Semiconductor wafer inspection system and method

摘要

A wafer inspection system comprises a camera having a field of view, an object mount configured to position at least a portion of surface 5 of an object 3 at an object plane 15 relative to the camera and within the field of view of the camera and at least one surface portion 41 carrying a multitude of retroreflectors 95 disposed at a greater Δd distance from the camera than the object plane and within the field of view of the camera.

主权项

1. A semiconductor wafer inspection system comprising:
a light source; a camera having a field of view; an object mount configured to position a surface of a wafer at an object plane relative to the camera and within the field of view of the camera; optics configured to provide an imaging beam path for imaging the object plane onto a light sensitive substrate of the camera, and to provide a bright-field illumination beam path from the light source to the object plane, wherein an angle at the object plane between a main axis of the imaging beam path and a main axis of the bright-field illumination beam path is smaller than 2°; an actuator configured to displace the object mount in a direction parallel to the object plane or to rotate the object mount about an axis oriented transverse to the object plane; and a surface portion carrying a multitude of retroreflectors disposed at a greater distance from the camera than the object plane and within the field of view of the camera; wherein at least one of the following relation is fulfilled:
Δd>0.1*λ/NA2 and Δd>2 mm whereinΔd is a difference between a distance of the surface portion from the camera and a distance of the object plane from the camera, wherein the distances are measured along the imaging beam path;λ is a wavelength of light used for imaging; andNA is a numerical aperture of the optics on the object side of the imaging beam path.