Multiple material stack grayscale patterning using electron-beam lithography and a single plasma etching step

In this paper, we present a novel method to perform grayscale electron-beam lithography on multilayer stacks where the pattern transfer is done in a single plasma etching step. Due to the differences in material etch rates in the stack, the shape of the resist after development vs the shape of the multilayer stack after etching is significantly different. To be able to reach the desired shape in the multilayer stack, the final resist dose is defined by an etching calibration curve that describes the relationship between the electron-beam dose and the remaining materials thickness after plasma etching. With this method, a resistive memory crossbar array is fabricated with a height resolution of 10 nm and nanoscale dimension devices.