U.S. patent application number 13/102836 was filed with the patent office on 2011-10-06 for photomask using separated exposure technique, method of fabricating photomask, and apparatus for fabricating photomask by using the method.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Seong-woon Choi, Hak-seung HAN, Byung-gook Kim, Hee-bom Kim, Sung-ho Park.
Application Number | 20110244376 13/102836 |
Document ID | / |
Family ID | 38559503 |
Filed Date | 2011-10-06 |
United States Patent
Application |
20110244376 |
Kind Code |
A1 |
HAN; Hak-seung ; et
al. |
October 6, 2011 |
PHOTOMASK USING SEPARATED EXPOSURE TECHNIQUE, METHOD OF FABRICATING
PHOTOMASK, AND APPARATUS FOR FABRICATING PHOTOMASK BY USING THE
METHOD
Abstract
A method of fabricating a photomask may include forming a
light-shielding layer and a first resist film on a substrate,
forming a first resist pattern by exposing first exposed regions of
the first resist film to a first exposure source that may have a
first energy, forming a first light shielding pattern by etching
the selectively exposed light-shielding layer by using the first
resist pattern as an etching mask, removing the first resist
pattern, forming a second resist film on the first light-shielding
layer, exposing second exposed regions of the second resist film
that may have a desired pattern shape to a second exposure source
that may have a second energy, forming a second light shielding
pattern by etching the selectively exposed first light shielding
pattern by using the second resist pattern as an etching mask, and
removing the second resist pattern.
Inventors: |
HAN; Hak-seung; (Yongin-si,
KR) ; Choi; Seong-woon; (Suwon-si, KR) ; Kim;
Byung-gook; (Suwon-si, KR) ; Kim; Hee-bom;
(Suwon-si, KR) ; Park; Sung-ho; (Seoul,
KR) |
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Suwon-si
KR
|
Family ID: |
38559503 |
Appl. No.: |
13/102836 |
Filed: |
May 6, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11730454 |
Apr 2, 2007 |
7939223 |
|
|
13102836 |
|
|
|
|
Current U.S.
Class: |
430/5 ;
355/53 |
Current CPC
Class: |
G03F 1/68 20130101; G03F
1/36 20130101; G03F 1/76 20130101 |
Class at
Publication: |
430/5 ;
355/53 |
International
Class: |
G03F 1/00 20060101
G03F001/00; G03B 27/42 20060101 G03B027/42 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 4, 2006 |
KR |
10-2006-0030588 |
Claims
1.-13. (canceled)
14. An apparatus for fabricating a photomask, comprising: a vacuum
chamber; a transfer chamber including a transfer arm; an arranging
chamber for arranging the photomasks; a first exposure chamber for
exposing surfaces of the photomasks to a first exposure source
having a first energy; and a second exposure chamber for exposing
the surfaces of the photomasks to a second exposure source having a
second energy.
15. The apparatus as claimed in claim 14, wherein the first
exposure source is an electron beam, and the second exposure source
is an electron beam or light.
16. The apparatus as claimed in claim 14, wherein the first
exposure source emits higher energy than the second exposure
source.
17. The apparatus as claimed in claim 14, wherein the first
exposure source emits energy that has an acceleration voltage
higher than that of the second energy.
18. (canceled)
19. (canceled)
20. A photomask, fabricated by the apparatus for fabricating a
photomask according to claim 14.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This is a divisional application based on pending
application Ser. No. 11/730,454, filed Apr. 2, 2007, the entire
contents of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method and apparatus for
fabricating a photomask. More particularly, the present invention
relates to a method and apparatus for fabricating a photomask which
may form a minute pattern by exposing the periphery of a boundary
line between patterns to a high energy electron beam or light
beam.
[0004] 2. Description of the Related Art
[0005] High-performance semiconductor devices necessarily operate
at high speed, process many signals, and have low power consumption
and small size together with high integration. In order to operate
one semiconductor chip at high speed, the power consumption of the
semiconductor chip may preferably be low. In order to reduce the
power consumption of the semiconductor chip, the size of each unit
element one of the semiconductor chip may be reduced. Therefore, in
order to achieve high-integration in semiconductor devices, unit
elements may be minutely formed, which may largely depend on the
capabilities of the patterning and photolithography techniques. The
photolithography process, in turn, may depend on the quality of the
photomask used in the process. A high-quality photomask may allow
the photolithography process to be implemented at a higher level of
performance, which may render it possible to obtain
highly-integrated semiconductor devices. That is, the fabrication
of a high-quality photomask having fine patterns may be important
for manufacturing highly-integrated semiconductor elements.
SUMMARY OF THE INVENTION
[0006] It is therefore a feature of an embodiment of the present
invention to provide a method and apparatus for fabricating a
photomask which substantially overcome one or more of the problems
due to the limitations and disadvantages of the related art.
[0007] It is therefore a feature of an embodiment of the present
invention to provide a method and apparatus for fabricating a
photomask which may reduce the adverse effects of a scattering
phenomenon, may reduce the time required for exposure, and may form
a desired minute pattern.
[0008] At least one of the above and other features and advantages
of the present invention may be realized by providing a photomask
fabricating method, which may include preparing a light-shielding
layer and a resist film that may be formed on a substrate, forming
a first resist pattern by exposing first exposed regions of the
first resist film adjacent to patterns that may exist in a first
pattern density region to a first exposure source that may have a
first energy, so as to selectively expose the light-shielding
layer, forming a first light shielding pattern by etching the
selectively exposed light-shielding layer by utilizing the first
resist pattern as an etching mask, removing the first resist
pattern, forming a second resist film that may be on the first
light-shielding layer, forming a second resist pattern by exposing
second exposed regions of the second resist film, except for the
first exposed regions of the first pattern region, and a second
pattern region to a second exposure source that may have a second
energy, forming a second light shielding pattern by etching the
selectively exposed first light shielding pattern by utilizing the
second resist pattern as a mask for etching, and removing the
second resist pattern.
