U.S. patent application number 10/124578 was filed with the patent office on 2002-10-24 for plasma etching chamber and method for manufacturing photomask using the same.
Invention is credited to Cho, Sung-Yong, Jeong, Hae-Young, Kim, Jin-Min, Lee, Jeong-Yun, No, Young-Hwa, Yoon, Sang-Joon.
Application Number | 20020153104 10/124578 |
Document ID | / |
Family ID | 19708633 |
Filed Date | 2002-10-24 |
United States Patent
Application |
20020153104 |
Kind Code |
A1 |
Lee, Jeong-Yun ; et
al. |
October 24, 2002 |
Plasma etching chamber and method for manufacturing photomask using
the same
Abstract
A plasma etching chamber of a plasma etching apparatus used in
an etching process for manufacturing a photomask and a method for
manufacturing a photomask using the same. The plasma etching
chamber includes an electrode having a supporting surface for
supporting a photomask substrate and a top surface surrounding the
supporting surface, a heat transfer element installed along a
peripheral edge of the supporting surface, and a heater for
supplying heat to the heat transfer element. In the method for
manufacturing a photomask, a shading layer is formed on a
transparent substrate. A photoresist layer pattern is formed on the
shading layer to partially expose the shading layer. The shading
layer is etched to form a shading layer pattern, using plasma with
the photoresist layer pattern as an etching mask, under a state in
which the temperature of at least one portion of the peripheral
edge of the transparent substrate is maintained higher than a
temperature at a center of the transparent substrate.
Inventors: |
Lee, Jeong-Yun; (Suwon-City,
KR) ; Kim, Jin-Min; (Suwon-City, KR) ; Jeong,
Hae-Young; (Suwon-City, KR) ; No, Young-Hwa;
(Seoul, KR) ; Yoon, Sang-Joon; (Osan-City, KR)
; Cho, Sung-Yong; (Suwon-City, KR) |
Correspondence
Address: |
VOLENTINE FRANCOS, P.L.L.C.
Suite 150
12200 Sunrise Valley Drive
Reston
VA
20191
US
|
Family ID: |
19708633 |
Appl. No.: |
10/124578 |
Filed: |
April 18, 2002 |
Current U.S.
Class: |
156/345.51 ;
156/345.52; 438/689 |
Current CPC
Class: |
G03F 1/80 20130101; H01J
2237/2001 20130101; H01J 37/32724 20130101; H01J 37/32009
20130101 |
Class at
Publication: |
156/345.51 ;
156/345.52; 438/689 |
International
Class: |
C23F 001/00; H01L
021/302; H01L 021/461 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 24, 2001 |
KR |
2001-22068 |
Claims
What is claimed is:
1. A plasma etching chamber comprising: an electrode including a
supporting surface for supporting a photomask substrate, and a top
surface surrounding the supporting surface; a heat transfer element
installed along a peripheral edge of the supporting surface; and a
heater for supplying heat to the heat transfer element.
2. The plasma etching chamber of claim 1, wherein the heat transfer
element is integrally formed within the electrode.
3. The plasma etching chamber of claim 2, wherein the heat transfer
element is partially exposed along the peripheral edge of the
supporting surface and the top surface of the electrode.
4. The plasma etching chamber of claim 2, wherein a horizontal
plane of the supporting surface is stepped down from a horizontal
plane of the top surface, and the electrode further comprises a
side wall extending between the top surface and the supporting
surface, and wherein the heat transfer element is partially exposed
along the peripheral edge of the supporting surface, the side wall,
and the top surface of the electrode.
5. The plasma etching chamber of claim 2, wherein the heat transfer
element is partially exposed only along the peripheral edge of the
supporting surface.
6. The plasma etching chamber of claim 1, wherein the heat transfer
element is formed of metal.
7. The plasma etching chamber of claim 1, wherein the heat transfer
element comprises a pipe line, and a heat transfer fluid flowing
through the pipe line for heating the pipe line.
8. The plasma etching chamber of claim 7, wherein the heat transfer
fluid is one selected from oil and gas.
9. The plasma etching chamber of claim 1, wherein the heat transfer
element is a heating coil.
10. The plasma etching chamber of claim 1, wherein the electrode
and supporting surface face upwardly toward an upper portion of the
plasma etching chamber.
