Effect of line structures on the self-propagating reaction of Al/Ni multilayer. - In: IEEE Xplore digital library, ISSN 2473-2001, (2022), S. 379-382
This work investigates the influence of a structured chip surface on the propagation of a self-sustaining reaction that is aimed to be used as heat source for chip assembly. A silicon (100) surface was structured by a combination of thermal oxidation and dry and wet etching to obtain line structures with height lesser than 1 µm. To ensure reaction of 5 µm thick Al/Ni multilayers, 1 µm of SiO2 is used as thermal insulator. Different widths of lines and valleys, with a ratio of 1:1, were processed. Width values were chosen to be 30 µm, 50 µm and 80 µm. Bilayer thickness of 50 nm with a 50/50 at% of Al/Ni were deposited using magnetron sputtering. By using focused ion beam with integrated scanning electron microscope and X-ray diffractometer the samples were analyzed prior to reaction. Velocity and temperature were measured with high-speed camera and high-speed pyrometer. Variations in reaction speed depending on the structure width were recorded and analyzed in perspective of the influence of the additional inclined reaction path. Calculation of the extended reaction paths and their influence on the reaction speed between the structures was performed. The results show that the additional distance has only a low influence on the velocity. Different reasons were identified, but it was not possible to determine the main cause. It was possible to slow down the reaction and keeping the temperature over 350 ˚C for over 500 ms, which provides enough energy to melt solders. The influence of smaller structures can be applied to bonding applications with reactive multilayers.
First prototype of a positioning device with subatomic resolution. - In: Proceedings of the 22nd International Conference of the European Society for Precision Engineering and Nanotechnology, (2022), S. 97-100
Silicon carbide formation in reactive silicon-carbon multilayers. - In: Materials science forum, ISSN 1662-9752, Bd. 1062 (2022), S. 44-48
An alternative low thermal budget silicon carbide syntheses route is presented. The method is based on self-propagating high-temperature synthesis of binary silicon-carbon-based reactive multilayers. With this technique, it is possible to obtain cubic polycrystalline silicon carbide at relatively low annealing temperatures by a solid state reaction. The reaction starts above 600 ˚C. The transformation process proceeds in a four-step process. The reaction enthalpy was determined to be (-70 ± 4) kJ/mol.
Silicon carbide - graphene nano-gratings on 4H and 6H semi-insulating SiC. - In: Materials science forum, ISSN 1662-9752, Bd. 1062 (2022), S. 170-174
A technical methodology of fabrication of hierarchically scaled multitude graphene nanogratings with varying pitches ranging from the micrometer down to sub 40 nm scale combined with sub 10 nm step heights on 4H and 6H semi-insulating SiC for length scale measurements is proposed. The nanogratings were fabricated using electron-beam lithography combined with dry etching of graphene, incorporating a standard semiconductor processing technology. A scientific evaluation of critical dimension, etching step heights, and surface characterization of graphene nanograting on both polytypes were compared and evaluated.
Nanofabrication and -metrology by using the nanofabrication machine (NFM-100). - In: Proceedings of SPIE, Bd. 12054 (2022), S. 120540A-1-120540A-12
The feature dimensions of integrated circuits are becoming smaller and the fabrication, metrology and inspection is becoming harder to be fulfilled. Fast-writing of long respectively large nano-features with Scanning-ProbeLithography and their inspection with an Atomic Force Microscope (AFM) is a challenge, for the accomplishment of which the Nanofabrication Machine (NFM-100) can serve as a beneficial experimental platform for basic research in the field of scale-spanning nanomeasuring and nanofabrication. The NFM-100 has an integrated tipbased system, which can be used as an AFM as well as for Field-Emission Scanning Probe Lithography (FESPL). The combination of both systems offers the possibility to fabricate and analyze micro- and nanostructures with high resolution and precision down to a single nanometre over a large area of 100 mm in diameter in a single configuration without tool or sensor change. Thus, in contrast to conventional optical inspection and alignment systems, the NFM-100 offers the potential for full lithographic and metrological automation. For FESPL, the implemented active probes enable an in-situ inspection capability, a quantitative mapping at unprecedented resolution, as well as an integrated overlay alignment system. In this paper, the basic set-up of the NFM-100 as well as the capability of the system for long range AFM scans and FESPL is demonstrated.