[0009] The first pattern region may have a pattern density lower
than that of the second pattern region. In the first pattern
region, a gap between the patterns may be equal to or more than
about twice a line width of the pattern, and in the second pattern
region, a gap between the patterns may be equal to or less than
about twice a line width of the pattern. The first energy may be
higher than the second energy. The first exposure source may be an
electron beam, and the second exposure source may be an electron
beam or light. The first energy may have an acceleration voltage
higher than that of the second energy. The first energy may have an
acceleration voltage of about 50 KeV, and the second energy has an
acceleration voltage of about 10 KeV.
[0010] At least one of the above and other features and advantages
of the present invention may be realized by providing a photomask
fabricating method, which may include preparing a light-shielding
layer and a resist film that may be formed on a substrate, exposing
first exposed regions of the resist film that may be adjacent to
patterns in a first pattern region to a first exposure source that
may have a first energy, exposing second exposed regions of the
resist film, except for the first exposed regions of the first
pattern region, and a second pattern region to a second exposure
source that may have a second energy, forming a resist pattern by
developing the resist film to selectively expose the
light-shielding layer, forming a light shielding pattern by etching
the selectively exposed light-shielding layer by utilizing the
resist pattern as a mask for etching, and removing the resist
pattern.
[0011] At least one of the above and other features and advantages
of the present invention may be realized by providing a photomask
fabricating apparatus, which may include a vacuum chamber, a
transfer chamber that may include a transfer arm, an arranging
chamber for arranging the photomasks, a first exposure chamber for
exposing first regions of surfaces of the photomasks to a first
exposure source having a first energy, and a second exposure
chamber for exposing the surfaces of the photomasks to a second
exposure source having a second energy.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The above and other features and advantages of the present
invention will become more apparent to those of ordinary skill in
the art by describing in detail exemplary embodiments thereof with
reference to the attached drawings, in which:
[0013] FIG. 1 illustrates an enlarged schematic plan view of a
portion of a photomask for explaining stages in a method of
fabricating a photomask according to an embodiment of the present
invention;
[0014] FIG. 2 illustrates an enlarged schematic plan view of a
portion of a photomask for explaining stages of the method of
fabricating a photomask according to the embodiment of the present
invention in greater detail;
[0015] FIGS. 3A and 3B illustrate graphs of the completion results
for photomasks fabricated by a method of fabricating a photomask
according to an embodiment of the present invention;
[0016] FIGS. 4A to 4H illustrate longitudinal sectional views of
stages of a method of fabricating a photomask according to an
embodiment of the present invention;
[0017] FIGS. 5A to 5E illustrate longitudinal sectional schematic
views of stages of a method of fabricating a photomask according to
another embodiment of the present invention;
[0018] FIGS. 6A and 6B illustrate diagrams of an apparatus for
fabricating a photomask according to an embodiment of the present
invention; and
[0019] FIGS. 7A and 7B illustrate flow charts showing stages of a
method of fabricating a photomask by using an apparatus for
fabricating a photomask according to an embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Korean Patent Application No. 10-2006-0030588 filed on Apr.
4, 2006, in the Korean Intellectual Property Office, and entitled:
"Photomask Using Separated Exposure Technique, Method of
Fabricating Photomask, and Apparatus for Fabricating Photomask by
Using the Method," is incorporated by reference herein in its
entirety.
[0021] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings, in which
exemplary embodiments of the invention are illustrated. The
invention may, however, be embodied in different forms and should
not be construed as limited to the embodiments set forth herein.
Rather, these embodiments are provided so that this disclosure will
be thorough and complete, and will fully convey the scope of the
invention to those skilled in the art.
[0022] In the drawing figures, the dimensions of layers and regions
may be exaggerated for clarity of illustration. It will also be
understood that when a layer or element is referred to as being
"on" another layer or substrate, it may be directly on the other
layer or substrate, or intervening layers may also be present.
Further, it will be understood that when a layer is referred to as
being "under" another layer, it may be directly under, and one or
more intervening layers may also be present. In addition, it will
also be understood that when a layer is referred to as being
"between" two layers, it may be the only layer between the two
layers, or one or more intervening layers may also be present. Like
reference numerals refer to like elements throughout.
[0023] Embodiments of the invention are described herein with
reference to cross-sectional illustrations that are schematic
illustrations of idealized embodiments of the invention. As such,
variations from the shapes of the illustrations as a result, for
example, of manufacturing techniques and/or tolerances, are to be
expected. Thus, embodiments of the invention should not be
construed as limited to the particular shapes of regions
illustrated herein but are to include deviations in shapes that
result, for example, from manufacturing. Therefore, the regions
illustrated in the drawing figures are schematic in nature and
their shapes are not intended to illustrate the actual shape of a
region of a device and are not intended to limit the scope of the
invention.
[0024] In the following description, "exposure" means to irradiate
electron beams or light onto a resist film formed on a photomask.
Electron beams may not simultaneously be irradiated onto an entire
surface of a photomask, but may be irradiated by an electron gun to
be sequentially irradiated onto minute regions of a surface of a
photomask. With electron beams, a shape of a pattern may be drawn
or written on a photomask by electron beams, rather than using a
photomask that may be exposed to electron beams. However, in order
to separately explain the cases of using electron beams and using
light, the description may appear complicated. For this reason, the
same term will be used in both cases. "Exposing" thus means to
irradiate electron beams or light onto a resist film.
[0025] In the following description, an exposure source may include
sources for either an electron beam or light. In order to
separately explain the cases of using electron beams and light, it
may be necessary to repetitively exemplify the same or similar
drawings and to repeat the description. Therefore, in order to
avoid repeating the same description and to simply explain the
technical idea of the present invention, inclusive terms will be
used.
