U.S. patent application number 12/241931 was filed with the patent office on 2009-01-29 for container for housing a mask blank, method of housing a mask blank, and mask blank package.
This patent application is currently assigned to HOYA CORPORATION. Invention is credited to Akinori KURIKAWA.
Application Number | 20090029271 12/241931 |
Document ID | / |
Family ID | 33568734 |
Filed Date | 2009-01-29 |
United States Patent
Application |
20090029271 |
Kind Code |
A1 |
KURIKAWA; Akinori |
January 29, 2009 |
CONTAINER FOR HOUSING A MASK BLANK, METHOD OF HOUSING A MASK BLANK,
AND MASK BLANK PACKAGE
Abstract
A container is adapted to receive a mask blank having a resist
film and includes a container body having an upper opening and a
cap put on the container body. The container body has an opening
edge provided with an annular elastic member made of polyolefin
elastomer or the like and extending throughout entire
circumference. When the cap is put on the container body, the
elastic member is interposed at a joint portion between the cap and
the container body to hermetically seal the container.
Inventors: |
KURIKAWA; Akinori; (Tokyo,
JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
HOYA CORPORATION
|
Family ID: |
33568734 |
Appl. No.: |
12/241931 |
Filed: |
September 30, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10886039 |
Jul 8, 2004 |
7463338 |
|
|
12241931 |
|
|
|
|
Current U.S.
Class: |
430/5 ; 206/454;
206/455; 414/800; 428/34.1; 428/35.7 |
Current CPC
Class: |
H01L 21/67353 20130101;
G03F 1/66 20130101; Y10T 428/1352 20150115; H01L 21/67376 20130101;
H01L 21/67359 20130101; Y10T 428/13 20150115 |
Class at
Publication: |
430/5 ; 428/34.1;
428/35.7; 414/800 |
International
Class: |
G03F 1/00 20060101
G03F001/00; B32B 1/02 20060101 B32B001/02; B65G 69/00 20060101
B65G069/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 8, 2003 |
JP |
271924/2003 |
Jul 25, 2003 |
JP |
279961/2003 |
Aug 12, 2003 |
JP |
292317/2003 |
Aug 25, 2003 |
JP |
299711/2003 |
Claims
1. A container for housing a mask blank having a chemically
amplified resist film in its interior, comprising: a container body
having an upper opening; a cap member to be put on the container
body; and an elastic member which is placed at a joint portion
between the container body and the cap member and which
hermetically seals an interior of the container to an extent that
the chemically amplified resist film is not contaminated by an acid
substance when the cap member is put on the container body.
2. A container according to claim 1, wherein the joint portion is
fixed by a sliding locking member for clamping the joint
portion.
3. A container according to claim 1, wherein the elastic member is
made of a material which hardly releases a chemical gas to the
extent that the chemically amplified resist film is not
contaminated by the acid substance.
4. A container according to claim 3, wherein the material is
polyolefin elastomer or polyester elastomer.
5. A method of housing a mask blank, comprising: preparing the
container according to claim 1; manufacturing the mask blank having
the chemically amplified resist film; and housing the manufactured
mask blank in the container.
6. A method according to claim 5, wherein the mask blank is housed
in the container under an atmosphere in which the acid substance is
removed to the extent that the chemically amplified resist film is
not contaminated by the acid substance.
7. A method according to claim 6, wherein the acid substance in the
atmosphere contains chlorine ions, sulfate ions or nitrate ions,
wherein a content of the chlorine ions is 0.05 .mu.g or less per 1
m.sup.3 of the atmosphere, a content of the sulfate ions is 0.1
.mu.g or less per 1 m.sup.3 of the atmosphere, and a content of the
nitrate ions is 0.7 .mu.g or less per 1 m.sup.3 of the
atmosphere.
8. A mask blank package, which is obtained by housing a mask blank
by a method according to claim 5.
9. A container for housing a mask blank having a chemically
amplified resist film in its interior, comprising: a container body
having an upper opening; a cap member to be put on the container
body; and a mechanism for inhibiting entry of an acid substance in
ambient air into the container to an extent that the chemically
amplified resist film is not contaminated by the acid substance
when the cap member is put on the container body.
10. A container according to claim 9, wherein the mechanism
comprising: a vent hole placed on the container to allow
communication between the ambient air and internal air; and a
filtering member placed in the vent hole to remove the acid
substance in the ambient air.
11. A container according to claim 10, wherein the filtering member
is a chemical filter for adsorbing the acid substance.
12. A method of housing a mask blank, comprising: preparing the
container according to claim 9; manufacturing the mask blank having
the chemically amplified resist film; and housing the manufactured
mask blank in the container.
13. A method according to claim 12, wherein the mask blank is
housed in the container under an atmosphere in which the acid
substance is removed to the extent that the chemically amplified
resist film is not contaminated by the acid substance.
14. A method according to claim 13, wherein the acid substance in
the atmosphere contains chlorine ions, sulfate ions or nitrate
ions, wherein a content of the chlorine ions is 0.05 .mu.g or less
per 1 m.sup.3 of the atmosphere, a content of the sulfate ions is
0.1 .mu.g or less per 1 m.sup.3 of the atmosphere, and a content of
the nitrate ions is 0.7 .mu.g or less per 1 m.sup.3 of the
atmosphere.
15. A mask blank package, which is obtained by housing a mask blank
by a method according to claim 12.
16. A method of transporting a mask blank package according to
claim 15, wherein the mask blank package is transported by the use
of traffic means.
17. A method of housing a mask blank having a chemically amplified
resist film in a container, wherein the mask blank is housed in the
container together with an atmosphere from which an acidic
substance is removed.
18. A method of housing a mask blank having a chemically amplified
resist film in a container, wherein the mask blank is housed in the
container under an atmosphere from which an acidic substance is
removed.
19. A mask blank package, wherein a mask blank having a chemically
amplified resist film is housed in a container having an atmosphere
which does not contain an acidic substance.
Description
[0001] This is a divisional of application Ser. No. 10/886,039
filed Jul. 8, 2004. The entire disclosure(s) of the prior
application(s), application Ser. No. 10/886,039 is considered part
of the disclosure of the accompanying divisional application and is
hereby incorporated by reference.
[0002] This application claims priority to prior Japanese
applications JP 2003-271924, 2003-279961, 2003-292317, and
2003-299711, the disclosures of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0003] This invention relates to a container for housing a photo
mask for use in fabrication of an electronic device or a mask blank
for use in fabrication of the photo mask and to a method of housing
the photo mask or the mask blank.
[0004] This invention also relates to a method of housing a mask
blank with a resist film, which is for producing a photo mask for
use in manufacture of an electronic device.
[0005] This invention also relates to a method of treating a
housing member for housing a mask blank with a resist film, which
is for producing a photo mask for use in manufacture of an
electronic device.
[0006] Following rapid development of the IT (Information
Technology) industry, a recent electronic device, in particular, a
semiconductor device, a color filter or a TFT (Thin Film
Transistor) element for a LCD (Liquid Crystal Display) monitor, or
the like is required to have a finer structure. One of techniques
supporting fine process technology for such a finer structure is a
lithography technique using a photo mask called a transfer mask. In
the lithography technique, a silicon wafer with a resist film is
exposed through the transfer mask to an electromagnetic wave from
an exposure light source so that a fine pattern is formed on the
silicon wafer. Generally, the transfer mask is produced by
preparing a mask blank comprising a light transparent substrate and
a light shielding film formed thereon and forming an original
pattern on the mask blank by the use of the lithography technique.
If foreign matters such as particles are present on a surface of
the mask blank, this may result in occurrence of a defect of the
pattern formed on the silicon wafer. Therefore, the mask blank must
be stored in a clean condition so that no foreign matters are
adhered or attached to the surface of the mask blank.
[0007] For example, as a conventional container for housing,
storing, and carrying a mask blank, a mask carrying case is
disclosed in Japanese Patent Application Publication (JP-A) No.
2001-154341.
[0008] Specifically, the conventional container for housing and
storing a mask blank comprises an inner case called a carrier, an
outer case (container body), and a cap. Several to several tens of
mask blanks are held in the inner case in parallel to one another.
The inner case with the mask blanks held therein is received in the
outer case. Then, the cap is put on the outer case. In this manner,
the mask blanks are housed in the container. An adhesive tape is
attached to a joint portion between the outer case and the cap to
hermetically seal the container and to prevent entry of ambient air
and foreign matters. In most cases, the container is made of a
resin material.
[0009] Following recent improvement in performance of the
electronic device, the original pattern formed on the transfer mask
is also required to be finer. In order to form such a finer
pattern, the mask blank must have an extremely high cleanliness.
Therefore, it is necessary to maintain as high cleanliness as
possible, in particular, during storage of the mask blank by
minimizing adhesion of foreign matters to the mask blank. Among
others, in case of a mask blank having a resist film formed on a
surface thereof, the foreign matters once adhered to the surface
are difficult to be removed. Further, cleaning is impossible at
this stage. Therefore, patterning is carried out with the foreign
matters adhered to the surface. This results in occurrence of a
pattern defect.
[0010] In the meanwhile, attention is recently directed to a
chemically amplified resist as a resist for a photo mask. For
example, the chemically amplified resist is described in Japanese
Patent Application Publication (JP-A) No. 2000-66380. The
chemically amplified resist is superior in characteristics, such as
sensitivity and contrast, than a photo resist which has been used
so far and is therefore advantageous in forming a finer pattern.
However, it is pointed out that the chemically amplified resist is
susceptible to an influence of a contaminant of a chemical
component because of its reaction mechanism. Specifically, in
presence of a contaminant of a certain chemical component, a
function of a substance serving as a catalyst for chemical
amplification may be suppressed or inhibited (for example,
deactivated) so that a desired performance can not be obtained.
[0011] The chemically amplified resist contains either a
high-molecular-weight compound having a resist function (positive
type) or a low-molecular-weight compound which produces a
high-molecular-weight compound by a cross-linking reaction or the
like (negative type), and a catalytic substance. By irradiating the
chemically amplified resist with energy radiation such as electron
wave or electromagnetic wave, the catalytic substance contained
therein is exposed to produce an acidic catalytic substance in the
resist. The acidic catalytic substance has a catalytic function for
a chemical reaction (chemical amplification) of making the
high-molecular-weight compound soluble to a liquid developer or
producing a high-molecular-weight compound and making the
high-molecular-weight compound insoluble to the liquid developer.
However, it is pointed out that the chemically amplified resist is
susceptible to an influence of a contaminant of a basic chemical
substance because of its reaction mechanism. Specifically, in
presence of a contaminant of a certain basic chemical substance,
for example, ammonia or amine, production of the acidic catalytic
substance serving as a catalyst for chemical amplification may be
inhibited or a function of the acidic catalytic substance produced
as mentioned above may be suppressed or inhibited (for example,
deactivated) so that a desired performance can not be obtained.
[0012] In view of the above, in case of the mask blank with a
chemically amplified resist film formed thereon, it is necessary
not only to eliminate foreign matters such as particles but also to
eliminate an influence of a contaminant of a chemical substance.
Therefore, the mask blank with a chemically amplified resist film
must be stored in an especially clean atmosphere.
