Method and systems for improving focus accuracy in a lithography system
AssigneesASML Holding N.V., ASML US, Inc.
InventorsMichael Nelson, Justin Kreuzer, Peter Filosi, Christopher Mason
Life of this patent
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Abstract
A focus system that includes a calibration subsystem and a control subsystem. The control subsystem, which includes a control sensor, is in close proximity to the exposing of an image. The calibration subsystem, which includes a calibration sensor and a control sensor, is located remotely from, or off-axis with respect to, the exposing of an image. By separating calibration and control functions, the functional requirements can be separated into two (or more) types of sensors.
Claims17
A method for improving focus accuracy in a lithography system, comprising:
- (a) determining a calibration value of a primary control sensor using a secondary control sensor and a calibration sensor;
- (b) measuring a focal distance to a surface of a substrate using the primary control sensor;
- (c) determining an actual focal distance of the surface of the substrate based on the focal distance measured by the primary control sensor and the calibration value;
- and
- (d) adjusting a position of the substrate based on the actual focal distance,
- wherein the calibration sensor has a higher focus accuracy than each of the secondary control sensor and the primary control sensor.
A method of positioning a substrate for exposure in a lithography system, comprising:
- (a) determining a proper focal distance to a surface of the substrate using a relatively high accuracy calibration sensor;
- (b) positioning the substrate at the proper focal distance determined by the calibration sensor;
- (c) measuring the focal distance to the surface of the substrate using a relatively low accuracy secondary sensor;
- and
- (d) positioning the substrate under an exposure area of the lithography system using a relatively low accuracy primary sensor, wherein the primary sensor positions the substrate based on the focal distance measured by the secondary sensor.
Dependencies are inferred from the claim text.