US 6,146,910 AGranted

Target configuration and method for extraction of overlay vectors from targets having concealed features

AssigneeThe United States of America as represented by the Secretary of Commerce

InventorsMichael W. Cresswell, Santos Mayo, Jeremiah R. Lowney

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Abstract

A method is provided for extracting overlay information from a target of an integrated circuit wafer wherein the first-level target has features wh are optically concealed by an overlying opaque planarized film. The target employed has an architecture including a resist feature on the planarized film and an embedded electron backscattering target feature disposed beneath the planarized film. This target is scanned with an electron bean of an energy sufficiently high (e.g., at least 11 keV) to penetrate the planarized film, be backscattered by the backscattered feature and return through the planarized film or through the planarized film and the resist feature. Electrons backscattered from the conductive first-level target feature through the resist feature are detected and a signal profile is generated based thereon. This signal profile is analyzed to extract overlay information.

Claims10

Dependent claims

A method for extracting overlay information from a first-level target of an integrated circuit wafer wherein the target includes embedded features at a first level which are optically concealed by an opaque overlying planarized film, said method comprising:

providing at least one resist feature on an opaque planarized film and an embedded electron backscattering target feature disposed beneath the film at least partially under the resist feature;
scanning the target with a primary electron beam of an energy sufficiently high to penetrate the planarized film, to be backscattered by the backscattering feature and to traverse back through the planarized film;
detecting a first signal due to backscattered electrons from said first-level target together with a further signal due to backscattered electrons traversing through the resist feature, and generating a signal profile based on said signals;
and
analyzing said signal profile to extract overlay information.

2 more elements

Dependencies are inferred from the claim text.