U.S. patent application number 10/795434 was filed with the patent office on 2004-09-16 for apparatus for cleaning a substrate having metal interconnects.
Invention is credited to Hamada, Satomi, Ito, Kenya, Kamezawa, Masayuki, Katakabe, Ichiro, Kodera, Masako.
Application Number | 20040177655 10/795434 |
Document ID | / |
Family ID | 32767923 |
Filed Date | 2004-09-16 |
United States Patent
Application |
20040177655 |
Kind Code |
A1 |
Kodera, Masako ; et
al. |
September 16, 2004 |
Apparatus for cleaning a substrate having metal interconnects
Abstract
The present invention relates to a cleaning apparatus which can
reduce a potential difference between metals or alloys used to form
interconnects on a substrate for thereby minimizing corrosion which
may occur during and after a substrate cleaning process. The
cleaning apparatus for cleaning a substrate having metal
interconnects comprises a cleaning mechanism for cleaning the
substrate, and a functional water supply mechanism for supplying
functional water to the cleaning mechanism. The cleaning mechanism
cleans a surface of the substrate with use of the functional
water.
Inventors: |
Kodera, Masako; (Tokyo,
JP) ; Ito, Kenya; (Tokyo, JP) ; Kamezawa,
Masayuki; (Tokyo, JP) ; Hamada, Satomi;
(Tokyo, JP) ; Katakabe, Ichiro; (Tokyo,
JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
32767923 |
Appl. No.: |
10/795434 |
Filed: |
March 9, 2004 |
Current U.S.
Class: |
68/19 |
Current CPC
Class: |
H01L 21/67057 20130101;
B08B 3/02 20130101; H01L 21/67219 20130101; C23G 3/00 20130101;
B08B 1/04 20130101; H01L 21/67173 20130101; B08B 3/12 20130101;
B08B 3/04 20130101; B08B 3/08 20130101; H01L 21/67046 20130101;
H01L 21/67051 20130101 |
Class at
Publication: |
068/019 |
International
Class: |
D06F 029/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 12, 2003 |
JP |
2003-65845 |
Claims
What is claimed is:
1. A cleaning apparatus for cleaning a substrate having metal
interconnects, comprising: a cleaning mechanism for cleaning the
substrate; and a functional water supply mechanism for supplying
functional water to said cleaning mechanism; wherein said cleaning
mechanism cleans a surface of the substrate with use of the
functional water.
2. A cleaning apparatus according to claim 1, wherein said
functional water supply mechanism produces gas-dissolved water as
the functional water.
3. A cleaning apparatus according to claim 1, wherein said
functional water supply mechanism comprises a water electrolyzing
device for electrolyzing water to produce electrolytic water as the
functional water.
4. A cleaning apparatus according to claim 2, wherein said
functional water supply mechanism comprises a water electrolyzing
device for electrolyzing water to produce electrolytic water as the
functional water.
5. A cleaning apparatus according to claim 1, wherein said cleaning
mechanism comprises at least one of a mechanism having a cleaning
member for scrubbing the surface of the substrate, a mechanism
having a cleaning member which is rotated on the surface of the
substrate, a mechanism for applying an ultrasonic wave to the
functional water, a mechanism for generating cavitation in the
functional water, and a mechanism for generating cavitation in the
functional water and applying an ultrasonic wave to the functional
water.
6. A cleaning apparatus according to claim 1, wherein metal or ally
for forming the metal interconnects contains at least one of
aluminum, tungsten, and titanium nitride.
7. A cleaning apparatus according to claim 2, wherein the
functional water comprises gas-dissolved water containing at least
one of CO.sub.2 and O.sub.3.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a cleaning apparatus for
cleaning a substrate having metal interconnects for use in a
precision electronic component such as a semiconductor device, and
more particularly to a cleaning apparatus which can reduce a
potential difference between metals or alloys used to form
interconnects on a substrate for thereby minimizing corrosion which
may occur during and after a substrate cleaning process.
[0003] 2. Description of the Related Art
[0004] Aluminum (Al) has been widely used as an interconnect
material in a semiconductor device. Aluminum or aluminum alloy is a
base metal having an extremely low potential compared with other
metals (see "Metal Guidebook", p 877, edited by The Japan Institute
of Metals). Accordingly, when aluminum or aluminum alloy is used in
combination with copper (Cu), tungsten (W), titanium (Ti), or their
alloy, such aluminum or aluminum alloy is highly liable to suffer
corrosion due to potential difference.
[0005] For example, Al--Cu alloy (aluminum and a small amount of
copper added thereto) that is generally used in a semiconductor
device has a surface potential of -730 mV (with respect to Ag/AgCl)
in pure water. On the other hand, tungsten (W) has a surface
potential of about -500 mV, titanium nitride (TiN) has a surface
potential of -430 mV, and copper (Cu) has a surface potential of
about -100 mV. Consequently, the potential difference of 200 mV or
more is generated between Al--Cu alloy and tungsten, the potential
difference of 300 mV or more is generated between Al--Cu alloy and
titanium nitride, and the potential difference of 600 mV is
generated between Al--Cu alloy and copper.
[0006] Tungsten is widely used as a filling material for contact
holes. Tungsten alloy and titanium alloy are used as a barrier
metal, and copper is used as a main material for forming
interconnects. Therefore, if aluminum or aluminum alloy which
basically comprises Al--Cu, and the above metal such as tungsten,
titanium, or copper, or their alloys are simultaneously exposed on
a surface of a semiconductor device and such a semiconductor device
is processed, aluminum or aluminum alloy which basically comprises
Al--Cu is highly likely to suffer corrosion.
