Dr. Tanja Bizjak Profile

Dr. Tanja Bizjak

Key Account Manager at SCHOTT AG

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Publications (6)

Proceedings Article | 13 March 2012 Paper

ZERODUR: bending strength data for tensile stress loaded support structures

Tanja Bizjak, Peter Hartmann, Thomas Westerhoff

Proceedings Volume 8326, 83261Q (2012) https://doi.org/10.1117/12.917042

KEYWORDS: Glasses, Failure analysis, Ceramics, Diamond, Corrosion, Zerodur, Surface finishing, Silver, Solids, Structural design

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In the past ZERODUR® was mainly used for mirror and substrate applications, where mechanical loads were given by its own weight. Nowadays substrates become more sophisticated and subject to higher stresses as consequences of high operational accelerations or vibrations. The integrity of structures such as reticle and wafer stages e.g. must be guaranteed with low failure probability over their full intended life time. Their design requires statistically relevant strength data and information. The usual way determining the design strength employs statistical Weibull distributions obtained from a set of experimental data extrapolating the results to low acceptable failure probability values. However, in many cases this led to allowable stress values too low for the intended application. Moreover, the experimental basis has been found to be too small for reliable calculations. For these reasons measurement series on the strength of ZERODUR® have been performed with different surface conditions employing a standardized ring-on-ring test setup. The numbers of specimens per sample have been extended from about 20 to 100 or even much more. The results for surfaces ground with different diamond grain sizes D151, D64 and D25 as well as for etched surfaces are presented in this paper. Glass ceramics like all glassy materials exhibit some strength reduction when being exposed to loads above a tensile stress threshold over long time periods. The strength change of ZERODUR® with time will be discussed on the basis of known and newly determined stress corrosion data. The results for samples with large numbers of specimens contribute new aspects to the common practice of extrapolation to low failure probability, since they provide evidence for the existence of minimum strength values depending on the structures surface conditions. For ground surfaces the evidence for minimum strength values is quite obvious. For etched surfaces minimum values are to be expected also. However, here closer observation is still needed. The systematic deviations from Weibull distributions lie below about 5 % failure probability and thus could not be seen in small samples as they were common in the past.

Proceedings Article | 4 March 2010 Paper

Novel continuously shaped diffractive optical elements enable high efficiency beam shaping

Yuri Miklyaev, Waleri Imgrunt, Vladimir Pavelyev, Denis Kachalov, Tanja Bizjak, Lutz Aschke, Vitalij Lissotschenko

Proceedings Volume 7640, 764024 (2010) https://doi.org/10.1117/12.846573

KEYWORDS: Beam splitters, Diffractive optical elements, Manufacturing, Beam shaping, Optics manufacturing, Optical components, Lithographic illumination, Micro optics, Diffraction gratings, Lithography

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Proceedings Article | 24 March 2009 Paper

Inspection and metrology tools benefit from free-form refractive micro-lens and micro-lens arrays

Tanja Bizjak, Thomas Mitra, Lutz Aschke

Proceedings Volume 7272, 72723Q (2009) https://doi.org/10.1117/12.814264

KEYWORDS: Inspection, Metrology, Micro optics, Lenses, Sensors, Semiconducting wafers, Aspheric lenses, Optics manufacturing, Metals, Manufacturing

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Proceedings Article | 12 September 2008 Paper

Free form micro-optics enables uniform off-axis illumination and superposition of high power laser devices

Tanja Bizjak, Oliver Homburg, Andreas Bayer, Thomas Mitra, Lutz Aschke

Proceedings Volume 7062, 70620T (2008) https://doi.org/10.1117/12.794686

KEYWORDS: High power lasers, Beam shaping, Spherical lenses, Homogenization, Superposition, Laser cutting, Lithographic illumination, Semiconductor lasers, Aspheric lenses, Micro optics

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Proceedings Article | 7 March 2008 Paper

Novel refractive optics enable multipole off-axis illumination

T. Bizjak, T. Mitra, D. Hauschild, L. Aschke

Proceedings Volume 6924, 69242J (2008) https://doi.org/10.1117/12.771213

KEYWORDS: Micro optics, Lens design, Chemical elements, Deep ultraviolet, Optical components, Beam shaping, Manufacturing, Optics manufacturing, Semiconducting wafers, Lithographic illumination

