@misc{HeroldAcker, author = {Herold, Steven and Acker, J{\"o}rg}, title = {Measurement of the temperature dependence of lattice deformations in silicon using Raman microscopy}, series = {Journal of Applied Physics}, volume = {126}, journal = {Journal of Applied Physics}, issn = {1089-7550}, doi = {10.1063/1.5090476}, pages = {7}, abstract = {The effect of heating and cooling in the range of 25-900 °C on the lattice deformations of diamond wire-sawn polycrystalline and scratched monocrystalline silicon surfaces was studied in detail using Raman microscopy. Mechanically treated silicon surfaces contain tensile or compressive strained silicon with varying deformation strength and areas with high-pressure silicon phases and amorphous silicon. It is shown that compressive deformed silicon relaxes after heating the sample to 600 °C, while tensile deformed silicon only relaxes after multiple heating and cooling cycles. Raman measurements during the heating and after the cooling phases reveal the individual thermal expansion and relaxation behavior of the deformed silicon states. Compressive deformed silicon relaxes during the heating phase, while tensile deformed silicon relaxes during the cooling phase. It is, therefore, possible to separately relax certain deformation states using thermal annealing without changing the topography of the surface.}, language = {en} } @misc{HuengerDannebergHeroldetal., author = {H{\"u}nger, Klaus-J{\"u}rgen and Danneberg, Matti and Herold, Steven and Acker, J{\"o}rg}, title = {Stress conditions in quartzite and their quantification by Raman spectroscopy}, series = {Proceedings of the 16th International Conference on Alkali-Aggregate Reaction in Concrete}, journal = {Proceedings of the 16th International Conference on Alkali-Aggregate Reaction in Concrete}, publisher = {LNEC}, isbn = {978-972-49-2315-4}, pages = {185 -- 192}, abstract = {The silica solubility of aggregates is one of the most important components of the alkali-silica reaction. It is a surface-controlled process that always still requires more detailed studies to better understand the reaction mechanism. Since strained quartz releases more SiO2 into the pore solution, the properties of grains, crystals and their structure can should be directly quantified. In other work, various possibilities were tested for this purpose in order to obtain analyses of the surface and to correlate these with the mortar bar tests, for example. However, a quantifiable direct measurement of quartz crystal states with satisfactory results has not yet been performed. In this thesis polarization and reflected light microscopy in combination with Raman and confocal microscopy is used to obtain quantifiable data by direct measurement of the strained crystals. First measurements show new surprising signals besides the Raman main peak of the quartz. Such signals cannot be found on the whole sample, but only at places where strains are expected, e.g. at contact zones between different quartz crystals or cracks and sometimes inside of quartz grains too. Thus, a method may have been found to quantify the strained state of different quartz crystals in natural quartzite rocks.}, language = {en} } @inproceedings{HuengerAckerDannebergetal., author = {H{\"u}nger, Klaus-J{\"u}rgen and Acker, J{\"o}rg and Danneberg, Matti and Herold, Steven}, title = {Quantification of stress states in quartzite surfaces by using RAMAN spectroscopy}, series = {27th Annual Conference of the German Crystallographic Society / Zeitschrift f{\"u}r Kristallographie. Supplement}, volume = {39}, booktitle = {27th Annual Conference of the German Crystallographic Society / Zeitschrift f{\"u}r Kristallographie. Supplement}, publisher = {De Gruyter}, address = {Berlin}, isbn = {978-3-11-065403-5}, issn = {0930-486X}, pages = {S. 122}, language = {en} } @inproceedings{HeroldAcker, author = {Herold, Steven and Acker, J{\"o}rg}, title = {Measurement of the temperature dependence of lattice deformations in silicon using Raman microscopy}, series = {9th European Silicon Days, 9-12 September 2018, Saarbr{\"u}cken, Germany, Book of abstracts}, booktitle = {9th European Silicon Days, 9-12 September 2018, Saarbr{\"u}cken, Germany, Book of abstracts}, editor = {Scheschkewitz, David and Kickelbick, Guido}, publisher = {Universit{\"a}t des Saarlandes}, address = {Saarbr{\"u}cken}, pages = {S. 197}, abstract = {One of the most common methods to analyse silicon materials is Raman-spectroscopy.[1] More recently there is a focus in the analysis of lattice deformations during sample preparations.[2] These deformations not only increase the chance of crack formation but also increases the chemical reactivity of the silicon towards etch processes or oxidation processes.[3] In this contribution, we will present our latest Raman evaluation technique for silicon lattice deformation and a way to control them using rapid thermal annealing. The transitions and relaxation of different lattice deformation states after the rapid heating to up to 900°C will be analysed in detail, while also the recrystallisation of amorphous silicon will be discussed from the aspects of lattice deformations. It will be shown that during the tempering the lattice deformation on scratched, indented or diamond wire sawn samples homogenises to a mainly weak tensile deformed state and that these homogenisation processes happen only up to certain critical temperatures.