Query: New-generation projection optics for ArF lithography

Candidate papers:

abstract: We have developed an ArF scanner with 0.7NA, the FPA 5000AS2, to meet the requirements of the semiconductor industry. The biggest improvement of this system from the previous model is its projection optics. The new projection lens design allows residual aberrations to be extremely small in order to satisfy the requirements of increasingly severe device production. Furthermore, the aberrations derived from the manufacturing process are minimized in the same manner as conventional i line and KrF lenses by precisely measuring them with a phase measuring interferometer (PMI) To reduce manufacturing induced aberrations, we calculate various components of imaging performance at each lens manufacturing process and feed them back to the tuning process. Focusing only on aberration in the expression of root mean square (RMS) can never be sufficient for optimal aberration reduction. Lens performance can be optimally improved by gaining a balance among Zernike terms, which represent aberrations, for critical dimensions of various device patterns. It helps us supply users with a projection lens having performance that meets their requirements. This paper reports on the imaging performance of the new lens for both static and dynamic exposure as well as simulation results using PMI data. It also presents the mechanical barrel system that holds the high performance projection lens, intrinsic birefringence (IBR) of CaF2, and leading edge ArF lens technologies such as chemical clean technology. And imaging performance of the newest 0.75 NAArF projection lens is demonstrated.
author_names: Yuji Chiba

Kazuhiro Takahashi
title: New generation projection optics for ArF lithography
venue: SPIE Advanced Lithography
year: 2002

abstract: It is widely expected that 193 nm lithography will be the technology of choice for volume production of the 0.10 micrometer device generation. For this purpose the PAS5500/1100TM Step Scan system, the second generation ArF tool, was developed. It is based on the PAS5500/900TM, the body of which has been adapted to fit the new 0.75 NA StarlithTM projection optics. This high NA enables mass manufacturing of devices following the 0.10 micrometer design rule. The system features a 10 W 2 kHz ArF laser and the AERIALTM II illuminator that can be equipped with a QUASARTM (multipole) option. In order to minimize wafer processing influences on overlay performance ATHENATM off axis alignment with phase modulator is implemented. The usage of Reticle Blue Alignment will further improve overlay as well as increase the system stability. In this paper the PAS5500/1100TM system layout is discussed and the first imaging and overlay results are presented. Imaging performance is illustrated by SEM pictures of 0.10 micrometer dense lines, 0.15, 0.13 and 0.12 micrometer dense contact holes, 0.10 micrometer DRAM isolation patterns, image plane deviation and system distortion fingerprints. Alignment reproducibility and single machine overlay results demonstrate the overlay capability.
author_names: B J Vleeming

Barbra Heskamp

Hans Bakker

Leon Verstappen

Jo Finders

Jan Stoeten

Rainer Boerret

Oliver Roempp
title: ArF step and scan system with 0.75 NA for the 0.10mm node
venue: SPIE Advanced Lithography
year: 2001

abstract: More than 1,000 units of KrF excimer laser steppers were already installed in semiconductor mass production lines which require design rule of less than 0.15 micrometers Higher NA lens compatibility, productivity and CoO become critical issues of KrF excimer laser stepper. Advanced 2kHz KrF excimer laser G20K/G21K offers the solutions for these three issues. Next generation excimer laser ArF has already finished the stage of principle demonstration and has moved to next level of practical inspection, such as stability, productivity, and economic efficiency. Gigaphoton 4kHz ArF, G40A, solved all of these issues. Furthermore sub 0.10 micrometers design rule region F2 laser has been examined at several organizations. In March, 2000, Komatsu successfully developed 2kHz F2 laser for catadioptric projection optics by the fund of NEDO. Gigaphoton is ready to fabricate G20F, 2kHz F2 laser based upon the result of NEDO research. ASET started new F2 laser lithography development program at Hiratsuka Research Center with collaboration of Nikon, Canon, Gigaphoton, Komatsu, and Ushio from April 2000, ending March 2002.
author_names: Hakaru Mizoguchi
title: Progress of light source technologies from KrF laser to F2 laser
venue: Microelectronic and MEMS Technologies
year: 2001