[0026] With an electron beam, three factors that may be considered
include the size, the acceleration voltage, and the electron
density of the electron beam. Therefore, a high energy electron
beam may exist in various forms as compared to a low energy
electron beam. More specifically, the total energy of an electron
beam may become higher by raising the acceleration voltage and
adjusting the electron density to be high or low, or by maintaining
the electron density. In a high electron density state, the
acceleration voltage may be high or low. Even when a large-spot
electron beam having the same acceleration voltage and the same
electron density is irradiated onto a wide region, the energy may
increase. High energy may be understood to be high total energy. In
embodiments of the present invention, an electron beam having a
high acceleration voltage will be exemplified as a representative
example.
[0027] With light, energy may increase by using light with a short
wavelength or by increasing exposure time. In the present
invention, light with a short wavelength will be exemplified.
[0028] A photomask used in the description may include a reticule,
and the photomask may be used together with a reticule.
[0029] A region where patterns exist on a photomask may be divided
into two regions. One of the divided regions may be a region where
the pattern density is relatively low, and the other region may be
a region where the pattern density is relatively high. Here, the
pattern density represents a ratio of an area which the patterns
occupy compared to the total area. For example, the pattern may be
a portion onto which an electron beam or light is not
irradiated.
[0030] The region having a low pattern density may represent a
region where the gap between the patterns may be equal to or more
than about twice the line width of the pattern. The region having a
high pattern density may represent a region where the gap between
the patterns is equal to or less than about twice the line width of
the pattern. That is, the region having a high pattern density may
be considered as a region where many patterns are aggregated
densely like cell regions of a DRAM, and the region having a low
pattern density may be considered to be a region where patterns are
not densely aggregated.
[0031] Generally, a photomask may be patterned by being exposed to
an electron beam or light. For example, a photomask may be
completed by forming an impermeable film of chromium on a
transparent glass substrate, forming a resist film that may react
with an electron beam or light on the impermeable film, exposing a
region of the resist film that may have a desired shape to an
electron beam or light, forming a resist pattern by developing the
resist film, etching the chromium film, and removing the resist
pattern. In this case, the resist may be an electron beam (e-beam)
resist or a photoresist.
[0032] An important process among the above-mentioned processes may
be exposing the resist film to an electron beam or light, in
particular, exposing the resist film to an electron beam. An
electron beam may scatter because it has physical properties that
are unlike light. Scattering is a phenomenon in which electrons
irradiated onto an electron beam resist may not travel straight and
may be scattered in irregular directions due to collisions with
atoms of the electron beam resist or a patterned film. Scattering
in an electron beam resist may be mainly divided into forward
scattering and backward scattering. Scattering may show different
aspects according to the acceleration voltage of an irradiated
electron beam. Specifically, as the acceleration voltage becomes
higher, the effect of the forward scattering may decrease and the
effect of the backward scattering may increase. In contrast, as the
acceleration voltage becomes lower, the effect of the forward
scattering may increase and the effect of the backward scattering
may decrease. Further, as the electron density of the electron beam
becomes higher, the effect of the scattering may increase.
[0033] Therefore, it may be preferable to expose a photomask to an
electron beam having an acceleration voltage and an electron
density capable of minimizing the effect of the forward scattering
and the backward scattering. However, since patterns to be formed
on photomasks vary, the effect of scattering may vary according to
the shapes and densities of the patterns. Specifically, in a
high-density pattern, since the effect of scattered electrons at
the time when adjacent patterns are exposed may be large, it may be
preferable to radiate an electron beam having low energy, i.e., a
low acceleration voltage and a low electron density, as compared to
a low-density pattern. In the case of the low-density pattern,
e.g., an isolated pattern, since the effect of scattered electrons
is small, it may be preferable to radiate an electron beam having a
relatively high acceleration voltage or electron density.
[0034] To form a minute pattern, when the entire photomask is
exposed to electron beams having the same acceleration voltage, a
region in which the size of a pattern may be excessively large may
be generated, and even a region where a pattern is not formed may
exist. For this reason, a method of adjusting an acceleration
voltage according to the pattern density of each region may be
used. For example, the entire pattern may be divided into a mesh
form, the pattern density of each of the divided regions may be
approximately calculated, and an acceleration voltage may be
determined on the basis of the calculated pattern density. However,
since the acceleration voltage is approximately calculated, it may
be inaccurate. Further, since various results are obtained
according to the pattern densities, acceleration voltages may vary.
When exposure is performed using an electron beam with an
acceleration voltage calculated in the above-mentioned manner,
since an inaccurate acceleration voltage may be used, it may be
difficult to form a desired pattern. Further, when various
acceleration voltages are used, it may take several minutes or more
to change the acceleration voltage. Therefore, it may take a
significant amount of time to expose one photomask.
[0035] Hereafter, methods and apparatuses for fabricating a
photomask according to embodiments of the present invention will be
described with reference to the accompanying drawings.
[0036] FIG. 1 illustrates an enlarged schematic plan view of a
portion of a photomask for explaining stages of a method of
fabricating a photomask according to an embodiment of the present
invention. FIG. 1 may be understood as illustrating a plan view of
a complete photomask, a state in which a resist pattern is formed
before completing a photomask, or a photomask pattern on computer
data.
[0037] Referring to FIG. 1(a), dark patterns 10 and clear patterns
20 may be formed in a region A of a photomask surface having a low
pattern density and a region B of the photomask surface having a
high pattern density. The dark patterns 10 may be referred to as
regions that are not exposed to an exposure source (an electron
beam or light), and the clear patterns 20 may be referred to as
regions exposed to the exposure source.
[0038] FIGS. 1(b) and 1(c) illustrate views showing representative
examples of stages of a method of applying the photomask patterns
of the present invention. In FIGS. 1(b) and 1(c), the clear
patterns 20 in the region A having the low pattern density may be
divided into two regions, that is, a first exposed region E1 and a
second exposed region E2. The first and second exposed regions E1
and E2 may be separately exposed. The second exposed region E2 may
be exposed together with the region B having the high pattern
density. In this way, the photomask pattern shown in FIG. 1(a) may
be completed. In FIGS. 1(a) to 1(c), hatched portions may represent
regions that are not exposed. The first exposed region E1 may be
exposed to an electron beam or light having higher energy than that
of an electron beam or light to which the second exposed region E2
is exposed. In other words, the second exposed region E2 may be
exposed to an electron beam or light having energy lower than that
of the electron beam or light to which the first exposed region E1
is exposed. In contrast, the first exposed region E1 may be exposed
to an electron beam or light having low energy, and the second
exposed region E2 may be exposed to an electron beam or light
having high energy. More specifically, the electron beam having the
high energy may be understood as an electron beam having a high
acceleration voltage, and the electron beam having the low energy
may be understood as an electron beam having a low acceleration
voltage. Further, light with a high energy may be understood as
light with a short wavelength, and light with a low energy may be
understood as light with a long wavelength.
