Decoupled control of a 5-DOF writing head for Scanning Beam Interference Lithography on 3D topographies

Scanning Beam Interference Lithography (SBIL) is an established technique for fabricating large-area, high-fidelity diffraction gratings. However, conventional implementations are generally restricted to planar or simple rotationally symmetric substrates. This work introduces a generalized 3D SBIL system capable of patterning gratings on complex non-planar topographies. The proposed architecture integrates a large range nano-positioning stage with a novel writing head featuring active tip, tilt, and rotation control. To manage the kinematic complexity, a geometric ray-tracing model is derived, and a decoupled control strategy is implemented to synchronize the substrate trajectory with the optical interference pattern. Experimental validation, performed using a custom fringe observation system, demonstrates the system’s capability to maintain phase coherence during complex multi-axis motion. The proposed control architecture achieves a phase tracking error of 2.35 nm (RMSE), enabling the successful generation of linear and circular gratings.