11. A plasma etching chamber comprising: an electrode including a
supporting surface for supporting a photomask substrate, and a top
surface surrounding the supporting surface; a chucking pad arranged
below the electrode, the chucking pad having a contact surface in
contact with corner portions of the photomask substrate for fixing
the photomask substrate supported by the supporting surface; a heat
transfer element installed within the chucking pad to heat the
corner portions of the photomask substrate; and a heater for
supplying heat to the heat transfer element.
12. The plasma etching chamber of claim 11, wherein the heat
transfer element is installed within the contact surface of the
chucking pad.
13. The plasma etching chamber of claim 12, wherein the heat
transfer element is comprised of metal.
14. The plasma etching chamber of claim 12, wherein the heat
transfer element is comprised of a heating coil.
15. The plasma etching chamber of claim 12, wherein the electrode
and the supporting surface face downwardly toward a lower portion
of the plasma etching chamber.
16. A method for manufacturing a photomask comprising: forming a
shading layer on a transparent substrate; forming a photoresist
layer pattern on the shading layer so as to partially expose the
shading layer; etching the shading layer using plasma to form a
shading layer pattern, and using the photoresist layer pattern as
an etching mask; and heating the transparent substrate, while
etching, such that a temperature of at least one portion of a
peripheral edge of the transparent substrate is maintained higher
than a temperature of a center portion of the transparent
substrate.
17. The method of claim 16, further comprising providing a
transparent substrate formed of quartz.
18. The method of claim 16, further comprising providing a shading
layer formed of chrome.
19. The method of claim 16, further comprising providing a
photoresist layer pattern formed of an electron-beam
photoresist.
20. The method of claim 16, wherein during the etching of the
shading layer, the heating comprises heating a peripheral edge of
the transparent substrate in order to maintain the temperature of
the peripheral edge of the transparent substrate higher than the
temperature of the center of the transparent substrate.
21. The method of claim 16, wherein during the etching of the
shading layer, the heating comprises heating only a bottom edge of
the transparent substrate in order to heat the peripheral edge of
the transparent substrate.
22. The method of claim 16, wherein during the etching of the
shading layer, the heating comprises heating a bottom edge and side
walls of the transparent substrate in order to the heat the
peripheral edge of the transparent substrate.
23. The method of claim 16, wherein during the etching the shading
layer, corner portions of the peripheral edge of the transparent
substrate are heated in order to maintain the corners of the
transparent substrate at a temperature higher than the temperature
of the center of the transparent substrate.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a plasma etching chamber
and a method for manufacturing a photomask using the same, and more
particularly, to a plasma etching chamber of a plasma etching
device used in an etching process for manufacturing a photomask and
a method for manufacturing a photomask using the same.
[0003] 2. Description of the Related Art
[0004] A photomask is typically used in a photolithographic process
for manufacturing a semiconductor device, and the photomask may
have various exposure patterns to achieve the desired result. To
form a photomask having a desired exposure pattern, a shading layer
is first formed on a photomask substrate, and a photoresist pattern
is formed on the shading layer to expose a portion of the shading
layer to create a shading layer pattern.
[0005] In general, photomask substrates are square-shaped. When the
photoresist layer is formed on a square-shaped photomask substrate,
a portion of the photoresist layer at the corners of the photomask
substrate is thicker than a portion of the photoresist layer near
the center of the photomask substrate. For example, in the case of
forming an electron beam photoresist layer to a thickness of 3000
.ANG., the electron beam photoresist layer at the corners of the
photomask substrate is about 200 .ANG. thicker than the electron
beam photoresist layer at the center of the photomask
substrate.
[0006] Given this non-uniformity, after electron beam exposure and
development are performed on the resultant substrate, the critical
dimension (CD) of a portion close to the edge of the photomask
substrate becomes smaller than that of a portion close to the
center of the photomask substrate. Indeed, based on an after
development inspection (ADI) performed after the photoresist layer
pattern is formed to partially expose the shading layer on the
photomask substrate, it has been noted that portions closer to the
edge of the photomask substrate exhibit a smaller CD value.
[0007] Moreover, after the shading layer is etched by dry etching
using the photoresist layer pattern as an etching mask, the
difference in the CD among portions of the photomask substrate is
even more pronounced. More specifically, the shading layer is
etched to form a shading layer pattern, and then stripping and
cleaning processes are performed on the resultant substrate. After
that, an after cleaning inspection (ACI) is carried out. With
reference to the ACI, the difference in the CD among portions of
the shading layer pattern is more pronounced, because an etching
rate for the shading layer at the center of the photomask substrate
is relatively high, whereas an etching rate for the shading layer
at the edge of the photomask substrate is relatively low.
