Scanning electron beam device with focus adjustment based on acceleration voltage and dimension measurement method using same

Abstract

A scanning electron beam device having: a deflector () for deflecting an electron beam () emitted from an electron source (); an objective lens () for causing the electron beam to converge; a retarding electrode; a stage () for placing a wafer (); and a controller (); wherein the stage can be raised and lowered. In the low acceleration voltage region, the controller performs rough adjustment and fine adjustment of the focus in relation to the variation in the height of the wafer using electromagnetic focusing performed through excitation current adjustment of the objective lens. In the high acceleration voltage region, the controller performs rough adjustment of the focus in relation to the variation in the height of the wafer by mechanical focusing performed through raising and lowering of the stage, and performs fine adjustment by electrostatic focusing performed through adjustment of the retarding voltage. It thereby becomes possible to provide a scanning electron beam device that measures, in a highly accurate manner, both the upper part and the bottom part of a groove or a hole having a high aspect ratio.