EUV blank defect and particle inspection with high throughput immersion AFM with 1nm 3D resolution

Abstract

Inspection of EUV mask substrates and blanks is demanding. We envision this is a good target application for massively parallel Atomic Force Microscopy (AFM). We envision to do a full surface characterization of EUV masks with AFM enabling 1nm true 3D resolution over the entire surface. The limiting factor to do this is in the sensor itself: throughput is limited by the time that a cantilever needs to adjust its oscillation amplitude to the surface topography while scanning. We propose to use heavily damped cantilevers to maximize the measurement bandwidth. We show that using up to 20.000 cantilevers in parallel we can then reach a throughput of one 152×152mm2 substrate per 2 days with 1nm resolution.