U.S. patent application number 10/373684 was filed with the patent office on 2003-08-28 for method and apparatus for cleaning and drying semiconductor wafer.
This patent application is currently assigned to A-Tech Ltd. Republic of Korea. Invention is credited to Lee, Chang-Keun, Lee, Joong-Yeon, Lee, Sang-Ho, Park, Jin-Koo, Yoon, Neung-Goo.
Application Number | 20030159713 10/373684 |
Document ID | / |
Family ID | 27761247 |
Filed Date | 2003-08-28 |
United States Patent
Application |
20030159713 |
Kind Code |
A1 |
Park, Jin-Koo ; et
al. |
August 28, 2003 |
Method and apparatus for cleaning and drying semiconductor
wafer
Abstract
Provided is an apparatus and method for cleaning and drying a
semiconductor wafer. Isopropyl alcohol and deionized water are
premixed in a desired ratio before a cleaning solution containing
isopropyl alcohol and deionized water is supplied into a treating
bath. Accordingly, a chemical compound remaining due to deionized
water can be effectively removed and the creation of water marks
due to isopropyl alcohol can be effectively prevented. As a result,
cleaning and drying effects can be increased and a cleaning
solution can be reused.
Inventors: |
Park, Jin-Koo; (Ansan-City,
KR) ; Lee, Joong-Yeon; (Icheon-City, KR) ;
Yoon, Neung-Goo; (Pyungtack-City, KR) ; Lee,
Chang-Keun; (Pyungtack-City, KR) ; Lee, Sang-Ho;
(Seoul, KR) |
Correspondence
Address: |
ROTHWELL, FIGG, ERNST & MANBECK, P.C.
1425 K STREET, N.W.
SUITE 800
WASHINGTON
DC
20005
US
|
Assignee: |
A-Tech Ltd. Republic of
Korea
|
Family ID: |
27761247 |
Appl. No.: |
10/373684 |
Filed: |
February 27, 2003 |
Current U.S.
Class: |
134/2 ; 134/110;
134/198; 134/32; 134/95.2; 257/E21.228 |
Current CPC
Class: |
H01L 21/67057 20130101;
H01L 21/02052 20130101; H01L 21/67028 20130101 |
Class at
Publication: |
134/2 ; 134/32;
134/95.2; 134/110; 134/198 |
International
Class: |
C23G 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 28, 2002 |
KR |
2002-10969 |
Oct 1, 2002 |
KR |
2002-59765 |
Oct 1, 2002 |
KR |
2002-59764 |
Claims
What is claimed is:
1. An apparatus for cleaning and drying a semiconductor wafer, the
apparatus comprising: a treating bath supplied with a cleaning
solution from an external source and in which the semiconductor
wafer is cleaned and dried; a cleaning solution mixing unit wherein
cleaning solutions to be supplied into the treating bath are mixed
in a predetermined ratio and including isopropyl alcohol tanks that
are supplied with isopropyl alcohol from an external source, mixing
tanks that are supplied with deionized water from an external
source, are connected to the isopropyl alcohol tanks to be supplied
with isopropyl alcohol contained in the isopropyl alcohol tanks and
mix isopropyl alcohol and deionized water, and level sensing means
that sense the amount of isopropyl alcohol supplied into the IPA
tanks and the amount of deionized water supplied into the mixing
tanks; a cleaning solution supplying unit that connects the mixing
tanks to the treating bath and supplies the cleaning solution mixed
in the mixing tanks into the treating bath; and a return line
through which the cleaning solution that was used in the cleaning
of the semiconductor wafer is returned back to the mixing
tanks.
2. The apparatus of claim 1, wherein two or more isopropyl alcohol
tanks of the cleaning solution mixing unit are interconnected in
parallel, the mixing tanks are connected to the isopropyl alcohol
tanks, respectively, and disposed in parallel so that each of the
isopropyl alcohol tanks and each of the mixing tanks make a group,
and the cleaning solution circulates through a mixing tank in a
group selected from two or more groups.
3. The apparatus of claim 1 or 2, wherein the level sensing means
are a plurality of level sensors that are installed at the
isopropyl alcohol tanks and a plurality of level sensors that are
installed at the mixing tanks.
4. The apparatus of claim 1 or 2, wherein the cleaning solution
mixing unit further comprises a nitrogen bubble generator that
injects a nitrogen gas into the mixing tanks so as to completely
mix deionized water and isopropyl alcohol.
5. The apparatus of claim 1 or 2, wherein isopropyl alcohol
supplementing pumps that additionally supply isopropyl alcohol in
the isopropyl alcohol tanks into the mixing tanks by a desired
amount are further installed between the isopropyl alcohol tanks
and the mixing tanks.
6. The apparatus of claim 1 or 2, wherein the cleaning solution
supplying unit comprises: a circulating pump that pumps the
cleaning solution in the mixing tanks into the treating bath; a
filter that filters the cleaning solution flowing via the
circulating pump off impurities; an isopropyl alcohol concentration
measurer that checks the concentration of isopropyl alcohol
contained in the cleaning solution that has passed through the
filter; and a liquid particle counter that detects the amount of
liquid particle contained in the cleaning solution flowing into the
treating bath.
7. The apparatus of claim 1 or 2, wherein the return line comprises
a liquid particle counter that detects liquid particle contained in
the cleaning solution returning from the treating bath back to the
mixing tanks.
