Dark-field optical inspection device

A device for dark-field optical inspection of a substrate, such as a wafer for electronics, optics, or electronics, the device comprising:

• a light source for generating at least one incident illuminating beam that is projected onto an inspection zone of the substrate and is capable of being reflected therein in the form of diffuse radiation;
• at least one first and one second collecting device having a sensing surface for capturing at least a portion of the diffuse radiation and transmitting it to an analysis device, the analysis device configured to measure at least one of an intensity, a spectral content, and a polarization of the diffuse radiation that is captured and to derive therefrom analysis quantities;
• and
• a reflecting optical device comprising a first reflecting optical part and second reflecting optical part, the reflecting optical device having a reflective surface that is designed to direct at least a portion of the diffuse radiation originating from an optical focal point of collection that is coincident with the inspection zone in the direction of the collecting devices;
• wherein the reflective surface of the reflecting optical device comprises a first reflective zone made on the first optical part and onto which a first portion of the diffuse radiation is reflected toward a first optical focal point of detection that is optically conjugated with the optical focal point of collection, and a second reflective zone made on the second reflecting optical part and onto which a second portion of the diffuse radiation is reflected toward a second optical focal point of detection that is optically conjugated with the optical focal point of collection and distinct from the first optical focal point of detection;
• wherein the first and the second collecting device are, respectively, arranged in the inspection device in order to capture the diffuse radiation at the first and the second optical focal point of detection of the reflecting optical device;
• and
• wherein the first and the second reflective zones correspond to portions of distinct ellipses whose respective main axes form a non-zero angle between them, a first focal point of the ellipses corresponding to the optical focal point of collection, and a second focal point of the ellipses corresponding, respectively, to the first optical focal point of detection and to the second optical focal point of detection of the reflecting optical device.