U.S. patent application number 12/936427 was filed with the patent office on 2011-02-10 for substrate cleaning method and substrate cleaning apparatus.
Invention is credited to Masanobu Sato.
Application Number | 20110031326 12/936427 |
Document ID | / |
Family ID | 41721236 |
Filed Date | 2011-02-10 |
United States Patent
Application |
20110031326 |
Kind Code |
A1 |
Sato; Masanobu |
February 10, 2011 |
SUBSTRATE CLEANING METHOD AND SUBSTRATE CLEANING APPARATUS
Abstract
A valve is closed while a cleaning liquid is fed into a tubular
body of a cleaning nozzle, and a piezoelectric element applies
vibrations to the cleaning liquid. This causes droplets of the
cleaning liquid to be produced and discharged from a plurality of
discharge holes. The droplet diameter of the discharged droplets is
in the range from 15 to 200 .mu.m, and the distribution of the
droplet diameter is such that the value of where a value of
3.sigma. does not exceed 10% of the average droplet diameter. The
droplet speed is in the range from 20 to 100 meters per second, and
the distribution of the droplet speed is such that the value of
where a value of 3.sigma. does not exceed 10% of the average
droplet speed. The droplet flow rate is not less than 10
milliliters per minute. Discharging the droplets of the cleaning
liquid from the cleaning nozzle toward a substrate while satisfying
these discharge conditions improves cleaning efficiency without
damages to the substrate.
Inventors: |
Sato; Masanobu; (Kyoto,
JP) |
Correspondence
Address: |
OSTROLENK FABER GERB & SOFFEN
1180 AVENUE OF THE AMERICAS
NEW YORK
NY
100368403
US
|
Family ID: |
41721236 |
Appl. No.: |
12/936427 |
Filed: |
July 17, 2009 |
PCT Filed: |
July 17, 2009 |
PCT NO: |
PCT/JP2009/062968 |
371 Date: |
October 5, 2010 |
Current U.S.
Class: |
239/1 ;
239/102.2 |
Current CPC
Class: |
H01L 21/02057 20130101;
H01L 21/67051 20130101 |
Class at
Publication: |
239/1 ;
239/102.2 |
International
Class: |
B05B 1/08 20060101
B05B001/08 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 29, 2008 |
JP |
2008-221157 |
Claims
1. A substrate cleaning method for cleaning a substrate by
discharging droplets of a cleaning liquid toward the substrate,
wherein droplets of a cleaning liquid having an average droplet
diameter in the range from 15 to 200 .mu.m and a droplet diameter
distribution where a value of 3.sigma. (where .sigma. is a standard
deviation) does not exceed 10% of said average droplet diameter are
produced and discharged toward a substrate.
2. The substrate cleaning method according to claim 1, wherein
droplets having an average droplet speed in the range from 20 to
100 meters per second and a droplet speed distribution where a
value of 3.sigma. (where .sigma. is a standard deviation) does not
exceed 10% of said average droplet speed are discharged toward the
substrate.
3. The substrate cleaning method according to claim 2, wherein said
droplets are discharged toward the substrate at a droplet flow rate
of not less than 10 milliliters per minute.
4. A substrate cleaning method for cleaning a semiconductor
substrate by discharging droplets of a cleaning liquid toward the
semiconductor substrate, wherein droplets of a cleaning liquid
having an average droplet diameter in the range from 15 to 30 .mu.m
and a droplet diameter distribution where a value of 3.sigma.
(where .sigma. is a standard deviation) does not exceed 2 .mu.m are
produced and discharged toward a semiconductor substrate.
5. The substrate cleaning method according to claim 4, wherein
droplets having an average droplet speed in the range from 20 to 60
meters per second and a droplet speed distribution where a value of
3.sigma. (where .sigma. is a standard deviation) does not exceed 5
meters per second are discharged toward the semiconductor
substrate.
6. The substrate cleaning method according to claim 5, wherein said
droplets are discharged toward the semiconductor substrate at a
droplet flow rate of not less than 10 milliliters per minute.
7. A substrate cleaning method for cleaning a substrate by
discharging droplets of a cleaning liquid toward the substrate,
wherein a cleaning liquid is fed to a tubular body including a
plurality of discharge holes formed in a wall surface thereof, and
vibrations are applied to the cleaning liquid, whereby droplets of
the cleaning liquid having an average droplet diameter in the range
from 15 to 200 .mu.m and a droplet diameter distribution where a
value of 3.sigma. (where .sigma. is a standard deviation) does not
exceed 10% of said average droplet diameter are discharged from
said plurality of discharge holes toward a substrate.
8. The substrate cleaning method according to claim 7, wherein
droplets having an average droplet speed in the range from 20 to
100 meters per second and a droplet speed distribution where a
value of 3.sigma. (where .sigma. is a standard deviation) does not
exceed 10% of said average droplet speed are discharged from said
plurality of discharge holes toward the substrate.
9. The substrate cleaning method according to claim 8, wherein
droplets of the cleaning liquid are discharged from said plurality
of discharge holes toward the substrate at a droplet flow rate of
not less than 10 milliliters per minute.
10. A substrate cleaning method for cleaning a semiconductor
substrate by discharging droplets of a cleaning liquid toward the
semiconductor substrate, wherein a cleaning liquid is fed to a
tubular body including a plurality of discharge holes formed in a
wall surface thereof, and vibrations are applied to the cleaning
liquid, whereby droplets of the cleaning liquid having an average
droplet diameter in the range from 15 to 30 .mu.m and a droplet
diameter distribution where a value of 3.sigma. (where .sigma. is a
standard deviation) does not exceed 2 .mu.m are discharged from
said plurality of discharge holes toward a semiconductor
substrate.
11. The substrate cleaning method according to claim 10, wherein
droplets having an average droplet speed in the range from 20 to 60
meters per second and a droplet speed distribution where a value of
3.sigma. (where .sigma. is a standard deviation) does not exceed 5
meters per second are discharged from said plurality of discharge
holes toward the semiconductor substrate.
12. The substrate cleaning method according to claim 11, wherein
droplets of the cleaning liquid are discharged from said plurality
of discharge holes toward the semiconductor substrate at a droplet
flow rate of not less than 10 milliliters per minute.
13. A substrate cleaning apparatus for cleaning a substrate by
discharging droplets of a cleaning liquid toward the substrate,
comprising a cleaning nozzle having a tubular body including a
plurality of discharge holes formed in a wall surface thereof, and
a piezoelectric element affixed to said wall surface, said cleaning
nozzle being configured to apply vibrations to a cleaning liquid
fed to said tubular body from said piezoelectric element, thereby
discharging droplets of the cleaning liquid having an average
droplet diameter in the range from 15 to 200 .mu.m and a droplet
diameter distribution where a value of 3.sigma. (where .sigma. is a
standard deviation) does not exceed 10% of said average droplet
diameter from said plurality of discharge holes toward a
substrate.
14. The substrate cleaning apparatus according to claim 13, wherein
said cleaning nozzle discharges droplets having an average droplet
speed in the range from 20 to 100 meters per second and a droplet
speed distribution where a value of 3.sigma. (where .sigma. is a
standard deviation) does not exceed 10% of said average droplet
speed from said plurality of discharge holes toward the
substrate.
15. The substrate cleaning apparatus according to claim 14, wherein
said cleaning nozzle discharges droplets of the cleaning liquid
from said plurality of discharge holes toward the substrate at a
droplet flow rate of not less than 10 milliliters per minute.
