| Zugriffsnummer | 51063 |
| Dokumenttyp | Konferenzartikel |
| Peer Review | unbekannt |
| Sprache | Englisch |
| Titel | New UHV facility for series production of low-cost crystalline standards |
| Autor(in); Institution |
Busch, Ingo; 5.1, Oberflächenmesstechnik, PTB-Braunschweig
Weiser, Florian; 5.1, Oberflächenmesstechnik, PTB-Braunschweig
Ostermann, Johannes; PTB-Braunschweig, formerly
Fernandez Scarioni, Michelle; 5.1, Oberflächenmesstechnik, PTB-Braunschweig
|
| Quelle/Jahr | NanoScale 2023: Dimensional and related measurements in the micro- and nanometre range:(2023), 17 - 18 |
| Artikelnummer | A-3 |
| Konferenzangaben | NanoScale 2023, Helsinki, 10-12, October, 2023, Finland |
| Freie Schlagworte | crystalline standards ; New SI ; Nanofrabrication |
| Zusammenfassung | A gap currently exists for the field of dimensional traceability and calibration of high-resolution microscopes. One such international comparison between 50 high-resolution atomic force microscopes from over 40 participants in 2020 revealed that only a few of the measurement results were within the given measurement uncertainty. In addition, many of the measurement devices were either insufficiently calibrated or not calibrated at all [1]. Under these conditions, the comparability of measurement results is not given and thus a sustainable obstacle to the development of nanotechnology. With the redefinition of the SI, the silicon lattice parameter is named in the mise en pratique as a secondary realization of the unit of length "meter" below 100 nm. In the PTB the production of crystalline standards has been systematically investigated and advanced in the past years. Within the framework of the JRP CRYSTAL, decisive preliminary work has been carried out, which represents a proof-of-principle for this innovative approach. Ultimately, a basis for the current mise-en-practique in this field. In the previously used UHV chamber, an electron beam was used to anneal a silicon chip prepatterned by electron beam lithography, resulting in atomically flat surfaces or monoatomic steps by self-assembly processes. Thus, the length measurement is reduced to a counting of lattice planes, which achieves the traceability to the lattice parameter. Improvements of more than one order of magnitude with respect to resolution and uncertainty of the standards have been approved. The fabrication process in the old UHV facility has several drawbacks for an industrial scale production: only a single sample could be fabricated per process with electron beam heating only from one side of the chip, and the size of the samples was limited by the design of the facility. Because of these limitations, the unit price per crystalline standard is high and scaling effects could not be used to reduce the price per sample. These limitations of the old UHV facility are addressed in a new facility, closing the gap between proof-of-principle and commercial application of this technology. In the new facility, the heat transfer is done via a direct current through the silicon sample. Up to 16 samples can be annealed in parallel and structured from both sides of the chip. For the realization, the sample holder was redesigned so that larger samples can also be processed. An extensive parameter study to optimize the heating process has now been completed. Initial challenges such as temperature control via the current intensity, superimposed by the strong temperature dependence of the conductivity of silicon, or a homogeneous temperature distribution in the sample, have been successfully solved. The heating process is optimized with respect to a high yield. As a result, the yield has been improved by 20%, so that the overall yield now reaches 80%. Further development includes the adaptation of the sample layout to achieve larger atomically flat areas of 0.01 cm² and more. In addition, the design is open, to couple additional modules, e.g., to combine DNA nano-origami with crystalline standards or analytic modules. Next steps are the increase of the structure sizes to dimensions between 30 and 70 nm. This can be achieved by combining crystalline standards with organic molecules for instance. Standards at this length scale are highly demanded for the calibration of microscopes, whose application ranges are at medium resolutions. Currently no cost-effective calibration standards are available (fit for purpose). With the prospect of more cost-effective crystalline standards fully utilizing the new SI, the comparability of measurements will be improved and thus the above-mentioned barrier to the further development of nanotechnology will be removed. |
