Silicon grid as a reference and calibration standard in a particle beam

Abstract

A reference and calibration grid (44a or 44b) of silicon is incorporated into a particle beam lithography system (10) and used to calibrate the system (10). The grid (44a or 44b) is formed in a silicon die (50) of much thicker structure and with square holes (64) and with a period to enable direct coordination with binary electronics. The grid (44a or 44b) is coated with a suitable material, preferably gold (72), to prevent charged particles or electrons from passing through the solid portions of the grid and the grid is preferably mounted on a grid holder (52) which can be aligned to the X-Y reference on the workpiece stage (32) and may be adjusted in tilt and in height (Z direction). The crystallography of silicon provides accuracies in orthogonality, corner radii, and edge roughness required for grids used as fiducials for particle beam lithography. In addition, as part of a thicker structure (silicon die 50), the grid (44a or 44 b) can easily be handled and hence mounting and alignment procedures can be markedly simplified. The flatness of the grid (44a or 44b) is consistent over the whole surface.