Reducing line edge roughness of laser heat-mode direct writing lithography using AOD scanning method

Line edge roughness (LER) is a critical parameter for evaluating the quality of micro-nano structure patterns. This paper proposes a method based on small pixel spacing exposure to reduce LER in laser heat-mode lithography. The simulation indicates that the reduction of LER can be achieved through smaller writing pixel spacing. Specifically, when the pixel spacing is reduced from 100 nm to 10 nm, the LER decreases by approximately 6 nm. To implement this, a laser heat-mode lithography system was developed with an acousto-optic deflector (AOD) as the light beam scanning element due to its high scanning accuracy, which enables pixel spacing as small as 6 nm. Additionally, to ensure pattern uniformity in the writing process, the compensation for AOD diffraction efficiency was first addressed. The variation in AOD diffraction efficiency is reduced from 63.94 % to 7.37 %. The experimental results show that LER can be effectively reduced from 14.58 nm to 9.34 nm when the pixel spacing reduces from 90 nm to 6 nm. The writing of arbitrary patterns validates the effectiveness of the method. This work provides an effective method for reducing LER in laser heat-mode direct writing lithography, paving the way for high quality pattern fabrication.