Focus control arrangement and method
AssigneeASML Netherlands B.V.
InventorsMartin Jacobus Johan Jak, Armand Eugene Albert Koolen, Gerbrand Van Der Zouw, Dirk Karel Margaretha Broddin
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Abstract
An inspection apparatus includes an optical system, which has a radiation beam delivery system for delivering radiation to a target, and a radiation beam collection system for collecting radiation after scattering from the target. Both the delivery system and the collection system comprise optical components that control the characteristics of the radiation and the collected radiation. By controlling the characteristics of one or both of the radiation and collected radiation, the depth of focus of the optical system may be increased.
Claims20
A method for increasing a depth of focus of an optical system in an inspection apparatus, the method comprising:
- delivering radiation two or more times along a delivery path to a target using a radiation beam delivery system, wherein each radiation delivery focuses at a different position along the delivery path, and wherein the target has a dimension, as measured parallel to the delivery path, that exceeds a dimension of the depth of focus along the delivery path;
- collecting radiation scattered by the target after each radiation delivery using a radiation collection system;
- detecting the collected radiation using a detector;
- determining dark field detection results based on the collected radiation;
- and
- combining the dark field detection results to produce an extended depth of focus having a dimension that exceeds the dimension of the target.
An inspection apparatus comprising:
- an optical system comprising:
- a radiation beam delivery system configured to deliver radiation two or more times along a delivery path to a target, wherein each radiation delivery focuses at a different position along the delivery path, and wherein the target has a dimension, as measured parallel to the delivery path, that exceeds a dimension of a depth of focus of the optical system along the delivery path;
- a radiation collection system configured to collect radiation scattered by the target after each radiation delivery;
- and
- a detection system configured to detect the collected radiation,
- wherein the optical system is configured to:
- determine dark field detection results based on the collected radiation, and
- combine the dark field detection results to produce an extended depth of focus having a dimension that exceeds the dimension of the target.
A lithographic apparatus comprising:
- an inspection apparatus comprising an optical system, the optical system comprising:
- a radiation beam delivery system configured to deliver radiation two or more times along a delivery path to a target, wherein each radiation delivery focuses at a different position along the delivery path, and wherein the target has a dimension, as measured parallel to the delivery path, that exceeds a dimension of a depth of focus of the inspection apparatus along the delivery path;
- a radiation collection system configured to collect radiation scattered by the target after each radiation delivery;
- and
- a detection system configured to detect the collected radiation,
- wherein the optical system is configured to:
- determine dark field detection results based on the collected radiation,
- combine the dark field detection results to produce an extended depth of focus having a dimension that exceeds the dimension of the target.
A computer program product comprising a computer readable medium having instructions stored thereon, that, when executed on a processor, cause the processor to control an optical system to perform operations, the operations comprising:
- delivering radiation two or more times along a delivery path to a target using a radiation beam delivery system, wherein each radiation delivery focuses at a different position along the delivery path;
- and wherein the target has a dimension, as measured parallel to the delivery path, that exceeds a dimension of a depth of focus of the optical system along the delivery path;
- collecting radiation scattered by the target after each radiation delivery using a radiation collection system;
- detecting the collected radiation using a detector;
- determining dark field detection results based on the collected radiation;
- and
- combining the detection results to produce an extended depth of focus having a dimension that exceeds the dimension of the target.
A computer program product comprising a computer readable medium having instructions stored thereon, that, when executed on a processor, cause the processor to control an inspection apparatus to perform operations, the operations comprising:
- delivering radiation two or more times along a delivery path to a target using a radiation beam delivery system, wherein each radiation delivery focuses at a different position along the delivery path, and wherein the target has a dimension, as measured parallel to the delivery path, that exceeds a dimension of a depth of focus of the inspection apparatus along the delivery path;
- collecting radiation scattered by the target after each radiation delivery using a radiation collection system;
- detecting the collected radiation using a detector;
- determining dark field detection results based on the collected radiation;
- processing the detected collected radiation to generate an actuating signal for controlling a controllable element in the inspection apparatus;
- and
- combining the dark field detection results to produce an extended depth of focus having a dimension that exceeds the dimension of the target.
Dependencies are inferred from the claim text.