Therma-wave, Inc.

Jeffrey E McAninch

Jeffrey Thomas Fanton

Lawrence D Rotter

David Y Wang

The subject invention relates to a broadband optical metrology system that segregates the broadband radiation into multiple sub-bands to improve overall performance. Each sub-band includes only a fraction of the original bandwidth. The optical path&#x2014;the light path that connects the illuminator, the sample and the detector&#x2014;of each sub-band includes a unique sub-band optical system designed to optimize the performance over the spectral range spanned by the sub-band radiation. All of the sub-band optical systems are arranged to provide small-spot illumination at the same measurement position. Optional purging of the individual sub-band optical paths further improves performance.

Measurement system with separate optimized beam paths

A purge system for an optical metrology tool is disclosed. The metrology tool includes an optics plate for supporting the measurement optics. A movable stage supports a wafer below the optics plate. Inert purge gas is injected between the lower surface of the optics plate and the upper surface of the wafer. The gas flow functions to stabilize and homogenize the ambient in the measurement region. The gas flow also serves to clear the measurement area of absorbing species which is particular useful for measurements using vacuum ultraviolet light.

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Livermore, CA, United States of America

Jeffrey E McAninch