U.S. patent application number 09/758708 was filed with the patent office on 2001-08-23 for method of compensating for pattern dimension variation caused by re-scattered electron beam in electron beam lithography.
This patent application is currently assigned to Samsung Electronics Co., Ltd.. Invention is credited to Choi, Ji-hyeon, Ki, Won-tai.
Application Number | 20010016295 09/758708 |
Document ID | / |
Family ID | 19638049 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010016295 |
Kind Code |
A1 |
Choi, Ji-hyeon ; et
al. |
August 23, 2001 |
Method of compensating for pattern dimension variation caused by
re-scattered electron beam in electron beam lithography
Abstract
The present invention relates to electron beam lithography, and
is directed to a method of compensating for pattern dimension
variation caused by a re-scattered electron beam when an electron
beam resist is exposed to the electron beam. The method of
compensating for pattern dimension variation caused by a
re-scattered electron beam comprises the steps of: dividing
original exposure pattens into square sections; obtaining a dose of
supplemental exposure to the re-scattered electron beam; and
compensation-exposing the electron beam resist so that the
supplemental exposure dose may be the same for all sections.
According to the present invention, the pattern dimension variation
can be compensated for a re-scattering effect of the electron beam,
thereby uniformly forming a fine pattern width of a more
highly-integrated circuit.
Inventors: |
Choi, Ji-hyeon; (Seoul,
KR) ; Ki, Won-tai; (Seoul, KR) |
Correspondence
Address: |
Steven M. Mills, Esq.
Samuels, Gauthier & Stevens LLP
225 Franklin Street
Boston
MA
02110
US
|
Assignee: |
Samsung Electronics Co.,
Ltd.
|
Family ID: |
19638049 |
Appl. No.: |
09/758708 |
Filed: |
January 11, 2001 |
Current U.S.
Class: |
430/30 ; 430/296;
430/942 |
Current CPC
Class: |
B82Y 40/00 20130101;
Y10S 430/143 20130101; B82Y 10/00 20130101; H01J 37/3174 20130101;
G03F 1/78 20130101 |
Class at
Publication: |
430/30 ; 430/296;
430/942 |
International
Class: |
G03F 009/00; G03C
005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 12, 2000 |
KR |
00.1337 |
Claims
What is claimed is:
1. A method of compensating for pattern dimension variation caused
by a re-scattered electron beam when an electron beam resist is
exposed to the electron beam at predetermined exposure patterns,
the method comprising: dividing the predetermined exposure patterns
into square sections; determining a dose of supplemental exposure
to the re-scattered electron beam when adjacent sections are
exposed, for each section; determining a compensation exposure dose
for each section by deducting the supplemental exposure dose of
each section from a predetermined reference value; and
compensation-exposing the electron beam resist according to the
compensation exposure dose of each section.
2. The method of compensating for pattern dimension variation
caused by a re-scattered electron beam according to claim 1,
wherein the step of determining the supplemental exposure dose for
each section comprises: obtaining an exposure pattern density of
each section; and obtaining the supplemental exposure dose for each
section according to the relationship: 2 i , j = x = - y = - D i +
x , j + y - x 2 + y 2 2 wherein .delta..sub.i,j is the supplemental
exposure dose of a section with x-coordinate i and y-coordinate j,
and .xi. is a re-scattering range, and D.sub.i,j is an exposure
pattern density of a section with x-coordinate i and y-coordinate
j.
3. The method of compensating for pattern dimension variation
caused by a re-scattered electron beam according to claim 1,
wherein the predetermined reference value is determined as the
largest value among the determined supplemental exposure dose for
all sections.
4. The method of compensating for pattern dimension variation
caused by a re-scattered electron beam according to claim 1,
wherein the step of compensation-exposing comprises the step of
compensation-exposing the electron beam resist according to
predetermined compensation exposure patterns according to the
compensation exposure dose for each section.
5. The method of compensating for pattern dimension variation
caused by a re-scattered electron beam according to claim 4,
wherein the compensation exposure patterns comprise parallel line
patterns having widths proportional to the compensation exposure
dose.
6. The method of compensating for pattern dimension variation
caused by a re-scattered electron beam according to claim 4,
wherein the compensation exposure patterns comprise a number of
square areas proportional to the compensation exposure dose of each
section divided into predetermined square areas.
