U.S. patent application number 11/870211 was filed with the patent office on 2008-04-10 for substrate processing apparatus.
Invention is credited to Kenichiro ARAI, Koji HASEGAWA, Toshio HIROE, Tomomasa ISHIDA, Naoko KURUMOTO, Kazunari NADA, Soichi NADAHARA, Seiichiro OKUDA.
Application Number | 20080083501 11/870211 |
Document ID | / |
Family ID | 39274111 |
Filed Date | 2008-04-10 |
United States Patent
Application |
20080083501 |
Kind Code |
A1 |
ARAI; Kenichiro ; et
al. |
April 10, 2008 |
SUBSTRATE PROCESSING APPARATUS
Abstract
A substrate processing apparatus of the invention includes: a
substrate holding unit that holds a substrate almost in a
horizontal posture; a rotating unit that rotates the substrate held
by the substrate holding unit about a vertical shaft line; and an
etching liquid nozzle disposed oppositely to a bottom surface of
the substrate held by the substrate holding unit and having plural
discharge ports each having a different distance from a rotation
center of the substrate rotated by the rotating unit so as to
discharge an etching liquid toward the bottom surface of the
substrate rotated by the rotating unit from the plural discharge
ports.
Inventors: |
ARAI; Kenichiro; (Kyoto,
JP) ; HIROE; Toshio; (Kyoto, JP) ; NADAHARA;
Soichi; (Kyoto, JP) ; HASEGAWA; Koji; (Kyoto,
JP) ; OKUDA; Seiichiro; (Kyoto, JP) ; ISHIDA;
Tomomasa; (Kyoto, JP) ; KURUMOTO; Naoko;
(Kyoto, JP) ; NADA; Kazunari; (Kyoto, JP) |
Correspondence
Address: |
OSTROLENK FABER GERB & SOFFEN
1180 AVENUE OF THE AMERICAS
NEW YORK
NY
100368403
US
|
Family ID: |
39274111 |
Appl. No.: |
11/870211 |
Filed: |
October 10, 2007 |
Current U.S.
Class: |
156/345.21 |
Current CPC
Class: |
H01L 21/6708
20130101 |
Class at
Publication: |
156/345.21 |
International
Class: |
C23F 1/00 20060101
C23F001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 10, 2006 |
JP |
2006-276502 |
Feb 21, 2007 |
JP |
2007-041313 |
Claims
1. A substrate processing apparatus, comprising: a substrate
holding unit that holds a substrate almost in a horizontal posture:
a rotating unit that rotates the substrate held by the substrate
holding unit about a vertical shaft line; and an etching liquid
nozzle disposed oppositely to a bottom surface of the substrate
held by the substrate holding unit and having plural discharge
ports each having a different distance from a rotation center of
the substrate rotated by the rotating unit so as to discharge an
etching liquid toward the bottom surface of the substrate rotated
by the rotating unit from the plural discharge ports.
2. The substrate processing apparatus according to claim 1,
wherein: the plural discharge ports of the etching liquid nozzle
are provided in such a manner that discharge flow rates of the
etching liquid per unit area on the bottom surface of the substrate
that is being rotated by the rotating unit become equal almost
entirely across the bottom surface of the substrate.
3. The substrate processing apparatus according to claim 1,
wherein: the plural discharge ports of the etching liquid nozzle
are aligned along a rotation radius direction of the substrate
rotated by the rotating unit.
4. The substrate processing apparatus according to claim 1,
wherein: the plural discharge ports of the etching liquid nozzle
are disposed more densely with distance from the rotation center of
the substrate rotated by the rotating unit.
5. The substrate processing apparatus according to claim 1,
wherein: the plural discharge ports of the etching liquid nozzle
are aligned along a rotation radius direction at almost same
density so as to oppose a region from a center to a peripheral edge
of the substrate rotated by the rotating unit.
6. The substrate processing apparatus according to claim 1,
wherein: the plural discharge ports of the etching liquid nozzle
include plural peripheral discharge ports aligned along a rotation
radius direction almost at same density so as to oppose a region of
the substrate rotated by the rotating unit excluding a center
thereof.
7. The substrate processing apparatus according to claim 5,
wherein: the plural discharge ports include a discharge port for
peripheral edge to supply the etching liquid to a peripheral edge
of the substrate rotated by the rotating unit and plural inner
discharge ports disposed closer to the rotation center of the
substrate than the discharge port for peripheral edge; and the
discharge port for peripheral edge includes a larger diameter
discharge port having a larger diameter than the inner discharge
ports.