8. The apparatus of claim 1 or 2, further comprising: a heating
tank that is connected to the cleaning solution mixing unit, is
supplied the cleaning solution from the mixing tanks, and heats the
cleaning solution, and evaporates isopropyl alcohol from the
cleaning solution using a difference between boiling points of
isopropyl alcohol and deionized water to decompose the cleaning
solution into pure isopropyl alcohol and deionized water; an
isopropyl alcohol filter that is connected to the heating tank and
filters vapor isopropyl alcohol off impurities; an isopropyl
alcohol collecting tank that is supplied with isopropyl alcohol
filtered through the isopropyl alcohol filter and condenses
isopropyl alcohol; a deionized water filter that is connected to
the heating tank and passes deionized water remaining in the
heating tank to filter impurities of deionized water; and a
deionized water collecting tank that is supplied with deionized
water filtered through the deionized water filter and temporarily
stores deionized water.
9. The apparatus of claim 1 or 2, wherein a sink that is supplied
with deionized water from an external source and sinks a lower
portion of the treating bath under deionized water is further
installed beneath the treating bath, wherein the sink includes an
ultrasonic generator that generates ultrasonic waves, passes the
ultrasonic waves through deionized water and the treating bath to
the semiconductor wafer that is being cleaned in the treating
bath.
10. A method of cleaning and drying a wafer, the method comprising:
(a) mixing deionized water and isopropyl alcohol to make a cleaning
solution; (b) supplying the cleaning solution into a treating bath
so that the cleaning solution contacts the semiconductor wafer in
the treating bath to clean the semiconductor wafer; (c) after the
semiconductor wafer is cleaned, separating the semiconductor wafer
from the cleaning solution; (d) drying the semiconductor wafer
separated from the cleaning solution to remove the cleaning
solution remaining on the semiconductor wafer.
11. The method of claim 10, wherein in step (b), before the
cleaning solution is supplied into the treating bath, the
semiconductor wafer is put into the treating bath.
12. The method of claim 10, wherein in step (b), after the supply
of the cleaning solution into the cleaning bath is completed, the
semiconductor wafer is dipped into the cleaning solution.
13. The method of claim 10, wherein in step (c), the semiconductor
wafer is lifted up from the treating bath so that the semiconductor
wafer is separated from the cleaning solution.
14. The method of claim 10, wherein in step (c), the cleaning
solution is discharged from the treating bath so that the
semiconductor wafer is separated from the cleaning solution.
15. The method of claim 10, wherein in step (a), the concentration
of isopropyl alcohol in the cleaning solution varies according to
time to adjust the concentration of isopropyl alcohol to a target
concentration.
16. The method of claim 10, wherein in step (d), a hot nitrogen gas
is sprayed on the surface of the semiconductor wafer, contacts, and
dries the surface of the semiconductor wafer.
Description
BACKGROUND OF THE INVENTION
[0001] This application claims the priority of Korean Patent
Application Nos. 2002-10969, 2002-59765, and 2002-59764 filed on
February 28, October 1, and Oct. 1, 2002, respectively, in the
Korean Intellectual Property Office, the disclosure of which is
incorporated herein in its entirety by reference.
[0002] 1. Field of the Invention
[0003] The present invention relates to a method and apparatus for
cleaning and drying a semiconductor wafer, and more particularly,
to a method and apparatus for cleaning and drying a semiconductor
wafer using a mixture of isopropyl alcohol and deionized water as a
cleaning solution by which cleaning and drying effects can be
increased due to premixing isopropyl alcohol and deionized water in
an accurate ratio before supplying them into a treating bath in
which a cleaning process is performed and the cleaning solution
used in the cleaning process can be circulated and reused.
[0004] 2. Description of the Related Art
[0005] Generally, most semiconductor wafer cleaning methods were
developed in the 1970s, and use large amounts of chemical
solutions. A typical cleaning method of removing pollutants
remaining on a semiconductor wafer includes a standard clean-1
(SC1) process of removing particles and organic pollutants at an
ambient temperature or a high temperature using a mixture of 1:4:20
of ammonia, hydrogen peroxide, and water and a standard clean-2
(SC2) process of removing transient metal pollutants at a high
temperature using a mixture of 1:1:5 of hydrochloric acid, hydrogen
peroxide, and water.
[0006] In another cleaning method, a piranha cleaning process is
first performed to remove an organic pollutant such as a sensitizer
or a surfactant at a high temperature using a mixture of sulphuric
acid and hydrogen peroxide and an HF cleaning process is lastly
performed to effectively remove a natural oxide layer from the
surface of a wafer, and simultaneously, a metal pollutant from the
natural oxide layer.
[0007] The above-described conventional cleaning methods have
problems in that a chemical solution in a large amount is used
during a cleaning process, and the chemical solution is mainly a
mixture of an acid and a base, a base material of the mixture being
a hydrogen peroxide, and thus wastewater cannot be easily treated.
The use of a large amount of chemical solution and a large amount
of cleaning water results in increasing cleaning costs and is
environmentally regulated.
[0008] Since most cleaning processes are performed at a high
temperature, a chemical solution used for cleaning decomposes and
evaporates, which decreases the life span of the cleaning solution
and a cleaning effect. In addition, the reuse rate of the cleaning
solution is reduced due to the excessive use of deionized water
(DIW). Also, since the above-described conventional cleaning
process is composed of multi-steps, a huge piece of equipment is
necessary for performing the cleaning process.
[0009] After such a cleaning process, a process of drying the wafer
is performed. The drying process includes spin drying, isopropyl
alcohol (IPA) vapor drying, IPA layer drying, and so forth. Spin
drying is performed to remove a cleaning solution remaining on the
wafer using a centrifugal force by spinning the wafer at a high
speed. IPA vapor drying is performed so that IPA vapors contact the
surface of the wafer, and a residual liquid such as moisture
remaining on the surface of the wafer is substituted for IPA, and
then removed. IPA drying is performed so that a wafer is dipped
into a cleaning solution having a DIW layer and an IPA layer, DIW
and IPA sequentially contact the wafer to clean residual liquid
with DIW, and the residual liquid is substituted for IPA. IPA layer
drying is also called marangoni drying.
