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 mu m, exposure latitude (EL) 5.1%). ISTP materials had the next-largest process window (DOF 0.12 mu m, EL 3.2%), followed by the rCEL (0.11 mu m, 0.58%). This study is an analysis of the feasibility of using the materials in double- exposure mode. (C) 2009 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3095589]

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. (C) 2009 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3099722]

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.

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.

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 mu m, EL 5.06 %). ISTP materials had the next largest process window (DOF 0.124 mu m, EL 3.22 %) followed by the rCEL (0.105 mu m, 0.58 %). This study is an analysis of the feasibility of using the materials in double exposure mode.

A 2-methoxynaphthalene dimer system is demonstrated as a sequential two photon photoacid generator for double exposure (DE) lithography. DE is based on the use of staggered exposures and is proposed as a replacement for conventional optical lithography. The linear behavior of conventional resist materials disqualifies their use in DE photolithography. The design of reversible nonlinear responsive materials is therefore required.

Double patterning and double exposure techniques have been proposed as possible methods for reducing half pitch resolution below k(1)=0.25. Both methods have the potential to reduce the theoretical lithographic half pitch to k(1)=0.125. Double patterning is a process-intensive method that requires multiple coat, develop, and etch steps to achieve the low k(1) imaging. Double exposure processes have been proposed that do not require multiple coat, develop, or etch steps. Potentially, double exposure processes will have a lower cost of ownership that double patterning. However, double exposure materials have not yet been proven to work experimentally. Before applying significant effort to develop double exposure materials, their feasibility can be determined using rigorous simulation techniques. This work presents a feasibility study of four types of double exposure materials and their potential process windows.

The ability to mass produce biosensor arrays at low costs is an important target for the diagnostics industry. Our group has previously explored the batch production of mesoscale sized hydrogels as platforms for biosensors using photolithographic techniques. The individual hydrogel features were self-assembled through lateral capillary interactions to form a closed packed configuration and the pre-polymer medium was subsequently UV-cured to form the array. To understand the self-assembly dynamics, we investigated, through simulation, the flotation behavior of two assembling particles and its dependence on physical constants such as surface tension and particle density. Simulation results revealed that the objects tilt toward each other as they came into proximity. The tilt angle decreased with increasing surface tension but increased with increasing particle density. Understanding the details of the flotation behavior is necessary in the development of a full scale self-assembly model.