[0013] In the conventional container for a mask blank, the joint
portion between the outer case and the cap is hermetically sealed
by the adhesive tape. However, this requires double efforts of
adhering the tape upon housing and packaging the mask blank and
removing the tape upon opening the container. In addition, a sealed
state is incomplete or insufficient. Specifically, the adhesive
tape generally used has some breathability. Depending upon
temperature variation of the atmosphere in which the container is
stored, internal air within the container may be expanded or
contracted. In this event, airflow between the ambient air and the
internal air occurs through the joint portion to which the tape is
adhered. Sometimes, pressure of the atmosphere may be varied, for
example, in case where the mask blank is transported on board an
aircraft. In case of transportation on board the airplane,
variation in pressure is considerably large. In this case also,
airflow occurs between the ambient air and the internal air.
Therefore, even if the mask blank is housed and packaged into the
container in a clean atmosphere such as a clean room, the ambient
air may enter into the container with lapse of time depending upon
a storage atmosphere after packaging. In this event, the interior
of the container may be contaminated by a certain component
contained in the ambient air.
[0014] Further, even if the container is made of a material, such
as plastic, which hardly releases any chemical component or the
like, a chemical component used in a base member of the adhesive
tape or an adhesive agent may enter into the container with lapse
of time to cause contamination. In particular, upon occurrence of
variation in atmosphere, such as temperature change or pressure
change mentioned above, contamination by the chemical component
released from the tape may be accelerated.
[0015] In particular, in case of the mask blank with the chemically
amplified resist film mentioned above, contamination by the
chemical component or the like causes a crucial defect and must be
completely avoided.
[0016] At a glance, it seems possible, by housing and packaging the
mask blank into the container within the clean room or the like and
sealing the joint portion between the outer case and the cap by the
adhesive tape, to prevent entry of the ambient air and store the
mask blank in a clean atmosphere. Actually, however, it is
difficult to avoid contamination by the entry of the ambient air or
contamination by the chemical component of the adhesive tape.
[0017] According to the study by the present inventor, it has been
found out that, even if contamination by the basic chemical
substance is avoided, a stable resist function is not always
obtained and a desired resist pattern is not always formed.
Specifically, it has been found out that, even if a factor causing
the basic substance such as amine to be generated during a
manufacturing process of the mask blank having the chemically
amplified resist film is thoroughly investigated and eliminated
and, further, close attention is paid to an environment of housing
and packaging the mask blank, there still arises a problem of
fluctuation in accuracy of the resist pattern formed on the mask
blank.
[0018] In order to eliminate the influence of the contaminant of
the basic chemical substance, the mask blank with the chemically
amplified resist film may be housed and packaged in an atmosphere
cleaned by the use of a chemical filter. Even in this event, the
mask blank housed in the container may be contaminated by a basic
substance released as an outgas from the container during
subsequent storage. In particular, depending upon the temperature
change or the pressure change of the ambient air during storage,
release of an outgas component may be accelerated. In this case, it
is proposed to use a material which releases a small amount of the
outgas component with lapse of time. In this approach, however,
contamination with lapse of time can not completely be eliminated
and the material of the container is restricted.
SUMMARY OF THE INVENTION
[0019] In order to remove the above-mentioned disadvantages, it is
an object of this invention to provide a container and a housing
method which are capable of storing a mask blank or the like while
keeping a clean atmosphere upon housing by inhibiting entry of
ambient air to avoid contamination by a chemical substance or the
like.
[0020] It is another object of this invention to provide a
container and a housing method which are suitable for a mask blank
provided with a chemically amplified resist film and required to be
stored in an especially clean atmosphere.
[0021] It is still another object of this invention to provide a
method of housing a mask blank, which is suitable for a mask blank
provided with a chemically amplified resist film and required to be
stored in an especially clean atmosphere and which is capable of
maintaining a stable resist function for forming a desired mask
pattern.
[0022] It is yet another object of this invention to provide a
method of treating a housing member for housing a mask blank, which
is suitable for a mask blank provided with a chemically amplified
resist film and required to be stored in an especially clean
atmosphere and which is capable of maintaining a stable resist
function for forming a desired mask pattern.
[0023] Generally, it is supposed that, by housing a mask blank into
a container in a clean atmosphere, such as a clean room, and
adhering an adhesive tape to a joint portion of the container to
seal the container, the mask blank can be stored while keeping the
clean atmosphere. However, as revealed by the study of the present
inventor, it is difficult in the known method to keep the clean
atmosphere in the container with the mask blank housed therein
after lapse of time. It is also found out that, particularly in
case of the mask blank having a chemically amplified resist film, a
desired fine pattern may not be formed during fabrication of a mask
and a stable resist function may not be obtained if the mask blank
is stored by the known housing method.
[0024] The present inventor earnestly and diligently studied in
order to remove the above-mentioned problem. As a result, it has
been found out that the entry of ambient air can be prevented and a
mask blank can be stored while keeping a clean atmosphere in the
interior of a container by providing an elastic member formed on at
least one of an opening edge of a main body of the container or a
lower edge of a cap member to extend throughout entire
circumference and interposed between the main body and the cap
member at a joint portion thereof. Thus, this invention has been
completed.
[0025] Further, as a result of earnest and diligent study of the
present inventor in order to remove the above-mentioned problem, it
has been found out that, even if the ambient air enters into the
container during storage, the mask blank can be stored while
keeping a clean atmosphere in the interior of the container, by
removing foreign matters such as a chemical substance contained in
the ambient air so that the foreign matters do not enter into the
container even if the ambient air enters. Thus, this invention has
been completed.
[0026] As described above, a contaminant for a chemically amplified
resist is generally believed to be a basic chemical substance such
as amine. According to the study by the present inventor, however,
it has been revealed that, even if the mask blank is stored in an
environment from which the basic chemical substance is eliminated,
a stable resist function may not be obtained and a desired fine
pattern may not be formed during manufacture of a mask.
[0027] As a result of earnest and diligent study by the present
inventor in order to remove the above-mentioned problem, it has
been unexpectedly found out that the mask blank having a chemically
amplified resist film may be contaminated not only by the basic
substance but also by adhesion of an acidic substance and formation
of a stable fine pattern is inhibited. It is also found out that
the acidic substance mainly affects the sensitivity of the
chemically amplified resist and has a function of excessively
enhancing a chemically amplifying effect. Based on a series of
findings described above, this invention has been completed.
[0028] The present inventor also found out that preliminary
treatment such as heating of the container is effective in order to
suppress the container releasing a chemical substance inhibiting
the chemically amplifying effect of the chemically amplified
resist.
[0029] Based on the findings mentioned above, this invention has
been completed.
[0030] Specifically, this invention has following structures.
[0031] Structure 1
[0032] A container which is for housing a mask blank in its
interior and which comprises a container body having an upper
opening and a cap member to be put on the container body, wherein
the container has an elastic member formed on at least one of an
opening edge of the container body and a lower edge of the cap
member to extend throughout entire circumference so that the
container is hermetically sealed when the cap member is put on the
container body.
[0033] Structure 2
[0034] A container which is for housing a mask blank in its
interior and which comprises a container body having an upper
opening and a cap member to be put on the container body, wherein
the container has an elastic member formed on at least one of an
opening edge of the container body and a lower edge of the cap
member to extend throughout entire circumference so that the
elastic member is interposed between the opening edge of the
container body and the lower edge of the cap member at a joint
portion therebetween when the cap member is put on the container
body.
[0035] Structure 3
[0036] A container according to structure 1 or 2, wherein the joint
portion is fixed and secured by a sliding locking member for
clamping the joint portion between the container body and the cap
member.
[0037] Structure 4
[0038] A method of housing a mask blank, wherein a mask blank
having a resist film is housed in a container according to
structure 1 or 2.
[0039] Structure 5
[0040] A method according to structure 4, wherein the resist film
is a chemically amplified resist film.
[0041] Structure 6
[0042] A mask blank package, which is obtained by housing a mask
blank by a method according to structure 4.
[0043] According to this invention, in a container which is for
housing a mask blank or the like and which comprises a container
body having an upper opening and a cap member to be put on the
container body, an elastic member is formed on at least one of an
opening edge of the container body and a lower edge of the cap
member to extend throughout entire circumference. With this
structure, the container is hermetically sealed when the cap member
is put on the container body. Therefore, it is possible to prevent
ambient air from entering the interior of the container during
storage and, consequently, to effectively prevent foreign matters
in the ambient air, such as particles or any chemical substance
contained in the ambient air, from entering the interior of the
container to contaminate the mask blank. In other words, it is
possible to store the mask blank for a long period of time while
keeping a clean atmosphere in the interior of the container. In
addition, it is possible to prevent contamination by a chemical
component in case where an adhesive tape is used.
[0044] According to this invention, the elastic member is
interposed between the opening edge of the container body and the
lower edge of the cap member at the joint portion therebetween when
the cap member is put on the container body. With this structure,
the container is hermetically sealed merely by putting the cap
member on the container. Therefore, the mask blank is easily housed
without requiring an additional work.
[0045] This invention is particularly suitable for housing and
storing a mask blank having a resist film which is required to be
housed and stored in an especially clean atmosphere, in particular,
a mask blank having a chemically amplified resist film required to
be absolutely prevented from contamination by a chemical substance
or the like.
[0046] This invention further has the following structures.
[0047] Structure 7
[0048] A container which is for housing a mask blank in its
interior and which at least comprises a container body having an
upper opening and a cap member to be put on the container body,
comprises a mechanism for inhibiting entry of foreign matters in
ambient air into the container.
[0049] Structure 8
[0050] A container according to structure 7, wherein the mechanism
for inhibiting entry of foreign matters in ambient air into the
container has a vent hole formed on the container to allow
communication between the ambient air and internal air, and a
filtering member formed in the vent hole to remove the foreign
matters in the ambient air.
[0051] Structure 9
[0052] A method of housing a mask blank, in which a mask blank
having a resist film is housed in a container according to
structure 7.
[0053] Structure 10
[0054] A method according to structure 9, wherein the resist film
is a chemically amplified resist.
[0055] Structure 11
[0056] A method according to structure 10, wherein the foreign
matters in the ambient air is a chemical substance inhibiting a
desired chemically amplifying effect in the chemically amplified
resist.
[0057] Structure 12
[0058] A mask blank package, which is obtained by housing a mask
blank by a method according to structure 9.
[0059] Structure 13
[0060] A method of transporting a mask blank package according to
structure 12, wherein the mask blank package is transported by the
use of traffic means.
[0061] According to this invention, in a container which is for
housing a mask blank and which comprises a container body having an
upper opening and a cap member to be put on the container body,
means for inhibiting entry of foreign matters in ambient air into
the container is provided. With this structure, it is possible to
prevent the ambient air from directly entering the interior of the
container and, consequently, to effectively prevent the foreign
matters in the ambient air, such as particles or any chemical
substance contained in the ambient air, from entering the interior
of the container to contaminate the mask blank. Thus, even if the
ambient air enters the interior of the container during storage, it
is possible by cleaning the ambient air to store the mask blank for
a long period of time while keeping a clean atmosphere in the
interior of the container. Therefore, it is possible to prevent the
mask blank from being contaminated by the foreign matters such as
the chemical substance during storage and, consequently, to obtain
a high-quality transfer mask by the use of the mask blank housed
and stored in the above-mentioned manner.
