EP1237046A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Method of identifying an extreme interaction pitch region, methods of designing mask patterns and manufacturing masks, device manufacturing methods and computer programs
Assignee: ASML MaskTools Netherlands BV
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Filing: 2002-02-27
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Granted: —
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Expires: 2022-02-27
Abstract
Abstract Optical proximity effects (OPEs) are a well-known phenomenon in photolithography. OPEs result from the structural interaction between the main feature and neighboring features. It has been determined by the present inventors that such structural interactions not only affect the critical dimension of the main feature at the image plane, but also the process latitude of the main feature. Moreover, it has been determined that the variation of the critical dimension as well as the process latitude of the main feature is a direct consequence of light field interference between the main feature and the neighboring features. Depending on the phase of the field produced by the neighboring features, the main feature critical dimension and process latitude can be improved by constructive light field interference, or degraded by destructive light field interference. The phase of the field produced by the neighboring features is dependent on the pitch as well as the illumination angle. For a given illumination, the forbidden pitch region is the location where the field produced by the neighboring features interferes with the field of the main feature destructively. The present invention provides a method for determining and eliminating the forbidden pitch region for any feature size and illumination condition. Moreover, it provides a method for performing illumination design in order to suppress the forbidden pitch phenomena, and for optimal placement of scattering bar assist features.
Inventors
- 👤 Xuelong Shi
- 👤 Jang Fung Chen
- 👤 Duan-Fu Stephen Hsu
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 11:14
CPC Classifications
G; G03; G03F; G03F7/00; G03F7/70; G03F7/70483; G03F7/70491; G03F7/705; H; H10; H10P; H10P76/00; G03F7/70058; G03F7/70125; G03F7/70425; G03F7/70433; G03F7/70441
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
150 words
A method of identifying an extreme interaction pitch region when designing a
mask pattern for transferring a lithographic pattern onto a substrate by use of a
lithographic apparatus, said method comprising the steps of: (a) determining an illumination intensity for a first pitch and a first illumination
angle, (b) determining an illumination intensity for said first pitch and a second
illumination angle, said second illumination angle being rotationally symmetric with
respect to said first illumination angle, (c) determining a total illumination intensity for said first pitch by combining the
illumination intensity associated with said first illumination angle and said second
illumination angle, (d) determining the log-slope of said total illumination intensity, and (e) identifying a pitch region containing said first pitch as an extreme interaction
pitch region if the value of the derivative of the log-slope of said total illumination
intensity with respect to pitch is approximately equal to zero.
Claim 2
Dependent Claim
20 words
A method according to claim 1, further comprising the steps of: repeating steps (a)-(e) for a plurality of different pitches.
Claim 3
Dependent Claim
62 words
A method according to claim 2 further comprising repeating steps (a) ― (e) for
a plurality of illumination angles and wherein a pitch is identified as an extreme
interaction pitch region if the value of the derivative of the log-slope of said total
illumination intensity with respect to pitch is approximately equal to zero for each of said
plurality of illumination angles.
Claim 4
Independent Claim
28 words
A method according to any one of the preceding claims, wherein said second
illumination angle exhibits a 90 degree rotational symmetry with respect to said first
illumination angle.
Claim 5
Independent Claim
55 words
A method according to any one of the preceding claims wherein said pitch
region is a range of pitches within +/- 0.12 x λ/NA of a specified pitch, wherein λ is the
wavelength of the exposure radiation of said lithographic apparatus and NA is the
numeric aperture of the projection system of said lithographic apparatus.
Claim 6
Independent Claim
147 words
A method according to any one of the preceding claims, further comprising the
steps of: for a given pitch identified as being in an extreme interaction pitch region: (f) determining an illumination intensity for said given pitch and a first
illumination angle, (g) determining an illumination intensity for said given pitch and a second
illumination angle, said second illumination angle being rotationally symmetric with
respect to said first illumination angle, (h) determining a second total illumination intensity for said given pitch by
combining the illumination intensity associated with said first illumination angle and said
second illumination angle, (i) determining the log-slope of said second total illumination intensity, (j) identifying a given illumination angle as being undesirable for said given pitch
if said log-slope of said second total illumination intensity is less than a predetermined
value, and (k) repeating steps (f)-(j) for a plurality of different illumination angles.