7. The method of compensating for pattern dimension variation
caused by a re-scattered electron beam according to claim 4,
wherein the spot of the electron beam on the surface of the
electron beam resist is sufficiently widened when the electron beam
resist is compensation-exposed according to the compensation
exposure patterns that the compensation exposure patterns are not
developed on the electron beam resist.
8. A recording medium recorded on which a program for obtaining
compensation exposure data for compensating for pattern dimension
variation caused by a re-scattered electron beam when an electron
beam resist is exposed to the electron beam with predetermined
exposure patterns, is recorded, the program comprising: a program
module for dividing the predetermined exposure pattens into square
sections and determining a dose of supplemental exposure to the
re-scattered electron beam when adjacent sections are exposed, for
each section; a program module for determining a compensation
exposure dose for each section by deducting the supplemental
exposure dose of each section from a predetermined reference value;
and a program module for setting-up compensation exposure patterns
for each section with predetermined compensation exposure patterns
so as to expose an area proportional to the compensation exposure
dose for each section.
9. The recording medium according to claim 8, wherein the program
module for determining the supplemental exposure dose of each
section comprises: a sub-program module for obtaining an exposure
pattern density of each section; and a sub-program module for
obtaining the supplemental exposure dose of each section according
to the relationship: 3 i , j = x = - y = - D i + x , j + y - x 2 +
y 2 2 wherein .delta..sub.i,j is a supplemental exposure dose of a
section with x-coordinate i and y-coordinate j, and .xi. is a
re-scattering range, and D.sub.i,j is an exposure pattern density
of a section with x-coordinate i and y-coordinate j.
10. The recording medium according to claim 8, wherein the
predetermined reference value is determined as the largest value
among the supplemental exposure doses for all sections.
11. The recording medium according to claim 8, wherein the
compensation exposure patterns comprise parallel line patterns
having widths proportional to the compensation exposure dose.
12. The recording medium according to claim 8, wherein the
compensation exposure patterns comprise a number of square areas
proportional to the compensation exposure dose of each section
divided into predetermined square areas.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to electron beam lithography,
and more particularly, to a method of compensating for pattern
dimension variation caused by a re-scattering effect of the
electron beam occurring when a resist is exposed to the electron
beam.
[0003] 2. Description of the Related Art
[0004] Electron beam lithography is a technique used in patterning
a material layer formed on a substrate in a desired pattern. This
entails the process of coating an electron beam resist on a
material layer; writing a desired pattern with an electron beam
(referred to in the art as an "exposure"); developing the electron
beam resist; and etching the material layer by using the electron
beam resist pattern formed using the desired pattern as a mask.
Electron beam lithography can be used to form a predetermined
material layer pattern directly forming an integrated circuit on
the substrate, however, in general, electron beam lithography is
used to fabricate a photomask for use in photolithography.
[0005] Referring to FIG. 1, the process for fabricating the
photomask will be described in greater detail. The process
comprises the steps of: coating an electron beam resist 130 on an
opaque film 120 (in the case of a phase shift mask, a phase
shifting layer is available, hereinafter described simply as an
opaque film) formed on a transparent substrate 110; writing a
desired pattern with an electron beam 150; developing the electron
beam resist 130 by using a difference of solubility depending on
writing of the electron beam; and etching the opaque film 120 by
using the formed resist pattern as a mask.
[0006] However, the electron beam 150 does not only expose the
desired portion of the electron beam resist 130, as the electron
beam 150 is reflected on the surface of the opaque film 120 or
scattered by collisions with atoms of a resist material in the
electron beam resist 130 as marked 170 in FIG. 1. Also, the
electron beam 150 is reflected in the electron beam resist 130 or
on the surface of the electron beam resist 130 and at the lower
plane of an objective lens 140 of an electron beam writer and, as a
consequence, the electron beam 150 exposes an undesired portion of
the electron beam resist 130 as marked 160 in FIG. 1.
