Imprint lithography has been shown to be an effective technique for replication of nano-scale features. Jet and
Flash Imprint Lithography (J-FIL) involves the field-by-field deposition and exposure of a low viscosity resist
deposited by jetting technology onto the substrate. The patterned mask is lowered into the fluid which then quickly
flows into the relief patterns in the mask by capillary action. Following this filling step, the resist is crosslinked under
UV radiation, and then the mask is removed leaving a patterned resist on the substrate.
Acceptance of imprint lithography for manufacturing will require demonstration that it can attain defect levels
commensurate with the defect specifications of high end memory devices. Typical defectivity targets are on the order of
0.10/cm2. In previous studies, we have focused on defects such as random non-fill defects occurring during the resist
filling process and repeater defects caused by interactions with particles on the substrate.
In this work, we attempted to identify the critical imprint defect types using a mask with NAND Flash-like patterns
at dimensions as small as 26nm. The two key defect types identified were line break defects induced by small
particulates and airborne contaminants which result in local adhesion failure. After identification, the root cause of the
defect was determined, and corrective measures were taken to either eliminate or reduce the defect source. As a result,
we have been able to reduce defectivity levels by more than three orders of magnitude in only 12 months and are now
achieving defectivity adders as small as 2 adders per lot of wafers.
193 immersion lithography has reached its maximal achievable resolution. There are mainly two lithographic
strategies that will enable continued increase in resolution. Those are being pursued in parallel. The first is extreme
ultraviolet (EUV) lithography and the second is double patterning (exposure) lithography. EUV lithography is counted
on to be available in 2013 time frame for 22 nm node. Unfortunately, this technology has suffered several delays due to
fundamental problems with source power, mask infrastructure, metrology and overall reliability. The implementation
of EUV lithography in the next five years is unlikely due to economic factors. Double patterning lithography (DPL) is a
technology that has been implemented by the industry and has already shown the proof of concept for the 22nm node.
This technique while expensive is the only current path forward for scaling with no fundamental showstoppers for the
32nm and 22nm nodes. Double exposure lithography (DEL) is being proposed as a cost mitigating approach to advanced
lithography. Compared to DPL, DEL offers advantages in overlay and process time, thus reducing the cost-of-ownership
(CoO). However, DEL requires new materials that have a non-linear photoresponse. So far, several approaches were
proposed for double exposure lithography, from which Optical Threshold Layer (OTL) was found to give the best
lithography performance according to the results of the simulation. This paper details the principle of the OTL
approach. A photochromic polymer was designed and synthesized. The feasibility of the material for application of DEL
was explored by a series of evaluations.
A pattern-recognition and encoding system has been developed for a biochip platform using shaped hydrogel sensors batch produced via photolithography. Each sensor shape is fashioned with a unique pattern of dots that makes it identifiable to a pattern recognition system. By linking the sensor's function to its shape, "random" arrays can be created (i.e., arrays that do not require sensors to be located at specific positions). Random arraying can be quickly and cost-effectively achieved via self-assembly methods. Pattern-recognition software was written to perform automated recognition of micrographs exhibiting fluorescing sensors. As a test of the recognition process, an array of shape-encoded DNA sensors was fabricated using lithography. Fluorescent micrographs were taken of a DNA-sensing experiment, and then processed with the pattern-recognition software. The results show that this process is quite viable with 98% recognition accuracy of the nondefective sensors in both images.
The current optical photolithography technology is approaching the physical barrier to the minimum achievable feature size. To produce smaller devices, new resolution enhancement technologies must be developed. Double-exposure lithography has shown promise as a potential pathway that is attractive because it is much cheaper than double-patterning lithography and can be deployed on existing imaging tools. However, this technology is not possible without the development of new materials with nonlinear response to exposure dose. The performance of existing materials such as reversible contrast enhancement layers (rCELs), and theoretical materials such as intermediate state two-photon (ISTP) and optical threshold layer (OTL) materials in double-exposure applications have been investigated through computer simulation. All three materials yielded process windows in double-exposure mode. OTL materials showed the largest process window (depth of focus (DOF) 0.14 µm, exposure latitude (EL) 5.1%). ISTP materials had the next-largest process window (DOF 0.12 µm, EL 3.2%), followed by the rCEL (0.11 µm, 0.58%). This study is an analysis of the feasibility of using the materials in double-exposure mode.
The current optical photolithography technology is approaching the physical barrier to the minimum achievable
feature size. To produce smaller devices, new resolution enhancement technologies must be developed. Double
exposure lithography has shown promise as potential pathway that is attractive because it is much cheaper than
double patterning lithography and it can be deployed on existing imaging tools. However, this technology is not
possible without the development of new materials with nonlinear response to exposure dose. The performance
of existing materials such as reversible contrast enhancement layers (rCELs) and theoretical materials such as intermediate
state two-photon (ISTP) and optical threshold layer (OTL) materials in double exposure applications
was investigated through computer simulation. All three materials yielded process windows in double exposure
mode. OTL materials showed the largest process window (DOF 0.137 μm, EL 5.06 %). ISTP materials had the
next largest process window (DOF 0.124 μm, EL 3.22 %) followed by the rCEL (0.105 μm, 0.58 %). This study
is an analysis of the feasibility of using the materials in double exposure mode.
Acid diffusion during the post-exposure bake of chemically amplified resists (CARs) is a major contributing factor to
line width roughness (LWR) and resolution limits at the 32 nm node and beyond. To overcome these limitations,
non-CAR materials are becoming more attractive because acid diffusion is eliminated. We have therefore focused our
effort on the synthesis of copolymers that have both a diacyldiazo side chain unit as well as a hexafluoroalcohol unit.
This copolymer shows better contrast than that of copolymers containing lactone units due to their inhibition behavior.
Furthermore, polymer blends containing hexafluoroalcohol groups show good 100 nm line and space patterning property
for 193 nm lithography. This paper describes the design, synthesis, and characterization of these non-CARs, and thier
improvement to photolithography.