16. A substrate cleaning apparatus for cleaning a semiconductor
substrate by discharging droplets of a cleaning liquid toward the
semiconductor substrate, wherein a cleaning nozzle having a tubular
body including a plurality of discharge holes formed in a wall
surface thereof, and a piezoelectric element affixed to said wall
surface, said cleaning nozzle being configured to apply vibrations
to a cleaning liquid fed to said tubular body from said
piezoelectric element, thereby discharging droplets of the cleaning
liquid having an average droplet diameter in the range from 15 to
30 .mu.m and a droplet diameter distribution where a value of
3.sigma. (where .sigma. is a standard deviation) does not exceed 2
.mu.m from said plurality of discharge holes toward a semiconductor
substrate.
17. The substrate cleaning apparatus according to claim 16, wherein
said cleaning nozzle discharges droplets having an average droplet
speed in the range from 20 to 60 meters per second and a droplet
speed distribution where a value of 3.sigma. (where .sigma. is a
standard deviation) does not exceed 5 meters per second from said
plurality of discharge holes toward the semiconductor
substrate.
18. The substrate cleaning apparatus according to claim 17, wherein
said cleaning nozzle discharges droplets of the cleaning liquid
from said plurality of discharge holes toward the semiconductor
substrate at a droplet flow rate of not less than 10 milliliters
per minute.
19. The substrate cleaning apparatus according to claim 13, wherein
said tubular body is cylindrical.
20. The substrate cleaning apparatus according to claim 13, further
comprising: a pressure pump for feeding a cleaning liquid through
an opening at a first end of said tubular body; and a valve for
closing an opening at a second end of said tubular body.
Description
TECHNICAL FIELD
[0001] The present invention relates to a substrate cleaning method
and a substrate cleaning apparatus for cleaning a semiconductor
substrate, a glass substrate for a liquid crystal display device, a
glass substrate for a photomask, a substrate for an optical disk, a
ceramic plate, and the like (hereinafter referred to simply as
"substrates") by discharging droplets of a cleaning liquid onto the
substrates.
BACKGROUND ART
[0002] In the manufacturing process of a semiconductor substrate
and the like, a cleaning step for removing particles deposited on
the substrate therefrom has been hitherto essential. A single wafer
type cleaning apparatus for executing the cleaning step uses the
technique of cleaning a substrate by jetting out fine droplets of a
cleaning liquid such as deionized water toward the substrate.
[0003] In such a cleaning apparatus, a two-fluid nozzle for
producing droplets by mixing a cleaning liquid and a pressurized
gas together to jet out a fluid mixture of the droplets and a gas
toward the substrate has been widely used, as disclosed, for
example, in Patent Document 1. Foreign materials such as particles
deposited on the substrate are physically removed by the kinetic
energy of the droplets of the cleaning liquid. Also, Patent
Document 2 discloses a cleaning apparatus that causes a
piezoelectric element to expand and contract repeatedly at a
frequency of an ultrasonic band, thereby emitting a mist of a
cleaning liquid accelerated in one direction from a discharge port
toward a substrate at a high speed.
[0004] As a technique for discharging droplets, on the other hand,
Patent Document 3 discloses a droplet spraying apparatus that
vibrates a thin film formed with discharge ports of an inverted
tapered shape to produce droplets. Also, Patent Document 4
discloses a nozzle head for an inkjet printer in which a pipe of an
annular shape formed with a notch is filled with ink, and in which
a vibrator is attached to an outer peripheral wall surface of the
pipe except where the notch is formed to vibrate the ink, whereby
droplets of ink are emitted.
PRIOR ART DOCUMENTS
Patent Documents
[0005] Patent Document 1: Japanese Patent Application Laid-Open No.
2007-227878 [0006] Patent Document 2: Japanese Patent Application
Laid-Open No. 2000-533 [0007] Patent Document 3: Japanese Patent
No. 3659593 [0008] Patent Document 4: Japanese Utility Model
Publication No. 7-7164 (1995)
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0009] However, when the two-fluid nozzle as disclosed in Patent
Document 1 is used, the speed and size (droplet diameter) of the
produced droplets are distributed over a wide range. In the
cleaning process of a semiconductor substrate, it is necessary to
ensure the removal of particles without destruction of devices on
the substrate. However, when the speed and size of the droplets are
distributed over a wide range, some of the droplets are useless
droplets not contributing to the removal of the particles, whereas
some of the droplets are so harmful droplets as to cause damages to
the devices. As a result, there have been problems in that
improvements in cleaning efficiency are suppressed and in that
there is a likelihood of device destruction. These problems arise
similarly in the cleaning of other substrates, and have become a
cause of uneven cleaning results.
[0010] The present invention has been made to solve the
above-mentioned problems. It is therefore an object of the present
invention to provide a substrate cleaning method and a substrate
cleaning apparatus capable of improving the cleaning efficiency of
a substrate.
Means for Solving the Problems
[0011] To solve the above-mentioned problems, according to a first
aspect of the present invention, in a substrate cleaning method for
cleaning a substrate by discharging droplets of a cleaning liquid
toward the substrate, droplets of a cleaning liquid having an
average droplet diameter in the range from 15 to 200 .mu.m and a
droplet diameter distribution where a value of 3.sigma. (where
.sigma. is a standard deviation) does not exceed 10% of the average
droplet diameter are produced and discharged toward a
substrate.
[0012] According to a second aspect, in the substrate cleaning
method according to the first aspect, droplets having an average
droplet speed in the range from 20 to 100 meters per second and a
droplet speed distribution where a value of 3.sigma. (where a is a
standard deviation) does not exceed 10% of the average droplet
speed are discharged toward the substrate.
[0013] According to a third aspect, in the substrate cleaning
method according to the first or second aspect, the droplets are
discharged toward the substrate at a droplet flow rate of not less
than 10 milliliters per minute.
[0014] According to a fourth aspect, in a substrate cleaning method
for cleaning a semiconductor substrate by discharging droplets of a
cleaning liquid toward the semiconductor substrate, droplets of a
cleaning liquid having an average droplet diameter in the range
from 15 to 30 .mu.m and a droplet diameter distribution where a
value of 3.sigma. (where .sigma. is a standard deviation) does not
exceed 2 .mu.m are produced and discharged toward a semiconductor
substrate.
[0015] According to a fifth aspect, in the substrate cleaning
method according to the fourth aspect, droplets having an average
droplet speed in the range from 20 to 60 meters per second and a
droplet speed distribution where a value of 3.sigma. (where .sigma.
is a standard deviation) does not exceed 5 meters per second are
discharged toward the semiconductor substrate.
[0016] According to a sixth aspect, in the substrate cleaning
method according to the fourth or fifth aspect, the droplets are
discharged toward the semiconductor substrate at a droplet flow
rate of not less than 10 milliliters per minute.
[0017] According to a seventh aspect, in a substrate cleaning
method for cleaning a substrate by discharging droplets of a
cleaning liquid toward the substrate, a cleaning liquid is fed to a
tubular body including a plurality of discharge holes formed in a
wall surface thereof, and vibrations are applied to the cleaning
liquid, whereby droplets of the cleaning liquid having an average
droplet diameter in the range from 15 to 200 .mu.m and a droplet
diameter distribution where a value of 3.sigma. (where .sigma. is a
standard deviation) does not exceed 10% of the average droplet
diameter are discharged from the plurality of discharge holes
toward a substrate.
[0018] According to an eighth aspect, in the substrate cleaning
method according to the seventh aspect, droplets having an average
droplet speed in the range from 20 to 100 meters per second and a
droplet speed distribution where a value of 3.sigma. (where .sigma.
is a standard deviation) does not exceed 10% of the average droplet
speed are discharged from the plurality of discharge holes toward
the substrate.
