Abstract: The invention is to observe semiconductor wafers with higher resolution at a low acceleration voltage—in particular, achieving such high-resolution observability when a wafer is inclined or tilted at large angles. A composite lens is used which consists essentially of a single-pole or monopole magnetic field type lens and an electrostatic field invasive lens whereas an electrode of the electrostatic field invasive lens which opposes the wafer is made of a magnetic material while letting a high voltage of the negative polarity be applied to this electrode and the wafer. Even when the wafer is tilted, any astigmatism and axis failure will hardly occur.

Abstract: The invention is to observe semiconductor wafers with higher resolution at a low acceleration voltage—in particular, achieving such high-resolution observability when a wafer is inclined or tilted at large angles. A composite lens is used which consists essentially of a single-pole or monopole magnetic field type lens and an electrostatic field invasive lens whereas an electrode of the electrostatic field invasive lens which opposes the wafer is made of a magnetic material while letting a high voltage of the negative polarity be applied to this electrode and the wafer. Even when the wafer is tilted, any astigmatism and axis failure will hardly occur.