U.S. patent application number 14/261005 was filed with the patent office on 2014-08-21 for method of cleaning substrate.
This patent application is currently assigned to HOYA CORPORATION. The applicant listed for this patent is HOYA CORPORATION, OSAKA UNIVERSITY. Invention is credited to Tsutomu SHOKI, Takeyuki YAMADA, Kazuto YAMAUCHI.
Application Number | 20140230848 14/261005 |
Document ID | / |
Family ID | 47068146 |
Filed Date | 2014-08-21 |
United States Patent
Application |
20140230848 |
Kind Code |
A1 |
YAMAUCHI; Kazuto ; et
al. |
August 21, 2014 |
METHOD OF CLEANING SUBSTRATE
Abstract
The present invention is a method of cleaning a substrate,
comprising cleaning at least one surface of a substrate located in
a liquid by injecting pressurized cleaning liquid containing
bubbles or cleaning particles from a injection nozzle to at least
one surface of the substrate.
Inventors: |
YAMAUCHI; Kazuto;
(Suita-shi, JP) ; SHOKI; Tsutomu; (Shinjuku-ku,
JP) ; YAMADA; Takeyuki; (Shinjuku-ku, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OSAKA UNIVERSITY
HOYA CORPORATION |
Osaka
Tokyo |
|
JP
JP |
|
|
Assignee: |
HOYA CORPORATION
Tokyo
JP
OSAKA UNIVERSITY
Osaka
JP
|
Family ID: |
47068146 |
Appl. No.: |
14/261005 |
Filed: |
April 24, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13455740 |
Apr 25, 2012 |
8748062 |
|
|
14261005 |
|
|
|
|
Current U.S.
Class: |
134/7 ;
134/36 |
Current CPC
Class: |
B24C 1/04 20130101; G03F
1/82 20130101; B24C 7/0007 20130101; B08B 3/02 20130101; H01L
21/67057 20130101; H01L 21/67051 20130101; H01L 21/02052
20130101 |
Class at
Publication: |
134/7 ;
134/36 |
International
Class: |
H01L 21/02 20060101
H01L021/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 26, 2011 |
JP |
2011-098480 |
Claims
1. A method of cleaning a substrate, comprising cleaning at least
one surface of the substrate by injecting pressurized cleaning
liquid from a injection nozzle to the at least one surface of the
substrate, wherein the cleaning liquid containing bubbles or
cleaning particles is supplied to the nozzle with pressurized
state, the substrate and the nozzle are located in a liquid, and
the pressurized cleaning liquid is injected from the injection
nozzle to the liquid, so that the at least one surface of the
substrate is cleaned by the pressurized cleaning liquid that is
injected to the liquid.
2. The method of cleaning the substrate according to claim 1,
wherein the cleaning liquid is pure water.
3. The method of cleaning the substrate according to claim 1,
wherein the cleaning liquid further contains a surfactant.
4. The method of cleaning the substrate according to claim 2,
wherein the cleaning liquid further contains an acidic substance or
an alkaline substance.
5. The method of cleaning the substrate according to claim 1,
wherein the injection nozzle has an opening with a shape of a slit
or a pinhole.
6. The method of cleaning the substrate according to claim 1,
wherein the cleaning particles is latex particles.
7. The method of cleaning the substrate according to claim 1,
wherein the substrate comprises a glass material.
8. The method of cleaning the substrate according to claim 1,
wherein the substrate comprises a synthetic quartz glass or a low
thermal expansion glass.
Description
[0001] This is a Divisional of application Ser. No. 13/455,740
filed Apr. 25, 2012, claiming priority based on Japanese Patent
Application No. 2011-098480 filed on Apr. 26, 2011 the contents of
all of which are incorporated herein by reference in their
entirety.
TECHNICAL FIELD
[0002] The present invention relates to a method of manufacturing a
mask blank substrate used for fabrication of a transfer mask, such
as a photomask used in manufacture of an electronic device like a
semiconductor device, a mask blank and a transfer mask, and a
method of cleaning a transfer mask.
BACKGROUND OF THE INVENTION
[0003] In general, in the manufacturing processes of a
semiconductor device, a fine pattern is formed using
photolithography. For the formation of a fine pattern, many
substrates called as photomasks are normally used. Herein, a
substrate used for formation of a fine pattern using
photolithography, such as a photomask, and the substrate provided
with a transfer pattern is referred to as "a transfer mask". In
general, this transfer mask is equipped with a fine pattern made of
a metal thin film or the like on a transparent glass substrate.
Photolithography is used for the manufacture of a transfer
mask.
[0004] For the manufacture of a transfer mask by photolithography,
a mask blank is used. The mask blank has a thin film, such as light
shielding film, for formation of a transfer pattern on a
transparent substrate, such as a glass substrate. Herein, a
transfer pattern may also be referred to as "a mask pattern".
Manufacture of a transfer mask using the mask blank comprises steps
of: exposing to form a desired pattern to a resist film formed on a
mask blank; developing the resist film in accordance with the
desired pattern to form a resist pattern; etching the thin film in
accordance with the resist pattern; and stripping and removing the
remained resist pattern. In the developing step, after forming the
desired pattern to the resist film formed on the mask blank,
developer is supplied to dissolve a portion of the resist film
soluble in the developer for formation of the resist pattern. In
the etching step, using this resist pattern as a mask, a portion of
the exposed thin film where the resist pattern is not formed is
dissolved by dry etching or wet etching, thereby forming the
desired mask pattern on the transparent substrate. Thus, a transfer
mask is produced.
[0005] In the steps of manufacturing a glass substrate for a mask
blank used for manufacture of the transfer mask, cleaning is
performed for the glass substrate after mirror polishing for
removing particles, such as a foreign substance, for example, on a
surface of the substrate. Conventionally, several methods are known
for the cleaning.
[0006] For example, in Japanese Laid-Open Patent [Kokai]
Publication No. 2000-173965, a cleaning method using a high speed
shear flow is disclosed. In the cleaning method using a high speed
shear flow described in Japanese Laid-Open Patent [Kokai]
Publication No. 2000-173965, objects to be cleaned and high
pressure nozzles are disposed at predetermined intervals in a
process tank mainly of ultrapure water, and high speed shear flow
of the ultrapure water injected from the high pressure nozzles are
generated near the surfaces of the objects to be cleaned. With the
high speed shear flow, fine foreign substances attached to the
surfaces of the objects to be cleaned are stripped by breaking the
bond with the surfaces of the objects to be cleaned. Further, the
high speed shear flow prevents the removed foreign substances from
reattaching to the surfaces of the objects to be cleaned.
[0007] In Japanese Laid-Open Patent [Kokai] Publication No.
2007-201186, an apparatus for cleaning a substrate is disclosed,
which cleans a substrate by supplying a cleaning fluid to one
surface of a surface to be cleaned. The apparatus for cleaning
substrate of Japanese Laid-Open Patent [Kokai] Publication No.
2007-201186 comprises a cleaning fluid supply unit supplying a
cleaning fluid to the surface of the substrate to be cleaned,
equipped towards a surface of a substrate to be cleaned, and a
cleaning roller equipped towards the surface of the substrate to be
cleaned so as to be approximately parallel to the cleaning fluid
supply unit and also feeding the cleaning fluid into a gap formed
with the surface of the substrate to be cleaned by rotation.
[0008] In addition, as a cleaning method for removing particles on
a substrate surface, there is a method of cleaning a substrate
surface by striking cleaning water with ultrasonic of about 1 MHz
applied directly to the substrate surface. This cleaning is
referred to as "megasonic cleaning".
[0009] As one example of the megasonic cleaning, Japanese Laid-Open
Patent [Kokai] Publication No. 2001-96241 discloses a method of
cleaning a precision substrate, such as a mask blank substrate,
using a cleaning fluid made by mixing ozonized water or anode water
with hydrogenated water or cathode water, and applying ultrasonic
to the cleaning fluid. In addition, Japanese Laid-Open Patent
[Kokai] Publication No. 2005-221928 discloses that the megasonic
cleaning is performed, for example, with supplying a cleaning
fluid, with ultrasonic applied thereto, to a surface of a
transparent substrate, after etching process on a surface of a
transparent substrate using an etching fluid, as an example of
physical cleaning utilizing a physical action for removing foreign
substances attached on the substrate surface.
[0010] In addition, in recent years, as a method of cleaning a
substrate to clean a substrate surface, such as a semiconductor
wafer, a two-fluid-jet cleaning method is used. For example, a
cleaning method for removing contaminants on a substrate surface
using the two-fluid-jet cleaning method is described in Japanese
Laid-Open Patent [Kokai] Publication No. 2008-226900.
[0011] On the other hand, in recent years, because of a demand for
miniaturization of semiconductor devices, there is an exposure
technique using an extreme ultraviolet light. Hereinafter, an
extreme ultraviolet is referred to as "EUV". EUV lithography is
highly expected, which is one of reflective lithography. Here, EUV
light refers to light in a wavelength band of the soft x-ray region
or the vacuum ultraviolet region, and specifically to light having
a wavelength approximately from 0.2 to 100 nm. As a mask used for
the EUV lithography, a reflective mask for exposure described in
Japanese Laid-Open Patent [Kokai] Publication No. 2002-122981, for
example, is proposed.
[0012] The reflective mask described above has a multilayer
reflective film to reflect exposure light formed on a substrate and
has an absorber film with a pattern formed on the multilayer
reflective film to absorb exposure light. Light introduced to a
reflective mask mounted to an exposure apparatus (a pattern
transfer apparatus) is absorbed in an area with the absorber film,
and an optical image reflected by the multilayer reflective film in
an area without the absorber film through a reflective optical
system is transferred on a semiconductor substrate.
