U.S. patent application number 09/752688 was filed with the patent office on 2001-08-02 for container for framed pellicle.
This patent application is currently assigned to SHIN-ETSU CHEMICAL CO., LTD.. Invention is credited to Shirasaki, Toru.
Application Number | 20010010292 09/752688 |
Document ID | / |
Family ID | 18538469 |
Filed Date | 2001-08-02 |
United States Patent
Application |
20010010292 |
Kind Code |
A1 |
Shirasaki, Toru |
August 2, 2001 |
Container for framed pellicle
Abstract
The invention provides an improvement in a pellicle container
for containing a framed pellicle conventionally made from a plastic
resin, which is mounted on a photolithographic photomask for
dust-proof protection thereof. A serious problem in the plastic
resin-made container is adsorption or deposition of organic matters
emitted from the container body by or on the pellicle membrane
during storage or transportation resulting in a decrease in the
light transmission as well as accelerated degradation of the
pellicle membrane to the light of an extremely short wavelength for
patternwise exposure in the photolithography while this problem can
be solved by the improvement of the invention according to which at
least the surface layer of the container surfaces facing the space
for containing the framed pellicle is formed from an inorganic
material, e.g., metals, glass materials and ceramics, free from
emission of any organic matters.
Inventors: |
Shirasaki, Toru;
(Annaka-shi, JP) |
Correspondence
Address: |
DOUGHERTY & TROXELL
5205 LEESBURG PIKE, SUITE 1404
FALLS CHURCH
VA
22041
US
|
Assignee: |
SHIN-ETSU CHEMICAL CO.,
LTD.
|
Family ID: |
18538469 |
Appl. No.: |
09/752688 |
Filed: |
January 3, 2001 |
Current U.S.
Class: |
206/454 ;
206/455; 206/701; 206/710; 430/4 |
Current CPC
Class: |
G03F 1/64 20130101; G03F
1/66 20130101 |
Class at
Publication: |
206/454 ;
206/455; 206/701; 206/710 |
International
Class: |
B65D 085/48; B65D
085/00; B65D 085/30 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 19, 2000 |
JP |
2000-10450 |
Claims
What is claimed is:
1. In a container for a framed pellicle as an assembly of a
container base and a covering mountable on the container base
jointly to form an inside space for containing a framed pellicle,
the improvement which comprises forming at least the surface layer
of the container base and the covering facing the inside space from
an inorganic material selected from the group consisting of metals
or alloys, glass materials and ceramic materials to form a cladding
layer.
2. The improvement as claimed in claim 1 in which the container
base and the covering of the container are entirely formed from the
inorganic material.
3. The improvement as claimed in claim 1 in which the cladding
layer of an inorganic material is formed only on the surfaces of
the container base and the covering made from a plasyic resin
facing the inside space.
4. The improvement as claimed in claim 1 in which the cladding
layer of an inorganic material is formed both on the surfaces of
the container base and the covering made from a plastic resin
facing the inside space and on the outwardly facing surfaces
thereof.
5. The improvement as claimed in claim 1 in which the cladding
layer of an inorganic material has a thickness of at least 0.1
.mu.m.
6. The improvement as claimed in claim 1 in which the metal or
alloy forming the cladding layer is selected from the group
consisting of aluminum, copper, iron and stainless steels.
7. The improvement as claimed in claim 1 in which the ceramic
material forming the cladding layer is selected from the group
consisting of silicon nitride, silicon carbide, zirconia, alumina
and boron nitride.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a container for a framed
pellicle or, more particularly, to a container for containing a
framed pellicle used for dust-proof protection of a photomask in
the photolithographic patterning works. In particular, the
improvement of the invention is directed to the structure of a
pellicle container for containing a framed pellicle used with an
object of dust-proof protection of a photomask in the patterning
works in the manufacture of fine and precision electronic devices
including semiconductor devices such as LSIs and VLSIs and liquid
crystal display panels.
[0002] Photolithographic patterning is a conventional and
established technology in the manufacturing process of fine and
precision electronic devices including semiconductor devices such
as LSIs and VLSIs and liquid crystal display panels. In the
photolithographic patterning works, the surface of the substrate
for the device is patternwise exposed to actinic rays such as
ultraviolet light through a pattern-bearing transparency called a
photomask. It is very important here that the surface of the
photomask is absolutely free from dust particles deposited thereon
because the quality of patterning is greatly affected adversely by
the dust particles on the photomask due to absorption, scattering
and diffraction of the exposure light. In this regard,
photolithographic patterning works are conducted in a dust-free
atmosphere of a clean room although it is almost impossible to be
absolutely free from dust particles even in a clean room of the
highest class. A usual procedure therefore is that a framed
pellicle for dust-proof protection is mounted on the photomask and
the patterning light-exposure is conducted through the transparent
pellicle membrane of the framed pellicle.
