U.S. patent application number 11/976267 was filed with the patent office on 2008-05-15 for ultrasonic-wave washing unit, ultrasonic-wave washing apparatus, ultrasonic-wave washing method, method of manufacturing a semiconductor device, and method of manufacturing a liquid crystal display.
This patent application is currently assigned to Kabushiki Kaisha Toshiba. Invention is credited to Hiroshi Fujita, Naoaki Sakurai.
Application Number | 20080110473 11/976267 |
Document ID | / |
Family ID | 29767398 |
Filed Date | 2008-05-15 |
United States Patent
Application |
20080110473 |
Kind Code |
A1 |
Sakurai; Naoaki ; et
al. |
May 15, 2008 |
Ultrasonic-wave washing unit, ultrasonic-wave washing apparatus,
ultrasonic-wave washing method, method of manufacturing a
semiconductor device, and method of manufacturing a liquid crystal
display
Abstract
An ultrasonic-wave washing unit comprising an ultrasonic-wave
vibrating plate to which an ultrasonic-wave vibrator is fixed by
adhesive bonding, an ultrasonic-wave transmission plate opposed to
the vibrating plate, a liquid supply means which supplies a liquid
to a space defined between the vibrating plate and the transmission
plate, and a liquid discharge means for discharging the liquid from
the space.
Inventors: |
Sakurai; Naoaki;
(Yokohama-shi, JP) ; Fujita; Hiroshi;
(Yokohama-shi, JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Assignee: |
Kabushiki Kaisha Toshiba
|
Family ID: |
29767398 |
Appl. No.: |
11/976267 |
Filed: |
October 23, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11072326 |
Mar 7, 2005 |
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11976267 |
Oct 23, 2007 |
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10443012 |
May 22, 2003 |
6875696 |
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11072326 |
Mar 7, 2005 |
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Current U.S.
Class: |
134/1 |
Current CPC
Class: |
H01L 21/67259 20130101;
H01L 21/67051 20130101; H01L 21/68 20130101; B08B 3/12 20130101;
H01L 21/67253 20130101 |
Class at
Publication: |
134/001 |
International
Class: |
B08B 3/12 20060101
B08B003/12 |
Foreign Application Data
Date |
Code |
Application Number |
May 23, 2002 |
JP |
2002-149130 |
Claims
1.-6. (canceled)
7. An ultrasonic-wave washing method comprising: moving an
ultrasonic-wave washing unit relatively to a to-be-washed surface
of a to-be-washed object held by means of a retaining means, the
washing unit having a diffusion means, which has one surface to
which an ultrasonic-wave vibrator is fixed and the other surface
opposed to the to-be-washed object and diffuses ultrasonic
vibration from the ultrasonic-wave vibrator, and a cooling means
which cools the diffusion means, thereby bringing the other surface
of the diffusion means to a given distance from the to-be-washed
surface; a step of supplying a detergent to the to-be-washed
surface, thereby filling the gap between the to-be-washed surface
and the other surface of the diffusion means with the detergent;
and a step of driving the ultrasonic-wave vibrator to diffuse and
propagate the ultrasonic vibration propagated through the diffusion
means to the to-be-washed surface, thereby washing the to-be-washed
surface.
8.-16. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2002-149130, filed May 23, 2002, the entire contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an ultrasonic-wave washing
unit, ultrasonic-wave washing apparatus, and ultrasonic-wave
washing method that are suitably used to wash a to-be-washed
object, such as a semiconductor substrate, e.g., a silicon wafer or
compound semiconductor-wafer, which forms a semiconductor device,
or a glass substrate, which forms a liquid crystal display, and a
method of manufacturing a semiconductor device and a method of
manufacturing a liquid crystal display to which these washing
techniques are applied.
[0004] 2. Description of the Related Art
[0005] In a manufacturing process for a semiconductor substrate or
glass substrate for liquid crystal display, submicron particles and
the like that adhere to the semiconductor substrate or glass
substrate must be removed by washing before and after various
precision works. Accordingly, an ultrasonic-wave washing method is
available in which a to-be-washed object is washed with a detergent
that is supplied with high-frequency ultrasonic waves of 500 kHz to
3.0 MHz, which are little damaging.
[0006] More specifically, according to this washing method, an
ultrasonic-wave diffuser that transmits and diffuses ultrasonic
vibration from a vibrator is brought close a to-be-washed surface
of the to-be-washed object, and the detergent is fed into the gap
between the diffuser and the surface. As this is done, the
to-be-washed object is washed with the detergent that is supplied
with the ultrasonic waves.
[0007] The efficiency of ultrasonic-wave washing can be improved by
enhancing ultrasonic-wave energy over the surface of the
to-be-washed object. To attain this, a source of ultrasonic-wave
oscillation is improved, or ultrasonic waves from the oscillation
source are converged to enhance the ultrasonic-wave energy over the
to-be-washed surface, as described in Jpn. Pat. Appln. No.
7-283183.
[0008] However, the output of the source of ultrasonic-wave
oscillation can be increased only limitedly, and a vibrating plate,
an ultrasonic-wave vibrator, and an adhesive agent that is used to
bond these elements together are limited in life performance and
reliability. In order to enhance the ultrasonic-wave energy,
therefore, a method is used to converge the ultrasonic-wave output,
thereby increasing the apparent value of the output.
[0009] Conventionally, as described above, the ultrasonic-wave
energy to be applied to the to-be-washed surface is enhanced by
converging the ultrasonic-wave output. Recently, however, wires and
other patterns formed on substrates have become finer and finer.
Therefore, high-frequency ultrasonic waves, which had
conventionally been regarded as little damaging, have started to
damage the patterns considerably. The inventor hereof closely
examined the principle of occurrence of damage, and ascertained
that ultrasonic waves generated from the ultrasonic-wave vibrator
were converged on a certain point and energy of a level that breaks
the wires or influences their crystals was produced on that point.
Thus, convergence and synthesis of ultrasonic vibration, which had
conventionally been carried out to increase the ultrasonic-wave
energy, were found to be the cause of the damage.
