J. Eur. Opt. Society-Rapid Publ. 22, 9( 2026) 95
( AZ MIR 701 from MicroChemicals) with thickness d = 195 nm. With a scanning electron microscope and an atom force microscope, the grating period was determined to p = 270 nm(± 2 nm)( see Figs. 15 and 16). The grating depth was determined to around h = 192nm.
5 Conclusion
A new fringe stabilization system for an SBIL system was presented. Using polarization camera-based real-time interferometry, the phase shift and the orientation of the two exposure beams are recorded with a separate measuring beam. This allows the lateral fringe movement and the orientation of the fringe pattern in the substrate plane to be precisely determined. A fringe observation system was implemented, which was placed in the substrate plane. Due to the high positioning accuracy of the nano positioning and measuring machine NPMM-200, the movement of the fringe pattern is precisely measured. Without fringe locking, the fringes moved a few tens of nanometers due to air turbulence and the dose contrast loss was 7.4 %. Our results demonstrate that activation of the fringe locking system effectively reduced fringe displacement to ± 5 nm. This improves the wavefront error in the reconstruction to less than k and reduces the contrast loss to
25
1.2 %. It should be noted that these values were detemined for p = 270 nm and scale with the grating period. For larger periods, the expected improvements are even better. Furthermore, the fringe locking system was also used to determine the fringe rotation in situ in the substrate plane. A rotation test demonstrated highly precise sensitivity in the millidegree range. Finally, structures were fabricated in photoresist with a period of approx. 270 nm and a grating depth of 192 nm. Improvements to this system are planned for future work. The measurements with the fringe observation system have shown that the camera heat influences the phase fluctuations and thus the fringe stabilization. A cooling system is therefore planned to minimize the disturbance and achieve fringe stability in the subnanometer range. In addition, the mirrors can be equipped with piezo actuators to compensate for fringe rotation or to compensate for rotary stage errors.
Funding
The FIB-SEM FEI Helios NanoLab 600 was funded by the Deutsche Forschungsgemeinschaft( DFG, German Research Foundation) – 154585072. The nano positioning and measuring machine NPMM-200 was funded by the Deutsche Forschungsgemeinschaft( DFG, German Research Foundation) – 267094782 Funding This work was supported by German Research Foundation( Deutsche Forschungsgemeinschaft, DFG), grant no. 465642714.
Conflicts of interest
The authors declare that they have no competing interests to report.
Data availability statement
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
Author contribution statement
Conceptualization K. T., J. R., H. W., I. O., C. P., C. S. T. H., O. S., E. M., T. K. and S. R.; Methodology C. P., C. S., T. H., O. S., E. M., T. K. andS. R.; Software, K. T., H. W., C. S. andJ. R.; InvestigationK. T., J. R., H. W. and C. P.; Writing – Original Draft Preparation K. T.; Writing – Review Editing K. T., J. R., C. P. I. O., T. H., O. S., E. M., T. K. and and S. R.; Project administration T. H., O. S., E. M., T. K. and S. R.; Funding acquisition T. H., O. S., E. M.
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