DocumentCode :
1154043
Title :
Condensation of silanol groups in porous methylsilsesquioxane films using Supercritical CO2 and alcohol cosolvents
Author :
Xie, Bo ; Muscat, Anthony J.
Author_Institution :
Dept. of Chem. & Environ. Eng., Univ. of Arizona, Tucson, AZ, USA
Volume :
17
Issue :
4
fYear :
2004
Firstpage :
544
Lastpage :
553
Abstract :
Fourier transform infrared (FTIR) spectroscopy, goniometry, and electrical measurements were used to investigate the effect of adding alcohol and carboxylic acid cosolvents to supercritical carbon dioxide (scCO2) to condense silanol groups in blanket porous methylsilsesquioxane (p-MSQ) films (JSR LKD 5109). The aliphatic C1-C6 alcohols removed approximately 50% more hydrogen-bonded silanol (SiO-H) groups than pure scCO2, leaving isolated silanol groups on the surfaces of the pores. Acetic acid removed H-bonded silanols but left fewer isolated moieties. On a molar basis, n-propanol, isopropanol, and n-butanol removed the largest percentage of silanols per molecule of cosolvent. These cosolvents were also among the lowest vapor pressure cosolvents studied, making them the most environmentally acceptable. As-received ashed ultralow-k MSQ had a contact angle of less than 10° and a dielectric constant of 3.5±0.1. After processing in a mixture containing 7% n-propanol and scCO2, the contact angle was 15° and the dielectric constant decreased to 3.2 ± 0.1. The surface was hydrophilic after processing in mixtures of cosolvents and scCO2 because of the isolated silanol groups on the surface. A comparison of the trends across the alcohol series indicates that cosolvent addition to scCO2 increased the solubility of water in the supercritical fluid mixture compared to pure scCO2. Within the same class of molecules, the solubility of the cosolvent in the supercritical fluid is a more important selection criterion than the solubility of water in the cosolvent.
Keywords :
Fourier transform spectra; carbon compounds; contact angle; dielectric thin films; film condensation; hydrogen bonds; infrared spectra; organic compounds; permittivity; porous materials; solubility; CO2; FTIR spectra; Fourier transform infrared spectroscopy; JSR LKD 5109; SiO-H groups; acetic acid removed H-bonded silanols; alcohol addition; alcohol cosolvents; aliphatic C1-C6 alcohols; blanket porous methylsilsesquioxane films; carboxylic acid cosolvent addition; condensation; contact angle; dielectric constant; electrical measurement; goniometry; hydrogen-bonded silanol groups; isopropanol; n-butanol; n-propanol; porous MSQ; porous methylsilsesquioxane film; silanol groups; solubility; supercritical CO2; supercritical fluid; ultralow-k; vapor pressure cosolvents; Chemicals; Cleaning; Copper; Dielectric constant; Dielectric materials; Etching; Infrared spectra; Plasma applications; Resists; Spectroscopy; 65; Alcohol; FTIR; Fourier transform infrared; condensation; contact angle; cosolvent; porous methylsilsesquioxane; silanol; spectroscopy; supercritical CO; ultralow-; water;
fLanguage :
English
Journal_Title :
Semiconductor Manufacturing, IEEE Transactions on
Publisher :
ieee
ISSN :
0894-6507
Type :
jour
DOI :
10.1109/TSM.2004.837003
Filename :
1353309
Link To Document :
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