U.S. patent application number 11/032591 was filed with the patent office on 2005-06-02 for fresh air ducts including downstream filters for clean rooms.
Invention is credited to Hwang, Jung-Sung, Im, Suk-Hee, Lim, Chang-Su.
Application Number | 20050115213 11/032591 |
Document ID | / |
Family ID | 29997478 |
Filed Date | 2005-06-02 |
United States Patent
Application |
20050115213 |
Kind Code |
A1 |
Lim, Chang-Su ; et
al. |
June 2, 2005 |
Fresh air ducts including downstream filters for clean rooms
Abstract
A fresh air duct is configured to direct fresh air filtered by
an air conditioning system towards a clean room downstream from the
fresh air duct, the fresh air having a first level of particle
density. A separate particle filter in the fresh air duct, located
downstream from the air conditioning system and upstream from the
clean room, is configured to further filter the fresh air to
provide filtered fresh air having a second level of particle
density therein that is less than the first level. Related methods
are also disclosed.
Inventors: |
Lim, Chang-Su; (Kyunggki-do,
KR) ; Im, Suk-Hee; (Kyunggi-do, KR) ; Hwang,
Jung-Sung; (Kyunggi-do, KR) |
Correspondence
Address: |
MYERS BIGEL SIBLEY & SAJOVEC
PO BOX 37428
RALEIGH
NC
27627
US
|
Family ID: |
29997478 |
Appl. No.: |
11/032591 |
Filed: |
January 10, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11032591 |
Jan 10, 2005 |
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10272319 |
Oct 16, 2002 |
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6849100 |
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Current U.S.
Class: |
55/385.2 |
Current CPC
Class: |
F24F 3/167 20210101;
B01D 50/00 20130101 |
Class at
Publication: |
055/385.2 |
International
Class: |
B01D 050/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 6, 2002 |
KR |
2002-39160 |
Claims
What is claimed:
1. An apparatus for providing fresh air to a clean room,
comprising: a fresh air duct configured to direct fresh air
filtered by an air conditioning system towards a clean room
downstream from the fresh air duct, the fresh air having a first
level of particle density; and a separate particle filter in the
fresh air duct, downstream from the air conditioning system and
upstream from the clean room, configured to further filter the
fresh air to provide filtered fresh air having a second level of
particle density therein that is less than the first level.
2. An apparatus according to claim 1 wherein the separate particle
filter is directly in the fresh air duct.
3. An apparatus according to claim 1 wherein the fresh air duct is
configured to receive fresh air only from the air conditioning
system.
4. An apparatus according to claim 1 wherein the air conditioning
system accepts external air having a third level of particle
density that is greater than the first and second levels and is in
a range between about 473.mu./m.sup.3 and about 999
.mu.g/m.sup.3.
5. An apparatus according to claim 1 wherein the separate particle
filter is in an outlet section of the fresh air duct adjacent the
clean room.
6. An apparatus according to claim 1 wherein the separate particle
filter comprises at least one of an HEPA filter configured to
filter at least about 99.97% of particles about 0.3 .mu.m in size
from the fresh air generated by the air conditioning system, an
ULPA filter configured to filter at least about 99.99% of particles
about 0.1 .mu.m to about 0.17 .mu.m in size from the fresh air
generated by the air conditioning system, and an ozone filter.
7. An apparatus according to claim 6 wherein the separate particle
filter comprises a first filter, the apparatus further comprising:
a second filter downstream from the first filter and upstream from
the clean room, wherein the second filter comprises at least one of
an HEPA filter configured to filter about 99.97% of particles about
0.3 .mu.m in size from the fresh air generated by the air
conditioning system, an ULPA filter configured to filter about
99.99% of particles about 0.1 .mu.m to about 0.17 .mu.m in size
from the fresh air generated by the air conditioning system, a
chemical filter and an ozone filter.
8. An apparatus according to claim 7 wherein the second filter is
located in an outlet section of the fresh air duct adjacent to the
clean room.
9. An apparatus according to claim 1 wherein the separate particle
filter comprises a detachable filter and wherein the fresh air duct
further comprises: a first portion of the fresh air duct configured
to direct fresh air from an input of the fresh air duct to an
output of the first portion; and a second portion of the fresh air
duct releaseably coupled to the output of the first portion and
configured to direct fresh air from the output of the first portion
along a pathway through the second portion, wherein the detachable
filter is in the second portion of the fresh air duct.
10. An apparatus according to claim 9 wherein the filter is located
adjacent to an input of the second portion of the fresh air
duct.
11. An apparatus according to claim 9 wherein the first portion
further comprises: a flexible section configured to allow the first
portion of the fresh air duct to move away from an input of the
second portion of the fresh air duct to expose the detachable
filter.
12. An apparatus for providing fresh air to a clean room,
comprising: a fresh air duct downstream from an air conditioning
system configured to direct fresh air filtered by the air
conditioning system to a clean room; and a detachable filter, in
the fresh air duct, configured to filter the fresh air to provide
filtered fresh air downstream of the detachable filter.
13. An apparatus according to claim 12 wherein the detachable
particle filter is directly in the fresh air duct.
14. An apparatus according to claim 12 wherein the fresh air duct
is configured to receive fresh air only from the air conditioning
system.