[0010] However, during spin drying, dust generated in the spinning
apparatus may be adsorbed onto the semiconductor wafer due to the
charging of the semiconductor wafer. In particular, moisture
remains in the notch lines for dicing the semiconductor wafer into
individual chips, trenches or contact holes, and creates water
marks.
[0011] During IPA vapor drying, since a vapor area is instable, IPA
vapors cannot uniformly contact the semiconductor wafer. Thus, the
possibility that water marks will be created is high. Also, since
flammable IPA vapors are used, accidental fires may break out.
[0012] Furthermore, marangoni drying can somewhat solve problems
occurring during spin drying or IPA vapor drying. However,
marangoni drying is not effective in removing various types of
pollutants, such as particles, which may remain on the surface of
the wafer.
SUMMARY OF THE INVENTION
[0013] Accordingly, the present invention provides an apparatus and
method for cleaning and drying a semiconductor wafer using a
mixture of IPA and DIW as a cleaning solution by which cleaning and
drying effects can be increased due to premixing IPA and DIW in an
accurate ratio before supplying them into a treating bath in which
a cleaning process is performed and the cleaning solution used in
the cleaning process can be circulated and reused to prevent waste
and reduce environmental pollution.
[0014] According to an aspect of the present invention, there is
provided an apparatus for cleaning and drying a semiconductor
wafer. The apparatus includes a treating bath, a cleaning solution
mixing unit, a cleaning solution supplying unit, and a return line.
The treating bath is supplied with a cleaning solution from an
external source and in which the semiconductor wafer is cleaned and
dried. The cleaning solution mixing unit mixes cleaning solutions
to be supplied into the treating bath in a predetermined ratio and
includes isopropyl alcohol tanks that are supplied with isopropyl
alcohol from an external source, mixing tanks that are supplied
with deionized water from an external source, are connected to the
isopropyl alcohol tanks to be supplied with isopropyl alcohol
contained in the isopropyl alcohol tanks and mix isopropyl alcohol
and deionized water, and level sensing means that sense the amount
of isopropyl alcohol supplied into the IPA tanks and the amount of
deionized water supplied into the mixing tanks. The cleaning
solution supplying unit connects the mixing tanks to the treating
bath and supplies the cleaning solution mixed in the mixing tanks
into the treating bath. The return line returns the cleaning
solution that was used in the cleaning of the semiconductor wafer
back to the mixing tanks.
[0015] Two or more isopropyl alcohol tanks of the cleaning solution
mixing unit are interconnected in parallel, the mixing tanks are
connected to the isopropyl alcohol tanks, respectively, and
disposed in parallel so that each of the isopropyl alcohol tanks
and each of the mixing tanks make a group, and the cleaning
solution circulates through a mixing tank in a group selected from
two or more groups.
[0016] The level sensing means are a plurality of level sensors
that are installed at the isopropyl alcohol tanks and a plurality
of level sensors that are installed at the mixing tanks.
[0017] The cleaning solution mixing unit further includes a
nitrogen bubble generator that injects a nitrogen gas into the
mixing tanks so as to completely mix deionized water and isopropyl
alcohol.
[0018] Isopropyl alcohol supplementing pumps additionally supply
isopropyl alcohol in the isopropyl alcohol tanks into the mixing
tanks by a desired amount are further installed between the
isopropyl alcohol tanks and the mixing tanks.
[0019] The cleaning solution supplying unit includes a circulating
pump, a filter, an isopropyl alcohol concentration measurer, and a
liquid particle counter. The circulating pump pumps the cleaning
solution in the mixing tanks into the treating bath. The filter
filters the cleaning solution flowing via the circulating pump off
impurities. The isopropyl alcohol concentration measurer checks the
concentration of isopropyl alcohol contained in the cleaning
solution that has passed through the filter. The liquid particle
counter detects the amount of liquid particle contained in the
cleaning solution flowing into the treating bath.
[0020] The return line includes a liquid particle counter that
detects liquid particle contained in the cleaning solution
returning from the treating bath back to the mixing tanks.
[0021] The apparatus further includes a heating tank, an isopropyl
alcohol filter, an isopropyl alcohol collecting tank, a deionized
water filter, and a deionized water collecting tank. The heating
tank is connected to the cleaning solution mixing unit, is supplied
the cleaning solution from the mixing tanks, and heats the cleaning
solution, and evaporates isopropyl alcohol from the cleaning
solution using a difference between boiling points of isopropyl
alcohol and deionized water to decompose the cleaning solution into
pure isopropyl alcohol and deionized water. The isopropyl alcohol
filter is connected to the heating tank and filters vapor isopropyl
alcohol off impurities. The isopropyl alcohol collecting tank is
supplied with isopropyl alcohol filtered through the isopropyl
alcohol filter and condenses isopropyl alcohol. The deionized water
filter is connected to the heating tank and passes deionized water
remaining in the heating tank to filter impurities of deionized
water. The deionized water collecting tank is supplied with
deionized water filtered through the deionized water filter and
temporarily stores deionized water.
[0022] A sink that is supplied with deionized water from an
external source and sinks a lower portion of the treating bath
under deionized water is further installed beneath the treating
bath. The sink includes an ultrasonic generator that generates
ultrasonic waves, passes the ultrasonic waves through deionized
water and the treating bath to the semiconductor wafer that is
being cleaned in the treating bath.
[0023] According to another aspect of the present invention, there
is also provided a method of cleaning and drying a wafer. Dionized
water and isopropyl alcohol are mixed to make a cleaning solution.
The cleaning solution is supplied into a treating bath so that the
cleaning solution contacts the semiconductor wafer in the treating
bath to clean the semiconductor wafer. After the semiconductor
wafer is cleaned, the semiconductor wafer is separated from the
cleaning solution. The semiconductor wafer separated from the
cleaning solution is dried to remove the cleaning solution
remaining on the semiconductor wafer.