abstract: More than 1,000 units of KrF excimer laser steppers were already installed in semiconductor mass production lines which require design rule of less than 0.15 m. Higher NA lens compatibility, productivity and CoO become critical issues of KrF excimer laser stepper. Advanced 2kHz KrF excimer laser G20K/G21K offers the solutions for these three issues. Next generation excimer laser ArF has already finished the stage of principle demonstration and has moved to a next level of practical demonstration and has moved to next level of practical inspection, such as stability, productivity, and economic efficiency. Gigaphoton 4kHz ArF, G40A, solved all of these issues. Furthermore sub 0.10m design rule region F2 laser has been examined at several organizations. In March, 2000, Komatsu successfully developed 2kHzF2 laser for catadioptric projection optics by the fund of NEDO. Gigaphoton is ready to fabricate G20F, 2kHz F2 laser, based upon the result of NEDO research. ASET started new F2 laser lithography development program at Hiratsuka Research Center with collaboration of Nikon, Canon, Gigaphoton, Komatsu, and Ushio from April 2000, ending March 2002.
author_names: Hakaru Mizoguchi
title: Progress of excimer laser technologies
venue: Other Conferences
year: 2000

abstract: Small field ArF projection optics for experiment is favorable to the prospective study and key technique development for lithography equipment. An ArF projection optics has been designed with specifications of 0.75 numerical aperture (NA) 100mm image field of view and 40X reduction ratio. The designed composite root mean square (RMS) of wave front error of the system can reach 0.03l (l=193.29nm) To achieve diffraction limited resolution, the optical manufacture tolerances of this high NA projection optics are too tight to manufacture, such as radius error within 0.01% central thickness within 2mm and surface figure error less than peak valley (P V) of 1/30l (l=632.8nm) In this paper, two effective compensatory methods are presented to relax the manufacture tolerances before assembly. One method is re computation of air spaces including actual measured values of the radii of curvature and center thickness for each element. The second method is rotating lenses to find the best matching manner of measured surface figure. The results show that radius error, central thickness error and surface figure error can be compensated significantly,and the best performance of the projection optics disregarding assembly error has been acquired. The composite wave front error RMS can reach 0.09l (l=193.29 nm) after compensation, which is much smaller than 0.25l before compensation under the same optical manufacture error. Both methods can also be used in development of industrial lithographic projection optics.
author_names: Xiao Lin Liu

Yan Qiu Li

Ke Liu

Li Wei
title: Two Methods to Loosen Optical Manufacture Tolerances for ArF Projection Optics
year: 2013

abstract: As the numerical aperture (NA) of 193nm immersion lithography projection optics (PO) increasing, polarization aberration (PA) leads to image quality degradation seriously. PA induced by large incident angle of light, film coatings and intrinsic birefringence of lens materials cannot be ignored. An effective method for PA compensation is to adjust lens position in PO. However, this method is complicated. Therefore, in this paper, an easy and feasible PA compensation method is proposed: for ArF lithographic PO with hyper NA (NA=1.2) which is designed by our laboratory, the PA induced critical dimension error (CDE) can be effectively reduced by optimizing illumination source partial coherent factor sout. In addition, the basic idea of our method to suppress pattern placement error (PE) is to adopt anti reflection (AR) multi layers MgF2/LaF3/MgF2 and calcium fluoride CaF2 of [111] crystal axes. Our simulation results reveal that the proposed method can effectively and quantificationally compensate large PA in the optics. In particular, our method suppresses the dynamic range of CDE from 12.7nm +4.3nm to 1.1nm +1.2nm, while keeping PE at an acceptable level.
author_names: Yu Jia

Yanqiu Li

Lihui Liu

Chunying Han

Xiaolin Liu
title: A method for compensating the polarization aberration of projection optics in immersion lithography
venue: Other Conferences
year: 2014

abstract: The 65nm and the subsequent 45nm node lithography require very stringent CD control. To realize high accuracy CD control on an exposure tool, it is essential to reduce wavefront aberrations induced by projection optics design and manufacturing errors and then stabilize the aberrations while the exposure tool is in operation. We have developed two types of new hyper NA ArF projection optics to integrate into our new platform exposure tool: a dry system and a catadioptric system for immersion application. In this paper, aberration measurement results of these projection systems are shown, demonstrating that ultra low aberration is realized. In addition, a new projection optical system has been developed which incorporates high degree of freedom Aberration Controllers and automatic aberration measuring sensors. These controllers and sensors are linked together through Aberration Solver, a software program to determine optimal target values for aberration correction, thereby allowing the projection optics to maintain its best optical properties. The system offers excellent performance in correcting aberrations that come from lens heating, and makes it possible to guarantee extremely low aberrations during operation of the exposure tool.
author_names: Toshiyuki Yoshihara