[0007] A quantity (a dose) by which the electron beam resist 130 is
exposed an extra amount by scattering of the electron beam 150 as
described above, is shown in FIG. 2. As shown in FIG. 2, the
electron beam resist can be additionally exposed from a region in
which a pattern is written with the electron beam, that is, from an
edge of the pattern to a maximum distance of 10 cm. Close to the
edge of the pattern, the dose can be as high as 25% of the original
exposure dose. In FIG. 2, an additional exposure 210 affecting from
the region in which a pattern is written with the electron beam, to
approximately 10 .mu.m, is caused by forward scattering and
backward scattering of the electron beam indicated by reference
numeral 170 in FIG. 1, and an additional exposure 220 affecting to
approximately 10 cm is caused by re-scattering of the electron beam
indicated by reference numeral 160 in FIG. 1. In conclusion, these
additional exposures deteriorate the accuracy of the opaque film
pattern, and cause a critical dimension (CD) error. The pattern
dimension variation caused by the former additional exposure 210 is
referred to as a proximity effect, and the pattern dimension
variation caused by the latter additional exposure 220 is referred
to as a re-scattering effect (multiple scattering effect or a
fogging effect) of the electron beam.
[0008] The re-scattering effect of the electron beam affects a wide
range (Considering the integration of a current integrated circuit,
10 cm is a very wide range.), and since a dose caused by the
additional exposure 220 is relatively small, the effect has not
been ascertained, and no compensation method is well-known.
However, the pattern dimension variation of the photomask caused by
the re-scattering effect of the electron beam is estimated to be
about 10.about.20 nm when an electron beam dose is 8 .mu.
C/cm.sup.2 at an accelerating voltage of 10 keV, and the pattern
dimension variation of the photomask greatly affects the
manufacture of more highly-integrated circuits.
[0009] On the other hand, the re-scattering effect of the electron
beam is introduced, and a method for forming the lower plane of the
objective lens in which the re-scattered electron beam is
reflected, of a material with a low atomic number, as a method for
reducing this effect is disclosed in, Norio Saitou et al.,
"Multiple Scattered E-beam Effect in Electron Beam Lithography",
SPIE Vol. 1465, pp.185 - p.191, 1991. That is, it is reported in
the paper that an additional dose caused by the re-scattering
effect of the electron beam when the lower plane of the objective
lens is formed of copper, aluminum, and carbon, respectively, was
measured, and the re-scattering effect of the electron beam was
lowest when carbon was adopted. However, it is shown in FIG. 2 that
the re-scattering effect is not remarkably reduced even if carbon
is adopted. In FIG. 2, the chart of symbol ".largecircle." applies
to the case where aluminum is adopted, and the chart of symbol
".quadrature." applies to the case where carbon is adopted.
[0010] Also, a method for reducing the re-scattering effect by
absorbing the re-scattered electron beam by attaching an absorber
plate in which a honeycomb groove is formed at the lower plane of
the objective lens, is disclosed in Naoharu Shimomura et al.,
"Reduction of Fogging Effect caused by Scattered Electron in an
Electron Beam System", SPIE Vol. 3748, pp.125 - p.132, 1999.
However, it is also not possible for all re-scattered electrons to
be absorbed by this method, and there is a limitation in reducing
the re-scattering effect.
SUMMARY OF THE INVENTION
[0011] To address the above limitation, it is an object of the
present invention to provide a method of compensating for pattern
dimension variation caused by a re-scattering effect of an electron
beam.
[0012] Accordingly, to achieve the above object, there is provided
a method of compensating for pattern dimension variation caused by
a re-scattered electron beam, the method comprising the steps of:
dividing original exposure patterns into square sections;
determining a dose of additional exposure (referred to herein as a
"supplemental exposure dose") to the re-scattered electron beam for
each section; and compensating the electron beam resist so that the
supplemental exposure dose may be the same for all sections. That
is, the method of compensating for pattern dimension variation
caused by a re-scattered electron beam comprises the steps of:
dividing original exposure pattens into square sections;
determining a dose of supplemental exposure to the re-scattered
electron beam when adjacent sections are exposed, for each section;
determining a compensation exposure dose for each section by
deducting supplemental exposure doses of each section from a
predetermined reference value; and compensation-exposing the
electron beam resist according to the compensation exposure dose of
each section.
[0013] The method of compensating for pattern dimension variation
caused by a re-scattering effect of an electron beam according to
the present invention can be provided in the form of a recording
medium on which a program to be read and performed by a commercial
computer is recorded. That is, a recording medium on which a
program for obtaining compensation exposure data for compensating
pattern dimension variation is recorded includes a program module
for dividing original exposure patterns into square sections and
determining a dose of supplemental exposure to the re-scattered
electron beam when adjacent sections are exposed, for each section,
a program module for determining a compensation exposure dose for
each section by deducting the supplemental exposure dose of each
section from a predetermined reference value, and a program module
for setting-up compensation exposure patterns for each section with
predetermined compensation exposure patterns so as to expose an
area proportional to the compensation exposure dose for each
section.
