Historically, improvements in lithography have enabled improved chip technologies. The International Roadmap for Devices and Systems (IRDS) Lithography roadmap predicts where current patterning capability can support future chip generations and where challenges and improvements are needed. It is intended to be used by semiconductor industry participants, by industry analysts, and by researchers who want or need to know how the industry will evolve in the future and what challenges need to be addressed.

在历经了多年的乐观预测与并不顺利的初始尝试阶段后,EUV技术终于在2019年进入批量生产.掩膜制造厂对具有EUV功能的设备投资是巨大的,不仅包括图形写入、检测、量测、修正、视检和清洁等设备,同时还要兼顾用于存储、运输和护膜技术的相关基础设施投入.然而,在掩膜制造厂和晶片厂中,即使是在晶片厂已经进入大规模生产(high volume manufacturing,HVM)的阶段,一些关键问题仍有待解决.本篇将重点针对其中几个问题,探讨如何发展出完善的、衔接连续的掩膜检测、使用、认证策略.尤其是在掩膜质量认证的整体流程中,护膜技术的选择与时序所带来的不确定性将引起一系列的问题.由于缺少数据,无法确定在大功率EUV曝光设备使用过程中产生污染的机理,这就造成了额外的不确定性.对于碳氢化合物沉积层与EUV光子/DUV波段发生反应的问题,需要认真制定监控和再认证计划.掩膜版重新认证周期不仅取决于曝光的晶片数量,还取决于掩膜版在光刻机中加载和卸载的次数,以及掩膜版在使用周期之间的存放时间.通常的做法是:为了确保掩膜版质量,需要将晶片检测和掩膜检测方案相结合,特别是如果采用的护膜不允许使用193 nm波段光学检测方案时,更是如此.为了配合将EUV技术应用于大规模生产,从掩膜版到晶片厂的掩膜整体认证策略应运而生,以此为大背景,本篇将针对权衡利弊和不确定性的研究作深入讨论.

After years of optimistic projections and false starts, 2019 is finally the year that EUV will enter volume production. Mask shop investment in EUV-capable equipment, including writing, inspection, metrology, repair, review and cleaning tools as well as related infrastructure for storage, transportation, and pellicle support has been substantial. However, in both mask shops and wafer fabs, key questions remain unanswered even as high volume manufacturing (HVM) begins in the fab. We will highlight several of these questions that still need to be answered to develop comprehensive, end-to-end strategies for mask inspection, use, and qualification strategies. In particular, we will show how uncertainty over pellicle technology options and timing cascade into a series of questions related to reticle qualification flows throughout the lifetime of a mask.Additional uncertainty comes from the lack of data on reticle contamination mechanisms during use in high-power EUV exposure tools. Concerns over hydrocarbon deposition and reaction with intense EUV photons as well as with the out-of-band DUV present in the system, will require the development of careful monitoring and re-qualification plans. Reticle requalification cycles will be gated not just by the number of wafers exposed, but by the number of times a reticle is loaded and unloaded from the scanner and how long it sits in storage between cycles. We anticipate that a combination of wafer-based and reticle-based inspection will be required to fully ensure reticle quality, especially if a pellicle solution is adopted which does not allow 193nm based inspection. These tradeoffs and uncertainties will be discussed in the context of a full, mask blank to wafer fab reticle qualification strategy for EUV volume manufacturing.

As the Extreme Ultraviolet (EUV) lithography ecosystem is being actively mapped out to enable sub-7nm design rule devices, there is an immediate and imperative need to identify the EUV reticle (mask) inspection methodologies [1]. The introduction of additional particle sources due to the vacuum system and potential growth of haze defects or other film or particle depositions on the reticle, in combination with pellicle uncertainty pose unique inspection challenges when compared to 193i reticles. EUV reticles are typically inspected with optical reticle-inspection tools. However, if there is a pellicle on the EUV mask which is non-transmissive to the optical wavelengths used in the reticle inspection tools, then there is a need for alternative inspection methodologies based on inspection of printed wafers. In addition, due to the potential new defect mechanisms associated with the EUV reticles, fabs are looking for additional methods to re-qualify reticles in production using printed wafer inspections. The printed wafer inspection methodology is referred to as "Reticle Print Verification" or "Reticle Print Check." This paper discusses these alternative inspection methodologies that are being developed in collaboration with imec using an advanced broadband plasma (BBP) patterned wafer optical inspection (KLA-Tencor 3905) and e-beam review systems (KLA-Tencor eDR7280).