}, language = {en} } @inproceedings{HeroldAcker, author = {Herold, Steven and Acker, J{\"o}rg}, title = {The influence of lattice deformations on the etch rates of potassium hydroxide on silicon}, series = {9th European Silicon Days, 9-12 September 2018, Saarbr{\"u}cken, Germany, Book of abstracts}, booktitle = {9th European Silicon Days, 9-12 September 2018, Saarbr{\"u}cken, Germany, Book of abstracts}, editor = {Scheschkewitz, David and Kickelbick, Guido}, publisher = {Universit{\"a}t des Saarlandes}, address = {Saarbr{\"u}cken}, pages = {S. 198}, abstract = {One of the most common methods to analyse silicon materials is Raman-spectroscopy.[1] More recently there is a focus in the analysis of lattice deformations during sample preparations.[2] These deformations not only increase the chance of crack formation but also increases the chemical reactivity of the silicon towards etch processes or oxidation processes.[3] In this contribution, we will present our latest results on the influence of lattice deformations induced by scratches and saw damage on the etch rate of potassium hydroxide. The lattice deformation will be measured using Raman-microscopy and correlated with the height difference measured with confocal microscopy. It will be shown that the etch rate strongly depends on the lattice deformation and that the etch rate will increase by up to the factor 10 in areas with tensile deformation.}, language = {en} } @misc{HeroldAcker, author = {Herold, Steven and Acker, J{\"o}rg}, title = {Analysis of the strain dependent acidic etch rate on diamond wire sawn silicon wafer}, series = {7th Dresden Nanoanalysis Symposium : "Nano-scale characterization for cutting-edge materials research and sustainable materials development", Abstract booklet}, journal = {7th Dresden Nanoanalysis Symposium : "Nano-scale characterization for cutting-edge materials research and sustainable materials development", Abstract booklet}, editor = {Zschech, Ehrenfried}, publisher = {Fraunhofer IKTS Dresden}, address = {Dresden}, pages = {46}, abstract = {Processing of silicon in microelectronics, photovoltaics and micromechanics includes thermal and mechanical processing that can lead to a change in the silicon lattice, such as phase transitions or lattice deformations which have a crucial impact on the mechanical properties and the chemical resistance of silicon. In this work the correlation between lattice deformations and the etching of silicon using a HF/HNO3 solution is investigated. Here we use Raman microscopy to quantify and qualify strain on mechanically treated silicon, as well as confocal microscopy to measure the topography and to calculate the local etch rate. Additionally, a thermal treatment is used to selectively relax strained silicon for better understanding the effect of a selective kind of strain on the etching mechanism. Our results show that only in tensile strained areas, with a deformation strength of at least 2 cm-1, small cracks are formed within the first 10 seconds of etching. After all strained silicon is etched away the etch process mainly depends on the resulting surface texture. The enhanced oxidation rate of tensile strained silicon by nitric acid is also shown exemplary by the surface modification using nitric acid and trichloro(octyl)silane.}, language = {en} } @misc{HeroldAcker, author = {Herold, Steven and Acker, J{\"o}rg}, title = {Lattice strain enhanced acidic etching on as cut sawn silicon wafer}, series = {Materials Science in Semiconductor Processing}, volume = {123}, journal = {Materials Science in Semiconductor Processing}, issn = {1873-4081}, doi = {10.1016/j.mssp.2020.105575}, pages = {11}, abstract = {The mechanical processing of silicon wafers leads to a heterogeneous lateral strain distribution and various modifications of the silicon, both of which influence the resulting topography after acid etching. In this study we investigate the influence of local strains and the initial topography of slurry and diamond wire saw wafers on the acid etching mechanism. The strain distribution is quantified and qualified by Raman microscopy before and after thermal treatment, while the topography is characterized by confocal microscopy before and after etching. The thermal treatment was used to selectively relax strains and investigate the effect of the individual strains on the etching mechanism. We found that amorphous silicon and compressive strained silicon are mainly present on the top most surface of the saw damage and do not influence the chemical reactivity of acid etching. In contrast, highly reactive tensile strained silicon is found up to 2.7 μm deep in the saw damage and acts as an etching mask. Rapid etching of the tensile strained silicon by HF/HNO3/H2SiF6 leads to the formation of cracks with high local concentrations of intermediate species. These strains induced cracks are etched out together with the original saw damage induced cracks and trenches and form the final surface after etching. Furthermore, we can show how the tensile strain strength must have a relative Raman shift of at least -2 cm-1 to have an effect on the local etch rate. Our data demonstrate how mechanical treatment in combination with thermal treatment and acidic etching can be used to optimize the resulting topography for applications like photovoltaics. In addition, it provides a deeper insight into the acid etching mechanism for non-planar silicon wafers.