U.S. patent application number 09/757715 was filed with the patent office on 2002-07-11 for containers for lithography mask and method of use.
Invention is credited to Guo, Cheng.
Application Number | 20020089656 09/757715 |
Document ID | / |
Family ID | 25048912 |
Filed Date | 2002-07-11 |
United States Patent
Application |
20020089656 |
Kind Code |
A1 |
Guo, Cheng |
July 11, 2002 |
Containers for lithography mask and method of use
Abstract
A container is provided for storing a lithographic printing
mask. A first container section is formed of a sturdy material
which defines a central inner recess area that is shaped to house a
mask and to hold outer edges of a mask without touching a pattern
on the mask. A second identical container section is placed against
the first container section with a mask housed within recesses of
both to form a container which has a common pressure level all
around and therein. A higher pressure level is then applied outside
the container causes the first and second sections of the container
to be held together. To remove the mask from the container, the
pressure outside the container is reduced to substantially the
pressure level inside the container and the first and second
sections are pulled apart.
Inventors: |
Guo, Cheng; (New Providence,
NJ) |
Correspondence
Address: |
Patent Counsel, MS/2061
Legal Affairs Dept.
Applied Materials, Inc.
3050 Bowers Avenue
Santa Clara
CA
95054
US
|
Family ID: |
25048912 |
Appl. No.: |
09/757715 |
Filed: |
January 9, 2001 |
Current U.S.
Class: |
355/75 ; 355/30;
355/53; 355/72; 355/77; 430/5; 435/5 |
Current CPC
Class: |
G03F 7/70741 20130101;
G03B 27/62 20130101; G03F 1/66 20130101 |
Class at
Publication: |
355/75 ; 355/72;
355/53; 355/77; 435/5; 355/30 |
International
Class: |
G03B 027/62 |
Claims
What is claimed is:
1. A container for housing a lithographic mask comprising: a first
section; and a second section in contact with the first section
with the contacting first and second sections defining a cavity
having a size which is sufficient to house a lithographic mask and
provide an air tight seal around the cavity when pressure within
the cavity is less than pressure outside the container such that
dust and other particles cannot reach a lithographic mask housed in
the cavity.
2. A container for storing a lithographic printing mask comprising:
a first container section formed of a sturdy material; and a second
container section formed of a sturdy material, wherein when the
first and second container sections are placed together they define
a cavity therein having a size to fixedly house a mask while not
contacting a mask pattern on the mask and provide an air tight seal
around the cavity when pressure within the cavity is less than
pressure outside the container such that dust and other particles
cannot reach the mask housed in the cavity.
3. The container of claim 2 further comprising a compressible
material located on a surface of at least one of the first and
second container sections where they come together and surrounding
the cavity defined by the first and second container sections for
providing the air tight seal.
4. The container of claim 3 wherein the compressible material is an
O-ring.
5. The container of claim 3 wherein the compressible material is a
layer of a compressible material.
6. The container of claim 2 wherein the first and second container
sections are formed from a material from one of a group consisting
of metal, plastic, and a sturdy composition material.
7. The container of claim 2 wherein a clean mask is placed in the
cavity of a cleaned first container section in a clean vacuum
chamber at a predetermined first pressure level, a cleaned second
container section is aligned with the first container section and
is placed in contact with the first container section, and the
first pressure level in the vacuum chamber is raised to a second
higher pressure level to seal and hold the sealed first and second
container sections together.
8. A container for storing a lithographic printing mask comprising:
a first container section formed of a sturdy material and defining
a first cavity which is shaped for contacting an edge section of a
mask to be stored in the container and covers, but does not contact
an area of a mask pattern on the mask when the edge section of the
mask is placed in the cavity; a second container section formed
from a sturdy material and defining a second cavity therein having
a size which contacts an edge section of a mask to be stored in the
container wherein when the first and second container sections are
placed together they fixedly house the mask in the first and second
cavities and provide an air tight seal around the cavity when
pressure within the first and second cavities is less than pressure
outside the container such that dust and other particles cannot
reach the mask housed in the cavity.