BRIEF SUMMARY OF THE INVENTION
[0013] In recent years, an ArF excimer laser is applied to the
exposure light for a transfer mask to which light-transmitting
photolithography is applied. In addition, there has been
significant miniaturization of transfer patterns in transfer masks.
Therefore, demands for the defect size and a number thereof
required to mask blanks have also become strict. One of the major
factors of generating convex defects in a thin film for pattern
formation of a mask blank is attachment of foreign substances on a
surface of a substrate before forming a thin film. Therefore, it is
important to remove foreign substances from a surface where a thin
film forms.
[0014] In contrast, in a case of the EUV reflective mask blank, its
demand for surface defects is extremely strict. In a case of
fabricating a reflective mask blank or a reflective mask using a
glass substrate with convex defects due to attachment of foreign
substances and the like on the substrate surface, when the convex
defects are near the pattern on the mask surface, a phase change
due to the convex defects occurs in a reflected light of the
exposure light. This phase change causes deterioration in the
positional accuracy and the contrast of the transferred pattern.
Particularly in a case of using light having a short wavelength,
such as EUV light, as the exposure light, the phase change becomes
very sensitive to minute concavity and convexity on the mask
surface and thus the transfer image is greatly influenced, so that
the phase change derived from minute concavity and convexity is not
a negligible problem. In addition, the EUV reflective mask blank
has a multilayer reflective film with, for example, Mo and Si
layers having each thickness of several nanometers being laminated
alternately from about 40 to 60 cycles. Therefore, even if there
are small convex defects that look like that they do not cause any
particular problem on the substrate surface, the size of the
defects on the substrate surface is enlarged upon forming the
multilayer reflective film, and convex defects with sizes
potentially causing phase defects on a surface of the multilayer
reflective film are sometimes generated. For such reasons,
particularly in a case of the EUV reflective mask blank, it is
required to satisfy the conditions at a very high level to the
surface defects.
[0015] In the cleaning method using a high speed shear flow, with
regards to relatively large foreign substances, for example,
foreign substances in a size of the 100 nm order or more, it is
possible to wash out the foreign substances on the substrate
surface with the high speed shear flow. However, even if the high
speed shear flow strikes on a surface of a substrate, high speed
shear flow is hard to act on relatively small foreign substances,
for example, foreign substances in a size of less than 100 nm. The
reason is assumed that, since a high speed shear flow is a flow of
a liquid, the flow rate of the high speed shear flow greatly
decreases near the substrate surface because of the viscosity of
the liquid. Therefore, it is difficult to remove foreign substances
in a relatively small size from a surface of a substrate with the
cleaning method using a high speed shear flow.
[0016] In order to clean a substrate used for a mask blank,
megasonic cleaning is sometimes used. However, the present inventor
has found that the conventional megasonic cleaning had the
following problems. That is, in such a megasonic cleaning method,
in a case of cleaning by striking a cleaning liquid with ultrasonic
at low frequencies relatively lower in the MHz band applied
directly to a surface of a glass substrate, the action of stripping
deposits on the substrate surface is high and a very high cleaning
effect is obtained. However, the vibration given by the ultrasonic
to the molecular structure constituting an surface layer of the
glass substrate is also great, and thus latent defects are
sometimes generated in an area of weaker bonding structure inside
the glass substrate compared with the surrounding area of the glass
substrate. By a conventional defect inspection for substrates, it
is very difficult to find such latent defects. Therefore, a
substrate comprising latent defects on the surface layer is
sometimes sent to a thin film formation step, which is the next
step, then thin film for transfer pattern is formed, and a mask
blank having the substrate comprising latent defects on the surface
layer is shipped as a mask blank of an acceptable product.
[0017] With that, the present invention is made to solve the
problems in a case of using a conventional cleaning method, such as
cleaning using a high speed shear flow and megasonic cleaning, for
example, and to obtain an appropriate cleaning method even for
cleaning of a substrate for a light-transmitting transfer mask and
a substrate for an EUV reflective mask blank. It is an object of
the present invention to provide a method of cleaning a substrate,
such as a mask blank substrate, which is capable of inhibiting
generation of latent defects inside a glass substrate during
cleaning the mask blank substrate and also capable of certainly
removing particles on a main surface of the substrate. It is also
an object of the present invention to provide a method of
manufacturing a mask blank substrate , a method of manufacturing a
mask blank, a method of manufacturing a reflective mask, and a
method of manufacturing a transfer mask that use the cleaning
method.
[0018] It is also an object of the present invention to provide a
substrate with a multilayer reflective film and a reflective mask
blank that are high quality with a reduced number of tiny convex
defects to satisfy high level demands for defect quality and a
method of manufacturing the same.
[0019] It is also an object of the present invention to provide an
apparatus for cleaning substrate to be used for a method of
cleaning a substrate, such as a mask blank substrate, which is
capable of inhibiting generation of latent defects inside a glass
substrate during cleaning the mask blank substrate and also capable
of certainly removing particles on a main surface of the
substrate.
[0020] As a result of intensive studies to solve the problems, the
present inventor has found that a cleaning method using pressurized
cleaning liquid comprising bubbles or cleaning particles. By using
the method of cleaning a substrate of the present invention, it is
possible to inhibit generation of latent defects inside a glass
substrate, which becomes a problem in a case of megasonic cleaning,
and it is also possible to certainly remove a particle on a main
surface of a substrate and a surface of a thin film for transfer
pattern formation on a mask blank, particularly removing micro
particles equivalent to less than 100 nm, for example. In order to
solve the problems, the present invention comprises the following
configurations.
[0021] The present invention is a method of cleaning a substrate
according to Configurations 1 through 5 below.
Configuration 1
[0022] Configuration 1 is a method of cleaning a substrate,
comprising cleaning at least one surface of the substrate located
in a liquid by injecting pressurized cleaning liquid containing
bubbles or cleaning particles from a injection nozzle to at least
one surface of the substrate.
Configuration 2
[0023] Configuration 2 is the method of cleaning the substrate
according to Configuration 1, wherein the cleaning liquid is pure
water.
Configuration 3
[0024] Configuration 3 is the method of cleaning the substrate
according to Configuration 2, wherein the cleaning liquid further
contains a surfactant.
Configuration 4
[0025] Configuration 4 is the method of cleaning the substrate
according to Configuration 2 or 3, wherein the cleaning liquid
further contains an acidic substance or an alkaline substance.
Configuration 5
[0026] Configuration 5 is the method of cleaning the substrate
according to any one of Configurations 1 through 4, wherein the
injection nozzle has an opening with a shape of a slit or a
pinhole.
[0027] The present invention is a method of manufacturing a mask
blank substrate according to any one of Configurations 6 through 8
below.
Configuration 6
[0028] Configuration 6 is a method of manufacturing a mask blank
substrate, comprising cleaning at least one surface of the
substrate in the method of cleaning the substrate according to any
one of Configurations 1 through 5.
Configuration 7
[0029] Configuration 7 is the method of manufacturing the mask
blank substrate according to Configuration 6, wherein the substrate
comprises a glass material.
Configuration 8
[0030] Configuration 8 is the method of manufacturing the mask
blank substrate according to Configuration 7, wherein the substrate
comprises a synthetic quartz glass or a low thermal expansion
glass.
[0031] The present invention is a method of manufacturing a mask
blank or a mask according to Configurations 9 through 12 below.
Configuration 9
[0032] Configuration 9 is a method of manufacturing a mask blank,
comprising forming a thin film for forming a transfer pattern on a
surface of the mask blank substrate, wherein the mask blank
substrate is obtained by the method of manufacturing the mask blank
substrate for the mask blank according to any one of Configurations
6 through 8.
Configuration 10
[0033] Configuration 10 is a method of manufacturing a reflective
mask blank, comprising: forming a multilayer reflective film to
reflect exposure light on a surface of a mask blank substrate,
wherein the mask blank substrate is obtained by the method of
manufacturing the mask blank substrate according to any one of
Configurations 6 through 8; and forming a thin film for forming a
transfer pattern on the multilayer reflective film.
Configuration 11
[0034] Configuration 11 is a method of manufacturing a transfer
mask, comprising forming the transfer pattern by patterning the
thin film of the mask blank obtained by the method of manufacturing
the mask blank according to Configuration 9.
Configuration 12
[0035] Configuration 12 is a method of manufacturing a reflective
mask, comprising forming the transfer pattern by patterning the
thin film of a reflective mask blank obtained by the method of
manufacturing a reflective mask blank according to Configuration
10.
[0036] The present invention is an apparatus for cleaning a
substrate according to any one of Configurations 13 through 17
below.
Configuration 13
[0037] Configuration 13 is an apparatus for cleaning a substrate,
comprising: a cleaning container; a substrate-fixing-base located
in the cleaning container to fix a substrate; a
cleaning-liquid-tube having a injection nozzle to supply a cleaning
liquid into the cleaning container, wherein the
cleaning-liquid-tube is located so as to inject the cleaning liquid
from the injection nozzle to the substrate fixed on the
substrate-fixing-base; a cleaning-liquid-pressurizing-device
connected to the cleaning-liquid-tube to pressurize the cleaning
liquid; and a mixing unit to mix bubbles or cleaning particles into
the cleaning liquid.
Configuration 14
[0038] Configuration 14 is the apparatus for cleaning the substrate
according to Configuration 13, wherein the mixing unit is a nozzle
for bubble generation to generate the bubble by supplying a gas at
a pressure higher than that of the cleaning liquid into the
cleaning liquid pressurized in the cleaning-liquid-tube.
Configuration 15
[0039] Configuration 15 is the apparatus for cleaning the substrate
according to Configuration 13, wherein the mixing unit is a
cleaning-particle-mixing-unit to mix the cleaning particle into the
cleaning liquid, and the cleaning-particle-mixing-unit is connected
to the cleaning-liquid-pressurizing-device to allow the cleaning
liquid having the cleaning particle mixed therein to move to the
cleaning-liquid-pressurizing-device.