15. An apparatus according to claim 12 wherein the fresh air duct
comprises: a first portion of the fresh air duct configured to
direct air from an input of the fresh air duct to an output of the
first portion; and a second portion of the fresh air duct
releaseably coupled to the output of the first portion and
configured to direct air from the output of the first portion along
a pathway through the second portion, wherein the detachable filter
is in the second portion of the fresh air duct.
16. An apparatus according to claim 12 wherein the detachable
filter is inside the clean room.
17. An apparatus according to claim 15 wherein the detachable
filter is located in the second portion adjacent to an input
thereto.
18. An apparatus according to claim 15 wherein the first portion
further comprises: a flexible section configured to allow the first
portion of the fresh air duct to move away from the input of the
second portion of the fresh air duct to expose the detachable
filter.
19. An apparatus according to claim 15 wherein the detachable
filter comprises an HEPA filter, an ULPA filter, a chemical filter,
or an ozone filter.
20. A clean room fresh air supply system comprising: an air
conditioning system configured to accept external air and provide
fresh air therefrom filtered by the air conditioning system
downstream to a clean room, the fresh air having a first level of
particle density; a fresh air duct downstream from the air
conditioning system and configured to conduct the fresh air along a
pathway therein; a first filter downstream from the air
conditioning system in the fresh air duct and upstream from the
clean room, configured to filter the fresh air to provide fresh air
having a second level of particle density that is less than the
first level; and a second filter in the fresh air duct downstream
from the first filter configured to further filter the fresh air
having the second level of particle density.
21. An apparatus according to claim 20 wherein the first filter is
directly in the fresh air duct.
22. An apparatus according to claim 20 wherein the fresh air duct
is configured to receive fresh air only from the air conditioning
system.
23. An apparatus according to claim 20 wherein the first filter
comprises at least one of an HEPA filter configured to filter at
least about 99.97% of particles about 0.3 .mu.m in size from the
fresh air generated by the air conditioning system, an ULPA filter
configured to filter at least about 99.99% of particles about 0.1
.mu.m to about 0.17 .mu.m in size from the fresh air generated by
the air conditioning system, and an ozone filter.
24. An apparatus according to claim 23 wherein the second filter
comprises at least one of an HEPA filter configured to filter at
least about 99.97% of particles about 0.3 .mu.m in size from the
fresh air, an ULPA filter configured to filter at least about
99.99% of particles about 0.1 .mu.m to about 0.17 .mu.m in size
from the fresh air, a chemical filter, and an ozone filter.
25. An apparatus according to claim 20 wherein the air conditioning
system accepts external air having a third level of particle
density that is greater than the first and second levels and is in
a range between about 473 .mu.g/m.sup.3 and about 999
.mu.g/m.sup.3.
26. An apparatus according to claim 20 wherein the first filter
comprises a detachable filter, wherein the fresh air duct
comprises: a first portion of the fresh air duct configured to
direct air from an input of the fresh air duct to an output of the
first portion; a second portion of the fresh air duct releaseably
coupled to the output of the first portion and configured to direct
air from the output of the first portion along a pathway through
the second portion, wherein the detachable filter is in the second
portion of the fresh air duct.
27. An apparatus according to claim 26 wherein the first filter is
located adjacent to an input of the second portion of the fresh air
duct.
28. An apparatus according to claim 26 wherein the first portion
further comprises: a flexible section configured to allow the first
portion of the fresh air duct to move away from the input of the
second portion of the fresh air duct to expose the detachable
filter.
29. An apparatus for providing fresh air to a clean room,
comprising: a fresh air duct configured to direct fresh air
filtered by an air conditioning system towards a clean room
downstream from the fresh air duct; and a separate particle filter
in the fresh air duct, downstream from the air conditioning system
and upstream from the clean room, configured to further filter
particles having a predetermined size from the fresh air.
30. An apparatus for providing fresh air to a clean room,
comprising: a fresh air duct configured to direct fresh air
filtered by an air conditioning system towards a clean room
downstream from the fresh air duct, the fresh air duct configured
to hold at least one of a plurality of interchangeable filters
downstream from the air conditioning system and upstream from the
clean room to provide different types of filtration.
31. An apparatus according to claim 30 wherein at least one of the
plurality of interchangeable filters comprises a particle filter
configured to filter particles having a predetermined size from the
fresh air.
32. An apparatus according to claim 30 wherein at least one of the
plurality of interchangeable filters comprises a chemical filter
configured to filter chemical contaminants from the fresh air.
Description
CLAIM FOR PRIORITY AND REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation application of U.S.
application Ser. No., Ser. No. 10/272,319, which was filed Oct. 16,
2002 and claims priority to Korean Patent Application No.
2002-39160 filed on Jul. 6, 2002, the entire disclosures of which
are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of integrated
circuit fabrication, and more particularly, to clean rooms used in
the fabrication of integrated circuits.
BACKGROUND OF THE INVENTION
[0003] Integrated circuit devices are typically fabricated in what
is commonly referred to as a clean room environment. As the term
implies, a clean room environment can be essentially free of
particles that can affect the yield of the integrated circuits
produced in the clean room.