[0024] Before the cleaning solution is supplied into the treating
bath, the semiconductor wafer may be put into the treating
bath.
[0025] After the supply of the cleaning solution into the cleaning
bath is completed, the semiconductor wafer may be dipped into the
cleaning solution.
[0026] The semiconductor wafer may be lifted up from the treating
bath so that the semiconductor wafer is separated from the cleaning
solution.
[0027] The cleaning solution may be discharged from the treating
bath so that the semiconductor wafer is separated from the cleaning
solution.
[0028] The concentration of isopropyl alcohol in the cleaning
solution varies according to time to adjust the concentration of
isopropyl alcohol to a target concentration.
[0029] A hot nitrogen gas is sprayed on the surface of the
semiconductor wafer, contacts, and dries the surface of the
semiconductor wafer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The above features and advantages of the present invention
will become more apparent by describing in detail exemplary
embodiments thereof with reference to the attached drawings in
which:
[0031] FIG. 1 is a schematic view of an apparatus for cleaning and
drying a semiconductor wafer according to an embodiment of the
present invention;
[0032] FIG. 2 is a view for explaining a step of dipping a
semiconductor wafer into a treating bath during cleaning and drying
a semiconductor wafer, according to an embodiment of the present
invention;
[0033] FIG. 3 is a view for explaining a step of dipping a
semiconductor wafer into a treating bath during cleaning and drying
a semiconductor wafer, according to another embodiment of the
present invention
[0034] FIGS. 4A through 4D are views illustrating examples of
moving a semiconductor wafer within a cleaning solution to further
effectively clean the semiconductor wafer put into a treating
bath;
[0035] FIG. 5 is a view for explaining a method of separating a
semiconductor wafer from a cleaning solution after the
semiconductor wafer is cleaned in a treating bath using a method of
cleaning and drying a semiconductor wafer according to an
embodiment of the present invention;
[0036] FIG. 6 is a view for explaining a step of separating a
semiconductor wafer from a cleaning solution after the
semiconductor wafer is cleaned in a treating bath in a method of
cleaning and drying a semiconductor wafer according to another
embodiment of the present invention;
[0037] FIG. 7 is a view for explaining a step of separating a
semiconductor wafer from a cleaning solution after the
semiconductor wafer is cleaned in a treating bath in a method of
cleaning and drying a semiconductor wafer according to still
another embodiment of the present invention;
[0038] FIG. 8 is a view for explaining a step of spraying a
nitrogen gas for drying a semiconductor wafer in a method of
cleaning and drying a semiconductor wafer according to an
embodiment of the present invention;
[0039] FIG. 9 is a view for explaining a step of spraying a
nitrogen gas for drying a semiconductor wafer in a method of
cleaning and drying a semiconductor wafer according to another
embodiment of the present invention;
[0040] FIGS. 10 through 12 are views for explaining a step of
changing the position of a semiconductor wafer with respect to a
elevating support block when a nitrogen gas is sprayed on the
semiconductor wafer; and
[0041] FIGS. 13 through 20 are graphs illustrating various ways to
adjust the concentration of IPA in a cleaning solution used for
cleaning and drying a semiconductor wafer according to an
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0042] Hereinafter, a preferred embodiment of the present invention
will be described in detail with reference to the attached
drawings.
[0043] FIG. 1 is a schematic view of an apparatus for cleaning and
drying a semiconductor wafer according to an embodiment of the
present invention. Referring to FIG. 1, the apparatus includes a
treating bath 11, a cleaning solution mixing unit 50, a cleaning
solution supplying unit 52, a return line 54, a drain line 90, and
a collecting unit 82. A wafer W is cleaned and dried in the
treating bath 11. The cleaning solution mixing unit 50 premixes
cleaning solutions to be supplied into the treating bath 11 in a
predetermined ratio. The cleaning solution supplying unit 52 moves
the cleaning solution mixed in the cleaning solution mixing unit 50
into the treating bath 11 and checks the state of the cleaning
solution. The return line 54 returns the cleaning solution, which
overflows after being used in a cleaning process in the treating
bath 11, back to the cleaning solution mixing unit 50.
[0044] If necessary, the drain line 90 returns the cleaning
solution from the treating bath 11 back to the cleaning solution
mixing unit 50. The collecting unit 82 is connected to the cleaning
solution mixing unit 50 and collects a polluted cleaning solution
to decompose the polluted cleaning solution into IPA and DIW.
[0045] The treating bath 11 may accommodate one or more wafers to
be cleaned and dried and is connected to the cleaning solution
supplying unit 52 and the return line 54. The upper portion of the
treating bath 11 is covered with a chamber cover 12 that is already
known in the prior art.
[0046] The wafer W is supported by an elevating support block 92
shown in FIG. 10 in the treating bath 11. The elevating support
block 92 is positioned inside the treating bath 11 when cleaning
the wafer W so that the wafer W is sunk under the cleaning solution
5. However, when drying the wafer W, the elevating support block 92
ascends over the treating bath 11 as shown in FIG. 11.
[0047] The chamber cover 12 covers the treating bath 11 and induces
a cleaning solution overflowing from the treating bath 11 to the
return line 54. The chamber cover 12 also includes a plurality of
nitrogen spraying nozzles 14. The nitrogen spraying nozzles 14 are
supplied with a nitrogen gas from an external source, and further
supply the nitrogen gas into the chamber cover 12 to fill the
chamber cover 12 with the nitrogen gas. In particular, the nitrogen
nozzles 14 spray the nitrogen gas on the wafer W when the wafer W
rises onto the liquid surface of the cleaning solution in order to
remove the cleaning solution attached to the surface of the wafer
W.