[0007] For example, in the case of forming aluminum interconnects
by a damascene process, interconnect grooves are first formed on a
surface of a silicon wafer, and then a metal serving as a barrier
metal such as TiN and Ti is deposited on the surface of the silicon
wafer by a sputtering process or the like to form a thin film,
e.g., a laminated film of TiN and Ti. Thereafter, aluminum is
deposited by a sputtering process or the like to form an aluminum
film having a thickness greater than the depth of the interconnect
grooves. Subsequently, aluminum and the barrier metal deposited on
convex portions of the surface of the silicon wafer are removed by
a CMP (Chemical Mechanical Polishing or Chemical Mechanical
Planarization) process so as to allow aluminum and the barrier
metal to remain only in the interconnect grooves, thereby forming
aluminum interconnects.
[0008] After the CMP process, the silicon wafer having the aluminum
interconnects is cleaned by a cleaning process. However, there
arises a problem that the aluminum interconnects are corroded in
the cleaning process. Specifically, the silicon wafer is generally
cleaned with pure water. When the pure water is supplied to the
aluminum interconnects and the barrier metal during the cleaning
process, the aluminum interconnects suffer a serious problem in
that the aluminum interconnects are corroded and dissolved due to
the potential difference between the aluminum interconnects and the
barrier metal which have been joined to each other. Such a problem
is reported in a document titled "Met. Res. Soc. Symp. Proc.", Vol.
671, 2001, --Control of Pattern Specific Corrosion During Aluminum
Chemical Mechanical Polishing--, written by H. Kim et. al.
[0009] Further, when aluminum interconnects are formed by an RIE
(Reactive Ion Etching) process, it is necessary to remove residues,
which remain on the substrate after the RIE process and a resist
removing process, with use of a chemical liquid in a subsequent
cleaning process. In this cleaning process also, the aluminum
interconnects are corroded and dissolved because the aluminum
interconnects and the barrier metal are simultaneously brought into
contact with the chemical liquid and pure water that is used as a
rinsing liquid.
[0010] If circuit interconnects formed on the substrate have a
large width, the above problem of corrosion is not so serious.
However, if the substrate has fine circuit interconnects thereon,
then the corrosion may cause defects such as disconnection, and
hence the above problem becomes serious.
SUMMARY OF THE INVENTION
[0011] Therefore, there has been demand for a cleaning apparatus
which can prevent interconnects made of aluminum or aluminum alloy
on a substrate from being corroded, and it is an object of the
present invention to provide such a cleaning apparatus.
[0012] Inventors of the present invention have made diligent
studies in order to solve a problem of corrosion which occurs
during a cleaning process of a substrate due to a potential
difference between an interconnect metal such as aluminum or the
like and a barrier layer metal on the substrate. As a result, the
inventors have found that the potential difference between the
interconnect metal and the barrier layer metal can be reduced by
using various types of functional waters as cleaning waters for
cleaning the substrate instead of using pure water, and have
completed the present invention based on the findings in that the
functional waters are effective to prevent the corrosion from
proceeding.
[0013] According to an aspect of the present invention, there is
provided a cleaning apparatus for cleaning a substrate having metal
interconnects, comprising: a cleaning mechanism for cleaning the
substrate; and a functional water supply mechanism for supplying
functional water to the cleaning mechanism; wherein the cleaning
mechanism cleans a surface of the substrate with use of the
functional water.
[0014] In a preferred aspect of the present invention, the
functional water supply mechanism produces gas-dissolved water as
the functional water.
[0015] In a preferred aspect of the present invention, the
functional water supply mechanism comprises a water electrolyzing
device for electrolyzing water to produce electrolytic water as the
functional water.
[0016] In a preferred aspect of the present invention, the cleaning
mechanism comprises at least one of a mechanism having a cleaning
member for scrubbing the surface of the substrate, a mechanism
having a cleaning member which is rotated on the surface of the
substrate, a mechanism for applying an ultrasonic wave to the
functional water, a mechanism for generating cavitation in the
functional water, and a mechanism for generating cavitation in the
functional water and applying an ultrasonic wave to the functional
water.
[0017] In a preferred aspect of the present invention, metal or
ally for forming the metal interconnects contains at least one of
aluminum, tungsten, and titanium nitride.
[0018] In a preferred aspect of the present invention, the
functional water comprises gas-dissolved water containing at least
one of CO.sub.2 and O.sub.3.
[0019] The functional water used as cleaning water comprises pure
water in which a predetermined gas such as CO.sub.2 gas or O.sub.3
gas is dissolved.
[0020] The functional water can be produced by an electrolyzing
process in which ultrapure water is electrolyzed without the
addition of an electrolyte, and a gas-dissolving process in which a
gas is dissolved in pure water with use of a gas-insufflating
filter.
[0021] Examples of the functional water produced by the
electrolyzing process include oxygen-gas-dissolved water (anode
water) produced in an anode side and hydrogen-gas-dissolved water
(cathode water) produced in a cathode side. The
oxygen-gas-dissolved water produced in the anode side has a pH
ranging from 6 to 7 and an oxidation-reduction potential ranging
from 200 to 300 mV. The hydrogen-gas-dissolved water produced in
the cathode side has a pH ranging from 7 to 8 and an
oxidation-reduction potential ranging from -500 to -700 mV.