[0019] According to a ninth aspect, in the substrate cleaning
method according to the seventh or eighth aspect, droplets of the
cleaning liquid are discharged from the plurality of discharge
holes toward the substrate at a droplet flow rate of not less than
10 milliliters per minute.
[0020] According to a tenth aspect, in a substrate cleaning method
for cleaning a semiconductor substrate by discharging droplets of a
cleaning liquid toward the semiconductor substrate, a cleaning
liquid is fed to a tubular body including a plurality of discharge
holes formed in a wall surface thereof, and vibrations are applied
to the cleaning liquid, whereby droplets of the cleaning liquid
having an average droplet diameter in the range from 15 to 30 .mu.m
and a droplet diameter distribution where a value of 3.sigma.
(where .sigma. is a standard deviation) does not exceed 2 .mu.m are
discharged from the plurality of discharge holes toward a
semiconductor substrate.
[0021] According to an eleventh aspect, in the substrate cleaning
method according to the tenth aspect, droplets having an average
droplet speed in the range from 20 to 60 meters per second and a
droplet speed distribution where a value of 3.sigma. (where .sigma.
is a standard deviation) does not exceed 5 meters per second are
discharged from the plurality of discharge holes toward the
semiconductor substrate.
[0022] According to a twelfth aspect, in the substrate cleaning
method according to the tenth or eleventh aspect, droplets of the
cleaning liquid are discharged from the plurality of discharge
holes toward the semiconductor substrate at a droplet flow rate of
not less than 10 milliliters per minute.
[0023] According to a thirteenth aspect, a substrate cleaning
apparatus for cleaning a substrate by discharging droplets of a
cleaning liquid toward the substrate comprises a cleaning nozzle
having a tubular body including a plurality of discharge holes
formed in a wall surface thereof, and a piezoelectric element
affixed to the wall surface, the cleaning nozzle being configured
to apply vibrations to a cleaning liquid fed to the tubular body
from the piezoelectric element, thereby discharging droplets of the
cleaning liquid having an average droplet diameter in the range
from 15 to 200 .mu.m and a droplet diameter distribution where a
value of 3.sigma. (where .sigma. is a standard deviation) does not
exceed 10% of the average droplet diameter from the plurality of
discharge holes toward a substrate.
[0024] According to a fourteenth aspect, in the substrate cleaning
apparatus according to the thirteenth aspect, the cleaning nozzle
discharges droplets having an average droplet speed in the range
from 20 to 100 meters per second and a droplet speed distribution
where a value of 3.sigma. (where .sigma. is a standard deviation)
does not exceed 10% of the average droplet speed for from the
plurality of discharge holes toward the substrate.
[0025] According to a fifteenth aspect, in the substrate cleaning
apparatus according to the thirteenth or fourteenth aspect, the
cleaning nozzle discharges droplets of the cleaning liquid from the
plurality of discharge holes toward the substrate at a droplet flow
rate of not less than 10 milliliters per minute.
[0026] According to a sixteenth aspect, a substrate cleaning
apparatus for cleaning a semiconductor substrate by discharging
droplets of a cleaning liquid toward the semiconductor substrate
comprises a cleaning nozzle having a tubular body including a
plurality of discharge holes formed in a wall surface thereof, and
a piezoelectric element affixed to the wall surface, the cleaning
nozzle being configured to apply vibrations to a cleaning liquid
fed to the tubular body from the piezoelectric element, thereby
discharging droplets of the cleaning liquid having an average
droplet diameter in the range from 15 to 30 .mu.m and a droplet
diameter distribution where a value of 3.sigma. (where .sigma. is a
standard deviation) does not exceed 2 .mu.m from the plurality of
discharge holes toward a semiconductor substrate.
[0027] According to a seventeenth aspect, in the substrate cleaning
apparatus according to the sixteenth aspect, the cleaning nozzle
discharges droplets having an average droplet speed in the range
from 20 to 60 meters per second and a droplet speed distribution
where a value of 3.sigma. (where .sigma. is a standard deviation)
does not exceed 5 meters per second from the plurality of discharge
holes toward the semiconductor substrate.
[0028] According to an eighteenth aspect, in the substrate cleaning
apparatus according to the sixteenth or seventeenth aspect, the
cleaning nozzle discharges droplets of the cleaning liquid from the
plurality of discharge holes toward the semiconductor substrate at
a droplet flow rate of not less than 10 milliliters per minute.
[0029] According to a nineteenth aspect, in the substrate cleaning
apparatus according to any one of the thirteenth to eighteenth
aspects, the tubular body is cylindrical.
[0030] According to a twentieth aspect, the substrate cleaning
apparatus according to any one of the thirteenth to nineteenth
aspects further comprises: a pressure pump for feeding a cleaning
liquid through an opening at a first end of the tubular body; and a
valve for closing an opening at a second end of the tubular
body.
EFFECT OF THE INVENTION
[0031] According to the first to third, the seventh to ninth, and
the thirteenth to fifteenth aspects of the present invention, the
droplets of the cleaning liquid having an average droplet diameter
in the range from 15 to 200 .mu.m and a droplet diameter
distribution where a value of 3.sigma. does not exceed 10% of the
average droplet diameter are discharged toward the substrate. Thus,
there are a small number of useless droplets not contributing to
the cleaning. This improves the cleaning efficiency of the
substrate.
[0032] In particular, according to the second, eighth and
fourteenth aspects, the droplets having an average droplet speed in
the range from 20 to 100 meters per second and a droplet speed
distribution where a value of 3.sigma. does not exceed 10% of the
average droplet speed are discharged toward the substrate. This
provides sufficient cleaning efficiency.
[0033] In particular, according to the third, ninth and fifteenth
aspects, the droplets are discharged toward the substrate at a
droplet flow rate of not less than 10 milliliters per minute. This
achieves sufficient cleaning in a short time.
[0034] According to the fourth to sixth, the tenth to twelfth, and
the sixteenth to eighteenth aspects of the present invention, the
droplets of the cleaning liquid having an average droplet diameter
in the range from 15 to 30 .mu.m and a droplet diameter
distribution where a value of 3.sigma. does not exceed 2 .mu.m are
discharged toward the semiconductor substrate. Thus, there are a
small number of useless droplets not contributing to the cleaning
and a small number of droplets that cause damages to the
semiconductor substrate. This improves the cleaning efficiency of
the substrate.
[0035] In particular, according to the fifth, eleventh and
seventeenth aspects, the droplets having an average droplet speed
in the range from 20 to 60 meters per second and a droplet speed
distribution where a value of 3.sigma. does not exceed 5 meters per
second are discharged toward the semiconductor substrate. This
provides sufficient cleaning efficiency.
[0036] In particular, according to the sixth, twelfth and
eighteenth aspects, the droplets are discharged toward the
semiconductor substrate at a droplet flow rate of not less than 10
milliliters per minute. This achieves sufficient cleaning in a
short time.
BRIEF DESCRIPTION OF DRAWINGS
[0037] FIG. 1 is a view showing an example of a substrate cleaning
apparatus appropriate for the cleaning of a semiconductor
substrate.
[0038] FIG. 2 is a view schematically showing the construction of a
cleaning nozzle.
[0039] FIG. 3 is a perspective view of the cleaning nozzle.
[0040] FIG. 4 is a graph showing distributions of the droplet
diameter of a cleaning liquid.
[0041] FIG. 5 is a graph showing distributions of the droplet speed
of the cleaning liquid.
[0042] FIG. 6 is a graph showing a correlation between the droplet
diameter of discharged droplets and damages to the substrate.
[0043] FIG. 7 is a graph showing a correlation between the droplet
speed of the discharged droplets and the removal rate of
contaminants.
