Accurate real-time landing angle and telecentricity measurement in lithographic systems

Abstract

Motion of a block carrying a grid for backscattering portions of a pattern of charged particles incident on the grid is moved generally axially of a charged particle beam tool while the position of the block is measured, preferably to optically, with a grazing incidence laser beam or interferometer, in the axial direction for any or all of the degrees of freedom of the block. Backscatter is correlated with known grid position to correct the backscatter measurement to compensate for lateral components of motion parallel to the target plane in measurement of actual beam position at different axial locations. Telecentricity and landing angle can thus be observed to an accuracy of 0.003 milliradians in substantially real time; permitting substantially real time adjustment thereof. The basic principles of this process and apparatus can be extended to measurement of numerical aperture and are equally applicable to probe-forming and beam projection lithography tools.

Dependencies are inferred from the claim text.