[0014] According to the present invention, pattern dimension
variation caused by a re-scattering effect of an electron beam can
be compensated for, thereby uniformly forming a fine pattern of a
more highly-integrated circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The above object and advantages of the present invention
will become more apparent by describing in detail preferred
embodiments thereof with reference to the attached drawings in
which:
[0016] FIG. 1 is a sectional view illustrating a scattering
phenomenon of an electron beam when the electron beam is incident
on an electron beam resist;
[0017] FIG. 2 is a graph of dose of supplemental exposure to a
scattered electron beam versus distance from the edge of a
pattern;
[0018] FIG. 3 is a flow chart illustrating steps of compensating
for pattern dimension variation caused by a re-scattered electron
beam, according to an embodiment of the present invention;
[0019] FIG. 4 is a layout diagram illustrating steps of dividing
predetermined exposure patterns into sections according to an
embodiment of the present invention;
[0020] FIG. 5 is a graph illustrating the manner in which
compensation exposure dose to compensate for pattern dimension
variation caused by a re-scattered electron beam is determined,
according to an embodiment of the present invention;
[0021] FIG. 6 and FIG. 7 illustrate examples of compensation
exposure patterns according to an embodiment of the present
invention;
[0022] FIG. 8 illustrates the size of an electron beam spot when
compensation exposing according to an embodiment of the present
invention;
[0023] FIG. 9 is a layout diagram illustrating exposure patterns
used for an experiment in compensating for pattern dimension
variation caused by the re-scattered electron beam, according to an
embodiment of the present invention;
[0024] FIG. 10 and FIG. 11 are graphs of a line width before
compensating for pattern dimension variation and a line width after
compensating for pattern dimension variation according to the
present invention, versus distance from the edge of a pattern,
respectively.
DETAILED DESCRIPTION OF THE INVENTION
[0025] FIG. 3 is a flow chart illustrating steps of compensating
for pattern dimension variation caused by a re-scattered electron
beam, according to the present invention. First, an electron beam
resist is exposed to an electron beam according to predetermined
exposure patterns (step 310). Referring back to FIG. 1, an electron
beam resist 130 is coated on an opaque film 120 formed on a
transparent substrate 110, and a desired pattern is written with
the electron beam. In other words, the electron beam exposure of
the step 310 corresponds to a general exposure step, and here, a
region not to be exposed to the electron beam is additionally
exposed. Here, the desired pattern, for example, may be
predetermined material layer patterns as shown in FIG. 4, and the
layout of the desired pattern is converted into data form suitable
for an electron beam exposure, and is supplied to an electron beam
writer. In FIG. 4, the material layer patterns to be actually
formed by a follow-up photolithographic process correspond to
oblique-lined portions, and a portion exposed by the electron beam
corresponds to the oblique-lined portions of FIG. 4 when a
photoresist to be used in the follow-up photolithographic process
is a negative-type photoresist and in case of a positive-type
photoresist, the portion corresponds to a portion excluding the
oblique-lined portions of FIG. 4. Hereinafter, for convenience of
explanation, it is assumed that the resists to be used as the
electron beam resist and in the follow-up photolithographic process
are both positive-type resists.
[0026] Returning to FIG. 3, during step 320 exposure patterns, such
as those shown in FIG. 4, are divided into square sections 410. In
step 330, a supplemental exposure dose caused by the re-scattered
electron beam is calculated when adjacent sections are exposed, for
each section 410. The step of calculating the supplemental exposure
dose for each section 410 can be subdivided as described below.
[0027] First, an exposure pattern density is calculated for each
section. As described above, in a case where the photoresist to be
used in the follow-up photolithographic process is a positive-type
photoresist, the portion exposed by the electron beam to actually
fabricate the photomask corresponds to a portion excluding the
oblique-lined portions of FIG. 4, and in a case where no
oblique-lined portions are included in a section 410, the exposure
pattern density of the section is 1, and on the contrary, in a case
where a section is formed of the oblique-lined portions, the
exposure pattern density of the section is 0. That is, the exposure
pattern density of each section is the fraction of the area of a
section not occupied by oblique-lined portions.