[0062] The means for inhibiting entry of foreign matters in ambient
air into the container may include a vent hole formed on the
container to allow communication between the ambient air and the
internal air and a filtering member formed in the vent hole to
remove the foreign matters in the ambient air. With this structure,
even if the ambient air enters, the foreign matters such as the
chemical substance contained in the ambient air are removed by the
filtering member so that the ambient air is cleaned. Therefore, it
is possible to prevent contamination due to entry of the foreign
matters or the chemical substance and to keep a clean atmosphere in
the interior of the container.
[0063] This invention is particularly suitable for housing and
storing a mask blank having a resist film which is required to be
housed and stored in a clean atmosphere, in particular, a mask
blank having a chemically amplified resist film required to be
absolutely prevented from contamination by a chemical substance or
the like.
[0064] According to this invention, when a mask blank package
obtained by housing a mask blank in a container is transported to a
remote place by the use of traffic means, the mask blank is not
contaminated even upon occurrence of temperature change or pressure
change of the ambient air. Therefore, it is possible to assure high
reliability in transportation of the mask blank to a remote
place.
[0065] This invention further has following structures.
[0066] Structure 14
[0067] A method of housing a mask blank having a chemically
amplified resist film in a container, wherein the mask blank is
housed in the container together with an atmosphere from which at
least an acidic substance is removed.
[0068] Structure 15
[0069] A method of housing a mask blank having a chemically
amplified resist film in a container, wherein the mask blank is
housed in the container under an atmosphere from which at least an
acidic substance is removed.
[0070] Structure 16
[0071] A method according to structure 14 or 15, wherein the
container has means for absorbing or adsorbing the acidic
substance.
[0072] Structure 17
[0073] A mask blank package, wherein a mask blank having a
chemically amplified resist film is housed in a container having an
atmosphere which does not contain at least an acidic substance.
[0074] Structure 18
[0075] A method of producing a mask blank with a resist film,
wherein a thin film for forming a mask pattern is deposited on a
substrate and a chemically amplified resist film is thereafter
formed on the thin film under an atmosphere from which at least an
acidic substance is removed.
[0076] Structure 19
[0077] A method of producing a mask blank with a resist film,
comprising a resist forming step of forming a chemically amplified
resist film on a mask blank obtained by depositing on a substrate a
thin film for forming a mask pattern, a post-treating step as an
optional step for treating the mask blank with the resist film, an
inspection step as an optional step for inspecting the mask blank
with the resist film, and a housing/packaging step of housing and
packaging the mask blank with the resist film in a container,
wherein at least one of the above-mentioned steps is carried out
under an atmosphere from which at least an acidic substance is
removed.
[0078] In this invention, the acidic substance to be removed may
be, particularly, an acidic substance as an acidic contaminant
adhered to the chemically amplified resist film to affect a
chemically amplifying function of the chemically amplified resist.
For example, the acidic substance may be a substance containing
chlorine ions, a substance containing sulfate ions, a substance
containing phosphate ions, or a substance containing nitrate ions.
Such acidic substance mainly affects the sensitivity of the
chemically amplified resist and has a function of excessively
enhancing the chemically amplifying effect so that a stable resist
function may not be obtained. As a result, formation of a stable
resist pattern may be inhibited so that a desired fine pattern is
not formed during manufacture of a mask.
[0079] The degree of removal of the acidic substance need not be
100%. It is sufficient to remove the acidic substance to the extent
that the chemically amplified resist film is not contaminated even
if the acidic substance is present in the atmosphere. As will
readily be understood, the degree of removal of the acidic
substance is preferably as high as possible in view of the quality
because the cleanliness is improved. However, pursuit of a higher
degree of removal may increase a production cost. Therefore, the
acidic substance may be removed from the atmosphere within a
profitable range and to the extent that no product defect is
caused. By way of example, specific numerical values are given
below. In case of the substance containing chlorine ions, the
content of chlorine ions is preferably 0.05 .mu.g or less per 1
m.sup.3 of the atmosphere. In case of the substance containing
sulfate ions, the content of sulfate ions is preferably 0.1 .mu.g
or less. In case of the substance containing nitrate ions, the
content of nitrate ions is preferably 0.7 .mu.g or less.
[0080] As a method of removing the acidic substance from the
atmosphere, use may be made of a filter (chemical filter) for
adsorbing a chemical substance. As the chemical filter for removing
the acidic substance, use is preferably made of a chemical filter
with an acid-neutralizing substance mixed therewith. As the
acid-neutralizing substance, carbonate is preferable. As the
carbonate, potassium carbonate is preferable. Preferably, an
activated carbon filter containing an adsorber such as activated
carbon is used as the above-mentioned chemical filter. Preferably,
a filter comprising the adsorber, such as activated carbon, mixed
with the acid-neutralizing substance is used as the above-mentioned
chemical filter.
[0081] In this invention, as described in structure 14, a mask
blank having a chemically amplified resist film is housed in a
container together with an atmosphere from which at least an acidic
substance is removed. Specifically, upon housing the mask blank
into the container, the atmosphere from which at least the acidic
substance is removed is supplied so that the mask blank is housed
and stored together with the atmosphere. It is therefore possible
to most preferably prevent the acidic contaminant from being
adhered to the mask blank in practical application.
[0082] In order to supply the atmosphere from which the acidic
substance is removed, use may be made of a method of supplying an
environment of a mask blank housing operation with an atmosphere
from which the acidic substance is removed by the use of the
above-mentioned chemical filter, a method of supplying the
container with the above-mentioned atmosphere to replace the
interior of the container, and a method of purging the container by
the above-mentioned atmosphere.
[0083] For example, as described in structure 15, a mask blank
having a chemically amplified resist film is preferably housed in a
container in an atmosphere from which at least an acidic substance
is removed. Generally, the operation of housing the mask blank is
carried out in a clean room. Therefore, it is easy to supply the
environment of the operation of housing the mask blank with the
atmosphere from which the acidic substance is removed by the use of
a chemical filter.
[0084] Preferably, a basic chemical substance, such as ammonia and
amine, which inhibits a desired chemically amplifying effect of the
chemically amplified resist is removed together with the acidic
substance. In order to remove the basic chemical substance, use may
be made of a method of using a chemical filter mixed with an
alkali-neutralizing substance, such as phosphoric acid. Preferably,
an activated carbon filter containing an adsorber such as activated
carbon is used as the above-mentioned chemical filter. Preferably,
a filter comprising the adsorber, such as activated carbon, mixed
with the alkali-neutralizing substance is used as the
above-mentioned chemical filter.
[0085] It is preferable to use an air filter in combination with
the chemical filter for removing the acidic substance or the basic
substance. Preferably, such an air filter may be a HEPA filter
(high efficiency particulate air filter) or an ULPA filter (ultra
low penetration particulate air filter). The HEPA filter is a
high-efficiency air filter and is generally made of a glass fiber
material. The ULPA filter is an ultra-high performance filter and
is generally made of a glass fiber or a fluorine-based resin
material. As an ability of the air filter, it is preferable to trap
particles having a diameter of 0.05 .mu.m or more. The air filter
such as the HEPA filter or the ULPA filter may be appropriately
selected taking into account cost effectiveness and the like.
[0086] This invention further has following structures.
[0087] Structure 20
[0088] A method of treating a housing member for housing a mask
blank having a chemically amplified resist film, wherein the method
includes a treatment for removing from the housing member a
chemical substance inhibiting a chemically amplifying effect of the
chemically amplified resist film.
[0089] Structure 21
[0090] A method according to structure 20, wherein the treatment
for removing the chemical substance inhibiting the chemically
amplifying effect of the chemically amplified resist film is a
treatment of heating the housing member.
[0091] Structure 22
[0092] A method according to structure 20, wherein a treatment of
bringing the housing member into contact with heated pure water is
carried out prior to the treatment for removing the chemical
substance.
[0093] Structure 23
[0094] A method according to structure 20, wherein the treatment
for removing the chemical substance is carried out upon a material
to be formed into the housing member and/or the housing member
after forming.
[0095] Structure 24
[0096] A method of producing a housing member for housing a mask
blank, the method including a method of treating a housing member
according to structure 20.
[0097] Structure 25
[0098] A mask blank package which is obtained by housing a mask
blank with a chemically amplified resist film in a member subjected
to a treatment for removing a chemical substance inhibiting a
chemically amplifying effect of the chemically amplified resist
film.
[0099] In this invention, the chemical substance to be removed from
the housing member for housing a mask blank is a chemical substance
adhered to the chemically amplified resist film and inhibiting the
chemically amplifying effect of the chemically amplified resist.
Presence of such chemical substance may suppress the desired
chemically amplifying effect or may excessively enhance the
chemically amplifying effect so that a stable resist function is
not obtained. As a result, formation of a desired stable resist
pattern is inhibited. Particularly, the chemical substance
affecting the chemically amplifying effect of the chemically
amplified resist may be an acidic substance as an acidic
contaminant. The acidic substance may be a substance containing
chlorine ions, a substance containing sulfate ions, a substance
containing phosphate ions, or a substance containing nitrate ions.
Such acidic substance mainly affects the sensitivity of the
chemically amplified resist and has a function of excessively
enhancing the chemically amplifying effect so that a stable resist
function may not be obtained. As a result, formation of a stable
resist pattern may be inhibited so that a desired fine pattern is
not formed during manufacture of a mask.
[0100] Further, it is preferable to treat the housing member so
that a basic substance, such as ammonia and amine, which inhibits a
desired chemically amplifying effect of the chemically amplified
resist is removed also.
[0101] In this invention, as the treatment for removing the
chemical substance inhibiting the chemically amplifying effect of
the chemically amplified resist, use may be made of heat treatment
or pressure-reducing treatment. Among others, the heat treatment is
preferable. By heat-treating the housing member, it is possible to
preliminarily release the chemical substance contained in the
housing member and possibly released as an outgas with lapse of
time. Therefore, if the mask blank is housed and packaged by the
use of the housing member subjected to the treatment according to
this invention, such as the heat treatment, to preliminarily
release the chemical substance contained in the housing member, the
outgas of the chemical substance is not released with lapse of
time. Thus, it is possible to prevent the mask blank having a
chemically amplified resist film from being contaminated by the
chemical substance and to maintain a stable resist function for
forming a desired mask pattern.
[0102] Upon carrying out the heat treatment, it is appropriate to
heat the housing member so that the atmosphere at least exceeds
room temperature. Generally, the mask blank is housed and stored in
a temperature region around the room temperature. Therefore, by the
above-mentioned heat treatment, it is possible to prevent the
outgas of the chemical substance from being released in the
temperature region in which the mask blank is housed and stored by
the use of the housing member subjected to the treatment according
to this invention. The heating temperature and the heating time may
appropriately be selected depending upon the characteristic of the
chemically amplified resist and taking into account the degree of
influence of the chemical substance upon the chemically amplifying
effect, which causes product defects. The heating temperature must
fall within a range such that the effect of this invention is
achieved and is practically between 40 and 90.degree. C.,
particularly between 40 and 80.degree. C. The heating time must
fall within a range such that the effect of this invention is
achieved and is practically between 5 minutes and 2 hours.