[0003] When the patterning light-exposure is conducted through the
pellicle membrane of a framed pellicle mounted on the photomask,
dust particles deposited on the surface of the pellicle membrane
have no particular adverse effects on the quality of patterning
since the exposure light is focused not at the dust particles but
at the photomask which is at least several millimeters below the
pellicle membrane.
[0004] FIG. 1 of the accompanying drawing illustrates a vertical
cross sectional view of a typical framed pellicle 6 which is an
integral device basically consisting of a square or circular frame
3, referred to as a pellicle frame, of a rigid material and a thin
and highly transparent film 1, referred to as a pellicle membrane,
of a plastic resin spread over one end surface of the pellicle
frame 3 and adhesively bonded thereto in a slack-free fashion with
intervention of an adhesive layer 2 therebetween. The other end
surface of the pellicle frame 3 is usually coated with a
pressure-sensitive adhesive forming a pressure-sensitive adhesive
layer 4 in order to facilitate mounting of the framed pellicle 6 on
the photomask with stability. The surface of the pressure-sensitive
adhesive layer 4 is temporarily protected until use by attaching a
releasable film or sheet 5.
[0005] The plastic resin forming the pellicle membrane 1 is usually
selected from nitrocelluloses, cellulose acetates and fluorocarbon
polymers in view of their good mechanical strengths even in the
form of a thin films and high transparency to the exposure light. A
glass plate is also proposed in place of the pellicle membrane 1 of
a plastic resin. The rigid material forming the pellicle frame 3 is
usually selected from aluminum, stainless steel, polyethylene and
the like. The pellicle membrane 1 is adhesively bonded to one of
the end surfaces of the pellicle frame 3 by using an adhesive 2
which can be an acrylic resin-based adhesive, epoxy resin-based
adhesive or fluorocarbon resin-based adhesive according to the
disclosure in U.S. Pat. No. 4,861,402, Japanese Patent Publication
No. 58-219023, Japanese Patent Kokai No. 7-168345 and elsewhere.
Alternatively, Japanese Patent Kokai No. 58-219023 proposes a
bonding method in which an organic solvent having good dissolving
power to the plastic resin of the pellicle membrane 1 is applied to
the end surface of the pellicle frame 3 followed by partial drying
and the pellicle membrane 1 is brought into contact with the end
surface of the pellicle frame still adequately wet with the
solvent.
[0006] The other end surface of the pellicle frame 3, i.e. the end
surface opposite to the pellicle membrane 1, is usually provided
with a pressure-sensitive adhesive layer 4 by coating with a
suitable pressure-sensitive adhesive based on a polybutene resin,
polyvinyl acetate resin, acrylic resin or silicone resin. The
surface of the pressure-sensitive adhesive layer 4 is temporarily
protected until use of the framed pellicle 6 by attaching a
releasable sheet or separator 5 which is removed by peeling
immediately before the framed pellicle 6 freed from the releasable
sheet 5 is mounted on the photomask by gently pressing against the
photomask. Needless to say, framed pellicles 6 with the above
mentioned releasable sheet 5 are transported and stored as
contained in a rigid container for a framed pellicle 6, which is
conventionally formed from a plastic resin, in order to protect the
same until use against mechanical damages and contamination.
[0007] Turning now to the light for patternwise exposure through
the pellicle membrane 1, it is a remarkable trend in recent years
to be in compliance with the requirement toward a finer and finer
resolution of the photolithographic pattern, the exposure light is
under a continuous shift toward those of shorter and shorter
wavelengths in order to accomplish the high pattern resolution. For
example, the g-line light and l-line light having a wavelength of
436 nm and 365 nm, respectively, which were the major current of
the exposure light, now have been replaced with the deep UV light
of 248 nm wavelength from a KrF excimer laser which in turn is
under replacement with vacuum UV light of 193 nm wavelength from an
ArF excimer laser. It is already foreseen that the UV light of a
still shorter wavelength of 158 nm such as the fluorine excimer
laser beams will be actually employed as the exposure light in
photolithographic patterning.
[0008] It has unexpectedly become apparent that a very serious
problem must be solved in order to conduct the patterning exposure
in photolithography by using the above mentioned extremely
short-wavelength light as the patterning exposure light. Namely, it
is unavoidable that the pellicle membrane 1 made from a plastic
resin more or less adsorbs gaseous hydrocarbon compounds and
moisture from the atmospheric air and these adsorbates have an
effect of decreasing the transmissivity of the pellicle membrane 1
to the exposure light. In addition, these adsorbed gases are
activated by the laser irradiation to form initiation sites for the
degradation reaction of the plastic resin of the pellicle membrane
1 resulting in a decrease in the durability of the framed pellicle
6.