9. A container for storing a lithographic printing mask comprising:
a first container section formed of a sturdy material and defining
a first cavity which is shaped for contacting an edge section of a
mask to be stored in the container and covers, but does not contact
an area of a mask pattern on the mask when the edge section of the
mask is placed in the cavity; a second container section formed
from a sturdy material and defining a second cavity therein having
a size which contacts an edge section of a mask to be stored in the
container wherein when the first and second container sections are
placed together they fixedly house the mask in the first and second
cavities and provide an air tight seal around the cavity when
pressure within the first and second cavities is less than pressure
outside the container such that dust and other particles cannot
reach the mask housed in the cavity.
10. The container of claim 9 further comprising a compressible
material located on a surface of at least one of the first and
second container sections where they come together and surrounding
the first and second cavities defined by the first and second
container sections, respectively, for providing the air tight
seal.
11. The container of claim 10 wherein the compressible material is
an O-ring.
12. The container of claim 9 wherein the compressible material is a
thin layer of a compressible material.
13. The container of claim 9 wherein the first and second container
sections are formed from a material selected from a group
consisting of metal, plastic, and a sturdy composition
material.
14. The container of claim 9 wherein a clean mask is placed in the
cavity of a cleaned first container section in a clean vacuum
chamber at a predetermined first pressure level, a cleaned second
container section is aligned with the first container section and
is placed in contact with the first container section, and the
first pressure level in the vacuum chamber is raised to second
higher pressure level to seal and hold the sealed first and second
container sections together.
15. A method of storing a mask in a container comprising first and
second sections which are both cleaned to remove particles thereon,
the method comprising the steps of: placing first and second
cleaned sections of the container and a cleaned mask in a chamber
and reducing the pressure within the chamber to a first pressure
level; while the mask is in the chamber which is at the first
pressure level, placing the mask in a cavity defined by portions of
the first container section such that a mask pattern on the mask
does not contact any portion of the first container; while the mask
is in the cavity, placing the second container section in contact
with the first container section to form the container and to seal
the cavity therein from dust and particles and any pressure changes
outside the container; and raising the first pressure level
surrounding the container to a second higher pressure level to seal
and hold the first and second container sections together.
16. The method of claim 15 wherein a compressible material is
located on a surface of at least one of the first and second
container sections where they come together and surrounds the
cavity defined by the first and second container sections for
providing the air tight seal.
17. The method of claim 16 wherein the compressible material is an
O-ring.
18. The method of claim 16 wherein the compressible material is a
thin layer of a compressible material.
19. The method of claim 15 wherein the first and second container
sections are formed from a material selected from a group
consisting of metal, plastic, and any sturdy composition
material.
20. The method of claim 15 wherein the first pressure level is
below normal atmospheric pressure and the second pressure level is
atmospheric pressure.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a container useful for holding
(storing) mask, e.g., a Next Generation Lithography (NGL) mask, and
preventing dust or other particles from reaching the mask, and to a
method of using the container.
BACKGROUND OF THE INVENTION
[0002] Keeping a mask used in the fabrication of integrated
circuits clean is critical. Dust or other particles on a mask can
cause corresponding spots to be formed on the substrate of an
integrated circuit being formed when the mask is illuminated. Such
spots will produce an inaccurate reproduction of the mask on the
substrate and thereby can reduce yield.
[0003] In prior art optical projection printing systems, light is
generally projected from a light source through a lens arrangement
and then a mask having a predetermined pattern formed thereon that
is stored in a pellicle. The image projected from the mask is
incident on a substrate having a light sensitive layer, e.g.,
photoresist, formed on a surface thereof. In this regard, see, for
example, U.S. Pat. No. 4,131,363 (Shea et al.), issued on Dec. 26,
1978. The pellicle in such printing systems generally comprises a
solid frame for holding a mask, and a transparent thin film that
covers an upper opening of the frame. To print a mask pattern, the
substrate and the mask within the pellicle are cleaned to remove
any dust or particles thereon, and the bottom of the pellicle frame
is securely mounted above the substrate around a light sensitive
layer thereon to be irradiated. The pattern on the mask within the
pellicle is then irradiated to transfer the pattern of the mask
onto the light sensitive layer on the substrate. Generally, dust or
other particles on the transparent thin film stretched over the
pellicle frame is of no concern. This is because the film is
positioned a sufficient distance above the mask so that dust or
other particles on the film are out of focus when the surface of
the substrate is irradiated through the mask with the type of
radiation (e.g., Ultraviolet (UV), deep UV, or X-ray radiation)
used in the prior art systems. Therefore, such dust or other
particles on the surface of the pellicle itself do not affect the
printed pattern on the substrate.