[0004] In particular, substances, either created during the
manufacturing process itself or introduced to the clean room via
external air supplied to the clean room, can contaminate the
integrated circuits produced by the clean room thereby leading to
their premature failure.
[0005] The types of devices fabricated in the clean room can
dictate the degree of filtering of external air provided to the
clean room. For example, studies have shown that in order to
reliably produce 256 MB DRAMs having a design rule of 0.25 .mu.m,
particles having a size greater than 0.25 .mu.m should be removed
or filtered from the clean room. In addition, the temperature,
humidity, and pressure of the air in the clean room may be
controlled. Other types of environmental factors, such as
illumination, noise, and vibration, may also be controlled.
[0006] In order to provide the filtering discussed above, air is
provided to the clean room through an air conditioning apparatus
having filter units that can filter external air (i.e., air
obtained from an external environment) to the clean room. In
particular, in some conventional approaches, fresh air produced by
the air conditioner is introduced below the floor of the clean room
which is then circulated above the ceiling of the clean room and
into the clean room.
[0007] As the concentration of fine particles contained in the
external air is increased, it may be difficult for a conventional
air conditioner to filter the air to the level needed by the clean
room which can increase contamination in the clean room resulting
in a decrease in the yield of integrated circuits manufactured in
the clean room. For example, a phenomenon referred to as "yellow
sand dust" (or "dust") can dramatically affect the yield of
integrated circuits produced in a clean room. The yellow sand dust
phenomenon can be characterized as when the external air includes
an abnormally high level of sulfuric oxide, nitric oxide, and/or
silicon. The yellow sand dust phenomenon can occur at particular
times of the year and in particular geographic locations. For
example, measurements in the area of Seoul, Republic of Korea in
the year 2001, showed that density of dust in the air during the
occurrence of the yellow sand dust phenomenon was about 7 to 14
times greater than the density at other times of the same year in
the same location. In particular, the density of the dust was
measured to be in a range between about 473 .mu.g/m.sup.3 and about
999 .mu.g/m.sup.3 during 2001 in Seoul. Furthermore, ozone,
SO.sub.2 and/or NO.sub.x contained in the external air during the
summer months can in turn be introduced into the clean room if
proper filtering is not performed.
[0008] FIG. 1 is a greatly enlarged schematic view that illustrates
a particle 10 lodged on a pattern 20 of an integrated circuit in a
clean room. The particle 10 can cause the integrated circuit to be
inoperative or to function improperly. The particle 10 can be about
0.05 .mu.m in diameter and have a circular or annular ring
shape.
[0009] FIG. 2 is a graph that illustrates measured compositions of
the particle 10 shown in FIG. 1. In particular, an EDS (Energy
Dispersive X-ray Spectrometer) shows that the particle 10 can
include significant amounts of silicon and oxygen which are present
in the composition of the dust produced during the yellow sand dust
phenomenon. As shown in FIG. 2, many of the particles shown in the
EDS have a size less than 0.05 .mu.m.
[0010] It is known to use an air conditioner including an HEPA
(high efficiency particulate air filter) and a chemical filter to
filter air provided to a clean room. U.S. Pat. No. 5,890,367 to You
et al. entitled Air Conditioning System for Semiconductor Clean
Room Including a Chemical Filter Downstream of a Humidifier,
discusses the removal of chemical impurities from the air provided
by the air conditioner, such as phosphoric acid generated by the
process of manufacturing the integrated circuits, using a chemical
filter located between the air conditioner, having a humidifier,
and an ULPA (ultra low penetration air) filter.
SUMMARY OF THE INVENTION
[0011] Embodiments according to the present invention can provide
fresh air ducts including separate particle filters downstream from
air conditioning systems for use with clean rooms. Pursuant to
these embodiments, a fresh air duct can be configured to direct
fresh air filtered by an air conditioning system towards a clean
room downstream from the fresh air duct, the fresh air having a
first level of particle density. A separate particle filter in the
fresh air duct, located downstream from the air conditioning system
and upstream from the clean room, can be configured to further
filter the fresh air to provide filtered fresh air having a second
level of particle density therein that is less than the first
level.
[0012] In some embodiments according to the present invention, the
air conditioning system accepts external air having a third level
of particle density that is greater than the first and second
levels and is in a range between about 473.mu./m.sup.3 and about
999 g/m.sup.3. In some embodiments according to the present
invention, the separate particle filter is in an outlet section of
the fresh air duct adjacent the clean room.
[0013] In some embodiments according to the present invention, the
separate particle filter can be at least one of an HEPA filter
configured to filter about 99.97% of particles about 0.3 .mu.m in
size from the fresh air generated by the air conditioning system,
an ULPA filter configured to filter about 99.99% of particles about
0.1 .mu.m to about 0.17 .mu.m in size from the fresh air generated
by the air conditioning system, and an ozone filter.
[0014] In some embodiments according to the present invention, a
second filter is located downstream from the first filter and
upstream from the clean room. The second filter can be at least one
of an HEPA filter configured to filter about 99.97% of particles
about 0.3 .mu.m in size from the fresh air generated by the air
conditioning system, an ULPA filter configured to filter about
99.99% of particles about 0.1 .mu.m to about 0.17 .mu.m in size
from the fresh air generated by the air conditioning system, a
chemical filter and an ozone filter. In some embodiments according
to the present invention, the second filter is included in an
outlet section of the fresh air duct adjacent to the clean
room.
