Systems and methods for detecting focus variation in photolithograph process using test features printed from photomask test pattern images
AssigneeSamsung Electronics Co., Ltd.
InventorHo-Chul Kim
Life of this patent
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Abstract
Systems and methods are provided for detecting focus variation in a lithographic process using photomasks having test patterns adapted to print test features with critical dimensions that can be measured and analyzed to determine magnitude and direction of defocus from a best focus position of an exposure tool during the lithographic process.
Claims30
A method for monitoring focus of a lithographic process, the method comprising:
- obtaining a semiconductor wafer having a photoresist pattern formed thereon, the photoresist pattern including a printed test pattern comprising first and second printed test features;
- determining a printed critical dimension CD1 of the first printed test feature and a printed critical dimension CD2 of the second printed test feature;
- determining a relative CD difference between the printed critical dimensions CD2 and CD1;
- and
- determining a magnitude and direction of defocus from a best focus setting for the lithographic process based on the determined relative CD difference.
A program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform method steps for monitoring focus of a lithographic process, the method steps comprising:
- obtaining a semiconductor wafer having a photoresist pattern formed thereon, the photoresist pattern including a printed test pattern comprising first and second printed test features;
- determining a printed critical dimension CD1 of the first printed test feature and a printed critical dimension CD2 of the second printed test feature;
- determining a relative CD difference between the printed critical dimensions CD2 and CD1;
- and
- determining a magnitude and direction of defocus from a best focus setting for the lithographic process based on the determined relative CD difference.
A photomask, comprising:
- a circuit layout pattern;
- and
- a test pattern comprising first and second test features, wherein the first and second test features are formed having at least one feature size equal to a design CD, wherein the test pattern is adapted to create a first printed test feature with a printed critical dimension CD1 and a second printed test feature with a printed critical dimension CD2 such that a relative difference between the printed critical dimensions CD2 and CD1 correlates to a magnitude and direction of defocus from a best focus setting for the lithographic process.
A photolithography system, comprising:
- an exposure system to expose a photoresist coated wafer with light through a photomask having a mask pattern including a circuit layout pattern and a test pattern, wherein the test pattern comprises first and second test features having at least one feature size equal to a design CD, wherein the test pattern is adapted to create a first printed test feature with a printed critical dimension CD1 and a second printed test feature with a printed critical dimension CD2;
- and
- a focal point monitoring system that detects focus drift of the exposure system, wherein the focal point monitoring system processes measured CD data of the first and second printed tests features to determine a magnitude and direction of focus drift based on a CD difference between CD2 and CD1.
Dependencies are inferred from the claim text.