Electron beam and scanning probe lithography: A comparison

Abstract

Electron beam lithography (EBL) and scanning probe lithography (SPL) are electron exposure techniques capable of high resolution patterning of organic resists. This article compares the exposure properties of these two systems. We consider the resist sensitivity to EBL and SPL electrons, exposure tolerances, patterning linearity, and proximity effects. It is possible to print sub-50 nm features using both systems, but SPL has a wider exposure latitude at these small feature sizes. SPL requires a significantly higher incident electron dose for exposure than does EBL. In EBL, lithography control is most limited by proximity effects which arise from backscattered electrons whose range is considerably larger than the forward scattering range in the resist film. As a result, the exposed feature dimension depends strongly on the local feature density and size, leading to unacceptable linewidth variations across a wafer. These limitations are alleviated in the case of SPL exposures. We demonstrate improved linearity and reduced proximity effects with SPL. We have patterned 200 nm pitch grids with SPL where all individual features are resolved. The linewidth of features in these grids is the same as the width of an isolated line at the same dose. Finally, we suggest that the SPL exposure mechanism may be different than that for EBL.