[0044] FIG. 8 is a graph showing a difference in the removal rate
of contaminants depending on the droplet flow rate of the
discharged droplets.
[0045] FIG. 9 is a view showing a substrate cleaning apparatus for
performing a cleaning process on a substrate including other
types.
[0046] FIG. 10 is a graph showing distributions of the droplet
diameter of the cleaning liquid appropriate for the cleaning of the
substrate including other types.
[0047] FIG. 11 is a graph showing distributions of the droplet
speed of the cleaning liquid appropriate for the cleaning of the
substrate including other types.
[0048] FIG. 12 is a view showing another example of the cleaning
nozzle.
[0049] FIG. 13 is a view showing another example of the cleaning
nozzle.
[0050] FIG. 14 is a view showing another example of the cleaning
nozzle.
EMBODIMENTS OF THE INVENTION
[0051] Embodiments according to the present invention will now be
described in detail with reference to the drawings.
[0052] FIG. 1 is a view showing an example of a substrate cleaning
apparatus appropriate for the cleaning of a semiconductor
substrate. This substrate cleaning apparatus 1 is a single wafer
type cleaning apparatus for cleaning semiconductor substrates W one
by one, and cleans a circular substrate W of silicon by removing
contaminants such as particles deposited on the substrate W
therefrom. The substrate cleaning apparatus 1 includes a rotary
holding part 10, a processing cup 20, a splash guard 30, a nozzle
driving part 50, a cleaning nozzle 60, and a controller 90 as its
principal components.
[0053] The rotary holding part 10 includes a spin base 11, a rotary
shaft 13, and a motor 14. The spin base 11 is a disk-shaped member
having a diameter slightly greater than that of the substrate W.
The spin base 11 has a plurality of (in this embodiment, six)
support pins 12 provided upright on a peripheral portion of the
upper surface of the spin base 11 and arranged on the circumference
of the same circle. Each of the support pins 12 includes a
cylindrical support portion for supporting a peripheral portion of
the lower surface of the substrate W from below, and a pin portion
protruding from the upper surface of the support portion and
abutting against an edge portion of the substrate W to push the
substrate W. Three out of the six support pins 12 are fixed support
pins fixedly provided on the spin base 11. Each of the fixed
support pins is configured such that the protruding pin portion is
provided over the axis of the cylindrical support portion. On the
other hand, the remaining three out of the six support pins 12 are
movable support pins provided rotatably (on their axes) relative to
the spin base 11. Each of the movable support pins is configured
such that the protruding pin portion is provided slightly
eccentrically with respect to the axis of the cylindrical support
portion. The three movable support pins are pivotably driven in
cooperation with each other by a linkage mechanism and a drive
mechanism both not shown. The pivotal movement of the movable
support pins allows the six pin portions to grasp the edge portion
of the substrate W and to release the grasp of the substrate W. The
six support pins 12 grasp the edge portion of the substrate W to
thereby allow the spin base 11 to hold the substrate W in a
horizontal position without contacting a central portion of the
lower surface of the substrate W.
[0054] The rotary shaft 13 is suspended from a central portion of
the lower surface of the spin base 11. The rotary shaft 13 is
cooperatively coupled to a driving pulley 16 of the motor 14
through a driving belt 15. As the motor 14 rotatably drives the
driving pulley 16, the driving belt 15 runs around to rotate the
rotary shaft 13. This causes the substrate W held by the spin base
11 to rotate around a vertical central axis RX within a horizontal
plane together with the spin base 11 and the rotary shaft 13.
[0055] The rotary shaft 13 also has a hollow interior in which a
processing liquid nozzle 18 is inserted in a vertical direction.
The processing liquid nozzle 18 is connected in communication with
a processing liquid supply source not shown. The processing liquid
nozzle 18 has a tip opening toward the central portion of the lower
surface of the substrate W held by the spin base 11. This allows
the supply of a processing liquid from the tip of the processing
liquid nozzle 18 to the central portion of the lower surface of the
substrate W.
[0056] A gap between the inner wall surface of the rotary shaft 13
and the outer wall surface of the processing liquid nozzle 18
serves as a gas supply passage which in turn is connected in
communication with a gas supply source not shown. This allows the
supply of a gas from the upper end of the gap toward the lower
surface of the substrate W held by the spin base 11.
[0057] The processing cup 20 is provided to surround the rotary
holding part 10. A cylindrical partition wall 21 is provided within
the processing cup 20. A drainage space 22 for draining a cleaning
liquid used for the cleaning process of the substrate W is formed
within the partition wall 21 so as to surround the rotary holding
part 10. A collection space 23 for collecting the cleaning liquid
used for the cleaning process of the substrate W is defined between
the outer wall of the processing cup 20 and the partition wall 21
so as to surround the drainage space 22.
[0058] A drainage pipe 27 for guiding the cleaning liquid to a
drainage processing apparatus (not shown) is connected to the
drainage space 22, and a collection pipe 28 for guiding the
cleaning liquid to a collection processing apparatus (not shown) is
connected to the collection space 23.
[0059] The splash guard 30 for preventing the cleaning liquid from
the substrate W from splashing outwardly is provided over the
processing cup 20. This splash guard 30 has a configuration
rotationally symmetric with respect to the central axis RX. A
drainage guide groove 31 of a V-shaped sectional configuration is
formed annularly in the inner surface of an upper end portion of
the splash guard 30. A collected liquid guide portion 32 defined by
an outwardly downwardly inclined surface is formed in the inner
surface of a lower end portion of the splash guard 30. A partition
wall receiving groove 33 for receiving the partition wall 21 in the
processing cup 20 is formed near the upper end of the collected
liquid guide portion 32.
[0060] The splash guard 30 is driven to move upwardly and
downwardly in a vertical direction by a guard up-and-down driving
mechanism 35 including a ball screw mechanism and the like. The
guard up-and-down driving mechanism 35 moves the splash guard 30
upwardly and downwardly between a collection position in which the
collected liquid guide portion 32 surrounds the edge portion of the
substrate W held by the spin base 11 and a drainage position in
which the drainage guide groove 31 surrounds the edge portion of
the substrate W held by the spin base 11. When the splash guard 30
is in the collection position (the position shown in FIG. 1), the
cleaning liquid splashed from the edge portion of the substrate W
is guided by the collected liquid guide portion 32 into the
collection space 23, and is then collected through the collection
pipe 28. When the splash guard 30 is in the drainage position, on
the other hand, the cleaning liquid splashed from the edge portion
of the substrate W is guided by the drainage guide groove 31 into
the drainage space 22, and is then drained through the drainage
pipe 27. In this manner, the drainage and collection of the
cleaning liquid are selectively executable. When the substrate W is
transferred to and received from the spin base 11, the guard
up-and-down driving mechanism 35 moves the splash guard 30
downwardly to a vertical position in which the spin base 11
protrudes upwardly from the upper end of the splash guard 30.
[0061] The nozzle driving part 50 includes a vertical movement
motor 51, a swing motor 53, and a nozzle arm 58. The nozzle arm 58
has a distal end to which the cleaning nozzle 60 attached. The
nozzle arm 58 has a proximal end coupled to a motor shaft 53a of
the swing motor 53. The swing motor 53 causes the cleaning nozzle
60 to pivot about the motor shaft 53a within a horizontal
plane.
[0062] The swing motor 53 is mounted to a vertical movement base
54. The vertical movement base 54 is in threaded engagement with a
ball screw 52 coupled directly to the motor shaft of the fixedly
provided vertical movement motor 51, and is slidably mounted to a
guide member 55. As the vertical movement motor 51 rotates the ball
screw 52, the cleaning nozzle 60 moves upwardly and downwardly
together with the vertical movement base 54.