[0028] The supplemental exposure doses are calculated for each
section using the following equation after the exposure pattern
density is calculated for each section: 1 i , j = x = - y = - D i +
x , j + y - x 2 + y 2 2 ( 1 )
[0029] wherein .delta..sub.i,j is a supplemental exposure dose of a
section with x-coordinate i and y-coordinate j, .xi. is a
re-scattering range, and D.sub.i,j is an exposure pattern density
of the section with x-coordinate i and y-coordinate j.
[0030] The above equation 1 will be described in detail below. For
example, in a case where the re-scattered electron beam affects the
edge of a window 420 indicated by a thick solid line when a portion
of the most centered section 410 in FIG. 4 is exposed, the
re-scattering range .xi. is 2, and in order to calculate the
supplemental exposure dose of the most centered section 410, the
supplemental exposure doses caused by the re-scattering effect of
the electron beam when each section contained in the window 420 is
exposed, are added. Also, the supplemental exposure dose of each
section caused by the re-scattering effect when exposing are
proportional to the exposure pattern density of the section and
inversely proportional to the distance from the most centered
section 410.
[0031] Returning to FIG. 3, after obtaining the supplemental
exposure doses with respect to all sections, compensation exposure
doses are calculated for each section (step 340). The compensation
exposure doses are doses that compensate such that the supplemental
exposure dose caused by the re-scattering effect of the electron
beam may be constant with respect to all sections. The supplemental
exposure dose of each section are deducted from a predetermined
reference value. Here, the predetermined reference value may be a
maximum value of the supplemental exposure dose with respect to all
sections, calculated in the step 330, or the predetermined
reference value may be otherwise appropriately designated. That is,
as shown in FIG. 2, since the supplemental exposure doses caused by
the re-scattering effect of the electron beam are approximately
less than 6% when carbon is used for the lower plane material of an
objective lens, a maximum supplemental exposure dose may be set up
as 6% of the original exposure (step 310) dose. Meanwhile, in a
case where the reference value is the maximum value of the
supplemental exposure dose, as shown in FIG. 5, the compensation
exposure dose of a section x is obtained by deducting the
supplemental exposure doses of the section from the maximum
supplemental exposure dose 510.
[0032] Subsequently, a compensation exposure is performed according
to the compensation exposure dose obtained for each section. In
detail, a predetermined compensation exposure pattern is selected
according to the compensation exposure dose for each section (step
350), and compensation exposure data are established by gathering
the selected compensation exposure pattern for each section, and
the electron beam resist is exposed by the electron beam according
to these compensation exposure data (step 360).
[0033] In FIGS. 6 and 7, which illustrate examples of compensation
exposure patterns which can be selected, oblique-lined portions 603
and 703 of FIGS. 6 and 7 denote portions compensation-exposed by
the electron beam. In the compensation exposure patterns, portions
exposed according to the compensation exposure dose of each section
become stepwise broad, and the compensation exposure patterns of
FIG. 6 are classified into 11 stages, and those of FIG. 7 into 10
stages. The selection of the compensation exposure patterns of
FIGS. 6 and 7 according to the compensation exposure dose for each
section is done according to tables 1 and 2, respectively: In
tables 1 and 2, .delta.'.sub.i,j is a compensation exposure dose of
a section with x-coordinate i and y-coordinate j, and
.delta..sub.max is the above-mentioned maximum supplemental
exposure dose.
1TABLE 1 Open ratio of Compensation compensation exposure exposure
Compensation exposure dose pattern (%) pattern .delta.'.sub.i,j
< 0.05 .delta..sub.max 0 610 0.05 .delta..sub.max .ltoreq.
.delta.'.sub.i,j < 0.15 .delta..sub.max 10 615 0.15
.delta..sub.max .ltoreq. .delta.'.sub.i,j < 0.25 .delta..sub.max
20 620 0.25 .delta..sub.max .ltoreq. .delta.'.sub.i,j < 0.35
.delta..sub.max 30 625 0.35 .delta..sub.max .ltoreq.
