Vistec Electron Beam (Germany)

Abstract SETs (Single-Electron-Transistors) arouse growing interest for their very low energy consumption. For future industrialization, it is crucial to show a CMOS-compatible fabrication of SETs, and a key prerequisite is the patterning of sub-20 nm Si Nano-Pillars (NP) with an embedded thin SiO2 layer. In this work, we report the patterning of such multi-layer isolated NP with e-beam lithography combined with a Reactive Ion Etching (RIE) process. The Critical Dimension (CD) uniformity and the robustness of the Process of Reference are evaluated. Characterization methods, either by CD-SEM for the CD, or by TEM cross-section for the NP profile, are compared and discussed.

Stimulated Raman Scattering (SRS) microscopy is a powerful nonlinear optical microscopy technique that images biological structures by exploiting the characteristic, vibrational contrast of the sample molecules. SRS provides a rich, chemically specific and biophysical image contrast that is in many ways complementary to the molecular contrast of fluorescence microscopy. Here, we present a range of applications of SRS, including label-free morphochemical imaging in model organisms, the characterization of organoids and spheroids, and investigations of brain tissues for neurodegenerative disease research. We show specifically that SRS can provide novel insights into the biophysical properties and biochemical composition of Amyloid-β plaques in a mouse model of Alzheimer’s disease. Our results highlight the potential of SRS to contribute to a deeper understanding of cell and tissue biology, and to serve as a powerful tool for preclinical and translational research.

Probing the diffusion of molecules has become a routine measurement across the life sciences, chemistry and physics. It provides valuable insights into reaction dynamics, oligomerisation, molecular (re-)organisation or cellular heterogeneities. Fluorescence correlation spectroscopy (FCS) is one of the widely applied techniques to determine diffusion dynamics in two and three dimensions. This technique relies on the temporal autocorrelation of intensity fluctuations but recording these fluctuations has thus far been limited by the detection electronics, which could not efficiently and accurately time-tag photons at high count rates. This has until now restricted the range of measurable dye concentrations, as well as the data quality of the FCS recordings, especially in combination with super-resolution stimulated emission depletion (STED) nanoscopy.Here, we investigate the applicability and reliability of (STED-)FCS at high photon count rates (average intensities of more than 1 MHz) using novel detection equipment, namely hybrid detectors and real-time gigahertz sampling of the photon streams implemented on a commercial microscope. By measuring the diffusion of fluorophores in solution and cytoplasm of live cells, as well as in model and cellular membranes, we show that accurate diffusion and concentration measurements are possible in these previously inaccessible high photon count regimes. Specifically, it offers much greater flexibility of experiments with biological samples with highly variable intensity, e.g. due to a wide range of expression levels of fluorescent proteins. In this context, we highlight the independence of diffusion properties of cytosolic GFP in a concentration range of approx. 0.01–1 µm. We further show that higher photon count rates also allow for much shorter acquisition times, and improved data quality. Finally, this approach also pronouncedly increases the robustness of challenging live cell STED-FCS measurements of nanoscale diffusion dynamics, which we testify by confirming a free diffusion pattern for a fluorescent lipid analogue on the apical membrane of adherent cells.

Laser-induced choroidal neovascularization (CNV) is a well-established model to mimic the wet form of age-related macular degeneration (AMD). In this protocol, we aim to guide the reader not simply through the technical considerations of generating laser-induced lesions to trigger neovascular processes, but rather focus on the powerful information that can be obtained from multimodal longitudinal in vivo imaging throughout the follow-up period. The laser-induced mouse CNV model was generated by a diode laser administration. Multimodal in vivo imaging techniques were used to monitor CNV induction, progression and regression. First, spectral domain optical coherence tomography (SD-OCT) was performed immediately after the lasering to verify a break of Bruch's membrane. Subsequent in vivo imaging using fluorescein angiography (FA) confirmed successful damage of Bruch's membrane from serial images acquired at the choroidal level. Longitudinal follow-up of CNV proliferation and regression on days 5, 10, and 14 after the lasering was performed using both SD-OCT and FA. Simple and reliable grading of leaky CNV leasions from FA images is presented. Automated segmentation for measurement of total retinal thickness, combined with manual caliber application for measurement of retinal thickness at CNV sites, allow unbiased evaluation of the presence of edema. Finally, histological verification of CNV is performed using isolectin GS-IB4 staining on choroidal flatmounts. The staining is thresholded, and the isolectin-positive area is calculated with ImageJ. This protocol is especially useful in therapeutics studies requiring high-throughput-like screening of CNV pathology as it allows fast, multimodal, and reliable classification of CNV pathology and retinal edema. In addition, high resolution SD-OCT enables the recording of other pathological hallmarks, such as the accumulation of subretinal or intraretinal fluid. However, this method does not provide a possibility to automate CNV volume analysis from SD-OCT images, which has to be performed manually.

In this paper we report different methods to improve the stray light performance of binary spectrometer gratings fabricated by electron beam lithography. In particular, we report the optimization concerns about spurious stray light peaks, also known as "Rowland ghosts". As already known these Rowland ghosts arise from a non-optimized stitching process of special subareas needed in order to fabricate large area gratings. One approach to reduce the impact of the stitching errors is the technique of "multi-pass-exposure" (MPE). Furthermore, the potential of a direct improvement of the stitching accuracy via special calibration parameters is examined. In both cases the effects on the stray light performance were determined by angle resolved scattering measurements. The achieved results show that specific calibration parameters of an e-beam writer have a strong influence on the strength of the Rowland ghosts and that their recalibration combined with an adapted writing regime reduces the peaks significantly.