[0010] If there is a wide gap between the ultrasonic-wave diffuser
and the to-be-washed object, the necessary quantity of detergent to
fill the gap increases, thus entailing higher cost. Accordingly,
the diffuser must be brought as close to the surface of the
to-be-washed object as possible. If the gap is too narrow, however,
the surface of the object is finely undulating and its thickness is
uneven. If the ultrasonic-wave washing unit is moved in a fixed
height position, therefore, the diffuser and the to-be-washed
object touch each other, so that the wires and the like on the
surface of the object may be broken.
BRIEF SUMMARY OF THE INVENTION
[0011] The object of the present invention is to subject a
to-be-washed object to ultrasonic-wave washing without damaging
it.
[0012] An ultrasonic-wave washing unit according to the invention
comprises: an ultrasonic-wave vibrator; diffusion means which
diffuses ultrasonic vibration generated by means of the
ultrasonic-wave vibrator; and cooling means which cools the
diffusion means.
[0013] An ultrasonic-wave washing apparatus of the invention
comprises retaining means which holds a to-be-washed object and an
ultrasonic-wave washing unit movable relatively to a to-be-washed
surface of the object, the ultrasonic-wave washing unit having
diffusion means, which has one surface to which an ultrasonic-wave
vibrator is fixed and the other surface opposed to the to-be-washed
object and diffuses ultrasonic vibration from the ultrasonic-wave
vibrator, and cooling means which cools the diffusion means, the
ultrasonic-wave washing apparatus further comprising detergent
supply means which supplies a detergent to the to-be-washed
surface.
[0014] An ultrasonic-wave washing method of the invention
comprises: a step of moving an ultrasonic-wave washing unit
relatively to a to-be-washed surface of a to-be-washed object held
by means of retaining means, the washing unit having diffusion
means, which has one surface to which an ultrasonic-wave vibrator
is fixed and the other surface opposed to the to-be-washed object
and diffuses ultrasonic vibration from the ultrasonic-wave
vibrator, and cooling means which cools the diffusion means,
thereby bringing the other surface of the diffusion means to a
given distance from the to be-washed surface; a step of supplying a
detergent to the to-be-washed surface, thereby filling the gap
between the to-be-washed surface and the other surface of the
diffusion means with the detergent; and a step of driving the
ultrasonic-wave vibrator to diffuse and propagate the ultrasonic
vibration propagated through the diffusion means to the
to-be-washed surface, thereby washing the to-be-washed surface.
[0015] A method of manufacturing a semiconductor device of the
invention comprises: a step of forming a gate insulating film on a
semiconductor substrate; a step of forming a gate conductor on the
gate insulating film; a step of forming a gate cap on the gate
conductor; a step of etching the gate conductor to the depth of the
gate insulating film in accordance with a mask pattern of the gate
cap; and a step of washing the surface by using the aforesaid
ultrasonic-wave washing method.
[0016] A method of manufacturing a liquid crystal display of the
invention comprises: a step of successively forming an SiN film,
SiO.sub.2 film, and a-Si film on a glass substrate for the liquid
crystal display; a step of annealing the a-Si film by means of a
laser, thereby polymerizing the film; a step of etching the
polymerized Si film, thereby forming an island of poly-Si; and a
step of washing the surface by using the aforesaid ultrasonic-wave
washing method.
[0017] An ultrasonic-wave washing apparatus of the invention, which
washes a to-be-washed surface of a to-be-washed object with a
detergent to which ultrasonic waves are applied, comprises:
retaining means which holds the to-be-washed object; an
ultrasonic-wave washing unit opposed to the to-be-washed surface of
the to-be-washed object held by the retaining means; and
positioning means which positions the ultrasonic-wave washing unit
with respect to the to-be-washed surface of the to-be-washed
object, the ultrasonic-wave washing unit including diffusion means
which has one surface to which an ultrasonic-wave vibrator is fixed
and the other surface opposed to the to-be-washed object and
diffuses ultrasonic vibration from the ultrasonic-wave vibrator;
detergent supply means which supplies a detergent to the
to-be-washed surface of the to-be-washed object; and measuring
means which measures a relative distance between the diffusion
means and the to-be-washed surface, the positioning means having
control means which positions the ultrasonic-wave washing unit so
as to maintain a given distance between the diffusion means and the
to-be-washed surface in accordance with the output of the measuring
means.
[0018] An ultrasonic-wave washing method of the invention
comprises: a positioning step of moving an ultrasonic-wave washing
unit relatively to a to-be-washed surface of a to-be-washed object,
the washing unit having diffusion means which has one surface to
which an ultrasonic-wave vibrator is fixed and the other surface
opposed to the to-be-washed object and diffuses ultrasonic
vibration from the ultrasonic-wave vibrator, thereby bringing the
other surface of the diffusion means to a given distance from the
to-be-washed surface; a detergent supply step of supplying a
detergent to the to-be-washed surface, thereby filling the gap
between the to-be-washed surface and the other surface of the
diffusion means with the detergent; a washing step of driving the
ultrasonic-wave vibrator to diffuse and propagate the ultrasonic
vibration propagated through the diffusion means to the
to-be-washed surface, thereby washing the to-be-washed surface; and
a measuring step of measuring a relative distance between the other
surface of the diffusion means and the to-be-washed surface, the
positioning step having a control step of maintaining a given
distance between the diffusion means and the to-be-washed surface
in accordance with the relative distance measured in the measuring
step.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0019] FIG. 1 is a sectional view of an ultrasonic-wave washing
apparatus of a leaf-spin washing type according to the present
invention;
[0020] FIG. 2 is a partial perspective view of an ultrasonic-wave
washing unit;
[0021] FIG. 3 is a sectional view of the ultrasonic-wave washing
unit;
[0022] FIG. 4 is a plan view showing the relation between a
to-be-washed object and the ultrasonic-wave washing unit;
[0023] FIG. 5 is a vertical sectional view showing the relation
between the to-be-washed object and the ultrasonic-wave washing
unit;
[0024] FIGS. 6A, 6B and 6C are diagrams showing the waveforms of
ultrasonic waves repeatedly applied in an on-off manner;
[0025] FIG. 7A is a diagram showing the waveform of ultrasonic
waves of which the phase is shifted by 180.degree. during
continuous irradiation;
[0026] FIG. 7B is a diagram showing the waveform of ultrasonic
waves of which the wavelength (pulse width) is changed during the
continuous irradiation;
[0027] FIG. 7C is a diagram showing the waveform of ultrasonic
waves of which the amplitude (pulse output) is changed during the
continuous irradiation;
[0028] FIGS. 8A, 8B and 8C are views showing steps of forming an
active area and a gate conductor in a manufacturing process for a
semiconductor device;
[0029] FIG. 9 is a view showing a first modification of an
ultrasonic-wave application means;
[0030] FIG. 10 is a view showing a second modification of the
ultrasonic-wave application means;
[0031] FIG. 11 is a view showing a third modification of the
ultrasonic-wave application means;
[0032] FIG. 12 is a view showing a fourth modification of the
ultrasonic-wave application means;
[0033] FIG. 13 is a view showing a fifth modification of the
ultrasonic-wave application means;
[0034] FIG. 14A is a view showing a sixth modification of the
ultrasonic-wave application means;
[0035] FIG. 14B is a sectional view taken along line Q-Q of FIG.