[0004] Pellicles used in the prior art photolithography systems are
generally secured to the substrate by various techniques such as
using an adhesive, vacuum chucking techniques, magnets, and spring
loading arrangements to protect the mask area from dust or other
particles. In this regard see, for example, U.S. Pat. No. 4,833,051
(Imamura), issued on May 23, 1989. Prior art pellicles also have
included various passageways through the sides of the pellicle
frame for equalizing atmospheric pressure changes that occur
between the protected area within the pellicle and outside of the
pellicle while still protecting the protected area within the
pellicle from dust or particles. Such passageway arrangements
prevent the thin film covering the frame of the pellicle from
deforming and contacting the surface of the mask when the pellicle
is transported via different altitudes and/or environments. These
passageways in the pellicle frame can include serpentine channels
or a straight through passageway with filters mounted therein. In
this regard see, for example, the Imamura patent cited above, and
U.S. Pat. No. 6,055,040 (Sego), issued on Apr. 25, 2000.
[0005] For all Next Generation Lithography (NGL) systems where a
narrow beam of radiation is used as, for example, electron beam
printing technology, keeping a mask clean is critical. However,
known pellicle materials are not transparent enough to radiation,
e.g., electron beams and extreme ultraviolet radiation, used with
NGL systems.
[0006] It is desirable to provide a container for holding a mask
that is to be used with NGL systems during transportation, storage,
etc. to keep dust and/or particles from depositing on the mask. The
design of the container should also reduce the chance of dust
and/or particle being deposited on a mask during mask loading and
unloading into and out of the container.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to a container and use
thereof for temporarily storing a Next Generation Lithography (NGL)
mask in order to keep such a mask clean prior to it being used
with, for example, electron beam printing technology.
[0008] A first apparatus aspect of the present invention is a
container for housing a lithographic mask. The apparatus comprises
a first section and a second section. The second section is in
contact with the first section with the contacting first and second
sections defining a cavity having a size which is sufficient to
house a lithographic mask and provide an air tight seal around the
cavity when pressure within the cavity is less than pressure
outside the container such that dust and other particles cannot
reach a lithographic mask housed in the cavity.
[0009] A second apparatus aspect of the present invention is a
container for storing a lithographic printing mask. The container
comprises a first container section formed of a sturdy material and
a second container section formed of a sturdy material. When the
first and second container sections are placed together they define
a cavity therein having a size to fixedly house a mask while not
contacting a mask pattern on the mask and provide an air tight seal
around the cavity when pressure within the cavity is less than
pressure outside the container such that dust and other particles
cannot reach the mask housed in the cavity.
[0010] A third apparatus aspect of the present invention is a
container for storing a lithographic printing mask. The container
comprises first and second sections. The first container section is
formed of a sturdy material and defines a first cavity which is
shaped for contacting an edge section of a mask to be stored in the
container and covers, but does not contact an area of a mask
pattern on the mask when the edge section of the mask is placed in
the cavity. The second container section is formed from a sturdy
material and defines a second cavity therein having a size which
contacts an edge section of a mask to be stored in the container
wherein when the first and second container sections are placed
together they fixedly house the mask in the first and second
cavities and provide an air tight seal around the cavity when
pressure within the first and second cavities is less than pressure
outside the container such that dust and other particles cannot
reach the mask housed in the cavity.
[0011] A fourth apparatus aspect of the present invention is a
container for storing a lithographic printing mask.
[0012] The container comprises first and second container sections.
The first container section is formed of a sturdy material and
defines a first cavity which is shaped for contacting an edge
section of a mask to be stored in the container and covers, but
does not contact an area of a mask pattern on the mask when the
edge section of the mask is placed in the cavity. The second
container section is formed from a sturdy material and defines a
second cavity therein having a size which contacts an edge section
of a mask to be stored in the container wherein when the first and
second container sections are placed together they fixedly house
the mask in the first and second cavities and provide an air tight
seal around the cavity when pressure within the first and second
cavities is less than pressure outside the container such that dust
and other particles cannot reach the mask housed in the cavity.