Claim 7
Dependent Claim
12 words
A method according to claim 6 wherein said predetermined value is 15.
Claim 8
Dependent Claim
86 words
A method of designing a mask pattern for transferring a lithographic pattern
onto a substrate by use of a lithographic apparatus with a desired illumination scheme,
said method comprising: identifying extreme interaction pitch regions and corresponding undesirable
illumination angles according to the method of claim 6 or 7; and designing said mask pattern by arranging features such that no combination of
features in said mask pattern has a pitch in an extreme interaction pitch region for which
illumination angles in said desired illumination scheme are undesirable.
Claim 9
Dependent Claim
63 words
A method according to claim 8 wherein said mask pattern includes main
features and optical proximity correction elements and said step of designing includes
positioning said optical proximity correction elements so as not to create pitches between
main features and optical proximity correction elements that fall in an extreme interaction
pitch region for which illumination angles in said desired illumination scheme are
undesirable.
Claim 10
Dependent Claim
32 words
A method of manufacturing a mask comprising the steps of: designing a mask pattern according to the method of claim 8 or 9; and manufacturing a mask embodying the designed mask pattern.
Claim 11
Independent Claim
158 words
A device manufacturing method comprising the steps of: providing a substrate that is at least partially covered by a layer of radiation-sensitive
material; providing a projection beam of radiation using a radiation system; using patterning means to endow the projection beam with a pattern in its cross-section; projecting the patterned beam of radiation onto a target portion of the layer of
radiation-sensitive material, characterized by : identifying extreme interaction pitch regions in said desired pattern according to
the method of any one of claims 1 to 5; creating illumination maps for said extreme interaction pitch regions in said
desired pattern, said illumination map comprising the log-shape of said total illumination
intensity as a function of illumination angle; and identifying favorable illumination angles from said illumination maps; wherein in said step of providing a projection beam, said projection beam is
arranged to illuminate said mask substantially only at angles identified as favorable
illumination angles in all said illumination maps.
Claim 12
Dependent Claim
89 words
A method according to claim 11 wherein: in said step of identifying extreme interaction pitch regions, at least first and
second extreme interaction pitch regions are identified; in said step of identifying favorable illumination angles, first and second sets of
favorable illumination angles for said first and second extreme interaction pitch regions
are identified; and wherein said steps of providing a projection beam, using patterning means and
projecting the patterned beam, are performed twice, once using said first set of favorable
illumination angles and once using said second set.
Claim 13
Dependent Claim
28 words
A method according to claim 12 wherein said step of identifying favorable
illumination angles comprises identifying the illumination angles having the highest
values of log-shape of illumination intensity.
Claim 14
Dependent Claim
34 words
A method according to claim 11 or 12 wherein said step of identifying
favorable illumination angles comprises identifying the illumination angles having a
value of log-shape of illumination intensity higher than a predetermined amount.
Claim 15
Dependent Claim
28 words
A computer program comprising program code means that, when executed
on a computer, instruct the computer to perform the method of any one of claims 1 to 9.
Claim 16
Dependent Claim
24 words
A computer program comprising program code means for controlling a
lithographic apparatus to perform the method of any one of claims 11 to 14.
Claim 17
Independent Claim
85 words
A method of identifying undesirable pitches between features when designing
an integrated device to be formed on a substrate by use of a lithographic apparatus, said
method comprising the steps of: (a) identifying extreme interaction pitch regions by determining illumination
intensity levels for a given illumination angle over a range of pitches; and (b) identifying said undesirable pitches for each extreme interaction pitch region
identified in step (a) by determining illumination intensities for a given extreme
interaction pitch region over a range of illumination angles.
Claim 18
Dependent Claim
26 words
A method according to claim 17, wherein said extreme interaction pitch
regions define regions which exhibit either substantial constructive optical interference or
substantial destructive optical interference.
Claim 19
Dependent Claim
20 words
A method according to claim 17 or 18, wherein said undesirable pitches have
corresponding illumination intensities exceeding a predetermined value.
Claim 20
Dependent Claim
22 words
A method according to claim 17, 18 or 19, wherein said features comprise a
main feature and an optical proximity correction element.
References Cited (Backward Citations)
No citation records indexed.
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