Ultra precision multi-axes heterodyne interferometers for picometer level accuracy

• Applicant: Dr. Jens Flügge
• Subject Area: Measurement Systems
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 449485254

High-resolution interferometry is a key component of high-precision production metrology, lithography for semiconductor devices and nanotechnology, and is also of great importance for scientific questions. Due to increasing accuracy requirements, interferometers with measurement uncertainties in the sub-angstrom range are needed. In order to achieve these accuracies, secondary effects, such as angular movements of traversing units in the range of nanoradians, must also be recorded. For the optimization of the interferometers and for the determination of the performance of the systems themselves, suitable measuring equipment is required, which, for lack of alternatives, must be equipped with high-precision multi-axis interferometers. Since the determination of the measurement uncertainties is very complex, SI traceable measurements are very challenging, but will be essential in the future. For this reason, HIT with its long-standing expertise in high-resolution interferometry and PTB as the world's leading institute in the field of traceability of dimensional measurands plan to use this cooperation project to develop both improved interferometers and a test platform to reliably prove the performance of high-resolution interferometers. For the improvement of multi-axis interferometers, both theoretical and experimental work has to be carried out. The focus will be on interpolation nonlinearities, thermal stability and assembly techniques to reduce alignment tolerances. In order to be able to verify the theoretical findings, a test platform existing at PTB with a displacement unit in vacuum will be further developed. An existing interferometer for length measurement has to be extended by additional angular axes and, in order to achieve a low sensitivity to tolerances when mounting test objects, the movement of the displacement unit has to be precisely controlled with these measurement possibilities. Furthermore, the entire vacuum chamber is tempered in order to create ideal conditions for investigations and comparison measurements as well as to be able to prove thermal sensitivities.All in all, it will be possible for the first time to compare high-resolution interferometers at this level of uncertainty, and thus to place measurement uncertainty estimates on a more reliable basis. The different and partly complementary approaches of both partners offer an excellent opportunity to identify and eliminate possible systematic sources of error. The project will benefit from the world-leading expertise of both partners, which is to a certain extent complementary, and will generate synergies accordingly. This will be further developed through regular extensive mutual research visits and regular scientific exchange (online and offline).

• DFG Programme: Research Grants
• International Connection: China
• Partner Organisation: National Natural Science Foundation of China
• Cooperation Partner: Professor Dr. Pengcheng Hu