Accurate measurement and adjustment method for interference fringe direction in a scanning beam interference lithography system

To improve the exposure contrast of the scanning beam interference lithography (SBIL) system, a mathematical model of scanning exposure that includes the direction error of the measurement mirror is established. The effect of the angle between the interference fringe direction and the X-axis measurement mirror direction on the exposure contrast is analyzed. An accurate method for interference fringe direction measurement based on the heterodyne interferometry measurement method of the metrology grating and phase shift interferometry is proposed. This method combines the diffraction characteristics of the metrology grating and the phase shift algorithm to calculate the angle between the interference fringe direction and the measurement mirror direction accurately and adjust it. Experiments show that this angle reaches 0.6777 grad, which meets high-precision grating fabrication requirements. Exposure comparison experiments performed at various angles show that a smaller angle between the interference fringe direction and the measurement mirror direction leads to better grating groove production by scanning exposure, which is consistent with the theoretical analysis. The accuracy of the theoretical analysis and the feasibility of the interference fringe direction adjustment method are verified, laying a foundation for high-quality grating fabrication by the SBIL system.& COPY; 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

In order to improve the exposure contrast of the scanning beam interference lithography (SBIL) system, a mathematical model is established to analyze the effect of the direction error of the measurement mirror on the exposure contrast. An accurate method for interference fringe direction measurement is proposed, which combines the diffraction characteristics of the metrology grating and the phase shift algorithm. Experiments show that the smaller the angle between the interference fringe direction and the measurement mirror direction, the better the grating groove production by scanning exposure.