On the Same Wavelength W3+ FAIR for interdisciplinary networking in WetzlarThe past few years have been extremely exciting for everybody who is interested in optics and the neighboring areas.Be it because of the Nobel Prize awarded for the development of super-resolved fluorescence microscopy, the "International Year of Light" campaign of the UN General Assembly, or the amazing outcome of expeditions into outer space.The latest innovations in light sources, optical elements, sensors and imaging methods give insights into cellular components as small as several nanometers or celestial bodies which are light years away.All this indicates that optics and pho tonics is one of the most remarkable and dynamic technology fields at present.Now the question arises: How can we keep pace with the last years in terms of exciting developments and discoveries?Besides the actual product quality, additional aspects are getting more and more important for forward looking companies.To name just two of them: The perfection of workflows and the motivation to team up.Especially for industry applications, an optimized workflow which reduces labor is of particular interest, since time is money.The opportunity to team up and combine products of different manufacturers has additional advantages.A lot of synergies can be exploited, which requires a certain openness -product wise and company wise.But in the end new interactions broaden the application spectrum and will give further insights into unknown territories.Connectivity is the keyword which differentiates the conservative products from the open ones.By the way, this trend is not restricted to the products themselves but also applies to the persons which are involved.Isn't it time to further open your mind for new interactions and connect with like-minded people?The W3+ FAIR is an interdisciplinary networking fair taking place on March 2 -3 in Wetzlar, a city in Hesse with a long history in optics.People from numerous disciplines will find the opportunity there to inform, contact and discuss.Company experts as well as academics and graduates with a background in optics, electronics and mechanics can meet there and exchange ideas to explore new horizons.Have I piqued your interest?Then please make up your own mind and link with people on the same wavelength.

Lithographic patterning encounters growing challenges to meet the requirements of current and future semiconductor technology nodes. Even e-beam lithography is challenged due to the physical characteristic of the whole transfer process including the e-beam blur, electron scattering, and resist effects. These effects cause an unavoidable blurring of the exposed shapes and are often described as process proximity effect. Besides the correction of this process proximity effect pattern contrast and process window for the lithography step have to be regarded. There are promising approaches for contrast enhancing proximity effect correction concepts. To enable a stable patterning great efforts have to be put into decreasing the errors of all involved technologies. The blurring resulting from the transfer process is usually described by a so-called process proximity function (PPF) and mostly approximated by a superposition of two or more Gaussian functions. All algorithms for proximity effect correction use that PPF to perform their correction. Thus, an accurate determination of that PPF contributes to reducing the error budget of the proximity effect correction scheme. Several methods for PPF calibration were introduced in the past. Some are based on modelling the transfer process and performing Monte Carlo simulations. Another common approach is to design and expose calibration patterns, measure the resulting CDs, and obtain the process proximity function as the result of a simulation based parameter fitting to a model function such as a sum of Gaussian functions. In order to respect the increased accuracy requirements an even more accurate description of the PPF is expected. This paper describes the newly developed PPF-explorer method for the calibration of a pointwise proximity function as a complementary technique, which is based on the exposure and evaluation of new calibration layouts. Following the common assumption that a process proximity function is radial-symmetric, we developed radial-symmetric calibration layouts.

For current and future semiconductor technology nodes with critical dimensions of 32 nm or below, the e-beam lithography is faced with increasing challenges to achieve a reasonable patterning of structures, especially if a process with a chemically amplified resist is used. The reasons for these limitations are the physical properties of the transfer process used to print a structure onto the resist-coated substrate, which inherently contains an unavoidable blurring of the deposited e-beam energy around the desired shape. This blurring is usually described by a so called process proximity function (PPF) and mostly approximated by a superposition of two or more Gaussian functions. The PPF includes the e-beam blur, electron forward scattering and resist effects (often described altogether by the so called alpha parameter of the PPF [K. Keil et al, "Resolution and total blur: Correlation and focus-dependencies in e-beam lithography," J. Vac. Sci. Technol. B 27, 2722 (2009)]) as well as the backscattering effect (often described by the so called beta parameter of the PPF). When the desired critical dimensions of structures are near or below the alpha parameter of the PPF, depending on their environment it may be just impossible to print the structures because of the vanishing image contrast. The PPF model confirms this well-known behavior but also shows ways and limits for improvements. This paper provides real pattern lithography results - comparing classical and GIDC correction - for exposures done on a Vistec SB3050DW shaped e-beam writer. A performance comparison of the GIDC method and the classical dose correction in terms of data preparation and writing time is presented.

In this paper a full package high throughput multi electron-beam approach, called Multi Shaped Beam (MSB), for applications in mask making as well as direct write will be presented including complex proof-of-lithography results. The basic concept enables a significant exposure shot count reduction for advanced patterns compared to standard Variable Shaped Beam (VSB) systems and allows full pattern flexibility by concurrently using MSB, VSB and Cell Projection (CP). Proof of lithography results will be presented, which have been performed using a fully operational electron-beam lithography system including data path and substrate scanning by x/y-stage movement.