Bunsuke Takeshita

Atsushi Shigenobu

Yasuo Hasegawa

Yoshinori Ohsaki

Kazuhiko Mishima

Seiya Miura
title: New projection optics and aberration control system for the 45 nm node
venue: SPIE Advanced Lithography
year: 2007

abstract: Critical issues for 150nm DUV lithography using 0.70 NA KrF and 0.60 NA ArF had been investigated. Aberration, coherence variation, mask error effect, and process margin for each case had been analyzed. Current projection lens and illumination optics are getting better and better. However, for 150nm lithography using high NA scanner, a large portion of beam should be traced on the outside of lens pupil and traced on the resist surface with a large incident angle. In such a case, lens aberration effect was observed on field edge, even though strehl ratio of projection lens and coherence variation on field edge had been improved. These effects had been investigated. One other critical issue in high NA scanner is depth of focus. The common depth of focus between dense and isolated patterns in real process using high NA scanner is mainly affected by photoresist thickness. That issue had been also investigated. Another important issue for 150nm DUV lithography is mask error effect. In the case of same design rule, lower (lambda) /NA lens is more favored than higher (lambda) /NA. Mask error issue in high NA KrF and ArF was also analyzed. Total comparisons between high NA KrF and 0.60 NA ArF have been discussed.
author_names: Dong-gyu Yim

Ki-Sung Kwon

Young-mog Ham

Ki-Ho Baik
title: Comparison study for sub 150 nm DUV lithography between high NA KrF and ArF lithography
venue: Advanced Lithography
year: 1999

abstract: Resolution requirements of below 200nm require the introduction of high NA catadioptric projection optics and the development of short wavelength laser illumination. The numerical aperture (NA) of the projection optics available for step and scan lithography has now been increased form 0.5 to 0.6 and KrF excimer laser illumination introduced. This paper examines the initial performance results achieved using the high NA (0.6) optics illuminated with a KrF excimer laser. Experimental data, using TDUV 009 PM, TDUV 010 PM, and CGR resists is used to illustrate the performance of 0.5 and 0.6 NA optics. Depth of focus and resolution are measured, and initial optics performance results are provided. The linearity of grouped and isolated line features is used to illustrate the lithographic resolution. Lithographic simulations (PROLITH and SPLAT) are used to show the effects of quadrupole illumination for the enhancement of depth of focus with 200nm lithography. The next generation step and scan lithography, which uses ArF (193nm) excimer illumination, is discussed. It is indicated that the step and scan technique will allow optical lithography to extend to 180nm resolution and below.
author_names: Harry Sewell
title: Advancing optical lithography using catadioptric projection optics and step and scan
venue: Advanced Lithography
year: 1996

abstract: Last year we developed an optics system for new generation ArF scanner. The optics' NA was 0.85, the lens field size was 26mm X 8 mm and the lens now is equipped onto FPA 6000AS4. Various performance improvements are made to FPA 6000AS4 to respond to tougher and tougher requirement of the lithography process. The optics improvement is not limited to aberration reduction but extends to such lens manufacturing technology as minimizing the impact of birefringence of the glass element at lens assembly. In the first part of the paper enhancement method and accomplishment of lens manufacturing technology is discussed. Lithography technology is not limited only to ArF. We developed 0.86 NA KrF system, too. The system aims to realize easy, inexpensive leading edge lithography by taking advantage of matured, highly performing resist and low process cost. The lens resolves 90nm pattern using usual halftone reticle and goes down to 85nm with strong RET, Levenson mask etc. By utilizing the accomplishments realized for ArF lens, aberration of the lens is extremely small. Performance evaluation result of this high NA KrF lens and extendibility of 248nm with RET is reported in the latter part of this paper.
author_names: Tomohiro Hoshino
title: Improving ArF lens performance and new generation high NA KrF optical system
venue: SPIE Advanced Lithography
year: 2004