Optical lithography Robin Nagel TUM 12. Januar 2009 Robin Nagel (TUM) Optical lithography 12. Januar 2009 1 / 22
1 What is optical lithography? 1 The optical system 1 Production process 1 Future and limits of optical lithography 1 References Robin Nagel (TUM) Optical lithography 12. Januar 2009 2 / 22
What is optical lithography? Lithography (from the Greek - lithos: stone + grapho: to write ) optical lithography is a process used to selectively remove parts of a thin film. Until now, it is the only way for industrial mass production of computer chips Robin Nagel (TUM) Optical lithography 12. Januar 2009 3 / 22
The optical system Robin Nagel (TUM) Optical lithography 12. Januar 2009 4 / 22
Mask making process Exposure Develop Etch Robin Nagel (TUM) Optical lithography 12. Januar 2009 5 / 22
What is optical lithography? The optical system Production process Future and limits of optical lithography References Photoresist The photoresist (DiazoNaphtoQuinon-(DNQ)Sulfonat) reacts under the influence of the light to an Inden-carboxylic acid The carboxylic acid has in orders of magnitude a higher solubility The bonding of the SO2 R group defines the absorbed wavelength Robin Nagel (TUM) Optical lithography 12. Januar 2009 6 / 22
What is optical lithography? The optical system Production process Future and limits of optical lithography References Defects Particles in the photoresist (dust,old photoresist) Bubbles Rough substrate Tear-off Robin Nagel (TUM) Optical lithography 12. Januar 2009 7 / 22
Kinds of photoresist Robin Nagel (TUM) Optical lithography 12. Januar 2009 8 / 22
Oxidation and exposure Lightsources can be: Mercury lamps with a wavelength of 365nm state-of-the-art light sources are Argon Fluoride (ArF) Excimer lasers with a wavelength of 193nm Robin Nagel (TUM) Optical lithography 12. Januar 2009 9 / 22
Etch process Robin Nagel (TUM) Optical lithography 12. Januar 2009 10 / 22
Diffusion and implant Robin Nagel (TUM) Optical lithography 12. Januar 2009 11 / 22
Deposition Robin Nagel (TUM) Optical lithography 12. Januar 2009 12 / 22
Oxidation Robin Nagel (TUM) Optical lithography 12. Januar 2009 13 / 22
Interconnects Robin Nagel (TUM) Optical lithography 12. Januar 2009 14 / 22
Metallization Robin Nagel (TUM) Optical lithography 12. Januar 2009 15 / 22
Chemical mechanical planarization Robin Nagel (TUM) Optical lithography 12. Januar 2009 16 / 22
Interconnects and layers Robin Nagel (TUM) Optical lithography 12. Januar 2009 17 / 22
Future and limits of optical lithography Rayleigh equation: W = k λ - k= resolution factor - λ= wavelengh NA - NA= Numerical aperture For example: λ=193nm, NA=0.93 and k=0.25 0.25 193nm W = = 52nm 0.93 Use of Extrem UV lights (13nm) or X-Ray (0.5nm) Use of new materials and techniques (such as immersion lithography) Robin Nagel (TUM) Optical lithography 12. Januar 2009 18 / 22
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References 1 lecture nanoelectronics by Prof. Lugli at the Tum 2 Intel, The High-k Solution, 2007 3 Paolo A. Gargini, Silicon nanoelectronics and beyond,2004 4 Gordon E. Moore, Cramming more components onto integrated circuits, 1965 5 Reed Business Information, 32 nm Marked by Litho, 2008 6 Daniel Bratton, Da Yang, Junyan Dai and Christopher K. Ober, Recent progress in high resolution lithography,2006 7 Yong Chen, Anne Pepin, Nanofabrication:Conventional and nonconventional methods,2001 8 icknowledge, Technology backgrounder: Immersion Lithography, 2003 9 Microchemicals, Lithografie, 2007 Robin Nagel (TUM) Optical lithography 12. Januar 2009 22 / 22