[0013] A method aspect of the present invention is a method of
storing a mask in a container comprising first and second sections
which are both cleaned to remove particles thereon. The method
comprising the steps of: placing first and second cleaned sections
of the container and a cleaned mask in a chamber and reducing the
pressure within the chamber to a first pressure level; while the
mask is in the chamber which is at the first pressure level,
placing the mask in a cavity defined by portions of the first
container section such that a mask pattern on the mask does not
contact any portion of the first container; while the mask is in
the cavity, placing the second container section in contact with
the first container section to form the container and to seal the
cavity therein from dust and particles and any pressure changes
outside the container; and raising the first pressure level
surrounding the container to a second higher pressure level to seal
and hold the first and second container sections together.
[0014] The invention will be better understood from the following
more detailed description taken with the accompanying drawing and
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 shows a cross-sectional side view of a container with
a Next Generation Lithography (NGL) mask stored (housed) therein in
accordance with the present invention;
[0016] FIG. 2 shows a cross-sectional schematic view of a vacuum
chamber with the container (shown in perspective view) of FIG. 1
housing a NGL mask in accordance with the present invention;
and
[0017] FIG. 3 shows a cross-sectional side view of an other
container with NGL mask stored (housed) therein in accordance with
the present invention.
[0018] The drawings are not necessarily to scale.
DETAILED DESCRIPTION OF THE INVENTION
[0019] It is to be understood that corresponding elements having
the same function in the several views of the drawings are provided
with the same designation numbers.
[0020] Referring now to the FIG. 1, there is shown a
cross-sectional side view of a container 10 for storing (housing) a
mask 12 in accordance with the present invention. The container 10
is particularly suited for housing (storing) a mask 12 of the type
used in Next Generation Lithography (NGL) systems including
electron beam lithography and may be used for housing conventional
lithographic masks. The storage container 10 comprises an upper
half 14 and a lower half 16. In a preferred embodiment the halves
14 and 16 are identical. The upper half 14 and the lower half 16 of
the storage container 10 are formed of a sturdy material such as,
for example, a metal, plastic, or other sturdy composition material
(i.e., a material capable of esentially not deforming with a vacuum
applied to portions thereof). Each of the upper and lower halves 14
and 16 defines first and second inner recess sections (cavities)
18a and 18b in a portion of the first and second halves 14 and 16
when the two halves 14 and 16 are placed together. The first inner
recess section (cavity) 18a is formed around an outside edge of the
overall inner recess area for contacting and holding edge portions
of the mask 12 when it is stored therein. The second inner recess
section (cavity) 18b, which is deeper than the first inner recess
section 18a, is in a central area of the overall inner recess area
so that it does not contact, and is over the area of the mask 12
where a mask pattern is actually found. A compressible O-Ring 19 is
positioned around a surface 15 of one of the upper and lower halves
14 and 16 where the halves 14 and 16 where the upper and lower
halves 14 and 16 come together to prevent air leakage into the
first and second inner recess section 18a and 18b when the
container 10 is subsequently vacuum sealed with a mask 12 stored
therein. The compressible material can comprise any suitable
material such as, rubber, which will seal the first and second
inner recesses 18a and 18b. Optionally, small channels (not shown)
can be formed in both the upper and lowers halves 14 and 16 of
container 10. These channels are in communication with each other
at least one location where the upper and lower halves 14 and 16
contact each other so as to help ensure that pressures in recesses
18b of both halves are equal.
[0021] Referring now to FIG. 2, there is shown a perspective view
of a vacuum chamber 26 with the container 10 of FIG. 1 therein. To
mount a mask 12 in the container 10, the first and second halves
are separated and placed within the vacuum chamber 26 (shown within
a dashed line rectangle) which is dust and particle free. A
selectively operated vacuum source (not shown) reduces the pressure
in the chamber 26 to a predetermined vacuum level via a port 28.
The surfaces of the mask 12 and especially the inner recess areas
18a and 18b are then cleaned to make sure that no dust or particles
remain thereon. The mask 12 is then placed in the inner recess
section 18a of the second half 16 of the container 10, and the
first half of the container 10 is symmetrically placed onto the
second half 16 and in contact with the O-ring 19. At his point in
time, the predetermined pressure (vacuum) level in the chamber 26
is the same inside the first and second inner recess areas 18a and
18b and outside the container 10 The pressure in the chamber 26 is
then increased to atmospheric pressure outside of the chamber 26.