Historically, progress in lithography has been driven by steady advances in exposure tool and optical technology; shorter wavelength, higher numerical aperture (NA) and resolution enhancement techniques to drive the k1 factor as close as possible to the physical limit. Over the past decade, however, the pace of progress has been gated more by patterning – what we do after the resist image is printed – than by higher resolution imaging. The emphasis on patterning rather than just printing has created new pressures in many parts of the overall process, beginning with the design itself. The breakdown of lithographic error budgets into CD and OL tolerances has given way to total edge placement error (EPE) budgets where CD, OL and edge roughness, as well as film and etch variations, must all be controlled to meet the required tolerances. Contact hole and cut mask placement have likewise been tightened to single digit EPE budgets. Collaborative research between technology specialists in multiple areas, such as metrology, etch, process control and simulation, will all be required to deliver these patterning solutions for some years to come. This paper will describe some of these challenges in more detail, and suggest directions for future research to keep optical lithography relevant even below the 10 nm node.

In this paper, we present a DSA compliant flow for contact/via layers with immersion lithography assuming the grapho-epitaxy process for cylinders’ formation. We demonstrate that the DSA technology enablement needs co-optimization among material, design, and lithography. We show that the number of DSA grouping constructs is countable for the gridded-design architecture. We use Template Error Enhancement Factor (TEEF) to choose DSA material, determine grouping design rules, and select the optimum guiding patterns. Our post-pxOPC imaging data shows that it is promising to achieve 2-mask solution with DSA for the contact/via layer using 193i at 5nm node.

Directed self-assembly (DSA) is a potential patterning solution for future generations of integrated circuits. Its main advantages are high pattern resolution (similar to 10 nm), high throughput, no requirement of high-resolution mask, and compatibility with standard fab-equipment and processes. The application of Mueller matrix (MM) spectroscopic ellipsometry-based scatterometry to optically characterize DSA patterned contact hole structures fabricated with phase-separated polystyrene-b-polymethylmethacrylate (PS-b-PMMA) is described. A regression-based approach is used to calculate the guide critical dimension (CD), DSA CD, height of the PS column, thicknesses of underlying layers, and contact edge roughness of the post PMMA etch DSA contact hole sample. Scanning electron microscopy and imaging analysis is conducted as a comparative metric for scatterometry. In addition, optical model-based simulations are used to investigate MM elements' sensitivity to various DSA-based contact hole structures, predict sensitivity to dimensional changes, and its limits to characterize DSA-induced defects, such as hole placement inaccuracy, missing vias, and profile inaccuracy of the PMMA cylinder. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)

Measurement and control of line edge roughness (LER) is one of the most challenging issues facing patterning technology. As the critical dimensions (CDs) of patterned structures decrease, an LER of only a few nanometers negatively impacts device performance. Here, Mueller matrix (MM) spectroscopic ellipsometry-based scatterometry is used to characterize LER in periodic line-space structures in 28-nm pitch Si fin samples fabricated by directed self-assembly patterning. The optical response of the MM elements is influenced by structural parameters like pitch, CDs, height, and side-wall angle, as well as the optical properties of the materials. Evaluation and decoupling MM element response to LER from other structural parameters requires sensitivity analysis using scatterometry models that include LER. Here, an approach is developed that can be used to characterize LER in Si fins by comparing the optical responses generated by systematically varying the grating shape and measurement conditions. Finally, the validity of this approach is established by comparing the results obtained from power spectral density analysis of top down scanning electron microscope images and cross-sectional transmission electron microscope image of the 28-nm pitch Si fins. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.

Patterning based on directed self-assembly (DSA) of block copolymer (BCP) has been demonstrated to be a cost-effective manufacturing technique for advanced sub-20-nm structures. This paper describes the application of Mueller matrix spectroscopic ellipsometry (MMSE) based scatterometry to optically characterize polystyrene-b-polymethylmethacrylate patterns and Si fins fabricated with DSA. A regression-based (inverse-problem) approach is used to calculate the line-width, line-shape, sidewall-angle, and thickness of the DSA structures. In addition, anisotropy and depolarization calculations are used to determine the sensitivity of MMSE to DSA pattern defectivity. As pattern order decreases, the mean squared error value increases, depolarization value increases, and anisotropy value decreases. These specific trends are used in the current work as a method to judge the degree of alignment of the DSA patterns across the wafer. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.

Measurement and control of line edge roughness (LER) is one of the most challenging issues facing patterning technology. As the critical dimensions (CD) of patterned structures decrease, LER of only a few nanometers can negatively impact device performance. Here, Mueller matrix spectroscopic ellipsometry (MMSE) based scatterometry is used to determine LER in periodic line-space structures in 28 nm pitch Si fin samples fabricated by directed selfassembly (DSA) patterning. The optical response of the Mueller matrix (MM) elements is influenced by structural parameters like pitch, CD, height, and side-wall angle (SWA), as well as the optical properties of the materials. Evaluation and decoupling MM element response to LER from other structural parameters requires sensitivity analysis using simulations of optical models that include LER. Here, an approach is developed that quantifies Si fin LER by comparing the optical responses generated by systematically varying the grating shape and measurement conditions. Finally, the validity of this approach is established by comparing the results obtained from top down scanning electron microscope (SEM) images and cross-sectional TEM image of the 28 nm pitch Si fins.