[0039] Stages of a method of fabricating a photomask according to
an embodiment of the present invention may use only exposure
sources having two energy levels. The method of fabricating a
photomask may reduce the exposure time of a photomask, as compared
to a method of fabricating a photomask according to the related art
which requires the utilization of exposure sources having various
energy levels.
[0040] The first exposed region E1 in FIG. 1 is depicted to not
invade the region of the dark pattern 10, for ease of explanation.
However, in order to specifically carry out the present invention,
the first exposed region E1 may be exposed to invade a
predetermined region of the dark pattern 10. In contrast, the first
exposed region E1 may be exposed to be separate from a boundary
line between the dark pattern 10 and the clear pattern 20. That is,
an unexposed region may exist in the clear region 20.
[0041] The width W of the first exposed region E1 will be described
below in more detail.
[0042] When the first exposed region E1 is exposed to the exposure
source having high energy and the second exposed region E2 is
exposed to the exposure source having low energy, the second
exposed region E2 may include the first exposed region E1. In other
words, the first exposed region E1 may overlap the second exposed
region E2. The configuration of FIG. 1 may thus be effective to
form a photomask surface having various shapes and densities, and
in particular, to form isolated patterns.
[0043] FIGS. 2(a) to 2(c) illustrate enlarged schematic plan views
of a portion of a photomask for explaining stages in a method of
fabricating a photomask according to the present invention in more
detail.
[0044] Referring to FIGS. 2(a) to 2(c), the first exposed regions
E1 may be arranged to be adjacent to the dark patterns 10 and may
be primarily exposed (see FIG. 2(b)). Then, the second exposed
regions E2 that are not adjacent to the dark patterns 10 may be
exposed (see FIG. 2(c)). In this way, a photomask having the dark
patterns 10 with various sizes may be fabricated (see FIG. 2(a)).
In particular, first exposed regions E1 with various widths W1, W2,
and W3 may be formed. The widths W1, W2, and W3 of the first
exposed regions E1 may depend on the size of the dark pattern 10 or
the clear pattern 20. When a line-segment-shaped dark pattern is
used, the first exposed region may not be arranged at any portion
of the left side of FIG. 2(c). In the following description, the
results obtained by carrying out experiments, that is, by
completing photomasks by variously changing the widths W1, W2, and
W3 of the first exposed regions E1 according to the size of the
dark pattern 10 will be exemplified.
[0045] FIGS. 3A and 3B illustrate graphs of the results obtained by
completing photomasks by the method of fabricating a photomask
according to an embodiment of the present invention. More
specifically, FIGS. 3A and 3B graph the experimental results
obtained by measuring the line widths and edge roughness's of dark
patterns of photomasks that are completed by variably splitting the
widths of the first exposed regions. An electron beam having an
acceleration voltage of about 50 keV may be used as the exposure
source to which the first exposed regions are exposed, and an
electron beam having an acceleration voltage of about 10 keV may be
used as the exposure source to which the second exposed regions are
exposed.
[0046] FIG. 3A shows the results obtained by measuring a variation
in the line width of a dark pattern of each of the photomasks
completed by setting the widths of the first exposed regions to
about 80 nm, about 300 nm, about 1 .mu.m, about 30 .mu.m, and about
100 .mu.m. The X-axis represents the line width of the dark pattern
and the Y-axis represents linearity, that is, the difference
between the measured line width and the designed line width. Both
the line width and the linearity may be expressed as nm. It may be
preferable to obtain higher linearity, that is, to obtain an
experimental result approaching a horizontal line. In other words,
setting the first exposed regions to about 80 nm and about 300 nm
may represent preferable results as compared to the other cases,
due to their high linearity. In particular, when the designed line
width of the dark pattern is equal to or larger than about 200 nm,
very stable linearity may be obtained.
[0047] FIG. 3B shows the results obtained by measuring the edge
roughness of dark patterns of photomasks completed by setting the
widths of the first exposed regions to about 80 nm, about 1 .mu.m,
and about 30 .mu.m. The X-axis represents the line width of the
dark pattern and the Y-axis represents the range of the variation
in the line width. Both the line width and the range of the
variation in the line width may be expressed as nm. More
specifically, when the width of the first exposed region is set to
about 80 nm, the edge roughness of the dark pattern may be very
good. It may be seen that, when setting the widths of the dark
patterns to about 1 .mu.m and about 30 .mu.m, and when the line
width of the dark pattern is equal to or smaller than about 100 nm,
the line width may vary remarkably. From the experimental results
shown in FIGS. 3A and 3B, it may be seen that the most superior
result may be obtained when the width of the first exposed region
is set to about 80 nm.
[0048] However, the experimental results have been exemplified for
presenting the technical concepts of the present invention under
specific conditions. An optimized result may be obtained according
to the energy of the exposure source through various
experiments.
[0049] FIGS. 4A to 4H illustrate longitudinal sectional schematic
views of stages of a method of fabricating a photomask according to
an embodiment of the present invention.
[0050] As shown in FIG. 4A, a light-shielding layer 120 may be
formed on a substrate 110. A first resist film 130 may be formed on
the light-shielding layer 120. Then, a first exposed region of a
region A having a low pattern density of the first resist film 130
may be exposed to a first exposure source having a first energy
level.
[0051] The substrate 110 may be made of, e.g., glass, quartz,
silicon, etc.