[0009] Since it is usual that the framed pellicles manufactured in
a production line are each contained in a plastic-made container
and stored for a considerable length of time before the product is
transported to the users for actual service, a chance of high
possibility for contacting with the above mentioned contaminant
gases is given during storage of the framed pellicles in
containers. Namely, plastic resins forming the container always
contain, though in a trace amount, various organic compounds such
as the unpolymerized monomer compounds and organic solvents as the
polymerization medium and these organic impurity matters are more
or less emitted from the container walls to be adsorbed by the
pellicle membrane 1 of the framed pellicle 6 contained in the
container and act adversely as described above.
SUMMARY OF THE INVENTION
[0010] The present invention accordingly has an object to provide,
in order to solve the above described problem, a container for a
framed pellicle which is free from emission of any organic matters
which might be adsorbed on the pellicle membrane of a framed
pellicle contained in the container for transportation and/or
storage to exhibit the adverse effects of decreasing the
light-transmissivity and acceleration of degradation of the
pellicle membrane.
[0011] Thus, the present invention provides an improvement in a
container for a framed pellicle as an assembly of a container base
and a covering mountable on the container base jointly to form an
inside space for containing a framed pellicle, which improvement
comprises forming at least the surface layer of the container base
and the covering facing the inside space from an inorganic material
selected from the group consisting of metals, alloys, glass
materials and ceramic materials.
[0012] While the minimum requirement of the present invention is to
form the inner surface layer of the container from an inorganic
material, it is optional that the whole bodies of the container
base and the covering are formed entirely from an inorganic
material or that both of the inner and outer surface layers of the
container are formed from an inorganic material.
BRIEF DESCRIPTION OF THE DRAWING
[0013] FIG. 1 is a schematic vertical cross sectional view of a
framed pellicle.
[0014] FIG. 2 is a schematic vertical cross sectional view of an
inventive container formed entirely from an inorganic material
containing a framed pellicle therein.
[0015] FIG. 3 is a schematic vertical cross sectional view of an
inventive container of which both of the inner and outer surface
layers are formed from an inorganic material containing a framed
pellicle therein.
[0016] FIG. 4 is a schematic vertical cross sectional view of an
inventive container of which the inner surface layer only is formed
from an inorganic material containing a framed pellicle
therein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] As is illustrated in FIG. 2, the container 7 of the present
invention is an assembly composed of a container base 7A and a
covering 7B mountable on the container base 7A. When the covering
7B is mounted on the container base 7A in place, an inside space 7C
is formed to contain the framed pellicle 6.
[0018] The most characteristic feature of the inventive container 7
for a framed pellicle is that at least the surface layer of the
container 7, i.e. container base 7A and covering 7B, facing the
inside space 7C is formed from an inorganic material which can be a
metal or alloy, glass material or ceramic material. Examples of the
metal and alloy suitable for the purpose include aluminum, copper,
iron and stainless steels. The surface of the layers of these
metallic materials can be subjected to a variety of surface
treatments with an object to improve stability and corrosion
resistance. For example, it is optional that the surface of an
aluminum layer is subjected to an anodization treatment to form an
oxidized thin film thereon. The glass material is not particularly
limitative including fused silica glass. The ceramic material used
here is exemplified by silicon nitride, silicon carbide, zirconia,
alumina, boron nitride and the like.
[0019] Instead of forming the entire body of the container 7 from
the above mentioned inorganic material as is illustrated in FIG. 2,
it is optional that the walls of the container have a composite
layered structure consisting of a core 8A or 8B made from a
conventional plastic resin and cladding layers 9, 10 of an
inorganic material on the outer and inner surfaces, respectively,
of the cores 8A, 8B as is illustrated in FIG. 3 by a vertical cross
sectional view containing a framed pellicle 6 in the inside space.
It is of course that the cladding layers 10 of an inorganic
material on the outer surface of the container base and covering
are not essential and can be omitted as is illustrated in FIG. 4 by
a vertical cross sectional view containing a framed pellicle 6.
Namely, the inorganic cladding layer 10 is formed only on the
surfaces of the container base 8A and covering 8B of a plastic
resin facing the inside space 7C to contain the framed pellicle
6.