The pressure outside the container 10 is now greater than the
pressure level inside the first and second inner recess sections
18a and 18b. This holds the first and second halves together.
Additionally, the O-ring 19 is compressed by the holding force of
the vacuum in the first and second inner recesses 18a and 18b to
prevent air from leaking into the first and second inner recess
sections 18a and 18b. The container 10 storing (housing) a mask 12
can then be then removed from the chamber 26 and shipped to where
it will be used.
[0022] In use, a container 10 housing a mask 12 is placed in a
clean chamber 26 where a lithographic machine (not shown) is
located. The pressure in the chamber 26 is reduced to the
predetermined vacuum level so that the container 10 can be opened,
i.e., the sections 14 and 16 can be separated. Once the container
10 in opened in the clean chamber 26, the mask 12 is removed from
the container 10 and transferred for use in the lithographic
machine to print a plurality of circuit substrates (not shown). It
is to be noted that the upper 14 and lower 16 halves are not
connected together at all by a hinge or other type of coupling
device. This means that there are no surfaces that rub against each
other when the two halves 14 and 16 are separated. Accordingly,
there are no particles formed from a coupling device that can fall
onto the mask 12 stored in the container 10 of FIG. 1 or the
container 10a of FIG. 2.
[0023] Referring now to FIG. 3, there is shown a cross-sectional
side view of a container 10a for storing (housing) a mask 12 in
accordance with the present invention. The container 10a is similar
to the container 10 of FIG. 1 but comprises a different outside
configuration without extra protrusions, and has a somewhat
different internal recess configuration. The storage container 10a
comprises an upper half 14a and a lower half 16a which have a
rectangular shape. Each of the upper and lower halves 14a and 16a
defines first and second inner recess sections 18aa and 18bb in a
portion thereof when the two halves 14a and 16a are placed
together. The first inner recess section 18aa is formed around an
outside edge of the overall inner recess area for contacting and
holding edge portions of the mask 12 when the mask 12 is stored in
the upper and lower halves 14a and 16a. This avoids movement of the
mask 12 during any movement of the container 10a which can cause
the possible release of particles from the rubbing of the mask 12
with the container 10a. The second inner recess section 18bb, which
is deeper than the first inner recess section 18aa, is in a central
portion of the overall inner recess area so that it does not
contact and is over the area of the mask 12 where a mask pattern
(not shown) is actually found.
[0024] A layer of a compressible material 20 is positioned around
the circumference of the container 10a outside the first inner
recess section 18aa where the upper and lower halves 14a and 16a
come together to prevent air leakage into the first and second
inner recess section 18aa and 18bb when the container is
subsequently vacuum sealed with a mask 12 stored therein. The upper
half 14a and the lower half 16a of the container 10a are formed of
a sturdy material such as, for example, a metal, plastic, or other
sturdy composite material and define first and second inner recess
sections 18aa and 18bb when the two halves 14a and 16a are placed
together. The recess section 18aa is formed around the recess
section 18bb and is sized to hold edge portions of the mask 12 when
it is stored therein. The inner recess section 18aa is sized such
that it does not contact the area of the mask 12 where the mask
pattern is actually found. The layer of a compressible material 20
is positioned around a surface 15a of at least one of the upper and
lower halves 14a and 16a where the halves 14a and 16a come together
to prevent air leakage into the first and second inner recess
sections 18aa and 18bb when the container 10a is subsequently
vacuum sealed with a mask 12 therein. The compressible material 20
can comprise any suitable material such as, rubber, which will seal
the first and second inner recesses 18aa and 18bb.
[0025] The mask 12 can be inserted and removed from container 10a
using the vacuum chamber 26 of FIG. 2 in essentially the same
manner as container 10 of FIG. 1 has a mask 12 inserted and then
removed therefrom.
[0026] It is to be appreciated and understood that the specific
embodiment of the invention described hereinbefore are merely
illustrative of the general principles of the invention. Various
modifications may be made by those skilled in the art which are
consistent with the principles set forth. More particularly, the
first and second halves 14, 14a and 16, 16a can have any other
shape as, for example, a rectangular outside shape with or without
external protrusions from that shown in FIGS. 1-3.
* * * * *