Photomask registration and overlay metrology by means of 193 nm optics

Klose, Gerd; Kerwien, Norbert; Arnz, M.; Beyer, Dirk; Rosenkranz, Norbert

doi:10.1117/12.801077

Cited by 12 publications

(5 citation statements)

References 6 publications

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“…The basic working principles of PROVE, focusing on the optical beam path including the new auto focus concept and illumination conditions have already been presented at photomask related conferences in 2008 [1,2,3]. The project has made continuous progress and has developed in the meantime from conceptual ideas, over a design on paper to tangible hardware in the lab.…”

Section: Progress In Provementioning

confidence: 96%

“…The impact of e.g. camera noise depends on the feature size, and an analytical formula was already presented at BACUS 2008 [3], which properly describes the scaling effects. However, the complete influence of the camera noise, in the presence of ever so slightly shifted images, also depends on the algorithms used to analyze the captured images.…”

Section: Design Of Experimentsmentioning

confidence: 99%

See 1 more Smart Citation

Monte Carlo simulations of image analysis for flexible and high-resolution registration metrology

Arnz

Klose

Troll

et al. 2009

25th European Mask and Lithography Conference

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The continuous progress of PROVE, the new photomask registration and overlay measurement tool currently under development at Carl Zeiss has been reported at mask related conferences since it's first publication at EMLC 2008. The project has moved in the past year from a final design on paper to functional hardware in the lab. Major tool components such as the climate control unit, the automated mask handling system and the metrology stage have been assembled and successfully tested. The scope of this paper is to report on the current status of PROVE and furthermore present results from simulations utilizing the image analysis routines of the tool. Monte-Carlo simulations were used to analyze the impact of several realistic tool limitations (camera noise, stage and focus noise and imaging telecentricity) on the image analysis process. The evaluation itself was based on a conventional threshold approach to perform both registration and CD measurement simultaneously. The results show, that the routines can deal with the tool imperfections and limit the contribution to the reproducibility error for standard registration markers to a negligible part. Even single contact holes suffer only from small errors, when camera noise is low and image averaging is increased. Employing a generally used test pattern the CD test results also confirm a sufficiently small error contribution to the CD non-uniformity reproducibility . MOTIVATIONPhotomask registration measurement has gained importance with the introduction of the 45 nm technology node and the discussion of double patterning schemes for several device applications. Measuring and analyzing pattern placement is not just a qualification task of high-end photomasks for the most advanced nodes; it also enables the continuous improvement of writing tools and the optimization of the overlay performance for the complete lithography process. Last year at EMLC 2008, the authors informed the mask making community about PROVE, the registration and overlay metrology tool which is currently under development at Carl Zeiss. PROVE addresses in-die measurement capability on production features by means of a high-resolution 193 nm optics, as well as optimized illumination for best contrast and pellicle compatibility. Within the last 12 months the project has made steady progress towards functional hardware as described in the following section of this paper. Meanwhile, the image analysis software has also been programmed, and was utilized for a Monte-Carlo simulation to test its functionality and assess its contribution to the overall error budget. In the main part of the paper, we present the effect of unavoidable machine inaccuracies, such as lateral positioning errors, focus errors, camera noise and telecentricity in the imaging path on the image analysis for registration and CD metrology. PROGRESS IN PROVEThe basic working principles of PROVE, focusing on the optical beam path including the new auto focus concept and illumination conditions have already been presented at photomask rel...

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Section: Progress In Provementioning

confidence: 96%

Section: Design Of Experimentsmentioning

confidence: 99%

Monte Carlo simulations of image analysis for flexible and high-resolution registration metrology

Arnz

Klose

Troll

et al. 2009

25th European Mask and Lithography Conference

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“…The objects under investigation are various masks types such as standard chrome-on-glass (COG), opaque MoSi-on-glass (OMOG), or EUV, all that are to be measured in transmission or reflection. The benefit of a shorter illumination wavelength has already been discussed in [3]. Based on extensive optical simulations, it could be demonstrated that the chosen wavelength of 193 nm at a 0.6 NA enables superior resolution for different types of photomask and production features to be imaged and measured for registration.…”

Section: Resolution Enhancementsmentioning

confidence: 97%

“…The community was introduced to the main tool concepts such as the design of the optical beam path, expected imaging performance, and stage calibration concepts [1][2][3][4][5][6]. PROVE TM as a strategic project currently running at Carl Zeiss combines knowledge and expertise from various departments within Carl Zeiss SMT as well as external partners, M+W Group (environmental control) and HAP Dresden (handling system), both located in Germany.…”

Section: System Descriptionmentioning

confidence: 99%

PROVE, the next generation registration metrology tool: status report

Beyer

Gabella²,

Hughes³

et al. 2010

SPIE Proceedings

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SEMATECH has identified the need for a high resolution photomask pattern placement metrology tool to support SEMATECH member companies' photomask production as well as research and development work. Performance measures of the tool are driven by double exposure/double patterning approaches that will help extend 193nm lithography according to International Technology Roadmap for Semiconductors (ITRS) requirements. Based on its superior and extendable concept, PROVE TM , a new photomask registration and overlay metrology system from Carl Zeiss SMS, was chosen as the winning proposal for tool development by an evaluation team of mask makers and SEMATECH member companies. The scope of the PROVE TM project is to design and build a photomask pattern placement metrology tool to serve the 32 nm node and below. The tool is designed for 193 nm illumination and imaging optics, which enable at-wavelength metrology for current photomask needs. The optical beam path offers registration and critical dimension (CD) metrology using transmitted or reflected light. The short wavelength together with an NA of 0.6 also allows sufficient resolution even at working distances compatible with the use of pellicles, hence enabling the tool for qualification of final masks. The open concept together with the use of 193 nm wavelength enables a higher NA for pellicle-free applications, including extreme ultraviolet (EUV) masks. This paper reports the current status of PROVE TM , highlighting its resolution capabilities while measuring production features as well as key registration specifications.

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“…It requires high resolution capabilities combined with excellent reproducibility and accuracy. For PROVE TM [8,9,10,11], the next generation photomask registration and overlay metrology system currently under development at Carl Zeiss we have chosen a diffraction limited, high resolution optics operating at 193 nm. The tool offers measurements both in transmission and reflection, while providing variable illumination for maximum contrast imaging.…”

Section: Registration Metrologymentioning

confidence: 99%

In-die metrology on photomasks for low k 1 lithography

2009

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New lithography techniques like Double Patterning, Computational Lithography and Source Mask Optimization will be used to drive immersion lithography to its limits. This results in several challenges for the mask maker. The extremely high MEEF values amplify small process variations on the mask features on the wafer. Complex mask features using sophisticated OPC and assist features as well as double patterning tightens the registration and CDU specification at the same time. Especially, overlay becomes more and more critical and must be ensured on every die. In-die registration and CD metrology on arbitrary features is required to measure mask performance precisely.In this paper an overview about several in-die metrology techniques will be given. Application of in-die CD measurements using the Zeiss WLCD32 tool as well as in-die registration measurements using the Zeiss Prove tool will be shown and discussed.

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Photomask registration and overlay metrology by means of 193 nm optics

Cited by 12 publications

References 6 publications

Monte Carlo simulations of image analysis for flexible and high-resolution registration metrology

Monte Carlo simulations of image analysis for flexible and high-resolution registration metrology

PROVE, the next generation registration metrology tool: status report

In-die metrology on photomasks for low k 1 lithography

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