[0063] The vertical movement motor 51 and the swing motor 53 in the
nozzle driving part 50 move the cleaning nozzle 60 between a
retracted position that is outside the splash guard 30 and a
cleaning position that is over the spin base 11. Also, the swing
motor 53 causes the cleaning nozzle 60 to pivot over the spin base
11 between a position over the central portion of the substrate W
and a position over the edge portion thereof.
[0064] The controller 90 controls various operating mechanisms
provided in the substrate cleaning apparatus 1. The controller 90
is similar in hardware construction to a typical computer.
Specifically, the controller 90 includes a CPU for performing
various computation processes, a ROM or read-only memory for
storing a basic program therein, a RAM or readable/writable memory
for storing various pieces of information therein, and a magnetic
disk for storing control software and data therein.
[0065] FIG. 2 is a view schematically showing the construction of
the cleaning nozzle 60. FIG. 3 is a perspective view of the
cleaning nozzle 60. The cleaning nozzle 60 serving as a cleaning
head is configured such that a piezoelectric element (piezo
element) 62 is affixed to a cylindrical tubular body 61. The
cleaning nozzle 60 is attached to the distal end of the nozzle arm
58 with a holder 63 made of resin therebetween. The holder 63 is
not shown in FIG. 3.
[0066] The cylindrical tubular body 61 includes a hollow interior
space formed therein, and has opposite ends both open. In this
embodiment, the tubular body 61 is made of quartz, and has a length
of 50 mm. The tubular body 61 may be made of ceramics such as
zirconia (ZrO.sub.2).
[0067] The tubular body 61 has a plurality of (in this embodiment,
20) discharge holes 64 formed in the wall surface thereof. The 20
discharge holes 64 are arranged in a line in a longitudinal
direction of the tubular body 61. Each of the discharge holes 64
has a substantially cylindrical shape extending through the side
wall of the tubular body 61. The 20 discharge holes 64 have a
uniform diameter in the range from 7 to 12 .mu.m . The spacing
between the 20 discharge holes 64 (the distance between adjacent
ones of the discharge holes 64) is 1 mm.
[0068] The piezoelectric element 62 is affixed to a portion of the
outer wall surface of the tubular body 61 opposed to the plurality
of discharge holes 64. The piezoelectric element 62 is electrically
connected to a power supply 65 having a high-frequency generator.
The power supply 65 applies an alternating voltage having a
predetermined frequency to the piezoelectric element 62.
[0069] An opening at a first end of the interior space of the
tubular body 61 is connected in communication with a cleaning
liquid supply source 71 through a supply pipe 70. A pressure pump
72 and a filter 73 are inserted in the path of the supply pipe 70.
The pressure pump 72 feeds the cleaning liquid (in this embodiment,
deionized water) under pressure from the cleaning liquid supply
source 71 toward the cleaning nozzle 60. The filter 73 removes
contaminants contained in the cleaning liquid fed from the cleaning
liquid supply source 71.
[0070] An opening at a second end of the interior space of the
tubular body 61, on the other hand, is connected in communication
with a delivery pipe 75. A valve 76 is inserted in the path of the
delivery pipe 75. When the valve 76 is opened while the cleaning
liquid is supplied from the supply pipe 70 to the interior space of
the tubular body 61, the cleaning liquid is drained through the
delivery pipe 75 to the outside of the apparatus.
[0071] Next, the processing operations of the substrate cleaning
apparatus 1 having the above-mentioned construction will be
described. The controller 90 executes software for a predetermined
cleaning process to control the mechanisms of the substrate
cleaning apparatus 1, whereby the processing operations to be
described below are performed.
[0072] First, a substrate W is transferred to the spin base 11,
with the splash guard 30 placed in a lowered position so that the
spin base 11 protrudes upwardly from the splash guard 30.
Subsequently, the splash guard 30 moves upwardly to the
above-mentioned drainage position, and the nozzle driving part 50
moves the cleaning nozzle 60 to the cleaning position that is over
the substrate W held by the spin base 11. In the cleaning position,
the spacing between the plurality of discharge holes 64 of the
cleaning nozzle 60 and the substrate W shall be in the range from 5
to 25 mm.
[0073] The cleaning liquid always continues to be fed from the
pressure pump 72 to the cleaning nozzle 60 even when the cleaning
process is not performed. When the cleaning process is not
performed, the valve 76 is open so that the cleaning liquid fed to
the interior of the tubular body 61 continues to be directly
drained through the delivery pipe 75 to the outside of the
apparatus. In other words, the cleaning liquid continues to be fed
to the cleaning nozzle 60 and continues to be drained to the
outside of the apparatus even when the cleaning nozzle 60 is on
standby in the retracted position that is outside the splash guard
30 and when the cleaning nozzle 60 is moving from the retracted
position to the cleaning position that is over the substrate W.
[0074] Next, the rotary holding part 10 starts rotating the
substrate W, and droplets of the cleaning liquid are discharged
from the cleaning nozzle 60 toward the upper surface of the
substrate W. At this time, the cleaning liquid may be discharged
from the processing liquid nozzle 18 toward the lower surface of
the substrate W. Also, the nozzle driving part 50 causes the
cleaning nozzle 60 to pivot between the position over the central
portion of the substrate W and the position over the edge portion
thereof, whereby the cleaning process proceeds. When the cleaning
process is performed, the valve 76 is closed while the cleaning
liquid is fed to the cleaning nozzle 60. Thus, the liquid pressure
of the cleaning liquid within the tubular body 61 increases,
whereby the cleaning liquid is discharged from the 20 discharge
holes 64. In this embodiment, the liquid pressure of the cleaning
liquid within the tubular body 61 shall be not greater than 10
MPa.
[0075] When the cleaning process is performed, the power supply 65
applies the alternating voltage having the predetermined frequency
to the piezoelectric element 62. This causes the piezoelectric
element 62 to expand and contract repeatedly, thereby applying
vibrations at the predetermined frequency to the cleaning liquid
within the tubular body 61. When the liquid pressure of the
cleaning liquid within the tubular body 61 is increased while
vibrations are applied to the cleaning liquid, the cleaning liquid
flowing out of the 20 discharge holes 64 under the liquid pressure
is dispersed and divided into droplets by the vibrations, so that
the droplets of the cleaning liquid are discharged from the 20
discharge holes 64. The division of the liquid flow out of the
discharge holes 64 into droplets is achieved by the following
process. The cleaning liquid maintained at a constant pressure or
at pressures (D.C. pressures) within a narrow range is supplied
into the tubular body 61. The cleaning liquid flows out of the
discharge holes 64 at a discharge rate substantially equal at the
20 discharge holes 64 because of the pressure. When the alternating
voltage having the fixed predetermined frequency is applied to the
piezoelectric element 62 in this state, the generated vibrations
cause the liquid flow to disperse and divide into droplets. The
supply pressure of the cleaning liquid produced by the pressure
pump 72 and the frequency of the alternating current applied to the
piezoelectric element 62 take values falling outside the range of
the normal operation of a continuous inkjet apparatus as described
in the prior art. Contaminants such as particles deposited on the
substrate W are physically removed by the kinetic energy of the
droplets discharged from the cleaning nozzle 60.
[0076] The controller 90 controls the pressure pump 72 to adjust
the liquid pressure of the cleaning liquid within the tubular body
61 and also controls the power supply 65 to adjust the vibrations
applied to the cleaning liquid, thereby specifying the discharge
conditions (parameters) of the droplets discharged from the 20
discharge holes 64. In addition, the diameter of the discharge
holes 64 and the number of discharge holes 64 have an influence on
the discharge conditions of the droplets.