[0048] A heater 80 is further installed to heat the nitrogen gas
proceeding toward the nitrogen spraying nozzles 14. If necessary,
the heater 80 can heat the nitrogen gas to further effectively
remove the cleaning solution sticking to the surface of the wafer
W.
[0049] A sink 84 is installed under the treating bath 11. The sink
84 contains DIW at a predetermined wafer level so that the lower
portion of the treating bath 11 is sunk under the wafer surface of
DIW. A wafer level sensor 88 is installed inside the sink 84. The
level sensor 88 senses the level of DIW so that the lower portion
of the treating bath 11 is always positioned under the level of
DIW.
[0050] An ultrasonic generator 86 is installed beneath the sink 84.
The ultrasonic generator 86 may be a general ultrasonic generator.
Ultrasonic waves generated by the ultrasonic generator 86 pass
through DIW in the sink 84, and then are transmitted to the wafer W
through a case of the treating bath 11 and the cleaning solution
5.
[0051] In other words, when DIW is supplied into the sink 84 and
the lower portion of the treating bath 11 is dipped into DIW,
ultrasonic waves generated by the ultrasonic generator 86 are
transmitted to the treating bath 11 through DIW during cleaning of
the wafer W.
[0052] The cleaning solution mixing unit 50 includes IPA tanks 18
and 19 and mixing tanks 24 and 25 respectively connected to the IPA
tanks 18 and 19. Since the IPA tanks 18 and 19 are disposed in
parallel, IPA can be supplied simultaneously into the IPA tanks 18
and 19 from an external source. Also, since the mixing tanks 24 and
25 are disposed in parallel, DIW can be supplied simultaneously
into the mixing tanks 24 and 25 from an external source.
[0053] Each of the IPA tanks 18 and 19 has a plurality of level
sensors 20. The level sensors 20 sense the amount of IPA supplied
into the IPA tanks 18 and 19 so that the desired amount of IPA is
supplied. Each of the mixing tanks 24 and 25 also has a plurality
of level sensors 21. The level sensors 21 sense the amount of DIW
supplied into the mixing tanks 24 and 25 so that a desired amount
of DIW is supplied.
[0054] Reference numeral 44 denotes an overflow drainpipe. As will
be described later, the overflow drainpipe 44 discharges the
cleaning solution outside the mixing tanks 24 and 25 when the
cleaning solution returning back via the return line 54 or the
drain line 90 rises above a predetermined level in the mixing tanks
24 and 25.
[0055] The IPA tanks 18 and 19 are respectively connected to the
mixing tanks 24 and 25 via connecting pipes 56. Thus, IPA in the
IPA tanks 18 and 19 moves into the mixing tanks 24 and 25 through
the connecting pipes 56.
[0056] The necessary amount of DIW is separately supplied into the
mixing tanks 24 and 25. Thus, in the mixing tanks 24 and 25, IPA
supplied from the IPA tanks 18 and 19 are mixed with DIW at a
predetermined ratio. Here, the amount of IPA supplied into the IPA
tanks 18 and 19 and the amount of DIW supplied into the mixing
tanks 24 and 25 can be respectively measured by the level sensors
20 and 21. Thus, the concentration of IPA to DIW can be adjusted,
and thus cleaning solutions having a desired concentration can be
obtained in the mixing tanks 24 and 25. In other words, the
concentration of IPA illustrated in graphs of FIGS. 12 through 19
can be obtained.
[0057] Each of the connecting pipes 56 is split into two pipes. IPA
supplementing pumps 22 and 23 are respectively installed at one of
the two split connecting pipes 56. The IPA supplementing pumps 22
and 23 are used to additionally and quickly supply the accurate
amount of IPA from the IPA tanks 18 and 19 into the mixing tanks 24
and 25.
[0058] Since IPA is volatile, IPA may gradually volatilize during
the circulation of the cleaning solution. When IPA volatilizes, the
concentration of IPA in the cleaning solution becomes low. Thus,
the IPA supplementing pumps 22 and 23 supplement IPA by a shortage
of IPA.
[0059] As described above, in each of the mixing tanks 24 and 25,
IPA and DIW are mixed in a desired ratio. A nitrogen bubble
generator 26 is additionally installed in order to completely mix
IPA and DIW. The nitrogen bubble generator 26 is supplied with a
nitrogen gas from an external source, sprays the nitrogen gas into
the lower portions of the mixing tanks 24 and 25 so that DIW and
IPA contained in the mixing tanks 24 and 25 are completely
mixed.
[0060] Also, in the present embodiment, the cleaning solution
mixing unit 50 includes the IPA tanks 18 and 19 and the mixing
tanks 24 and 25. However, the number of IPA tanks and the number of
mixing tanks may increase.
[0061] The mixing tanks 24 and 25 are connected to a supplying pipe
58 via mixed solution supplying valves 28 and 29.
[0062] The mixed solution supplying valves 28 and 29 are opened
alternately not simultaneously. In other words, when the mixed
solution supplying valve 28 is opened, the mixed solution supplying
valve 29 is closed. Alternatively, when the mixed solution
supplying valve 28 is closed, the mixed solution supplying valve 29
is opened. This means that while the cleaning solution in the
mixing tank 24 is circulated and supplied into the treating bath
11, the cleaning solution in the mixing tank 25 is not circulated.
In other words, in a case where only the mixed solution supplying
valve 28 is opened to clean the wafer W using only the cleaning
solution contained in the mixing tank 24, and after a predetermined
period of time, the cleaning solution is polluted more than the
allowed pollution level, the mixed solution supplying valve 28 is
closed, the mixed solution supplying valve 29 is opened, and the
cleaning solution contained in the mixing tank 25 is circulated to
continue cleaning of the wafer W.
[0063] As described above, while the cleaning solution in the
mixing tank 25 is supplied into the treating bath 11, a mixed
solution discharging valve 30 of the mixing tank 24 is opened to
discharge the polluted cleaning solution in the mixing tank 24.
