Transcript Presentations\Nanometer Scale Lithography Bourget and Geex

Nanometer Scale
Lithography
Also Known as Nanolithography. It is the making of
semiconductor devices on an atomic scale level to no more
than 100 nm by transferring patterns to one medium to
another. There are multiple techniques which include
photolithography, x-ray nanolithography, electron beam
direct-write lithography, extreme ultraviolet lithography,
and ion beam lithography.
Vicki Bourget & Vinson Gee
April 23, 2014
Outline
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Basic Components
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Photolithography
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X-ray nanolithography
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Electron Beam Direct-Write Lithography
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Extreme Ultraviolet Lithography
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Charged Particle Lithography
Optical Lithography Basic Components
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Source
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Condenser
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Mask
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Collects the source radiation and directs it onto the
mask
Contains the pattern to be printed on the wafer
Reduction imaging lens
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Projects an image of the mask onto the silicon wafer
Photolithography
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Uses light to transfer a
pattern from photomask to
a photoresist chemical on
the substrate
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Chemical treatments
engraves the exposure
pattern into the material
under the photoresist
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Most cost effective
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Requires a flat substrate
Image From: Lin
X-Ray Nanolithography
Selectively remove
parts of a thin film
• Uses x-rays to transfer
pattern from mask to
photoresist on the
substrate
• Requires special mask
sensitive to x-rays
• Used for batch
processing
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Image From: Antony
Electron Beam Direct Write Lithography
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Electron beam Lithography has the ability to
fabricate patterns that have nanometer feature
sizes
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Short wavelength and reasonable energy densities
Direct writing is the most common approach for
electron beam lithography
• Most often used in mask making, prototyping,
fabrication of special small volume products,
and research and development for advanced
applications
• Not often used in mass production due to a
speed limitation
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Electron Beam Direct Write Lithography
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Direct writing consists of a
source of electrons, a
focusing optics set, a
blanker to turn the beam
on and off, a deflection
system for moving the
beam and a stage for
holding the substrate
(Image from Ampere)
Electron Beam Direct Write Lithography
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It is the most desirable process because it is capable of
superior resolution and requires no expansive
projection optics or time consuming mask production
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Two types of beams used
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Gaussian round beam that moves with the wafer to
expose the wafer one pixel at a time
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Can be classified as vector scans
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Variable shaped beam uses parallel electron beams
to write a primitive shape in one shot
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More speed is gained but the resolution is sacrificed
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Speed vs detail
Extreme Ultra Violet Lithography
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Uses a laser-produced plasma source of radiation, a
reflective mask and a 4x all reflective imaging system
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Ideal for creating a high volume of integrated circuits
using wavelengths below 100 nm
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EUVL manufacturing must be done in a vacuum using
reflective mirrors and masks since all materials strongly
absorb ultraviolet light
Extreme Ultra Violet Lithography
This image shows a simple EUVL process where the
radiation from the laser-produced plasma illuminates a
mask onto the silicon wafer substrate where the IC’s are
built
(Image from Stulen)
Ion Beam Lithography
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Similar to electron beam lithography, but the key
difference is that ion lithography uses heavier, charged
ions
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Heavier ion particles have more momentum and offers
high resolution patterning than UV, x-ray, or electron
beam lithography
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Uses include nanometer pattern fabrication and direct
doping of the substrate
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Boron and Phosphorus ions are commonly used
Ion Beam Lithography
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There are several methods of ion beam
lithography
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Focused ion beam lithography (FIB)
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Masked ion beam lithography (MIB)
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Ion beam projection lithography (IBP)
Summary
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Nanolithography is the making of semiconductor devices
on an atomic level to no more that 100 nm
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Used to create small integrated circuits and printed
circuit boards
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They are still improving the techniques
References
Ampere A. Tseng, Kuan Chen, Chii D. Chen, Kung J. Ma, “Electron
Beam Lithography in Nanoscale Fabrication: Recent
Development,” IEEE Transactions on Electronics Packaging
Manufacturing, Vol. 26, No. 2, April 2003, p. 141-149, PDF
Antony Bourdillon and Yuli Vladimirsky, “X-ray Lithography on the
Sweet Spot”, UHRL, San Jose, (2006)
Lin, B. J., "Optical Lithography", SPIE Press, Bellingham, WA,
2009, p. 136.
Okazaki, Shinji, “Comparison of Optical, X-ray, Electron and Ion
Beam Lithography,” Microelectronic Engineering 9 (1989), p.
297-304, North-Holland, PDF.
Stulen, Richard H. and Donald W. Sweeney, “Extreme Ultraviolet
Lithography,” IEEE Journal of Quantum Electronics, Vol. 35, No.
5, May 1999, p. 694 – 699, PDF
Key Concepts
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Basic components for lithography are source, condenser,
mask, and reduction imaging lens.
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Photolithography is the most cost effective technique.
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Most common application is integrated circuits.
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Electron beam uses either round beam or variable shaped
beam.
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EUV is ideal for creating a high volume of integrated
circuits using wavelengths below 100 nm.