[0022] In the gas-dissolving process, a predetermined gas is blown
into pure water to be dissolved therein, thus producing
gas-dissolved water such as oxygen-gas-dissolved water,
hydrogen-gas-dissolved water, and other-gas-dissolved water.
[0023] Examples of a gas to be dissolved include a carbon dioxide
gas, an ozone gas, an ammonia gas, a hydrochloric acid gas, and the
like, and two or more of these gases can be blown into pure
water.
[0024] A potential of a metal used to form interconnects on a
substrate can be shifted by using the functional water which has
been thus produced. For example, although aluminum dipped in pure
water has a surface potential of -1120 mV, aluminum dipped in
gas-dissolved water containing an oxygen gas at saturated
concentration has a surface potential of about -310 mV. In this
manner, the surface potential of aluminum can be greatly shifted in
the noble direction. Even if aluminum is dipped in gas-dissolved
water containing an oxygen gas at non-saturated concentration, the
surface potential of aluminum can be shifted in the noble
direction.
[0025] When aluminum is dipped in hydrogen-gas-dissolved water
having saturated concentration which is produced in the same
process, the surface potential of aluminum is -770 mV, which is not
shifted greatly. However, when aluminum is dipped in a liquid
comprising a mixture of the oxygen-gas-dissolved water having
saturated concentration and the hydrogen-gas-dissolved water having
saturated concentration, the surface potential of aluminum is in
the range of -200 to -300 mV, which is greatly shifted to the noble
direction. In the case of using gas-dissolved water produced by
blowing a gas with use of a gas-insufflating filter, the same
result as described above can also be obtained. Even if
oxygen-gas-dissolved water and hydrogen-gas-dissolved water each
having non-saturated concentration are used, the surface potential
of aluminum can be shifted in the noble direction.
[0026] As described above, it is possible to use functional water
produced by blowing a gas other than oxygen and hydrogen, and one
example of such functional water is carbon-dioxide-gas-dissolved
water. The carbon-dioxide-gas-dissolved water does not have an
ability to greatly shift the surface potential of aluminum.
However, the carbon-dioxide-gas-dissolved water is practical for
use because the carbon-dioxide-gas-dissolved water having a
concentration of 3 ppm is capable of shifting the surface potential
of aluminum, tungsten, tungsten alloy, titanium, and titanium alloy
in the noble direction by a maximum of about 100 mV.
[0027] From the viewpoint of the potential difference between
aluminum and another metal, the potential differences between
aluminum and titanium and between aluminum and titanium alloy are
minimized when using the oxygen-gas-dissolved water or a mixture of
the oxygen-gas-dissolved water and the hydrogen-gas-dissolved
water. Similarly, the oxygen-gas-dissolved water or a mixture of
the oxygen-gas-dissolved water and the hydrogen-gas-dissolved water
is effective for aluminum.
[0028] The gas-dissolved water including the functional water of
the present invention has already been used to clean a substrate.
For example, there has been known a process for cleaning a
substrate with use of an aqueous solution in which any one of an
hydrogen gas, a reducing gas, or an ozone gas is dissolved for the
purpose of removing particles from the substrate after a resist
removing process or the purpose of removing a metal impurity
attached on the substrate. Such a process for cleaning the
substrate with use of the aqueous solution is disclosed in the
following documents: Japanese laid-open patent publication No.
10-64867, Japanese laid-open patent publication No. 10-172941,
Japanese laid-open patent publication No. 2001-326209, Japanese
laid-open patent publication No. 2002-100599, and Japanese
laid-open patent publication No. 2002-118085.
[0029] However, the above documents do not disclose a process for
cleaning a substrate having interconnects formed thereon, and do
not suggest a method of controlling the potential difference
between two or more metals or alloys for forming interconnects.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a schematic view showing a basic structure of a
cleaning apparatus according to a first embodiment of the present
invention;
[0031] FIG. 2 is a schematic view showing a basic structure of a
cleaning apparatus according to a second embodiment of the present
invention;
[0032] FIG. 3 is cross-sectional view showing an example of a
cleaning module having a batch-type dipping container;
[0033] FIG. 4 is a schematic view showing an example of a
spray-type cleaning module;
[0034] FIG. 5 is a schematic view showing a gas-dissolved-water
producing unit;
[0035] FIG. 6 is a schematic view showing an electrolytic water
producing unit;
[0036] FIG. 7 is a schematic view showing an example of a
cleaning/drying module for performing a roll cleaning process while
holding and rotating a substrate;
[0037] FIG. 8A is a perspective view showing another example of a
cleaning/drying module for cleaning a substrate by supplying
functional water as cleaning water;
[0038] FIG. 8B is a perspective view showing an essential part of
the cleaning/drying module shown in FIG. 8A;
[0039] FIG. 9 is a perspective view showing another example of a
cleaning/drying module having a pencil-type cleaner;
[0040] FIG. 10A is a schematic view showing a polishing apparatus
which incorporates a cleaning apparatus according to the present
invention; and
[0041] FIG. 10B is a perspective view showing an essential part of
the-polishing apparatus shown in FIG. 10A.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0042] A cleaning apparatus for cleaning a substrate having metal
interconnects formed thereon according to embodiments of the
present invention will be described below.