[0052] The light-shielding layer 120 may be composed of, e.g.,
chromium, aluminum, titanium, molybdenum, ruthenium, or tantalum, a
metal alloy, a metal compound incorporating oxygen or nitrogen,
etc. The light-shielding layer 120 may preferably have excellent
adhesive strength to the glass substrate 110, a thermal expansion
coefficient that may be similar to that of the glass substrate 110,
and flexibility. The light-shielding layer 120 may be made of at
least one made of a metal material that may include, e.g.,
chromium, aluminum, titanium, molybdenum, ruthenium, or tantalum, a
metal alloy, a metal compound incorporating oxygen or nitrogen,
etc. Two or more layers of these materials may be used. Examples of
the material forming the light-shielding layer 120 may also include
compounds, e.g., chromium-aluminum alloy, metal oxide such as
chromium oxide or aluminum oxide, metal nitride such as chromium
nitride or aluminum nitride, metal oxynitride of all metallic
elements, a compound incorporating an alloy, etc. For example, the
light-shielding layer 120 having a thickness of about 2000 .ANG.
may be formed of chromium that has been deposited by sputtering.
The about 2000 .ANG. thickness of the light-shielding layer 120 is
selected in order to illustrate the present invention, but is not
limited thereto. With a photomask for forming a minute pattern, the
light-shielding layer 120 may be formed with a thickness of several
hundred A, e.g., about 400 .ANG., about 500 .ANG., about 600 .ANG.,
etc.
[0053] Although not shown, an antireflection layer may be formed on
the light-shielding layer 120. The antireflection layer may be a
layer having reflectivity lower than that of the light-shielding
layer 120. The antireflection layer may be formed of a material
different from that of the light-shielding layer 120 and may be
preferably formed of a material that may be patterned together with
the light-shielding layer 120, in order to easily perform
patterning. For example, when the light-shielding layer 120 is
formed of chromium, the antireflection layer may be formed of
chromium oxide. When the light-shielding layer 120 is formed of a
metal alloy containing chromium or a metal compound other than pure
chromium, the antireflection layer may be formed of a chromium
oxide with a thickness of about several hundred .ANG.. In this
embodiment, although not described, the antireflection layer may be
formed with a thickness of, e.g., about 500 .ANG..
[0054] The first resist film 130 may be formed of a material that
may be selectively patterned by a developer after being exposed to
an electron beam or light. In particular, the resist film 130 may
be formed of, e.g., a carbon-based polymeric compound. The resist
film 130 may be formed of a material that reacts relatively well
with an electron beam, a material that reacts relatively well with
light, or a material that reacts well with both the exposure
sources.
[0055] In the present invention, only an electron beam, only light,
or both the electron beam and light may be used as exposure
sources. Therefore, limiting terms "electron beam resist" and
"photoresist" are not used in this disclosure, but a comprehensive
term "resist" is used. However, a specific resist may be used at
the time when a photomask is formed in order to improve the
properties of the photomask. The thickness of the first resist film
130 may be set to about 4000 .ANG. in this embodiment of the
present invention, but is not limited thereto.
[0056] The first exposed region may be a region substantially
adjacent to a boundary line of a pattern in a region A in which the
density of a pattern to be formed is low. More specifically, the
first exposed region may be a region having a predetermined width
from a boundary line of a dark pattern to be formed toward a clear
pattern.
[0057] First energy refers to energy with a level different from
the level of second energy. In this embodiment of the present
invention, the first energy level may be set to be higher than the
second energy level. However, the first energy level may be lower
than the second energy level. When an electron beam is used, energy
may be used together with a dose and, in particular, may be
understood as being an acceleration voltage or an electron density.
When light is used, energy may be used together with intensity, and
in particular, may be understood as a wavelength or exposure time.
In this embodiment of the present invention, electron beams having
high energy, i.e., high acceleration voltages, may be applied. More
specifically, an electron beam having an acceleration voltage of
about 50 keV may be used as the first energy, and an electron beam
having an acceleration voltage of about 10 keV may be used as the
second energy. However, the acceleration voltages of the electron
beams have been selected in order to exemplify the present
invention, but are not limited thereto.
[0058] The first exposure source may correspond to a second
exposure source, which will be described below. The first exposure
source may be the same as the second exposure source. In this
embodiment of the present invention, an electron beam may be used
as the first exposure source. Light may also be used as the first
exposure source.
[0059] Referring to FIG. 4B, the first exposed region of the region
A having a low pattern density of the first resist film 130 may be
exposed to the first exposure source, and then the first resist
film 130 may be developed by, e.g., a developer, thereby forming a
first resist pattern 130a. The first resist pattern 130a may be
formed by spraying or pouring a developer on the surface of the
first resist film 130 or by soaking the first resist film 130 in
the developer. When the first resist pattern 130a is formed, the
light-shielding layer 120 under the first resist film 130 may be
selectively exposed. The developing method is known and thus a
detail description thereof will be omitted.
[0060] Referring to 4C, the exposed portions of the light-shielding
layer 120 may be etched by using the first resist pattern 130a as
an etching mask. As a result, a first light shielding pattern 120a
may be formed such that the substrate 110 under the light-shielding
layer 120 may be exposed. More specifically, the exposed portions
of the light-shielding layer 120 may be etched by a wet etching
method of, e.g., soaking the light-shielding layer in an acid
etching agent or spraying an acid etching agent on the surface of
the exposed portions of the light-shielding layer, or, e.g., a dry
etching method using an etching gas combination that may include
halogen, e.g., F--, Cl--, Br--, and I--. This etching step may form
the first light shielding pattern 120a such that the substrate 110
under the light-shielding layer 120 may be selectively exposed.
Examples of the acid etching agent may include, e.g.,
H.sub.2SO.sub.4, HF, H.sub.2PO.sub.4, HCl, etc. The etching gas
combination may include gases including a halogenated gas, e.g.,
CF.sub.4, CHF.sub.3, C.sub.2F.sub.4, C.sub.3F.sub.6,
C.sub.4F.sub.8, SF.sub.6, CCl.sub.4, HBr, etc. An inert gas may be
used, e.g., Ne, Ar, and Xe, etc., and at least one of O.sub.2 and
N.sub.2. The etching methods are well known in the art, and a
detail description thereof will be omitted.
