Method for optically inspecting a wafer by sequentially illuminating with bright and dark field light beams wherein the images from the bright and dark field illuminated regions are spatially offset

A method for optically inspecting a surface of a wafer comprising the steps of:

• illuminating a region on the surface of the wafer with at least one first incident illuminating light beam for a bright-field illumination, the at least one first incident illuminating light beam being provided by a first incident illumination device in a bright-field configuration;
• illuminating another region on the surface of the wafer with at least one second incident illuminating light beam for a dark-field illumination, the at least one second incident illuminating light beam being provided by a second incident illumination device in a dark -field configuration;
• sequentially scanning the at least one first and the at least one second incident illuminating light beams over the surface of the wafer with a relative movement of the wafer with respect to the first and the second incident illuminating light beams;
• and
• acquiring a plurality of images of illuminated regions in a bright-field configuration and acquiring a plurality of images of the illuminated regions in a dark-field configuration;
• wherein the images of the illuminated regions in the dark-field configuration have a spatial offset from the images of the illuminated regions in the bright-field configuration;
• and
• wherein the relative movement of the wafer with respect to the at least one first and the at least one second incident illuminating light beams is performed by at least one of the group consisting of:
• deflecting at least one of the at least one first and at least one second incident illuminating light beams, and moving the wafer,
• wherein illuminating the regions on the surface of the wafer with the at least one first and at least one second incident illuminating light beams is performed asynchronously or simultaneously.