[0020] The inorganic cladding layers 10 on the inner surfaces of
the cores 8A, 8B of the container should desirably have a thickness
of at least 0.1 .mu.m. When the thickness is too small, the
inorganic cladding layers are eventually subject to the formation
of cracks or fissures so that emission of organic contaminant gases
from the cores 8A, 8B of a plastic resin cannot be completely
prevented. The method for forming the inorganic cladding layers 10
on the surfaces of the cores 8A, 8B is not particularly limitative
depending on the kind of the inorganic materials and desired
thickness of the cladding layers 10. For example, the inorganic
cladding layers 10 can be formed by the vacuum vapor deposition
method or, alternatively, by adhesively bonding a thin sheet of the
inorganic material by using an adhesive.
[0021] Following is a description of the present invention in more
detail by way of Examples and a Comparative Example making
reference to the accompanying drawing, which is preceded by the
description of the preparation procedure of framed pellicles to be
contained in the container.
[0022] Thus, a framed pellicle 6A was prepared by adhesively
bonding a glass sheet of 1 mm thickness to serve as the pellicle
membrane onto one of the end surfaces of an aluminum-made pellicle
frame coated with a silicone resin-based adhesive while the other
end surface of the pellicle frame was coated with a silicone
resin-based pressure-sensitive adhesive in a thickness of 0.5 mm
and the pressure-sensitive adhesive layer was protected by
attaching a releasable film.
[0023] Another framed pellicle 6B was prepared in about the same
manner as above excepting for the replacement of the 1 mm thick
glass sheet with a 0.5 .mu.m thick film of a fluorocarbon resin
which was spread over and adhesively bonded to the adhesive-coated
end surface of the pellicle frame in a slack-free fashion.
[0024] The pellicle membranes of the framed pellicles 6A, 6B had
transmissions of 80% and 90%, respectively, to the fluorine excimer
laser beams of 158 nm wavelength. In the Examples and Comparative
Example shown below, these framed pellicles were kept for a length
of time in several different pellicle containers and measurements
were made for the transmission of the pellicle membranes after
storage to the fluorine excimer laser beams.
EXAMPLE 1
[0025] The framed pellicles 6A, 6B prepared as above were each kept
in a pellicle container entirely made of aluminum for 1 month at
room temperature. The framed pellicles 6A, 6B taken out of the
respective pellicle containers were subjected to the transmission
measurement of the fluorine excimer laser beams to give values of
80% and 90%, respectively, showing no decrease as a consequence of
storage.
EXAMPLE 2
[0026] The experimental procedure was substantially the same as in
Example 1 excepting for the replacement of the aluminum-made
pellicle containers with containers entirely made from fused silica
glass. The transmission values of the pellicle membranes of the
framed pellicles 6A, 6B after 1 month storage therein were 80% and
90%, respectively, to the fluorine excimer laser beams showing no
decrease as a consequence of storage.
EXAMPLE 3
[0027] The experimental procedure was substantially the same as in
Example 1 excepting for the replacement of the aluminum-made
pellicle containers with containers made from an ABS resin and
provided with a 0.1 .mu.m thick cladding layers of aluminum formed
by the method of vacuum vapor deposition on the overall surfaces of
the container base and covering. The transmission values of the
pellicle membranes of the framed pellicles 6A, 6B after 1 month
storage therein were 80% and 90%, respectively, to the fluorine
excimer laser beams showing no decrease as a consequence of
storage.
EXAMPLE 4
[0028] The experimental procedure was substantially the same as in
Example 3 except that the 0.1 .mu.m thick cladding layers of
aluminum were formed only on the inward surfaces of the ABS
resin-made container base and covering facing the inside space for
containing the framed pellicle. The transmission values of the
pellicle membranes of the framed pellicles 6A, 6B after 1 month
storage therein were 80% and 90%, respectively, to the fluorine
excimer laser beams showing no decrease as a consequence of
storage.
EXAMPLE 5
[0029] The experimental procedure was substantially the same as in
Example 3 except that the cladding layers on the surfaces of the
container base and covering had a double-layered structure
consisting of a 0.5 .mu.m thick undercladding layer of aluminum and
0.5 .mu.m thick top cladding layer of boron nitride each formed by
the method of vacuum vapor deposition. The transmission values of
the pellicle membranes of the framed pellicles 6A, 6B after 1 month
storage therein were 80% and 90%, respectively, to the fluorine
excimer laser beams showing no decrease as a consequence of
storage.
Comparative Example
[0030] The experimental procedure was substantially the same as in
Example 1 excepting for the replacement of the aluminum-made
pellicle containers with containers made from a polymethyl
methacrylate resin having no inorganic cladding layers thereon. The
transmission values of the pellicle membranes of the framed
pellicles 6A, 6B after 1 month storage therein were 47% and 50%,
respectively, to the fluorine excimer laser beams showing
remarkable decreases as a consequence of storage.
* * * * *