[0103] In this invention, the housing member for housing a mask
blank is preferably subjected to cleaning prior to the treatment
for removing the chemical substance. By preliminarily removing the
chemical substance adhered to a surface of the housing member by
cleaning, it is possible to reliably improve the effect of removing
the chemical substance by the treatment of this invention
subsequently carried out. In this case, pure water is preferably
used as a cleaning liquid. As the pure water, use is preferably
made of reverse osmotic membrane water (hereinafter abbreviated to
"RO water") or ultra filtration membrane water (hereinafter
abbreviated to "UF water"). If ion exchange is additionally carried
out to obtain ion exchanged water (may be called de-ionized water,
hereinafter abbreviated to "DI water"), the function of removing
the chemical substance from the housing member is further enhanced.
The RO water and the DI water have a complementary relationship
with respect to chemical substances as main objects to be removed.
Therefore, pure water subjected to RO treatment and then to DI
treatment (hereinafter abbreviated to "RO/DI water") achieves a
more desirable effect. By cleaning the above-mentioned member using
such pure water, it is possible to remove the chemical substance
and to prevent contamination by the cleaning liquid. Thus, cleaning
with the pure water is especially preferable in order to maintain
the performance of the chemically amplified resist film of the mask
blank to be housed.
[0104] In case where the cleaning is carried out by the use of the
pure water mentioned above, the cleaning is preferably carried out
by bringing the housing member into contact with heated pure water
because a more desirable effect is obtained. In this case, the
temperature of the pure water is selected within a temperature
region higher than the room temperature and lower than a boiling
point. Practically, the temperature region between 40 and
90.degree. C., particularly between 40 and 80.degree. C. may be
used.
[0105] In this invention, in order to improve the effect of
removing the chemical substance, the above-mentioned cleaning and
the treatment for removing the chemical substance according to this
invention may be repeated a plurality of number of times.
[0106] The treatment for removing the chemical substance according
to this invention is preferably carried out in a cleaned
environment. In particular, use is preferably made of an atmosphere
from which the acidic substance or the basic substance
contaminating the chemically amplified resist film is removed. This
is because the chemical substance contained in the atmosphere is
prevented from being adhered to the housing member during the
treatment of the housing member. In order to remove the acidic
substance from the atmosphere, a filter (chemical filter) for
adsorbing the chemical substance may be used. As the chemical
filter for removing the acidic substance, use is preferably made of
a chemical filter mixed with an acid-neutralizing substance. As the
acid-neutralizing substance, carbonate is preferable. As the
carbonate, potassium carbonate is preferable. Preferably, an
activated carbon filter containing an adsorber such as activated
carbon is used as the above-mentioned chemical filter. Preferably,
a filter comprising the adsorber, such as activated carbon, mixed
with the acid-neutralizing substance is used as the above-mentioned
chemical filter. Preferably, a basic chemical substance, such as
ammonia and amine, which inhibits a desired chemically amplifying
effect of the chemically amplified resist is removed together with
the acidic substance. In order to remove the basic chemical
substance, use may be made of a method of using a chemical filter
mixed with an alkali-neutralizing substance, such as phosphoric
acid.
[0107] It is preferable to use an air filter in combination with
the chemical filter for removing the acidic substance or the basic
substance. Preferably, such an air filter may be a HEPA filter
(high efficiency particulate air filter) or an ULPA filter (ultra
low penetration particulate air filter). As an ability of the air
filter, it is preferable to trap particles having a diameter of
0.05 .mu.m or more.
[0108] In this invention, the housing member for housing a mask
blank may be a member for housing and holding the mask blank (such
as an inner case of the container), a member for housing and
storing the mask blank (such as the container), and the like.
[0109] In this invention, a material of the housing member for
housing a mask blank is not particularly restricted. Preferably,
however, a resin material light in weight and easy in handling is
used. The resin material contains a high-molecular-weight compound
as a main component and an added substance added upon synthesis, an
unreacted substance, a low-molecular-weight compound, and so on.
Even at a relatively low temperature, a large amount of outgas
tends to be released with lapse of time. Under the circumstances,
this invention is highly useful. Such a resin material may be
polypropylene resin, acryl resin, polyethylene resin, polybutylene
resin, or polycarbonate resin. Among others, acryl resin,
particularly, polymethyl methacrylate (PMMA) resin is a material
releasing a relatively small amount of outgas. Therefore, by
applying this invention, it is possible to maintain an excellent
performance of the chemically amplified resist film formed on the
mask blank housed and stored. This invention is applicable not only
to the case where the mask blank is held in a vertical direction
but also to the case where the mask blank is supported in a
horizontal or an oblique direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0110] FIG. 1 is a perspective view of a cap of a container
according to an embodiment of this invention;
[0111] FIG. 2 is a perspective view showing a state where a mask
blank is housed in an inner case;
[0112] FIG. 3 is a perspective view of a container body (outer
case) of the container;
[0113] FIG. 4 is a vertical sectional view of the container in
which the mask blank is housed;
[0114] FIG. 5 is an enlarged vertical sectional view showing a
joint portion between the cap and the container body;
[0115] FIG. 6 is a view similar to FIG. 5 but showing a
modification of the container;
[0116] FIG. 7 is a view similar to FIG. 5 but showing another
modification of the container;
[0117] FIG. 8 is a view similar to FIG. 5 but showing still another
modification of the container;
[0118] FIG. 9 is a perspective view of a cap of a container
according to another embodiment of this invention;
[0119] FIG. 10 is a perspective view of a container body (outer
case) of the container in FIG. 10; and
[0120] FIG. 11 is a vertical sectional view of the container in
which a mask blank is housed.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
[0121] Now, referring to FIGS. 1 through 5, a first embodiment of
this invention will be described.
[0122] A container according to the first embodiment is adapted to
receive a mask blank 1 comprising a glass substrate having a
principal surface of a square shape, a light shielding thin film,
such as a chromium film, deposited on one principal surface of the
glass substrate, and a chemically amplified resist film formed on
the thin film. The container comprises an inner case 2 for housing
the mask blank 1, a container body 3 for housing the inner case 2,
and a cap 4 to be put on the container body 3 on the side of an
opening of the container body 3 (FIG. 4).
[0123] It is noted here that the mask blank 1 may be directly
housed in the container body 3 provided with a groove or the like
without using the inner case 2. However, use of the inner case 2 in
this embodiment is convenient because several to several tens of
mask blanks held in the inner case 2 can collectively be
handled.
[0124] The inner case 2 in this embodiment is provided with a
plurality of pairs of grooves 21 and 22 formed on a pair of
opposite inner side surfaces opposite to each other in a first
direction, respectively, in parallel to one another at a
predetermined interval and extending from the opening (upper side)
towards a bottom surface (lower side) of the inner case 2. The
grooves 21 and 22 are provided with opening windows 23 and 24
formed at lower portions adjacent the bottom surface of the inner
case 2, respectively. The bottom surface of the inner case 2 is
provided with an opening portion 27. Further, the bottom surface of
the inner case 2 is provided with a substrate supporting portion 26
which supports a lower end face of the mask blank 1 (FIGS. 2 and
4). In order to house and fix the inner case 2 in the container
body 3, a pair of depressed portions 28 and 29 are formed on a pair
of opposite outer side surfaces of the inner case 2 opposite to
each other in the second direction perpendicular to the first
direction, respectively, and extend from the bottom surface to an
intermediate position towards the opening (FIG. 2). A height of the
inner case 2 from an upper end face 25 adjacent to the opening to
the substrate supporting portion 26 corresponds to a major part of
a height of the mask blank 1 housed in the inner case 2. When the
mask blank 1 is housed in the inner case 2, an upper part of the
mask blank 1 protrudes from the upper end face 25 of the inner case
2 (FIG. 4). When several mask blanks 1 are inserted into the inner
case 2 along pairs of grooves 21 and 22, the mask blanks 1 stand in
parallel to one another at the predetermined interval. The mask
blanks 1 stand in a vertical direction in this embodiment but may
stand in an oblique direction.
[0125] The container body 3 in this embodiment is provided with
protruding portions 31 and 32 formed on a pair of opposite inner
side surfaces opposite to each other in the second direction and
adapted to be brought into contact with the depressed portions 28
and 29 of the inner case 2. The protruding portions 31 and 32 have
bottom portions connected to the bottom surface of the container
body 3 (FIG. 3). On a pair of opposite outer side surfaces opposite
to each other in the first direction, projecting portions 33 and 34
are formed near the opening, respectively. The projecting portions
33 and 34 have projecting surfaces substantially flush with an
outer peripheral surface 36 continuously formed at a position
slightly below an opening edge 35 of the container body 3.
[0126] The cap 4 in this embodiment has engaging portions 41 and 42
extending from a pair of opposite lower edges 47 thereof (i.e.,
opening edges to be fitted to the container body 3 and turned
upside in FIG. 1) and provided with recessed portions 43 and 44,
respectively. With this structure, when the cap 4 is put on the
container body 3, the recessed portions 43 and 44 are engaged with
the projecting portions 33 and 34 of the container body 3,
respectively, so that the cap 4 and the container body 3 are fixed
to each other (FIG. 4). The cap 4 is further provided with stoppers
45 and 46 formed on a pair of inner side surfaces opposite to each
other in the second direction and faced to each other (FIG. 1). The
stoppers 45 and 46 are adapted to be butted against the upper end
face 25 of the inner case 2 on the side of the opening to support
and fix the inner case 2 in the vertical direction. It is noted
here that the cap 4 may be directly put on the container body 3
without forming the recessed portions 43 and 44 of the cap 4 and
the projecting portions 33 and 34 of the container body 3. In case
where the recessed portions 43 and 44 of the cap 4 and the
projecting portions 33 and 34 of the container body 3 are engaged
with each other as engaging means, such engaging means may be
formed not only on a pair of opposite side surfaces but on all four
side surfaces.
[0127] Each of the inner case 2, the container body 3, and the cap
4 may be made of a resin material appropriately selected from, for
example, polypropylene, acryl, polyethylene, polycarbonate,
polyester, polyamide, polyimide, and polyethylene sulfide. Among
others, polycarbonate or polyester is preferable. As a material of
each of the container body 3 and the cap 4, polycarbonate is
preferable. As a material of the inner case 2, polyester is
preferable. As polyester, polyethylene terephthalate (PET) or
polybutylene terephthalate (PBT) is preferable. If electric charges
are accumulated during storage of the mask blank, discharge
breakdown may occur during a mask manufacturing process to cause
pattern defects. In view of the above, it is preferable to impart
conductivity to the container body 3, for example, by mixing carbon
in the resin material constituting the container body 3. It is also
preferable to impart conductivity by applying a conductive polymer
film onto a surface of the container body 3.
[0128] In this embodiment, an annular elastic member 5 is fitted
along the outer peripheral surface 36 continuous from the opening
edge 35 of the container body 3 (FIG. 3). When the cap 4 is put on
the container body 3 and the recessed portions 43 and 44 of the cap
4 are engaged with the projecting portions 33 and 34 of the
container body 3 so that the cap 4 and the container body 3 are
fixed to each other, an outer peripheral surface 48 continuous from
the lower edge of the cap 4 and the outer peripheral surface 36
continuous from the opening edge of the container body 3 overlap
each other frontward and rearward and are connected to each other
as illustrated in FIG. 5. Further, the elastic member 5 is
interposed at a joint portion therebetween so that the interior of
the container can be hermetically sealed.