When the mixing tank 24 is completely emptied, the mixed solution
discharging valve 30 is closed, IPA and DIW are newly supplied from
external sources, IPA and DIW are mixed in a desired ratio, and the
mixture is maintained in the mixing tank 24.
[0064] By alternately using the mixing tanks 24 and 25, a pure
cleaning solution can be continuously supplied without stopping the
apparatus for cleaning and drying a semiconductor wafer. Thus, a
wafer can be quickly and effectively cleaned and dried.
[0065] Discharging pipes 64 and 65, which are respectively
installed beneath the mixing tanks 24 and 25, discharge the
cleaning solution in the mixing tanks 24 and 25 to the collecting
unit 82 and are opened and closed by the mixed solution discharging
valves 30 and 31.
[0066] The collecting unit 82 basically collects the cleaning
solution that is polluted at an allowed pollution level or above
due to the cleaning of a wafer and remakes the polluted cleaning
solution into pure IPA and DIW.
[0067] The collecting unit 82 includes a heating tank 70, which is
connected to the discharging pipes 64 and 65 and receives the
polluted cleaning solution, an IPA collecting tank 74 and a DIW
collecting tank 78, which are connected to the heating tank 70, an
IPA filter 72, which removes impurities contained in IPA flowing
from the heating tank 70 to the IPA collecting tank 74, and a DIW
filter 76, which removes impurities contained in DIW flowing from
the heating tank 70 to the DIW collecting tank 78.
[0068] The heating tank 70 receives and heats a cleaning solution
and evaporates IPA in the cleaning solution having a relatively low
boiling point to decompose the cleaning solution into DIW and IPA.
In other words, the heating tank 70 decomposes a cleaning solution
into IPA and DIW using a difference between boiling points of IPA
and DIW.
[0069] IPA turning into a gaseous state in the heating tank 70 is
filtered through the IPA filter 72, moves into the IPA collecting
tank 74, is cooled, and is condensed into a liquid state in
time.
[0070] An additional cooler may be installed to condense IPA. IPA
collected in the IPA collecting tank 74 is supplied into the IPA
tanks 18 and 19 of the cleaning solution mixing unit 50 and
reused.
[0071] After IPA flows out of the heating tank 70, polluted DIW
remains in the heating tank 70. Polluted DIW is filtered through
the DIW filter 76, and then is temporarily stored in the DIW
collecting tank 78. DIW collected in the DIW collecting tank 78 is
supplied into the mixing tanks 24 and 25 of the cleaning solution
mixing unit 50 and reused. Thus, the reuse of the cleaning solution
can save considerably the cleaning solution.
[0072] The cleaning solution supplying unit 52, which moves the
cleaning solution of a predetermined concentration supplied from
the cleaning solution mixing unit 50 into the treating bath 11,
includes a circulating pump 36, a filter 38, an IPA concentration
measurer 40, and a liquid particle counter 42.
[0073] The circulating pump 36 is connected to the mixing tanks 24
and 25 via the mixed solution supplying valves 28 and 29. The
circulating pump 36 pumps the cleaning solutions in the mixing
tanks 24 and 25 into the treating bath 11 through the cleaning
solution supplying unit 52.
[0074] The cleaning solution moving into the treating bath 11 via
the circulating pump 36 is purified through the filter 38. The
filter 38 passes the cleaning solution and filters off impurities
contained in the cleaning solution so that the usable period of the
cleaning solution is prolonged at its maximum.
[0075] The IPA concentration measurer 40 connected to the filter 38
checks the concentration of IPA in the cleaning solution that is
circulating. Since IPA is volatile, the concentration of IPA may
gradually become low during the circulation of the cleaning
solution. Due to this, the IPA concentration measurer 40 is
installed to continuously check the concentration of IPA in the
cleaning solution. When IPA measurer 40 perceives that the
concentration of IPA is reduced, the IPA supplementing pumps 22 and
23 operate to supplement IPA contained in the IPA tanks 18 and 19
into the mixing tanks 24 and 25 so that the cleaning solution
returns to an optimum concentration level.
[0076] The liquid particle counter 42 detects the amount of liquid
particle in the cleaning solution that is circulating to determine
whether the cleaning solution has to be replaced. The liquid
particle is a pollutant that is not filtered by the filter 38.
[0077] The cleaning solution supplied into the treating bath 11
through the cleaning solution supplying unit 52 cleans the wafer W
in the treating bath 11, overflows from the treating bath 11, and
flows to the return line 54.
[0078] The cleaning solution flowing through the return line 54
passes through the liquid particle counter 43 again. The liquid
particle counter 42 detects liquid particle contained in the
cleaning solution, which passed through the treating bath 11, and
rechecks the pollution level of the cleaning solution that
underwent the cleaning of the wafer W. The cleaning solution
passing through the return line 54 returns back into the mixing
tanks 24 and 25 via the return valve 60 or 61.
[0079] Drying the wafer W is accomplished by lifting the wafer W up
over the liquid surface of the cleaning solution. In other words,
when the wafer W is lifted up over the liquid surface of the
cleaning solution, drying the wafer W is firstly achieved due to
the surface tension of the cleaning solution. Next, while the wafer
W is rising, the nitrogen gas is sprayed on the wafer W through the
nitrogen nozzles 14 to secondly achieve the drying of the wafer
W.
[0080] The procedure of lifting a wafer up over the liquid surface
of a cleaning solution includes: moving the wafer over the liquid
surface of the cleaning solution using an elevating support block
92 (shown in FIG. 10) while maintaining the level of the cleaning
solution and reducing the level of the cleaning solution without
moving the wafer.