14A;
[0036] FIG. 15 is a side view of an ultrasonic-wave washing
apparatus according to a second embodiment of the invention;
[0037] FIG. 16 is a vertical sectional view of an ultrasonic-wave
washing unit incorporated in the ultrasonic-wave washing
apparatus;
[0038] FIG. 17 is a plan view showing the relation between the
ultrasonic-wave washing unit of the ultrasonic-wave washing
apparatus and the to-be-washed object; and
[0039] FIG. 18 is a bottom view showing a modification of the
ultrasonic-wave washing unit.
DETAILED DESCRIPTION OF THE INVENTION
[0040] An ultrasonic-wave washing unit according to a first
embodiment of present invention and an ultrasonic-wave washing
apparatus using the same will now be described with reference to
the accompanying drawings. FIG. 1 is a sectional view of the
ultrasonic-wave washing apparatus of a leaf-spin washing type of
the invention. FIG. 2 is a partial perspective view of the
ultrasonic-wave washing unit. FIG. 3 is a sectional view of the
ultrasonic-wave washing unit. FIG. 4 is a plan view showing the
relation between a to-be-washed object and the ultrasonic-wave
washing unit. FIG. 5 is a vertical sectional view.
[0041] An ultrasonic-wave washing apparatus 10 comprises a spinning
device 12 and an ultrasonic-wave washing unit 14. The spinning
device 12 holds a to-be-washed object 11, such as a silicon wafer
or some other semiconductor substrate, glass substrate for a liquid
crystal display, etc. The washing unit 14 supplies a detergent 13
to the object 11 and applies ultrasonic waves to the detergent 13,
thereby washing a to-be-washed surface 11a of the object 11.
[0042] In FIG. 1, numeral 15 denotes a cup in the form of a
bottomed cylinder. The bottom of the cup 15 is provided with
discharge ports 16 through which the detergent 13 is discharged.
The upper part of the cup 15 is inclined toward its center in order
to prevent the detergent 13 scattered from the to-be-washed object
11 from being reflected by the inner wall of the cup 15 and
rebounded on the object 11 and to guide the detergent 13 to the
discharge ports 16. A rotating shaft 18 that is coupled to the
shaft of a motor 17 substantially penetrates the center of the
lower part of the cup 15. The shaft 18 is rotatably supported by
means of a bearing 19 that is attached to the cup 15. The center of
rotation of a rotating stage 20 is fixed to the top of the shaft
18. A plurality of support pins 21 are arranged at equal spaces in
a ring along the outer periphery of the stage 20. The pins 21
fixedly support the object 11. The rotating stage 20 and the
support pins 21 constitute retaining means.
[0043] An arm 22 is located in a position opposite the to-be-washed
surface 11a of the to-be-washed object 11. It is movable in the
direction of arrow T (direction toward and away from the object 11)
and the direction of arrow R (direction parallel to the surface
11a). The ultrasonic-wave washing unit 14 is mounted on the distal
end portion of the arm 22. The washing unit 14 comprises nozzles 23
and an ultrasonic-wave application means 24. The nozzles 23 supply
the detergent 13 to the to-be-washed surface 11a of the object 11.
The ultrasonic-wave application means 24 applies ultrasonic waves
to the detergent 13 on the surface 11a.
[0044] Although only one nozzle 23 is shown in FIG. 1, a plurality
of nozzles 23 should preferably be arranged in the manner shown in
FIG. 4. More specifically, the detergent 13 is supplied to the
upper-stream side of the to-be-washed object 11 that faces the
ultrasonic-wave application means 24 when the object 11 rotates in
the direction of arrow C. In FIG. 1, three nozzles 23a, 23b and 23c
are arranged under the application means 24 on the left-hand side
of the object 11. On the right-hand side of the object 11, three
nozzles 23d, 23e and 23f are arranged over the application means
24. With this arrangement, the ultrasonic waves can be efficiently
applied to the detergent 13, so that the washing effect can be
improved.
[0045] Since the to-be-washed object 11 is rotated according to the
present embodiment, the nozzles 23 are arranged in the manner
described above. If the object 11 is transported straight by means
of a belt conveyor, for example, the nozzles 23 should only be
arranged on the upper-stream side of the ultrasonic-wave
application means 24 with respect to the direction of
transportation of the object 11. The location of the nozzles 23 is
not limited to the case of the present embodiment, and they may be
located in any other suitable positions such that the surface of
the object 11 can be sufficiently supplied with the detergent.
[0046] According to the present embodiment, moreover, the nozzles
23 are arranged separately from the ultrasonic-wave application
means 24. Alternatively, however, they may be formed integrally
with the application means 24 or designed so that the detergent 13
can be supplied to the to-be-washed object 11 along the surface of
an ultrasonic-wave transmission plate 28 (mentioned later).