[0077] In the present embodiment, the average droplet diameter of
the droplets of the cleaning liquid discharged from the 20
discharge holes 64 toward the substrate W shall be in the range
from 15 to 30 .mu.m. It is important herein that the droplet
diameter of the droplets discharged from the cleaning nozzle 60 is
not widely distributed over the range from 15 to 30 .mu.m but
variations in the droplet diameter are quite small. Specifically,
the distribution of the droplet diameter is such that the value of
3.sigma. (where .sigma. is a standard deviation) does not exceed 2
.mu.m.
[0078] FIG. 4 is a graph showing distributions of the droplet
diameter of the cleaning liquid. In FIG. 4, the droplet diameter
distribution of the droplets discharged from the cleaning nozzle 60
according to the present embodiment is depicted by the solid line,
and the droplet diameter distribution of droplets discharged from
the conventional two-fluid nozzle is depicted by the dotted line.
The droplet diameter of the droplets discharged from the
conventional two-fluid nozzle has a wide distribution which in turn
includes not only droplets having a droplet diameter in the range
from 15 to 30 .mu.m but also a large number of droplets having a
droplet diameter falling outside the range. In contrast to this,
the droplet diameter of the droplets discharged from the cleaning
nozzle 60 according to the present embodiment has a very narrow
distribution, and there is little variation in the droplet
diameter.
[0079] In the present embodiment, the average droplet speed of the
droplets of the cleaning liquid discharged from the 20 discharge
holes 64 toward the substrate W shall be in the range from 20 to 60
meters per second. Like the droplet diameter, the droplet speed of
the droplets discharged from the cleaning nozzle 60 is not widely
distributed over the range from 20 to 60 meters per second but
variations in the droplet speed are quite small. Specifically, the
distribution of the droplet speed is such that the value of
3.sigma. does not exceed 5 meters per second.
[0080] FIG. 5 is a graph showing distributions of the droplet speed
of the cleaning liquid. In FIG. 5, the droplet speed distribution
of the droplets discharged from the cleaning nozzle 60 according to
the present embodiment is also depicted by the solid line, and the
droplet speed distribution of the droplets discharged from the
conventional two-fluid nozzle is depicted by the dotted line. The
droplet speed of the droplets discharged from the conventional
two-fluid nozzle has a very wide distribution. In contrast to this,
the droplet speed of the droplets discharged from the cleaning
nozzle 60 according to the present embodiment has a very narrow
distribution.
[0081] In this manner, variations in the droplet diameter and
droplet speed of the droplets discharged from the cleaning nozzle
60 according to the present embodiment are allowed to fall within a
small range. This is because the cleaning liquid is discharged from
the plurality of discharge holes 64 by applying vibrations from the
piezoelectric element 62 to the cleaning liquid filled in the
interior of the tubular body 61 under a high pressure. In other
words, the conventional two-fluid nozzle produces droplets by
causing a pressurized gas to collide with a liquid. Thus, the
droplets are discharged in the form of a multiphase flow of the
droplets and the gas, and are hence difficult to control. This
results in wide distributions of and great variations in the
droplet diameter and droplet speed of the droplets. The cleaning
nozzle 60 according to the present embodiment, on the other hand,
discharges the pressurized liquid from the plurality of discharge
holes 64 while applying vibrations to the pressurized liquid. Thus,
only the droplets are discharged. This allows narrow distributions
of and small variations in the droplet diameter and droplet speed
of the droplets.
[0082] FIG. 6 is a graph showing a correlation between the droplet
diameter of the discharged droplets and damages to the substrate W.
As shown in FIG. 6, damages to the substrate W occur when the
droplet diameter exceeds 30 .mu.m. The greater the droplet diameter
is, the greater the damages are. Since the average droplet diameter
of the droplets of the cleaning liquid discharged from the cleaning
nozzle 60 is in the range from 15 to 30 .mu.m, damages to the
substrate W is prevented during the cleaning process.
[0083] Also, variations in droplet diameter are quite small and the
value of 3.sigma. does not exceed 2 .mu.m. For this reason, there
are no useless droplets not contributing to the cleaning, and there
are no harmful droplets that cause damages to the substrate W.
Thus, cleaning efficiency is improved without damages to the
substrate W.
[0084] FIG. 7 is a graph showing a correlation between the droplet
speed of the discharged droplets and the removal rate of
contaminants. As shown in FIG. 7, the higher the droplet speed of
the discharged droplets is, the higher the removal rate of
contaminants is. Since the average droplet speed of the droplets of
the cleaning liquid discharged from the cleaning nozzle 60
according to the present embodiment is in the range from 20 to 60
meters per second, necessary removal performance is attained.
[0085] Additionally, variations in droplet speed are quite small
and the value of 36 does not exceed 5 meters per second. For this
reason, there are few useless droplets not contributing to the
cleaning.
[0086] Also, the cleaning nozzle 60 is provided with the 20
discharge holes 64. In the present embodiment, the total flow rate
of the droplets of the cleaning liquid discharged from the 20
discharge holes 64 toward the substrate W shall be not less than 10
milliliters per minute. FIG. 8 is a graph showing a difference in
the removal rate of contaminants depending on the droplet flow rate
of the discharged droplets. In FIG. 8, the dotted line represents
the removal rate of contaminants when the droplets of the cleaning
liquid are discharged at a droplet flow rate of 1 milliliter per
minute, and the solid line represents the removal rate of
contaminants when the droplets of the cleaning liquid are
discharged at a droplet flow rate of 10 milliliters per minute. The
higher the droplet flow rate is, the higher the cleaning efficiency
is. When the droplets of the cleaning liquid are discharged at a
droplet flow rate of 1 milliliter per minute, it requires 300
seconds to attain a sufficient removal rate. However, when the
droplets are discharged at a droplet flow rate of 10 milliliters
per minute, the same removal rate is attainable in 30 seconds. For
the single wafer type substrate cleaning apparatus 1, it is
generally reasonable that the time required for the cleaning
process of a single substrate W is 30 seconds.
[0087] As described above, the droplets of the cleaning liquid are
discharged from the cleaning nozzle 60 toward the substrate W
during the cleaning process. The average droplet diameter of the
droplets discharged from the cleaning nozzle 60 is in the range
from 15 to 30 .mu.m, and the distribution thereof is such that the
value of 36 does not exceed 2 .mu.m. Also, the average droplet
speed of the discharged droplets is in the range from 20 to 60
meters per second, and the distribution thereof is such that the
value of 36 does not exceed 5 meters per second. Additionally, the
droplet flow rate of the discharged droplets is not less than 10
milliliters per minute. Discharging the droplets of the cleaning
liquid from the cleaning nozzle 60 toward the substrate W while
satisfying these discharge conditions improves the cleaning
efficiency without damages to the substrate W to attain the
sufficient removal rate of contaminants in a short time.
[0088] During the cleaning process, the cleaning nozzle 60 is
pivoted repeatedly between the position over the central portion of
the substrate W and the position over the edge portion thereof The
cleaning process is performed uniformly over the entire surface of
the substrate W. The liquid splashed from the rotating substrate W
by centrifugal force is guided by the drainage guide groove 31 into
the drainage space 22, and is drained through the drainage pipe
27.
[0089] After a lapse of a predetermined period of cleaning
processing time, the valve 76 is opened to stop the discharge of
the droplets from the cleaning nozzle 60, and the nozzle driving
part 50 moves the cleaning nozzle 60 to the retracted position.
Subsequently, the number of rotation of the substrate W is
increased so that the drying process of the substrate W is
performed. After the completion of the drying process, the rotation
of the substrate W is stopped, and the splash guard 30 moves
downwardly. Then, the processed substrate W is transported
outwardly from the spin base 11. Thus, a series of processing
operations in the substrate cleaning apparatus 1 is completed.
