 90°C and pressures above 1000 psig the GXL mixture removed the photoresist and etch residue. Cleaning efficiency depended on CO 2 pressure; at lower pressures the CO 2 reduced the mole fraction of the TMAHCO 3 /CH 3 OH while at higher pressures the CO 2 assisted removal.

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“…17 A boroscope and video camera allowed observation of phase equilibrium, and provided a significant magnification of the viewable area. Two platinum flag electrodes (5 ϫ 5 mm) were spot welded to Pt wires that served as the electrical leads for conductivity measurements.…”

Section: Methodsmentioning

confidence: 99%

“…[12][13][14][15][16] To optimize cleaning effectiveness, the phase behavior of various cleaning mixtures was investigated. 17 Results of these studies demonstrated the significance of the phase state of the cleaning mixtures: shorter cleaning times were required for complete removal when the cleaning mixture was in a single phase. Such observations indicate that an improved understanding of the chemical-physical properties of TMAHCO 3 /methanol/CO 2 mixtures enhances the ability to design CO 2 -based mixtures and establish specific temperature/pressure conditions for residue removal.…”

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confidence: 97%

Ionic Conductivity of Elevated Pressure TMAHCO[sub 3]/MeOH/CO[sub 2] Mixtures

Levitin

Hess

2005

Electrochem. Solid-State Lett.

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Carbon-dioxide-based elevated pressure cleaning mixtures for photoresist and plasma etch residue removal are being considered as alternative environmentally benign approaches for back end of line microelectronic device manufacture. Despite many attractive features, CO 2 has little solvating power for photoresist or inorganic materials. Addition of a basic modifier such as tetramethylammonium bicarbonate (TMAHCO 3 ) to CO 2 , can yield a mixture suitable for residue removal. In this work, characterization of the TMAHCO 3 /methanol-modified fluids was performed by measuring the ionic conductivity as a function of concentration and mole fraction of CO 2 at room temperature and various pressures. The conductivity displays a strong dependence on the dielectric properties of the fluid medium.Due to the ongoing demand for faster and more reliable microelectronic devices and integrated circuits ͑ICs͒, IC manufacturing is facing significant challenges; these include continuous device miniaturization and incorporation of new materials into process sequences, while abating environmental concerns. 1 It is anticipated that some of these challenges will be met by the use of sub-and super-critical CO 2 in various surface cleaning, preparation, and drying steps in IC processes. [2][3][4][5] Due to the easily attainable critical temperature ͑31°C͒ and pressure ͑74 bar͒, nonflammability, high availability, and low cost, CO 2 presents a very attractive environmentally benign approach for surface treatment in the microelectronics and microelectromechanical systems ͑MEMS͒ industries. In addition, fluids at conditions below their critical points, sometimes referred to as gas-expanded liquids ͑GXLs͒, may overcome the limitations of traditional solvents, pure CO 2 , and even super-critical mixtures of these components. 6 The physical properties of GXLs are intermediate between those of the pure gas and liquid components, suggesting that excellent mass transport and excellent solvent strength are possible in the same mixture. For example, the solvent strength of GXLs is much greater than that of gases or supercritical fluids, while the surface tension and viscosity of GXLs are much lower than that of liquids.One of the major drawbacks of elevated pressure CO 2 -based fluids is their nonpolar character ͑the dielectric constant is Ͻ2 at the critical point͒. This results in a limited solubility of highly polar ͑e.g., ionic͒ chemical moieties; therefore, dissociation of ionic compounds and thus the ionic conductivity of the fluids is low. 7 To effectively implement sub-or super-critical CO 2 mixtures in IC process applications, the solvating power must be improved. Solubility limitations can be addressed by the addition of polar modifiers or surfactants. [2][3][4][5][8][9][10][11] Recently we demonstrated that efficient photoresist and post plasma etch residue removal can be achieved upon addition of tetramethylammonium bicarbonate (TMAHCO 3 ) in methanol to CO 2 at elevated pressure and temperature (ϳ3000 psi, and 70°C͒. 12-16 To optimize c...

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Phase Behavior and Modeling of CO₂/Methanol/Tetramethylammonium Bicarbonate and CO₂/Methanol/Tetramethylammonium Bicarbonate/Water Mixtures at High Pressures

Cited by 16 publications

References 42 publications

Compatibility of high pressure cleaning mixtures with a porous low dielectric constant film: A positronium annihilation lifetime spectroscopic study

Compatibility of high pressure cleaning mixtures with a porous low dielectric constant film: A positronium annihilation lifetime spectroscopic study

Photoresist and Residue Removal Using Gas-Expanded Liquids

Ionic Conductivity of Elevated Pressure TMAHCO[sub 3]/MeOH/CO[sub 2] Mixtures

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Phase Behavior and Modeling of CO2/Methanol/Tetramethylammonium Bicarbonate and CO2/Methanol/Tetramethylammonium Bicarbonate/Water Mixtures at High Pressures

Cited by 16 publications

References 42 publications

Compatibility of high pressure cleaning mixtures with a porous low dielectric constant film: A positronium annihilation lifetime spectroscopic study

Compatibility of high pressure cleaning mixtures with a porous low dielectric constant film: A positronium annihilation lifetime spectroscopic study

Photoresist and Residue Removal Using Gas-Expanded Liquids

Ionic Conductivity of Elevated Pressure TMAHCO[sub 3]/MeOH/CO[sub 2] Mixtures

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Phase Behavior and Modeling of CO₂/Methanol/Tetramethylammonium Bicarbonate and CO₂/Methanol/Tetramethylammonium Bicarbonate/Water Mixtures at High Pressures