[0043] FIG. 1 is a schematic view showing a basic structure of a
cleaning apparatus according to a first embodiment of the present
invention. As shown in FIG. 1, a cleaning apparatus comprises a
cleaning unit 1 serving as a cleaning mechanism, a functional water
producing unit 2 serving as a functional water supply mechanism, a
chemical liquid supply unit 3, a controller 4, a pair of functional
water supply pipes 21a, 21b, a pair of flow meters 22a, 22b, a pair
of valves 23a, 23b, and a chemical liquid supply pipe 29. The
cleaning unit 1 comprises a loading/unloading unit 11, a chemical
processing module 12, a cleaning/drying module 13, and a transfer
module 14.
[0044] A substrate to be cleaned is introduced into the cleaning
unit 1 through the loading/unloading unit 11. The substrate is
processed, e.g. etched, in the chemical processing module 12, and
is then cleaned and dried in the cleaning/drying module 13. The
substrate which has been cleaned and dried is transferred to a
subsequent process by the transfer module 14.
[0045] Specifically, a substrate having metal interconnects formed
thereon is transferred to the chemical processing module 12, and is
processed by a chemical liquid such as an etching liquid or a
cleaning liquid that is supplied from the chemical liquid supply
unit 3 through the chemical liquid supply pipe 29.
[0046] The substrate having the metal interconnects, which is an
object to be cleaned, is then transferred to the cleaning/drying
module 13. In the cleaning/drying module 13, the substrate is
cleaned by functional water. The functional water is produced by
the functional water producing unit 2 and supplied to the
cleaning/drying module 13 through the functional water supply pipes
21a, 21b, the flow meters 22a, 22b, and the valves 23a, 23b. The
valves 23a, 23b are controlled by the controller 4 so that the
valves 23a, 23b are selectively opened and closed at an appropriate
timing. In this cleaning process, it is possible to use not only a
single type of functional water, but also several types of
functional waters as cleaning waters.
[0047] For example, anode water may be used as first functional
water, and then a mixture of anode water and cathode water may be
used as second functional water. In such a case, first, the anode
water and the cathode water as functional water are produced by the
functional water producing unit 2. Then, only the anode water is
supplied to the substrate through the functional water supply pipe
21a, the flow meter 22a, and the valve 23a, thereby cleaning the
substrate for a predetermined period of time. Thereafter, the
cathode water is supplied to the substrate through the functional
water supply pipe 21b, the flow meter 22b, and the valve 23b,
thereby cleaning the substrate. The types of the functional waters
are not limited to the above case. For example, a combination of
pure water and anode water or cathode water, a combination of anode
water and cathode water, or a combination of electrolytic water
such as anode water or cathode water and gas-dissolved water which
is produced by introducing a gas into pure water may be used as the
functional water.
[0048] Examples of a cleaning process using the functional water
include a roll cleaning process in which a cleaning member scrubs
the surface, to be cleaned, of the substrate, a pencil cleaning
process in which a cleaning member is rotated on the surface, to be
cleaned, of the substrate, a cavitation ultrasonic cleaning
process, and a combination of these processes.
[0049] The cleaning/drying module 13 performs a contact-type
cleaning process such as a roll cleaning process, a dipping process
for dipping one or more substrates in the functional water held in
a cleaning container (not shown), or a non-contact-type rinsing
process for supplying the functional water to a surface, to be
cleaned, of a substrate that is held by a substrate holding
mechanism (not shown).
[0050] The supply of the chemical liquid, and the supply and
switching of the cleaning water (the functional water) depending on
a type of metal used for forming the interconnects on the surface
of the substrate can be performed at appropriate timings by signals
from the controller 4. The combination of the cleaning waters can
be also made in appropriate composition by signals from the
controller 4.
[0051] FIG. 2 is a schematic view showing a basic structure of a
cleaning apparatus according to a second embodiment of the present
invention. Structure and operation of the cleaning apparatus
according to the second embodiment which will not be described
below are identical to those of the cleaning apparatus according to
the first embodiment.
[0052] As shown in FIG. 2, the cleaning apparatus comprises
connecting pipes 26a, 26b, flow meters 24a, 24b, and valves 25a,
25b. The connecting pipes 26a, 26b connect the functional water
supply pipes 21a, 21b and the chemical liquid supply pipe 29 to
each other, and the flow meters 24a, 24b and the valves 25a, 25b
are provided on the connecting pipes 26a, 26b, respectively. With
this structure, the functional waters produced by the functional
water producing unit 2 are supplied into the chemical liquid supply
pipe 29 through the connecting pipes 26a, 26b, the flow meters 24a,
24b, and the valves 25a, 25b. The valves 25a, 25b are controlled by
the controller 4 so that several types of the functional waters are
selectively supplied into the chemical liquid supply pipe 29
through the connecting pipes 26a, 26b.
[0053] According to the cleaning apparatus shown in FIG. 2, it is
possible to add the functions of the functional waters to the
chemical liquid for thereby achieving a preferable processing
condition, e.g., a preferable etching condition. As with the first
embodiment, the supply of the chemical liquid, and the supply and
switching of the functional water (the cleaning water) can be
performed at appropriate timings by signals from the controller 4.
The selection of the functional water to be added to the chemical
liquid can be also performed by signals from the controller 4 to
make appropriate composition.
[0054] An example of a cleaning apparatus for cleaning a substrate
having metal interconnects according to the present invention
comprises a substrate holding mechanism, a cleaning mechanism for
cleaning the substrate, and a functional water supply mechanism for
supplying functional water to the cleaning mechanism. The cleaning
mechanism cleans a surface of the substrate with use of the
functional water.
