US5667918A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of lithography using reticle pattern blinders
Assignee: Round Rock Research LLC
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Filing: 1995-06-27
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Granted: 1997-09-16
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Expires: 2015-06-27
Abstract
Abstract An improved reticle pattern for semiconductor lithography systems that utilize partially coherent or off-axis illumination includes blinder structures located adjacent to the exterior features of the reticle pattern. The blinder structures protect the exterior features from light that is scattered from large low resolution areas of the reticle in a defocus mode of the lithography system. This protects the exterior features projected onto a semiconductor wafer from degradation and improves the resolution, contrast and depth of focus of the lithographic system. In an illustrative embodiment, the reticle pattern is formed as a simple grating in which the exterior features of the grating are protected from image degradation by blinder structures formed as one or more solid blinder lines.
Inventors
- 👤 Steve K. Brainerd
- 👤 J. Brett Rolfson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 12:05
CPC Classifications
G; G03; G03F; G03F7/00; G03F7/70; G03F7/70058; G03F7/70125; G03F1/00; G03F1/36; G03F7/70425; G03F7/70433
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
103 words
A lithographic method comprising: providing a lithographic apparatus having partially coherent or off-axis illumination; providing a reticle configured for use with the lithographic apparatus to project a pattern onto a target; forming a blinder structure including at least two parallel spaced blinders in an area of the reticle adjacent to an edge of a protected feature of the pattern, said blinders having a thickness below a resolution limit of the lithographic apparatus, said blinder structure having an overall width equal to a width of the protected feature, said overall width inclusive of the thicknesses of the blinders and a spacing between the blinders.
Claim 2
Dependent Claim
103 words
A lithographic method comprising: providing a lithographic apparatus having partially coherent or off-axis illumination; providing a reticle configured for use with the lithographic apparatus to project a pattern onto a target; forming a blinder structure including at least two parallel spaced blinders in an area of the reticle adjacent to an edge of a protected feature of the pattern, said blinders having a thickness below a resolution limit of the lithographic apparatus, said blinder structure having an overall width equal to a width of the protected feature, said overall width inclusive of the thicknesses of the blinders and a spacing between the blinders.
Claim 3
Dependent Claim
40 words
The method as claimed in claim 1 wherein the protected feature comprises a line and the blinder structure is parallel to and spaced from an exterior edge of the line by a distance equal to a linewidth of the line.
Claim 4
Dependent Claim
20 words
The method as claimed in claim 1 wherein the blinder structure comprises a pair of parallel spaced solid blinder lines.
Claim 5
Dependent Claim
19 words
The method as claimed in claim 1 and wherein the blinder structure comprises three parallel spaced solid blinder lines.
Claim 6
Dependent Claim
42 words
The method as claimed in claim 1 wherein the pattern comprises a plurality of spaced lines and the blinder structure is formed in a space between the lines adjacent to an end portion of the lines and generally perpendicular to the lines.
Claim 7
Dependent Claim
35 words
The method as claimed in claim 1 and further comprising forming a second blinder structure adjacent to an edge of the blinder structure, said second blinder structure comprising at least two parallel spaced blinder lines.
Claim 8
Dependent Claim
152 words
A lithographic method comprising: providing a lithographic apparatus having partially coherent or off-axis illumination; forming a reticle configured for use with the lithographic aparatus to project a primary pattern on a target, said primary pattern including parallel spaced lines; forming a plurality of blinder structures in areas of the reticle adjacent to exterior longitudinal and lateral edge portions of the lines of the primary pattern to prevent scattered light from the areas from degrading a projected image of the lines of the primary pattern; said blinder structures each comprising at least two parallel spaced blinder lines, each blinder line having a thickness that is less than a resolution of the lithographic apparatus and with an overall width of each blinder structure inclusive of the thicknesses of the blinder lines and a spacing between the blinder lines for each blinder structure, equal to a linewidth of a single line of the primary pattern.
Claim 9
Dependent Claim
152 words
A lithographic method comprising: providing a lithographic apparatus having partially coherent or off-axis illumination; forming a reticle configured for use with the lithographic aparatus to project a primary pattern on a target, said primary pattern including parallel spaced lines; forming a plurality of blinder structures in areas of the reticle adjacent to exterior longitudinal and lateral edge portions of the lines of the primary pattern to prevent scattered light from the areas from degrading a projected image of the lines of the primary pattern; said blinder structures each comprising at least two parallel spaced blinder lines, each blinder line having a thickness that is less than a resolution of the lithographic apparatus and with an overall width of each blinder structure inclusive of the thicknesses of the blinder lines and a spacing between the blinder lines for each blinder structure, equal to a linewidth of a single line of the primary pattern.
Claim 10
Dependent Claim
36 words
The method as claimed in claim 7 wherein at least one of the blinder structures is spaced from a longitudinal edge of an exterior line of the line-space pattern by a distance equal to the linewidth.
Claim 11
Dependent Claim
36 words
The method as claimed in claim 7 wherein at least one of the blinder structures is spaced from an exterior lateral edge of the lines of the line-space pattern by a distance equal to the linewidth.