[0047] Preferably, the detergent 13 should be discharged from the
nozzles 23a to 23f at different rates. More specifically, the
to-be-washed object 11 rotates in the direction of arrow C, so that
the detergent 13 that is supplied to the center of the object 11 is
caused to flow toward the outer periphery by centrifugal force. In
order to supply the detergent 13 substantially uniformly to the
surface of the to-be-washed surface 11a of the object 11,
therefore, the detergent 13 is discharged at the highest rate from
the nozzles 23c and 23d on the center side of the object 11, at the
second highest rate from the nozzles 23b and 23e, and at the lowest
rate from the nozzles 23a and 23f.
[0048] Since the to-be-washed object 11 is rotated according to the
present embodiment, the detergent is discharged at different rates
from the nozzles 23a to 23f, as described above. If the object 11
is transported straight, however, the detergent may be discharged
at the same rate.
[0049] As is shown in detail in FIGS. 2 and 3, the ultrasonic-wave
application means 24 includes ultrasonic-wave diffusion means,
which is composed of an ultrasonic-wave vibrator 25 based on lead
titanate, for example, an ultrasonic-wave vibrating plate 26, and
the ultrasonic-wave transmission plate 28. The vibrating plate 26,
to which the vibrator 25 is bonded, transmits vibration of the
vibrator 25. The transmission plate 28 is opposed to the vibrating
plate 26 and, in conjunction with the vibrator 25, defines a space
27. The vibrator 25 may be a piezoelectric device.
[0050] The oscillation frequency of the ultrasonic-wave vibrator 25
ranges from 500 kHz to 8 MHz. It generates heat as it vibrates. If
the ultrasonic-wave vibrating plate 26 is non-loaded, the vibrator
25 may be destroyed by its own vibration and heat generation.
Further, the heat generation causes an adhesive agent (e.g., epoxy
thermosetting adhesive agent) that bonds the vibrator 25 and the
vibrating plate 26 together to reach a temperature corresponding to
its heat resistance or higher temperature. Inevitably, therefore,
the state of bond is worsened, so that the transmission of
ultrasonic vibration suffers a loss.
[0051] Accordingly, the ultrasonic-wave transmission plate 28 is
provided with coolant supply ports (liquid supply means) 29,
through which a coolant (liquid) such as water is fed into the
space 27, and coolant discharge ports (liquid discharge means) 30,
through which the coolant is discharged. These ports serve as means
for applying load to the ultrasonic-wave vibrating plate 26 and as
cooling means for cooling the adhesive agent that bonds the
vibrator 25 and the vibrating plate 26 together.
[0052] In carrying out ultrasonic-wave washing, moreover, the
washing effect can be improved if the temperature of the detergent
is high. If the high-temperature detergent directly touches the
ultrasonic-wave vibrating plate 26 to which the ultrasonic-wave
vibrator 25 is bonded, however, the durability of the adhesive
agent that bonds them is extremely lowered, so that the detergent
cannot be heated to high temperature. As ultrasonic waves are
applied to the detergent that indirectly touches the
ultrasonic-wave transmission plate 28 through the medium of the
aforesaid coolant, however, thermal damage to the adhesive agent
need not be considered, so that a high-temperature detergent can be
utilized.
[0053] The number of coolant supply and discharge ports 29 and 30
may be suitably selected depending on the size of the
ultrasonic-wave washing unit 14. These ports 29 and 30 are
connected to a source of coolant supply and coolant discharge means
(not shown) through the interior of the arm 22.
[0054] For example, an RF power source (not shown) is connected to
the ultrasonic-wave vibrator 25 by means of a supply line 25a.
Generation of ultrasonic vibration is controlled by driving the RF
power source. The ultrasonic-wave vibrating plate 26 is formed of a
flat quartz plate, single-crystal sapphire, SiC, alumina, SUS, or
Ta plate. The ultrasonic-wave transmission plate 28 is convex on
the side opposite from the vibrating plate 26. Like the vibrating
plate 26, it is formed of quartz, single-crystal sapphire, SiC,
alumina, SUS, or Ta plate. Since the transmission plate 28 directly
touches the detergent 13, its constituents may possibly liquate out
and contaminate the to-be-washed object 11, depending on the kind
of the detergent. Therefore, the material of the transmission plate
28 must be suitably selected according to the kind of the detergent
13 used.
[0055] As shown in FIG. 4, the length of the ultrasonic-wave
application means 24 is a little greater than the diameter of the
to-be-washed object 11 (silicon wafer). As the object 11 rotates
for 180.degree. in this arrangement, its whole surface can be
washed in the main. However, the length of the application means 24
may be suitably changed depending on the size of the object 11. If
the object 11 is circular, as shown in FIG. 4, for example, the
length of the application means 24 may be made a little greater
than the diameter of the object 11, as described above, or than its
radius, so that the range from the center of rotation to the outer
periphery can be covered. Alternatively, the application means 24
may be made so small that ultrasonic vibration can be applied
spottedly. If the to-be-washed object 11 is a square substrate
(e.g., glass substrate for liquid crystal display) that is
transported straight, its whole surface can be efficiently washed
in the main as it passes under the application means 24 provided
that the length of the application means 24 is a little greater
than the width of the object 11. A region 28a indicated by broken
line in FIG. 4 represents a portion in which the ultrasonic-wave
transmission plate 28 (mentioned later) and the object 11 connect
with each other by means of the detergent 13.
[0056] The principle of washing in the ultrasonic-wave washing
apparatus 10 will now be described also with reference to FIG. 5.
The gap between the to-be-washed surface 11a of the to-be-washed
object 11 and the ultrasonic-wave transmission plate 28 of the
ultrasonic-wave application means 24 is approximated to 0.5 mm or
more, e.g., to about 1 mm, and the detergent 13 is supplied to the
gap. If this is done, the detergent 13 touches the transmission
plate 28 and uses its surface tension to form a convex on the plate
28, as shown in FIG. 5. On the other hand, vibration that is
produced by the ultrasonic-wave vibrator 25 is transmitted from the
ultrasonic-wave vibrating plate 26 to the transmission plate 28
through the coolant that fills the space 27. The ultrasonic waves
having reached the transmission plate 28 are radially diffused by
the curved convex of the transmission plate 28 and applied to the
detergent 13. Thus, the ultrasonic is waves that are diffused by
the transmission plate 28 never converge on the detergent 13 or the
to-be-washed surface 11a, and no convergent points for ultrasonic
energy that surpasses energy generated for each unit area can be
produced. In consequence, the ultrasonic waves can be restrained
from damaging any convex structures such as wires on the surface
11a or members that are exposed in the surface of the object
11.