[0081] The drain line 90 is just an apparatus for reducing the
level of the cleaning solution without moving the wafer. The drain
line 90 is connected to the lower portion of the treating bath 11
and the mixing tank 24 or 25 and discharges the cleaning solution 5
in the treating bath 11 downward, so that the wafer is firstly
dried.
[0082] The drain line 90 controls the return values 60 and 61 to
return the cleaning solution back to one of the mixing tanks 24 and
25 being used.
[0083] As described above, an apparatus for cleaning and drying a
semiconductor wafer according to the present invention includes the
cleaning solution mixing unit 50, which premixes cleaning solutions
in a desired ratio, the cleaning solution supplying unit 52, which
is supplied with the cleaning solution from the cleaning solution
mixing unit 50 and supplies the cleaning solution into the treating
bath 11, and the return line 54, which returns the cleaning
solution used in the cleaning of the semiconductor wafer in the
treating bath 11 back to the cleaning solution mixing unit 50.
Thus, since the cleaning solution can be always maintained at an
accurate concentration, effects of cleaning and drying the
semiconductor wafer are good.
[0084] Since the cleaning solution discharged from the cleaning
solution mixing unit 50 returns back through the return line 50,
and then is reused to perform a cleaning process, the apparatus is
economic. In particular, the collecting unit 82 decomposes a
cleaning solution that is polluted at an allowed pollution level or
above into pure IPA and DIW. Thus, the cleaning solution can be
reused, the discarded amount of the cleaning solution can be
remarkably reduced, and environmental pollution can be reduced.
[0085] A method of cleaning and drying a semiconductor wafer using
the cleaning and drying apparatus can be basically divided into
four steps. The four steps will be described below.
[0086] In the first step, DIW and IPA are mixed. As described
above, the mixture of DIW and IPA is carried out by the cleaning
solution mixing unit 50. In other words, the mixing tanks 24 and 25
are supplied with IPA and DIW, and then IPA and DIW is completely
mixed by the nitrogen bubble generator 26.
[0087] In the second step, a cleaning solution made by mixing IPA
and DIW in the first step is supplied into the treating bath 11 so
as to contact the wafer in the treating bath 11.
[0088] The cleaning solution may contact a wafer according to two
ways. In one of the two ways, a wafer W is put into the treating
bath 11 in advance, and then a cleaning solution is supplied into
the treating bath 11 to gradually raise the liquid surface of the
cleaning solution so that the wafer W is dipped into the cleaning
solution. In the other way, when a cleaning solution is
continuously supplied into the treating bath 11 to maintain the
cleaning solution at a predetermined level, the wafer W descends to
be dipped into the cleaning solution.
[0089] FIGS. 2 and 3 illustrate a wafer W descending into a
cleaning solution.
[0090] FIG. 2 illustrates a wafer W that vertically descends, and
FIG. 3 illustrates a wafer W that descends while swaying from side
to side. When the wafer W descends while swaying from side to side,
the wafer W rubs on a cleaning solution 5, which results in an
increase in a cleaning effect.
[0091] Besides the two methods, the method of dipping a wafer into
a cleaning solution may be modified into various forms.
[0092] In order to supply a cleaning solution into the treating
bath 11 with a wafer placed in the treating bath 11 in advance so
that the wafer is dipped into the cleaning solution, the treating
bath 11 has to be pre-emptied. To empty the treating bath 11, the
drain line 90 is opened to return the cleaning solution in the
treating bath 11 back to the mixing tanks 24 and 25.
[0093] When wafer is dipped into a cleaning solution, it is
preferable that the wafer moves so as to rub the wafer on the
cleaning solution till the wafer is separated from the cleaning
solution.
[0094] FIGS. 4A through 4D illustrate a wafer that moves in the
cleaning solution.
[0095] FIG. 4A illustrates a wafer W that vertically sways, FIG. 4B
illustrates a wafer W horizontally sways, FIG. 4C illustrates a
wafer W that turns around the axis (Y-axis) of the vertical
direction, FIG. 4D illustrates a wafer W that turns around the axis
(X-axis) of the horizontal direction.
[0096] As described above, impurities such as various types of
particles can be effectively removed from the surface of a wafer by
moving the wafer within a cleansing solution.
[0097] In the third step, the wafer W is separated from a cleaning
solution 5. FIGS. 5 through 7 illustrate a method of separating the
wafer W from the cleaning solution 5.
[0098] In FIGS. 5 and 6, the wafer W is lifted up with the liquid
surface of the cleaning solution 5 maintained, and in FIG. 7, the
cleaning solution 5 is discharged with the wafer W left in the
treating bath 11. Also, in FIG. 5, the wafer W is vertically lifted
up, and in FIG. 6, the wafer W sways from side to side when being
lifted up so that the friction between the wafer W and the cleaning
solution 5 increases.
[0099] As shown in FIGS. 5 and 6, paths for taking the wafer W out
of the treating bath 11 may be changes in other various forms.
[0100] The supply of the cleaning solution 5 into the treating bath
11 has to stop and the drain line 90 has to be opened in order to
discharge the cleaning solution 5 as shown in FIG. 7. When the
drain line 90 is opened, the cleaning solution 5 in the treating
bath 11 returns back to mixing tanks that are operating.
[0101] After the wafer W is completely separated from the cleaning
solution 5, the fourth step is performed. In the fourth step, the
remaining cleaning solution is removed from the surface of the
wafer W separated from the cleaning solution 5. Also, the fourth
step is carried out in the treating bath 11 from which the cleaning
solution 5 is removed or over the treating bath 11 when the
cleaning solution 5 remains in the treating bath 11.
[0102] In the fourth step, a nitrogen gas having a high
temperature, preferably a temperature within a range of
50-150.degree. C., is sprayed on the surface of the wafer W at a
predetermined pressure so as to remove the cleaning solution
remaining on the surface of the wafer W.