[0055] In this cleaning apparatus, the substrate having the metal
interconnects formed on its surface is held by the substrate
holding mechanism, and is transferred to the cleaning mechanism.
The substrate holding mechanism is operable to move the substrate
in an appropriate manner as needed while holding the substrate
firmly. Specifically, the substrate holding mechanism may be
operable to turn the substrate which has the metal interconnects
formed on the surface thereof from a horizontal attitude to a
vertical attitude, or may be operable to rotate the substrate about
its own axis and move the substrate in a horizontal plane.
[0056] A substrate to be cleaned may be placed in a dipping
container, and functional water may be supplied into the dipping
container to clean the substrate. FIG. 3 is cross-sectional view
showing an example of a cleaning module having a batch-type dipping
container which is incorporated in the cleaning unit. As shown in
FIG. 3, a cleaning module 30 comprises a dipping container 31, and
a functional water supply nozzle 32 disposed above the dipping
container 31. A drain pipe 34 is connected to a bottom of the
dipping container 31, and a valve 33 is provided on the drain pipe
34. A substrate holder 35 for holding a plurality of substrates W
is disposed in the dipping container 31. In the cleaning module 30
having the above structure, the plurality of substrates W are held
by the substrate holder 35, and then the valve 33 is closed.
Functional water is supplied from the functional water
supply-nozzle 32 into the dipping container 31 until the substrates
W are fully dipped in the functional water. The substrates W are
kept being dipped in the functional water for a predetermined
period of time. During this period of time, an upper open end 31a
of the dipping container 31 may be hermetically closed or covered
with a lid (not shown). Alternatively, the functional water may be
overflowed from the dipping container 31. Particularly, if the
functional water comprises hydrogen-gas-dissolved water, the
hydrogen-gas-dissolved water should preferably be overflowed from
the dipping container 31 because hydrogen tends to be easily
released from the water. Ultrasonic vibrators 36 may be provided in
the dipping container 31 so that ultrasonic waves are applied to
the functional water for thereby increasing a cleaning efficiency.
In FIG. 3, the drain pipe 34 is connected to the bottom of the
dipping container 31. However, the dipping container 31 may be
constructed so as to allow the functional water to be overflowed
from the upper open end 31a. In this case, a stock container (not
shown) for temporarily holding the functional water which has
overflowed from the dipping container 31 may be provided.
[0057] FIG. 4 is a schematic view showing an example of a
spray-type cleaning module which is incorporated in the cleaning
unit. As shown in FIG. 4, a cleaning module 37 comprises a
plurality of nozzles 38a, 38b. The nozzles 38a are disposed above a
plurality of substrates W which have been transferred by a transfer
mechanism (not shown), and the nozzles 38b are disposed below the
substrates W. Functional waters are supplied from the nozzles 38a,
38b to the substrates W to clean the substrates W. The nozzles 38a,
38b may supply the functional water in the form of a liquid shower
or in the form of a mist spray. Either the substrates W or the
nozzles 38a, 38b or both the substrates W and the nozzles 38a, 38b
may be moved relatively to each other during the cleaning process.
Alternatively, both the substrates W and the nozzles 38a, 38b may
not be moved.
[0058] FIG. 5 is a schematic view showing a gas-dissolved-water
producing unit for producing gas-dissolved-water as an example of
the functional water producing unit 2. As shown in FIG. 5, a
gas-dissolved-water producing unit 40 comprises a gas dissolving
device 42. A predetermined gas is supplied to the gas dissolving
device 42 through a gas supply pipe 44 and pure water is also
supplied to the gas dissolving device 42 through a pure water
supply pipe 45. The gas dissolving device 42 mixes the gas and the
pure water to produce gas-dissolved water serving as functional
water, which is supplied to the cleaning unit 1 (see FIG. 1 or FIG.
2) through a gas-dissolved-water supply pipe 41. The gas dissolving
device 42 comprises a gas dissolving membrane in the form of a
hollow yarn membrane made of polytetrafluoroethylene. The gas
supply pipe 44 is connected to a gas container 48 such as a
hydrogen gas container or an oxygen gas container. A pressure meter
47a is provided on the gas supply pipe 44, although it is possible
to dispense with the pressure meter 47a. A pressure meter 47b is
provided on the pure water supply pipe 45, and a flow meter 43 for
measuring a flow rate of the gas-dissolved water is provided on the
gas-dissolved water supply pipe 41. It is also possible to dispense
with the pressure meter 47b and the flow meter 43. A drain pipe 46
is connected to the gas dissolving device 42 for discharging the
pure water and the gas from the gas dissolving device 42.
[0059] In the gas-dissolved-water producing unit 40, the pure water
and the gas are brought into contact with each other through the
gas dissolving membrane to produce the gas-dissolved water. In the
gas dissolving device 42, the gas and the pure water should
preferably flow countercurrently.
[0060] When the pure water and the gas are brought into contact
with each other, the pressure of the pure water should preferably
be slightly higher than the pressure of the gas because it is
possible to prevent gas bubbles from being produced in the vicinity
of the gas dissolving membrane, thereby easily controlling the
concentration of the gas which is dissolved in the pure water. In
the gas-dissolved-water producing unit 40 shown in FIG. 5, the gas
is supplied from the gas container 48. However, the gas may be
supplied from a pipe system in a plant.