.delta.'.sub.i,j < 0.45 .delta..sub.max 40 630 0.45
.delta..sub.max .ltoreq. .delta.'.sub.i,j < 0.55 .delta..sub.max
50 635 0.55 .delta..sub.max .ltoreq. .delta.'.sub.i,j < 0.65
.delta..sub.max 60 640 0.65 .delta..sub.max .ltoreq.
.delta.'.sub.i,j < 0.75 .delta..sub.max 70 645 0.75
.delta..sub.max .ltoreq. .delta.'.sub.i,j < 0.85 .delta..sub.max
80 650 0.85 .delta..sub.max .ltoreq. .delta.'.sub.i,j < 0.95
.delta..sub.max 90 655 0.95 .delta..sub.max .ltoreq.
.delta.'.sub.i,j < 1.0 .delta..sub.max 100 660
[0034]
2TABLE 2 Open ratio of Compensation compensation exposure exposure
Compensation exposure dose pattern pattern .delta.'.sub.i,j <
0.5 0 710 0.05 .delta..sub.max .ltoreq. .delta.'.sub.i,j < 0.16
.delta..sub.max 1/9 715 0.16 .delta..sub.max .ltoreq.
.delta.'.sub.i,j < 0.27 .delta..sub.max 2/9 720 0.27
.delta..sub.max .ltoreq. .delta.'.sub.i,j < 0.38 .delta..sub.max
3/9 725 0.38 .delta..sub.max .ltoreq. .delta.'.sub.i,j < 0.49
.delta..sub.max 4/9 730 0.49 .delta..sub.max .ltoreq.
.delta.'.sub.i,j < 0.60 .delta..sub.max 5/9 735 0.60
.delta..sub.max .ltoreq. .delta.'.sub.i,j < 0.71 .delta..sub.max
6/9 740 0.71 .delta..sub.max .ltoreq. .delta.'.sub.i,j < 0.82
.delta..sub.max 7/9 745 0.82 .delta..sub.max .ltoreq.
.delta.'.sub.i,j < 0.93 .delta..sub.max 8/9 750 0.93
.delta..sub.max .ltoreq. .delta.'.sub.i,j < 1.0 .delta..sub.max
1 755
[0035] The maximum dose during compensation-exposing (step 360) is
preferably a sufficiently small value (for example, less than 6%)
compared to that at the original exposure (step 310), preferably,
however, the compensation exposure time is comparatively short, for
example less than 30 minutes (exposure time at the original
exposure is generally several hours.), so that the compensation
exposure patterns of FIGS. 6 and 7 are not actually formed on the
photomask.
[0036] Also, as shown in FIG. 8, preferably, a spot size 810 of the
electron beam when compensation-exposing is several times greater
than a line width of the compensation exposure patterns 603 so that
the spot 810 overlaps unexposed portions 605.
[0037] When the compensation exposure is performed in this way, the
supplemental exposure dose caused by the re-scattering effect of
the electron beam at each section becomes constant, thereby the
pattern dimension variation of the photomask is prevented.
[0038] In the above-mentioned embodiment, the method according to
the present invention is applied to the fabrication of the
photomask. However, in alternative embodiments, the method of the
present invention can be applied to the patterning of a
predetermined material layer formed on a substrate so as to
construct an integrated circuit.
[0039] Hereinafter, experimental examples in which the pattern line
width variation when the compensation exposure is performed
according to the method of the present invention will be described,
in comparison to an example in which the compensation exposure is
not performed.
[0040] First, as shown in FIG. 9, an exposure pattern 910 of a 70
mm.times.70 mm size in which a test pattern 940, in which linear
patterns 950 having a predetermined line width are arranged is
formed, is provided. In FIG. 9, oblique-lined regions 930 and 950
correspond to an opaque film pattern, and a blank region 920
corresponds to a portion exposed to the electron beam.
[0041] FIG. 10 is a graph in which a line width of the test pattern
910 (see FIG. 9) is measured, following a general exposure to the
electron beam (step 310). In the graph of FIG. 10, the horizontal
axis denotes distance to an unexposed area 930 from a boundary
between a 100% exposed area (the non-oblique-lined area 920 of FIG.
9) and the unexposed area (the oblique-lined area 930), and the
vertical axis denotes a measured line width of the test pattern.
Reference numeral 1010 denotes a line width when exposing at an
accelerating voltage of 50 keV and a dose of 32 .mu. C/cm.sup.2,
and reference numeral 1020 denotes a line width when exposing at an
accelerating voltage of 10 keV and a dose of 8 .mu. C/cm.sup.2.