[0129] As the elastic member 5, it is desired to use a material
which release only a small amount of a chemical component gas even
upon occurrence of change in temperature or pressure of the
atmosphere. For example, a packing material, such as polyolefin
elastomer and polyester elastomer, is particularly preferable.
Further, a silicone rubber may be used as far as release of a gas
component is small.
[0130] The elastic member 5 may have a rectangular section or a
circular section. The thickness or the width of the elastic member
5 can not be definitely mentioned. However, if the thickness or the
width is excessively large, the cap 4 is difficult to be fitted and
removed. On the other hand, if the thickness or the width is
excessively small, tight contact between the elastic member 5 and
the joint portion between the cap 4 and the container body 3 may be
incomplete so that the function of hermetically sealing the
interior of the container is difficult to obtain. Therefore, the
thickness or the width of the elastic member 5 may appropriately be
determined depending upon the size of the container and the shape
and the size of the joint portion.
[0131] In this embodiment, the elastic member 5 having an annular
shape and an appropriate size is fitted to the opening edge of the
container body 3. Alternatively, the elastic member may
preliminarily be adhered.
[0132] As described above, in the container according to this
embodiment, the elastic member 5 is interposed between the cap 4
and the container body 3 at the joint portion when the cap 4 is put
on the container body 3. Thus, the container can be hermetically
sealed. Therefore, it is possible to store the mask blank for a
long period of time while maintaining a clean atmosphere upon
housing the mask blank and to prevent ambient air from entering the
interior of the container to cause contamination by a chemical
component or the like contained in the ambient air. Therefore, this
invention is suitable for housing a mask blank having a chemically
amplified resist film susceptible to an influence of a storage
environment and required to be stored in an especially clean
atmosphere.
[0133] Referring to FIG. 6, a container according to a modification
of the first embodiment is similar in structure to the first
embodiment except that the elastic member 5 is formed at a
different position of the container body 3. Specifically, the
elastic member 5 is interposed at a joint surface between the outer
peripheral surface 48 continuous from the lower edge of the cap 4
and the outer peripheral surface 36 continuous from the opening
edge of the container body 3 when the cap 4 is put on the container
body 3.
[0134] Referring to FIG. 7, a container according to another
modification is similar in structure to the first embodiment except
that the lower edge of the cap 4 is provided with a flange 49 while
the opening edge of the container body 3 is provided with a flange
37. When the cap 4 is put on the container body 3 and fixed, the
flanges 49 and 37 are connected to each other with the elastic
member 5 interposed therebetween.
[0135] Referring to FIG. 8, a container according to still another
modification is similar to that in FIG. 7 except that the flange 49
at the opening edge of the container body 3 is provided with a
recessed portion to bury a part of the elastic member 5.
[0136] In case where the flanges are overlapped and connected, use
may be made of a locking member 6 (see FIG. 8) for clamping the
joint portion from upper and lower sides. By merely sliding the
locking member 6 along the flanges, the joint portion can be fixed
and locked. Therefore, the use of the locking member 6 is
advantageous in that the cap 4 can easily be fitted and removed,
for example, by robotic manipulation. In order to avoid the locking
member 6 from being deviated from a sliding direction, it is
desired that, in a locking portion of the joint portion, the flange
of the cap 4 is provided with a protrusion 49a extending upward
from an end of the flange while the flange of the container body 3
is provided with a protrusion 37a extending downward from an end of
the flange.
[0137] In each of the first embodiment and the modifications
thereof, the elastic member is formed on the container body. Not
being limited thereto, the elastic member may be adhered to the
cap. Alternatively, the elastic member may be formed on each of the
container body and the cap. In any event, the effect of this
invention is advantageously achieved.
[0138] As will readily be understood, this invention is applicable
not only to a mask blank having a square shape but also to a case
where a substrate of a different shape, such as a disk-like shape,
is housed.
[0139] Hereinafter, this invention will be described in conjunction
with a specific example.
Example
[0140] A half tone film was formed on a quartz substrate by
sputtering. On the half tone film, a resist film was formed by spin
coating to produce a mask blank with a resist film. As the half
tone film, a MoSi metal film was used. As the resist film, a
chemically amplified resist film of a positive type was used.
[0141] Ten mask blanks were produced in the above-mentioned manner
and housed in the container according to the first embodiment
illustrated in FIGS. 1 through 5. Each of the cap and the container
body was made of polycarbonate. The inner case was made of
polybutylene terephthalate. As the elastic member, an annular
packing member of polyolefin elastomer was used. A housing
operation was carried out in a clean room cleaned by an activated
carbon filter and an ULPA filter.
[0142] The container was packaged in a package bag and transported
by air cargo. The container after transported was opened in a clean
room similar to that described above to take out the mask blanks.
Each mask blank was subjected to electron beam writing,
development, and etching in a predetermined manner to produce a
phase-shift transfer mask. The quality of each phase-shift transfer
mask thus produced was inspected in detail by the use of a scanning
electron microscope. As a result, no serious defect was found in
any one of the ten phase-shift masks.
Comparative Example
[0143] Mask blanks were produced, housed, and transported in a
manner similar to the Example except that a known container without
using an elastic member at the joint portion of the container (a
cap, a container body, and an inner case were made of materials
similar to those in the Example) was used and that an adhesive tape
was attached to the joint portion of the container to seal the
container after housing the mask blanks.
[0144] By the use of the mask blanks after transportation, phase
shift masks were produced in the manner similar to the Example. The
quality of each phase-shift mask was inspected in detail by the use
of a scanning electron microscope. As a result, disturbance in line
width of a pattern was observed in each of the ten phase-shift
masks. The reason is supposed as follows. Since sealing of the
container was incomplete, ambient air entered into the interior of
the container during transportation. A certain chemical component
in the ambient air chemically contaminated the chemically amplified
resist film of the mask blank.
Second Embodiment
[0145] Now, referring to FIGS. 2 and 9 through 11, a container for
a mask blank according to a second embodiment of this invention
will be described.
[0146] A container according to the second embodiment is adapted to
receive a mask blank 1 comprising a glass substrate having a
principal surface of a square shape, a light shielding thin film,
such as a chromium film, deposited on one principal surface of the
glass substrate, and a chemically amplified resist film formed on
the thin film. The container comprises an inner case 2 for housing
the mask blank 1, a container body 3 for housing the inner case 2,
and a cap 4 to be put on the container body 3 on the side of an
opening of the container body 3 (FIG. 11).
[0147] It is noted here that the mask blank 1 may be directly
housed in the container body 3 provided with a groove or the like
without using the inner case 2. However, use of the inner case 2 is
convenient because several to several tens of mask blanks held in
the inner case 2 can collectively be handled.
[0148] The inner case 2 in this embodiment is provided with a
plurality of pairs of grooves 21 and 22 formed on a pair of
opposite inner side surfaces opposite to each other in a first
direction, respectively, in parallel to one another at a
predetermined interval and extending from the opening (upper side)
towards a bottom surface (lower side) of the inner case 2. The
grooves 21 and 22 are provided with opening windows 23 and 24
formed at lower portions adjacent the bottom surface of the inner
case 2, respectively. The bottom surface of the inner case 2 is
provided with an opening portion 27. Further, the bottom surface of
the inner case 2 is provided with a substrate supporting portion 26
which supports a lower end face of the mask blank 1 (FIGS. 2 and
11). In order to house and fix the inner case 2 in the container
body 3, a pair of depressed portions 28 and 29 are formed on a pair
of opposite outer side surfaces of the inner case 2 opposite to
each other in the second direction perpendicular to the first
direction, respectively, and extend from the bottom surface to an
intermediate position towards the opening (FIG. 2). A height of the
inner case 2 from an upper end face 25 adjacent to the opening to
the substrate supporting portion 26 corresponds to a major part of
a height of the mask blank 1 housed in the inner case 2. When the
mask blank 1 is housed in the inner case 2, an upper part of the
mask blank 1 protrudes from the upper end face 25 of the inner case
2 (FIG. 11). When several mask blanks 1 are inserted into the inner
case 2 along pairs of grooves 21 and 22, the mask blanks 1 stand in
parallel to one another at the predetermined interval. The mask
blanks 1 stand in a vertical direction in this embodiment but may
stand in an oblique direction.
[0149] The container body 3 in this embodiment is provided with
protruding portions 31 and 32 formed on a pair of opposite inner
side surfaces opposite to each other in the second direction and
adapted to be brought into contact with the depressed portions 28
and 29 of the inner case 2. The protruding portions 31 and 32 have
bottom portions connected to the bottom surface of the container
body 3 (FIG. 10). On a pair of opposite outer side surfaces
opposite to each other in the first direction, projecting portions
33 and 34 are formed near the opening, respectively. The projecting
portions 33 and 34 have projecting surfaces substantially flush
with an outer peripheral surface 36 continuously formed at a
position slightly below an opening edge 35 of the container body
3.
[0150] The cap 4 in this embodiment has engaging portions 41 and 42
extending from a pair of opposite lower edges 47 thereof (i.e.,
opening edges to be fitted to the container body 3 and turned
upside in FIG. 9) and provided with recessed portions 43 and 44,
respectively. With this structure, when the cap 4 is put on the
container body 3, the recessed portions 43 and 44 are engaged with
the projecting portions 33 and 34 of the container body 3,
respectively, so that the cap 4 and the container body 3 are fixed
to each other (FIG. 11). The cap 4 is further provided with
stoppers 45 and 46 formed on a pair of inner side surfaces opposite
to each other in the second direction and faced to each other (FIG.
9). The stoppers 45 and 46 are adapted to be butted against the
upper end face 25 of the inner case 2 on the side of the opening to
support and fix the inner case 2 in the vertical direction. It is
noted here that the cap 4 may be directly put on the container body
3 without forming the recessed portions 43 and 44 of the cap 4 and
the projecting portions 33 and 34 of the container body 3. In case
where the recessed portions 43 and 44 of the cap 4 and the
projecting portions 33 and 34 of the container body 3 are engaged
with each other as engaging means, such engaging means may be
formed not only on a pair of opposite side surfaces but on all four
side surfaces.
[0151] Each of the inner case 2, the container body 3, and the cap
4 may be made of a resin material appropriately selected from, for
example, polypropylene, acryl, polyethylene, polycarbonate,
polyester, polyamide, polyimide, and polyethylene sulfide. Among
others, polycarbonate or polyester is preferable. As a material of
each of the container body 3 and the cap 4, polycarbonate is
preferable. As a material of the inner case 2, polyester is
preferable. As polyester, polyethylene terephthalate (PET) or
polybutylene terephthalate (PBT) is preferable. If electric charges
are accumulated during storage of the mask blank, discharge
breakdown may occur during a mask manufacturing process to cause
pattern defects. In view of the above, it is preferable to impart
conductivity to the container body 3, for example, by mixing carbon
in the resin material constituting the container body 3.
[0152] When the cap 4 is put on the container body 3 and the
recessed portions 43 and 44 of the cap 4 are engaged with the
projecting portions 33 and 34 of the container body 3 so that the
cap 4 and the container body 3 are fixed to each other, an outer
peripheral surface 48 continuous from the lower edge of the cap 4
and the outer peripheral surface 36 continuous from the opening
edge of the container body 3 overlap each other frontward and
rearward and are connected to each other.