Configuration 16
[0040] Configuration 16 is the apparatus for cleaning the substrate
according to any one of Configurations 13 through 15, wherein the
injection nozzle has an opening with a shape of a slit or a
pinhole.
Configuration 17
[0041] Configuration 17 is the apparatus for cleaning the substrate
according to any one of Configurations 13 through 16, wherein the
substrate comprises a glass material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] FIG. 1 is a configuration diagram illustrating one example
of an apparatus for cleaning substrate of the present
invention.
[0043] FIG. 2 is a configuration diagram illustrating another
example of an apparatus for cleaning substrate of the present
invention.
[0044] FIG. 3 is a schematic diagram illustrating a mask blank
substrate that can be used for a manufacturing method of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0045] Next, Configurations 1 through 5 of the method of cleaning a
substrate of the present invention are described.
[0046] The present invention as described in Configuration 1 is a
method of cleaning a substrate, comprising cleaning at least one
surface of a substrate located in a liquid by injecting pressurized
cleaning liquid containing bubbles or cleaning particles from a
injection nozzle to at least one surface of the substrate.
[0047] As described in Configuration 1, the cleaning method of the
present invention is characterized in that pressurized cleaning
liquid containing bubbles or cleaning particles is injected from an
injection nozzle to at least one surface of a substrate located in
a liquid. Since the cleaning liquid is injected from the injection
nozzle in a pressurized state, it is possible to detach and remove
particles, such as foreign substances in a relatively large size,
attached on the surface of the substrate from the substrate.
Further, since the cleaning liquid contains bubbles or cleaning
particles, the bubble or the cleaning particle can directly hit
foreign substances in a relatively small size, such as particles
like foreign substances in a size of, for example, less than 100
nm, attached on the surface of the substrate. As the result,
according to the cleaning method of the present invention, it is
possible to certainly carry out removal of particles attached on
the surface of the substrate.
[0048] In the cleaning method of the present invention, in a case
that the pressurized cleaning liquid contains bubbles, the
pressurized cleaning liquid is injected from the injection nozzle
into a liquid with relatively low pressure in which the substrate
is located. At this time, the compressed bubble rapidly expands
with emitting energy of the pressurization to directly hit
particles, such as foreign substances in a relatively small size,
attached on the surface of the substrate. As the result, it is
possible to certainly carry out removal of particles attached on
the surface of the substrate. As the gas, air, nitrogen, and/or an
inert gas can be used. From the view of the costs, it is preferred
to use air from which particles are removed with a dust filter.
[0049] In the cleaning method of the present invention, in a case
that the pressurized cleaning liquid contains cleaning particles,
the pressurized cleaning liquid is injected and accelerated from
the injection nozzle into the liquid in low pressure in which the
substrate is located. At this time, since the cleaning particle is
accelerated similar to the cleaning liquid, the cleaning particle
obtains large momentum. Since this cleaning particle hits the
particles, such as foreign substances, attached on the surface of
the substrate, it is possible to remove the particles attached on
the surface of the substrate.
[0050] As the cleaning particle, it is possible to use a particle
that has hardness that may not damage the substrate and the
particle that is easily soluble to chemicals, such as acid, can be
used. Specifically, it is preferred to use a latex particle as the
cleaning particle. In a case of using a latex particle, even if the
latex particle remains, the remained latex particle can be
dissolved when cleaning with acid or the like in a following
step.
[0051] As the liquid in which the substrate is located, it is
possible to use a liquid that is the same type as the cleaning
liquid. Specifically, it is possible to use a liquid similar to the
cleaning liquid, generally used for cleaning a mask blank
substrate, such as ultrapure water, pure water, or deionized water,
for example, although it is not limited to those.
[0052] Since the substrate subjected to the cleaning is located in
the liquid, the pressurized cleaning liquid is injected to the
surface of the substrate in the liquid. Therefore, a certain
differential pressure is required between the pressure of the
injected cleaning liquid and the pressure of the liquid near the
substrate surface. The differential pressure between the pressure
of pressurization to the cleaning liquid by the
cleaning-liquid-pressurizing-device and the pressure of the liquid
near the substrate surface is at least 1 atmosphere (atm, 101325
Pa) or more, preferably 3 atmospheres or more, and more preferably
5 atmospheres or more, thereby enabling effective removal of the
particles attached on the substrate. The higher differential
pressure becomes more effective. However, in a case of the high
differential pressure, the cleaning-liquid-pressurizing-device is
required to have very high performance. Considering this point, the
differential pressure is 20 atmospheres or less, preferably 15
atmospheres or less, and more preferably 12 atmospheres or
less.
[0053] As described in Configuration 2, the present invention is
the method of cleaning a substrate of Configuration 1, wherein the
cleaning liquid is pure water.
[0054] As described in Configuration 2, as the cleaning liquid, it
is preferred to use pure water. By using pure water as the cleaning
liquid, it is possible to remove the presence of foreign substances
and the like in the cleaning liquid, and it is possible to prevent
secondary contamination during cleaning. The pure water may be, for
example, ultrapure water and deionized water, but it is not limited
to them.
[0055] As described in Configuration 3, in the method of cleaning a
substrate of the present invention, the cleaning liquid can also
further contain a surfactant.
[0056] As described in Configuration 3, the cleaning liquid, such
as pure water, contains a surfactant, thereby enabling more certain
removal of particles from the surface of the substrate.
[0057] As described in Configuration 4, in the method of cleaning a
substrate of the present invention, the cleaning liquid can also
further contain an acidic substance or an alkaline substance.
[0058] As described in Configuration 4, the cleaning liquid
contains an acidic substance or an alkaline substance, thereby
enabling to obtain an effect of cleaning the substrate surface by
acid or alkali.
[0059] As described in Configuration 5, in the method of cleaning a
substrate of the present invention, it is preferred that the
injection nozzle has an opening with a shape of a slit or a
pinhole.
[0060] As described in Configuration 5, in the method of cleaning a
substrate of the present invention, the shape of the injection
nozzle can be in a shape, such as a slit shape that is a nozzle
shape of an elongated rectangular or a pinhole shape that is a
nozzle shape of a tiny circular. In a case of a nozzle shape of a
slit shape, cleaning can be treated linearly over a wide region, so
that the throughput of the cleaning treatment can be increased. In
a case of a nozzle shape with a pinhole shape, the cleaning liquid
can be injected at a high pressure from a small cross sectional
area, so that it is possible to remove particles attached
relatively rigidly to the substrate. In addition, it is also
possible to use a product having a plurality of pinhole nozzles
aligned in one line or in other alignments as the injection nozzle.
The shape of the injection nozzle is preferably in a shape of
enabling to prevent cavitation hydrodynamically.
[0061] Next, Configurations 6 through 8 of a method of
manufacturing a mask blank substrate of the present invention are
described.
[0062] As described in Configuration 6, the present invention is a
method of manufacturing a mask blank substrate, comprising cleaning
at least one surface of the substrate in the method of cleaning the
substrate according to any one of Configurations 1 through 5.
[0063] As described in Configuration 6, the method of manufacturing
the mask blank substrate of the present invention comprises
cleaning of at least one surface of the substrate in the method of
cleaning a substrate according to any one of Configurations 1
through 5. According to the method of cleaning the substrate
according to any one of Configurations 1 through 5 above, it is
possible to certainly remove particles attached on the surface of
the substrate. As the result, according to the method of
manufacturing the mask blank substrate of the present invention, it
is possible to obtain a mask blank substrate with significantly
reduced defects due to the particles.
[0064] As described in Configuration 7, it is preferred that the
present invention is the method of manufacturing the mask blank
substrate of Configuration 6, wherein the substrate comprises a
glass material.
[0065] As described in Configuration 7, the substrate is made of a
glass material, thereby enabling to certainly manufacture a mask
blank substrate.
[0066] As described in Configuration 8, in the method of
manufacturing the mask blank substrate of the present invention, it
is preferred that the substrate comprises a synthetic quartz glass
or a low thermal expansion glass.
[0067] As described in Configuration 8, it is preferred to use a
synthetic quartz glass or a low thermal expansion glass as a
material for the substrate. A synthetic quartz glass has
characteristics, such as being chemically stable and having an
extremely small thermal expansion coefficient in comparison with
other materials. The synthetic quartz glass is also high in light
transparency to exposure light of an extra high pressure mercury
lamp used for a transfer mask in an FPD (Flat Panel Display)
manufacturing application. Further, the synthetic quartz glass is
also high in light transparency to exposure light of a KrF excimer
laser having a wavelength of approximately 248 nm and an ArF
excimer laser having a wavelength of approximately 193 nm used for
a transfer mask in a semiconductor device manufacture application.
As seen from these, the synthetic quartz glass can be used
preferably as a material for the mask blank substrate.
[0068] A low thermal expansion glass is preferably used as a
substrate for a reflective mask blank using EUV light as the
exposure light. In order to prevent pattern deformation due to the
heat at the time of exposure, the low thermal expansion glass has a
low thermal expansion coefficient preferably within a range of
0.+-.1.0.times.10.sup.-7/.degree. C. and more preferably within a
range of 0.+-.0.3.times.10.sup.-7/.degree. C. A material having a
low thermal expansion coefficient within the ranges may preferably
comprise, for example, a SiO.sub.2-TiO.sub.2 based glass substrate
having TiO.sub.2 within a range, for example, from about 5 to about
10 weight % added to SiO.sub.2, in a case of an amorphous glass.
The SiO.sub.2-TiO.sub.2 based glass having TiO.sub.2 added thereto
is sometimes difficult to be cleaned with chemicals, so that it is
possible to clean preferably in the cleaning method of the present
invention.
