Process development for manufacturing blazed gratings using grayscale lithography

Inhalt:
Despite the challenge of precisely adjusting the blaze angle, blazed gratings offer superior diffraction efficiency, adaptability, and optical performance compared to binary diffraction gratings. Traditional manufacturing methods struggle to meet modern demands for finer grating periods, the use of diverse materials and structural fidelity. Grayscale laser lithography is a promising solution that balances time efficiency and precision. This paper discusses optimising the coating system for grayscale lithography to achieve homogeneous coatings of up to 220 nm thickness. Increases to the thermal energy applied to the photoresist introduces inhomogeneities, but grayscale lithography is reliable for resist layers around 500 nm thick. Reactive ion beam etching enables structure transfer to silicon substrates and the achievement of grating geometries with 3 µm line spacing and heights of 240–320 nm.