Patent ID: 8576393

Claim:
An apparatus for simultaneous optical inspection and detection of defects on opposite surfaces of a wafer, the apparatus comprising: a circumferential dark field source disposed around a periphery of the wafer and having an optical axis that is normal to the wafer and being configured to illuminate opposite surfaces of the wafer simultaneously; a pair of bright illumination sources both configured to illuminate respective opposite surfaces of the wafer; a pair of optical sensors disposed on opposite surfaces of the wafer and being normal to both the wafer surfaces and to the bright illumination source, both of said sensors having an optical axis that is coaxial with the optical axis of the circumferential dark field source, said sensors being configured for capturing light reflected from the wafer surface and producing a sensor signal having sufficient resolution for detection of surface defects; and a processing unit coupled to the optical sensor for processing the sensor signal in accordance with stored instructions for accumulating data representative of an image of the wafer and defects, and for providing an indication of defects.