[0069] Next, Configurations 9 and 10 of a method of manufacturing a
mask blank of the present invention are described.
[0070] As described in Configuration 9, the present invention is a
method of manufacturing a mask blank, comprising forming a thin
film for forming a transfer pattern on a surface of the mask blank
substrate obtained by the method of manufacturing the mask blank
substrate according to any one of Configurations 6 through 8.
[0071] As described in Configuration 9, in the method of
manufacturing the mask blank substrate according to any one of
Configurations 6 through 8 above, it is possible to certainly
remove particles attached on the surface of the substrate by a
predetermined method of cleaning the substrate. As the result, it
is possible to obtain a mask blank substrate with significantly
reduced defects due to the particles. Therefore, a mask blank with
a thin film for pattern formation formed on the mask blank
substrate obtained by the method of manufacturing the mask blank
substrate according to any one of Configurations 6 through 8 above
can also significantly reduce defects due to particles for high
yield. The thin film for formation of the transfer pattern on the
mask blank substrate can be formed using a known method.
[0072] As described in Configuration 10, the present invention is a
method of manufacturing a reflective mask blank, comprising:
forming a multilayer reflective film to reflect exposure light on a
surface of the mask blank substrate obtained by the method of
manufacturing the mask blank substrate according to any one of
Configurations 6 through 8; and forming a thin film for forming a
transfer pattern on the multilayer reflective film.
[0073] As described in Configuration 10, in the method of
manufacturing the mask blank substrate according to any one of
Configurations 6 through 8 above, it is possible to certainly
remove particles attached on the surface of the substrate of the
reflective mask blank by the predetermined method of cleaning the
substrate. As the result, it is possible to obtain a mask blank
substrate with significantly reduced defects due to the particles.
Therefore, a reflective mask blank having a thin film, an absorber
film for example, formed thereon to form a transfer pattern on the
multilayer reflective film to reflect exposure light formed on a
surface of a mask blank substrate obtained by the method of
manufacturing the substrate for the mask blank according to any one
of Configurations 6 through 8, can also significantly reduce
defects due to particles and it is possible to obtain high yield
for reflective mask blanks. The multilayer reflective film and the
thin film for formation of the transfer pattern on the mask blank
substrate can be formed using a known method.
[0074] Next, Configurations 11 and 12 of a method of manufacturing
a mask of the present invention are described.
[0075] The present invention as described in Configuration 11 is a
method of manufacturing a transfer mask, comprising forming the
transfer pattern by patterning the thin film of the mask blank
obtained by the method of manufacturing the mask blank of
Configuration 9.
[0076] As described in Configuration 11, the mask blank obtained by
the method of manufacturing the mask blank of Configuration 9 can
significantly reduce defects due to particles for high yield.
Therefore, the transfer mask having a transfer pattern formed on
the thin film of the mask blank obtained by Configuration 9 can
also significantly reduce defects due to particles for high yield.
The formation of the transfer pattern to the thin film of the mask
blank can be carried out using a known method.
[0077] The present invention as described in Configuration 12 is a
method of manufacturing a reflective mask, comprising forming the
transfer pattern by patterning the thin film of a reflective mask
blank obtained by the method of manufacturing a reflective mask
blank of Configuration 10.
[0078] As described in Configuration 12, the reflective mask blank
obtained by the method of manufacturing a reflective mask blank of
Configuration 10 can significantly reduce defects due to particles
for high yield. Therefore, the reflective mask having a transfer
pattern formed on the thin film of the reflective mask blank
obtained by Configuration 10 can also significantly reduce defects
due to particles for high yield. The formation of the transfer
pattern on the thin film of the reflective mask blank can be
carried out using a known method.
[0079] Next, Configurations 13 through 17 of an apparatus for
cleaning substrate of the present invention are described.
[0080] As described in Configuration 13, the present invention is
an apparatus for cleaning substrate, comprising: a cleaning
container; a substrate-fixing-base located in the cleaning
container to fix a substrate; a cleaning-liquid-tube having a
injection nozzle to supply a cleaning liquid into the cleaning
container, wherein the cleaning-liquid-tube is located so as to
inject the cleaning liquid from the injection nozzle to the
substrate fixed on the substrate-fixing-base; a
cleaning-liquid-pressurizing-device connected to the
cleaning-liquid-tube to pressurize the cleaning liquid; and a
mixing unit to mix bubbles or cleaning particles into the cleaning
liquid.
[0081] As described in Configuration 13, the apparatus for cleaning
substrate of the present invention comprises a cleaning container,
a substrate-fixing-base, a cleaning-liquid-tube, a
cleaning-liquid-pressurizing-device, and a mixing unit.
[0082] It is preferred that the cleaning container has a size
sufficient to maintain the liquid and to have the substrate located
on the substrate-fixing-base. In order to avoid contamination in
the liquid, the material for the cleaning container is preferably a
material not emitting a contaminant, particles, and the like in the
liquid.
[0083] The substrate-fixing-base is located in the cleaning
container. The substrate-fixing-base enables to fix the substrate
in the cleaning container. The fixation of the substrate by the
substrate-fixing-base can be carried out by a known mechanism, such
as a known spin chuck, for example. The substrate-fixing-base can
have a rotatable structure using an electric motor. It is also
possible to clean the two main surfaces of the substrate at the
same time by using two injection nozzles. The two main surfaces of
the substrate mean the two "main surfaces 71" facing to each other
as shown in FIG. 3.
[0084] The cleaning-liquid-tube comprises an injection nozzle to
supply a cleaning liquid into the cleaning container. The injection
nozzle is located to inject the cleaning liquid to the substrate
fixed on the substrate-fixing-base. It can be configured that,
while cleaning, the position of the injection nozzle can be moved
by, for example, swinging between the center of the substrate and
the edge surfaces while rotating the substrate at a predetermined
rotation speed. As the result, in a case that the
substrate-fixing-base has a rotatable structure, it is possible to
inject the cleaning liquid to the entire surface of the substrate
from the injection nozzle by rotation of the substrate-fixing-base
and by moving the injection nozzle. It is also possible to have a
structure with a fixed injection nozzle and the structure that
allows the substrate rotated and/or moved. It is also possible to
have a structure of injecting the cleaning liquid by fixing the
substrate and to move the injection nozzle. Further, it is also
possible to have a structure of moving the injection nozzle only to
allow the cleaning liquid to be injected to the entire substrate
and the structure with the substrate fixed.
[0085] The cleaning-liquid-pressurizing-device is a device to
pressurize the cleaning liquid. The
cleaning-liquid-pressurizing-device is connected to the
cleaning-liquid-tube. As the result, the cleaning liquid
pressurized by the cleaning-liquid-pressurizing-device can be
injected through the cleaning-liquid-tube from the injection nozzle
into the cleaning container.
[0086] The mixing unit is configured to mix bubbles or cleaning
particles into the cleaning liquid. The mixing unit can be
configured to mix bubbles or cleaning particles into the
pressurized cleaning liquid. The mixing unit can be configured to
mix bubbles or cleaning particles into the cleaning liquid before
pressurization.
[0087] As described in Configuration 14, in the apparatus for
cleaning substrate of the present invention, it is preferred that
the mixing unit is a nozzle for bubble generation to generate the
bubble by supplying a gas at a pressure higher than that of the
cleaning liquid, into the cleaning liquid pressurized in the
cleaning-liquid-tube.
[0088] As described in Configuration 14, in the apparatus for
cleaning substrate of the present invention, bubbles can be
generated in the cleaning liquid by supplying a gas at a pressure
higher than that of the cleaning liquid, into the cleaning liquid
from the nozzle for bubble generation. The bubble is injected from
the injection nozzle to the substrate together with the cleaning
liquid. As the result, it is possible to remove particles attached
on the substrate surface. The gas can be pressurized using a known
gas pressurizer, such as a compressor.
[0089] As described in Configuration 15, in the apparatus for
cleaning substrate of the present invention, it is preferred that
the mixing unit is a cleaning-particle-mixing-unit to mix the
cleaning particle into the cleaning liquid, and the
cleaning-particle-mixing-unit is connected to the
cleaning-liquid-pressurizing-device to allow the cleaning liquid
having the cleaning particle mixed therein to move to the
cleaning-liquid-pressurizing-device.
[0090] As described in Configuration 15, the apparatus for cleaning
substrate of the present invention can mix cleaning particles into
the cleaning liquid by comprising a cleaning-particle-mixing-unit
to mix cleaning particles into the cleaning liquid. Since the
cleaning-particle-mixing-unit is connected to the
cleaning-liquid-pressurizing-device, the cleaning liquid having the
cleaning particle mixed therein can be pressurized and injected
from the injection nozzle to the substrate. As the result, it is
possible to remove particles attached on the substrate surface. The
cleaning particle can be mixed into the cleaning liquid immediately
before use, or the cleaning particle is mixed in the cleaning
liquid in advance and the cleaning liquid with the cleaning
particle can be set in the apparatus for cleaning substrate.
[0091] As described in Configuration 16, in the apparatus for
cleaning substrate of the present invention, it is preferred that
the injection nozzle has an opening with a shape of a slit or a
pinhole.
[0092] As described in Configuration 16, in the method of cleaning
a substrate of the present invention, the shape of the injection
nozzle can be in a shape, such as a slit shape that is a nozzle
shape of an elongated rectangular shape or a pinhole shape that is
a nozzle shape of a tiny circular shape. In a case of a nozzle
shape of a slit shape, cleaning can be treated linearly over a wide
region, so that the throughput of the cleaning treatment can be
improved. In a case of a nozzle shape with a pinhole shape, the
cleaning liquid can be injected at a high pressure from a small
cross sectional area, so that it is possible to remove particles
attached relatively rigidly to the substrate. In addition, it is
also possible to use a product having a plurality of pinhole
nozzles aligned in one line or in other alignments as the injection
nozzle. The shape of the injection nozzle is preferably in a shape
of enabling to prevent cavitation hydrodynamically.