Preferably, the position of the splash guard 30 during the cleaning
and drying processes is changed as appropriate depending on the
need for the collection or drainage of the cleaning liquid.
[0090] Although the embodiment according to the present invention
has been described hereinabove, various modifications in addition
to the above may be made therein without departing from the spirit
and scope of the present invention. As an example, the liquid
pressure of the cleaning liquid within the tubular body 61 is not
greater than 10 MPa in the substrate cleaning apparatus 1 according
to the above-mentioned embodiment. However, the liquid pressure is
not limited to this. For example, a higher liquid pressure is
required when the diameter of the discharge holes 64 is smaller
than that of the above-mentioned embodiment.
[0091] Also, in the substrate cleaning apparatus 1 according to the
above-mentioned embodiment, the cleaning liquid is supplied to the
cleaning nozzle 60 even when the cleaning process is not performed,
and is drained to the outside of the apparatus. However, this may
be configured in the form of a circulation system. Specifically, a
pipe downstream from the valve 76 is connected through a filter to
the cleaning liquid supply source 71 so that the cleaning liquid
from the cleaning nozzle 60 flows back to the cleaning liquid
supply source 71.
[0092] The substrate cleaning apparatus 1 according to the
above-mentioned embodiment is suitable for the cleaning of a
semiconductor substrate as the substrate W, but the cleaning
technique according to the present invention may be applied to the
cleaning of other types of substrates W. Examples of other types of
substrates W include a glass substrate for a liquid crystal display
device, and a ceramic plate such as a dish.
[0093] FIG. 9 is a view showing a substrate cleaning apparatus for
performing a cleaning process on a substrate W including other
types. The substrate W is held by a support base 111. The cleaning
nozzle 60 serving as a cleaning head is moved relative to the
substrate W held by the support base 111. The cleaning nozzle 60
may be moved over the substrate W by a sliding movement mechanism
not shown or the support base 111 may be driven, with the cleaning
nozzle 60 held fixed. Also, the cleaning nozzle 60 may be moved
manually.
[0094] The construction of the cleaning nozzle 60 is similar to
that described in the above-mentioned embodiment with reference to
FIGS. 2 and 3. Specifically, while feeding a cleaning liquid to the
cleaning nozzle 60, the valve 76 is closed to increase the liquid
pressure of the cleaning liquid within the tubular body 61. At the
same time, the piezoelectric element 62 applies vibrations to the
cleaning liquid within the tubular body 61. This causes droplets of
the cleaning liquid to be produced and discharged from the 20
discharge holes 64. Contaminants deposited on the substrate W are
physically removed by the droplets discharged from the cleaning
nozzle 60.
[0095] For the cleaning of the substrate W including other types,
the controller 90 controls the pressure pump 72 to adjust the
liquid pressure of the cleaning liquid within the tubular body 61,
and controls the power supply 65 to adjust the vibrations applied
to the cleaning liquid, thereby specifying the discharge conditions
of the droplets discharged from the 20 discharge holes 64. When it
comes to the droplet diameter, the average droplet diameter of the
droplets of the cleaning liquid discharged from the 20 discharge
holes 64 toward the substrate W shall be in the range from 15 to
200 .mu.m. As in the above-mentioned embodiment, the droplet
diameter of the droplets discharged from the cleaning nozzle 60 is
not widely distributed over the range from 15 to 200 .mu.m but
variations in the droplet diameter are quite small. Specifically,
the distribution of the droplet diameter is such that the value of
3.sigma. (where a is a standard deviation) does not exceed 10% of
the average droplet diameter.
[0096] FIG. 10 is a graph showing distributions of the droplet
diameter of the cleaning liquid. Droplets having a distribution DA
are relatively small in average droplet diameter and are suitable
for the cleaning of semiconductor substrates. On the other hand,
droplets having a distribution DB are relatively large in average
droplet diameter and are suitable for the cleaning of ceramic
plates. The distributions of the droplet diameter of the droplets
discharged from the cleaning nozzle 60 are so narrow that the value
of 3.sigma. does not exceed 10% of the average droplet diameter,
independently of the average droplet diameter, and there is little
variation in the droplet diameter. For this reason, there are no
useless droplets not contributing to the cleaning, and there are no
harmful droplets that cause damages to the substrate W. Thus, the
cleaning efficiency is improved without damages to the substrate W.
However, as the average droplet diameter increases, the variations
increase gradually. When the average droplet diameter exceeds 200
.mu.m, it is difficult that the value of 3.sigma. is equal to or
less than 10% of the average droplet diameter in the distribution
of the droplet diameter. In the light of the manufacture of the
cleaning nozzle 60, the average droplet diameter exceeding 200
.mu.m is not practical because the variations cannot be
suppressed.
[0097] When it comes to the droplet speed, the average droplet
speed of the droplets of the cleaning liquid discharged from the 20
discharge holes 64 toward the substrate W shall be in the range
from 20 to 100 meters per second. Like the droplet diameter, the
droplet speed of the droplets discharged from the cleaning nozzle
60 is not widely distributed over the range from 20 to 100 meters
per second but variations in the droplet speed are quite small.
Specifically, the distribution of the droplet speed is such that
the value of 3.sigma. (where .sigma. is a standard deviation) does
not exceed 10% of the average droplet speed. The liquid pressure of
the cleaning liquid supplied to the cleaning nozzle 60 is not
limited to 10 MPa or lower, but the supply of the cleaning liquid
at a higher liquid pressure is required depending on conditions
such as the diameter of the discharge holes 64.
[0098] FIG. 11 is a graph showing distributions of the droplet
speed of the cleaning liquid. Depending on the type of substrate W
to be cleaned, droplets relatively low in average droplet speed as
represented by a distribution DC may be used or droplets relatively
high in average droplet speed as represented by a distribution DD
may be used. The distributions of the droplet speed of the droplets
discharged from the cleaning nozzle 60 are so narrow that the value
of 3.sigma. does not exceed 10% of the average droplet speed,
independently of the average droplet speed, and there is little
variation in the droplet diameter. For this reason, there are few
useless droplets not contributing to the cleaning. However, as the
average droplet speed increases, the variations increase
gradually.
[0099] When the average droplet speed exceeds 100 meters per
second, it is difficult that the value of 36 is equal to or less
than 10% of the average droplet speed in the distribution of the
droplet speed.
[0100] When it comes to the droplet flow rate, the total flow rate
of the droplets of the cleaning liquid discharged from the 20
discharge holes 64 toward the substrate W shall be not less than 10
milliliters per minute. Discharging the droplets of the cleaning
liquid from the cleaning nozzle 60 toward the substrate W while
satisfying these discharge conditions depending on the type of
substrate W eliminates useless droplets not contributing to the
cleaning and harmful droplets that cause damages to the substrate W
to improve the cleaning efficiency without damages to the substrate
W, thereby attaining the sufficient removal rate of contaminants in
a short time.
[0101] In the above-mentioned embodiment, the droplets of the
cleaning liquid are discharged from the cleaning nozzle 60 of the
cylindrical shape under the above-mentioned discharge conditions.
However, the configuration of the cleaning nozzle 60 is not limited
to this. FIG. 12 is a view showing another example of the cleaning
nozzle.
[0102] A cleaning nozzle 160 shown in FIG. 12 is configured such
that a piezoelectric element 162 is affixed to a tubular body 161
having the shape of a quadrangular prism. The tubular body 161 has
an outside shape of a quadrangular prism, and includes a hollow
interior space having the shape of a quadrangular prism. The
opposite ends of the hollow space of the tubular body 161 are both
open. As in the above-mentioned embodiment, a first end of the
hollow space of the tubular body 161 is connected to the supply
pipe 70, and a second end thereof is connected to the delivery pipe
75 (with reference to FIG. 2). The tubular body 161 may be made of
quartz or ceramics such as zirconia.
