Patent ID: 7982188

Claim:
A sample inspection apparatus for inspecting a wafer carrying an insulator on a surface of the wafer, the apparatus comprising: a sample stage to hold a sample to be inspected; a first electron optical system to direct to the sample an area electron beam that is formed to spread over a two-dimensional area of the sample; means for applying a voltage to the sample thus forming a surface potential on the sample to reflect the directed area electron beam without reaching to the sample; an image detection unit to detect the reflected area electron beam and to form a first image according to a potential distribution of the sample; an image processing unit to detect a defect existing in the first sample by analyzing information of the potential distribution based on the obtained first image, and to record a position of the defect; a second electron optical system to obtain a scanning electron microscopic (SEM) image by irradiating the recorded position of the defect with an electron probe beam configured to scan the sample with respect to the recorded position of the defect and detecting a secondary generated charged particle; and a pre-charge control unit for controlling a charged state of the sample prior to the first image being formed, wherein said charged state of the sample is controlled to reflect a potential distortion between a potential at a normal portion in the sample and a potential at a faulty portion in the sample, and wherein said pre-charge control unit includes an electron gun to irradiate an electron beam along an optical axis separated from respective optical axes of said first and said second electron optical systems to the sample, and a grid arranged between the electron gun and the sample to control said charged state of the sample due to the voltage applied to the grid.