Approaches to modulating stochastic effects in EUV lithography (Conference Presentation)

Stochastic effects are a major concern for yield enablement as we look towards extending the use of single-expose EUV lithography in both trench and via levels. For example, in trench levels stochastic effects lead to two competing defect modes: line breaks and microbridges, both of which are highly CD-dependent and lead to patterning cliffs that narrow the process window as the pitch decreases. In order to push the limits of effective pitch resolution, a fundamental understanding of the patterning process space is required, including imaging and mask contributions, material contributions, as well as develop, and etch contributions. In this paper we will discuss several strategies to modulate and gain fundamental understanding of stochastic effects. In term of the illumination contribution, recently Burkhardt et al. investigated phase effect in EUV through simulation, demonstrating that the images shift caused by a focus shift in monopole illumination can be used to make split images overlap, thus enhancing the contrast in a dipole. We will show that this approach can be used to modulate stochastic effects, specifically defectivity and line edge roughness, and directly correlate these modulations to electrical yield detractors. We will also discuss alternate approaches to understand interfacial effects between the resist and underlying substrate that can impact stochastic defectivity.