Flare mitigation strategies in extreme ultraviolet lithography

Jiang³

et al. 2009

SPIE Proceedings

Accurate modeling of EUV Lithography is a mandatory step in driving the technology towards its foreseen insertion point for 22-16nm node patterning. The models are needed to correct EUV designs for imaging effects, and to understand and improve the CD fingerprint of the exposure tools. With a full-field EUV ADT from ASML now available in the IMEC cleanroom, wafer data can be collected to calibrate accurate models and check if the existing modeling infrastructure can be extended to EUV lithography. As a first topic, we have measured the CD on wafer of a typical OPC dataset at different flare levels and modeled the evolution of wafer CD through flare, reticle CD, and pitch using Brion's Tachyon OPC engine. The modeling first requires the generation of a flare map using long-range kernels to model the EUV specific long-range flare. The accuracy of the flare map can be established independently from the CD measurements, by using the traditional disappearing pad test for flare determination (Kirk test). The flare map is then used as background intensity in the calibration of the traditional optical models with short-range kernels. For a structure set of 600 features and over a flare range of 4-6%, an rms fit value of 0.9nm was obtained. As a second aspect of the modeling, we have calibrated a full resist model to process window data. The full resist model is then used in a combination with experimental measurements of reticle CD, slit intensity uniformity, focal plane behavior, and EUV thick mask effects to model the evolution of wafer CD across the exposure field. The modeled evolution of CD across the exposure field was found to be a good match to the experimentally seen evolution of CD across the field, and confirms that the 4 factors mentioned above are main contributions to the CD uniformity across the field. As such the modeling work enables a better understanding of the errors contributing to CD variation across the field for EUV technology.

Section: Validation Of Flare Modelingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Accurate models for EUV lithography

Jiang³

et al. 2009

SPIE Proceedings

“…[1][2][3][4][5][6][7][8][9] The range of influence of flare in EUV is extremely broad ͑millimeters or more͒, thus implying that an effective full-chip compensation strategy is needed to be able to satisfy the requirements for the 32-nm node and beyond. 4,5 At the core of any strategy for flare correction is the ability to accurately and effectively calculate the local flare levels across the chip design, producing what is commonly known as a flare map.…”

Section: Introductionmentioning

confidence: 99%

“…4,5 At the core of any strategy for flare correction is the ability to accurately and effectively calculate the local flare levels across the chip design, producing what is commonly known as a flare map. [1][2][3] The calculation of flare maps in a reasonable time is not an obvious task, requiring the convolution of an extended point-spread function ͑PSF͒ at a reasonable resolution, but a great deal of progress has been made recently in this direction. 2,3 To confirm the correctness of flare calculation, the comparison to measured values is critical.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3] The calculation of flare maps in a reasonable time is not an obvious task, requiring the convolution of an extended point-spread function ͑PSF͒ at a reasonable resolution, but a great deal of progress has been made recently in this direction. 2,3 To confirm the correctness of flare calculation, the comparison to measured values is critical. It is also essential that the basic requirements of a decent flare metrology are satisfied on the experimental side.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Flare in extreme ultraviolet lithography: metrology, out-of-band radiation, fractal point-spread function, and flare map calibration

Roey

J. Micro/Nanolith. MEMS MOEMS

et al. 2009

The critical role of flare in extreme ultraviolet ͑EUV͒ lithography is well known. In this work, the implementation of a robust flare metrology is discussed, and the proposed approach is qualified both in terms of precision and accuracy. The flare measurements are compared to full-chip simulations using a simplified single fractal point-spread function ͑PSF͒, and the parameters of the analytical PSF are optimized by comparing the simulation output to the experimental results. After flare map calibration, the matching of simulation and experiment in the flare range from 4 to 12% is quite good, clearly indicating an offset of about 3%. The origin of this offset is attributed to the presence of DUV light. An experimental estimate of the DUV component is found in good agreement with the predicted value.

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

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

Davydova

et al. 2011

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.