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Author: Alfred Kwok-Kit Wong
Publisher: SPIE Press
ISBN: 9780819439956
Category : Science
Languages : en
Pages : 238
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Book Description
Ever-smaller IC devices are pushing the optical lithography envelope, increasing the importance of resolution enhancement techniques. This tutorial encompasses two decades of research. It discusses theoretical and practical aspects of commonly used techniques, including optical imaging and resolution, modified illumination, optical proximity correction, alternating and attenuating phase-shifting masks, selecting RETs, and second-generation RETs. Useful for students and practicing lithographers
Author: Alfred Kwok-Kit Wong
Publisher: SPIE Press
ISBN: 9780819439956
Category : Science
Languages : en
Pages : 238
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Book Description
Ever-smaller IC devices are pushing the optical lithography envelope, increasing the importance of resolution enhancement techniques. This tutorial encompasses two decades of research. It discusses theoretical and practical aspects of commonly used techniques, including optical imaging and resolution, modified illumination, optical proximity correction, alternating and attenuating phase-shifting masks, selecting RETs, and second-generation RETs. Useful for students and practicing lithographers
Author: F. M. Schellenberg
Publisher: SPIE-International Society for Optical Engineering
ISBN:
Category : Integrated circuits
Languages : en
Pages : 910
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Book Description
Optical lithography for integrated circuits is undergoing a renaissance with the adoption of Resolution Enhancement Technology (RET). Some RET concepts have become routine in manufacturing. This volume gathers together seminal RET papers.
Author: Xinyu Gu
Publisher:
ISBN:
Category :
Languages : en
Pages : 552
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Book Description
The relentless commercial drive for smaller, faster, and cheaper semi-conductor devices has pushed the existing patterning technologies to their limits. Photolithography, one of the crucial processes that determine the feature size in a microchip, is currently facing this challenge. The immaturity of next generation lithography (NGL) technology, particularly EUV, forces the semiconductor industry to explore new processing technologies that can extend the use of the existing lithographic method (i.e. ArF lithography) to enable production beyond the 32 nm node. Two new resolution enhancement techniques, double exposure lithography (DEL) and pitch division lithography (PDL), were proposed that could extend the resolution capability of the current lithography tools. This thesis describes the material and process development for these two techniques. DEL technique requires two exposure passes in a single lithographic cycle. The first exposure is performed with a mask that has a relaxed pitch, and the mask is then shifted by half pitch and re-used for the second exposure. The resolution of the resulting pattern on the wafer is doubled with respect to the features on the mask. This technique can be enabled with a type of material that functions as optical threshold layer (OTL). The key requirements for materials to be useful for OTL are a photoinduced isothermal phase transition and permeance modulation with reverse capabilities. A number of materials were designed and tested based on long alkyl side chain crystalline polymers that bear azobenzene pendant groups on the main chain. The target copolymers were synthesized and fully characterized. A proof-of-concept for the OTL design was successfully demonstrated with a series of customized analytical techniques. PDL technique doubles the line density of a grating mask with only a single exposure and is fully compatible with current lithography tools. Thus, this technique is capable of extending the resolution limit of the current ArF lithography without increasing the cost-of-ownership. Pitch division with a single exposure is accomplished by a dual-tone photoresist. This thesis presents a novel method to enable a dual-tone behavior by addition of a photobase generator (PBG) into a conventional resist formulation. The PBG was optimized to function as an exposure-dependent base quencher, which mainly neutralizes the acid generated in high dose regions but has only a minor influence in low dose regions. The resulting acid concentration profile is a parabola-like function of exposure dose, and only the medium exposure dose produces a sufficient amount of acid to switch the resist solubility. This acid response is exploited to produce pitch division patterns by creating a set of negative-tone lines in the overexposed regions in addition to the conventional positive-tone lines. A number of PBGs were synthesized and characterized, and their decomposition rate constants were studied using various techniques. Simulations were carried out to assess the feasibility of pitch division lithography. It was concluded that pitch division lithography is advantageous when the process aggressiveness factor k1 is below 0.27. Finally, lithography evaluations of these dual-tone resists demonstrated a proof-of-concept for pitch division lithography with 45 nm pitch divided line and space patterns for a k1 of 0.13.
