Second level exposure for phase shift mask applications using an SLM-based DUV mask writer

Chandramouli, Mahesh; Olshausen, Bob; Korobko, Yulia; Henrichs, Sven; Ping, Qu; Ma, Jian; Auches, Bruce; Cole, Damon M.; Ostrom, Thomas M.; Beyerl, Angela; Eklund, Robert; Zerne, R; Göransson, Peter; Persson, Magnus; Newman, Tom

doi:10.1117/12.617359

Cited by 7 publications

(5 citation statements)

References 11 publications

(11 reference statements)

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“…The corner enhancement strength is adjustable, so that corner pullback can be tuned to the application. An example of this is the 2 nd level patterning on alternating PSM, where it is beneficial to match the corner pullback of the 2 nd level features to the underlying 1 st level features that are normally patterned by e-beam exposure tools 11,12 . Corner enhancement is illustrated in Figure 1.…”

Section: Advanced Adjustments Processormentioning

confidence: 99%

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Improved CD uniformity for advanced masks using the Sigma7500 pattern generator and ProcessEqualizer

Eklund

Österberg

Hellgren

et al. 2007

23rd European Mask and Lithography Conference

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Managing the total CD error in advanced mask manufacturing requires that error contributions from writing, process and metrology are minimized. This paper describes how both the writing and process contributions have been addressed in the Sigma7500 DUV laser pattern generator, which prints masks by imaging a programmable spatial light modulator (SLM). System enhancements have reduced the writing contribution to global CD uniformity to 5 nm (3s). Processrelated CD error sources, such as the signatures from mask developing and etching can be significant contributors to the total CD error in mask manufacturing. These errors are classified as being either pattern-independent or patterndependent, and the effects of both can be reduced using the ProcessEqualizer feature of the Sigma7500. This software tool performs CD sizing during writing based on pattern density maps derived during mask data preparation, along with tunable parameters that are determined experimentally. The CD sizing function has no effect on system throughput and does not require flattening and re-fracturing of the pattern data.

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Section: Advanced Adjustments Processormentioning

confidence: 99%

“…Laser patterning is convenient for the 2 nd level, as it does not require the process complications of a discharge layer. For advanced mask applications such as alternating PSM 11,12 , the high throughput of a laser pattern generator is effective in handling the relatively complex pattern files.…”

Section: Second Level Alignment For Psmmentioning

confidence: 99%

Improved CD uniformity for advanced masks using the Sigma7500 pattern generator and ProcessEqualizer

Eklund

Österberg

Hellgren

et al. 2007

23rd European Mask and Lithography Conference

Self Cite

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show abstract

“…The corner enhancement strength is adjustable, so that corner pullback can be tuned to the application. An example of this is the 2 nd level patterning on alternating PSM, where it is beneficial to match the corner pullback of the 2 nd level features to the underlying 1 st level features that are normally patterned by e-beam exposure tools 5,6 . Corner enhancement is illustrated in Figure 3.…”

Section: Advanced Adjustments Processormentioning

confidence: 99%

Sigma7500: an improved DUV laser pattern generator addressing sub-100-nm photomask accuracy and productivity requirements

et al. 2006

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As photomask pattern complexity continues to increase, it becomes more challenging to control write times of shaped ebeam tools. This raises the related concerns of increased mask costs and extended mask cycle times. A strategy for sub-100 nm technology nodes is to use high-speed DUV laser pattern generators for as many layers as possible, reserving ebeam tools for only the most critical layers. With 248 nm optics and high-NA partially coherent imaging, the Sigma7500 increases the application space available to laser pattern generators. Image profiles are steepened with phase shifting methods, and pattern fidelity is improved with on-line corner enhancement. In the Sigma architecture, mask patterns are imaged with full fidelity and addressability in each writing pass. Because of this, the Sigma7500 provides additional means to improve write time by reducing the number of exposure passes. Platform improvements have resulted in a 2-pass writing accuracy that meets the 4-pass specification of the previous system. Write time is typically under two hours in 2-pass mode, compared to approximately three hours for 4-pass. The Sigma7500 can generally be used for all binary mask layers at the 90 nm technology node, and for about half the layers at 45 nm. The ProcessEqualizer TM function addresses long range CD errors arising from mask process effects. Mask data is sized in real time to compensate for process errors related to local pattern density, and also to correct for static process CD signatures. With a through-thelens alignment system and both grid matching and pattern matching capabilities, the tool is also suited to 2 nd layer patterning for advanced phase shifting mask (PSM) applications down to 45 nm, with extendibility to 32 nm. Process integration is facilitated by the use of standard FEP-171 chemically amplified resist (CAR).

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“…Pattern data is rasterized during writing, facilitating real-time corrections. The Sigma7500 is suited to a variety of mask applications [2][3][4] , including binary masks, first level patterning of attenuated PSM, and second level patterning of advanced masks such as alternating PSM. Performance specifications for the system are given in Table 1.…”

Section: Overviewmentioning

confidence: 99%

Improving the CD linearity and proximity performance of photomasks written on the Sigma7500-II DUV laser writer through embedded OPC

et al. 2007

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Optical proximity correction (OPC) is widely used in wafer lithography to produce a printed image that best matches the design intent while optimizing CD control. OPC software applies corrections to the mask pattern data, but in general it does not compensate for the mask writer and mask process characteristics. The Sigma7500-II deep-UV laser mask writer projects the image of a programmable spatial light modulator (SLM) using partially coherent optics similar to wafer steppers, and the optical proximity effects of the mask writer are in principle correctable with established OPC methods.To enhance mask patterning, an embedded OPC function, LinearityEqualizer™, has been developed for the Sigma7500-II that is transparent to the user and which does not degrade mask throughput. It employs a Calibre™ rule-based OPC engine from Mentor Graphics, selected for the computational speed necessary for mask run-time execution. A multinode cluster computer applies optimized table-based CD corrections to polygonized pattern data that is then fractured into an internal writer format for subsequent data processing. This embedded proximity correction flattens the linearity behavior for all linewidths and pitches, which targets to improve the CD uniformity on production photomasks.Printing results show that the CD linearity is reduced to below 5 nm for linewidths down to 200 nm, both for clear and dark and for isolated and dense features, and that sub-resolution assist features (SRAF) are reliably printed down to 120 nm. This reduction of proximity effects for main mask features and the extension of the practical resolution for SRAFs expands the application space of DUV laser mask writing.

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Second level exposure for phase shift mask applications using an SLM-based DUV mask writer

Cited by 7 publications

References 11 publications

Improved CD uniformity for advanced masks using the Sigma7500 pattern generator and ProcessEqualizer

Improved CD uniformity for advanced masks using the Sigma7500 pattern generator and ProcessEqualizer

Sigma7500: an improved DUV laser pattern generator addressing sub-100-nm photomask accuracy and productivity requirements

Improving the CD linearity and proximity performance of photomasks written on the Sigma7500-II DUV laser writer through embedded OPC

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