[0061] FIG. 6 is a schematic view showing an electrolytic water
producing unit as another example of the functional water producing
unit 2. An electrolytic water producing unit 50 serving as a water
electrolyzing device comprises an electrolytic bath 51 for holding
water, e.g., pure water or ultrapure water, which is divided into
two regions by an ion exchange membrane 54. An anode electrode 52
is disposed in one of the regions, and a cathode electrode 53 is
disposed in the other. A power supply 58 is connected to the anode
electrode 52 and the cathode electrode 53 for electrolyzing the
water held in the electrolytic bath 51. An anode water pipe 56 is
connected to the electrolytic bath 51 for extracting anode water
which has been produced in the electrolytic bath 51, and a cathode
water pipe 57 is connected to the electrolytic bath 51 for
extracting cathode water which has been produced in the
electrolytic bath 51. A deionized water supply pipe 55 is connected
to the electrolytic bath 51 for supplying deionized water, e.g.,
pure water or ultrapure water, into the electrolytic bath 51 so as
to compensate for a shortage of water in the electrolytic bath
51.
[0062] The ion exchange membrane 54 may comprise a cation exchange
membrane or an anion exchange membrane. However, the ion exchange
membrane 54 should preferably comprise a cation exchange membrane.
Each of the anode electrode 52 and the cathode electrode 53 should
preferably comprise an electrode made of insoluble metal such as
platinum or titanium, or an electrode whose surface is covered with
such insoluble metal.
[0063] When the cleaning apparatus described above is used to clean
a substrate having aluminum interconnects after the substrate is
polished by a CMP process, operation is carried out as follows: The
substrate which has been polished by the CMP process using slurry
is water-polished using the functional water immediately after the
CMP process. Thereafter, the substrate is cleaned with use of one
or more scrubbers, rolls, or pencil-type cleaners. Alternatively,
the substrate is cleaned by a non-contact-type cleaning process
such as a rinsing process. In the scrubbing and/or the rinsing
process, it is effective to use the functional water.
[0064] If oxygen-gas-dissolved water and hydrogen-gas-dissolved
water are used as functional water, aluminum interconnects can be
prevented from being corroded substantially completely.
[0065] If the present invention is applied to clean a substrate
having aluminum interconnects after a RIE process, it is effective
to use oxygen-gas-dissolved water or both oxygen-gas-dissolved
water and hydrogen-gas-dissolved water in order to prevent the
aluminum interconnects from being corroded.
[0066] FIG. 7 is a schematic view showing an example of a
cleaning/drying module incorporated in the cleaning apparatus
according to the first or second embodiment of the present
invention. A cleaning/drying module 70 shown in FIG. 7 performs a
roll cleaning process while holding and rotating a substrate having
interconnects. As shown in FIG. 7, the cleaning/drying module 70
comprises a plurality of rollers 73a, 73b for holding and rotating
a substrate W, a plurality of roll-shaped cleaning members 74a, 74b
for cleaning the substrate W, functional water supply nozzles 75a,
75b for supplying functional water to the substrate W and chemical
liquid supply nozzles 76a, 76b for supplying a chemical liquid such
as an etching liquid or a chemical cleaning liquid to the substrate
W. The rollers 73a, 73b hold a circumferential edge of the
substrate W and rotate the substrate W about its own axis in a
horizontal plan. The roll-shaped cleaning members 74a, 74b are
brought into contact with an upper surface and a lower surface of
the substrate W, respectively, and are rotated about their own axes
to scrub the upper surface and the lower surface of the substrate
W. Each of the roll-shaped cleaning members 74a, 74b comprises a
PVA sponge roll, for example. The functional water supply nozzles
75a, 75b are disposed above and below the substrate W,
respectively. The chemical liquid supply nozzles 76a, 76b are also
disposed above and below the substrate W, respectively. Necessary
functional water is supplied from the functional water supply
nozzles 75a, 75b to the substrate W. Necessary chemical liquid is
supplied from the chemical liquid supply nozzles 76a, 76b to the
substrate W. The functional water should preferably be supplied
from the functional water supply nozzles 75a, 75b as quickly as
possible after the functional water is produced by the functional
water producing unit 2 (see FIG. 1 or FIG. 2) in order to prevent
the functional water from being deteriorated, i.e., being reduced
in concentration. For this reason, a pipe for interconnecting the
functional water producing unit 2 and the cleaning/drying module 70
should be as short in length as possible. Furthermore, this pipe
should preferably be made of polytetrafluoroethylene.
[0067] Ultrasonic vibrators 77 may be provided on the respective
functional water supply nozzles 75a, 75b as needed. Each of the
ultrasonic vibrators 77 applies ultrasonic energy to the functional
water to increase a cleaning capability. If necessary, the
functional water producing unit 2 (see FIG. 1 or FIG. 2) should
preferably have a measuring device (not shown) for measuring and
monitoring properties such as a pH and an ion concentration of the
functional water and a control device (not shown) for controlling
such properties based on values measured by the measuring
device.
[0068] FIG. 8A is a perspective view showing another example of a
cleaning/drying module incorporated in the cleaning apparatus
according to the first or second embodiment of the present
invention. FIG. 8B is a perspective view showing an essential part
of the cleaning/drying-module shown in FIG. 8A. A cleaning/drying
module 80 shown in FIGS. 8A and 8B has a mechanism for cleaning a
substrate W by supplying a cleaning liquid onto the substrate W. As
shown in FIGS. 8A and 8B, the cleaning/drying module 80 comprises a
plurality of substrate holding arms 84 for holding the substrate W,
a rotational table 86 for rotating the substrate W, a liquid supply
nozzle 82 for supplying a liquid onto the substrate W, a swing arm
87 which performs a swinging motion, and a gas supply nozzle 88 for
supplying a gas to the substrate W so as to dry the substrate
W.