Claim 12
Dependent Claim
38 words
The method as claimed in claim 7 wherein at least one of the blinder structures is generally perpendicular to a longitudinal edge of the lines of the line-space pattern and is located within a space between the lines.
Claim 13
Dependent Claim
17 words
The method as claimed in claim 7 wherein each blinder structure comprises two parallel spaced blinder lines.
Claim 14
Dependent Claim
17 words
The method as claimed in claim 7 wherein each blinder structure comprises three parallel spaced blinder lines.
Claim 15
Dependent Claim
25 words
The method as claimed in claim 7 and further comprising forming additional blinder structures adjacent to and spaced from exposed edges of the blinder structures.
Claim 16
Dependent Claim
110 words
A lithographic method comprising: providing a lithographic apparatus having partially coherent or off-axis illumination; providing a reticle configured for use with the lithographic apparatus and including a pattern of parallel spaced lines each having an equal linewidth; forming blinder structures in areas of the reticle adjacent to exterior edge portions of the lines to prevent scattered light from the areas from degrading an image of the lines, said blinder structures comprising at least two blinder lines, each said blinder line having a thickness that is less than a resolution of the lithographic apparatus, each said blinder structure spaced from a corresponding exterior edge by a distance equal to the linewidth.
Claim 17
Dependent Claim
110 words
A lithographic method comprising: providing a lithographic apparatus having partially coherent or off-axis illumination; providing a reticle configured for use with the lithographic apparatus and including a pattern of parallel spaced lines each having an equal linewidth; forming blinder structures in areas of the reticle adjacent to exterior edge portions of the lines to prevent scattered light from the areas from degrading an image of the lines, said blinder structures comprising at least two blinder lines, each said blinder line having a thickness that is less than a resolution of the lithographic apparatus, each said blinder structure spaced from a corresponding exterior edge by a distance equal to the linewidth.
Claim 18
Dependent Claim
27 words
The method as claimed in claim 14 wherein the blinder structures comprises at least two parallel spaced blinder lines having an overall width equal to the linewidth.
Claim 19
Dependent Claim
32 words
The method as claimed in claim 14 wherein some of the blinder structures are formed by blinder lines parallel to and spaced from a longitudinal edge of exterior lines of the pattern.
Claim 20
Dependent Claim
32 words
The method as claimed in claim 14 wherein some of the blinder structures are formed by blinder lines parallel to and spaced from a lateral edge of exterior lines of the pattern.
Claim 21
Dependent Claim
17 words
The method as claimed in claim 14 wherein each blinder structure comprises three parallel spaced blinder lines.
Claim 22
Dependent Claim
136 words
A lithographic method comprising: providing a lithographic apparatus having partially coherent or off-axis illumination; forming a reticle configured for use with the lithographic apparatus and having a primary pattern comprising spaced lines; forming blinder structures in areas of the reticle adjacent to edge portions of the lines to prevent scattered light from the areas from degrading an image of the lines, said blinder structures each comprising at least two parallel spaced blinder lines, each said blinder line having a thickness that is less than a resolution of the lithographic apparatus; said blinder structures having an overall width inclusive of the blinder lines that is approximately equal to a linewidth of a single line of the primary pattern, and at least some of said blinder structures having an associated blinder structure for protecting an exposed edge thereof.
Claim 23
Dependent Claim
136 words
A lithographic method comprising: providing a lithographic apparatus having partially coherent or off-axis illumination; forming a reticle configured for use with the lithographic apparatus and having a primary pattern comprising spaced lines; forming blinder structures in areas of the reticle adjacent to edge portions of the lines to prevent scattered light from the areas from degrading an image of the lines, said blinder structures each comprising at least two parallel spaced blinder lines, each said blinder line having a thickness that is less than a resolution of the lithographic apparatus; said blinder structures having an overall width inclusive of the blinder lines that is approximately equal to a linewidth of a single line of the primary pattern, and at least some of said blinder structures having an associated blinder structure for protecting an exposed edge thereof.
Claim 24
Dependent Claim
19 words
The method as claimed in claim 19 wherein forming the reticle is performed using an electron beam mask writer.
Claim 25
Dependent Claim
20 words
The method as claimed in claim 19 wherein forming the blinder structures is performed using an electron beam mask writer.
Claim 26
Dependent Claim
20 words
The method as claimed in claim 19 wherein the reticle comprises a transparent substrate and a metal layer formed thereon.
Claim 27
Dependent Claim
20 words
The method as claimed in claim 19 and further comprising placing a reduction lens between the reticle and a target.
Claim 28
Dependent Claim
17 words
The method as claimed in claim 23 and wherein the reduction lens comprises a 5× reduction lens.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2000-09-15 | 2001-03-17 | 2001-09-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-09-15 | 2005-03-17 | 2005-09-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-09-15 | 2009-03-17 | 2009-09-16 | $7700.00 | Window Closed / Lapsed |