Pattern transfer into silicon using sub-10 nm masks made by Electron Beam Induced Deposition

To demonstrate the possibility of using EBID masks for sub-10 nm pattern transfer into silicon, first experiments were carried out by using 20-40 nm EBID masks, that were etched by different chemistries. It is experimentally verified that recipes based on hydrogen bromide, chlorine and boron trichloride can selectively etch silicon when using 20-40 nm masks made by EBID. We observed an enhancement of the height ratio, i.e. the ratio of the height of structures before and after etching, up to a factor of 3.5 when using the chlorine chemistry. To demonstrate the pattern transfer of sub-10 nm structures, further experiments were carried out using 8-20 nm EBID masks in combination with hydrogen bromide, chlorine and fluorine chemistries. Fluorine chemistry provided the best results in terms of surface smoothness and height ratio. In this case, 7.4 nm lines were successfully transferred into silicon, resulting in 14.3 nm wide lines with a height ratio of approximately 5.