[0103] The tubular body 161 has a plurality of (for example, 20)
discharge holes 164 formed in a first side wall surface thereof The
20 discharge holes 164 are arranged in a line in a longitudinal
direction of the tubular body 161. The size of the plurality of
discharge holes 164 and the spacing therebetween are identical with
the size of the plurality of discharge holes 64 of the
above-mentioned embodiment and the spacing therebetween,
respectively. The first side wall surface formed with the plurality
of discharge holes 164 has a width of 10 mm. The piezoelectric
element 162 is affixed to the outside wall surface of a second side
wall (a side wall opposed to the side wall provided with the
plurality of discharge holes 164) of the tubular body 161. The
piezoelectric element 162 is electrically connected to the power
supply 65. The power supply 65 applies an alternating voltage
having a predetermined frequency to the piezoelectric element
162.
[0104] The overall construction of the substrate cleaning apparatus
including the cleaning nozzle 160 and the construction around the
cleaning nozzle 160 are identical with those of the above-mentioned
embodiment. The cleaning liquid always continues to be fed to the
cleaning nozzle 160. When the cleaning process is performed, the
valve 76 is closed, whereby the cleaning liquid is discharged from
the plurality of discharge holes 164. Also, when the cleaning
process is performed, the piezoelectric element 162 applies
vibrations to the cleaning liquid within the tubular body 161.
Thus, droplets of the cleaning liquid are produced and discharged
from the plurality of discharge holes 164, as in the
above-mentioned embodiment.
[0105] The cleaning nozzle may be configured as shown in FIG. 13. A
cleaning nozzle 260 shown in FIG. 13 includes a tubular body 261
having the shape of a polygonal prism. The tubular body 261 has an
outside shape of a polygonal prism, and includes a hollow interior
space having the shape of a polygonal prism. The opposite ends of
the hollow space of the tubular body 261 are both open. As in the
above-mentioned embodiment, a first end of the hollow space of the
tubular body 261 is connected to the supply pipe 70, and a second
end thereof is connected to the delivery pipe 75 (with reference to
FIG. 2). The tubular body 261 may be made of quartz or ceramics
such as zirconia.
[0106] The tubular body 261 has a plurality of (for example, 20)
discharge holes 264 formed in a first side wall surface thereof and
arranged in a line. The size of the plurality of discharge holes
264 and the spacing therebetween are identical with the size of the
plurality of discharge holes 64 of the above-mentioned embodiment
and the spacing therebetween, respectively. A piezoelectric element
262 is affixed to the outside wall surface of a side wall opposed
to the side wall provided with the plurality of discharge holes
264. The piezoelectric element 262 is electrically connected to the
power supply 65.
[0107] The overall construction of the substrate cleaning apparatus
including the cleaning nozzle 260 and the construction around the
cleaning nozzle 260 are identical with those of the above-mentioned
embodiment. The cleaning liquid always continues to be fed to the
cleaning nozzle 260. When the cleaning process is performed, the
valve 76 is closed, whereby the cleaning liquid is discharged from
the plurality of discharge holes 264. Also, when the cleaning
process is performed, the piezoelectric element 262 applies
vibrations to the cleaning liquid within the tubular body 261.
Thus, droplets of the cleaning liquid are produced and discharged
from the plurality of discharge holes 264, as in the
above-mentioned embodiment.
[0108] The cleaning nozzle may also be configured as shown in FIG.
14. FIG. 14(a) is a vertical sectional view of a cleaning nozzle
360, and FIG. 14(b) is a transverse sectional view of the cleaning
nozzle 360. The cleaning nozzle 360 shown in FIG. 14 includes a
tubular body 361 having the shape of a rectangular parallelepiped.
The interior space of the tubular body 361 is divided into a
plurality of compartments by a plurality of partition plates 365.
The partition plates 365 do not completely separate the plurality
of compartments, but the compartments are in communication with
each other.
[0109] The tubular body 361 is formed with an inlet 366 and an
outlet 367. The inlet 366 and the outlet 367 are in communication
with the interior space of the tubular body 361. The inlet 366 is
connected to the supply pipe 70, and the outlet 367 is connected to
the delivery pipe 75. The tubular body 361 may also be made of
quartz or ceramics such as zirconia.
[0110] Each of the compartments separated by the plurality of
partition plates 365 has a discharge hole 364. The plurality of
discharge holes 364 in the cleaning nozzle 360 are also arranged in
a line. The size of the plurality of discharge holes 364 and the
spacing therebetween are identical with the size of the plurality
of discharge holes 64 of the above-mentioned embodiment and the
spacing therebetween, respectively. A piezoelectric element 362 is
affixed to the outside surfaces of opposite side walls of the
tubular body 361. The piezoelectric element 362 is electrically
connected to the power supply 65.
[0111] The overall construction of the substrate cleaning apparatus
including the cleaning nozzle 360 and the construction around the
cleaning nozzle 360 are identical with those of the above-mentioned
embodiment. The cleaning liquid always continues to be fed to the
cleaning nozzle 360. When the cleaning process is performed, the
valve 76 is closed, whereby the cleaning liquid is discharged from
the plurality of discharge holes 364. Also, when the cleaning
process is performed, the piezoelectric element 362 applies
vibrations to the cleaning liquid within the tubular body 361.
Thus, droplets of the cleaning liquid are produced and discharged
from the plurality of discharge holes 364, as in the
above-mentioned embodiment.
[0112] For the discharge of the droplets of the cleaning liquid
toward the substrate W by using the cleaning nozzle 160 shown in
FIG. 12, the cleaning nozzle 260 shown in FIG. 13 or the cleaning
nozzle 360 shown in FIG. 14, the discharge conditions of the
droplets are similar to those described above. Discharging the
droplets of the cleaning liquid toward the substrate W while
satisfying the above-mentioned discharge conditions eliminates
useless droplets not contributing to the cleaning and harmful
droplets that cause damages to the substrate W to improve the
cleaning efficiency without damages to the substrate W, thereby
attaining the sufficient removal rate of contaminants in a short
time, as in the above-mentioned embodiment.
[0113] Cleaning nozzles other than those shown in FIGS. 2, 3, and
12 to 14 which are capable of discharging droplets of the cleaning
liquid under the above-mentioned discharge conditions may be used
to discharge droplets of the cleaning liquid toward the substrate
W.
[0114] The cleaning liquid is not limited to deionized water but
may be an aqueous solution of liquid chemical for cleaning.
[0115] The overall construction of the substrate cleaning apparatus
1 is not limited to the configuration shown in FIG. 1. For example,
the substrate cleaning apparatus 1 may be provided with a gas
nozzle for ejecting a nitrogen gas toward the substrate W subjected
to the cleaning process to dry the substrate W.
REFERENCE NUMERALS AND CHARACTERS
[0116] 1 substrate cleaning apparatus [0117] 10 rotary holding part
[0118] 11 spin base [0119] 20 processing cup [0120] 30 splash guard
[0121] 50 nozzle driving part [0122] 60, 160, 260, 360 cleaning
nozzles [0123] 61, 161, 261, 361 tubular bodies [0124] 62, 162,
262, 362 piezoelectric elements [0125] 64, 164, 264, 364 discharge
holes [0126] 65 power supply [0127] 70 supply pipe [0128] 75
delivery pipe [0129] 76 valve [0130] 90 controller [0131] 111
support base [0132] W substrate
* * * * *