A Comparative Study of Depth of Focus in Multi-Beam Interference Lithography Systems

This chapter examines and compares the depth of focus (DOF) across laser interference lithography (LIL) systems with two, three, four, and five beams. DOF is an important parameter in photolithography, affecting pattern accuracy and tolerance within the process. It is analyzed as a function of laser wavelength, slit separation, beam number, and interference angles. A mathematical expression for DOF is provided, and MATLAB simulations are used to derive results, offering an in-depth analysis of how the beam count influences DOF. The study shows that increasing the number of beams enhances pattern detail, yielding finer interference patterns, though it also reduces DOF, making the system more sensitive to defocusing. The work’s novelty lies in systematically illustrating the balance between pattern complexity and focus tolerance with increasing beam count. Multi-beam interference lithography presents an effective method and makes it ideal for creating high-resolution, periodic micro- and nanostructures suitable for biomedical and nanotechnology applications.