Method and system of sample edge detection and sample positioning for image inspection apparatus

A non-transitory computer-readable medium that stores a set of instructions that is executable by at least one processor of an apparatus to cause the apparatus to perform a method, the method comprising:

• causing the apparatus to obtain light reflected off a gap area formed between an outside edge of a sample held at an electrostatic holder and a structure of the electrostatic holder, wherein
• the gap area is coated with a first coating configured to reflect a first wavelength of light with first brightness, to reflect a second wavelength of the light with second brightness, and to reflect a third wavelength of the light with third brightness,
• the first wavelength is within a predetermined range of wavelengths,
• the second wavelength and the third wavelength are outside the predetermined range of wavelengths, and
• the first brightness is higher than the second brightness and the third brightness;
• causing the apparatus to image the light as a first image in a first color channel, a second image in a second color channel, and a third image in a third color channel, wherein a first wavelength of the light is imaged in the first color channel, a second wavelength of the light is imaged in the second color channel, and a third wavelength of the light is imaged in the third color channel;
• generating a synthesis image based on the first image, the second image, and the third image;
• and
• determining a location of the sample based on the synthesis image.

A system, comprising:

• an image inspection apparatus configured to scan a sample positioned on a sample holder and generate an image of the sample;
• an electrostatic holder configured to hold a sample and form a gap area between an outside edge of the sample and a structure of the electrostatic holder when the electrostatic holder holds the sample, wherein a surface of the gap area is applied with a mechanical milling process;
• a light source configured to direct the light at the gap area with a predetermined polarity;
• and an optical detector configured to image the light reflected off the gap area.