Biomedical Engineering Reference
In-Depth Information
Fig. 1.18
The nanoimprint
process
stamping
resist
substrate
stamped resist
etching
ion beam. The throughput, which represents the number of patterned features in
one second, is quite low, of 10-10 2 features/s for the direct writing EB and FIB
techniques, but increases dramatically, up to 10 10 features/s, for the EB projection
method.
The nanoimprint lithography is a high-resolution nanolithography, displaying
high reproducibility in a short time. Its throughput is as large as 10 12 features/s,
while the resolution is as small as 10 nm. Typically, the nanoimprint technique
utilizes a master or stamp fabricated from SiO 2 or Si, which contains the desired
pattern fabricated via EB or FIB. This stamp is then used to imprint a resist with the
desired pattern. The resist is generally a polymer, which can be UV-curable or ther-
moplastic (heated above its glass temperature), such as PMMA. After the polymer
is stamped, the resist residues are removed by etching. The nanoimprint lithography,
schematically displayed in Fig. 1.18 , is excellently reviewed in Guo ( 2004 ).
The extreme top-down nanolithography technique is based on atomic beams,
collimated and focused, similar to optical systems, by atomic lenses, atomic
apertures, etc. In general, the atom beam interacts with laser beams and the resulted
optical-atomic forces are utilized for (1) depositing atoms in order to built nanoscale
structures or (2) patterning various shapes in a lithographic method ( Meschede and
Metcalf 2003 ). The atomic lithographic technique is based on an incoming atomic
beam that is incident on a standing wave created by a laser and a mirror system, as
showninFig. 1.19 . The standing wave plays the role of a light mask for the incident
atoms and is analogue to an array of lenses diffracting the atoms in the optical
antinodes or nodes as a function of the sign of the difference between the laser
frequency and the resonant frequency of atoms. In consequence, the desired pattern
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