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Measurement of current density distribution in shaped e-beam writers
Horáček, Miroslav ; Bok, Jan ; Kolařík, Vladimír ; Urbánek, Michal ; Matějka, Milan ; Krátký, Stanislav
The ZrO W(100) Schottky cathode is used in our e-beam writing system working with a rectangular-shaped electron beam. The homogeneous angular current density distribution is crucial for quality of exposures of the shaped beam lithography systems. Two basic types of the angular emission distribution can be observed in dependence on the microscopic final end form shape of the emitter tip, with bright centre and more common dark centre. The stable operation of the cathode thus stable end form shape requires a delicate balance of parameters inside the gun which however can slightly change during cathode life time. This implies the necessity of analysing and periodical monitoring the current density distribution in e-beam. Four methods enabling this measurement are presented.
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Monte-Carlo simulation of proximity effect in e-beam lithography
Urbánek, Michal ; Kolařík, Vladimír ; Krátký, Stanislav ; Matějka, Milan ; Horáček, Miroslav ; Chlumská, Jana
E–beam lithography is the most used pattern generation technique for academic and research prototyping. During this patterning by e–beam into resist layer, several effects occur which change the resolution of intended patterns. Proximity effect is the dominant one which causes that patterning areas adjacent to the beam incidence point are exposed due to electron scattering effects in solid state. This contribution deals with Monte Carlo simulation of proximity effect for various accelerating beam voltage (15 kV, 50 kV, 100 kV), typically used in e–beam writers. Proximity effect simulation were carried out in free software Casino and commercial software MCS Control Center, where each of electron trajectory can be simulated (modeled). The radial density of absorbed energy is calculated for PMMA resist with various settings of resist thickness and substrate material. At the end, coefficients of proximity effect function were calculated for beam energy of 15 keV, 50 keV and 100 keV which is desirable for proximity effect correction.
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Comparison of ultimate resolution achieved by e-beam writers with shaped beam and with Gaussian beam
Krátký, Stanislav ; Kolařík, Vladimír ; Matějka, Milan ; Urbánek, Michal ; Horáček, Miroslav ; Chlumská, Jana
This contribution deals with the comparison of two different e–beam writer systems. E–beam writer with rectangular shaped beam BS600 is the first system. This system works with electron energy of 15 keV. Vistec EBPG5000+ HR is the second system. That system uses the Gaussian beam for pattern generation and it can work with two different electrons energies of values 50 keV and 100 keV. The ultimate resolution of both systems is the main aspect of comparison. The achievable resolution was tested on patterns consisted of single lines, single dots (rectangles for e–beam writer with shaped beam) and small areas of periodic gratings. Silicon wafer was used as a substrate for resist deposition. Testing was carried out with two resists, PMMA as a standard resist for electron beam lithography, and HSQ resist as a material for ultimate resolution achievement. Process of pattern generation (exposition) is affected by the same undesirable effect (backscattering and forward scattering of electrons, proximity effect etc.). However, these effects contribute to final pattern (resolution) by various dispositions. These variations caused the different results for similar conditions (the same resist, dose, chemical developer etc.). Created patterns were measured and evaluated by using of atomic force microscope and scanning electron microscope.
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Lift-Off technique using different e-beam writers
Chlumská, Jana ; Kolařík, Vladimír ; Krátký, Stanislav ; Matějka, Milan ; Urbánek, Michal ; Horáček, Miroslav
This paper deals with lift–off technique performed by the way of electron beam lithography. Lift–off is a technique mainly used for preparation of metallic patterns and unlike etching it is an additive technique using a sacrificial material – e.g. e–beam resist PMMA. In this paper we discussed technique of preparation of lift–off mask on two different e–beam writing systems. The first system was BS600 – e–beam writer with rectangular variable shaped beam working with 15keV. The second system was Vistec EBPG5000+ HR – e–beam writer with Gaussian shape beam working with 50 keV and 100 keV. The PMMA resist single layer and bi–layer was used for the lift–off mask preparation. As a material for creation of metallic pattern, magnetron sputtered chromium was used. Atomic force microscope, scanning electron microscope and contact profilometer were used to measure and evaluate the results of this process.
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Microstructuring of metallic layers for sensor applications
Kolařík, Vladimír ; Krátký, Stanislav ; Urbánek, Michal ; Matějka, Milan ; Chlumská, Jana ; Horáček, Miroslav
This contribution deals with a patterning of thin metallic layers using the masking technique by electron beam lithography. It is mainly concentrated on procedures to prepare finger structure in thin Gold layer on electrically isolated Silicon wafer. Both positive and negative tone resists are used for patterning. The thin layer is structured by the wet etching or by the lift-off technique. The prepared structures are intended to be used as a conductivity sensor for a variety of sensor applications. Patterning of the thin layer is performed by the e-beam writer with shaped rectangular beam BS600 by direct writing (without the glass photo mask). Besides the main technology process based on the direct-write e-beam lithography, other auxiliary issues are also discussed such as stitching and overlay precision of the process, throughput of this approach, issues of the thin layer adhesion on the substrate, inter-operation control and measurement techniques.