[0093] The material for the injection nozzle can be a predetermined
material selected from known metal materials and polymer materials.
In a case that the cleaning liquid contains cleaning particles, it
is possible to select an abrasion resistant material in accordance
with the hardness of the cleaning particle and the like. In a case
of using a relatively soft latex particle or the like as the
cleaning particle, it is possible to use a material having not so
much abrasion resistance, such as a polymer material.
[0094] As described in Configuration 17, in the apparatus for
cleaning substrate of the present invention, it is preferred that
the substrate is made of a glass material.
[0095] As described in Configuration 17, the apparatus for cleaning
substrate of the present invention can preferably be used for
cleaning of a substrate made of a glass material, such as a mask
blank substrate.
[0096] According to the method of cleaning a substrate of the
present invention, it is possible to provide a method of cleaning a
substrate, such as a mask blank substrate that can certainly remove
minute particles attached on the main surface of the substrate
while cleaning the mask blank substrate. By using the cleaning
method, it is also possible to provide a method of manufacturing a
mask blank substrate, a method of manufacturing a mask blank, a
method of manufacturing a reflective mask, and a method of
manufacturing a transfer mask.
[0097] In addition, according to the apparatus for cleaning
substrate of the present invention, it is possible to provide an
apparatus for cleaning substrate used for a method of cleaning a
substrate, such as a mask blank substrate, wherein the apparatus
for cleaning substrate can certainly remove minute particles
attached on the main surface of the substrate while cleaning the
mask blank substrate.
[0098] In addition, according to the present invention, it is
possible to provide a substrate with a multilayer reflective film
and a reflective mask blank that are high quality with reduced
number of tiny convex defects to satisfy high level demands for
defect quality, and a method of manufacturing the same. According
to the manufacturing method of the present invention, it is
possible to inhibit generation of defects due to particles on the
main surface of the substrate. Therefore, according to the
manufacturing method of the present invention, it is possible to
prevent occurrence of anomalies of transmissivity and anomalies of
phase in the transfer mask. In addition, according to the
manufacturing method of the present invention, it is possible to
prevent occurrence of anomalies in the reflective mask.
[0099] A detailed description of embodiments of the present
invention is given below.
[0100] As the invention of Configuration 1 above, the present
invention is a method of cleaning a substrate, comprising cleaning
at least one surface of a substrate located in a liquid by
injecting pressurized cleaning liquid containing bubbles or
cleaning particles from an injection nozzle to at least one surface
of the substrate.
[0101] Although a substrate is not limited particularly, the method
of the present invention can preferably be used for cleaning of a
mask blank substrate made of a glass material, particularly a
substrate for a reflective mask blank.
[0102] The mask blank substrate is not particularly limited as long
as it has transparency to an exposure wavelength to be used. In the
present invention, it is possible to use a quartz substrate and
other various glass substrates, for example, a substrate of a soda
lime glass, an aluminosilicate glass, or the like. Among these
substrates, a quartz substrate particularly has high transparency
to light of an ArF excimer laser or in a region of shorter
wavelength than the ArF excimer laser, so that it is preferred as a
substrate for a binary mask blank or a substrate for a phase shift
mask blank used for formation of a high definition transfer
pattern. A description herein is given with an example of using a
glass substrate as the mask blank substrate. Accordingly, a mask
blank substrate herein may also be referred to as a glass
substrate.
[0103] As a substrate for a reflective mask blank using EUV light
for the exposure light, a low thermal expansion glass can be used
preferably. The low thermal expansion glass preferably has a low
thermal expansion coefficient within a range of
0.+-.1.0.times.10.sup.-7/.degree. C., more preferably within a
range of 0.+-.0.3.times.10.sup.-7/.degree. C. to prevent pattern
deformation due to the heat at the time of exposure. As a material
having a low thermal expansion coefficient within this range, in a
case of an amorphous glass, for example, a
SiO.sub.2-TiO.sub.2-based glass substrate that can be used
preferably, has TiO.sub.2 added within a range, for example, from
about 5 to about 10 weight %.
[0104] In the steps of manufacturing a glass substrate for a mask
blank, after a polishing step, a cleaning step is performed for
removing particles on a glass substrate surface, such as foreign
substances like abrasive particles attached to the substrate
surface, for example.
[0105] In the polishing step, a polishing pad is made contact with
the surface of the mask blank substrate, which is a glass
substrate. Then, a polishing solution containing abrasive particles
is supplied to the surface of the glass substrate, and the glass
substrate and the polishing pad are relatively moved in order to
polish the surface of the glass substrate. For example, the glass
substrate is pressed against a polishing platen with a polishing
pad adhered thereto, and the polishing platen and the glass
substrate are relatively moved while supplying a polishing solution
containing abrasive particles. By moving the polishing pad and the
substrate relatively, the surface of the glass substrate is
polished. As the abrasive particles, colloidal silica is used
preferably for at least final polishing in a precision polishing
step because good smoothness and flatness of the glass substrate
are obtained. For this polishing step, it is possible to use, for
example, a double side polishing machine with a planetary gear
system and the like.
[0106] After the polishing step, a cleaning step based on the
method of cleaning a substrate of the present invention can be
performed. FIGS. 1 and 2 are configuration diagrams illustrating
examples of an apparatus for cleaning substrate 10 used in the
cleaning step of the present invention. After the polishing step, a
cleaning step is performed that comprises cleaning of at least one
surface of a substrate 1 by injecting pressurized cleaning liquid
20 containing bubbles 30 or cleaning particles 40 from a injection
nozzle 26 towards at least one surface of the substrate 1 located
in a liquid 16. Since the cleaning liquid 20 is injected from the
injection nozzle 26 in a pressurized state, particles 3, such as
foreign substances, attached to the surface of the substrate 1 can
be detached from the substrate 1. Further, since the cleaning
liquid 20 contains the bubbles 30 or the cleaning particles 40, it
is possible to certainly remove the particles 3, such as foreign
substances, like silica particles, attached to the surface of the
substrate 1 remained in the polishing step, for example.
[0107] Because of higher density and higher precision of electronic
devices in recent years, miniaturization of transfer mask patterns
is progressing. As the result, the demands for the surface
smoothness and the surface defect of a mask blank substrate are
becoming severer, year by year, and the inspection accuracy of
defect inspection apparatus has become improved. Therefore, even a
surface defect in a small size that could not be found with a
conventional inspector, a surface defect having a particle size
equivalent to 60 nm, for example, is becoming detected. A mask
blank substrate with such a tiny surface defect should not be
accepted.
[0108] According to the present invention, a removal rate of
particles having a particle size equivalent to 60 nm or more on the
surface of the substrate 1 after cleaning is obtained as high as
98% or more relative to before cleaning. Here, the removal rate of
particles is a value calculated by the following relational
expression.
Removal Rate(%)=[(Number of Particles before Cleaning-Number of
Particles after Cleaning)/Number of Particles before
Cleaning].times.100
[0109] Specifically, using a micro-particle-applicator, particles
having a plurality of known particle sizes are applied on the
substrate 1. For example, polystyrene latex particles having a
plurality of particle sizes of 60 nm or more are applied on the
substrate 1 at a predetermined application density. The polystyrene
latex particles herein may also be referred to as PSL particles.
The PSL particles have a property that there is a probability of 1%
or less to have the particles coming close to each other within 1
mm. Next, the number of particles before cleaning is detected using
a defect inspection apparatus of, for example, sensitivity of 60
nm. The defect inspection apparatus of sensitivity of 60 nm in this
context means a defect inspection apparatus that can detect the PSL
particles, even when the defect inspection apparatus carries out
defect inspection to a specimen with scattered PSL particles having
a particle size of 60 nm on the substrate 1. After cleaning the
substrate 1, the number of particles is detected similarly using
the defect inspection apparatus. From the results, the removal rate
of the particles due to cleaning is calculated by the relational
expression.
[0110] In a case of obtaining a removal rate of particles for each
particle size, and not in a case of the removal rate of the entire
particles comprising a plurality of particle sizes as above, only
particles having a plurality of known particle sizes are applied on
the identical substrate 1 using a particle size
micro-particle-applicator. For example, PSL particles having
particle sizes of 60 nm, 90 nm, 120 nm, 150 nm, and 200 nm are
applied on the identical substrate 1 at a predetermined application
density separately in respective regions. Then, the number of
particles before cleaning for each particle size is detected using
a defect inspection apparatus of sensitivity of 60 nm, for example.
After cleaning the substrate 1, the number of particles for each
particle size is similarly detected using the defect inspection
apparatus. From the results, by the relational expression, the
removal rate by cleaning of the particles for each particle size is
calculated. According to the present invention, with regards to the
particles having a particle size equivalent to 60 nm or more, 98%
or more of the particle removal rate is obtained for any particle
size.
[0111] The apparatus for cleaning substrate 10 shown in FIG. 1 is
configured with a cleaning container 12, a substrate-fixing-base 14
to place and to fix the substrate 1 thereon to prevent moving the
substrate 1, a cleaning-liquid-tube 24 having an injection nozzle
26, and a cleaning-liquid-pressurizing-device 22 to pressurize the
cleaning liquid 20. The substrate-fixing-base 14 is located in the
cleaning container 12, and the cleaning-liquid-tube 24 is located
to allow the cleaning liquid 20 to be injected from the injection
nozzle 26 to the substrate. In order to avoid contamination in the
liquid 16, the material of the cleaning container 12 is preferably
a material not emitting contaminants, particles, and the like in
the liquid 16.
