Joseph Q. Pham

The glass transition of thin film polymer/polymer blends: Interfacial interactions and confinement

We examined the influence of film thickness and composition on the effective Tg of compatible thin film mixtures of polystyrene (PS) and tetramethylbisphenol-A polycarbonate (TMPC) on SiOx/Si substrates using spectroscopic ellipsometry. Our measurements reveal that while the Tg of TMPC films increased with decreasing film thickness, h, the effective Tg of thin film mixtures of PS and TMPC decreased with decreasing film thickness. In these mixtures, Tg was independent of film thickness at large h. We also found that while the Tg of bulk mixtures of TMPC/PS exhibited large negative deviations from additivity with composition, such deviations were negligible in the thin film mixtures. The thickness dependence of Tg is compared with theory.

Chemical-mechanical photoresist drying in supercritical carbon dioxide with hydrocarbon surfactants

Supercritical CO2 containing hydrocarbon surfactants was utilized to remove water from photoresists without pattern collapse due to capillary forces. The addition of highly branched hydrocarbon surfactants to CO2 reduces the amount of solvent required for drying, and lowers the interfacial tension from 20 mN/m to approximately 1 mN/m, thus reducing pattern collapse. The drying time and amount of solvent were further reduced in a chemical/mechanical method, in which solvent, drained by gravity forces, is removed by hydrodynamic forces resulting from flowing CO2. In situ ellipsometry measurements show that the resist films swollen with CO2 return to their original thickness upon depressurization, indicating CO2 is compatible with these resists.

Water-in-carbon dioxide microemulsions for removing post-etch residues from patterned porous low-k dielectrics

A hierarchy of CO2-based solvents is used to remove post-etch residues from vias and trenches in low-k patterned porous methylsilsesquioxane (pMSQ) interlayer dielectrics. Spectroscopic ellipsometry measurements indicate that, upon pressurization and depressurization with CO2, the thickness and refractive index return to values near the original values indicating that collapse or voiding of the pores did not occur. Post-etch residue could not be removed by pure water, CO2, with or without cosolvent, or dry CO2 with a surfactant. These results suggest that the particles could not be removed by a dissolution mechanism alone. The via and the bottom trench were cleaned with a solvent containing water, CO2, and a hydrocarbon surfactant. In this mild detergent system, particles may be removed both as a suspension and in the dissolved state in microemulsions and macroemulsions. The low interfacial tension prevents collapse of the pMSQ during water removal. This mild detergent system does not produce voids in the...