Multi charged particle beam inspection apparatus, and multi charged particle beam inspection method

A multi charged particle beam inspection method comprising:

• performing an acquisition operation of a secondary electron image which includes a reflected electron emitted from a substrate due to irradiation with multiple charged particle beams on the substrate;
• measuring a plurality of interfering factors inside or on a periphery of a secondary electron image acquisition mechanism;
• determining, for each of the plurality of interfering factors, in a case where change exceeding a corresponding threshold occurs in at least one of the plurality of interfering factors, whether the change is a first case which returns to an original state within a predetermined time period, or a second case which does not return to the original state even if the predetermined time period has passed;
• suspending the acquisition operation of the secondary electron image when the change of the interfering factor exceeds the corresponding threshold;
• in a case where change of the second case occurs, calibrating a change amount of the multiple charged particle beams, and restarting the acquisition operation of the secondary electron image after the calibrating, from a restart position which is previous, by the sampling period, to a position where the acquisition operation of the secondary electron image was suspended;
• and
• in a case where change of the first case occurs, restarting the acquisition operation of the secondary electron image after the predetermined time period has passed, from a restart position which is previous, by the sampling period, to a position where the acquisition operation of the secondary electron image was suspended, without calibrating a change amount of the multiple charged particle beams.

A multi charged particle beam inspection apparatus comprising:

• a secondary electron image acquisition mechanism configured to perform an acquisition operation of a secondary electron image of a secondary electron including a reflected electron emitted from a substrate due to irradiation with multiple charged particle beams on the substrate;
• an interference circuit configured to calculate a change amount of an interfering factor based on input from at least one sensor, detect the change amount of the interfering factor exceeding a threshold, and determine whether the change of the interfering factor exceeding the threshold is a first case in which the change of the interfering factor returns to an original state which is lower than the threshold within a predetermined time period, or a second case in which the change of the interfering factor does not return to the original state even if the predetermined time period has passed;
• and
• a comparison circuit configured to compare the secondary electron image acquired and a reference image of a region corresponding to the secondary electron image acquired,
• wherein the secondary electron image acquisition mechanism is configured to suspend the acquisition operation of the secondary electron image when the interference circuit detects that the change amount of the interfering factor exceeds the threshold,
• the secondary electron image acquisition mechanism is configured to, in a case where the first case occurs, restart the acquisition operation of the secondary electron image after the predetermined time period has passed, from a restart position on the substrate which is previous to a position where the change amount of the interfering factor exceeding the threshold was detected by the interference circuit, without calibrating a change amount of the multiple charged particle beams, and
• the secondary electron image acquisition mechanism is configured to, in a case where change of the second case occurs, calibrate a change amount of the multiple charged particle beams, and restart the acquisition operation of the secondary electron image after the calibration, from a restart position on the substrate which is previous to a position where the interfering factor exceeding the threshold was detected by the interference circuit.