[0015] In some embodiments according to the present invention, the
separate particle filter can be a detachable filter and the fresh
air duct can further include a first portion of the fresh air duct
configured to direct air from an input of the fresh air duct to an
output of the first portion and a second portion of the fresh air
duct releaseably coupled to the output of the first portion and
configured to direct air from the output of the first portion along
a pathway through the second portion. The detachable filter is in
the second portion of the fresh air duct.
[0016] In some embodiments according to the present invention, the
detachable filter can be a first detachable filter. An outlet
portion of the fresh air duct is located downstream from the second
portion and a second detachable filter is in the outlet portion
configured to provide filtered air downstream of the second
detachable filter to the clean room. In some embodiments according
to the present invention, the filter is located adjacent to an
input of the second portion of the fresh air duct.
[0017] In some embodiments according to the present invention, the
first portion can be a flexible section configured to allow the
first portion of the fresh air duct to move away from an input of
the second portion of the fresh air duct to expose the detachable
filter. In some embodiments according to the present invention, a
third portion of the fresh air duct is coupled to the second
portion and has at least one output therefrom. A second detachable
filter is included in the third portion and is configured to filter
the fresh air conducted along the pathway to the at least one
output from the fresh air duct into the clean room.
[0018] In some embodiments according to the present invention, a
third portion of the fresh air duct is coupled to the second
portion and has a plurality of outputs therefrom. A plurality of
detachable filters is located in the third portion upstream from
the plurality of outputs.
[0019] In further embodiments according to the present invention, a
fresh air duct is located downstream from an air conditioning
system and is configured to direct fresh air from the air
conditioning system to a clean room. A detachable filter, is
located in the fresh air duct and is configured to filter the fresh
air to provide filtered fresh air downstream of the detachable
filter.
[0020] In some embodiments according to the present invention, the
fresh air duct can be a first portion of the fresh air duct
configured to direct air from an input of the fresh air duct to an
output of the first portion and a second portion of the fresh air
duct that is releaseably coupled to the output of the first portion
and is configured to direct air from the output of the first
portion along a pathway through the second portion, wherein the
detachable filter is in the second portion of the fresh air duct.
In some embodiments according to the present invention, the
detachable filter is inside the clean room.
[0021] In some embodiments according to the present invention, an
outlet portion of the fresh air duct is lcoated downstream from the
second portion. A second detachable filter is located in the outlet
portion and is configured to provide filtered air downstream of the
second detachable filter into the clean room.
[0022] Embodiments of methods according to the present invention
can include providing fresh air filtered by an air conditioning
system downstream towards the clean room, the fresh air having a
first level of particle density, further filtering the fresh air
downstream from the air conditioning system to provide filtered
fresh air having a second level of particle density that is less
than the first level and providing the filtered fresh air to the
clean room.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a greatly enlarged schematic view of a particle
lodged on a pattern of an integrated circuit device.
[0024] FIG. 2 is an EDS illustrating the composition of a particle
commonly associated with the yellow sand dust phenomenon.
[0025] FIG. 3 is a schematic view that illustrates embodiments of
clean room systems according to the present invention.
[0026] FIGS. 4A-4B are schematic views that illustrate embodiments
of fresh air ducts according to the present invention.
[0027] FIG. 5 is a schematic frontal view that illustrates
embodiments of a filter on a filter frame and grill according to
the present invention.
[0028] FIG. 6 is a bar graph that illustrates the density of ozone
present in a clean room at different times of the year.
[0029] FIG. 7 is a schematic view that illustrates embodiments of
clean room systems according to the present invention.
[0030] FIG. 8 is a schematic sectional view that illustrates
embodiments of fresh air ducts according to the present
invention.
[0031] FIG. 9 is a schematic view that illustrates embodiments of
clean room systems according to the present invention.
[0032] FIG. 10 is a schematic sectional view that illustrates
embodiments of fresh air ducts according to the present
invention.
[0033] FIG. 11 is a graph that illustrates comparative measurements
of particles in a conventional clean room system and in embodiments
of a clean room system according to the present invention.
[0034] FIG. 12 is a bar graph that illustrates comparative
measurements of the density of silicon in baths in a conventional
clean room and in embodiments of clean rooms according to the
present invention.
DESCRIPTION OF EMBODIMENTS ACCORDING TO THE INVENTION
[0035] The present invention now will be described more fully
hereinafter with reference to the accompanying drawings, in which
typical embodiments of the invention are shown. This invention may,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein. Rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. In the drawings, the
relative sizes of regions may be exaggerated for clarity. It will
be understood that when an element such as a duct or portion of a
duct is referred to as being "connected" or "coupled" to another
element, it can be directly connected to the other element or
intervening elements may also be present. In contrast, when an
element is referred to as being "directly connected" or "directly
coupled" to another element, there are no intervening elements
present. Terms used herein are to be given their ordinary meaning
unless explicitly defined otherwise herein.
