Extreme-ultraviolet-lithography line-space patterning defect detection using voltage contrast SEM

This paper introduces an innovative method for detecting defects in the line-space (LS) patterns, which we refer to as voltage contrast (VC) scanning electron microscope (SEM) pad inspection. This detection technique involves a single-layer meander (MR) and fork-fork (F-F) design, where one terminal of the MR/F-F is connected to a conductive film and the other to a small pad. Ideally, if a defect occurs within the LS of the MR/F-F structures, the contrast of the pad in the VC SEM image will change. As a result, defects can be efficiently detected by analysing the grayscale of the pad. To demonstrate LS patterning defect detection using the VC SEM pad technique, we designed various lengths of MR and F-F structures featuring a pitch of 40 nm. The design also included programmed defect (PD). We employed e-beam lithography to create patterns on the photoresist, followed by an etching process to transfer the patterns onto a Ru and a TiN film. The VC SEM image of the MR pad shows dark contrast when MR has a break PD, while the one without a defect appears bright. In contrast, the pad connected to the F-F with a bridge PD shows a bright contrast, while the F-F without a defect appears dark. This observation confirms that this defect detection approach will allow for an efficient and rapid detection of extreme ultraviolet lithography (EUVL) LS patterning defects.