4 May 2005 Overcoming pattern collapse of ultra high resolution dense lines obtained with EUV resists
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Abstract
Future lithography tools will have to address the 32 nm node. EUV lithography at 13.4 nm wavelength is the technology that may achieve such resolution if chemically amplified EUV resists show high enough resolution capabilities. However for sub 100 nm line width patterns, the pattern collapse, generated during the drying step of the developing process, becomes a serious limiting phenomenon. We performed ultra high resolution exposures of EUV positive chemically amplified resists using either electron beam lithography (EBL), or EUV interferometry Lithography (IL) produced in a synchrotron. Two theoretical models have been compared with experimental results. One is mainly dealing with adhesion failure and the other with the line deformation. Adhesion failure occurs when capillarity pressure on the pattern become stronger than the attractive Van der Walls forces assuring the pattern adhesion on the substrate. Mechanical failure occurs once the lines deflection exceeds the mechanical breaking resistance of the resist. We highlighted that pattern collapse mode depends on resist thickness. Collapsing of patterns with thickness>100 nm are properly fitted with the deformation model of the resist; whereas for pattern height under 60 nm, experimental results obtained by EUVIL and EBL are properly predicted with the adhesion failure model. To push resolution further and avoid pattern collapse, we targeted to expose sub 100 nm thick resist films. AFM3D measurements on EBL patterns show that reducing the resist thickness increases their top Line Width Roughness (LWR) testifying of physical resist properties variations in the resist interfacial layers. However we pointed out an optimum resist thickness, hence an optimal dilution. By tuning developer normality and puddle time, straight resist profiles were obtained. Finally we reached dense 40/40 nm lines in XP9947W150 resist using both exposure tools and validate the process compatibility with future etching steps by transferring 40/40 nm dense lines patterned with EBL into a metallic hard mask.
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A. Jouve, J. Simon, J. Foucher, T. David, J.-H. Tortai, Harun Solak, "Overcoming pattern collapse of ultra high resolution dense lines obtained with EUV resists", Proc. SPIE 5753, Advances in Resist Technology and Processing XXII, (4 May 2005); doi: 10.1117/12.598763; https://doi.org/10.1117/12.598763
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