[0112] When locating the substrate 1 in the liquid 16, the
substrate 1 is located on the substrate-fixing-base 14 to be fixed
not to move the substrate 1 by the injection of the pressurized
cleaning liquid 20. At this time, it is preferred that the
substrate 1 is located on the substrate-fixing-base 14 with
avoiding contact between a main surface 71 of the substrate 1 and
the substrate-fixing-base 14. A known structure, for example, a
known spin chuck and the like can be used for the
substrate-fixing-base 14. The substrate-fixing-base 14 can have a
rotatable structure using an electric motor. The cleaning fluid
supplied from the cleaning-liquid-tube 24 can be injected to the
main surface 71 of the substrate 1 by the injection nozzle 26.
Using two injection nozzles 26, it is also possible to clean the
two main surfaces 71 of the substrate 1 at the same time. The main
surfaces 71 of the substrate 1 mean, as exemplified in FIG. 3, the
surfaces except the substrate peripheral areas. The substrate
peripheral areas refer to edge surfaces 72 and chamfered faces 73
exemplified in FIG. 3. The main surfaces 71 of the substrate 1 are
surfaces shown as the two facing main surfaces 71.
[0113] In the example of FIG. 1, the cleaning liquid 20 contains
bubbles 30. Since the cleaning liquid 20 containing the bubbles 30
is pressurized by the cleaning-liquid-pressurizing-device 22, the
particles 3 on the main surface 71 of the substrate can be removed
by the cleaning liquid 20 and the bubbles 30 injected from the
injection nozzle 26.
[0114] An apparatus for cleaning substrate 10 shown in FIG. 2 is
configured with, similar to the case of FIG. 1, a cleaning
container 12, a substrate-fixing-base 14 to place and to fix the
substrate 1 thereon to prevent moving the substrate 1, a
cleaning-liquid-tube 24 having an injection nozzle 26, and a
cleaning-liquid-pressurizing-device 22 to pressurize the cleaning
liquid 20. In the example of FIG. 2, the cleaning liquid 20
contains cleaning particles 40. Since the cleaning liquid 20
containing the cleaning particles 40 is pressurized by the
cleaning-liquid-pressurizing-device 22, the particles 3 on the main
surface 71 of the substrate can be removed by the cleaning liquid
20 and the cleaning particles 40 injected from the injection nozzle
26.
[0115] Although FIG. 1 shows an example of the cleaning liquid 20
containing the bubbles 30 and FIG. 2 shows an example of the
cleaning liquid 20 containing the cleaning particles 40, the
cleaning liquid 20 can also contain both the bubbles 30 and the
cleaning particles 40. The apparatus for cleaning substrate 10 can
also comprise at least one mechanism to mix both the bubbles 30 and
the cleaning particles 40 into the cleaning liquid 20.
[0116] The cleaning-liquid-pressurizing-device 22 is a device to
pressurize the cleaning liquid 20. The
cleaning-liquid-pressurizing-device 22 is connected to the
cleaning-liquid-tube 24. As the cleaning-liquid-pressurizing-device
22, a high pressure pump and the like can be used. As the result,
the cleaning liquid 20 pressurized by the
cleaning-liquid-pressurizing-device 22 can be injected from the
injection nozzle 26 into the cleaning container 12 through the
cleaning-liquid-tube 24. The pressure of pressurizing the cleaning
liquid 20 by the cleaning-liquid-pressurizing-device 22, in terms
of a differential pressure compared to the pressure of the liquid
near the substrate surface, is at least 1 atmosphere (atm, 101325
Pa) or more, preferably 3 atmospheres or more, and more preferably
5 atmospheres or more, thereby enabling effective removal of the
particles 3 attached to the substrate 1. An upper limit of the
differential pressure is 20 atmospheres or less, preferably 15
atmospheres, and more preferably 12 atmospheres.
[0117] In a mixing unit, the bubbles 30 or the cleaning particles
40 are mixed into the cleaning liquid 20. As an example of the
mixing unit, FIG. 1 shows bubbles generation nozzle 36. In the
apparatus for cleaning substrate 10 shown in FIG. 1, a gas
introduction tube 34 is inserted to the cleaning-liquid-tube 24 to
introduce a gas 38 into the cleaning liquid 20 from the bubble
generation nozzle 36 at a tip end of the gas introduction tube 34
located in the cleaning-liquid-tube 24, thereby obtaining a
structure being enabled to mix the bubbles 30 into the cleaning
liquid 20. By pressurizing the gas 38 at a pressure higher than
that of the cleaning liquid 20, it is possible to introduce the gas
38 into the cleaning liquid 20 for generation of the bubbles 30.
The mixing unit can also have a structure of mixing the bubbles 30
into the cleaning liquid 20 before pressurization. As the gas 38,
air, nitrogen, and/or an inert gas can be used. From the view of
the costs, as the gas 38, it is preferred to use air from which
particles are removed with a dust filter.
[0118] As another example of the mixing unit, the apparatus for
cleaning substrate 10 shown in FIG. 2 has a structure of a
cleaning-particle-mixing-unit 42 to allow the cleaning particles 40
to be mixed into the cleaning liquid 20. The cleaning liquid 20
having the cleaning particles 40 mixed thereto in the
cleaning-particle-mixing-unit 42 is pressurized by the
cleaning-liquid-pressurizing-device 22, and supplied to the
cleaning-liquid-tube 24. The mixing unit can also have a structure
of mixing the cleaning particles 40 into the cleaning liquid 20
after pressurization.
[0119] During cleaning of the substrate 1, while rotating the
substrate 1 at a predetermined rotation speed, a position of the
injection nozzle 26 can be configured to move, for example, by
swinging between the center and the edge surface of the substrate
1. It is also possible to have a structure with a fixed injection
nozzle 26 and the structure that allows the substrate rotated
and/or moved, and also it is also possible to have a structure with
a fixed substrate 1 and the structure with the injection nozzle 26
fixed so that the cleaning liquid 20 can be injected to the entire
substrate 1.
[0120] As the cleaning liquid 20 in this case, it is preferred to
use pure water, such as ultrapure water, pure water, and deionized
water, for example. A conventional cleaning fluid containing an
acidic substance or an alkaline substance, such as a sulfuric acid
peroxide mixture and an ammonia peroxide mixture, can also be used.
However, in a case of using an acidic or alkaline cleaning fluid,
the smoothness and the flatness of the surface of the glass
substrate 1 obtained by polishing are sometimes degraded, so that
it is preferred to use pure water. As the cleaning liquid 20, it is
also possible to use hydrogen gas dissolved water, O.sub.2 gas
dissolved water, O.sub.3 gas dissolved water, noble gas dissolved
water, N.sub.2 gas dissolved water, or the like.
[0121] In a case of using the apparatus for cleaning substrate 10,
the rotation speed of the substrate 1 and the moving speed of the
injection nozzle 26 while cleaning are preferably set at
predetermined values so as to uniformly clean the entire substrate
1. The injection nozzle 26 in the apparatus for cleaning substrate
10 can use any shape of the tip end thereof, such as a circular
shape, a rectangular shape like a slit shape, for example. In order
to certainly inject the cleaning liquid 20 in a pressurized state
from the injection nozzle 26, the injection nozzle 26 preferably
has a shape of an opening with a shape of a slit or a pinhole.
[0122] As the above description, according to the method of
manufacturing the mask blank substrate of the present invention,
the cleaning liquid 20 containing the bubbles 30 or the cleaning
particles 40 is pressurized by the
cleaning-liquid-pressurizing-device 22, so that the particles 3 on
the main surface 71 of the substrate can be removed certainly by
the cleaning liquid 20 and the bubbles 30 injected from the
injection nozzle 26.
[0123] The method of cleaning a substrate of the present invention
described above can be used preferably as a cleaning step of a
method of manufacturing a mask blank substrate. The method of
cleaning a substrate of the present invention is also applicable to
cleaning step in a method of manufacturing a mask blank and a
method of manufacturing a reflective mask blank.
[0124] The method of manufacturing the mask blank substrate of the
present invention and the method of manufacturing the mask blank of
the present invention explained above are particularly preferred
for manufacture of a mask blank substrate and a mask blank used to
fabricate a transfer mask used for an exposure apparatus with
exposure light having a short wavelength of 200 nm or less as an
exposure light source requiring a miniaturized transfer pattern. As
a demand for pattern miniaturization is becoming more and more, a
demand for the surface defect of a mask blank substrate and a mask
blank has also become extremely severe. For example, in a case of
fabricating, for example, a phase shift mask using a mask blank
with concave defects due to generation of the latent defects
described above or convex defects due to attachment of foreign
substances or the like on a surface of a glass substrate, a change
in the phase angle and a decrease in the transmissivity due to the
concave defects and the convex defects occur in a transmitted light
of the exposure light. The change in the phase angle and the
decrease in the transmissivity cause deterioration in the
positional accuracy and the contrast of the transferred pattern.
Particularly in a case of using light having a short wavelength,
such as an ArF excimer laser having a wavelength of approximately
193 nm as the exposure light, the change in the phase angle becomes
very sensitive to the minute concave defects on the mask surface,
so that the influence of the transfer image increases. Accordingly,
the changes in the phase angle and the transmissivity derived from
the minute concave defects are important problems that are not
negligible at all.
[0125] In a case of binary mask as well, when light having a short
wavelength, such as an ArF excimer laser having a wavelength of
approximately 193 nm, is used as exposure light, it becomes an
important problems to have a minute surface defect on the substrate
surface. This is because, when there is a minute surface defect on
the substrate surface, the influence to the transmissivity
increases. According to the present invention, it is possible to
prevent generation of a minute surface defect, such as a convex
defect, due to attachment of particles, such as foreign substances,
so that it is preferred for fabrication of a transfer mask used for
an exposure apparatus with exposure light having a short wavelength
of 200 nm or less requiring a miniaturized transfer pattern as an
exposure light source.
