Real-world impact of inverse lithography technology

Ho, Jonathan; Wang, Yan; Wu, Xin; Leitermann, Wolfgang; Lin, B. N.; Shieh, Ming Feng; Sun, Jie-wei; Lin, Orson; Lin, Jason; Liu, Yong; Pang, Liang

doi:10.1117/12.632211

Cited by 11 publications

(8 citation statements)

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“…The Luminescent ILT, which was the pioneering product first introduced in 2005/2006, [9][10][11][12][13][14][15][16][17] tried to solve the ILT runtime problem by reducing the number of variables using the level-set method. It also provides a mathematically elegant method for solving topology discontinuity during ILT optimization.…”

Section: Luminescent Level-set Methodsmentioning

confidence: 99%

“…Luminescent announced an ILT product at the 2005 Photomask Technology Conference. Six papers were presented by Luminescent 9,10 and its partners and customers, including UMC and Xilinx, 11 Cypress, 12 SMIC, 13 and Photronics. 14 The author of this ILT review paper, at that time working for Luminescent, was the first to formally name this method "inverse lithography technology" or "ILT," an acronym now universally used by the semiconductor industry.…”

Section: History Of Inverse Lithographymentioning

confidence: 99%

“…The seeds for ILT were sown as early as the 1980s, with academic work. 1,2 By the 1990s, industrial research and development teams had started to work on ILT technologies that could be used in production, [3][4][5][6][7][8] with the first ILT product introduction in 2005/2006, [9][10][11][12][13][14][15][16][17] when the author first coined the term ILT. At this time, dry-process 45-nm lithography was the leading-edge target and was very challenging in terms of process window.…”

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confidence: 99%

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Inverse lithography technology: 30 years from concept to practical, full-chip reality

Pang

2021

J. Micro/Nanopattern. Mats. Metro.

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In lithography, optical proximity and process bias/effects need to be corrected to achieve the best wafer print. Efforts to correct for these effects started with a simple bias, adding a hammer head in line-ends to prevent line-end shortening. This first-generation correction was called rule-based optical proximity correction (OPC). Then, as chip feature sizes continued to shrink, OPC became more complicated and evolved to a model-based approach. Some extra patterns were added to masks, to improve the wafer process window, a measure of resilience to manufacturing variation. Around this time, the concept of inverse lithography technology (ILT), a mathematically rigorous inverse approach that determines the mask shapes that will produce the desired on-wafer results, was introduced. ILT has been explored and developed over the last three decades as the next generation of OPC, promising a solution to several challenges of advanced-node lithography, whether optical or extreme ultraviolet (EUV). Today, both OPC and ILT are part of an arsenal of lithography technologies called resolution enhancement technologies. Since OPC and ILT both involve computation, they are also considered as part of computational lithography. We explore the background and history of ILT and detail the significant milestones that have taken full-chip ILT from an academic concept to a practical production reality.

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Section: Luminescent Level-set Methodsmentioning

confidence: 99%

Section: History Of Inverse Lithographymentioning

confidence: 99%

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confidence: 99%

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Inverse lithography technology: 30 years from concept to practical, full-chip reality

Pang

2021

J. Micro/Nanopattern. Mats. Metro.

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“…[1][2][3][4][5][6][7][8] Then in 2005 and 2006, Luminescent Technologies (later acquired by Synopsys and KLA) introduced the industry's first commercial product and the author coined the term inverse lithography technology (ILT) for this approach. [9][10][11][12][13][14][15][16][17] ILT is a rigorous computational approach to determine the mask shapes that will produce the desired on-wafer results. Given a target wafer shape and models of the lithographic optics, an inverse calculation is made to arrive at the mask pattern that will supply the desired wafer result and the best process window.…”

Section: Curvilinear Ilt Started Over a Decade Agomentioning

confidence: 99%

Breakthrough curvilinear ILT enabled by multi-beam mask writing

Pang

Russell

Baggenstoss

et al. 2021

J. Micro/Nanopattern. Mats. Metro.

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Background: Multi-beam mask writers have been one of the most significant additions to the semiconductor manufacturing equipment arsenal in over a decade. The ability of multi-beam mask writers to write masks with a constant write time regardless of mask shapes or complexity has made them an eagerly anticipated advancement to help write curvilinear mask shapes for both today's advanced 193i nodes and for extreme ultra-violet (EUV) lithography in the future. Perhaps the most obvious application for these new pixel-based mask writers is the production of curvilinear inverse lithography technology (ILT) masks. ILT has been seen as a promising solution to many of the challenges of advanced-node lithography, whether optical or EUV. However, the runtimes and mask writing times associated with this computational technique have limited its practical application. Until recently, it had been used for critical "hotspots" on chips, but had not been used for entire chips.Aim: The introduction of multi-beam mask writing, along with the advent of graphics processing unit (GPU)-accelerated computing for mask and wafer, have enabled the introduction of a new approach to full-chip ILT using these new technologies. The goal was to produce full-chip, curvilinear ILT within the traditional turnaround times of mask shops. Approach:The solution to the runtime problem for ILT has been particularly vexing, as the traditional approach to runtime improvement-partitioning and stitching-has failed to produce satisfactory results, either in terms of runtime or in terms of quality. In 2019, D2S introduced an entirely new, stitchless approach, systematically designed for ILT, multi-beam mask writers, and GPU acceleration, that makes full-chip ILT a practical reality in production for the first time.Results: We present this new ILT approach, first introduced using a multi-beam mask writer to create the complex curvilinear mask shapes. We also review findings that targeting curvilinear mask shapes creates masks that are more resilient to manufacturing variation. Finally, we review the results of this new, stitchless full-chip curvilinear ILT as applied to memory chip making. We show mask making and wafer print results, including pattern fidelity and process window, to demonstrate the actual benefit of such technologies-a doubling in the wafer process windowfor semiconductor manufacturing.

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“…Thus, in recent years another resolution enhancement technique known as inverse lithography (IL) or inverse mask technology has been proposed. [10][11][12][13][14][15] IL is a technique that theoretically calculates/corrects the full mask to compensate for strong image distortion from optical diffraction loss. IL calculates the full mask correction using a nonlinear regression that incorporates the inverse optimization algorithm to obtain a theoretically optimal mask after an elaborate computation.…”

Section: Introductionmentioning

confidence: 99%

Wavefront-based pixel inversion algorithm for generation of subresolution assist features

Yu²,

Chao

2011

J. Micro/Nanolith. MEMS MOEMS

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The generation of subresolution assist features (SRAFs) using inverse-lithography techniques demands extensive computational resources which limits its deployment in advanced CMOS nodes. In this paper, we propose a wavefront-based pixel inversion algorithm to quickly obtain inverse masks with a high aerial image quality. Further assisted by a flexible pattern simplification technique, we present effective SRAF generation and placement based on the calculated inverse mask. The proposed approach can be easily inserted prior to a conventional mask correction flow for subsequent concurrent optimizations of both drawn patterns and SRAFs. The innovative pixel inversion and pattern simplification techniques allow quality mask corrections as produced by inverse lithography while maintaining the convenience of standardized/validated process flows currently used in the industry. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

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Real-world impact of inverse lithography technology

Cited by 11 publications

References 0 publications

Inverse lithography technology: 30 years from concept to practical, full-chip reality

Inverse lithography technology: 30 years from concept to practical, full-chip reality

Breakthrough curvilinear ILT enabled by multi-beam mask writing

Wavefront-based pixel inversion algorithm for generation of subresolution assist features

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