US 2011/0299759 A1Published application

Reticle defect inspection with model-based thin line approaches

AssigneeKLA-Tencor Corporation

InventorsRuifang Shi, Xiaochun Li

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Abstract

Provided are novel inspection methods and systems for inspecting photomasks to identify various defects using a model-based approach and information obtained from modeled images. Modeled or simulation images are generated directly from test or reference images. Some examples include aerial images that represent expected patterns projected by a lithography system on a substrate as well as photoresist images that represent expected resist patterns. Test images are first represented as a band limited mask pattern, which may include only linear terms for faster image processing. This pattern is then used to construct a modeled image, which in turn is used to construct a model-based feature map. This map serves as a base for inspecting the original test images to identify photomask defects and may include information that allows differentiating between various feature types based on their lithographic significance and other characteristics.

Claims29

Dependent claims

A method for inspecting a photomask to identify lithographically significant defects, the method comprising:

providing the photomask comprising one or more printable features and one or more non-printable features, the photomask configured to achieve lithographic transfer of the one or more printable features onto a substrate using a lithography system;
producing test light intensity images of the photomask using an inspection apparatus, the test light intensity images comprising a test transmission image and a test reflection image;
constructing a band limited mask pattern;
providing a model of the lithography system to be employed in the lithographic transfer;
constructing an aerial image of the band limited mask pattern by applying the model of the lithography system to the band limited mask pattern, wherein constructing the aerial image comprises separating the one or more non-printable features from the one or more printable features based on optical intensity distributions in the aerial image;
building a model-based feature map using the aerial image of the mask pattern,
wherein the model-based feature map differentiates between the one or more printable features and the one or more non-printable features;
and
analyzing the test light intensity images using the model-based feature map to identify any lithographically significant defects.

6 more elements

Dependencies are inferred from the claim text.