[0057] The following is a description of a washing method that
utilizes the ultrasonic-wave washing apparatus 10 constructed in
this manner. First, the to-be-washed object (e.g., silicon wafer)
11 is delivered to and fixedly supported on the support pins 21
that are arranged in a ring on the rotating stage 20 from which the
arm 22 is evacuated. As this is done, the ultrasonic-wave
application means 24 is moved to washing means (not shown) that is
located outside the cup 15, whereupon the surface of the
ultrasonic-wave transmission plate 28 that is in contact with the
detergent 13 can be washed. Then, the arm 22 is rocked and driven
to move the ultrasonic-wave washing unit 14 horizontally over the
to-be-washed object 11 and further to lower it so that a given gap
is formed between the surface of the object 11 and the apex of the
transmission plate 28 of the application means 24.
[0058] After the to-be-washed object 11 and the ultrasonic-wave
application means 24 are situated in a given relation, the motor 17
is driven to rotate the object 11 in the direction of arrow C so
that the detergent 13 is supplied to the to-be-washed surface 11a
of the object 11 through the nozzles 23a to 23f. When the detergent
13 is fed in a given quantity onto the surface 11a, it fills the
gap between the ultrasonic-wave transmission plate 28 and the
surface 11a and connects them in the region 28a, as shown in FIG.
5. If the ultrasonic-wave vibrator 25 is actuated in this state,
ultrasonic vibration is transmitted to the to-be-washed surface 11a
of the object 11 through the ultrasonic-wave vibrating plate 26,
coolant that fills the space 27, transmission plate 28, and
detergent 13. Thus, the ultrasonic vibration can remove particles
and the like that adhere to the surface 11a. After the washing
operation, the detergent 13 is scattered toward the outer periphery
by centrifugal force that is produced as the object 11 rotates and
is discharged from the discharge ports 16.
[0059] The following is a description of a method of driving the
ultrasonic-wave vibrator 25. Recently, wires formed on the surface
of substrates such as silicon wafers have been made finer and
finer. In some cases, therefore, the wires may be damaged even by
ultrasonic waves in a band that has conventionally been
nondamaging. According to the present embodiment, the ultrasonic
waves are applied not continuously but repeatedly in an on-off
manner. In an alternative method, ultrasonic waves of a plurality
of types having different phases, wavelengths, or amplitudes are
changed by stages and applied continuously. This method will now be
described specifically.
[0060] FIGS. 6A, 6B and 6C show the waveforms of ultrasonic waves
that are repeatedly applied in an on-off manner. FIG. 6A shows a
case in which carrier waves of 100 Hz are superimposed on
ultrasonic waves. FIG. 6B shows a case in which carrier waves of
200 Hz are superimposed, and FIG. 6C shows a case in which carrier
waves of 1,000 Hz are superimposed. As the ultrasonic waves are
thus repeatedly applied in an on-off manner, crystals that
constitute the wires and substrates resonate with the on-state
ultrasonic waves. When the application of the ultrasonic waves is
switched off in a given time, however, the resonance is stopped.
Thus, the resonance can be prevented from attaining a level such
that it damages the wires or crystals.
[0061] FIGS. 7A, 7B and 7C show the waveforms of a plurality of
ultrasonic waves with different phases, wavelengths, and amplitudes
that are applied continuously, not in an on-off manner. FIG. 7A
shows a case in which the phase is shifted for 180.degree. with
every 80 pulses during the continuous irradiation. FIG. 7B shows a
case in which the wavelength (pulse width) is changed during the
continuous irradiation and 80 pulses of 1,590 Hz and 40 pulses of
749 Hz are applied alternately. If the changed wavelength is an
integral multiple or submultiple of the original wavelength, in
this case, however, resonance occurs inevitably, so that the
wavelength should be of any other value. FIG. 7C shows a case in
which the amplitude (pulse output) is changed with every given time
with the phase unchanged during the continuous irradiation and 80
pulses of 30 Hz and 80 pulses of 5 Hz are applied alternately.
According to these methods of irradiation, ultrasonic waves that
cancel the resonance in the wires and crystals are changed as they
are applied. Thus, the incidence of damage can be lowered to a
hundredth of a value for the case where specific ultrasonic waves
continue to be applied. In the case described above, ultrasonic
waves of two types are changed as they are applied. Alternatively,
however, ultrasonic waves of three or more types may be changed as
they are applied. Alternatively, moreover, ultrasonic waves of a
plurality of types may be superposed so that the types are changed
with every given timing to restrain resonance.
[0062] The ultrasonic-wave vibrator 25, vibrating plate 26,
transmission plate 28, and the adhesive agent that bonds the
vibrator 25 and the vibrating plate 26 deteriorate with time.
Therefore, the state of the ultrasonic waves in the gap between the
transmission plate 28 and the to-be-washed surface 11a or in the
space 27 is detected by means of a sensor. Based on the result of
this detection, the RF power source that drives the vibrator 25 is
subjected to feedback control, and the timing for the replacement
of each component can be recognized.
[0063] The following is a description of the case where the
ultrasonic-wave washing method of the present embodiment is applied
to an active area of a semiconductor device and the manufacture of
a liquid crystal cell of a liquid crystal display.
[0064] FIGS. 8A, 8B and 8C are views showing steps of forming the
active area and a gate conductor in a manufacturing process for the
semiconductor device. If the design rule is not very tight, damage
to the wires and the like is not a critical problem. It is known,
however, that the wires and the like are liable to damage if the
design rule is as tight as the level of 0.2 .mu.m.
[0065] First, a gate insulating film (gate oxide film) is formed on
a semiconductor substrate that is formed of a silicon wafer, for
example, and the gate conductor is formed on the insulating film.
Subsequently, an SiN film that constitutes a gate cap, for example,
is formed on the gate conductor, and a resist film is formed on the
SiN film. Then, the resist film is exposed and developed to be
patterned, whereupon a mask is formed. Thereafter, the SiN film is
etched to form the gate cap (FIG. 8A). Then, the resist film having
been used as the mask is removed, and the surface is washed.
