Effects of flare in extreme ultraviolet lithography: Learning from the engineering test stand

Chandhok, Manish; Lee, Sang H.; Bacuita, Terence

doi:10.1116/1.1824068

Cited by 31 publications

(18 citation statements)

References 8 publications

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“…The flare difference between horizontal and vertical features has been reported in a series of studies, [9][10][11] and it is generally referred to as horizontal-vertical flare anisotropy. Most of these studies however fail to accurately quantify the exact amount of such anisotropy.…”

Section: B Flare Measurementsmentioning

confidence: 98%

“…2 Even if part of the spread could be attributed to the dependence of the spectral characteristics of the source on its components and settings, the differences observed call for additional quantitative investigations on the amount of DUV OoB in EUVL scanners. 6,[9][10][11][12][13][14][15][16][17][18][19] The flare caused by the EUV scattering on the optics roughness is generally larger as compared to optical scanners, and its lateral range (i.e., the distance over which flare matters) is extremely broad (millimeters or more). The proposed approach uses a purposely fabricated aluminum-coated mask with reflectivity that has been qualified in both EUV and DUV wavelength ranges.…”

Section: Introductionmentioning

confidence: 99%

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Metrology development for extreme ultraviolet lithography: Flare and out-of-band qualification

Lorusso

Hendrickx

Davydova

et al. 2011

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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Articles you may be interested inCharacterization of out-of-band radiation and plasma parameters in laser-produced Sn plasmas for extreme ultraviolet lithography light sources Extreme ultraviolet lithography (EUVL) is the leading candidate for lithography beyond the 22 nm half-pitch device manufacturing node. These geometries impose tighter requirements for standard critical dimension metrology and call for new strategies able to quantify and monitor extreme ultraviolet (EUV) specific parameters. In this paper, the approaches to measure two key EUV imaging parameters, namely flare and out-of-band (OoB) radiation, are discussed. EUV sources are known to emit a broad spectrum of wavelengths ranging from EUV to deep ultraviolet (DUV) and beyond. As the DUV can contribute to the photoresist exposure and degrade imaging performance, it is critical to accurately determine the amount of DUV OoB in EUVL exposure tools at the wafer level. In this paper, a methodology using an aluminum-coated reticle to measure the DUV=EUV ratio in resist is discussed. Such a mask is able to provide quantitative in situ information on the scanner DUV content thanks to its ability to transmit DUV and absorb EUV. The experimental OoB results for two EUVL tools are reported and compared with modeling predictions. Flare in EUVL is caused by light scattered by the surface roughness of the optical elements and has a larger impact as compared to optical lithography. As a consequence, a precise and accurate flare metrology is essential to guarantee a proper qualification of the effect, as well as to implement an effective compensation strategy. However, the flare level estimate has been historically based on operator and tool-dependent procedures that are unable to meet the requirements for accuracy and precision dictated by EUVL. A robust in-line approach to flare metrology is developed and qualified. As in the case of OoB, experimental flare results for two EUVL tools are reported. The experimental data are compared to full-chip simulations using the point spread function of the tool's optical system.

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Section: B Flare Measurementsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Metrology development for extreme ultraviolet lithography: Flare and out-of-band qualification

Lorusso

Hendrickx

Davydova

et al. 2011

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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show abstract

“…The flare level on EUVL tools is expected to be high compared to optical scanners, being inversely proportional to wavelength squared and proportional to the mirror surface roughness [4][5][6][7]. The flare specification for the EUV ADT is less than 16% which nevertheless could cause a significant degradation of the patterning performance of the tool.…”

Section: Flare and Shadowingmentioning

confidence: 99%

Imaging performance of the EUV alpha semo tool at IMEC

et al. 2008

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Extreme Ultraviolet Lithography (EUVL) is the leading candidate beyond 32nm half-pitch device manufacturing. Having completed the installation of the ASML EUV full-field scanner, IMEC has a fully-integrated 300mm EUVL process line. Our current focus is on satisfying the specifications to produce real devices in our facilities. This paper reports on the imaging fingerprint of the EUV Alpha Demo Tool (ADT), detailing resolution, imaging, and overlay performance. Particular emphasis is given to small pitch contact holes, which are a critical layer for advanced manufacturing nodes and one of the most likely layers where EUVL may take over from 193nm lithography. Imaging of contact holes, pattern transfer and successful printing of the contact hole level on a 32nm SRAM device is demonstrated. The impact of flare and shadowing on EUV ADT performance is characterized experimentally, enabling the implementation of appropriate mitigation strategies.

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“…However, this simple method is not preferred in many practical cases since the unwanted dummies are printed. More preferable way is to implement straylight impact in OPC [6][7][8][9]. In OPC, an image is calculated as sum of convolution of mask and kernels which is known as Sum Of Coherent Systems (SOCS) [10].…”

Section: Brief Theory Of Stray Lightmentioning

confidence: 99%

Stray-light implementation in optical proximity correction (OPC)

Kim

et al. 2007

SPIE Proceedings

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It is suggested that stray-light (SL, also called flare, scattered light) impact can be compensated by modifying standard OPC method. Compared to traditional optical proximity effect caused by diffraction limit, stray light leads to extremely long range (~ 100 micrometer ~ 10 millimeter) proximity effect. Appropriate approximation is introduced for stray-light implemented OPC in such a large scale. This paper also addresses other practical problems in the stray-light OPC and presents how to solve the problems.

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Effects of flare in extreme ultraviolet lithography: Learning from the engineering test stand

Cited by 31 publications

References 8 publications

Metrology development for extreme ultraviolet lithography: Flare and out-of-band qualification

Metrology development for extreme ultraviolet lithography: Flare and out-of-band qualification

Imaging performance of the EUV alpha semo tool at IMEC

Stray-light implementation in optical proximity correction (OPC)

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