Sample inspection apparatus

A sample inspection apparatus comprising:

• a charged particle optical system configured to irradiate a sample with a charged particle beam;
• a first probe configured to come into contact with the sample;
• an amplifier having an input terminal to which the first probe is connected;
• a frequency generator configured to generate a reference signal;
• a phase detection unit configured to detect an output signal of the amplifier using the reference signal generated by the frequency generator;
• a system control unit;
• a charged particle control unit configured to control the charged particle optical system;
• and
• an image processing unit configured to form an image from an output signal input from the phase detection unit,
• wherein the system control unit outputs a scanning signal that causes the charged particle control unit to scan the sample with the charged particle beam,
• the image processing unit forms the image by calculating a gray value per pixel from a detection signal input from the phase detection unit based on a control signal input from the system control unit in synchronization with the scanning signal, and
• the system control unit sets a frequency of the reference signal generated by the frequency generator to a value higher than or equal to a sampling rate that is a reciprocal of an electron beam irradiation time per pixel of the image.