[0008] As described above, if a photomask having a predetermined
exposure pattern and exhibiting non-uniform CD distribution over an
entire photomask substrate is used in the manufacture of
semiconductor devices, various problems may occur, including
performance degradation or inoperative devices.
SUMMARY OF THE INVENTION
[0009] To solve the above problems, it is a first object of the
present invention to provide a plasma etching chamber used to
perform an etching process for forming a shading layer pattern with
a uniform CD distribution over an entire photomask substrate.
[0010] It is a second object of the present invention to provide a
method for manufacturing a photomask including a shading layer
pattern which has a uniform CD distribution over an entire
photomask substrate.
[0011] Accordingly, to achieve the first object, the present
invention provides a plasma etching chamber including an electrode
having a supporting surface for supporting a photomask substrate,
and a top surface surrounding the supporting surface. A heat
transfer element is installed along the peripheral edge of the
supporting surface, and a heater is provided to supply heat to the
heat transfer element.
[0012] Preferably, the heat transfer element is built into the
electrode itself. The heat transfer element may be partially
exposed along the peripheral edge of the supporting surface and the
top surface on the electrode.
[0013] When the supporting surface is stepped down from the top
surface, the electrode may further include a side wall extending
between the top surface and the supporting surface, and the heat
transfer element may be partially exposed along the peripheral edge
of the supporting surface, the side wall, and the top surface.
[0014] Alternatively, the heat transfer element may be built into
the electrode so that it is not exposed on the top surface of the
electrode.
[0015] In another aspect, the present invention provides a plasma
etching chamber including an electrode, including a supporting
surface for supporting a photomask substrate and a top surface
surrounding the supporting surface. A chucking pad has a contact
surface in contact with the corners of the photomask substrate and
fixes the photomask substrate which is supported by the supporting
surface. A heat transfer element is installed at the chucking pad
to heat the corners of the photomask substrate, and a heater
supplies heat to the heat transfer element. Preferably, the heat
transfer element is built into the chucking pad.
[0016] To achieve the second object, the present invention provides
a method for manufacturing a photomask, in which a shading layer is
first formed on a transparent substrate. A photoresist layer
pattern is formed on the shading layer so as to partially expose
the shading layer. The shading layer is etched using plasma and
using the photoresist layer pattern as an etching mask under a
state in which at least one portion of the peripheral edge of the
transparent substrate is maintained at a temperature higher than
the temperature of the center of the transparent substrate.
[0017] During the step of etching the shading layer, the peripheral
edge of the transparent substrate may be uniformly heated in order
to maintain the temperature of the edge of the transparent
substrate higher than the temperature of the center of the
transparent substrate. Alternatively, the heat may be applied to
the bottom edge of the transparent substrate in order to heat the
edge of the transparent substrate. In another alternative, heat may
be applied to the bottom edge and side walls of the transparent
substrate in order to the heat the edge of the transparent
substrate. A heat transfer element installed along the edge of the
transparent substrate, and a heater for supplying heat to the heat
transfer element, may be used for uniformly heating the edge of the
transparent substrate.
[0018] Also, during the step of etching the shading layer, the
corners of the transparent substrate may be heated in order to
maintain the temperature of the corners of the transparent
substrate higher than the temperature of the center of the
transparent substrate. A heat transfer element installed along the
corners of the transparent substrate, and a heater for supplying
heat to the heat transfer element, may be used for heating the
corners of the transparent substrate.
