Measurement system

A measurement system for measuring a surface structure of a sample, a surface of the sample having a via, and the measurement system comprising:

• a light source, for generating incident light, a cross section of the incident light covering an opening of the via;
• a first light splitter, disposed in a light emitting direction of the light source and configured to reflect the incident light to form first reflected light;
• a first aperture stop, disposed between the light source and the first light splitter, a size of the first aperture stop being adjustable and configured to adjust a size of the cross section of the incident light, the first aperture stop and the first light splitter being a first default distance apart;
• an lens assembly, disposed between the first light splitter and the sample and configured to guide the first reflected light to the sample to form second reflected light, the lens assembly having a focal length reference point, the focal length reference point and the sample being a default object distance apart, the focal length reference point and the first light splitter being a second default distance apart;
• a second aperture stop, disposed between the lens assembly and the first light splitter, a size of the second aperture stop being adjustable to filter the second reflected light, the second aperture stop and a back focal plane of the lens assembly being a third default distance apart;
• a spectrum analyzer, disposed at a side of the first light splitter opposite to the sample, the spectrum analyzer and the first light splitter being a fourth default distance apart, the filtered second reflected light passing through the first light splitter and being received by the spectrum analyzer, the spectrum analyzer forming an optical spectrum according to the received second reflected light;
• and
• a computer, electrically connected to the spectrum analyzer and configured to separate the optical spectrum into a high frequency spectrum and a low frequency spectrum, and determine a depth of the via according to the high frequency spectrum;
• wherein the first default distance is substantially equal to the fourth default distance, a sum of the second default distance and the fourth default distance is substantially equal to an image distance of the lens assembly.