Author: Gianfranco Capetti
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author:
Publisher:
ISBN: 9781109386677
Category : Imaging systems
Languages : en
Pages :
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Book Description
As todays' semiconductor fabrication industry tries to keep up with Moore's Law, which predicts the downscaling of integrated circuit size and the doubling of transistor counts every two years, resolution enhancement techniques (RET) play a much more important role than anytime in the past. Optical proximity correction (OPC), phase shifting mask (PSM), and off-axis illumination (OAI) are RETs used extensively in the semiconductor industry to improve the resolution and pattern fidelity of optical lithography. Preserving the fidelity of the circuit patterns is important for preserving the performance predicted in the design stage of the integrated circuit (IC). Typical circuit patterns exhibit regular geometries, such as lines, L-joint, U-joint and so on. These regular geometries reduce the resistances between nodes and simplify the process of routing. In the past decades, a variety of OPC, PSM and illumination design approaches have been proposed in the literature. In general, these approaches are divided into two subsets: rule-based and model-based approaches. This dissertation focuses on the study and development of model-based OPC, PSM and illumination optimization approaches for both coherent imaging systems and partially coherent imaging systems. For coherent imaging systems, we develop generalized gradient-based RET optimization methods to solve for the inverse lithography problem, where the search space is not constrained to a finite phase tessellation but where arbitrary search trajectories in the complex space are allowed. Subsequent mask quantization leads to efficient design of PSMs having an arbitrary number of discrete phases. In order to influence the solution patterns to have more desirable manufacturability properties, a wavelet regularization framework is introduced offering more localized flexibility than total-variation regularization methods traditionally employed in inverse problems. The algorithms provide highly effective four-phase PSMs capable of generating mask patterns with arbitrary Manhattan geometries. Furthermore, a double-patterning optimization method for generalized inverse lithography is developed where each patterning uses an optimized two-phase mask. These algorithms are computationally efficient, however, they focused on coherent illumination systems. Most practical illumination sources have a nonzero line width and their radiation is more generally described as partially coherent. Partially coherent illumination (PCI) is desired, since it can improve the theoretical resolution limit. PCI is thus introduced in practice through modified illumination sources having large coherent factors or through off-axis illumination. In partially coherent imaging, the mask is illuminated by light travelling in various directions. The source points giving rise to these incident rays are incoherent with one another, such that there is no interference that could lead to nonuniform light intensity impinging on the mask. The gradient-based inverse lithography optimization methods derived under the coherent illumination assumption fail to account for the nonlinearities of partially coherent illumination and thus perform poorly in the partially coherent scenario. For partially coherent imaging systems with inherent nonlinearities, the sum of coherent systems (SOCS) model and the average coherent approximation model are applied to develop effective and computationally efficient OPC optimization algorithms for inverse lithography. Wavelet regularization is added to the optimization framework to reduce the complexity of the optimized masks. Subsequently, a Singular Value Decomposition (SVD) model is used to develop computationally efficient PSM optimization algorithms for inverse lithography. A novel DCT post-processing is proposed to cut off the high frequency components in the optimized PSMs and keep the fabricating simplicity. Furthermore, a photoresist tone reversing technique is exploited in the design of PSMs to project extremely sparse patterns. As traditional RETs, the above mentioned gradient-based inverse OPC and PSM optimization methods fix the source thus limiting the degrees of freedom during the optimization of the mask patterns. To overcome this restriction, computationally efficient, pixel-based, simultaneous source mask optimization (SMO) methods for both OPC and PSM designs are developed in this dissertation. The synergy is exploited in the joint optimization of source and mask patterns. The resulting source and mask patterns fall well outside the realm of known design forms. In these SMO algorithms, the Fourier series expansion model is applied to approximate the partially coherent system as a sum of coherent systems. Cost sensitivity is used to drive the output pattern error in the descent direction. In order to influence the solution patterns to have more desirable manufacturability properties, topological constraints are added to the optimization framework. Several illustrative simulations are presented to demonstrate the effectiveness of the proposed algorithms. The above gradient-based inverse lithography optimization approaches are effective and computationally efficient under the thin-mask assumption, where the mask is considered as a 2-D object. As the critical dimension (CD) printed on the wafer shrinks into the subwavelength regime, the thick-mask effects become prevalent and thus these effects must be taken into account. Thus, OPC and PSM methods derived under the thin-mask assumption have the inherent limitations and perform poorly in the subwavelength scenario. In order to overcome this limitation, the final contribution of this dissertation focuses on developing OPC and PSM optimization methods based on the boundary layer (BL) model to take into account the thick-mask effects. Attributed to the nonlinear properties of the BL model, model-based forward lithography methods are exploited to obtain the optimized binary and phase-shifting masks. The advantages and limitations of the proposed algorithm are discussed and several illustrative simulations are presented.