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Optical lithography in the deep ultraviolet (DUV) region is being pushed to reach the limits of printing resolution. The effort required to achieve the 32 nm structure with this technology puts very hard conditions and requests on the illumination optics. Different kinds of illumination modes are combined to get into a regime of extreme numerical aperture (hyper NA). Arrays of refractive micro-optics have been and continue to be the ideal solution for high transmission homogenizing elements for several tool generations. Illumination of the masks with high numerical aperture is critical for achieving the smallest structure on the semiconductor material. Exposure tools use different illumination modes to get better imaging of certain mask structures. The beam shaping necessary to create these illumination modes is achieved mostly with diffractive elements. Most of the currently used modes can also be created with arrays of refractive micro-optics, manufactured from fused silica and calcium fluoride. The advantage over the diffractive optical elements lies in efficiency, which comes close to 90%. An important prerequisite for these special types of optical elements is LIMO's unique production technology which can manufacture free form surfaces on monolithic arrays exceeding 200 mm edge length with high precision and reproducibility. These homogenizing elements in the illumination optics can provide a custom designed intensity distribution, and offer the possibility to correct the failure of other optical elements. Each lens can be designed individually and can also be shaped asymmetrically. Thus unusual lens sizes and shapes can be produced, and various far fields such as rectangles, lines, hexagons or multi-poles can be achieved. In this paper we present novel refractive micro-optical elements which create rectangular dipole illumination. They can also be combined in such a way as to create a quadrupole with variable intensity ratio between the vertical and horizontal poles. The huge advantage of such a multipole illumination is polarization control and variable intensity in poles. Working on this combination, the resolution can be enhanced even further.

Proceedings Article | 27 March 2007 Paper

Novel high-throughput micro-optical beam shapers reduce the complexity of macro-optics in hyper-NA illumination systems

T. Bizjak, T. Mitra, L. Aschke

Proceedings Volume 6520, 65202X (2007) https://doi.org/10.1117/12.712124

KEYWORDS: Lenses, Semiconducting wafers, Polarization, Spherical lenses, Beam shaping, Photomasks, Micro optics, Microlens array, Lens design, Microlens

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Uniform illumination of the mask is a key factor for the lithography process. The requirements of Immersion Lithography make illumination systems even more complex e.g. by adding additional parameters like polarization and improved throughput. Arrays of refractive microoptics are the ideal solution for high transmission homogenizing elements since several tool generations. These arrays can provide very steep intensity profiles (top hat and other profiles), enable lossless polarization control and do not suffer from zero order losses like diffractive elements. Usually refractive microlens arrays are used with macrooptical field lenses in order to illuminate a field very uniformly or with a customized intensity distribution. High numerical apertures create the necessity for aspherical surfaces which leads to significantly higher lens cost especially for the macrooptics. In this paper we present novel microoptical homogenizers which create extremely uniform intensity distributions for high numerical apertures without any field lens or at least only with spherical field lenses. Especially multi-pole off-axis illumination can be improved with less optical components. An important prerequisite for these special types of homogenizers is that LIMO can produce free form surfaces on monolithic arrays larger than 200 mm with high precision and reproducibility. Every lens can be designed individually and can also be shaped asymmetrically. We will present surface test methods and the final UV tests, guaranteeing the performance for the applications. Example data gained with these tests will be shown with regard to: meeting the design parameters, reproducibility over one wafer and reproducibility in large lots. Monolithic elements based on crossed cylindrical lenses provide a fill factor close to 100%. Simulations and measurements prove that microoptic arrays can be produced which provide a uniformity of the homogenized laser light of significantly better than 1% P-V at numerical apertures above 0.35. Refractive microoptic arrays do not change the polarization state of the transmitted light which is an important prerequisite in immersion exposure tools. LIMO homogenizer sets are manufactured from fused silica and Calcium Fluoride thus they are suitable for all DUV wavelengths at highest laser fluxes.

Showing 5 of 6 publications

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