Also, reference numeral 1030 denotes a line width when exposing at
an accelerating voltage of 10 keV and a dose of 8 .mu. C/cm.sup.2
and converting the 100% exposed area 920 of FIG. 9 into an area
having an average exposure pattern density of 70% with a similar
level to that of a conventional integrated circuit device.
[0042] Referring to FIG. 10, variation widths of line widths, that
is, differences in a maximum line width and a minimum line width
are 53 nm(1010), 15 nm(1020), and 10 nm(1030), respectively. Also,
the variation of the line widths including the variation of the
line widths at the test pattern 940 of the 100% exposed area 920,
are measured as 87 nm(1010), 22 nm(1020), and 15 nm(1030),
respectively.
[0043] Following this, the compensation exposure was performed
according to the method of compensating for pattern dimension
variation caused by the re-scattered electron beam of the present
invention. That is, the exposure pattern 910 of, for example, 70
nm.times.70 nm of FIG. 9 is divided into the sections of, for
example, 1 mm.times.1 mm, and the exposure pattern density and the
supplemental exposure dose with respect to each section are
determined.
[0044] Here, the re-scattering range .xi. is set up as 8 mm, and
the maximum supplemental exposure dose value .delta..sub.max is set
up as 3.5% of the original exposure dose. After obtaining the
compensation exposure dose for each section, the line widths of the
test pattern formed by the compensation exposure according to the
compensation exposure doses are measured.
[0045] Referring to FIG. 11, a graph illustrating the above
measured results, the horizontal and vertical axes are the same as
those of FIG. 10, and reference numerals 1110, 1120, and 1130
denote measured line widths corresponding to 1010,1020, and 1030 of
FIG. 10, respectively. In FIG. 11, in the cases of 1110, 1120, and
1130, the variation widths of the line widths are remarkably
reduced compared to those of FIG. 10. The variation widths of the
line width including the variation of the line widths at the test
pattern 940 of the 100% exposed area 920, are measured as 23
nm(1110), 6 nm(1120), and 4 nm(1130), respectively.
[0046] Meanwhile, the method of compensating for a pattern
dimension variation caused by the re-scattered electron beam of the
present invention may be realized by a software program, and the
program may be provided on computer readable media. Therefore, the
method of compensating for pattern dimension variation of the
present invention can be performed by a general-purpose digital
computer. The media can include storage media such as magnetic
media (for example, a read-only memory (ROM), a floppy disk, and a
hard disk etc.), optical media (for example, CD-ROM and a digital
versatile-disc (DVD) etc.), and carrier waves (for example,
transfer via Internet).
[0047] In general, the exposure patterns as shown in FIG. 4 are
converted into exposure data for writing with an electron beam and
supplied to the electron beam writer, the compensation exposure
patterns of FIGS. 6 or 7 obtained by the method of the present
invention are also supplied to the electron beam writer as the
compensation exposure data. In particular, all steps of the method
of the present invention, that is, the steps of: dividing original
exposure patterns (FIG. 4) into predetermined-size sections and
determining a dose of supplemental exposure by the re-scattered
electron beam for each section; obtaining a compensation exposure
dose for each section; and selecting predetermined compensation
exposure patterns according to the compensation exposure dose for
each section and establishing compensation exposure data with
respect to entire exposure patterns, can be essentially realized by
modules of a computer program, and it is also preferable for the
steps to be realized by the computer program. Here, codes and code
segments of a functional program, in which each program module is
actually coded, can be readily implemented by a skilled computer
programmer.
[0048] As described above, according to the present invention, the
exposure patterns are preferably divided into square sections, and
the supplemental exposure dose caused by the re-scattering effect
of the electron beam and the compensation exposure dose are
determined for each section. The electron beam resist is
compensation-exposed according to predetermined compensation
exposure patterns according to the compensation exposure dose for
each section, thereby minimizing the pattern dimension variation
caused by the re-scattering effect of the electron beam.
[0049] The method of compensating for pattern dimension variation
caused by the re-scattering effect of the electron beam of the
present invention can be realized by a computer program and
performed in a general-purpose digital computer, thereby minimizing
the pattern dimension variation caused by the re-scattered electron
beam in an electron beam exposure system.
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