Applicability of e-beam mask inspection to EUV mask production

Ever since the 180nm technology node the semiconductor industry has been battling the sub-wavelength regime in optical lithography. During the same time development for a 13.5nm Extreme Ultraviolet [EUV] solution has been in development, which would take us back from a λ/10 to a >λ regime again - at least for one node. Add to this the potential to increase the wafer size as well, and we are at a major crossroads. The introduction of EUV has been marred by many delays, but we are finally seeing the hardware development efforts converge and multiple customers around the world embarking on this adventure. As it becomes clear that this preproduction phase will occur at or below 20nmHP, it also becomes clear that this will happen at the limiting edge of existing 19x-based patterned mask inspection technology, reaching the practical resolution limits at around 20nm HP mask densities. Resolution is coupled with sensitivity and throughput such that the extended sensitivity may come at an unreasonable throughput. Loss of resolution also badly impacts defect dispositioning, or classification, which becomes impractical. As resolution is especially critical for die to database inspection, single die masks and masks with high flare bias are at risk of not being inspectable with 19xnm based inspectors. E-Beam based mask inspection has been proposed and demonstrated as a viable technology for patterned EUV mask inspection. In this paper, we study the key questions of sensitivity and throughput, in both die-to-die and die-to-database applications. We present new results, based on a new generation of E-Beam inspection technology, which has a higher data rate at smaller spot sizes. We will demonstrate the feasibility of acceptable inspection time with EBMI. We also will discuss die-to-data-base inspection and the advantage of using E-Beam imaging for meeting future requirements of single- die EUV masks.