Proximity effect correction on the multi-level interconnect metal for the high-energy electron-beam lithography

In the application of the high-energy electron-beam (e-beam) lithography to the multi-level interconnect metal; the backscattered electron from the heavy metal previously patterned in lower levels on the substrate causes a significant proximity effect. We estimated the "inter-level" proximity effect in the e-beam exposure with the accelerating voltage of 50 kV on some multi-level interconnect metal structures which consist in aluminum wiring and tungsten plugs. It was found that the backscattering range and the backscattering energy ratio to the incident energy depend not only on the density and thickness of metal but also on the distance between the resist and the heavy metal plugs. In this paper, a novel proximity effect correction algorithm is proposed, where the exposing patterns are divided into some classes according to the metal structure, the total backscattering energy deposited in the resist is expressed by the sum of the backscattering energy from each structural class, and the exposure dose is modulated by the function of the total backscattering energy.