[0019] The plasma etching chamber according to the present
invention includes the heat transfer element for maintaining the
temperature of the corners of the transparent substrate higher than
the temperature of the center of the transparent substrate. Thus,
it is possible to form a shading layer having a uniform CD
distribution over the entire photomask substrate. In addition, in
the method for manufacturing a photomask according to the present
invention, when etching the shading layer, the temperature of at
least one portion of the edge of the transparent substrate is
maintained higher than the temperature of the center of the
transparent substrate by heating the at least one portion of the
edge of the transparent substrate. Therefore, it is possible to
form a shading layer pattern having a uniform CD distribution over
the transparent substrate by increasing an etching rate for the
shading layer at the edge of the transparent substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The above objects and advantages of the present invention
will become more apparent by describing in detail a preferred
embodiment thereof with reference to the attached drawings in
which:
[0021] FIG. 1 is a schematic view of a plasma etching chamber
according to a first embodiment of the present invention;
[0022] FIG. 2 is a top view of an electrode and a heat transfer
element included in the plasma etching chamber according to the
first embodiment of the present invention;
[0023] FIGS. 3 through 5 are views illustrating the detailed
structure of different embodiments of a heat transfer element
included in the plasma etching chamber according to the first
embodiment of the present invention;
[0024] FIG. 6 is a top view illustrating the structure of a plasma
etching chamber according to a second embodiment of the present
invention;
[0025] FIG. 7 is a cross-sectional view of an electrode of the
plasma etching chamber according to the second embodiment of the
present invention, taken along line 7-7' of FIG. 6;
[0026] FIG. 8 is a cross-sectional view of the electrode of the
plasma etching chamber according to a second embodiment of the
present invention, taken along line 8-8' of FIG. 6;
[0027] FIGS. 9A and 9B are cross-sectional views illustrating a
method for manufacturing a photomask according to a preferred
embodiment of the present invention; and
[0028] FIGS. 10 and 11 are views illustrating the bottom surface of
a transparent substrate shown in FIGS. 9A and 9B.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] The present invention may be embodied in many different
forms and should not be construed as being limited to the present
embodiment set forth herein. Rather, the embodiment is provided so
that this disclosure will be thorough and complete, and will fully
convey the concept of the invention to those skilled in the art. In
the drawings, the thickness of layers and regions are exaggerated
for clarity. It will also be understood that when a layer is
referred to as being "on" another layer or substrate, it can be
directly on the other layer or substrate, or intervening layers may
also be present.
[0030] In general, as the temperature of a typical photoresist
layer or a chrome layer increases, the etching rate increases. The
present invention will overcome a problem with non-uniform
distribution of critical dimension (CD) values throughout a
photomask substrate using the above property.
[0031] FIG. 1 is a schematic view illustrating the structure of a
plasma etching chamber according to a first embodiment of the
present invention. The plasma etching chamber may be installed in a
transformer coupled plasma (TCP) etching apparatus, for example, or
other suitable plasma etching chamber.
[0032] Referring to FIG. 1, a plasma etching chamber 10 includes a
chamber wall 12, a TCP coil 14 installed on the chamber wall 12,
and a first power source 16 for applying radio-frequency (RF) power
to the TCP coil 14.
[0033] An electrode 30 for supporting a photomask substrate 20 is
installed inside the plasma etching chamber 10. The electrode 30
includes a supporting surface 32 for supporting the photomask
substrate 20 and a top surface 34 positioned outwardly of the
supporting surface 32 and surrounding the supporting surface 32.
Note, that in this embodiment of the electrode 30, the supporting
surface 32 is recessed (or has a step difference) from the top
surface 34, although in other embodiments it need not be. In other
words, a horizontal plane comprising the supporting surface 32 is
recessed from a horizontal plane comprising the top surface 34. In
this recessed embodiment, a side wall 36 extends between the top
surface 34 and the supporting surface 32 in the electrode 30,
thereby forming a shoulder S on which the photomask substrate 20
rests.
[0034] A second power source 18 for applying radio-frequency (RF)
power to the electrode 30 is connected to the bottom of the plasma
etching chamber 10. The electrode 30 is installed so that the
supporting surface 32 and top surface 34 face upward.
[0035] If an RF power is applied from the first power source 16 to
the TCP coil 14, a magnetic field is formed around the TCP coil 14.
As a result, magnetic field lines extend vertically downward into
the inside of the plasma etching chamber 10. Then, an etching gas
in the plasma etching chamber 10 is ionized by the magnetic field
inside the plasma etching chamber 10, and plasma is generated due
to the ionization of the etching gas. If an RF power is then
applied from the second power source 18 connected to the electrode
30, plasma is attracted towards the photomask substrate 20
supported on the electrode 30. As a result, a layer deposited on
the photomask substrate 20 is etched.
[0036] To obtain a uniform CD distribution of the photomask
substrate 20 while etching the layer deposited on the photomask
substrate 20, a heat transfer element 40 is installed near the edge
of the supporting surface 32 of the electrode 30. The heat transfer
element 40 is connected to a heater 50 for supplying heat to the
heat transfer element 40.
