Methods and Scatterometers, Lithographic Systems, and Lithographic Processing Cells
First Claim
1. A method of determining the focus of a lithographic apparatus used in a lithographic process on a substrate, the method comprising:
- using the lithographic process to form a structure on the substrate, the structure having at least one feature which has a profile which has an asymmetry which depends on the focus of the lithographic apparatus on the substrate;
a first measurement comprising forming and detecting a first image of the periodic structure while illuminating the structure with a first beam of radiation, the first image being formed using a first part of non-zero order diffracted radiation while excluding zero order diffracted radiation;
a second measurement comprising forming and detecting a second image of the periodic structure while illuminating the structure with a second beam of radiation, the second image being formed using a second part of the non-zero order diffracted radiation which is symmetrically opposite to the first part in a diffraction spectrum; and
using the first and second images detected in the first and second measurements to determine the asymmetry in the profile of the periodic structure and/or to provide an indication of the focus on the substrate.
1 Assignment
0 Petitions
Accused Products
Abstract
In a method of determining the focus of a lithographic apparatus used in a lithographic process on a substrate, the lithographic process is used to form a structure on the substrate, the structure having at least one feature which has an asymmetry in the printed profile which varies as a function of the focus of the lithographic apparatus on the substrate. A first image of the periodic structure is formed and detected while illuminating the structure with a first beam of radiation. The first image is formed using a first part of non-zero order diffracted radiation. A second image of the periodic structure is foamed and detected while illuminating the structure with a second beam of radiation. The second image is formed using a second part of the non-zero order diffracted radiation which is symmetrically opposite to the first part in a diffraction spectrum. The ratio of the intensities of the measured first and second portions of the spectra is determined and used to determine the asymmetry in the profile of the periodic structure and/or to provide an indication of the focus on the substrate. In the same instrument, an intensity variation across the detected portion is determined as a measure of process-induced variation across the structure. A region of the structure with unwanted process variation can be identified and excluded from a measurement of the structure.
-
Citations
36 Claims
-
1. A method of determining the focus of a lithographic apparatus used in a lithographic process on a substrate, the method comprising:
-
using the lithographic process to form a structure on the substrate, the structure having at least one feature which has a profile which has an asymmetry which depends on the focus of the lithographic apparatus on the substrate; a first measurement comprising forming and detecting a first image of the periodic structure while illuminating the structure with a first beam of radiation, the first image being formed using a first part of non-zero order diffracted radiation while excluding zero order diffracted radiation; a second measurement comprising forming and detecting a second image of the periodic structure while illuminating the structure with a second beam of radiation, the second image being formed using a second part of the non-zero order diffracted radiation which is symmetrically opposite to the first part in a diffraction spectrum; and using the first and second images detected in the first and second measurements to determine the asymmetry in the profile of the periodic structure and/or to provide an indication of the focus on the substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
-
11. An angularly resolved scatterometer configured to determine the focus of a lithographic apparatus used in a lithographic process on a substrate, wherein the lithographic process is used to form a structure on the substrate, the structure having at least one feature which has a profile which has an asymmetry which depends on the focus of the lithographic apparatus on the substrate, the scatterometer comprising:
-
an illumination arrangement operable to deliver first and second beams of radiation to the substrate for use in first and second measurements; a detection arrangement operable during the first and second measurements to form and detect respective first and second images of the substrate using radiation diffracted from the substrate; and a stop arrangement within the detection arrangement, wherein the illumination arrangement and stop arrangement together are effective to stop zero order diffracted radiation contributing to the first and second images, while the first and second images are formed using first and second parts respectively of the non-zero order diffracted radiation, the first and second parts being symmetrically opposite one another in a diffraction spectrum of the diffracted radiation; and a computational arrangement operable to determine the profile asymmetry for the feature from the first and second images and/or to use the determined asymmetry and the relationship between the focus and the asymmetry for each feature to provide an indication of the focus on the substrate. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
-
-
21. A lithographic system comprising:
a lithographic apparatus comprising; an illumination optical system arranged to illuminate a pattern; a projection optical system arranged to project an image of the pattern on to a substrate; and an angularly resolved scatterometer configured to determine the focus of the lithographic system used in a lithographic process on the substrate, wherein the lithographic process is used to form a structure on the substrate, the structure having at least one feature which has a profile which has an asymmetry which depends on the focus of the lithographic system on the substrate, the scatterometer comprising; an illumination arrangement operable to deliver first and second beams of radiation to the substrate for use in first and second measurements; a detection arrangement operable during the first and second measurements to form and detect respective first and second images of the substrate using radiation diffracted from the substrate; and a stop arrangement within the detection arrangement, wherein the illumination arrangement and stop arrangement together are effective to stop zero order diffracted radiation contributing to the first and second images, while the first and second images are formed using first and second parts respectively of the non-zero order diffracted radiation, the first and second parts being symmetrically opposite one another in a diffraction spectrum of the diffracted radiation; and a computational arrangement operable to determine the profile asymmetry for the feature from the first and second images and/or to use the determined asymmetry and the relationship between the focus and the asymmetry for each feature to provide an indication of the focus on the substrate.