Thereafter, the gate conductor is etched to the depth of the gate
insulating film in accordance with a mask pattern of the gate cap
(FIG. 8B). After the surface is washed, a spacer of an oxide film
is formed around the sidewall of the gate (FIG. 8C), whereupon the
gate of, for example, a DRAM is completed.
[0066] In the manufacturing process for the semiconductor device
described above, the surface must be cleaned in order to form
another layer thereon after an etching step or the like. The
ultrasonic-wave washing method of the present invention is an
effective method to meet this requirement. If the design rule is on
the level of 0.2 .mu.m (0.7 .mu.m or less for a metallic wire) and
if the aspect ratio (H/W in FIG. 8C) is 1 or more, a wire is
inevitably flattened in a portion indicated by symbol .alpha. in
FIG. 8B or symbol .beta. in FIG. 8C according to the conventional
ultrasonic-wave washing method. Thus, according to the conventional
method, the incidence of defective patterns increases, and the
yield rate may possibly lower to 50% or less. According to the
ultrasonic-wave washing method of the present invention, on the
other hand, damage to the wires and the like can be minimized, and
the yield rate can be approximated to 100%.
[0067] The following is a description of an example of a step of
forming a gate on the glass substrate that constitutes the liquid
crystal cell of the poly-Si-TFT liquid crystal display. The
processing area of the liquid crystal display is greater than that
of the semiconductor device. The opening of the display is expected
to be widened in order to improve the display capacity. Thus, the
pixel section must be increased, and peripheral circuit sections,
such as a driver, must be reduced in size.
[0068] After the SiN film, an SiO.sub.2 film, and an a-Si film are
formed, in a fundamental step, the surface of the a-Si film is
washed. Thereafter, the a-Si film is annealed to be polymerized by
means of a laser, whereupon a mask is formed. After the poly-Si
film is etched to form an island of poly-Si that serves as the
gate, its surface is washed. After an insulating film and a metal
film are formed on the surface of the glass substrate that includes
the poly-Si island, a resist is spread and exposed to form a mask,
and the metal film is etched to form a gate wire.
[0069] In the manufacturing process for the liquid crystal display,
a wider area than in the semiconductor device must be washed in a
short time, so that ultrasonic-wave washing requires high power. In
the case of the conventional ultrasonic-wave washing method, the
glass substrate has about ten damaged regions, which are few. Since
the liquid crystal display has no redundant circuits, however, it
can be fatally affected by a single damaged region. It is
empirically recognized that the number of damaged regions can be
reduced substantially to zero according to the ultrasonic-wave
washing method of the present embodiment.
[0070] If the ultrasonic-wave washing is carried out in this manner
by using the ultrasonic-wave washing apparatus according to the
present embodiment, damage to the wires or to the crystalline state
of substances that constitute the substrates and the like can be
minimized, and the yield rate in the manufacturing processes for
the semiconductor device and liquid crystal display can be improved
considerably.
[0071] The following is a description of modifications of the
ultrasonic-wave application means according to the embodiment
described above. FIG. 9 shows a first modification of the
ultrasonic-wave application means 24. Ultrasonic-wave application
means 40 has a pair of support portions 41a and 41b. Between the
support portions 41a and 41b, a space 45 is defined by a part of
each support portion, an ultrasonic-wave vibrating plate 43, an
ultrasonic-wave transmission plate 44, and a pair of side plates
(not shown). An ultrasonic-wave vibrator 42 is fixed to the
vibrating plate 43 by adhesive bonding. The transmission plate 44
is a plate member that in convex on one side. The one support
portion 41a is provided with a coolant supply port 46a (or a
plurality of ports 46a arranged in the longitudinal direction of
the application means 40) through which the coolant is introduced
into the space 45. The other support portion 41b is provided with a
coolant discharge port 46b (or a plurality of ports 46b arranged in
the same manner as the supply ports 46a) through which the coolant
is discharged. The ultrasonic-wave application means 40 constructed
in this manner facilitates manufacture. Since the members are
constructed independently, moreover, the maintenance and the
replacement of the members can be carried out smoothly and
easily.
[0072] FIG. 10 shows a second modification of the ultrasonic-wave
application means. Like numerals are used to designate like
portions of the first and second modifications, and a description
of those portions is omitted. Ultrasonic-wave application means 50
has a pair of support portions 51a and 51b. Between the support
portions 51a and 51b, a space 55 is defined by a part of each
support portion, an ultrasonic-wave vibrating plate 43, an
ultrasonic-wave transmission plate 54 in the form of a flat plate,
and a pair of side plates (not shown). An ultrasonic-wave vibrator
42 is fixed to the vibrating plate 43 by adhesive bonding. This
modification differs from the first modification in that the
transmission plate 54 is a flat plate that is fixed at an angle to
the vibrating plate 43. Ultrasonic vibration that is propagated to
the to-be-washed object 11 through vibrating plate 43, the coolant
in the space 55, and the transmission plate 54 from can be
reflected and returned by the object 11. Owing to the aforesaid
inclination, in this case, vibration from the vibrator 42 can
prevent the reflected ultrasonic vibration from being redirected by
the transmission plate 54 and damaging the vibrator 42 or the bond
between the vibrator 42 and the vibrating plate 43. In
consideration of the relation between the transmission of the
vibration from the vibrating plate 43 and the reflected vibration,
the mounting angle of the transmission plate 54 should be adjusted
to about 2 to 20.degree., and preferably to about 15.degree..
[0073] FIG. 11 shows a third modification of the ultrasonic-wave
application means. Like numerals are used to designate like
portions of the first to third modifications, and a description of
those portions is omitted. This modification differs from the
aforesaid modifications in that an ultrasonic-wave transmission
plate 64 is bent in a position substantially halfway between
support portions 61a and 61b. With this arrangement, damage from
the reflected vibration can be reduced in the same manner as in the
second modification, and the space between the to-be-washed surface
11a of the to-be-washed object 11 and the transmission plate 64,
which is to be filled with the detergent 13, can be widened. Thus,
the washing efficiency can be made higher than in the second
modification.