[0069] In the cleaning/drying module 80, the substrate W is held by
the substrate holding arms 84 and rotated by the rotational table
86 which is rotatable at a high rotational speed. The liquid supply
nozzle 82 is mounted on the swing arm 87. A chemical liquid such as
an etching liquid or a chemical cleaning liquid is supplied from
the liquid supply nozzle 82 to the upper surface of the substrate
W, thereby processing the substrate W. In addition, functional
water as a cleaning liquid or a rinsing liquid is also supplied
from the liquid supply nozzle 82 to the upper surface of the
substrate W, thereby cleaning the substrate W. If necessary, the
chemical liquid, the functional water, and the rinsing liquid are
vibrated by ultrasonic wave having a high frequency in the range of
several tens kHz to 5 MHz.
[0070] The liquid supply nozzle 82 may comprise a nozzle for
supplying the above liquid having a high pressure in the range of
1.times.10.sup.6 to 5.times.10.sup.6 Pa. Alternatively, the liquid
supply nozzle 82 may comprise a low-pressure-liquid nozzle and a
high-pressure-liquid nozzle disposed centrally in the
low-pressure-liquid nozzle for generating cavitation due to shear
between a high-pressure liquid and a low-pressure liquid ejected
from the respective nozzles. In this case, the high-pressure liquid
has a pressure ranging from 1.times.10.sup.6 to 5.times.10.sup.6
Pa, and the low-pressure liquid has a pressure ranging from
1.times.10.sup.5 to 5.times.10.sup.5 Pa, for example. The
functional water described above may be used for at least one of
the high-pressure liquid and the low-pressure liquid. After the
substrate W is cleaned, the supply of the cleaning liquid, the
rinsing liquid, or the like from the liquid supply nozzle 82 is
stopped, and then the rotational table 86 is rotated at a high
rotational speed of 2000 rpm (min.sup.-1) or more for thereby
centrifugally drying the substrate W.
[0071] The substrate W is cleaned in a non-contact manner in the
cleaning/drying module 80 shown in FIGS. 8A and 8B. However, the
substrate W may be cleaned alternatively or additionally by a
pencil-type cleaner which performs a rotational motion on the
surface, to be cleaned, of the substrate W. FIG. 9 is a perspective
view showing a cleaning/drying module having such a pencil-type
cleaner. In FIG. 9, a semiconductor substrate W to be cleaned is
transferred by a transfer robot, which will be described later on
in FIGS. 10A and 10B, to a position above a spin chuck 92, and held
by the spin chuck 92 in such a state that the surface, to be
cleaned, of the substrate W faces upwardly. Then, the spin chuck 92
is rotated at a predetermined rotational speed to rotate the
substrate W, and at the same time, functional water is supplied
from a functional water supply nozzle 98 toward a substantially
central portion of the substrate W.
[0072] A pencil-type cleaner 96 is mounted on a swing arm 97 via a
rotational shaft 90. The pencil-type cleaner 96 has a cleaning
member 93 comprising a PVA sponge or the like and being mounted on
the pencil-type cleaner 96. The swing arm 97 is operable to perform
a swinging motion and a vertical motion. The cleaning unit performs
a cleaning process as follows: The swing arm 97 is swung to bring
the pencil-type cleaner 96 to a position above a substantially
central portion of the substrate W. At this time, the pencil-type
cleaner 96 is not rotated. Then, the swing arm 97 is moved
downwardly to bring the cleaning member 93 of the pencil-type
cleaner 96 into contact with the upper surface of the substrate W.
Immediately before the cleaning member 93 is brought into contact
with the substrate W, the pencil-type cleaner 96 starts to be
rotated about the rotational shaft 90 at a predetermined rotational
speed. The cleaning member 93 is rotated independently of the
substrate W which is being rotated by the spin chuck 92, and is
pressed against the surface, to be cleaned, of the substrate W by
the swing arm 97 under a predetermined pressing force. Then, the
swing arm 97 is swung to bring the cleaning member 93 to the
circumferential edge of the substrate W at a predetermined speed,
thereby scrubbing the substrate W.
[0073] FIG. 10A is a schematic view showing a polishing apparatus
which incorporates a cleaning apparatus according to the present
invention. FIG. 10B is a perspective view showing an essential part
of the polishing apparatus shown in FIG. 10A. The polishing
apparatus shown in FIGS. 10A and 10B serves to polish and planarize
a substrate W having a conductive material such as a metal
interconnect material or an insulating material, which is formed on
the surface of the substrate W by a CVD apparatus or a plating
apparatus (not shown). The polishing apparatus has a polishing unit
100, a loading/unloading unit 122, two transfer mechanisms
(transfer robots) 124a, 124b, a cleaning unit (cleaning mechanism)
126 having three cleaning modules 126a, 126b and 126c, and a
reversing machine 128. The cleaning modules 126a, 126b and 126c may
comprise a roll cleaning mechanism as shown in FIG. 7, a cleaning
mechanism which employs a pencil-type cleaner as shown in FIG. 9,
and a cleaning mechanism for supplying a cleaning liquid as shown
in FIGS. 8A and 8B, respectively.