[0103] FIG. 8 illustrates a state where when the wafer W is lifted
up over the treating bath 11, a hot nitrogen gas is concentratedly
sprayed on the surface of the wafer W. In this state, the remaining
cleaning solution is removed due to the pressure of spraying the
nitrogen gas and heat transmitted from the nitrogen gas.
[0104] FIG. 9 illustrates a state where a hot nitrogen gas is
sprayed on the wafer W in the vertical laminar flow. Thereafter,
the hot nitrogen gas contacts the surface of the wafer W to
transmit heat to the surface of the wafer W so that a mixed
solution is evaporated and dried.
[0105] FIGS. 10 and 13 are views for explaining a step of changing
the position of a wafer relative to an elevating support block and
side support blocks when a nitrogen gas is sprayed on the wafer. As
the elevating support block and the side support blocks, various
types of elevating support blocks and side support blocks have been
proposed.
[0106] The elevating support block 92 ascends and descends while
vertically supporting a plurality of wafers. Side support blocks 94
temporarily separate a wafer W from the elevating support block 92
when the wafer W goes up, so that a lower edge Z of the wafer W is
separated from the elevating support block 92 as shown in FIG. 12.
When the elevating support block 92 ascends, the side support
blocks 94 are fully apart from the wafer W so that the wafer W
passes through a space between the side support blocks 94.
[0107] As can seen in FIG. 10, the wafer W is dipped under the
cleaning solution 5 when being supported by the elevating support
block 92. The side support blocks 94 are positioned over the
treating bath 11. The side support blocks 94 are parallel and can
move along directions indicated by arrows. If necessary, the side
support blocks 94 support sides of the wafer W as shown in FIG.
12.
[0108] As shown in FIG. 10, when the wafer W is completely cleaned
under the cleaning solution 5, the elevating support block 92 goes
up in direction U indicated by arrow so that the wafer W is
separated from the cleaning solution 5. Thereafter, a nitrogen gas
is sprayed on the wafer W.
[0109] Referring to FIG. 11, the elevating support 92 completely
moves up over the treating bath 11 and the wafer W is positioned
between the-side support blocks 94. Here, since the lower edge Z of
the wafer W contacts the elevating support block 92, the nitrogen
gas does not reaches the lower edge Z, and thus the lower edge Z is
not completely dried. Thus, the side support blocks 94 moves along
direction A indicated by arrow so as to support the sides of the
wafer W, while the elevating support block 92 temporarily descends
as shown in FIG. 12.
[0110] Referring to FIG. 12, the side support blocks 94 support the
sides of the wafer W and the elevating support block 92 goes down,
so that the nitrogen gas is sprayed on the lower edge Z. Here, the
elevating support block 92 must not sink under the cleaning
solution 5.
[0111] When the wafer W is completely dried, the elevating support
92 ascends and the side support blocks 94 are separated from the
wafer W so that the elevating support block 92 re-supports the
wafer W, and then the wafer W is taken out from the elevating
support block 92.
[0112] Finally, a wafer is completely cleaned and dried through the
first through fourth steps.
[0113] FIGS. 13 through 20 are graphs illustrating ways to adjust
the concentration of IPA with respect to variations in the time
required for supplying a cleaning solution into a treating bath.
When the concentration of IPA is properly adjusted to work
conditions or other requirements, an improved cleaning effect can
be achieved. In addition, the adjustment of the concentration of
IPA can be realized by the IPA supplementing pumps 22 and 23
described with reference to FIG. 1.
[0114] FIG. 13 illustrates a state where a cleaning solution
containing IPA and DIW of a predetermined ratio is supplied into a
treating bath without varying the concentration of IPA.
[0115] FIG. 14 illustrates a state where when only DIW is first
supplied into a treating bath, and then the addition of IPA to DIW
is gradually increased and the concentration of IPA reaches a
predetermined level, the supply of IPA stops.
[0116] FIG. 15 illustrates a state where when the concentration of
IPA of a cleaning solution supplied into a treating bath is
gradually increased and reaches a predetermined level, the addition
of IPA stops.
[0117] FIG. 16 illustrates a state where the concentration of IPA
to DIW is increased at regular intervals not gradually.
[0118] FIG. 17 illustrates a state where only pure IPA is first
supplied into a treating bath, and then DIW is supplied into the
treating bath at predetermined time intervals, so that the
concentration of IPA becomes low.
[0119] FIG. 18 illustrates a state where a cleaning solution
containing IPA of a predetermined concentration is supplied into a
treating bath, and then the addition of IPA is reduced from a
predetermined point of time, so that only DIW is supplied.
[0120] FIG. 19 illustrates a state where a cleaning solution
containing IPA of a predetermined concentration is first supplied
into a treating bath, and then the addition of IPA is gradually
increased, so that the concentration of IPA becomes higher.
[0121] FIG. 20 illustrates a state where a cleaning solution
containing IPA of a predetermined concentration is first supplied
into a treating bath, and then the addition of IPA is gradually
reduced, so that the concentration of IPA becomes lower.
[0122] In an apparatus and method for cleaning and drying a
semiconductor wafer according to the present invention, before DIW
and IPA are supplied into a treating bath, IPA and DIW are
completely mixed so that cleaning and drying works are effectively
performed. Also, a cleaning solution can be reused to prevent waste
of the cleaning solution.
[0123] In addition, the semiconductor wafer is taken as an example
of an object to be cleaned. However, the object to be cleaned is
not limited to the semiconductor wafer, and the present invention
may be applied to various objects including a substrate for a
liquid crystal display device only, a substrate for a recording
disc only, a substrate for a mask only, or the like.
[0124] While the present invention has been particularly shown and
described with reference to exemplary embodiments thereof, it will
be understood by those of ordinary skill in the art that various
changes in form and details may be made therein without departing
from the spirit and scope of the present invention as defined by
the following claims.
* * * * *