[0036] FIG. 3 is a schematic diagram that illustrates embodiments
of clean room systems according to the present invention. As shown
in FIG. 3, the clean room system includes a clean room 320 in which
integrated circuit devices are fabricated. An air conditioning
system 300 accepts external air (i.e., air external to the clean
room 320) and provides fresh air, via a fresh air duct 302,
downstream to a lower space 310A of the clean room 320. The fresh
air is then circulated to an upper space 310B of the clean room 320
as illustrated.
[0037] The air conditioner 300 filters particles in the external
air using a plurality of filters 300A, 300B, 300C and 300D. The air
conditioner 300 can also include a heater 300E and a cooler 300F,
located downstream from the filters 300A-300D, for controlling the
temperature of the air. The air conditioner 300 can further include
a humidifier 300G, downstream from the heater 300E and cooler 300F,
for adjusting the humidity of the air. The humidifier 300G is
located downstream from the filters 300A-300D to avoid introducing
excessive moisture into the filters 300A-D which could otherwise
adversely affect the efficiency of the filters. The air conditioner
300 can further include a blower 300H, at an outlet of the air
conditioner 300, configured to force the fresh air from the air
conditioner 300 into the fresh air duct 302.
[0038] The air conditioner 300 will now be described in greater
detail. The filters 300A-300D can be selected to filter particles
of different sizes. Moreover, the filters 300A-300D can be arranged
in a sequence according the size of the particles to be filtered.
For example, filter 300A can be selected to filter the largest
particles whereas each of the remaining filters can be arranged to
filter decreasingly smaller particles such that filter 300D filters
the smallest sized particles of the filters 300A-300D.
[0039] External air is introduced into the air conditioner 300
through a roll filter 300A which can remove impurities from the
external air. A demister 300B is located downstream from the roll
filter 300A and is configured to remove or reduce the moisture and
impurities in the air. A medium filter 300C is located downstream
from the demister 300B and is configured to remove minute dust from
the air, preferably at an efficiency of at least about 90%. In some
embodiments according to the present invention, the medium filter
300C is an HEPA filter which can filter particles having a size of
about 0.3 .mu.m from the air at an efficiency of at least about
99.97%.
[0040] In some embodiments according to the invention, the heater
300E and the cooler 300F are located downstream from the filters
300A-D. In some embodiments according to the present invention, the
cooler 300F is located downstream from the heater 300E so that
moisture introduced into the air by the heater 300E can be reduced
by the cooler 300F.
[0041] In other embodiments according to the present invention, the
heater 300E and the cooler 300F are upstream from the filters
300A-300D. The air output from the heater 300E flows through the
humidifier 300G before being provided to the clean room 320 so that
the humidity of the air can be adapted if needed. A blower 300H is
located at the outlet of the air conditioner 300 to force the fresh
air from the air conditioner 300 into the fresh air duct 302.
During times when the sand dust phenomenon occurs, the density of
the particle impurities in the fresh air can be about 1,200,000
EA/cfm (cubic feet per minute).
[0042] The fresh air duct 302 is configured to conduct the fresh
air from the air conditioner 300 to the lower space 310A of the
clean room. The fresh air duct 302 includes a filter 106 which
provides secondary filtering of the fresh air provided by the air
conditioner 300. The filter 106 can be selected based on the types
of particles and contaminants contained in the external air at a
particular time. Because the fresh air has passed through filters
300A-300D, the filter 106 preferably has an efficiency that is at
equal or superior to the filter efficiency of the filter 300D. In
some embodiments according to the present invention, the filter 106
is an HEPA filter capable of filtering particles having a size of
about 0.3 .mu.m at an efficiency of at least 99.97%. In other
embodiments according to the present invention, the filter 106 is
an ULPA filter that is capable of filtering particles having a size
in a range between about 0.12 .mu.m and about 0.17 .mu.m at an
efficiency of at least about 99.99%. In other embodiments according
to the present invention, when the external air includes
contaminants, such as sulfuric acid or nitric oxide, a chemical
filter can also be provided in the fresh air duct 302 (as described
herein, for example, with reference to FIG. 10). For example,
during times when the sand dust phenomenon occurs, the density of
0.3 .mu.m sized particles in the filtered fresh air provided by an
HEPA filter 106 can be in a range between about 400,000 EA/cfm and
about 500,000 EA/cfm.
[0043] According to the present invention, the inclusion of the
filter 106 in the fresh air duct 320 downstream from the filters
300A-D in the air conditioner 300 allows the particles in the air
to be filtered in separate steps. When the density of the particles
in the external air is exceptionally high, such as when the yellow
sand dust phenomenon occurs, embodiments according to the present
invention can nonetheless provide adequate filtering for clean
rooms. Otherwise, the external air may be contaminated with so many
particles that the efficiency of the filters 300A-300D is reduced
to the point that the air provided by the air conditioner 300
causes an unacceptable number of defects in the manufacturing
process in the clean room. Therefore, the filter 106 can further
filter the fresh air provided by the air conditioner 300 to provide
fresh air having a lower density of particles than the fresh air
provided by the air conditioner 300, particularly when the yellow
sand dust phenomenon occurs.
[0044] In some embodiments according to the present invention, the
type of filtering provided in the fresh air duct 302 can be
adjusted as the condition of the external air changes. For example,
if the external air includes chemical contaminants, such as
sulfuric oxide or nitric oxide, the filter 106 can be a chemical
filter. In some embodiments according to the present invention, an
HEPA filter or an ULPA filter can be used if the particle size is
particularly small.