[0074] FIG. 12 shows a fourth modification of the ultrasonic-wave
application means. Like numerals are used to designate like
portions of the first to fourth modifications, and a description of
those portions is omitted. An ultrasonic-wave transmission plate 74
of this modification is different from the ultrasonic-wave
transmission plate 44 of the first modification. The transmission
plate 74 of the fourth modification is characterized in that its
surface opposite an ultrasonic-wave vibrating plate 43 is flat and
that its surface opposite the to-be-washed-object 11 is in the form
of a convex lens. With this arrangement, ultrasonic vibration given
from the transmission plate 74 can be diffused more uniformly, so
that energy on the to-be-washed surface 11a can be made uniform to
reduce the difference in washing capacity.
[0075] FIG. 13 shows a fifth modification of the ultrasonic-wave
application means. Like numerals are used to designate like
portions of the first to fifth modifications, and a description of
those portions is omitted. An ultrasonic-wave transmission plate 84
of this modification is different from the ultrasonic-wave
transmission plate 54 of the second modification. The transmission
plate 84 of the fifth modification is characterized in that its
surface opposite an ultrasonic-wave vibrating plate 43 is flat and
that its surface opposite the to-be-washed object 11 is in the form
of a convex lens. This arrangement can produce the following effect
besides the effect of the second modification. Ultrasonic vibration
given from the transmission plate 84 can be diffused more
uniformly, so that energy on the to-be-washed surface 11a can be
made uniform to reduce the difference in washing capacity.
[0076] FIGS. 14A and 14B show a sixth modification of the
ultrasonic-wave application means that can apply ultrasonic waves
in spots. FIG. 14A is a vertical sectional view, and FIG. 14B is a
sectional view taken along line Q-Q of f 14A. Ultrasonic-wave
application means 90 has a ring-shaped support portion 91. The
support portion 91 has therein ultrasonic-wave diffusion means 93,
one surface (lower surface in FIG. 14A) of which is convex
(spherical in this modification) and the other surface of which is
flat. The diffusion means 93 is formed of quartz, sapphire, SiC,
alumina, SUS, or Ta. An ultrasonic-wave vibrator 92 is fixed
substantially to the central portion of the other surface of the
diffusion means 93 by adhesive bonding. A thermal conduction sheet
96, e.g., a Teflon sheet, is provided on the outer per of the
vibrator 92. Ring-shaped cooling means 94, which has a coolant
passage 94a therein, is located on the sheet 96. The passage 94a is
provided with a coolant supply port 95a through which the coolant
is supplied and a coolant discharge port 95b through which the
coolant is discharged. With use of the application means 90
constructed in this manner, the diffusion means 93 can be cooled,
and the vibrator 92 can be cooled together with the adhesive agent
by means of the diffusion means 93. Further, the manufacture is
easy, and the maintenance and the replacement of the members can be
carried out smoothly and easily.
[0077] In the embodiment and the modifications described above, the
ultrasonic-wave application means has a straight configuration, as
shown in FIGS. 1 to 13, or is designed to be able to apply
ultrasonic waves in spots, as shown in FIGS. 14A and 14B. However,
these configurations may be combined freely and suitably used as
required with the same effect.
[0078] FIG. 15 is a side view showing an ultrasonic-wave washing
apparatus 110 according to a second embodiment of the invention.
FIG. 16 is a vertical sectional view showing an ultrasonic-wave
washing unit incorporated in the washing apparatus 110. FIG. 17 is
a plan view showing the relation between the washing unit of the
washing apparatus 110 and the to-be-washed object. In these
drawings, arrows X, Y and Z indicate three rectangular directions,
individually. More specifically, the arrows X and Y indicate
horizontal directions, and the arrow Z indicates a vertical
direction.
[0079] The ultrasonic-wave washing apparatus 110 comprises a
transportation mechanism 120, a positioning mechanism 130, and an
ultrasonic-wave washing unit 140. The transportation mechanism 120
transports a semiconductor substrate, such as a silicon wafer, or a
to-be-washed object W, such as a glass substrate for liquid crystal
display. The positioning mechanism 130 positions the washing unit
140. The washing unit 140 supplies a detergent L to the object W
and applies ultrasonic waves to the semiconductor, thereby washing
a to-be-washed surface Wa of the object W.
[0080] The transportation mechanism 120 comprises a plurality of
rotating drums 121 that are driven by means of a drive mechanism
(not shown). The drums 121 serve to transport the to-be-washed
object W in the direction of the arrow X.
[0081] The positioning mechanism 130 comprises an up-and-down
motion mechanism 131, an arm 132, and a control circuit 133. The
mechanism 131 positions the arm 132 with respect to its height
direction (direction of the arrow Z). The arm 132 is supported on
the mechanism 131, and the ultrasonic-wave washing unit 140 is
mounted on the distal end of the arm 132. The circuit 133 controls
the up-and-down motion mechanism 131 in accordance with the output
of a non-contact distance sensor 171, which will be mentioned
later.
[0082] The ultrasonic-wave washing unit 140 comprises a detergent
supply section 150, an ultrasonic-wave application section 160, and
a measuring section 170. The supply section 150 supplies the
detergent L to the to-be-washed surface Wa of the to-be-washed
object W. The application section 160 applies ultrasonic waves to
the detergent L on the surface Wa. The measuring section 170
measures a gap .delta. between an ultrasonic-wave diffuser 162 of
the application section 160 and the surface Wa.
[0083] As shown in FIG. 17, the detergent supply section 150
comprises a plurality of nozzles 151a to 151f, through which the
detergent L is supplied to the upper-stream side of the
to-be-washed object W that faces the ultrasonic-wave application
section 160. With this arrangement, ultrasonic waves can be
efficiently applied to the detergent L. Thus, the washing effect
can be improved, and the detergent L can be saved.
[0084] According to the present embodiment, moreover, the supply
section 150 is formed independently of the ultrasonic-wave
application section 160. Alternatively, however, it may be formed
integrally with the application section 160 or designed so that the
detergent L can be supplied along the surface of the
ultrasonic-wave diffuser 162 to the to-be-washed object W.