[0153] In this embodiment, the cap 4 is provided with a vent hole
49 formed at one corner thereof to allow communication between the
ambient air and the internal air. The vent hole 49 is provided with
a filtering member 5' faced to the inside of the cap 4 (FIGS. 9 and
11). The filtering member 5' comprises a filter holding portion 52
having a flange-like shape and holding an internal filter, pipes 51
and 53 integrally connected to the filter holding portion 52 on
opposite sides thereof to serve as a gas flow path. In this
embodiment, the pipe 51 is attached to the vent hole 49 of the cap
4 while the pipe 53 faces the inside of the cap 4. The filter
holding portion 52 can be divided so as to mount and remove the
internal filter. The corner of the cap 4 provided with the vent
hole 49 is depressed inward and the filter holding portion 52 is
brought into contact with the depressed portion.
[0154] Even if the ambient air enters through the vent hole 49 in
the state where the mask blanks are housed and stored in the
container according to this embodiment, foreign matters such as a
chemical substance contained in the ambient air can be removed by
the filtering member 5' and cleaned ambient air alone enters the
interior of the container. Therefore, cleanliness in the container
is maintained.
[0155] As the filter of the filtering member 5', use may be made
of, for example, an air filter generally used in a clean room.
Preferably, such a filter may be a HEPA filter (high efficiency
particulate air filter) or an ULPA filter (ultra low penetration
particulate air filter). The HEPA filter is a high-efficiency air
filter mainly used for air purification in a clean room and is
generally made of a glass fiber material. The ULPA filter is an
ultra-high performance filter developed following the development
of the fine process technology in ULSI manufacture and is generally
made of a glass fiber or a fluorine-based resin material. As an
ability of the air filter, it is preferable to trap particles
having a diameter of 0.05 .mu.m or more. The air filter such as the
HEPA filter or the ULPA filter may be appropriately selected taking
into account cost effectiveness and the like. Practically, the HEPA
filter may be used.
[0156] In case where a mask blank having a chemically amplified
resist film especially required to eliminate contamination by a
chemical substance is housed and stored, it is preferable to use a
filter for adsorbing the chemical substance (chemical filter),
alone or in combination with the above-mentioned air filter. As the
chemical filter, for example, an activated carbon filter or an ion
exchange filter may preferably be used. The chemical filter such as
the activated carbon filter or the ion exchange filter may be
appropriately selected taking into account cost effectiveness and
the like. Practically, the activated carbon filter may be used.
[0157] The chemical substance contaminating the chemically
amplified resist, i.e., inhibiting a desired chemically amplifying
effect of the chemically amplified resist (the chemically
amplifying effect is enhanced or suppressed as compared with a
desired extent and a predetermined resist pattern can not be
formed) includes an acidic chemical substance and a basic chemical
substance. The acidic chemical substances may be a substance
containing chlorine ions, a substance containing sulfate ions, a
substance containing phosphate ions, or a substance containing
nitrate ions. The basic chemical substance may be a compound
containing nitrogen, such as ammonia, amine, aniline, or nitrile,
which suppresses or inhibits (for example, deactivates) the
function of an acid as a catalyst for the chemically amplifying
reaction.
[0158] As described above, in the container according to this
embodiment, even if the ambient air enters through the vent hole 49
while the mask blank is housed and stored, the foreign matters such
as the chemical substance contained in the ambient air are
prevented by the filtering member 5' from entering the interior of
the container. Therefore, it is possible to store the mask blank
while maintaining a clean atmosphere upon housing the mask blank
even for a long period of time and to prevent the ambient air from
directly entering the interior of the container to contaminate the
mask blank by the foreign matters such as the chemical substance
contained in the ambient air. Therefore, this invention is suitable
for housing and storing the mask blank having a chemically
amplified resist film susceptible to an influence of the storage
environment and required to be stored in an especially clean
atmosphere.
[0159] Generally, the ambient air may enter through the joint
portion between the cap 4 and the container body 3, i.e., the joint
portion where the outer peripheral surface 48 continuous from the
lower edge of the cap 4 and the outer peripheral surface 36
continuous from the opening edge of the container body 3 overlap
each other when the cap 4 is put on the container body 3. However,
by providing the container with the vent hole 49, the ambient air
will preferentially enter through the vent hole 49 so that the
contamination of the interior of the container is sufficiently
prevented.
[0160] In this embodiment, the vent hole 49 and the filtering
member 5' are formed at one corner of the cap 4. Not being limited
thereto, the vent hole 49 and the filtering member 5' may be formed
at any position except the corner as far as the mask blank housed
in the container is not contacted therewith. The vent hole 49 and
the filtering member 5' may be formed at a plurality of positions,
not at one position. Further, the vent hole 49 and the filtering
member 5' may be formed not at a top plate of the cap 4 in this
embodiment but may be formed at an appropriate position on a side
wall plate or on the container body 3.
[0161] The means for inhibiting entry of the foreign matters
contained in the ambient air into the container is not limited to
that in this embodiment. For example, a vent hole is formed at an
appropriate position of the container and a filter or a sealing
member having a filtering function is directly attached to the vent
hole so as to cover or close the vent hole from the inside of the
container. Further, without forming the vent hole, a filter or a
member having a filtering function may be attached to the joint
portion between the cap 4 and the container body 3.
[0162] The mask blank to which this invention is applicable
includes a mask blank comprising a light transparent substrate such
as a glass substrate and a light shielding film such as Cr formed
on the substrate, a mask blank used to produce a phase shift mask
and comprising a substrate and a half tone (semitransparent) film
formed on the substrate, and a mask blank used to produce a
reflective mask and comprising a substrate, a reflective film such
as a Mo/Si multilayer reflective film for reflecting exposure
light, and an absorber film such as a Ta-based absorber film for
absorbing the exposure light. As will readily be understood, this
invention is applicable not only to a case where a mask blank of a
square shape is housed but also to a case where a mask blank of a
different shape, such as a disk-like shape, is housed.
[0163] Now, this embodiment will be described in conjunction with a
specific example.
Example
[0164] A halftone film was formed on a quartz substrate (6
inch.times.6 inch) by sputtering. On the halftone film, a resist
film was formed by spin coating to produce a mask blank with a
resist film. As the half tone film, a MoSi metal film was used. As
the resist film, a chemically amplified resist film of a positive
type was used.
[0165] 100 mask blanks were produced in the above-mentioned manner
and housed in 10 containers according to the second embodiment
described in conjunction with FIGS. 2 and 9 through 11. Each of the
cap and the container body was made of polycarbonate. The inner
case was made of polybutylene terephthalate. As a filter of a
filtering member attached to the container, a combination of the
activated carbon filter and the HEPA filter was used. A housing
operation was carried out in a clean room cleaned by an activated
carbon filter and an ULPA filter.
[0166] The container was packaged in a package bag and transported
by air cargo. The container after transported was opened in a clean
room similar to that described above to take out the mask blanks.
Each mask blank was subjected to electron beam writing,
development, and etching in a predetermined manner to produce a
phase-shift transfer mask. The quality of each phase-shift transfer
mask thus produced was inspected in detail by the use of a scanning
electron microscope. As a result, no serious defect was found in
any one of the 100 phase-shift masks.
Comparative Example
[0167] Mask blanks were produced, housed, and transported in a
manner similar to the Example except that a known container without
providing the container with the vent hole and the filtering member
(a cap, a container body, and an inner case were made of materials
similar to those in the Example) was used and that an adhesive tape
was attached to the joint portion of the container to seal the
container after housing the mask blanks.
[0168] By the use of the mask blanks after transportation, phase
shift masks were produced in the manner similar to the Example. The
quality of each phase-shift mask was inspected in detail by the use
of a scanning electron microscope. As a result, disturbance in line
width of a pattern was observed in each of the 100 phase-shift
masks. The reason is supposed as follows. The ambient air entered
into the interior of the container during transportation. A certain
chemical component in the ambient air chemically contaminated the
chemically amplified resist film of the mask blank.
Third Embodiment
[0169] Now, referring to FIGS. 1, 2, 4, and 10, a container
according to a third embodiment will be described.
[0170] The container for housing a mask blank, used in this
embodiment, is not specifically limited.
[0171] A container according to the third embodiment is adapted to
receive a mask blank 1 comprising a glass substrate having a
principal surface of a square shape, a light shielding thin film,
such as a chromium film, deposited on one principal surface of the
glass substrate, and a chemically amplified resist film formed on
the thin film. The container comprises an inner case 2 for housing
the mask blank 1, a container body 3 for housing the inner case 2,
and a cap 4 to be put on the container body 3 on the side of an
opening of the container body 3 (FIG. 4).
[0172] It is noted here that the mask blank 1 may be directly
housed in the container body 3 provided with a groove or the like
without using the inner case 2. However, use of the inner case 2 in
this embodiment is convenient because several to several tens of
mask blanks held in the inner case 2 can collectively be
handled.
[0173] The inner case 2 is provided with a plurality of pairs of
grooves 21 and 22 formed on a pair of opposite inner side surfaces
opposite to each other in a first direction, respectively, in
parallel to one another at a predetermined interval and extending
from the opening (upper side) towards a bottom surface (lower side)
of the inner case 2. The grooves 21 and 22 are provided with
opening windows 23 and 24 formed at lower portions adjacent the
bottom surface of the inner case 2, respectively. The bottom
surface of the inner case 2 is provided with an opening portion 27.
Further, the bottom surface of the inner case 2 is provided with a
substrate supporting portion 26 which supports a lower end face of
the mask blank 1 (FIGS. 2 and 4). In order to house and fix the
inner case 2 in the container body 3, a pair of depressed portions
28 and 29 are formed on a pair of opposite outer side surfaces of
the inner case 2 opposite to each other in the second direction
perpendicular to the first direction, respectively, and extend from
the bottom surface to an intermediate position towards the opening
(FIG. 2). A height of the inner case 2 from an upper end face 25
adjacent to the opening to the substrate supporting portion 26
corresponds to a major part of a height of the mask blank 1 housed
in the inner case 2. When the mask blank 1 is housed in the inner
case 2, an upper part of the mask blank 1 protrudes from the upper
end face 25 of the inner case 2 (FIG. 4). When several mask blanks
1 are inserted into the inner case 2 along pairs of grooves 21 and
22, the mask blanks 1 stand in parallel to one another at the
predetermined interval. The mask blanks 1 stand in a vertical
direction in this embodiment but may stand in an oblique
direction.
[0174] The container body 3 is provided with protruding portions 31
and 32 formed on a pair of opposite inner side surfaces opposite to
each other in the second direction and adapted to be brought into
contact with the depressed portions 28 and 29 of the inner case 2.
The protruding portions 31 and 32 have bottom portions connected to
the bottom surface of the container body 3 (FIG. 10). On a pair of
opposite outer side surfaces opposite to each other in the first
direction, projecting portions 33 and 34 are formed near the
opening, respectively. The projecting portions 33 and 34 have
projecting surfaces substantially flush with an outer peripheral
surface 36 continuously formed at a position slightly below an
opening edge 35 of the container body 3.
