Scanning beam interference lithography for spatial structures

• Applicants: Dr. Tobias Haist; Professor Dr.-Ing. Eberhard Manske; Professor Dr.-Ing. Oliver Sawodny
• Subject Area: Measurement Systems ; Automation, Mechatronics, Control Systems, Intelligent Technical Systems, Robotics
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 465642714

The main objective of the joint research project is to develop and investigate methods for the efficient fabrication of large, high-quality grating structures for optical applications. As a patterning technique, scanning beam interference lithography (SBIL), which is well established for planar gratings, will be extended to the spatial problem. 3D-SBIL requires precision positioning of the pose of the write point of an optical print head to be designed with respect to the substrate with uncertainties in the low single-digit nanometer range.In order to achieve the highest measurement accuracy in the Cartesian 3D volume, the nanopositioning and nanomeasuring machines (NPMM) developed and built at the TU Ilmenau follow the approach of the "scanning stage" principle and thus the consistent adherence to the Abbe comparator principle in all three coordinate axes. Path deviations of the measuring stage in six degrees of freedom are detected by measurement and compensated by control. To enable scanning interference lithography on spatial structures with the required accuracy, additional axes of motion are required in the writing head. With these additional axes the same approach is consequently pursued to realize an intelligent measurement and control driven nanofabrication of complex nanostructures. Instead of compensating for the numerous additional degrees of freedom, the combined uncertainty in the write point is to be measured with an optical feedback system and compensated with an overall control system. Therefore, the new approach is to implement the additional motion axes (rotate, pan, rotate) through the lithography writing tool while simultaneously moving the stage in three dimensions. Here, the said movements can be performed by relatively small optics with high dynamics. However, simple cascading of the axes without further measures would greatly increase the positioning uncertainty. Synchronization between tool and stage movement, again with the nanometer requirement, is therefore essential.In order to achieve the main goal of a 3D-SBIL, approaches for a writing head are to be investigated, which is capable of maintaining the required accuracies in all required spatial degrees of freedom. The optical concept must be closely coordinated with the overall metrological and control concept. Specifically, the writing head is to generate a spatially limited, interference lithographically structured exposure area with degrees of freedom in the position, period and orientation of the interference fringes, the metrological registration of the interference fringes to the substrate and the already written areas is to be investigated, and finally the necessary 3D trajectories of the writing point with respect to the substrate with position uncertainties in the low single-digit nanometer range are to be realized in terms of control technology.

• DFG Programme: Research Grants