[0061] Referring to FIG. 4D, the first resist pattern 130a may be
removed, and thus the first light shielding pattern 120a and the
substrate 110 may be selectively exposed. More specifically, the
first resist pattern 130a may be removed by a wet method using,
e.g., a stripper containing H.sub.2SO.sub.4, or a dry method using,
e.g., a gas combination containing O.sub.2.
[0062] Referring to FIG. 4E, a second resist film 140 may be formed
on the first light shielding pattern 120a, and the substrate 110
may be selectively exposed. Then, second exposed regions of the
region A, having the low pattern density of the second resist film
140, and clear pattern regions of a region B, having a high pattern
density of the second resist film 140, may be exposed to the second
exposure source having the second energy. The second resist film
140 may be formed of the same material as the first resist film
130, or the second resist film 140 may be formed of a material
different from that of the first resist film 130, according to the
exposure source. The second resist film 140 may be formed of an
organic polymeric material. The polymeric material may be, e.g.,
phenyl-formaldehyde resin, acrylic resin, methacrylic resin,
etc.
[0063] The second exposed region may be separate from a boundary
line of a pattern existing in the region A having the low pattern
density. The second exposed region may partially overlap the first
exposed region, but may not overlap the first exposed region, or
may include the first exposed region.
[0064] The second energy may have an energy level different from
the energy level of the first energy. In this embodiment of the
present invention, the second energy may have an energy level lower
than the level of the first energy.
[0065] The second exposure source may be the same as the first
exposure source, or it may be different form the first exposure
source. Both the first and second exposure sources may be electron
beams or light beams. Alternatively, the first exposure source may
be an electron beam and the second exposure source may be light, or
the first exposure source may be light and the second exposure
source may be an electron beam. When high energy light is used,
ultraviolet light may be utilized.
[0066] Referring to FIG. 4F, the second resist film 140 may be
developed to thereby form a second resist pattern 140a. As a
result, the first light shielding pattern 120a may be selectively
exposed. The embodiment illustrated in FIG. 4F may be compared with
the embodiment illustrated in FIG. 4B.
[0067] Referring to FIG. 4G, the first selectively exposed light
shielding pattern 120a may be etched by using the second resist
pattern 140a as a mask for etching, thereby forming a second light
shielding pattern 120b. The second light shielding pattern 120 may
be a final pattern to be formed. A detailed description of FIG. 4G
may be compared with the embodiment illustrated in FIG. 4C and in
the description of FIG. 4C.
[0068] Referring to FIG. 4H, the second resist pattern 140a may be
removed, thereby completing a photomask having the final pattern.
The description of FIG. 4H may be compared with the embodiment
illustrated in FIG. 4D and in the description of FIG. 4D.
[0069] Then, the photomask shown in FIG. 4H may go through a
washing process, a correcting process, a pellicle attaching
process, etc., to thereby complete a final photomask.
[0070] The method of fabricating a photomask according to the
embodiment of the present invention described with reference to
FIGS. 4A to 4H may include forming the first resist film 130,
exposing the first exposed region of the first region A that may
have the low pattern density of the first resist film 130 to the
first exposure source that may have the first energy to form the
first resist pattern 130a, patterning the light-shielding layer 120
to form the first light shielding pattern 120a, removing the first
resist pattern 130a, and forming the second resist film 140. The
method may further include exposing the second exposed region of
the region A, that may have the low pattern density of the second
resist film 140, and the clear pattern region of the region B, that
may have the high pattern density of the second resist film 140, to
the second exposure source that may have the second energy to form
the second resist pattern 140a, patterning the first light
shielding pattern 120a to form the second light shielding pattern
120b, and removing the second resist pattern 140a, thereby
completing a final photomask. In the method, a process of forming,
developing, and removing a resist film, an exposure process, and an
etching process may be performed two or more times.
[0071] Next, a method of fabricating a photomask according to
another embodiment of the present invention will be described with
reference to FIGS. 5A to 5E.
[0072] FIGS. 5A to 5E illustrate longitudinal sectional schematic
views of stages of a method of fabricating a photomask according to
another embodiment of the present invention. The method may also be
described in comparison to FIGS. 4A to 4H.
[0073] As shown in FIG. 5A, a light-shielding layer 220 and a third
resist film 230 may be sequentially formed on a photomask substrate
210, and then first exposed regions of a region A, having a low
pattern density of the third resist film 230, may be exposed to a
first exposure source having a first energy. This process may
correspond to the process shown in FIG. 4A.
[0074] Referring to FIG. 5B, second exposed regions of the region
A, having the low pattern density of the third resist film 230, and
clear pattern regions of a region B having a high pattern density
of the third resist film 230 may be exposed to a second exposure
source having a second energy. This process may correspond to the
process shown in FIG. 4E. More specifically, the same resist film
may be exposed in FIGS. 5A and 5B.
[0075] Referring to FIG. 5C, the third resist film 230 may be
developed to form a third resist pattern 230a. As a result, the
light-shielding layer 220 under the resist film 230 may be
selectively exposed. The process may correspond to the processes
shown in FIGS. 4B and 4F.
[0076] Referring to FIG. 5D, the exposed portions of the
light-shielding layer 220 may be etched by using the third resist
pattern 230a as a mask for etching, thereby forming a third light
shielding pattern 220a. This process may correspond to the
processes shown in FIGS. 4C and 4G.
[0077] Referring to FIG. 5E, the third resist pattern 230a may be
removed, thereby completing a photomask. This process may
correspond to the processes shown in FIGS. 4D and 4H.