[0126] A multitone mask used for manufacture of flat panel displays
and the like is configured to have regions of at least three
different transmissivity coexisted on a glass substrate that are
light shielding area to shield exposure light, a
light-semi-transmitting area to transmit exposure light at a
predetermined transmissivity, and a transparent area to transmit
exposure light at a high transmissivity. A flat panel display
herein may also be referred to as an FPD. In recent years, a
multitone mask provided with two types or more of a
light-semi-transmitting area having different transmissivity is
also used. Therefore, control of the transmissivity for exposure
light is very important, and the presence of latent defects
described above on a surface of a glass substrate, generation of
concave defects due to the latent defects, and the presence of
convex defects due to attachment of foreign substances are the
problems to be avoided. According to the present invention,
generation of a minute surface defect, such as a convex defect due
to attachment of particles like foreign substances, can be
prevented, so that it is preferred to fabricate a multitone
mask.
[0127] The cleaning method of the present invention is preferred
for a mask blank substrate used to manufacture the following mask
blanks, for example.
Substrate a: Binary Mask Blank having Thin Film being Light
Shielding Film Made of Material Containing Transition Metal
[0128] This binary mask blank has a configuration comprising light
shielding film on a transparent substrate, and this light shielding
film is made of a material containing an elemental substance of
transition metal, such as chromium, tantalum, ruthenium, tungsten,
titanium, hafnium, molybdenum, nickel, vanadium, zirconium,
niobium, palladium, and/or rhodium or a compound thereof. For
example, a light shielding film may be composed of chromium or a
chromium compound having one or more elements selected from the
elements, such as oxygen, nitrogen, and carbon, added to chromium.
A light shielding film may also be composed of, for example, a
tantalum compound having one type or more elements selected from
the elements, such as oxygen, nitrogen, and boron, added to
tantalum.
[0129] This binary mask blank comprises those having a light
shielding film with two layer structures of light shielding layer
and a surface antireflection layer, those having a three layer
structure with a back surface antireflection layer between the
light shielding layer and the substrate further in addition to the
two layer structure, and the like.
[0130] The light shielding film can be a composition gradient film
having composition varying continuously or gradually across the
film thickness.
Substrate b: Phase Shift Binary Mask Blank having Thin Film above
being Light-Semi-Transmitting Film Made of Material Containing
Transition Metal and Silicon Compound, that is, Material Containing
Transition Metal Silicide Compound, Particularly Molybdenum
Silicide Compound
[0131] As this phase shift mask blank, a halftone phase shift mask
has a form comprising a light-semi-transmitting film on a
transparent substrate, such as a glass substrate, and a shifter
area is produced by patterning the light-semi-transmitting film.
This phase shift mask may have a configuration comprising a
light-semi-transmitting film on a transparent substrate and light
shielding film that is light shielding band on the
light-semi-transmitting film, in order to prevent a pattern failure
in a transferred substrate by a light-semi-transmitting film
pattern formed in a transfer region based on light transmitted
through the light-semi-transmitting film. Other than a halftone
phase shift mask blank, it may also comprise mask blanks of a
Levenson phase shift mask, which is a substrate embedded type with
a shifter area embedded in a transparent substrate by etching or
the like, and an enhancer type phase shift mask.
[0132] The light-semi-transmitting film of the halftone phase shift
mask blank transmits light with an intensity substantially not
contributing to exposure, for example, light with an intensity from
1% to 30% relative to light of the exposure wavelength and has a
predetermined phase difference, for example, a phase difference of
180 degrees. It may be possible to have an inverse relationship
between a phase of light transmitted through a
light-semi-transmitting area made by patterning the
light-semi-transmitting film and a phase of light, with intensity
substantially contributing to exposure, transmitted through a
transparent area without the light-semi-transmitting film formed
therein. The light transmitted through the light-semi-transmitting
area and the light transmitted through the transparent area are
diffracted to the other regions each other due to the diffraction
of light. Since the respective phases of the light transmitted
through the light-semi-transmitting area and the light transmitted
through the transparent area are in the inverse relationship, both
lights cancel each other. As the result, light intensity at a
boundary between the light-semi-transmitting area and the
transparent area can be almost zero, and a contrast of the light at
the boundary, which is resolution, is improvement.
[0133] The material for this light-semi-transmitting film may
comprise a material containing, for example, a compound of
transition metal and silicon, that is, a transition metal silicide
compound. Specifically, the material for the
light-semi-transmitting film may comprise a material having main
components of the transition metal and silicon with oxygen and/or
nitrogen. The transition metal can be selected from molybdenum,
tantalum, tungsten, titanium, hafnium, nickel, vanadium, zirconium,
niobium, palladium, ruthenium, rhodium, chromium, and an alloy
thereof.
[0134] Since the material for the light-semi-transmitting film
contains transition metal and silicon, in a case of a configuration
comprising light shielding film on the light-semi-transmitting
film, the material for the light shielding film is preferably a
material having etching selectivity to the light-semi-transmitting
film, that is, a material having etching resistance. The material
for the light shielding film having etching resistance is
particularly preferably chromium or a chromium compound having
elements, such as oxygen, nitrogen, and/or carbon, added to
chromium.
[0135] The Levenson phase shift mask is produced using a mask blank
having a similar configuration to a binary mask blank. Accordingly,
the structure of the thin film for pattern formation of the
Levenson phase shift mask is similar to that of the light shielding
film of the binary mask blank. The light-semi-transmitting film of
the mask blank for an enhancer type phase shift mask transmits
light with intensity that does not contribute to exposure
substantially, for example, light with intensity from 1% to 30%
relative to light of the exposure wavelength, which is the same as
the light-semi-transmitting film of the halftone phase shift mask
blank. However, the light-semi-transmitting film of the mask blank
for the enhancer type phase shift mask is the film that has a small
phase difference generated in the transmitting exposure light, for
example, having a phase difference of 30 degrees or less,
preferably a phase difference of 0 degrees, which is different from
the light-semi-transmitting film of the halftone phase shift mask
blank. Although the material for the light-semi-transmitting film
of the mask blank for the enhancer type phase shift mask contains
the elements similar to the light-semi-transmitting film of the
halftone phase shift mask blank, the composition ratio of each
element and the film thickness are adjusted to be a predetermined
transmissivity and a predetermined small phase difference relative
to the exposure light.
Substrate c: Binary Mask Blank having Thin Film being Light
Shielding Film Made of Transition Metal, Material Containing
Compound of Transition Metal and Silicon, particularly, Material
Containing Transition Metal Silicide, more particularly Molybdenum
Silicide
[0136] This light shielding film may comprise a material containing
a compound of transition metal and silicon. Specifically, the
material for the light shielding film may comprise a material
having main components of the transition metal and silicon with
oxygen and/or nitrogen. The material for the light shielding film
may also comprise a material having main components of transition
metal with oxygen, nitrogen, and/or boron. The usable transition
metals may comprise molybdenum, tantalum, tungsten, titanium,
hafnium, nickel, vanadium, zirconium, niobium, palladium,
ruthenium, rhodium, chromium, and the like.
[0137] Particularly in a case of forming the light shielding film
with a molybdenum silicide compound, the light shielding film may
have a two layer structure of light shielding layer of MoSi or the
like and a surface antireflection layer of MoSiON or the like and
may also have a three layer structure of a back surface
antireflection layer of MoSiON or the like between the light
shielding layer and the substrate further in addition to the two
layer structure.
[0138] The light shielding film can be a composition gradient film
having composition varying continuously or gradually across the
film thickness.
[0139] In order to make a fine pattern with thinner film thickness
of a resist film, it can also be a configuration having an etching
mask film on the light shielding film. This etching mask film
preferably has etching selectivity to the etching of the light
shielding film containing transition metal silicide, that is, a
material having etching resistance. The material for the light
shielding film having etching resistance is preferably a material
made particularly of chromium or a chromium compound having
elements, such as oxygen, nitrogen, and/or carbon, added to
chromium. At this time, if the etching mask film has an
antireflection function, it is possible to fabricate a transfer
mask with remaining the etching mask film on the light shielding
film.
Substrate d: Multitone Mask Blank having Thin Film in Lamination
Structure of One or More Light-Semi-Transmitting Film and Light
Shielding Film
[0140] The material for the light-semi-transmitting film of the
multitone mask blank may comprise, other than the elements similar
to the light-semi-transmitting film of the halftone phase shift
mask blank, an elemental substance of metal, such as chromium,
tantalum, titanium, and aluminum, or an alloy thereof, and
materials containing these compounds. The composition ratio and the
film thickness of each element are adjusted to be a predetermined
transmissivity relative to the exposure light. The material similar
to the light shielding film of the binary mask blank can also be
used for the material for the light shielding film of the multitone
mask blank. The composition and the film thickness of the light
shielding film material can be adjusted in order to obtain
predetermined light shielding performance (a predetermined optical
density) of the lamination structure of the light shielding film
material and the light-semi-transmitting film.
[0141] In Substrates a, b, c, and d above, between the transparent
substrate and the light shielding film or between the
light-semi-transmitting film and the light shielding film, an
etching stopper film having etching resistance to the light
shielding film and/or the light-semi-transmitting film can be
formed. The material for the etching stopper film can be a material
allowing the etching mask film to be stripped at the same time when
etching the etching stopper film.
[0142] Further, the cleaning method of the present invention can be
used particularly preferably for cleaning of a mask blank substrate
used to manufacture a reflective mask blank, as follows.