[0037] As illustrated in FIG. 1, the heat transfer element 40 is
preferably built into the electrode 30, in the shoulder area S of
the electrode 30, thereby forming an L-shaped heat transfer
element. In FIG. 1, the heat transfer element 40 is illustrated as
being partially exposed at the peripheral edge of the supporting
surface 32 on the electrode 30, the side wall 36, and the top
surface 34 to effectively heat the edge of the photomask substrate
20. Since the exposed portion of the supporting surface 32 is very
close to the bottom edge of the photomask substrate 20 and the side
wall 36, the edge of the photomask substrate 20 can be effectively
heated. However, if the heat transfer element 40 is installed only
around the edge of the photomask substrate 20 in contact with the
supporting surface 32, the heat transfer element 40 may be formed
within the electrode 30 such that the heat transfer element 40 is
not exposed on the top surface 34 of the electrode 30.
[0038] FIG. 2 is a top view illustrating the electrode 30 and the
heat transfer element 40 built into the electrode 30 of FIG. 1. As
viewed from above the electrode 30, the L-shaped heat transfer
element 40 is installed to completely enclose the peripheral edge
of the supporting surface 32, and extends from the edge of the
supporting surface 32 to a certain width along the top surface
34.
[0039] FIGS. 3 through 5 are views illustrating the detailed
structure of alternate embodiments of the heat transfer element 40.
Referring to FIG. 3, the heat transfer element 40 may be comprised
of a metal line 62 having a high heat conductivity. The metal line
62 includes a connection unit 62a which is connected to the heater
50 to receive heat supplied from the heater 50.
[0040] Referring to FIG. 4, the heat transfer element 40 may
include a pipe line 72 and heat transfer fluid flowing through the
pipe line 72 for heating the pipe line 72. The heat transfer fluid
may be oil or gas, and the fluid functions to transmit heat
supplied from the heater 50 to the pipe line 72.
[0041] Referring to FIG. 5, the heat transfer element 40 may be
comprised of a heating coil 82 in various configurations based on
the desired heating profile, for example, edge heating, edge and
side wall heating, or edge, side wall and top surface heating.
[0042] Since the plasma etching chamber 10 according to the first
embodiment of the present invention includes the heat transfer
element 40 for heating the edge of the photomask substrate 20, the
edge of the photomask substrate 20 can be heated to a temperature
higher than the temperature at the center of the photomask
substrate 20, and thus an etching rate for a shading layer in an
etching process for forming a shading layer pattern can be
uniformly controlled on the entire photomask substrate 20. This is
because as the temperature of a typical photoresist layer
increases, the etching rate increases. As a result, it is possible
to form the shading layer pattern to exhibit a uniform CD
distribution over the entire photomask substrate 20.
[0043] FIG. 6 is a partial schematic top view illustrating the
structure of a plasma etching chamber according to a second
embodiment of the present invention. FIG. 7 is a cross-sectional
view of the electrode 130 of the plasma etching chamber according
to the second embodiment of the present invention, taken along line
7-7' of FIG. 6. FIG. 8 is an enlarged cross-sectional view of the
electrode of the plasma etching chamber according to a second
embodiment of the present invention, taken along line 8-8' of FIG.
6. The plasma etching chamber according to the second embodiment of
the present invention may be included in an inductively coupled
plasma (ICP) etching apparatus.
[0044] Referring to FIGS. 6 through 8, the electrode 130 shown in
FIG. 6 is installed in a face-down type plasma etching chamber in
which a top surface 134 of the electrode 130 faces downward. The
plasma etching chamber includes a supporting surface 132 for
supporting a photomask substrate 120. The electrode 130 including
the top surface 134 surrounds the recessed (or stepped down)
supporting surface 132. In this stepped down electrode
configuration, a side wall 136 extends between the top surface 134
and the supporting surface 132.
[0045] A plurality of chucking pads 140 are installed below the
electrode 130 as shown best in FIG. 8. The chucking pads 140 fix
the photomask substrate 120 that is supported by the supporting
surface. Each of the chucking pads 140 includes a contact surface
142 extending inwardly of the side walls 136 such that the chucking
pads 140 and the corners of the photomask substrate 120 contact
each other so that the photomask substrate 120 is fixed in
place.
[0046] A heat transfer element 160 for heating the corners of the
photomask substrate 120 is built into each of the chucking pads
140. The heat transfer element 160 receives heat supplied from a
heater 150. The heat transfer element 160 may be comprised of
metal, a heating coil, or other heating device embodiments as set
forth in FIGS. 3-5.