[0175] The cap 4 in this embodiment has engaging portions 41 and 42
extending from a pair of opposite lower edges 47 thereof (i.e.,
opening edges to be fitted to the container body 3 and turned
upside in FIG. 1) and provided with recessed portions 43 and 44,
respectively. With this structure, when the cap 4 is put on the
container body 3, the recessed portions 43 and 44 are engaged with
the projecting portions 33 and 34 of the container body 3,
respectively, so that the cap 4 and the container body 3 are fixed
to each other (FIG. 4). The cap 4 is further provided with stoppers
45 and 46 formed on a pair of inner side surfaces opposite to each
other in the second direction and faced to each other (FIG. 1). The
stoppers 45 and 46 are adapted to be butted against the upper end
face 25 of the inner case 2 on the side of the opening to support
and fix the inner case 2 in the vertical direction. It is noted
here that the cap 4 may be directly put on the container body 3
without forming the recessed portions 43 and 44 of the cap 4 and
the projecting portions 33 and 34 of the container body 3. In case
where the recessed portions 43 and 44 of the cap 4 and the
projecting portions 33 and 34 of the container body 3 are engaged
with each other as engaging means, such engaging means may be
formed not only on a pair of opposite side surfaces but on all four
side surfaces.
[0176] Each of the inner case 2, the container body 3, and the cap
4 may be made of a resin material appropriately selected from, for
example, polypropylene, acryl, polyethylene, polycarbonate,
polyester, polyamide, polyimide, and polyethylene sulfide. Among
others, polycarbonate or polyester is preferable. As a material of
each of the container body 3 and the cap 4, polycarbonate is
preferable. As a material of the inner case 2, polyester is
preferable. As polyester, polyethylene terephthalate (PET) or
polybutylene terephthalate (PBT) is preferable. If electric charges
are accumulated during storage of the mask blank, discharge
breakdown may occur during a mask manufacturing process to cause
pattern defects. In view of the above, it is preferable to impart
conductivity to the container body 3, for example, by mixing carbon
in the resin material constituting the container body 3.
[0177] When the cap 4 is put on the container body 3 and the
recessed portions 43 and 44 of the cap 4 are engaged with the
projecting portions 33 and 34 of the container body 3 so that the
cap 4 and the container body 3 are fixed to each other, an outer
peripheral surface 48 continuous from the lower edge of the cap 4
and the outer peripheral surface 36 continuous from the opening
edge of the container body 3 overlap each other frontward and
rearward and are connected to each other.
[0178] As described in structure 16, the container preferably has
means for absorbing or adsorbing an acidic substance. Even if the
mask blank is housed in the container together with an atmosphere
from which the acidic substance is removed, the acidic substance
may enter together with the ambient air through the joint portion
between the cap and the container body of the container during
transportation and storage of a mask blank package obtained by
housing the mask blank in the container. Even in this event, if the
container has means for absorbing or adsorbing the acidic
substance, the acidic substance contained in the ambient air can be
removed and the interior of the container can be kept at a clean
atmosphere. As the means for absorbing or adsorbing the acidic
substance, for example, it is a simple method to dispose a material
for absorbing or adsorbing the acidic substance (absorber or
adsorber for the acidic substance) in the container. As the
material for absorbing or adsorbing the acidic substance, use may
be made of, for example, carbonate such as potassium carbonate.
Alternatively, the material for absorbing or adsorbing the acidic
substance may be contained in a material constituting the
container. Further, an adsorber such as activated carbon may be
used in combination.
[0179] As described in structure 17, the mask blank package
according to this invention is obtained by housing the mask blank
having a chemically amplified resist film in the container having
an atmosphere which does not contain at least the acidic substance.
The phrase "does not contain the acidic substance" is not
restricted to the case where the acidic substance is not present in
the atmosphere at all but may be the case where a small amount of
the acidic substance is contained in the atmosphere as far as the
chemically amplified resist is not contaminated. A specific
allowance value in case where the acidic substance is contained in
the atmosphere is equivalent to the degree of removal of the acidic
substance mentioned above.
[0180] As described above, the atmosphere from which the acidic
substance is removed may be used upon housing the mask blank.
Further, the above-mentioned atmosphere is preferably used also in
a manufacturing process of the mask blank. Specifically, as
described in structure 18, a thin film for forming a mask pattern
is deposited on a substrate such as a glass substrate and,
thereafter, a chemically amplified resist film is formed on the
thin film under an atmosphere from which at least an acidic
substance is removed. Thus, it is possible to prevent adhesion of
the acidic substance in the stage of manufacture of the mask blank
with a resist film
[0181] It is suitable to use the above-mentioned atmosphere in a
series of steps from manufacture of the mask blank to housing and
packaging. Specifically, as described in structure 19, in a series
of steps including a resist forming step of forming a chemically
amplified resist film on a mask blank obtained by depositing on a
substrate a thin film for forming a mask pattern, a post-treating
step as an optional step for treating the mask blank with the
resist film, an inspection step as an optional step for inspecting
the mask blank with the resist film, and a housing/packaging step
of housing and packaging the mask blank with the resist film in a
container, at least one step is preferably carried out under an
atmosphere from which at least the acidic substance is removed. For
example, the post-treating step as an optional step is a heating
(baking) step for improving adhesiveness of the resist film or a
dry cleaning step.
[0182] In particular, a series of steps from the resist forming
step of forming the chemically amplified resist film on the mask
blank to the housing/packaging step of housing and packaging the
mask blank with a resist film are suitably carried out under the
atmosphere from which at least the acidic substance is removed.
[0183] The mask blank to which this invention is applicable
includes a mask blank comprising a light transparent substrate such
as a glass substrate and a light shielding film such as Cr formed
on the substrate, a mask blank used to produce a phase shift mask
and comprising a substrate and a half tone (semitransparent) film
formed on the substrate, and a mask blank used to produce a
reflective mask and comprising a substrate, a reflective film such
as a Mo/Si multilayer reflective film for reflecting exposure
light, and an absorber film such as a Ta-based absorber film for
absorbing the exposure light.
[0184] According to this invention, the atmosphere from which at
least the acidic substance is removed is used upon housing the mask
blank having a chemically amplified resist film into the container.
In this manner, it is possible to prevent contamination due to
adhesion of the acidic substance, which affects a desired
chemically amplifying effect of the chemically amplified resist and
excessively enhances the chemically amplifying effect. Therefore, a
stable resist performance is assured even after storage of the mask
blank. As a result, upon manufacture of a mask, a stable resist
pattern is formed and a high-quality transfer mask is obtained with
a desired mask pattern. According to this invention, even if the
mask blank package as a combination of the container and the mask
blank having a chemically amplified resist film and housed in the
container is transported to a remote place by the use of traffic
means, contamination of the resist film of the mask blank housed
therein can be suppressed. Therefore, it is possible to assure high
reliability in transportation of the mask blank to a remote
place.
[0185] According to this invention, after the thin film for forming
a mask pattern is deposited on the substrate, the chemically
amplified resist film is formed on the thin film under the
atmosphere from which at least the acidic substance is removed. In
this manner, it is possible to prevent adhesion of the acidic
substance in the stage of manufacture of the mask blank with a
resist film.
[0186] In a series of steps from manufacture of the mask blank to
housing and packaging, the atmosphere from which the acidic
substance is removed is used. In this manner, it is possible to
advantageously prevent contamination by the acidic substance.
[0187] Now, the third embodiment will be described in conjunction
with a specific example.
Example
[0188] A halftone film was formed on a quartz substrate (6
inch.times.6 inch) by sputtering. On the halftone film, a resist
film was formed by spin coating to produce a mask blank with a
resist film. As the half tone film, a MoSi metal film was used. As
the resist film, a chemically amplified resist film of a positive
type was used. The resist film was formed in a clean room cleaned
by an activated carbon filter containing potassium carbonate and an
ULPA filter.
[0189] 100 mask blanks were manufactured in the above-mentioned
manner and housed in 10 containers having the structure illustrated
in FIGS. 1 through 4. Each of the cap and the container body was
made of polycarbonate. The inner case was made of polybutylene
terephthalate. A housing operation was carried out in a clean room
cleaned by an activated carbon filter and an ULPA filter. As the
activated carbon filter, a combination of an activated carbon
filter containing potassium carbonate and an activated carbon
filter containing phosphoric acid was used.
[0190] The container was packaged in a package bag and transported
by air cargo. The container after transported was opened in a clean
room similar to that described above to take out the mask blanks.
Each mask blank was subjected to electron beam writing,
development, and etching in a predetermined manner to produce a
phase-shift transfer mask. The quality of each phase-shift transfer
mask thus produced was inspected in detail by the use of a scanning
electron microscope. As a result, no serious defect was found in
any one of the 100 phase-shift masks
Comparative Example
[0191] Mask blanks were produced, packaged, and transported in the
manner similar to the Example except that the activated carbon
filter containing potassium carbonate was not used in the clean
room.
[0192] By the use of the mask blanks after transportation, phase
shift masks were produced in the manner similar to the Example. The
quality of each phase-shift mask was inspected in detail by the use
of a scanning electron microscope. As a result, disturbance in line
width of a pattern was observed in each of the 100 phase-shift
masks. The reason is supposed as follows. Specifically, a certain
acidic substance was present in the atmosphere within the clean
room and trapped in the container. In this state, the mask blanks
were packaged. During transportation, the chemically amplified
resist film of the mask blank was chemically contaminated by the
acidic substance.
Fourth Embodiment
[0193] Now, referring to FIGS. 1, 2, 4, and 10, a fourth embodiment
of this invention will be described.
[0194] At first, as a housing member to which this invention is
applicable, description will be made of an example of a container
for housing a mask blank.
[0195] A container according to the fourth embodiment is adapted to
receive a mask blank 1 comprising a glass substrate having a
principal surface of a square shape, a light shielding thin film,
such as a chromium film, deposited on one principal surface of the
glass substrate, and a chemically amplified resist film formed on
the thin film. The container comprises an inner case 2 for housing
the mask blank 1, a container body 3 for housing the inner case 2,
and a cap 4 to be put on the container body 3 on the side of an
opening of the container body 3 (FIG. 4).
[0196] It is noted here that the mask blank 1 may be directly
housed in the container body 3 provided with a groove or the like
without using the inner case 2. However, use of the inner case 2 in
this embodiment is convenient because several to several tens of
mask blanks held in the inner case 2 can collectively be
handled.
[0197] The inner case 2 is provided with a plurality of pairs of
grooves 21 and 22 formed on a pair of opposite inner side surfaces
opposite to each other in a first direction, respectively, in
parallel to one another at a predetermined interval and extending
from the opening (upper side) towards a bottom surface (lower side)
of the inner case 2. The grooves 21 and 22 are provided with
opening windows 23 and 24 formed at lower portions adjacent the
bottom surface of the inner case 2, respectively. The bottom
surface of the inner case 2 is provided with an opening portion 27.
