@article{ElvirettiLiskerLukoseetal.2022, author = {Elviretti, M. and Lisker, Marco and Lukose, Rasuole and Lukosius, Mindaugas and Akhtar, Fatima and Mai, Andreas}, title = {Reliable metal-graphene contact formation process flows in a CMOS-compatible environment}, series = {Nanoscale Advances}, volume = {4}, journal = {Nanoscale Advances}, publisher = {Royal Society of Chemistry (RSC)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16581}, pages = {4373 -- 4380}, year = {2022}, abstract = {The possibility of exploiting the enormous potential of graphene for microelectronics and photonics must go through the optimization of the graphene-metal contact. Achieving low contact resistance is essential for the consideration of graphene as a candidate material for electronic and photonic devices. This work has been carried out in an 8′′ wafer pilot-line for the integration of graphene into a CMOS environment. The main focus is to study the impact of the patterning of graphene and passivation on metal-graphene contact resistance. The latter is measured by means of transmission line measurement (TLM) with several contact designs. The presented approaches enable reproducible formation of contact resistivity as low as 660 Ω μm with a sheet resistance of 1.8 kΩ/□ by proper graphene patterning, passivation of the channel and a post-processing treatment such as annealing.}, language = {en} } @article{KalishettyhalliMahadevaiahPerezLiskeretal.2022, author = {Kalishettyhalli Mahadevaiah, Mamathamba and P{\´e}rez, Eduardo and Lisker, Marco and Schubert, Markus Andreas and Perez-Bosch Quesada, Emilio and Wenger, Christian and Mai, Andreas}, title = {Modulating the Filamentary-Based Resistive Switching Properties of HfO₂ Memristive Devices by Adding Al₂O₃ Layers}, series = {Electronics}, volume = {11}, journal = {Electronics}, number = {10}, address = {MDPI}, issn = {2079-9292}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-16172}, year = {2022}, abstract = {The resistive switching properties of HfO₂ based 1T-1R memristive devices are electrically modified by adding ultra-thin layers of Al₂O₃ into the memristive device. Three different types of memristive stacks are fabricated in the 130 nm CMOS technology of IHP. The switching properties of the memristive devices are discussed with respect to forming voltages, low resistance state and high resistance state characteristics and their variabilities. The experimental I-V characteristics of set and reset operations are evaluated by using the quantum point contact model. The properties of the conduction filament in the on and off states of the memristive devices are discussed with respect to the model parameters obtained from the QPC fit.}, language = {en} } @article{DrostMarschmeyerFraschkeetal.2022, author = {Drost, Martin and Marschmeyer, Steffen and Fraschke, Mirko and Fursenko, Oksana and B{\"a}rwolf, Florian and Costina, Ioan and Kalishettyhalli Mahadevaiah, Mamathamba and Lisker, Marco}, title = {Etch mechanism of an Al₂O₃ hard mask in the Bosch process}, series = {Micro and Nano Engineering}, volume = {14}, journal = {Micro and Nano Engineering}, publisher = {Elsevier}, issn = {2590-0072}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15678}, year = {2022}, abstract = {The etching of high aspect ratio structures in silicon via the Bosch process is essential in modern technologies such as microelectromechanical systems (MEMS) and through‑silicon vias (TSV) fabrication. The process can be very demanding on the mask selectivity due to long etching times, and it has been shown that an Al2O3 hard mask is very suitable in this regard, as it offers significantly higher selectivity compared to the conventional SiO2 or resist masks. In this work, we employ a combination of Scanning Electron Microscopy (SEM), Spectroscopic Ellipsometry (SE) and X-Ray Photoelectron Spectroscopy (XPS) depth profiling to scrutinize the Al2O3 mask etching mechanism and therefore the origin of the extraordinary high selectivity. We demonstrate that by increasing the passivation step time, a thicker fluorocarbon polymer layer is formed on the Al2O3, and Al2O3 is then removed with a minuscule average etch rate of 0.01 nm/min. XPS depth profiling reveals that during Deep Reactive Ion Etching (DRIE) using the Bosch process, an AlFx layer is formed between the polymer and Al2O3. As AlFx is non-volatile, it requires sputtering to be removed. If the polymer layer is thick enough to attenuate the incoming ions such that their energy is not sufficient to lead to desorption of AlFx, such as when using a longer passivation time, the mask is not eroded. By investigating the surface after different amounts of DRIE cycles, we also obtained information about the formation rate of AlFx and the changes in the Al2O3 and polymer thicknesses over the course of a DRIE process. These findings further expand the knowledge of DRIE and can help process engineers to tailor the processes accordingly.}, language = {en} }