Supercritical CO 2 Treatments for Semiconductor Applications
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Supercritical CO2 Treatments for Semiconductor Applications S. Gangopadhyaya, J.A. Lubgubana, B. Lahlouhb, G. Sivaramanb, K. Biswasa, T. Rajagopalanb, N. Biswasb, H. -C. Kimc, W. Volksenc and R. D. Millerc a
Dept. of Electrical and Computer Engg., University of Missouri, Columbia, MO, 65211 Nano-Tech Center, Texas Tech University, Lubbock, TX 79409 c IBM Almaden Research Center, San Jose, CA 95120 b
Supercritical fluids (SF) have been used in a wide variety of applications: in industrial processes, analytical, waste detoxification, etc. Recently, its usefulness extends to the semiconductor industry. Researches have shown that supercritical CO2 (SCCO2) can be used to remove photoresists and significantly reduce the amount of waste from solvents in comparison to conventional stripping techniques. SF will also find its usefulness in cleaning high aspect ratio vias and deep trenches as semiconductor features shrink to submicron levels. We will report here the use of supercritical CO2 treatments in extraction of porogens from a nanohybrid film fabricated via templated-porogen approach. Its use as a medium to repair the damage in porous films from plasma ashing will also be presented. The ability to tune the solvation and diffusion power of SCCO2 and to swell the film matrix make it a good medium for silylation to restore hydrophobicity and functionalize the film. Introduction The further development of ultra-large-scale-integration microelectronics devices will depend on the introduction of new materials and the development of new processing techniques and procedures. The reasons are: using current materials to fabricate devices will ultimately offset the speed and performance and using current processing techniques will create reliability problems that come with scaling to dimensions below 100 nm. New materials for low-k and high-k gate dielectrics, new method of cleaning residues and new deposition techniques in high aspect ratio vias and deep trenches are just few examples. Among the new processes for microelectronics processing is the emerging supercritical CO2, SCCO2.1~3 This technique has been used extensively for various applications like industrial, pharmaceutical, analytical and waste detoxification.4,5 The recent interest in SCCO2 process lies on its versatile characteristics which includes gas-like diffusivity, liquid-like dissolving power and dynamic properties.4,5 In high aspect ratio vias and deep trenches, these properties of SCCO2 can be exploited in a variety of ways: as a solvent carrier to clean residues, as a medium for chemical reaction, as a deposition medium, and as solvent for removal of certain species. The efficient and minimal use of co-solvents in SCCO2 is a strong motivator to use this process. The use of SCCO2 with a co-solvent in the removal of photoresists has been reported and resulted in minimal waste products.1 This means the availability of an environmentally friendly and cost-cutting process which make it attractive. Another group has reported the use of SCCO2 as toughening
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