Enhanced processing of performance films using high-diffusivity penetrants

#This invention relates to methods of enhancing the performance of films formed on substrates such as microelectronic devices.

#Liquid and supercritical carbon dioxide has been disclosed and in some cases commercially used as a diluent, carrier, or media for a variety of chemical and industrial processes ranging from fine chemical extraction and isolation to cleaning of precision parts (See, e.g., U.S. Pat. No. 5,944,966 to DeSimone et al. (cleaning); U.S. Pat. No. 6,240,936 to DeSimone et al. (spin cleaning); U.S. Pat. No. 5,858,022 to Romack et al. (dry cleaning); U.S. Pat. No. 6,120,613 to Romack et al. cleaning/separation systems)). The physical properties and the tunable nature of both liquid and supercritical CO2, along with its generally benign nature, make it an ideal candidate for replacement of many industrial solvents and water.

#Liquid and supercritical CO2 has been disclosed as a media for coating a variety of CO2-philic materials onto various substrates (see, e.g., U.S. Pat. No. 6,001,418 to DeSimone et al. (spin coating); U.S. Pat. No. 6,200,637 to McClain et al. (coating); U.S. Pat. No. 6,010,542 to DeYoung et al. (dyeing)). Again, the physical properties of the fluid encompassed in its tunable nature and superior wetting properties benefit a variety of applications in replacement of solvents and water.

#A 1-micron thick film of a t-butyl capped polyhydroxystyrene polymer Mn-10,500 was spin coated onto a 5-inch wafer from a 10-wt. percent solution in THF/Toluene (2:1). After a 10-minute equilibration period in dry air at 70° C., the wafer was evaluated spectroscopically to benchmark residual solvent hold-up in the film. The wafer was then added to a pressure chamber that was filled with CO2 at 1800 psi and 40° C. The chamber was maintained at 40° C. for 3 minutes while additional clean CO2 was added to the chamber and CO2 was removed from the chamber maintaining constant pressure and temperature. Over the 2-minute period, 4 fluid turnovers was achieved. The chamber was then vented to atmospheric pressure and the wafer was removed and analyzed spectroscopically. The film was determined to be essentially free of residual solvent. A second wafer, spun under identical conditions, was allowed to equilibrate in dry air at 70° C. for 10 minutes before the film was evaluated spectroscopically to benchmark solvent hold-up. The wafer was then placed on a heating plate set to 100° C. for 3-minutes. After cooling, the wafer was analyzed for residual solvent content. The film showed considerable but incomplete solvent removal. The wafer was exposed to atmospheric conditions for an additional 3-hours after which it was again evaluated spectroscopically. Solvent residue was still noted in the film.

#Two identically patterned 5″ quartz wafers with non-uniform surface topography were coated with a commercially available photoresist to yield films approximately 1 micron thick. Both were allowed to equilibrate for 5 hours in dry air at 70° C. The surface topography of the films was then evaluated using a profilometer. Surface non-uniformity was seen in both wafers. One wafer was placed in a pressure vessel to which CO2 was added to 1800 psi and 50° C. The vessel was maintained at 40° C. for 3 minutes and the chamber was vented and the wafer removed. The second wafer was placed on a heating plate at 100° C. for 3 minutes then cooled. The surface of both wafers was profiled. In both cases the non-uniformity of the film was substantially reduced.

#Two small quartz wafers were coated with a t-butyl capped polyhydroxystyrene polymer and a prototpye photoacid generator, 0.4% PAG by weight of polymer in solution. After a 70° C. PAB for 5 minutes followed by a 10-minute equilibration at 70° C., both wafers were evaluated spectroscopically to benchmark the hydroxyl content in the blanket film. Both wafers were then exposed to a light source of the desired wavelength and intensity for the same length of time. One wafer was then placed in a pressure vessel that was pressurized to 2500 psi at 50° C. for 4 minutes while CO2 was circulated through the chamber at the constant pressure and temperature. The chamber was then vented and the wafer removed. Simultaneous with the treatment of the first wafer with CO2, the second wafer was heated to 50° C. for 4 minutes and then cooled to room temperature. Both wafers were then equilibrated in dry air for 10 minutes and then analyzed spectroscopically to determine the relative degree of hydroxyl content. While both films showed increased hydroxyl content in the film relative to the benchmark established after PAB, the film processed in the CO2 fluid showed a substantially higher degree of hydroxyl content.