Multiple e-beam direct write lithography (MEBDW), using >10,000 e-beams writing in parallel, proposed by
MAPPER, KLA-Tencor, and IMS is a potential solution for 20-nm half-pitch and beyond. The raster scan in MEBDW
makes bitmap its data format. Data handling becomes indispensable since bitmap needs a huge data volume due to the
fine pixel size to keep the CD accuracy after e-beam proximity correction (EPC). In fact, in 10,000-beam MEBDW, for a
10 WPH tool of 1-nm pixel size and 1-bit gray level, the aggregated data transmission rate would be up to 1963 Tera bits
per second (bps), requiring 19,630 fibers transmitting 10 Gbps in each fiber. The data rate per beam would be <20 Gbps.
Hence data reduction using bigger pixel size, fewer grey levels to achieve sub-nm EPC accuracy, and data truncation
have been extensively studied.
In this paper, process window assessment through Exposure-Defocus (E-D) Forest to quantitatively characterize the
data truncation before and after EPC is reported. REBL electron optics, electron scattering in resist, and resist acid
diffusion are considered, to construct the E-D Forest and to analyze the imaging performance of the most representative layers and patterns, such as critical line/space and hole layers with minimum pitch, cutting layers, and implant layers, for the 10-nm, and 7-nm nodes.
The authors present a study focused on the feasibility of using holographic polymer dispersed liquid crystal wavelength filters for hyperspectral imaging (HSI). For this study, stacks of these filters were fabricated in the visible wavelength range of 600 to 800 nm. These filters were demonstrated to have a number of properties useful for HSI applications, including uniform reflection efficiency of 80% across a 35 mm optical aperture, polarization insensitivity for normal incidence, spectral resolution of 10 nm, and fast switching times on the order of microseconds. In addition, the ability to modulate each filter in the stack at a different frequency allows for spectral multiplexing, thus enabling synchronous detection and demodulation of the image data. Although the filters in their current state show promise for HSI applications, techniques to further improve performance in terms of viewing angle range and transmission throughput are presented. Finally, a system level integration of such a stack into the prototype drive and detection unit is discussed.
REBL (Reflective Electron Beam Lithography) is a novel concept for high speed maskless projection electron beam
lithography. Originally targeting 45 nm HP (half pitch) under a DARPA funded contract, we are now working on
optimizing the optics and architecture for the commercial silicon integrated circuit fabrication market at the equivalent of
16 nm HP. The shift to smaller features requires innovation in most major subsystems of the tool, including optics, stage,
and metrology. We also require better simulation and understanding of the exposure process.
In order to meet blur requirements for 16 nm lithography, we are both shrinking the pixel size and reducing the beam
current. Throughput will be maintained by increasing the number of columns as well as other design optimizations. In
consequence, the maximum stage speed required to meet wafer throughput targets at 16 nm will be much less than
originally planned for at 45 nm. As a result, we are changing the stage architecture from a rotary design to a linear
design that can still meet the throughput requirements but with more conventional technology that entails less technical
risk. The linear concept also allows for simplifications in the datapath, primarily from being able to reuse pattern data
across dies and columns. Finally, we are now able to demonstrate working dynamic pattern generator (DPG) chips,
CMOS chips with microfabricated lenslets on top to prevent crosstalk between pixels.
This work focuses on the study of the modification in formation and electro-optic behavior of holographically formed
polymer -liquid crystal thin film gratings doped with multiwalled carbon nanotubes. Results indicate a time delay in the
evolution of the first diffraction order in the presence of carbon nanotubes when compared to ones with no nanotubes.
An analysis is presented based on the modification of the diffusion kinetics in terms of photo induced phase separation.
This slow down is attributed to the non-participation of the carbon nanotubes in the phase separation process, and acting
as physical barriers to the counter diffusing liquid crystals. The diffusion constant of nanotubes, incorporating its shape
anisotropy, is computed in such a photo polymerizable system and compared with those of the participating polymers
and liquid crystals. An optimal concentration of carbon nanotube doping is arrived at which helps in improve the
switching speed while maintaining diffraction efficiency. Improvement is switching speed is attributed to reduction in
size of the liquid crystal droplets. Scanning electron microscopy results indicate a change in morphology of the gratings
doped with carbon nanotubes. In specific, smaller droplet size and, beyond the optimal level of nanotube doping,
imperfect liquid crystal phase separation with scarcity of liquid crystal droplets across the sample is seen.
In this work we demonstrate the feasibility of using a holographically formed thin film electro-optic stack for
the development of an airborne hyperspectral imaging system in the visible wavelength range of 600nm to 800nm. Each
wavelength filtering element in the stack is formed by photo-induced phase separation of a homogenous mixture of
liquid crystals and photopolymers, exhibiting a uniform reflection efficiency of up to 80% across a 35mm optical
aperture with non-normalized baseline transmission, polarization insensitivity for normal incidence and a spectral
resolution of 10nm. Fast switching time on the order of microseconds and techniques to improve view angle in the
individual wavelength filtering elements in the stack are discussed and the improvements are discussed from a
morphological standpoint. Two techniques for stacking the thin films have been developed which requires lesser number
of substrates hence improving transmission throughput and radiometric efficiency through the stack. An advantage of
using such a stack is the ability to modulate each wavelength filtering element at a different frequency to obtain a
spectral multiplex, thereby enabling synchronous detection and demodulation of each wavelength with a high update rate
for the hyperspectral cube. A system level integration of such a stack into the prototype drive and detection unit is
discussed in this work.
In this work we demonstrate an improved electro-optic response and quantify the effect on transmitted wavefront
properties of thiolene based reflection mode holographic polymer dispersed liquid crystals (HPDLC) gratings doped
with oxidized multi-walled carbon nanotubes (MWNT). Effect of various doping levels on the reflection efficiencies is
evaluated and optical spectrometry results indicate a reduction in the reflection efficiency and an anomalous electrooptic
behavior at higher doping levels of MWNT especially in gratings with longer pitch where the diffusion length for
liquid crystal (LC) is long. Wavefront analysis based on Shack-Hartmann wavefront sensor show an increase in the
transmitted RMS wavefront error in a 633nm wavefront after a critical level of MWNT doping. Polarized optical
microscopy results indicate that the MWNT do not participate in the photo polymerization induced phase separation
hence acting as physical barriers for the counter diffusing LC at high MWNT concentrations. Reduction in overall size
of the LC droplets in the LC rich planes, observed using scanning electron microscopy imaging, leads to faster rise and
fall times hence quicker relaxation time. Observation of reduced switching voltage is attributed to the modification of
dielectric properties of the medium manifested by an increase in capacitance and decrease in resistivity in presence of
MWNT.
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