}, language = {en} } @misc{HeroldAcker, author = {Herold, Steven and Acker, J{\"o}rg}, title = {Strain enhanced chemical oxidation of silicon wafer}, series = {Materials Science in Semiconductor Processing}, volume = {135}, journal = {Materials Science in Semiconductor Processing}, issn = {1369-8001}, doi = {10.1016/j.mssp.2021.106105}, pages = {6}, abstract = {The effect of strain through mechanical processing on the formation of silicon dioxide, one of the most important chemical reactions for the fabrication of semiconductors, biosensors or photovoltaics, has not yet been studied in detail. In this study, we use the surface modification of silicon by alkylsilanes and Raman microscopy techniques to visualise where different oxidants react preferentially on mechanically processed surfaces. We found that HNO3, H2O2 as well as H2SiF6 only oxidise tensile strained silicon areas and do not oxidise unstrained silicon even after long reaction times. Furthermore, a comparison between H2O2 and HNO3 in the presence of HF was also carried out and it was shown that H2O2/HF only etches away tensile strained areas, whereas HNO3/HF initially attacks the tensile strained areas but also forms NOx species. These NOx species then lead to a strain unselective, geometry-based etching mechanism. These results lead to new possibilities in strain lithography,high-precision etching, as well as in the structuring of biosensors and localisation of surface modifications.}, language = {en} } @misc{SpindlerHeroldAckeretal., author = {Spindler, Mario and Herold, Steven and Acker, J{\"o}rg and Brachmann, Erik and Oswald, Steffen and Menzel, Siegfried and Rane, Gerd}, title = {Chemical etching of Tungsten thin films for high-temperature surface acoustic wave-based sensor devices}, series = {Thin Solid Films}, volume = {612}, journal = {Thin Solid Films}, doi = {10.1016/j.tsf.2016.04.035}, pages = {322 -- 326}, abstract = {Surface acoustic wave devices are widely used as wireless sensors in different application fields. Recent developments aimed to utilize those devices as temperature sensors even in the high temperature range (T > N 300 degrees C) and in harsh environmental conditions. Therefore, conventional materials, which are used for the substrate and for the interdigital transducer finger electrodes such as multilayers or alloys based on Al or Cu have to be exchanged by materials, which fulfill some important criteria regarding temperature related effects. Electron beam evaporation as a standard fabrication method is not well applicable for depositing high temperature stable electrode materials because of their very high melting points. Magnetron sputtering is an alternative deposition process but is also not applicable for lift-off structuring without any further improvement of the structuring process. Due to a relatively high Ar gas pressure of about 10(-1) Pa, the sidewalls of the photoresist line structures are also covered by the metallization, which subsequently prevents a successful lift-off process. In this study, we investigate the chemical etching of thin tungsten films as an intermediate step between magnetron sputtering deposition of thin tungsten finger electrodes and the lift-off process to remove sidewall covering for a successful patterning process of interdigital transducers.}, language = {en} } @misc{AckerSieberLangneretal., author = {Acker, J{\"o}rg and Sieber, Tim and Langner, Thomas and Herold, Steven}, title = {The impact of lattice strain on the reactivity of silicon}, series = {Silicon for the Chemical and Solar Industry XIV}, journal = {Silicon for the Chemical and Solar Industry XIV}, editor = {Andresen, Birger and Nygaard, Lars and Rong, Harry and Tangstad, Merete and Tveit, Halvard and Page, Ingrid Gamst}, publisher = {The Norwegian University of Science and Technology}, address = {Trondheim}, pages = {11 -- 20}, abstract = {The present study is focused on the question of how lattice strain mechanically introduced into silicon alters the chemical reactivity of the silicon atoms that are affected by the strain field on a microscopic length scale. The magnitude and local distribution of lattice strain are extracted from confocal Raman microscopy measurements. The reactivity of Si is expressed by the etch rate of Si after treatment with HF-HNO3-H2SiF6 mixtures. Then, the local etch rate is calculated from the local etch depth as determined by confocal microscopy. It has been found that tensile strain leads to the highest enhancement of the etch rate, followed by a compressive strain increase in the etch rate.}, language = {en} }