Metrologische Nanopositionierung kombiniert mit Zwei-Photonen-Laserdirektschreiben :
Metrological nanopositioning combined with two-photon direct laser writing. - In: Technisches Messen, ISSN 2196-7113, Bd. 89 (2022), 7/8, S. 507-514
The extension of nanopositioning and nanomeasuring machines (NPM-machines) to fabrication machines by using a femtosecond laser for the implementation of direct laser writing by means of two-photon absorption (2PA) is a promising approach for cross-scale metrological fabrication in the field of lithographic techniques . To this end, a concept for integrating two-photon technology into an NPM machine was developed and implemented, followed by a characterization of the system and targeted investigations to provide evidence for the synergy of the two techniques. On this basis, a new approach to high-throughput micro- and nano-fabrication was developed and investigated, demonstrating new possibilities in cross-scale, high-precision manufacturing . This mix-and-match approach is based on a combination of 2PA laser writing with field emission lithography to fabricate masters for subsequent nanoimprint lithography. Not only the advantages of the large positioning range of the NMM-1 could be highlighted, but also the advantages resulting from the highly accurate positioning. A systematic reduction of the distance between two adjacent lines resulted in a minimum photoresist width of less than [Math Processing Error] , which can be classified among the smallest distances between two laser-written lines described in the literature , , . The center-to-center distance of the lines of about [Math Processing Error] at a numerical aperture of 0.16 and a wavelength of 801 nm is only about [Math Processing Error] of the Rayleigh diffraction limit extended for the two-photon process. Thus, for the first time, a resist width far below the diffraction limit could be realized with conventional two-photon laser writing in positive photoresist.
Modifications to a high-precision direct laser writing setup to improve its laser microfabrication. - In: Proceedings of SPIE, Bd. 11989 (2022), S. 119890U-1-119890U-7
Two-photon-absorption (2PA) techniques enables the possibility to create extremely fine structures in photosensitive materials. For direct laser writing as micro- or nanofabrication a laser system can be combined with highly precise positioning systems. These are mostly limited by a few hundreds micrometer positioning range with applications based on piezoelectric stages or even just relatively few tens micrometer positioning range with applications based on galvanometer scanners. Although these techniques are precise, but stitching methods are required for larger fabrication areas. Therefore, a setup consisting of a femtosecond laser for 2PA and a nanopositioning and nanomeasuring machine (NMM-1) was developed for high precision laser writing on lager surfaces. Further developments of the system should enable a significant improvement in high-precision and stitching free direct laser writing. In order to combine the the femtosecond laser and the NMM-1 into a functional unit, to write complex structures with highest accuracy and homogeneity, further improvements like a beam expansion for a better use of the numerical aperture of the objective and a new femtosecond laser with a integrated power measurement are realized. This showed improvements in line width for nano strucuring. Advantages and disadvantages as well as further developments of the NMM-1 system will be discussed related to current developments in the laser beam and nanopositioning system optimization.
Electric bias-induced edge degradation of few-layer MoS2 devices. - In: Materials today, ISSN 2214-7853, Bd. 53 (2022), 2, S. 281-284
In this work, we experimentally investigate the effects of electric bias on the degradation of few-layer MoS2 back-gated field-effect transistors in ambient air. The devices were fabricated using mechanically exfoliated MoS2 flakes, which were transferred to a Si/SiO2 substrate by a PDMS-based transfer. We report an accelerated electric bias-induced degradation of the devices under investigation and used optical and scanning electron microscopy (SEM) to monitor changes of the morphology of the MoS2 channel. In particular, we found a linear dependency of the degradation on the electric field between the Ti/Au source and drain contacts. In addition, we identify four regions in which morphological changes occur, of which the edges of the MoS2 channel are most affected.
Nanoscale surface morphology modulation of graphene - i-SiC heterostructures. - In: Materials today, ISSN 2214-7853, Bd. 53 (2022), 2, S. 289-292
A multitude gratings design consists of gratings with different pitches ranging from the micrometre down to sub 40 nm scale combined with sub 10 nm step heights modulating the surface morphology for length scale measurements is proposed. The surface morphology modulation was performed using electron beam lithography incorporating a standard semiconductor processing technology. The critical dimension, edge roughness, step heights and line morphology in dependence on the grating pitch is studied.
Impact analysis of temperature and humidity effects on polishing. - In: EOS Annual Meeting (EOSAM 2021), (2021), 03011, S. 1-3
The polishing process for optical glass is one with intertwined chemical and mechanical processes. The aim of the present study is to verify whether control of these factors can be used to improve the efficiency of the polishing process.