8. The substrate processing apparatus according to claim 5,
wherein: the plural discharge ports include a discharge port for
peripheral edge to supply the etching liquid to a peripheral edge
of the substrate rotated by the rotating unit; and the discharge
port for peripheral edge has an inclined discharge port that
discharges the etching liquid in a direction inclined outward in a
radius direction of the substrate with respect to a vertical
direction.
9. The substrate processing apparatus according to claim 6,
wherein: the plural discharge ports include a discharge port for
peripheral edge to supply the etching liquid to a peripheral edge
of the substrate rotated by the rotating unit and plural inner
discharge ports disposed closer to the rotation center of the
substrate than the discharge port for peripheral edge; and the
discharge port for peripheral edge includes a larger diameter
discharge port having a larger diameter than the inner discharge
ports.
10. The substrate processing apparatus according to claim 6,
wherein: the plural discharge ports include a discharge port for
peripheral edge to supply the etching liquid to a peripheral edge
of the substrate rotated by the rotating unit; and the discharge
port for peripheral edge has an inclined discharge port that
discharges the etching liquid in a direction inclined outward in a
radius direction of the substrate with respect to a vertical
direction.
11. The substrate processing apparatus according to claim 1,
further comprising: an etching liquid heating unit that heats the
etching liquid to be discharged from the plural discharge ports of
the etching liquid nozzle.
12. The substrate processing apparatus according to claim 1,
wherein: the substrate holding unit includes plural holding members
that hold the substrate almost in the horizontal posture in
cooperation by abutting on a peripheral edge of the substrate at
different positions.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a substrate processing
apparatus that etches away a surface of a substrate using an
etching liquid. Substrates subjected to etching include but not
limited to a semiconductor wafer, a glass substrate for liquid
crystal display, a glass substrate for plasma display, a substrate
for FED (Field Emission Display), an optical disc substrate, a
magnetic disc substrate, a magneto optical disc substrate, and a
photomask substrate.
[0003] 2. Description of Related Art
[0004] In the fabrication sequence of a semiconductor device,
liquid processing using a processing liquid is applied to a
semiconductor wafer. One of such liquid processing is etching
processing in which an etching liquid is supplied to a surface of
the semiconductor wafer. The etching processing referred to herein
includes, besides etching processing to form a pattern on a surface
of a semiconductor wafer (the semiconductor wafer itself or a thin
film formed on the semiconductor wafer), rinse processing to remove
foreign matter on a surface of the semiconductor wafer by utilizing
an etching action.
[0005] A substrate processing apparatus that processes a
semiconductor wafer using a processing liquid includes a batch type
configured to apply processing to plural semiconductor wafers
collectively at a time and a single substrate process type
configured to apply processing to semiconductor wafers one by one.
The single substrate process type substrate processing apparatus
has a spin chuck that rotates while holding a semiconductor wafer
almost in a horizontal posture, and a processing liquid nozzle that
supplies a processing liquid toward a surface of the semiconductor
wafer held by the spin chuck.
[0006] In a case where the processing liquid is supplied to the
bottom surface of the semiconductor wafer held by the spin chuck, a
center shaft nozzle inserted through the rotation shaft of the spin
chuck is used. A discharge port at an upper end of the center shaft
nozzle opposes the center of the bottom surface of the
semiconductor wafer held by the spin chuck. When the processing
liquid discharged from the discharge port reaches the bottom
surface of the semiconductor wafer, the processing liquid spreads
toward the outer side along the rotation radius direction under a
centrifugal force. The processing liquid is thus supplied across
the entire bottom surface of the semiconductor wafer.
[0007] For example, in a case where the etching processing is to be
applied to a semiconductor wafer on the device forming surface, the
semiconductor wafer is held by the spin chuck with the device
forming surface faced down. The semiconductor wafer is rotated
about a vertical shaft line by the spin chuck and the etching
liquid is discharged from the center shaft nozzle toward the
rotation center of the device forming surface. The etching liquid
having reached the device forming surface of the semiconductor
wafer migrates toward the outer side along the rotation radius
direction under a centrifugal force induced by rotations of the
semiconductor wafer, and is consequently supplied across the entire
surface of the device forming surface of the semiconductor wafer
(see, for example, Japanese Unexamined Patent Publication No.