[0045] Furthermore, in the summer months in Korea, the density of
ozone in the air may be higher than in other times of the year.
FIG. 6 is a bar graph illustrating differences in the density of
ozone in a clean room measured in a summer season and in other
times during the year. In particular, the bar graph on the left
side of FIG. 6 shows the minimum and maximum values of the density
of ozone measured in the clean room during times of than the summer
months (i.e., ordinary times). In contrast, the bar graphs on the
right side of FIG. 6 illustrates the minimum and maximum values of
ozone density measured in a clean room during the summer season. As
shown in FIG. 6, the density of the ozone measured in the clean
room during the summer season is 4 to 4 1/2 times greater than the
density of the ozone measured in the clean room during other times
of the year. Therefore, according to the present invention, an
ozone filter may be attached to the fresh air duct during the
summer season to provide additional filtering of ozone. If the
increased amount of ozone in the external air is not filtered, the
density of the ozone introduced into the-clean room may increase
and thereby cause additional defects in the integrated circuits
fabricated therein.
[0046] The fresh air duct 302 will now be described in further
detail. FIGS. 4A and 4B are sectional views that illustrate
embodiments of fresh air ducts according to the present invention.
According to FIG. 4A, the fresh air duct 302 is located downstream
from the air conditioner system 300. In some embodiments according
to the present invention, the fresh air duct 302 is configured to
conduct the fresh air provided by the air conditioner 300 from a
first portion 101 of the fresh air duct 302 downstream to a second
portion 108 of the fresh air duct 302 along a pathway defined by
the fresh air duct 302 to the clean room.
[0047] The fresh air duct 302 includes a filter 106 positioned in
the pathway. In some embodiments according to the present
invention, the filter 106 is an HEPA filter capable of filtering
particles having a size of 0.3 .mu.m at an efficiency of at least
about 99.97%, or an ULPA filter capable of filtering particles
having a size of about 0.1 .mu.m at an efficiency of at least about
99.99%. It will be further understood that an ozone filter capable
of removing ozone and/or a chemical filter for filtering chemical
contaminants such as sulfuric oxide or nitric oxide may be used in
addition to the filters discussed above.
[0048] In some embodiments according to the present invention, the
filter 106 is detachably coupled within the second portion 108 and
filters the air provided through the first portion 101 to provide
filtered fresh air downstream of the filter 106. The first portion
101 is releasably coupled to the second portion 108 so that the
filter 106 may be more easily removed from the fresh air duct 302
compared to conventional systems.
[0049] In some embodiments according to the present invention, a
flexible section 101 A of the first portion 101 allows an output of
the first portion 101 to be retracted from an input of the second
portion 108 so that the filter 106 can be exposed and thereby
accessed for detachment and replacement as shown, for example, in
FIG. 4B. It will be further understood that the flexible section
101A may flex from side to side in addition to retracting from the
input to the second portion 108 to further facilitate ease of
replacement of the filter 106. In some embodiments according to the
present invention, the flexible section 101A is in the form of
bellows as shown in FIG. 4A. In other embodiments according to the
present invention, the flexible section 101A can be an elastic
material, such as rubber, and takes the form of a sleeve without
the bellows type of arrangement shown in FIG. 4A.
[0050] In some embodiments according to the present invention, an
attachment section 104 includes first and second pieces that are
releasably coupled to one another thereby allowing the first and
second portions 101, 108 to be releasably coupled to one another.
The first piece is coupled to the output of the first portion 101
whereas the second piece is coupled to the input of the second
portion 108. It will be understood that other configurations of the
attachment section 104 may be used.
[0051] In particular, the first piece of the attachment section 104
includes a fixing frame 104C and a fastening member 104D. The
second piece of the attachment section 108 includes a filter frame
104A which positions the filter 106 along the pathway defined by
the fresh air duct and a grill 104B which overlies and can protect
the filter 106. The first piece of the attachment section 104 is
configured to be releaseably coupled to the second piece of
attachment section 104 by securing the filter frame 104A to the
fixing frame 104C using the fastening member 104D. In some
embodiments according to the present invention, the fastening
member 104D includes a plurality of bolts or screws located near
the edges of the fixing frame 104C. A plurality of holes are
located in the filter frame 104A so that the fastening member 104D,
such as a plurality of bolts or screws, can be aligned and inserted
into the holes. The plurality of bolts or screws can then be
tightened to couple the first piece of the attachment section 104
to the second piece of attachment section 104, thereby coupling the
first portion 101 to the second portion 108.
[0052] It will be understood that in other embodiments according to
the present invention, the fastening member 104 can be other
mechanisms, such as latches. It will be understood that in some
embodiments according to the present invention, a series of
attachment sections may be included in the fresh air duct 302
wherein each of the respective attachment sections holds a
respective filter for a specific use in further filtering the fresh
air.
[0053] FIG. 5 is a frontal view that illustrates embodiments of the
second piece of the attachment section 104 according to the present
invention. As discussed above, the filter frame 104A provides a
space in which the filter 106 can be inserted. The grill 104B is
detachably installed adjacent to a face of the filter frame 104A,
such as the face which faces upstream. The grill 104B can be a
lattice-type grill which supports and protects the filter 106.