Author: F. M. Schellenberg
Publisher:
ISBN: 9781628413656
Category :
Languages : en
Pages : 896
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Book Description
Optical lithography for integrated circuits is undergoing a renaissance with the adoption of resolution enhancement techniques (RET). Some RET concepts have become routine in manufacturing, almost two decades after the original applications were conceived. This volume gathers together seminal RET papers. Since many of the first applications were announced by Japanese authors well before the material was presented in English, some of the original Japanese papers are included plus their English translations.
Author: David Michael Newmark
Publisher:
ISBN:
Category :
Languages : en
Pages : 332
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Book Description
Author: Xu Ma
Publisher: John Wiley & Sons
ISBN: 111804357X
Category : Technology & Engineering
Languages : en
Pages : 225
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Book Description
A Unified Summary of the Models and Optimization Methods Used in Computational Lithography Optical lithography is one of the most challenging areas of current integrated circuit manufacturing technology. The semiconductor industry is relying more on resolution enhancement techniques (RETs), since their implementation does not require significant changes in fabrication infrastructure. Computational Lithography is the first book to address the computational optimization of RETs in optical lithography, providing an in-depth discussion of optimal optical proximity correction (OPC), phase shifting mask (PSM), and off-axis illumination (OAI) RET tools that use model-based mathematical optimization approaches. The book starts with an introduction to optical lithography systems, electric magnetic field principles, and the fundamentals of optimization from a mathematical point of view. It goes on to describe in detail different types of optimization algorithms to implement RETs. Most of the algorithms developed are based on the application of the OPC, PSM, and OAI approaches and their combinations. Algorithms for coherent illumination as well as partially coherent illumination systems are described, and numerous simulations are offered to illustrate the effectiveness of the algorithms. In addition, mathematical derivations of all optimization frameworks are presented. The accompanying MATLAB® software files for all the RET methods described in the book make it easy for readers to run and investigate the codes in order to understand and apply the optimization algorithms, as well as to design a set of optimal lithography masks. The codes may also be used by readers for their research and development activities in their academic or industrial organizations. An accompanying MATLAB® software guide is also included. An accompanying MATLAB® software guide is included, and readers can download the software to use with the guide at ftp://ftp.wiley.com/public/sci_tech_med/computational_lithography. Tailored for both entry-level and experienced readers, Computational Lithography is meant for faculty, graduate students, and researchers, as well as scientists and engineers in industrial organizations whose research or career field is semiconductor IC fabrication, optical lithography, and RETs. Computational lithography draws from the rich theory of inverse problems, optics, optimization, and computational imaging; as such, the book is also directed to researchers and practitioners in these fields.
Author: Chris A. Mack
Publisher: Society of Photo Optical
ISBN: 9780819462077
Category : Technology & Engineering
Languages : en
Pages : 122
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Book Description
This Field Guide distills the material written by Chris Mack over the past 20 years, including notes from his graduate-level lithography course at the University of Texas at Austin. It details the lithography process, image formation, imaging onto a photoresist, photoresist chemistry, and lithography control and optimization. An introduction to next-generation lithographic technologies is also included, as well as an extensive lithography glossary and a summation of salient equations critical to anyone involved in the lithography industry.
Author: Alfred K. Wong
Publisher:
ISBN: 9780819478627
Category :
Languages : en
Pages : 0
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Book Description
Ever-smaller IC devices are pushing the optical lithography envelope, increasing the importance of resolution enhancement techniques. This tutorial encompasses two decades of research. It discusses theoretical and practical aspects of commonly used techniques, including optical imaging and resolution, modified illumination, optical proximity correction, alternating and attenuating phase-shifting masks, selecting RETs, and second-generation RETs. Useful for students and practicing lithographers.
