Patent EP1239331A2 successfully refreshed from Google Patents.
EP1239331A2
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EP
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Illumination optimization for specific mask patterns
Assignee: ASML Netherlands BV
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Filing: 2002-02-22
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Granted: —
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Expires: 2022-02-22
Abstract
Abstract A method and apparatus for microlithography. The method and apparatus include optimizing illumination modes based on characteristics of a specific mask pattern. The illumination is optimized by determining an appropriate illumination mode based on diffraction orders of the reticle, and the autocorrelation of the projection optic. By elimination of parts of the illumination pattern which have no influence on modulation, excess DC light can be reduced, thereby improving depth of focus. Optimization of mask patterns includes addition of sub-resolution features to reduce pitches and discretize the probability density function of the space width.
Inventors
- 👤 Robert John Socha
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 10:46
CPC Classifications
G; G03; G03F; G03F7/00; G03F7/20; G03F7/70; G03F7/70425; G03F7/70433; G03F1/00; G03F1/36; G03F7/70058; G03F7/70125; G03F7/70441; G03F7/70483; G03F7/70491; G03F7/705
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
78 words
A method of optimizing an illumination profile for a selected patterning
means pattern, comprising the steps of: defining a transmission cross coefficient function for an optical system including
an illuminator and the selected patterning means pattern; determining relative relevance to imaging of diffraction orders based on the
selected pattern; and calculating an optimized illumination configuration from the transmission cross
coefficient function, weighting regions of the illumination configuration based on the
relative relevance to imaging of the diffraction orders.
Claim 2
Dependent Claim
32 words
A method as in claim 1, wherein the step of determining relative
relevance to imaging of diffraction orders further comprises the step of: determining a characteristic pitch of the selected mask pattern.
Claim 3
Dependent Claim
45 words
A method as in claim 2, further comprising the steps of: identifying a critical region of the selected pattern prior to determining the
characteristic pitch, wherein determining the characteristic pitch for the selected pattern is performed
by determining the characteristic pitch for the critical region.
Claim 4
Dependent Claim
73 words
A method as in claim 3, wherein the step of identifying a critical region
further comprises identifying a plurality of critical regions and wherein determining the
characteristic pitch for the critical region includes: comparing a pitch of each identified critical region; and if the pitch of each identified region is substantially equal, determining the
characteristic pitch for the critical region to be equal to the characteristic pitch of one of
the identified regions.
Claim 5
Independent Claim
44 words
A method as in any one of the preceding claims, further comprising
weighting regions of the illuminator configuration based on a selected optimized metric
selected from the group consisting of depth of focus, end-of-line, image log slope (ILS),
image slope (IS), and aberration sensitivity.
Claim 6
Dependent Claim
80 words
A method as in claim 1 or 2, further comprising the steps of: identifying a plurality of critical regions; determining a pitch of each of the identified critical regions; and calculating optimized illumination configurations from the transmission cross
coefficient function, weighing orders based on relevance to imaging of diffraction
orders for each critical region, and wherein calculating an optimized illumination configuration further comprises
calculating a composite optimized illumination configuration based on the calculated
optimized illumination configuration for each critical region.
Claim 7
Independent Claim
36 words
A method as in any one of the preceding claims, further comprising the
steps of: modifying the selected pattern by optical proximity correction techniques to
reduce a total number of different pitches in the mask pattern.
Claim 8
Dependent Claim
30 words
A method as in claim 7, wherein the step of modifying the selected
pattern by optical proximity correction techniques further comprises addition of sub-resolution
features to the selected mask pattern.
Claim 9
Dependent Claim
23 words
A method as in claim 7, wherein the steps of modifying the selected
pattern and calculating an optimized illumination configuration steps are iterated.
Claim 10
Dependent Claim
39 words
A computer program for optimizing an illumination profile comprising
program code means that, when executed on a computer system, instruct the computer
system to carry out the steps of the method of any one of claims 1 to 9.
Claim 11
Independent Claim
105 words
A device manufacturing method comprising the steps of: (a) providing a substrate that is at least partially covered by a layer
of radiation-sensitive material; (b) providing a projection beam of radiation using an illumination system; (c) using patterning means to endow the projection beam with a pattern
in its cross-section; (d) projecting the patterned beam of radiation onto a target portion of the layer of
radiation-sensitive material, wherein, prior to step (d), the cross-sectional intensity
distribution in the projection beam produced in step (b) is tailored to the pattern
employed in step (c) using a method according to any one of claims 1 to 9.
Claim 12
Dependent Claim
154 words
A lithographic projection apparatus comprising: an illumination system for providing a projection beam of radiation; a support structure for supporting patterning means, the patterning
means serving to pattern the projection beam according to a desired
pattern; a substrate table for holding a substrate; a projection system for projecting the patterned beam onto a target
portion of the substrate, wherein the apparatus additionally comprises: calculating means, for defining a transmission cross coefficient function for the
illuminator and the patterning means, determining relative relevance to imaging of
diffraction orders based on the pattern produced by the patterning means, and
calculating an optimized illumination configuration from the transmission cross
coefficient function, weighing regions of the illumination configuration based on the
relative relevance to imaging of the diffraction orders; and selecting means, for selecting the cross-sectional intensity
distribution in the projection beam exiting the illumination system in
accordance with the illumination configuration calculated by the said
calculating means.
Claim 13
Independent Claim
58 words
A method of optimizing a selected mask design comprising: identifying critical features of the selected mask design; determining an optimized illumination profile based on diffraction orders of the
critical features; and modifying the selected mask design by use of optical proximity correction
techniques which are selected to reduce a number of pitches present in the selected mask
design.
Claim 14
Dependent Claim
45 words
A method as in claim 11 wherein the optical proximity correction further
comprises addition of sub-resolution features selected to modify a continuous
probability density function of the space width of the selected mask design such that the
modified probability density function has an increased discretization.
Claim 15
Dependent Claim
31 words
A method as in claim 13 or 14 wherein said step of determining an
optimized illumination profile comprises the steps of the method of any one of claims 1
to 9.
Claim 16
Dependent Claim
35 words
A computer program for optimizing a selected mask design comprising
program code means that, when executed on a computer, instruct the computer to carry
out the method of any one of claims 13 to 15.
References Cited (Backward Citations)
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