[0054] In operation, the filter 106 can be replaced by stopping or
slowing the blower 300H to reduce the air flow downstream to the
filter 106. In some embodiments according to the present invention,
the filter 106 is replaced by loosening the fastening member 104D
thereby releasing the fixing frame 104C from the filter frame 104A
as shown in FIG. 4B. The flexible section 101A can be retracted
from the second portion 108 to expose the filter 106. The grill
104B is removed from the filter frame 104A and the filter 106 is
removed from the filter frame 104A. A replacement filter 106 is
mounted in the filter frame 104A and the grill 104B is replaced
over the replacement filter 106 and secured to the filter frame
104A. The flexible section 101A is extended so that the fixing
frame 104C contacts the filter frame 104A and the fastening member
104D is used to fasten the first portion 101 to the second portion
108 of the fresh air duct 302.
[0055] Returning now to the description of the clean room system
shown in FIG. 3, air flowing from the fresh air duct 302 passes
through the filter 106 and is introduced through an outlet into a
lower space 310A of the clean room. An air circulating section 312
circulates the air from the lower space 310A to an upper space 310B
located above the ceiling of the clean room. The air circulating
section 312 further circulates the air already existing in the
clean room with the fresh air that is supplied via the fresh air
duct 302. The air circulating section 312 includes a pre-filter for
filtering contaminated air in the lower space 310A. The air
circulating section 312 also includes a bag filter capable of
filtering particles contained in the air and an efficiency of at
least about 90% and an axial fan for circulating the air that is
passed through the filters.
[0056] A clean room filter 330 filters the air supplied from the
air circulating section 312 into the clean room 320. The clean room
filter 330 can be located in the ceiling of the clean room 320. The
air filtered by the clean room filter 330 travels from the upper
space 310B through a grating into the clean room 320. The air exits
the clean room 320 into the lower space 310A. The air in the lower
space 310A can be recirculated into the upper space 310B above the
ceiling of the clean room 320 through the air circulating section
312.
[0057] Accordingly, the clean room filter 330 filters the particles
contained in the air before the air is introduced into the clean
room 320. The clean room filter 330 filters particles that are
smaller than the particles filtered by the filters 300A-300D.
Because the particles contained in the external air can be removed
or greatly reduced by the filter 106, the clean room filter 330 can
be used to filter the contaminants in the clean room 320 generated
by the manufacturing process itself. In some embodiments according
to the present invention, the clean room filter 330 can be an ULPA
filter capable of filtering particles having a size and a range
between about 0.12 .mu.m and about 0.17 .mu.m at an efficiency of
at least about 99.99%.
[0058] In some embodiments according to the present invention,
about 70% of the air introduced into the clean room 320 is
circulated throughout the clean room 320. Furthermore, in some
embodiments according to the present invention, about 30% of the
air is discharged from the clean room system through an exhaust
apparatus that operates during the fabrication of integrated
circuits in the clean room 320. Therefore, a volume of air equal to
30% of air discharged by the exhaust system is introduced through
the fresh air duct 320 according to the present invention.
[0059] FIG. 7 is a schematic diagram illustrating embodiments of a
clean room system according to the present invention. The clean
room system shown in FIG. 7 is substantially identical to the clean
room system disclosed above in reference to FIG. 3. Accordingly, a
detailed description of many of the common elements of the clean
room system shown in FIG. 7 will not be repeated here.
[0060] In some embodiments according to the present invention,
first and second filters 204 are included in an outlet section of a
fresh air duct 402 through which the fresh air is provided to a
lower space 410A of the clean room system. In some embodiments
according to the present invention, the first and second filters
204 are different from one another. For example, in some
embodiments according to the present invention, the first filter
204 can be an HEPA filter whereas the second filter 204 can be an
ULPA filter, an ozone filter, or a chemical filter.
[0061] FIG. 8 is a sectional view that illustrates embodiments of
the outlets 201 of fresh air ducts according to the present
invention as shown in FIG. 7. As shown in FIG. 8, the filter 204 is
positioned in the outlet portion of the fresh air duct downstream
from a damper 206 configured to control the flow of the fresh air
through the outlet section 201. In particular, the outlet section
201 is positioned downstream from an air conditioner system 400 and
filters the fresh air provided to the clean room 420.
[0062] In some embodiments according to the present invention, the
filter 204 is positioned along the pathway defined by the outlet
section 201 by an attachment section 202 and, in particular, is
located in a filter frame 202A. A filter grill 202B overlies the
filter 204 and is attached to the filter frame 202A to protect the
filter 204 and to hold the filter 204 in place. The attachment
section 202 further includes a fixing frame 202C and a fastening
member 202D which releasably couples the fixing frame 202C to the
filter frame 202A. The fixing frame 202C can be detached from the
filter frame 202A by removing the fastening member 202D and the
fixing frame 202C to expose the filter 204 which then may be
removed and replaced. The fixing frame 202C and fastening member
202D can be recoupled to the filter frame 202A.