[0078] The method of fabricating a photomask according to another
embodiment of the present invention described with reference to
FIGS. 5A to 5E may include forming the light-shielding layer 220
and the resist film 230 on the photomask substrate 210, exposing
the first exposed regions of the region A having the low pattern
density of the resist film 230 to the first exposure source having
the first energy, exposing the second exposed regions of the region
A, which may have the low pattern density, and the clear pattern
regions of the region B, which may have the high pattern density,
to the second exposure source having the second energy to form the
resist pattern 230a, patterning the light-shielding layer 220 to
form the third light shielding pattern 220a, and removing the
resist pattern 230a to complete the final photomask. The photomask
fabricating method may use one resist film 230.
[0079] In the method of fabricating a photomask according to any
one of the embodiments of the present invention, a photomask may be
fabricated by forming a light-shielding layer and a first resist
film on a substrate, performing a primary exposure of first exposed
regions that may be adjacent to a pattern existing in a first
pattern density region to an electron beam with a first energy, and
performing a secondary exposure of exposing second exposed regions
of the first pattern density region, except for the first exposed
regions, and a second pattern density region to an electron beam
with a second energy.
[0080] The first pattern density region may be a region having a
pattern density lower than that of the second pattern density
region. The electron beam with the first energy may have an
electron acceleration voltage higher than that of the electron beam
with the second energy.
[0081] FIGS. 6A and 6B illustrate views of an apparatus for
fabricating a photomask according to an embodiment of the present
invention.
[0082] Referring to FIG. 6A, an apparatus 500 for fabricating a
photomask according to an embodiment of the invention may include a
vacuum chamber 510, a transfer chamber 520 that may include a
transfer arm R capable of loading or unloading photomasks M, an
arranging chamber 530 that may arrange the photomasks M, a first
exposure chamber 540 that may expose the surfaces of blank
photomasks to a first exposure source having a first energy, and a
second exposure chamber 550 that may expose the surfaces of the
blank photomasks to a second exposure source having a second
energy.
[0083] The vacuum chamber 510 may be a device for placing the
entire apparatus for fabricating a photomask under a vacuum, or the
vacuum chamber 510 may be a space for making the air pressure in
the chamber equal to the air pressure of the outside of the chamber
when the photomask M may be carried into the chamber from the
outside or is carried out of the chamber. Although not shown, a
vacuum pump or a gas or air injection tube may be included in the
vacuum chamber 510.
[0084] The transfer chamber 520 may include the transfer arm R. The
transfer arm R may transfer the photomask M or a stage S among the
vacuum chamber 510, the arranging chamber 530, the first exposure
chamber 540, and the second exposure chamber 550. Entry to and
egress from the various chambers may be via doors D1, D2, D3 and
D4.
[0085] The arranging chamber 530 may arrange the photomasks M and,
particularly, may arrange the photomasks M on the stage S. The
stage S may be a device where photomasks are safely loaded in an
exposing process.
[0086] The first exposure chamber 540 may be a chamber for primary
exposure of the surface of a photomask to a first exposure source
having a first energy, and the second exposure chamber 550 may be a
chamber for secondary exposure of the surface of a photomask to a
second exposure source having a second energy. The first and second
exposure chambers will be described below in detail.
[0087] Both the first and second exposure sources may be electron
beams, or the first exposure source may be an electron beam and the
second exposure source may be light. Alternatively, the first
exposure source may be light and the second exposure source may be
an electron beam.
[0088] The first energy may be higher than the second energy, or
the second energy may be higher than the first energy. When an
exposure source is an electron beam, energy may be adjusted with an
acceleration voltage or an electron density. When an exposure
source is light, energy may be expressed by intensity, or it may be
adjusted with the wavelength of light or exposure time. Adjusting
the energy of an exposure source is well known, and thus a
description thereof will be omitted.
[0089] A blank photomask refers to a photomask having no pattern
formed therein. The blank photomask may include a glass substrate
made of quartz, a light-shielding layer formed on the glass
substrate, an antireflection layer formed on the light-shielding
layer, and a resist film formed on the antireflection layer.
[0090] The light-shielding layer of the photomask may be formed of
a metallic material, e.g., chromium, aluminum, molybdenum, or
titanium, a metal alloy, a metal compound, a combination thereof,
etc. The antireflection layer may be formed of a metal compound
such as a chromium oxide.
[0091] The resist film may be formed of an electron beam resist or
a photoresist.
[0092] FIG. 6B illustrates a perspective schematic view of the
inside of the first and second exposure chambers 540 and 550.
[0093] Referring to FIG. 6B, the exposure chambers 540 and 550 may
include separate exposure spaces, exposure stages S1 and S2, and
exposure source irradiating devices 560 and 570, respectively. The
stages S1 and S2, on which the photomasks M may be safely loaded,
may move backward, forward, right, and left. The exposure source
irradiating devices 560 and 570 may irradiate exposure sources onto
the surfaces of the photomasks M safely loaded on the stages S1 and
S2 while moving the stages S1 and S2 backward, forward, right, and
left.
[0094] The exposure source irradiating devices 560 and 570 may
irradiate an electron beam or light. When the exposure source is an
electron beam, each of the exposure source irradiating devices 560
and 570 may irradiate an electron beam having a predetermined
energy under the control of an electron beam calibration system.
When the exposure source is light, it may be possible to irradiate
light onto the photomasks M safely loaded on the stages S1 and S2
by transmitting the light from a light-emitting source through an
optical fiber or a lens system. Although not shown, when the
exposure source is light, a shutter or a separating system for
separating light into multiple shots may be included in each
exposure source irradiating device. More specifically, an openable
separating system, such as a camera shutter, or a polygonal rotary
mirror system may be provided. The rotary mirror system may
separate light into multiple shots whose number may be the same as
that of the planes thereof during one turn.
[0095] FIGS. 7A and 7B are flow charts illustrating stages of a
method of fabricating a photomask by using an apparatus for
fabricating a photomask according to an embodiment of the present
invention. The method of fabricating a photomask using the
apparatus for fabricating a photomask according to an embodiment of
the present invention will be described with reference to FIG.
7A.
