An image fidelity approach to measuring the point spread function in electron and ion beam lithographies

Abstract

In electron and ion beam direct write lithographies, the fidelity of a pattern is degraded by beam spreading and electron or ion interactions in the resist and substrate materials. This pattern degradation will lead to errors in pattern linewidths and possibly the blending together of closely spaced features. This is the proximity effect in electron beam lithography. Implicit in the beam spreading compensation process is the detailed knowledge and measurement of the beam point spread function. The successful lithographic reproduction of arbitrary patterns with critical dimensions necessitates a measurement of the point spread function to at least that dimension. The degree of compensation or correction that can be achieved depends directly upon the accuracy of the point spread function available. This paper will present experimental measurements of the point spread function using an image fidelity approach. These measurements are based on the extremely accurate transform based proximity correction methodology reported previously [1, 2, 3].