Process improvement of high aspect ratio nano-gratings based on synchrotron x-ray

Abstract

To achieve better structural accuracy and aspect ratio, nano-gratings with a vertical angle close to 90° and a depth-to-width ratio of about 8 were prepared by synchrotron radiation. The optimal exposure dose and development time were determined to be 0.006 (A‧h) and 6 min, respectively, by observing the surface loss and roughness of the grating at 150 nm and 250 nm under different conditions. To obtain the desired rectangular grating structure, the experimental conditions were optimized with the help of controlled variables experimental method. With the mask-to-photoresist pitch and the development and drying temperatures of 20 μm and 23 °C, the optimized depth-to-width ratio of the nano-gratings with a line width of 250 nm can reach 8.28. The cone angle can reach 88.4°. The aspect ratio of the nano-gratings with a line width of 150 nm is 7.18, and its cone angle is 87.1°.