Electrostatic lens array

A charged particle optical system comprising:

• a collimator lens configured to collimate a charged particle beam emitted from a charged particle source;
• an aperture array configured to divide the collimated charged particle beam;
• and
• an electrostatic lens array configured to focus each of the divided charged particle beams so as to irradiate a sample surface,
• wherein the electrostatic lens array includes multiple substrates spaced from each other by intervals, each of the multiple substrates having an aperture for passing therethrough the charged particle beam,
• wherein with respect to a travelling direction of the charged particle beam, a peripheral contour line formed by any one of surfaces of the multiple substrates other than an upper surface of a most upstream substrate and a lower surface of a most downstream substrate has a protruding portion protruding from a peripheral contour line of both of the upper surface of the most upstream substrate and the lower surface of the most downstream substrate;
• wherein a position of the protruding portion is defined by a position regulating member, whereby parallelism is adjustable so that a surface including the protruding portion is parallel to a surface to be irradiated with the charged particle beam after passing through the aperture, and
• wherein the position regulating member is in contact with the protruding portion.

An electrostatic lens array comprising:

• multiple substrates including at least first and second substrates;
• and
• a spacer contacting a lower surface of the first substrate and an upper surface of the second substrate to space to the first and second substrates from each other, each of the multiple substrates having an aperture for passing therethrough a charged particle beam,
• wherein with respect to a travelling direction of the charged particle beam, the spacer has a protruding portion protruding from a peripheral contour line of one of the upper surface of the most upstream substrate and the lower surface of the most downstream substrate,
• wherein a position of the protruding portion is defined by a position regulating member, whereby parallelism is adjustable so that a surface including the protruding portion is parallel to a surface to be irradiated with the charged particle beam after passing through the aperture, and
• wherein the position regulating member is in contact with the protruding portion.