[0063] In will be understood that the first and second outlets 201
can provide filtered fresh air to different areas of the clean room
420. For example, in some clean rooms, dedicated fresh air duct
outlets are provided for different areas which perform
photolithography, etching, implant, deposition, as each of these
processes may require different degrees of filtering. Therefore,
respective outlets 201 according to the present invention can be
configured with different filters selected for the different areas
of the clean room 420.
[0064] FIG. 9 is a schematic diagram illustrating a clean room
system according to the present invention including filters in the
fresh air duct and the outlets. In particular, FIG. 9 illustrates a
fresh air duct 352 including a filter 154 according to the present
invention and first and second auxiliary filters 164 according to
the present invention in the outlet sections, as discussed above,
for example, in reference to FIGS. 3 and 7 respectively.
Accordingly, a further detailed description of these filters is
omitted.
[0065] Generally, the fresh air duct 352 includes at least one
filter 154 for filtering particles contained in the air provided by
an air conditioning system 350 located upstream. The auxiliary
filters 164 are located at first and second outlets and can be
different types of filters. For example, one of the auxiliary
filters 164 can be an HEPA filter whereas the other auxiliary
filter 164 can be an ULPA filter, an ozone filter, or a chemical
filter.
[0066] FIG. 10 is a sectional view that illustrates embodiments of
fresh air ducts according to the present invention. According to
FIG. 10, a fresh air duct 150 including a filter 154 is
substantially identical to the fresh air ducts illustrated in FIGS.
4A and 4B and further includes an auxiliary filter 164 located
downstream from the filter 154. According to FIG. 10, fresh air
provided by an upstream air conditioner flows into a first portion
151 of the fresh air duct 150 which travels downstream to a second
portion 158 of the fresh air duct 150 through the filter 154. The
elements shown in FIG. 10, including a first attachment section
152, are substantially the same as those described above in
reference to FIGS. 4A and 4B and will not be described further. The
fresh air duct 150 further includes a damper 160 downstream from
the second portion 158. The damper 160 is configured to interrupt
or reduce the flow of fresh air downstream. The auxiliary filter
164 is located downstream from the damper 160 and is positioned
along the pathway defined by the second portion 158. In particular,
the auxiliary filter 164 is positioned in the second portion 158
adjacent to the output therefrom. The filter 164 is connected to a
second attachment section 162. The second attachment section 162
includes an auxiliary filter frame 162A which holds the auxiliary
filter 164 and a grill 162B which overlies the auxiliary filter
164. The auxiliary filter frame 162A is releasably coupled to a
fixing frame 162C by a fastening member 162D. In some embodiments
according to the present invention, the auxiliary filter 164 can be
an HEPA filter, and ULPA filter, a chemical filter, or an ozone
filter. In some embodiments according to the present invention, the
auxiliary filter 164 is an ozone filter or a chemical filter.
During times when the sand dust phenomenon occurs, the density of
0.3 .mu.m sized particles in the filtered fresh air provided by the
auxiliary filter 164 can be in a range between about 1,000 EA/cfm
and about 2,000 EA/cfm.
[0067] FIG. 11 is a graph illustrating the amount of particles
measured in a fresh air duct of a conventional clean room system
compared to the amount of particles measured in a fresh air duct
according to embodiments of the present invention. The measurements
were taken during the period from Mar. 20, 2001 to Apr. 10, 2001 in
The Republic of Korea. The yellow sand dust phenomenon discussed
above occurred during the period from Mar. 20, 2001 to Mar. 25,
2001 and from Apr. 7, 2001 to Apr. 10, 2001 (hereinafter referred
to as the "interval"). During this time, the maximum dust density
at the peak time was in a range between above 500 .mu.g/m.sup.3 and
about 1000 .mu.g/m.sup.3.
[0068] As shown by 600a in FIG. 11, the amount of particles in the
fresh air duct of the conventional system was abnormally high
during the interval. In contrast, as shown by 600b in FIG. 11, the
amount of particles in a fresh air duct according to embodiments of
the present invention, was not abnormally high and was less than
that measured in the conventional fresh air duct during the
interval. In FIG. 11, the increase in the amount of particles for
the period from Mar. 30, 2001 to Apr. 2, 2001 was caused by a
measurement error. As illustrated by FIG. 11, the fresh air
provided to the clean room by embodiments according to the present
invention, may be contaminated by fewer particles compared to
conventional approaches, even during the yellow sand dust
phenomenon.
[0069] FIG. 12 is a bar graph illustrating densities of silicon
measured in a cleaning liquid bath in a conventional clean room and
densities of silicon measured in a cleaning liquid bath in a clean
room according to embodiments of the present invention. According
to FIG. 12, the density of silicon detected in the cleaning liquid
number 1 to number 4 in the bath in the conventional clean room was
in a range between about 3 and about 8 parts per billion. In
contrast, the density of silicon measured in the cleaning liquid
bath of the clean room according to embodiments of the present
invention (number 6 to number 15) was less than 1 part per billion.
Accordingly, the contamination of the clean room due to particles
in the external air was reduced in clean rooms utilizing
embodiments according to the present invention.
[0070] It should be noted that many variations and modifications
might be made to the embodiments described above without
substantially departing from the principles of the present
invention. All such variations and modifications are intended to be
included herein within the scope of the present invention, as set
forth in the following claims.
* * * * *