Uniform fabrication method for large area nanostructure gratings by suppressing scanning etching periodic errors based on frequency domain analysis

Large area nanostructures (diameters above 200 mm) are widely used in various fields for manufacturing high-end products, such as diffraction gratings, VLSI (Very Large Scale Integrated Circuit) manufacturing, and wafer etching.However, the commonly used large-diameter RIE (Reactive Ion Etching) method is expensive and prone to lateral etching, and it is difficult to achieve uniform plasma distribution in large diameter discharge chambers, leading to depth errors of nanostructure. Therefore, grating scanning RIBE (reactive ion beam etching) is often used for large area nanostructures manufacturing.Under the background, we based on the RIBE technology, and aim at the key problem that the periodic error is difficult to suppress during grating scanning, and put forward a periodic error suppression method based on ion source working temperature control and etching depth error frequency domain analysis.Firstly, the ion source water cooling structure is added, and the temperature of the ion source during the etching process for 4 h is reduced from 130.7 °C to 54.1 °C, which effectively avoids the fluctuation of etching efficiency caused by heat radiation on the nanostructure surface.Secondly, under the reactive discharge condition of CHF3, the removal function of the fused silica was measured and calculated through laser wavefront interferometer. In order to facilitate subsequent calculation, the Gaussian function is used to fit it. Combined with Fourier transform and convolution theory, the frequency spectrum information of the Gaussian function and scanning path is obtained, that is, the PSD (Power Spectral Density) spectrum of error distribution.On the PSD spectrum, the error frequency information is analyzed comprehensively, and the line feed frequency with the smallest error amplitude is selected as 0.35 Hz, and the scanning etching line spacing parameter is determined as 2.85 mm. Under this scanning parameter, the uniform etching of 300 × 300 mm nanostructure grating is realized, and the uniformity is 5.3 %.The research in this paper provides support for the industrial-scale implementation of reactive ion beam etching processes for large area nanostructures based on the suppression method of periodic errors in scanning based on frequency domain analysis.