Further, the bottom surface of the inner case 2 is provided with a
substrate supporting portion 26 which supports a lower end face of
the mask blank 1 (FIGS. 2 and 4). In order to house and fix the
inner case 2 in the container body 3, a pair of depressed portions
28 and 29 are formed on a pair of opposite outer side surfaces of
the inner case 2 opposite to each other in the second direction
perpendicular to the first direction, respectively, and extend from
the bottom surface to an intermediate position towards the opening
(FIG. 2). A height of the inner case 2 from an upper end face 25
adjacent to the opening to the substrate supporting portion 26
corresponds to a major part of a height of the mask blank 1 housed
in the inner case 2. When the mask blank 1 is housed in the inner
case 2, an upper part of the mask blank 1 protrudes from the upper
end face 25 of the inner case 2 (FIG. 4). When several mask blanks
1 are inserted into the inner case 2 along pairs of grooves 21 and
22, the mask blanks 1 stand in parallel to one another at the
predetermined interval. The mask blanks 1 stand in a vertical
direction in this embodiment but may stand in an oblique
direction.
[0198] The container body 3 is provided with protruding portions 31
and 32 formed on a pair of opposite inner side surfaces opposite to
each other in the second direction and adapted to be brought into
contact with the depressed portions 28 and 29 of the inner case 2.
The protruding portions 31 and 32 have bottom portions connected to
the bottom surface of the container body 3 (FIG. 10). On a pair of
opposite outer side surfaces opposite to each other in the first
direction, projecting portions 33 and 34 are formed near the
opening, respectively. The projecting portions 33 and 34 have
projecting surfaces substantially flush with an outer peripheral
surface 36 continuously formed at a position slightly below an
opening edge 35 of the container body 3.
[0199] The cap 4 in this embodiment has engaging portions 41 and 42
extending from a pair of opposite lower edges 47 thereof (i.e.,
opening edges to be fitted to the container body 3 and turned
upside in FIG. 1) and provided with recessed portions 43 and 44,
respectively. With this structure, when the cap 4 is put on the
container body 3, the recessed portions 43 and 44 are engaged with
the projecting portions 33 and 34 of the container body 3,
respectively, so that the cap 4 and the container body 3 are fixed
to each other (FIG. 4). The cap 4 is further provided with stoppers
45 and 46 formed on a pair of inner side surfaces opposite to each
other in the second direction and faced to each other (FIG. 1). The
stoppers 45 and 46 are adapted to be butted against the upper end
face 25 of the inner case 2 on the side of the opening to support
and fix the inner case 2 in the vertical direction.
[0200] As described above, the material of each of the inner case
2, the container body 3, and the cap 4 is preferably a resin
material. Among others, a PMMA resin is preferable. Each of these
members is subjected to treatment for removing the chemical
substance, such as heat treatment, according to this invention
before the mask blank is housed. If electric charges are
accumulated during storage of the mask blank, discharge breakdown
may occur during a mask manufacturing process to cause pattern
defects. In view of the above, it is possible to impart
conductivity to the container body 3, for example, by mixing carbon
in the resin material constituting the container body 3.
[0201] When the cap 4 is put on the container body 3 and the
recessed portions 43 and 44 of the cap 4 are engaged with the
projecting portions 33 and 34 of the container body 3 so that the
cap 4 and the container body 3 are fixed to each other, an outer
peripheral surface 48 continuous from the lower edge of the cap 4
and the outer peripheral surface 36 continuous from the opening
edge of the container body 3 overlap each other frontward and
rearward and are connected to each other.
[0202] As described in structure 23, a member which has been formed
as a housing member may be subjected to the treatment for removing
the chemical substance or a material before formed into the housing
member may be subjected to the treatment for removing the chemical
substance. Further, it is possible both the material before formed
into the housing member and the housing member after forming are
subjected to the treatment for removing the chemical substance.
[0203] As described in structure 24, the treating method according
to this invention is applicable to a method of manufacturing a mask
blank housing member. In this case, this invention is applicable to
a method of producing a housing member by treating the housing
member as a formed product by the method of this invention or to a
method of producing a recycled housing member by treating a used
housing member by the method of this invention. Specifically, the
treating method of this invention is applicable to a method of
producing a mask blank container by forming a resin material and to
a method of producing a recycled mask blank container by treating a
used mask blank container, which has been used once or more, by the
method of this invention.
[0204] As described in structure 25, a mask blank package according
to this invention is obtained by housing a mask blank with a
chemically amplified resist film in a member subjected to a
treatment for removing a chemical substance inhibiting a chemically
amplifying effect of the chemically amplified resist.
[0205] The mask blank to which this invention is applicable is not
specifically limited but includes a mask blank comprising a light
transparent substrate such as a glass substrate and a light
shielding film such as Cr formed on the substrate, a mask blank
used to produce a phase shift mask and comprising a substrate and a
phase shift film formed on the substrate, and a mask blank used to
produce a reflective mask and comprising a substrate, a reflective
film such as a Mo/Si multilayer reflective film for reflecting
exposure light, and an absorber film such as a Ta-based absorber
film for absorbing the exposure light.
[0206] According to this invention, the housing member for housing
the mask blank having a chemically amplified resist film is
subjected to the treatment for removing from the housing member the
chemical substance inhibiting the chemically amplifying effect of
the chemically amplified resist. Thus, it is possible to
preliminarily release the chemical substance contained in the
housing member and possibly released with lapse of time. Therefore,
if the mask blank is housed and packaged by the use of the mask
blank housing member subjected to the treatment according to this
invention, the outgas of the chemical substance is not released
with lapse of time. Thus, it is possible to prevent the mask blank
having a chemically amplified resist film from being contaminated
by the chemical substance. Therefore, a stable resist performance
is assured even after storage of the mask blank. As a result, upon
manufacture of a mask, a stable resist pattern is formed and a
high-quality transfer mask is obtained with a desired mask
pattern.
[0207] Further, by the use of the treatment of heating the housing
member as the treatment for removing the chemical substance
inhibiting the chemically amplifying effect of the chemically
amplified resist, the effect of this invention can be achieved in a
simple manner.
[0208] Now, the fourth embodiment will be described in conjunction
with specific examples.
Example 4-1
[0209] A halftone film was formed on a quartz substrate (6
inch.times.6 inch) by sputtering. On the halftone film, a resist
film was formed by spin coating to produce a mask blank with a
resist film. As the half tone film, a MoSi metal film was used. As
the resist film, a chemically amplified resist film of a positive
type was used. The resist film was formed in a clean room cleaned
by a combination of an activated carbon filter containing potassium
carbonate, an activated carbon filter containing phosphoric acid,
and an ULPA filter.
[0210] 100 mask blanks were produced in the above-mentioned manner
and housed in 10 containers having the structure illustrated in
FIGS. 1, 2, 4 and 10. As a material of each of the cap, the
container body, and the inner case of the container, PMMA resin was
used. By the use of the PMMA resin, the container was formed into
the structure illustrated in FIGS. 1, 2, 4, and 10. Thereafter, the
container was cleaned with RO/DI water at a temperature of
40.degree. C. After cleaning, the container was heat treated in a
clean oven. The heat treatment was carried out at 50.degree. C. for
30 minutes. Each of the cleaning step and the heat treating step
was carried out in a clean room cleaned by the use of a combination
of an activated carbon filter containing potassium carbonate, an
activated carbon filter containing phosphoric acid, and an ULPA
filter.
[0211] The operation of housing the mask blanks was also carried
out in the clean room cleaned by the above-mentioned activated
carbon filters and the ULPA filter.
[0212] The container was packaged in a package bag and transported
by air cargo. The container after transported was held for about
one month in a packaged state. Thereafter, the container was opened
in a clean room similar to that mentioned above to take out the
mask blanks. Each mask blank was subjected to electron beam
writing, development, and etching in a predetermined manner to
produce a phase-shift transfer mask. The quality of each
phase-shift transfer mask thus produced was inspected in detail by
the use of a scanning electron microscope. As a result, no serious
defect was found in any one of the 100 phase-shift masks. Upon
opening the container, acidic ions and basic ions on the inner
surface of the container were analyzed by ion chromatography. The
result is shown Table 1.
Example 4-2
[0213] Mask blanks were housed, transported, and stored by the use
of the container produced in the manner similar to Example 1 except
that the container was cleaned with RO/DI water kept at 70.degree.
C.
[0214] In the manner similar to Example 1, a phase shift mask was
produced by the use of the mask blank after storage. The quality of
each phase-shift mask thus produced was inspected in detail by the
use of a scanning electron microscope. As a result, no serious
defect was found in any one of the 100 phase-shift masks. The
result of analyzing acidic ions and basic ions on the inner surface
of the container upon opening the container is shown in Table
1.
Example 4-3
[0215] Mask blanks were housed, transported, and stored by the use
of the container produced in the manner similar to Example 1 except
that the container was cleaned with RO water kept at 40.degree.
C.
[0216] In the manner similar to Example 1, a phase shift mask was
produced by the use of the mask blank after storage. The quality of
each phase-shift mask thus produced was inspected in detail by the
use of a scanning electron microscope. As a result, no serious
defect was found in any one of the 100 phase-shift masks The result
of analyzing acidic ions and basic ions on the inner surface of the
container upon opening the container is shown in Table 1.
Comparative Example
[0217] Mask blanks were housed, transported, and stored by the use
of the container produced in the manner similar to Example 1 except
that the container after cleaning was not heat treated but was left
at room temperature.
[0218] In the manner similar to Example 1, a phase shift mask was
produced by the use of the mask blank after storage. The quality of
each phase-shift mask thus produced was inspected in detail by the
use of a scanning electron microscope. As a result, disturbance in
line width of a pattern was observed in each of 100 masks. The
result of analyzing acidic ions and basic ions on the inner surface
of the container upon opening the container is shown in Table
1.
TABLE-US-00001 TABLE 1 (ng/cm.sup.2) Container basic resin heat
acidic ions ions material Cleaning treatment Cl.sup.-
SO.sub.4.sup.2- HPO.sub.3.sup.2- NH.sub.4.sup.+ Example PMMA RO/DI
50.degree. C. not not not not 4-1 Water 30 minutes detected
detected detected detected (40.degree. C.) Example PMMA RO/DI
50.degree. C. not not not not 4-2 Water 30 minutes detected
detected detected detected (70.degree. C.) Example PMMA RO
50.degree. C. 0.8 0.9 not 0.9 4-3 Water 30 minutes detected
(40.degree. C.) Compar- PMMA RO/DI None 4.7 4.5 36 4.5 ative Water
(left at room Example (40.degree. C.) temperature)
[0219] The reason is supposed as follows. As seen from the result
in Table 1, even if the PMMA resin which releases a relatively
small amount of outgas was used, chemical substances, such as an
acidic substance and a basic substance, were released from the
container into the interior of the container while the mask blanks
were housed and stored. The chemically amplified resist film of the
mask blank was chemically contaminated by the chemical substances
released from the container.
[0220] In Examples 4-1 to 4-3 of this embodiment, the container
produced by the use of the heat treatment according to this
invention. Therefore, while the mask blank was housed and stored,
no substantial amount of chemical substance contaminating the
chemically amplified resist film is released from the container. On
the contrary, in Comparative Example without the heat treatment of
this invention, the chemical substance contaminating the chemically
amplified resist film is released from the container while the mask
blank was housed and stored.
[0221] While this invention has thus far been described in
conjunction with the preferred embodiments thereof, it will be
readily possible for those skilled in the art to put this invention
into practice in various other manners without departing from the
scope of this invention.
* * * * *