Substrate e: Reflective Mask Blank Provided with Absorber Film on
Multilayer Reflective Film Made of Alternately Laminating High
Refractive Index Layer and Low Refractive Index Layer
[0143] The reflective mask is a mask used for EUV lithography. The
reflective mask has a structure of forming a multilayer reflective
film to reflect exposure light on a substrate and forming an
absorber film to absorb exposure light with a pattern shape on a
multilayer reflective film. Light, for example, EUV light,
introduced to a reflective mask mounted to an exposure apparatus,
which is a pattern transfer apparatus, is absorbed in an area with
the absorber film and is reflected in an area without the absorber
film by the multilayer reflective film. The light image reflected
by the multilayer reflective film is transferred onto the
semiconductor substrate through an optical system.
[0144] The multilayer reflective film is formed by alternately
laminating a high refractive index layer and a low refractive index
layer. Examples of the multilayer reflective film may comprise an
Mo/Si cyclic lamination film made of alternately laminating Mo
films and Si films in approximately 40 cycles, an Ru/Si cyclic
multilayer film, an Mo/Be cyclic multilayer film, an Mo compound/Si
compound cyclic multilayer film, an Si/Nb cyclic multilayer film,
an Si/Mo/Ru cyclic multilayer film, an Si/Mo/Ru/Mo cyclic
multilayer film, an Si/Ru/Mo/Ru cyclic multilayer film, and the
like. It is possible to select a predetermined material, depending
on the exposure wavelength.
[0145] As the absorber film of the reflective mask, a material
having a function of absorbing, for example, EUV light as exposure
light can be used preferably. As the absorber film of the
reflective mask, a elemental substance of, for example, tantalum
expressed by a chemical symbol of Ta or a material containing Ta as
a main component can be used preferably. Such an absorber film is
preferably in a crystal state of amorphous or microcrystalline
structure, from the view of the smoothness and the flatness.
[0146] The material containing Ta as a main component may comprise
a material containing Ta and B, a material containing Ta and N, a
material containing Ta and B and further at least either O or N, a
material containing Ta and Si, a material containing Ta, Si, and N,
a material containing Ta and Ge, a material containing Ta, Ge, and
N, a material containing Ta and Hf, a material containing Ta, Hf,
and N, a material containing Ta and Zr, a material containing Ta,
Zr, and N, and the like. By adding B, Si, and/or Ge to Ta, it is
possible to easily obtain an amorphous material to enable
improvement of the smoothness. Since oxidation resistance improves
by adding N and/or O to Ta, an effect of enabling improvement of
the temporal stability can be obtained.
[0147] In a case of the EUV reflective mask blank, it is required
to satisfy conditions to a surface defect at a very high level. The
method of cleaning a substrate of the present invention can be used
particularly preferably to clean a substrate used for an EUV
reflective mask blank.
EXAMPLES
[0148] Embodiments of the present invention are described in
further detail with Examples.
Example 1
[0149] For the substrate, a synthetic quartz glass substrate in a
size of 152.4 mm.times.152.4 mm having a thickness of 6.35 mm was
used. Edge surfaces of this synthetic quartz glass substrate was
processed by chamfering and grinding, and further was treated by
rough polishing and precision polishing with a polishing solution
containing cerium oxide abrasive particles. The glass substrate
finished with these processes, treatments and polishing, was set in
a carrier of a double side polishing machine, and it is polished
with super precision polishing process with the conditions as
follows.
[0150] Polishing Pad: Soft polisher of suede type
[0151] Polishing Solution: Abrasive particles of colloidal silica
having a particle size of 100 nm and water
[0152] Processing Pressure: From 50 to 100 g/cm.sup.2
[0153] Processing Time: 60 minutes
[0154] After finishing the super precision polishing, the glass
substrate was immersed in hydrofluoric acid to carry out cleaning
for removal of the abrasive particles of the colloidal silica.
Next, the main surfaces and the edge surfaces of the glass
substrate were subjected to scrub cleaning and subsequently were
subjected to spin cleaning with pure water and spin drying. After
spin drying, the main surfaces of the glass substrate was subjected
to defect inspection for convex defects and concave defects in a
size equivalent to 60 nm or more using a defect inspection
apparatus with sensitivity of 60 nm by a laser interference
confocal optical system. As the defect inspection apparatus, M6640
manufactured by Lasertec Corporation was used. Next, out of glass
substrates subjected to the defect inspection, ten glass substrates
with no concave defect detected and with less than ten convex
defects detected, equivalent to 60 nm, were selected. Using these
selected glass substrates, cleaning capabilities in the cleaning
conditions in each Example were evaluated, as follows.
[0155] On a main surface of the selected glass substrate, PSL
particles having a particle size of 60 nm were scattered as dummy
foreign substances. Next, using a defect inspection apparatus of 60
nm sensitivity, M6640 manufactured by Lasertec Corporation, defect
inspection was carried out for convex defects and concave defects
in a size equivalent to 60 nm or more. As the result, although no
concave defect was detected, 3430 convex defects in a size
equivalent to 60 nm or more were detected.
[0156] Subsequently, the substrate was cleaned using the apparatus
for cleaning substrate shown in FIG. 1. As the cleaning liquid,
pure water containing bubbles was used. The flow rate of the
cleaning liquid containing bubbles injected from the injection
nozzle to the surface of the substrate was adjusted to 1.5
liters/minute. The rotation speed of the substrate and the moving
speed of the cleaning nozzle during the cleaning were set at
predetermined values. Other experimental conditions were as
follows.
[0157] Pressure of Cleaning Liquid: 5 atmospheres
[0158] Type of Gas for Bubble Generation: Air
[0159] Flow Rate of Gas Introduced into Cleaning Liquid: 1.0
liter/minute
[0160] Shape of Injection nozzle: Pinhole like circular shape
having diameter of 1 mm
[0161] Cleaning of the substrate was carried out for five minutes
in the above conditions. The main surface of the glass substrate
after cleaning was subjected to defect inspection for convex
defects and concave defects in a size equivalent to 60 nm or more
using the defect inspection apparatus of 60 nm sensitivity, M6640
manufactured by Lasertec Corporation. As the result, although no
concave defect was detected, 69 convex defects in a size equivalent
to 60 nm or more were detected.
[0162] In a similar manner, total ten glass substrates were
subjected to scattering of dummy foreign substances, cleaning, and
defect inspection.
[0163] Regarding the ten glass substrates finished with the above
cleaning, the particle removal rate having a particle size
equivalent to 60 nm or more on the substrate surface after cleaning
was calculated based on the relational expression described above.
As the result, a high particle removal rate of 98.0% in average of
the ten glass substrates was obtained. Accordingly, it was found
that a high cleaning effect was obtained by the cleaning in Example
1.
[0164] The ten glass substrates finished with the above cleaning
were immersed in an alkaline chemical for 20 minutes and cleaned,
followed by the main surfaces of the glass substrates were
subjected to again defect inspection using the defect inspection
apparatus of 60 nm sensitivity, M6640 manufactured by Lasertec
Corporation. As the result, no concave defect was detected for any
of the ten substrates. Accordingly, it could be confirmed that no
latent defects was generated inside the glass substrates even when
the above cleaning of a substrate of the present invention was
carried out.
Example 2
[0165] Other than cleaning the substrates using pure water
containing cleaning particles as the cleaning liquid and using the
apparatus for cleaning substrate shown in FIG. 2, ten glass
substrates were subjected to scattering of dummy foreign
substances, cleaning, and defect inspection in a similar manner to
Example 1. The conditions in Example 2 other than the following
experimental conditions were similar to those in Example 1.
[0166] Pressure of Cleaning Liquid: 5 atmospheres
[0167] Type of Cleaning Particle: Latex particle having average
particle size of 60 nm
[0168] Flow Rate of Gas Introduced into Cleaning Liquid: 1.0
liter/minute
[0169] Flow Rate of Cleaning Particle Introduced into Cleaning
Liquid: 0.5 liters/minute
[0170] Shape of Injection nozzle: Pinhole like circular shape
having diameter of 1 mm
[0171] Cleaning of the substrate was carried out for five minutes
in the above conditions. The main surface of the glass substrate
after cleaning was subjected to defect inspection for convex
defects and concave defects in a size equivalent to 60 nm or more
using the defect inspection apparatus of 60 nm sensitivity, M6640
manufactured by Lasertec Corporation. Total ten glass substrates
were subjected to scattering of dummy foreign substances, cleaning,
and defect inspection.
[0172] Regarding the ten glass substrates finished with the above
cleaning, the particle removal rate having a particle size
equivalent to 60 nm or more on the substrate surface after cleaning
was calculated based on the relational expression described above.
As the result, a high particle removal rate of 98% in average of
the ten glass substrates was obtained. Accordingly, it was found
that a high cleaning effect was obtained by the cleaning in Example
2.
[0173] The ten glass substrates finished with the above cleaning
were immersed in an alkaline chemical for 20 minutes and cleaned,
followed by the main surfaces of the glass substrates were
subjected to again defect inspection using the defect inspection
apparatus of 60 nm sensitivity, M6640 manufactured by Lasertec
Corporation. As the result, no concave defect was detected for any
of the ten substrates. Accordingly, it could be confirmed that no
latent defects was generated inside the glass substrates even when
the above cleaning of a substrate of the present invention was
carried out.
Comparative Example 1
[0174] Other than carrying out cleaning with pure water only as the
cleaning liquid instead of cleaning with pure water containing
bubbles or cleaning particles for the cleaning of the substrate,
the cleaning capabilities were evaluated in a similar manner to
Examples 1 and 2.
[0175] The defect inspection of the main surface of the substrate
before and after cleaning was carried out in a similar manner to
Example 1, the particle removal rate having a particle size
equivalent to 60 nm or more on the substrate surface after cleaning
was calculated based on the relational expression described above.
As the result, the particle removal rate was a value of 87% in
average of the ten glass substrates and was lower than the particle
removal rate in Examples 1 and 2. Accordingly, it was found that a
high cleaning effect was obtained by Examples 1 and 2 using the
method of cleaning a substrate of the present invention.
* * * * *