[0047] Since the plasma etching chamber according to the second
embodiment of the present invention includes the chucking pads 140
in which the heat transfer element 160 is installed, it is possible
to effectively heat only the corners of the photomask substrate 120
showing a relatively large thickness of photoresist and a
relatively small CD value along portions of the edge of the
photomask substrate 120. Accordingly, the corners of the photomask
substrate 120 can be heated to a temperature higher than the
temperature at the center of the photomask substrate 120.
Therefore, an etching rate for a shading layer in an etching
process for forming a shading layer pattern can be uniformly
controlled along the entire photomask substrate 120. As a result,
it is possible to form the shading layer pattern having a uniform
CD distribution over the entire photomask substrate 120.
[0048] FIGS. 9A and 9B are cross-sectional views illustrating a
method for manufacturing a photomask according to a preferred
embodiment of the present invention.
[0049] Referring to FIG. 9A, a shading layer 210, such as a chrome
layer, is formed on a transparent substrate 200, such as a quartz
substrate. A photoresist layer pattern 220 is formed on the shading
layer 210 to partially expose the shading layer 210. The
photoresist layer pattern 220 may be an electron beam
photoresist.
[0050] Referring to FIG. 9B, the shading layer 210 is etched by
performing an etching process using plasma while using the
photoresist layer pattern 220 as an etching mask under a state in
which the temperature of at least a portion of the edge of the
transparent substrate 200 is maintained higher than the temperature
of the center of the transparent substrate 200, thus forming a
uniform shading layer pattern 210a. Here, a typical plasma etching
apparatus, such as a TCP etching apparatus or an ICP etching
apparatus, may be used.
[0051] FIGS. 10 and 11 are views illustrating the bottom surface of
the transparent substrate 200.
[0052] To maintain the temperature of a peripheral edge portion
202a of the transparent substrate 200 higher than the temperature
of the center 202c of the transparent substrate 200 while etching
the shading layer 210, only the edge portion 202a of the
transparent substrate 200, which is denoted by the slanted lines in
FIG. 10, is heated. The side walls of the transparent substrate 200
and the peripheral edge portion 202a can be heated at the same
time. An etching apparatus including the plasma etching chamber 10,
which has been described with reference to FIG. 1, may be used.
[0053] In addition, to maintain the temperature of corners 202b of
the transparent substrate 200, at which CD values decrease
considerably, among the peripheral edge portion 202a of the
transparent substrate 200, higher than the temperature of the
center 202c of the transparent substrate 200 while etching the
shading layer 210, the corners 202b of the transparent substrate,
which are denoted by the slanted lines in FIG. 11, can be heated.
At this time, a plasma etching chamber including chucking pads,
which has been described above with reference to FIG. 8, may be
used.
[0054] As described above, an etching rate for the shading layer
210 at a peripheral edge portion or corners of the transparent
substrate 200 can be enhanced by maintaining the temperature of at
least a portion of the edge of the transparent substrate 200 higher
than the temperature of the center of the transparent substrate 200
while etching the shading layer 210. As a result, it is possible to
obtain a shading layer pattern having a uniform CD distribution
over the entire transparent substrate 200.
[0055] As described above, the plasma etching chamber according to
the present invention includes a heat transfer element for
maintaining the temperature of the edge of the photomask substrate
higher than the temperature of the center of the photomask
substrate by heating the edge or corners of the photomask
substrate. Again, since the edge or corners of the photomask
substrate can be heated to a higher temperature than the center of
the photomask substrate, the etching rate for a shading layer can
be controlled to ensure layer uniformity over the entire photomask
substrate. As a result, it is possible to form a shading layer
pattern having a uniform CD distribution over the entire photomask
substrate.
[0056] In the method for manufacturing a photomask according to the
present invention, before etching a shading layer, at least one
portion of the edge of a transparent substrate is heated to a
temperature higher than the temperature of the center of the
transparent substrate. Thus, while etching the shading layer, an
etching rate for the shading layer at the edge or corners of the
transparent substrate can be enhanced. As a result, it is possible
to form a shading layer pattern having a uniform CD distribution
over the entire photomask substrate.
[0057] While this invention has been particularly shown and
described with reference to preferred embodiments thereof, it will
be understood by those skilled in the art that various changes in
form and details may be made therein without departing from the
spirit and scope of the invention as defined by the appended
claims.
* * * * *