[0096] First, a light-shielding layer including an antireflection
layer may be formed on a substrate, and a first resist film may be
formed on the light-shielding layer, thereby completing a blank
photomask. The blank photomask may be carried into the vacuum
chamber 510 of the apparatus for fabricating a photomask, and the
vacuum chamber 510 may be placed under a vacuum. Then, a door D2
between the vacuum chamber 510 and the transfer chamber 520 may be
opened. Subsequently, the transfer arm R may transfer the photomask
M from the vacuum chamber 510 to the arranging chamber 530, may
arrange the photomask M on the stage S in the arranging chamber
530, and may transfer the arranged photomask M to the first
exposure chamber 540. In the first exposure chamber 540, the first
exposed regions of the photomask M may be primarily exposed to the
first exposure source having the first energy. After the primary
exposure of the photomask M in the first exposure chamber 540, the
transfer arm R may transfer the photomask M to the outside of the
first exposure chamber 540. The photomask M transferred to the
outside of the first exposure chamber 540 may be transferred to the
vacuum chamber 510 and may be then removed from the apparatus 500
for fabricating a photomask. Subsequently, the photomask M may be
baked and developed, thereby forming a first resist pattern. Then,
the photomask M may be etched to form a first light shielding
pattern.
[0097] Next, the first resist pattern may be removed, and a second
resist film may be formed on the first light shielding pattern. The
photomask M having the second resist film formed thereon may be
carried into the vacuum chamber 510, and the vacuum chamber 510 may
be evacuated, i.e., placed under a vacuum. The transfer arm R may
transfer the photomask M in the vacuum chamber 510 to the arranging
chamber 530, may arrange the photomask M on the stage in the
arranging chamber 530, and may transfer the arranged photomask M
into the second exposure chamber 550. In the second exposure
chamber 550, the second exposed regions of the photomask M may
undergo a secondary exposure to the second exposure source having
the second energy. After the secondary exposure of the photomask M,
the transfer arm R may transfer the photomask M from the second
exposure chamber 550 to the vacuum chamber 510. Then, the photomask
M may be taken out from the apparatus 500 for fabricating a
photomask. Subsequently, the photomask M may be baked and
developed, thereby forming a second resist pattern. Then, the
photomask M may be etched to form a second light shielding pattern.
Next, the second resist pattern may be removed. In this way, the
photomask M may be completed. The above-mentioned processes may
correspond to the processes shown in FIGS. 4A to 4H.
[0098] A method of fabricating a photomask using an apparatus for
fabricating a photomask according to another embodiment of the
present invention will be described with reference to FIG. 7B.
First, a light-shielding layer including an antireflection layer
may be formed on a substrate, and a resist film may be formed on
the light-shielding layer, thereby completing a blank photomask.
The blank photomask may be carried into the vacuum chamber 510 of
the apparatus for fabricating a photomask, and the vacuum chamber
510 may be evacuated, i.e., placed under a vacuum. Then, the
chamber door D2 between the vacuum chamber 510 and the transfer
chamber 520 may be opened. Subsequently, the transfer arm R may
transfer the photomask M from the vacuum chamber 510 to the
arranging chamber 530, may arrange the photomask M on the stage S
in the arranging chamber 530, and may transfer the arranged
photomask M to the first exposure chamber 540.
[0099] In the first exposure chamber 540, the first exposed regions
of the photomask M may undergo a primary exposure to the first
exposure source having the first energy. After the primary exposure
of the photomask M in the first exposure chamber 540, the transfer
arm R may transfer the photomask M to the second exposure chamber
550. In the second exposure chamber 550, the second exposed regions
of the photomask M may undergo a secondary exposure to the second
exposure source having the second energy. After the secondary
exposure of the photomask M, the transfer arm R may transfer the
photomask M from the second exposure chamber 550 to the vacuum
chamber 510. Then, the photomask M may be taken out from the
apparatus 500 for fabricating a photomask. Subsequently, the
photomask M may be baked and developed, thereby forming a resist
pattern. Then, the photomask M may be etched to form a light
shielding pattern. Next, the resist pattern may be removed. In this
way, the photomask M may be completed. The above-mentioned
processes may be described with reference to FIGS. 5A to 5E.
[0100] The apparatus for fabricating a photomask according to an
embodiment of the present invention may include a vacuum chamber, a
transfer chamber including a transfer arm capable of loading or
unloading photomasks, an arranging chamber for arranging the
photomasks M, a first exposure chamber for exposing first regions
of the surfaces of blank photomasks to an electron beam having a
first acceleration voltage, and a second exposure chamber for
exposing the second regions, which may be adjacent to and wider
than the first regions, and the third regions, which may be
separated from and wider than the first regions, of the surfaces of
the photomasks to an electron beam having a second acceleration
voltage that may be lower than the first acceleration voltage.
[0101] In addition, the present invention may be applied to a
reflective photomask. The term "reflective photomask" refers to a
photomask for forming a pattern on a wafer by reflecting light, for
example, a photomask using EUV (Extreme Ultra Violet) light as an
exposure source. The reflective photomask may be completed by
laminating a reflective layer on a glass substrate made of quartz
and forming a light shielding pattern on the reflective layer.
Since the present invention may form a light shielding pattern, it
may be applied to a reflective photomask. Although a method of
fabricating a reflective photomask is not shown, those skilled in
the art may easily apply the concepts of the present invention to a
method of fabricating a reflective photomask. Therefore, the
specification and claims of the present invention may include a
reflective photomask as well as a transmissive photomask.
[0102] As described above, according to a photomask and a method
and apparatus for fabricating a photomask of the above-described
embodiments of the present invention, it may be possible to rapidly
fabricate a photomask having a fine photomask pattern with the
uniform line widths of separated patterns and close patterns.
[0103] Exemplary embodiments of the present invention have been
disclosed herein, and although specific terms are employed, they
are used and are to be interpreted in a generic and descriptive
sense only and not for purpose of limitation. Accordingly, it will
be understood by those of ordinary skill in the art that various
changes in form and details may be made without departing from the
spirit and scope of the present invention as set forth in the
following claims.
* * * * *