-
22. A lithographic cell comprising:
-
a coater arranged to coat substrates with a radiation sensitive layer; a lithographic apparatus arranged to expose images onto the radiation sensitive layer of substrates coated by the coater; a developer arranged to develop images exposed by the lithographic apparatus; and an angularly resolved scatterometer configured to determine the focus of the lithographic apparatus used in a lithographic process on the substrate, wherein the lithographic process is used to form a structure on the substrate, the structure having at least one feature which has a profile which has an asymmetry which depends on the focus of the lithographic apparatus on the substrate, the scatterometer comprising; an illumination arrangement operable to deliver first and second beams of radiation to the substrate for use in first and second measurements; a detection arrangement operable during the first and second measurements to form and detect respective first and second images of the substrate using radiation diffracted from the substrate; and a stop arrangement within the detection arrangement, wherein the illumination arrangement and stop arrangement together are effective to stop zero order diffracted radiation contributing to the first and second images, while the first and second images are formed using first and second parts respectively of the non-zero order diffracted radiation, the first and second parts being symmetrically opposite one another in a diffraction spectrum of the diffracted radiation; and a computational arrangement operable to determine the profile asymmetry for the feature from the first and second images and/or to use the determined asymmetry and the relationship between the focus and the asymmetry for each feature to provide an indication of the focus on the substrate.
-
-
23. An angularly resolved scatterometer configured to determine the focus of a lithographic apparatus used in a lithographic process on a substrate, wherein the lithographic process is used to form a structure on the substrate, the structure having at least one feature which has a profile which has an asymmetry which depends on the focus of the lithographic apparatus on the substrate, the scatterometer comprising:
-
an illumination device effective to produce a beam of radiation; a masking device arranged such that a beam of radiation produced by the illumination device and directed onto the substrate through the masking device will illuminate the structure within a first range of angles; a detection device configured to detect radiation diffracted from the substrate; a stop device between the substrate and the detection device, the masking device and stop device together being effective to stop zero order diffracted radiation and a part of the higher order diffracted radiation from being detected; a rotation device operative to rotate the masking device and the substrate relative to each other about their respective optical axes such that after the relative rotation the structure is illuminated within a second range of angles, the second range being diametrically opposed to the first range within the cross section of the illuminating beam; wherein the detection device is effective to measure different portions of the image produced by the diffracted radiation produced by directing the beam of radiation onto the periodic structure through the stop device before and after the rotation of the masking device and the substrate relative to each other about their respective optical axes; and a computational device operative to determine the profile asymmetry for the feature from the measured spectra measured before and after the rotation of the masking device and the substrate device relative to each other or to use the determined asymmetry and the relationship between the focus and the asymmetry for each feature to provide an indication of the focus on the substrate. - View Dependent Claims (24)
-
-
25. A method of detecting process variation in a structure on a substrate, the method comprising:
-
directing a beam of radiation onto the substrate so as to illuminate the structure; forming an image of the structure using only one selected diffraction order of radiation diffracted by the substrate;
detecting a portion of the formed image;determining an intensity variation across the detected portion, corresponding to variation in diffraction efficiency across the structure; and identifying process-induced variation in the structure using the determined intensity variation. - View Dependent Claims (26, 27, 28, 29)
-
-
30. An angularly resolved scatterometer configured to determine process-induced variation in a structure on a substrate, the angularly resolved scatterometer comprising:
-
an illumination device operable to produce a beam of radiation; a directing device configured to direct the beam of radiation onto the substrate to illuminate the structure; a detection device configured to form and detect an image of the structure using radiation diffracted from the substrate; a stop device configured to stop all except one order of diffracted radiation from being detected by the detection device; and a computational arrangement operative to determine an intensity variation across the detected radiation, corresponding to variation in diffraction efficiency across the structure; and
to identify process-induced variation in the structure using the determined intensity variation. - View Dependent Claims (31, 32, 33, 34)
-
-
35. A lithographic system comprising:
-
a lithographic apparatus comprising; an illumination optical system arranged to illuminate a pattern; a projection optical system arranged to project an image of the pattern on to a substrate; and an angularly resolved spectrometer comprising; an illumination device operable to produce a beam of radiation; a directing device configured to direct the beam of radiation onto the substrate to illuminate the structure; a detection device configured to detect radiation diffracted from the substrate and to form an image; a stop device between the substrate and the detection device, the stop device being configured to stop all except one order of diffracted radiation from being detected by the detection device; and a computational arrangement operative to determine an intensity variation across the detected image, corresponding to variation in diffraction efficiency across the structure, and to identify process-induced variation in the structure using the determined intensity variation.
-
-
36. A lithographic cell comprising:
-
a coater arranged to coat substrates with a radiation sensitive layer; a lithographic apparatus arranged to expose images onto the radiation sensitive layer of substrates coated by the coater; a developer arranged to develop images exposed by the lithographic apparatus; and an angularly resolved spectrometer comprising; an illumination device operable to produce a beam of radiation; a directing device configured to direct the beam of radiation onto the substrate to illuminate the structure; a detection device configured to detect radiation diffracted from the substrate and to form an image; a stop device between the substrate and the detection device, the stop device being configured to stop all except one order of diffracted radiation from being detected by the detection device; and a computational arrangement operative to determine an intensity variation across the detected image, corresponding to variation in diffraction efficiency across the structure, and to identify process-induced variation in the structure using the determined intensity variation.
-
Specification