[0074] The substrate W is processed in the polishing apparatus as
follows: The transfer mechanism 124b transfers the substrate W from
the loading/unloading unit 122 to the reversing machine 128. The
substrate W is reversed by the reversing machine 128 in such a
state that a surface to be polished faces downwardly. The reversed
substrate W is then transferred by the transfer mechanism 124a to a
substrate-transfer base 138. The substrate W is placed on the
substrate-transfer base 138 and is then held by a top ring 113
under vacuum. The substrate W is pressed against a polishing pad
attached on a polishing table 112 under a predetermined pressing
force. At this time, the top ring 113 and the polishing table 112
are moved, e.g., rotated, relatively to each other while a
polishing liquid is supplied onto the polishing table 112, thus
polishing the substrate W.
[0075] The polished substrate W is transferred to the
substrate-transfer base 138 by the top ring 113, and then
transferred from the substrate-transfer base 138 to the cleaning
module 126a by the transfer mechanism 124a. The cleaning module
126a, which may comprise a roll cleaning mechanism, for example,
cleans the substrate W with use of the functional water of the
present invention. The substrate W which has been cleaned by the
cleaning module 126a is then transferred by the transfer mechanism
124a to the cleaning module 126b and the cleaning module 126c in
this order, where the substrate W is cleaned with use of the
functional water. The cleaning module 126c rotates the cleaned
substrate W at a high rotational speed, thereby spin-drying the
substrate W.
[0076] The cleaned and dried substrate W is transferred to the
loading/unloading unit 122 by the transfer mechanism 124b, and is
accommodated in a cassette (not shown). The cleaning unit 126 is
supplied with the functional water of the present invention as a
cleaning liquid from the functional water producing unit (see FIG.
1 or FIG. 2) for thereby preventing the substrate W from being
corroded when the substrate W is cleaned after being polished. The
polishing liquid used in the polishing unit 100 comprises an
alkaline liquid referred to as slurry, a colloid, or abrasive
particles. Therefore, distribution of the functional water or a
type of gas to be dissolved in the functional water can be changed
to selectively supply the functional water to the cleaning module
126a and the subsequent cleaning modules 126b, 126c. A cleaning
capability of the functional water of the present invention varies
depending on a temperature of the functional water at the time of
being supplied to the substrate. Therefore, a device (not shown)
for measuring a temperature of the functional water and a device
(not shown) for controlling a temperature of the functional water
may be provided in the functional water producing unit or the
functional water supply pipe (see FIG. 1 or FIG. 2).
[0077] As described above, according to the present invention,
functional water such as gas-dissolved water is used instead of
pure water so as to shift a surface potential of one or more metals
or alloys for forming a circuit on a substrate, thereby preventing
the metal from being corroded.
[0078] If the functional water of the present invention comprises
oxygen-gas-dissolved water or hydrogen-gas dissolved water, then
since both of the oxygen-gas-dissolved water and the hydrogen-gas
dissolved water are neutral, the substrate does not need to be
rinsed with pure water after being cleaned with the
oxygen-gas-dissolved water or the hydrogen-gas dissolved water.
Further, even if the substrate is rinsed with pure water after
being cleaned with gas-dissolved water such as oxygen-gas-dissolved
water or hydrogen-gas dissolved water, the substrate is not
corroded by the pure water because the surface of the metal has
been passivated by oxygen contained in the gas-dissolved water.
[0079] Furthermore, according to the present invention, it is
possible to shift not only a surface potential of a metal, but also
a surface potential of a silicon substrate or a glass.
Particularly, gas-dissolved water with two or more gases dissolved
therein is effective in minimizing any damage to the substrate
which may occur in the case where only a single gas such as a
hydrogen gas, a reducing gas, or an ozone gas is dissolved in the
gas-dissolved water.
[0080] An example of the present invention will be described below.
However, the present invention should not be interpreted as being
limited to the example described below.
[0081] Measurement of potentials of metals in functional
waters:
[0082] Potentials of Al (aluminum), TiN (titanium nitride), and W
(tungsten) were measured when these metals are dipped in several
types of functional waters. The measured potentials are shown in
Table 1 below. Potential differentials between the above metals
which are derived from the measured potentials are shown in Table 2
below.
1 TABLE 1 Metal potential (when stable) [mV] Functional water Al
TiN W Deionized water -1120 -430 -490 Anode water -310 -280 -220
Cathode water -770 -450 -290 Mixed water -264 -290 -250
[0083]
2 TABLE 2 Potential difference between metals [mV] Functional water
Al--TiN Al--W Deionized water -690 -628 Anode water -30 -90 Cathode
water -320 -480 Mixed water 26 -14
[0084] As can be seen from the results shown in Table 1, it is
possible to shift the surface potential of the metal by selecting
the functional water to be used for cleaning the metal. In
addition, as can be seen from the results shown in Table 2, it is
possible to reduce the potential difference between the metals by
selecting the functional water in accordance with a combination of
the metals. Therefore, it is possible to prevent the metal from
being corroded when the metal is cleaned.
[0085] The cleaning apparatus according to the present invention is
effective in preventing corrosion which may occur due to the
potential difference between different types of metals such as a
circuit-forming metal and a barrier metal by selecting functional
water as cleaning water. Therefore, a base metal such as aluminum
having a low potential can be used for forming fine interconnects
on a substrate, thus allowing a highly integrated circuit to be
formed on the substrate.
* * * * *