[0085] The ultrasonic-wave application section 160 has a support
portion 161 of Teflon. The length (in the depth direction of FIGS.
15 and 16) of the support portion 161 will be mentioned later. The
support portion 161 has therein an ultrasonic-wave diffuser 162,
one surface 162a of which is flat and the other surface 162b of
which is convex (spherical in this embodiment). The diffuser 162 is
formed of quartz, for example. Alternatively, it may be formed of
sapphire, SiC, alumina, SUS, or Ta. Since the diffuser 162 directly
touches the detergent L, its constituents may possibly liquate out
and pollute the to-be-washed object W, depending on the kind of the
detergent. Therefore, the material of the diffuser 162 must be
suitably selected according to the kind of the detergent L
used.
[0086] An ultrasonic-wave vibrator 163 is fixed substantially to
the central portion of the one surface of the ultrasonic-wave
diffuser 162. For example, an RF power source (not shown) is
connected to the ultrasonic-wave vibrator 163 by means of a supply
line 163a. Generation of ultrasonic vibration is controlled by
driving the RF power source.
[0087] A coolant passage 165 is formed over the ultrasonic-wave
diffuser 162. The passage 165 is provided with a coolant supply
port 166 through which the coolant is supplied and a coolant
discharge port 167 through which the coolant is discharged. The
number of coolant supply and discharge ports 166 and 167 is
suitably selected depending on the size of the ultrasonic-wave
washing unit 140. These ports 166 and 167 are connected to a source
of coolant supply and a coolant discharge section (not shown)
through the interior of the arm 132.
[0088] The measuring section 170 is provided with the non-contact
distance sensor 171. The output of the sensor 171 is applied to the
input of the control circuit 133 of the positioning mechanism 130.
Thereupon, the circuit 133 causes the up-and-down motion mechanism
131 to control the vertical position of the arm 132.
[0089] The following is a description of the length of the support
portion 161 in the direction of the arrow Y. As shown in FIG. 17,
the length of the support portion 161 is a little greater than the
width of the to-be-washed object (e.g., glass substrate for liquid
crystal display) W. As the object W passes once under the
ultrasonic-wave application section 160 in this arrangement, its
whole surface can be washed in the main.
[0090] However, the length of the support portion 161 may be
suitably changed depending on the size of the to-be-washed object
W. The support portion 161 may be reduced in size so that
ultrasonic vibration can be applied spottedly. A region G indicated
by broken line in FIG. 17 represents a portion in which the
ultrasonic-wave diffuser 162 and the object W connect with each
other by means of the detergent L.
[0091] The following is a description of the principle of washing
in the ultrasonic-wave washing apparatus 110. The to-be-washed
surface Wa of the to-be-washed object W and the ultrasonic-wave
diffuser 162 of the ultrasonic-wave application section 160 are
brought close to each other so that the gap .delta. between them is
about 2 to 3 mm, and the detergent L is supplied to the gap. If
this is done, the detergent L touches the diffuser 162 and uses its
surface tension to form a convex on the diffuser 162, as shown in
FIG. 16. On the other hand, vibration that is produced by the
ultrasonic-wave vibrator 163 reaches the diffuser 162. Ultrasonic
waves P having reached the diffuser 162 are radially diffused by
the curved convex of the diffuser 162 and applied to the detergent
L.
[0092] The following is a description of a washing method that
utilizes the ultrasonic-wave washing apparatus 110 constructed in
this manner. The arm 132 is lowered so that the ultrasonic-wave
washing unit 140 approaches the transportation mechanism 120 in
accordance with the thickness of the to-be-washed object W and the
given gap .delta.. Subsequently, the object W is transported by
means of the transportation mechanism 120. Thereupon, the given gap
.delta. is substantially maintained between the surface of the
object W and the apex of the ultrasonic-wave diffuser 162 of the
ultrasonic-wave application section 160. At the same time, the
non-contact distance sensor 171 measures the distance between the
surface of the object W and the diffuser 162 of the application
section 160. As the resulting value is applied to the input of the
positioning mechanism 130, the up-and-down motion mechanism 131 is
controlled so that the gap .delta. can always be kept within an
appropriate range.
[0093] Further, the detergent L is supplied to the to-be-washed
surface Wa of the to-be-washed object W through the nozzles 151a to
151f. When the detergent L is fed in a given quantity onto the
surface Wa, it fills the gap between the ultrasonic-wave diffuser
162 and the surface Wa and connects them in the region G, as shown
in FIG. 16. If the ultrasonic-wave vibrator 163 is actuated in this
state, ultrasonic vibration caused by the ultrasonic waves P is
transmitted to the surface Wa of the object W through the diffuser
162 and the detergent L. Thus, the vibration can remove particles
and the like that adhere to the surface Wa.
[0094] If the ultrasonic-wave washing is carried out in this manner
by using the ultrasonic-wave washing apparatus 110 according to the
present embodiment, the ultrasonic-wave diffuser 162 and the
to-be-washed surface Wa of the to-be-washed object W can be
prevented from touching each other even though the object W is
undulating or its thickness is uneven. Thus, the gap .delta. can be
narrowed to enhance the utility of the detergent.
[0095] FIG. 18 is a bottom view showing an ultrasonic-wave
application section 190 according to a modification of the
ultrasonic-wave application section 160 that can apply ultrasonic
waves in spots. The profile of the application section 190
resembles that of the application section 160 described above. Like
numerals are used to designate portions that have the same
functions, and a description of those portions is omitted. A
support portion 191 of the application section 190 is
ring-shaped.
[0096] This configuration can produce the same effect of the
ultrasonic-wave washing apparatus 110 that uses the ultrasonic-wave
application section 160.
[0097] The present invention is not limited to the embodiments
described above. According to the above-described embodiments, the
ultrasonic-wave application means has a straight configuration, as
shown in FIGS. 15 to 17, or is designed to be able to apply
ultrasonic waves in spots, as shown in FIG. 18. However, these
configurations may be combined freely and suitably used as required
with the same effect. Besides, it is to be understood that various
changes and modifications may be effected in the invention without
departing from the scope or spirit of the invention.
[0098] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *