Wafer heating analysis for electron-beam projection lithography

Electron projection lithography (EPL) is one of the principal next-generation lithography technologies for the sub-65 nm regime. To satisfy the stringent resolution requirements, all image placement errors must be characterized and minimized. These include the distortions of the device wafer during exposure. The wafer absorbs beam energy which produces temperature increases and thermomechanical strains that directly contribute to pattern-placement errors, stitching errors between adjacent subfields, and image blur. Thus, CD control and pattern overlay will be directly affected. In this article, the thermomechanical distortions caused by wafer heating in the EPL system have been simulated using finite element models that include the effects of the interaction between the wafer and chuck.