Recent years have seen great strides in the development of extreme ultraviolet (EUV) laser-produced plasma sources. Field deployed EUV exposure tools are now capable of facilitating advanced technology node development. Nevertheless, as the required manufacturing exposure dose scales, EUV sources must follow suit and provide 5001000 W to maintain production throughputs. A free-electron laser (FEL) offers a cost effective, single-source alternative for powering an entire EUV lithography program. FEL integration into semiconductor fab architecture will require both unique facility considerations as well as a paradigm shift in lithography operations. Critical accelerator configurations relating to energy recovery, multi-turn acceleration, and operational mode are discussed from engineering/scientific, cost-minimization, and safety perspectives. Furthermore, the individual components of a FEL (electron injector, RF systems, undulator, etc.) are examined with respect to both design and cost, considering existing technology as well as prospective innovations. Finally, FEL development and deployment roadmaps are presented, focusing on manufacturer deployment for the 5 nm or 3 nm technology nodes.[1-3]

Simulations of Mueller matrix spectroscopic ellipsometry (MMSE) based scatterometry are used to predict sensitivity to dimensional changes and defects in directed self-assembly (DSA) patterned contact hole structures fabricated with phase-separated polystyrene-b-polymethylmethacrylate (PS-b-PMMA) before and after etch. The optical signature of Mueller matrix (MM) elements has a complex dependence on the structure topography and orientation, depolarization, and optical properties of the materials associated with the surface and any underlying layers. Moreover, the symmetry properties associated with MM elements provide an excellent means of measuring and understanding the topography of periodic nanostructures. A forward problem approach to scatterometry or optical model based simulations is used to investigate MMSE sensitivity to various DSA based contact hole structures and its limits to characterize DSA induced defects such as hole placement inaccuracy, missing vias, profile inaccuracy of the PMMA cylinder, and process induced defects such as presence of residual PMMA after etching.

Unidirectional design has attracted lots of attention with the scaling down of technology nodes. However, due to the limitation of traditional lithography, printing the randomly distributed dense cuts becomes a big challenge for highly scaled unidirectional layout. Recently directed self-assembly (DSA) has emerged as a promising lithography technique candidate for cut manufacturing because of its ability to form small cylinders inside the guiding templates and the actual pattern size can be greatly reduced. In this paper, we perform a comprehensive study on the DSA cut mask optimization problem. We first formulate it as integer linear programming (ILP) to assign cuts to different guiding templates, targeting at minimum conflicts and line-end extensions. As ILP may not be scalable for very large size problem, we further propose a speed-up method to decompose the problem into smaller ones and solve them separately. We then merge and legalize the solutions without much loss of result quality. The proposed approaches can be easily extended to handle more DSA guiding patterns with complicated shapes. Experimental results show that our methods can significantly reduce the total number of unresolvable patterns and the line-end extensions for the targeted layouts.

In this paper, we demonstrate the unique advantage of dual-frequency mid-gap capacitively coupled plasma (m-CCP) in advanced node patterning process with regard to etch rate / depth uniformity and critical dimension (CD) control in conjunction with wider process window for aspect ratio dependent & microloading effects. Unlike the non-planar plasma sources, the simple design of the mid-gap CCPs enables both metal and non-metal hard-mask based patterning, which provides essential flexibility for conventional and DSA patterning. We present data on both, the conventional multi patterning as well as DSA patterning for trenches / fins and holes. Rigorous CD control and CDU is shown to be crucial for multi patterning as they lead to undesirable odd-even delta and pitch walking. For DSA patterning, co-optimized Ne / Vdc of the dual frequency CCPs would be demonstrated to be advantageous for higher organic-to-organic selectivity during co-polymer etching.

Further enhancements to Monte Carlo and Self-Consistent Field Theory Directed Self-Assembly (DSA) simulation capabilities implemented in GLOBALFOUNDRIES are presented and discussed, along with the results of their applications. We present the simulation studies of DSA in graphoepitaxy confinement wells, where the DSA process parameters are varied in order to determine the optimal set of parameters resulting in a robust and etch transferrable phase morphology. A novel concept of DSA-aware assist features for the optical lithography process is presented and demonstrated in simulations. The results of the DSA simulations and studies for the DSA process using a blend of homopolymers and diblock copolymers are also presented and compared with the simulated diblock copolymer systems.