A New Approach of E-beam Proximity Effect Correction for High-Resolution Applications

Abstract

The e-beam proximity effect is well known as one of the limiting factors in e-beam lithography. As features get smaller the need for e-beam proximity effect correction (EPC) increases. There exist different approaches to cover these effects by varying dose or shape of the pattern layout during the exposure step. Both of these basic approaches have drawbacks limiting their application. For example, the EPC correction by shape variation underlies constraints such as neighbouring features, the exposure grid of the e-beam tool and writing time. EPC by dose variation fails in cases the feature size is very close to the process dependent forward scattering parameter alpha. To guarantee CD uniformity in these cases a negative dose assignment would be necessary, which is practically impossible. The paper presents a new correction scheme based on dose assignment and geometry variation at the same time. After a short introduction the theoretical description of the method is given. Dose and geometry modifications are calculated using a Fast Fourier Algorithm. Due to the ability of changing the geometry depending on feature size and feature neighbourhood even very small features can be printed correctly. This flexibility is the main advantage compared to already existing methods. Pattern fidelity and linearity can be improved drastically. Resolution limits can be pushed further down. The application of the automatic correction to high resolution features with a feature size of 100 nm are demonstrated. The CD linearity is investigated and demonstrated using a real device patterns.