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E-beam pattern generator BS600 and technology zoom
Kolařík, Vladimír ; Horáček, Miroslav ; Matějka, František ; Matějka, Milan ; Urbánek, Michal ; Krátký, Stanislav ; Král, Stanislav ; Bok, Jan
This contribution deals with an electron beam pattern generator (ELG) working with a rectangular shape variable size electron beam originally developed at Institute of Scientific Instruments (ISI), later on commercialized as a BS600 series by former company Tesla, and recently upgraded by ISI cooperating with several partners. The key issue of this paper is a recently developed exposure mode which is called Technology Zoom (TZ mode) since its original concept until the recent progress. This ELG operating in the TZ mode provides three main advantages when compared to the standard exposure mode: higher exposure speed due to increased beam current density; finer stamp size adjustment and sharper stamp shape due to the stronger size reduction of the shaping aperture. Further, we discussed also some drawbacks and practical issues of the TZ mode. And finally, we summarize some results on real exposure examples. The new exposure mode (together with other recent upgrades) makes the BS600 pattern generator very useful for the nanotechnology patterning tasks and challenges.
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Variable-shape E-beam litography: Proximity effect simulation of 3D micro and nano sructures
Matějka, Milan ; Urbánek, M. ; Kolařík, V. ; Horáček, M. ; Krátký, Stanislav ; Mikšík, P. ; Vašina, J.
A proximity effect simulation technique and developed resist profile simulation for variable-shaped e-beam lithography of three dimensional structures are presented. The e-beam lithography is a technology process which allows high resolution patterning. Most frequently it is used for microfabrication or nanofabrication of two dimensional relief structures such as resist photo masks, etching masks, diffraction gratings, micro and nano optics, photonics and more. However, in the case of the 3D structures patterning the precise thickness control of developed resist is required. With regard to subsequent proximity effect correction, the proximity effect simulation and developed resist profile simulation models are in the case of 3D structures fabrication critically important. We show the results from simulation of exposure and resist development process for the chosen polymer resist (PMMA), using the patterning and simulation e-beam lithography software.
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Calibration specimens for microscopy
Kolařík, Vladimír ; Matějka, Milan ; Matějka, František ; Krátký, Stanislav ; Urbánek, Michal ; Horáček, Miroslav ; Král, Stanislav ; Bok, Jan
Recent developments in nanotechnologies raised new issues in microscopy with nanometer and sub nanometer resolution. Together with the imaging techniques, new approaches in the metrology field are required both in the direct metrology issues and in the area of calibration of the imaging tools (microscopes). Scanning electron microscopy needs the calibration specimens for adjusting the size of the view field (correct magnification) and the shape of that field (correction of deflection field distortions). Calibration specimens have been prepared using different technologies; among them the e–beam patterning and the e–beam lithography have been proved to be appropriate and flexible tool for that task. In the past, we have reported several times our achievements in this field (e.g. [1]). Nevertheless, recent advances of the patterning tool (BS600), mainly the development of the technology zoomed exposure mode [2] and the installation of the magnetic field active cancellation system [3], pushed remarkably the technology necessary for further advances in this area. Within this contribution some theoretical, technology and practical aspects are discussed; achieved results are presented.
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Proximity effect simulation for variable shape e-beam writer
Kolařík, Vladimír ; Matějka, Milan ; Urbánek, Michal ; Král, Stanislav ; Krátký, Stanislav ; Mikšík, P. ; Vašina, J.
Electron Beam Writer (EBW) is a lithographic tool allowing generation of patterns in high resolution. The writing is carried out into a layer of a sensitive material (resist), which is deposited on the substrate surface (e.g. silicon). The resolution of the EBW is limited not only by the beam spot size, but also by the electron scattering effects (forward scattering, backscattering). Thus, even if the beam spot size on the resist surface is very small, due to electron scattering effect in the resist, the exposed area is significantly broader than the original beam spot size [1, 2].
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What is the buzz about the TZ mode
Kolařík, Vladimír ; Matějka, František ; Matějka, Milan ; Horáček, Miroslav ; Urbánek, Michal ; Bok, Jan ; Krátký, Stanislav ; Král, Stanislav ; Mika, Filip
This contribution deals with an e-beam pattern generator BS 600 that works with a variable rectangular spot of electrons (stamp). The TZ stands for the ‘technology zoom’; its meaning is a reduction of the spot size by a factor of 3. Original description of the TZ exposure mode can be found in (1), [2] and [3]; further aspects concerning the exposure system and its electron source were described in [4] and [5]; technology and related topics are discussed in [6], [7], [8] and [9]; overview of application areas is in [10], [11] and [12]; and finally, very recent results are summarized in [13], [14] and [15].
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