2002-110626 and United States Patent Application Publication No.
US2003/0194878A1).
[0008] The etching liquid supplied to the semiconductor wafer,
however, spreads radially about a region where it was supplied, and
because the spreading direction of the etching liquid supplied to
the rotation center of the semiconductor wafer coincides with the
acting direction of the centrifugal force, the etching liquid
hardly drops off while it migrates toward the peripheral edge of
the semiconductor wafer. Accordingly, a large amount of the etching
liquid reaches the peripheral edge of the semiconductor wafer. In
this case, the etching liquid may possibly flow over from the
peripheral edge of the semiconductor wafer onto the surface (top
surface) on the opposite side and undesirably etch away the surface
on the opposite side.
[0009] In particular, in a case where a mechanical chuck that holds
a semiconductor wafer by pinching the peripheral edge of the
semiconductor wafer using plural pinching members is used as the
spin chuck, because the etching liquid flows over onto the surface
on the opposite side by running along plural pinching members,
etching proceeds particularly in portions abutted on the pinching
members, which raises a problem that plural traces of etching
(so-called pin marks) are left along the peripheral edge of the
semiconductor wafer.
SUMMARY OF THE INVENTION
[0010] An object of the invention is therefore to provide a
substrate processing apparatus not only capable of applying etching
processing across the entire bottom surface of the substrate, but
also capable of suppressing or preventing an etching liquid
supplied to the bottom surface of the substrate from flowing over
onto the top surface.
[0011] A substrate processing apparatus of the invention includes:
a substrate holding unit that holds a substrate almost in a
horizontal posture; a rotating unit that rotates the substrate held
by the substrate holding unit about a vertical shaft line; and an
etching liquid nozzle disposed oppositely to a bottom surface of
the substrate held by the substrate holding unit and having plural
discharge ports each having a different distance from a rotation
center of the substrate rotated by the rotating unit so as to
discharge an etching liquid toward the bottom surface of the
substrate rotated by the rotating unit from the plural discharge
ports.
[0012] According to this configuration, the etching liquid
discharged from the plural discharge ports in a distributed manner
is supplied directly to the bottom surface of the substrate in
plural regions each having a different distance from the rotation
center thereof. The etching liquid supplied to the plural supplied
regions on the bottom surface of the substrate spreads radially
about the respective supplied regions. The etching liquid spreading
toward the rotation center drops off by a centrifugal force induced
by rotations of the substrate, whereas the etching liquid spreading
toward the peripheral edge drops off as the etching liquid under
consideration interferes with the etching liquid supplied to
regions closer to the peripheral edge of the substrate than the
supplied region of the etching liquid under consideration. An
amount of the etching liquid reaching the peripheral edge of the
substrate is therefore relatively small. Hence, not only is it
possible to apply the etching processing across the entire bottom
surface of the substrate, but it is also possible to suppress or
prevent the etching liquid from flowing over onto the top surface
of the substrate.
[0013] It is preferable that the plural discharge ports of the
etching liquid nozzle are provided in such a manner that discharge
flow rates of the etching liquid per unit area on the bottom
surface of the substrate that is being rotated by the rotating unit
become equal almost entirely across the bottom surface of the
substrate.
[0014] According to this configuration, the discharge flow rates of
the etching liquid per unit area on the bottom surface of the
substrate are equal almost entirely across the bottom surface of
the substrate. It is thus possible to supply a fresh etching liquid
directly and uniformly almost across the entire bottom surface of
the substrate.
[0015] In a case where an etching liquid having extremely high
etching power when it is fresh but deteriorating so fast that it
loses etching power almost completely in an instant is used, when
the etching liquid is supplied to the substrate, the etching rate
is quite high in the supplied regions, whereas the etching rate is
low in the other regions. However, even when such an etching liquid
is used, because a fresh etching liquid is supplied directly and
uniformly almost across the substrate, it is possible to etch away
the entire bottom surface of the substrate uniformly at an
extremely high etching rate. As the etching liquid supplied from
the etching liquid nozzle, for example, hydrofluoric-nitric acid
can be used.
[0016] It is preferable that the plural discharge ports of the
etching liquid nozzle are aligned along a rotation radius direction
of the substrate rotated by the rotating unit.
[0017] According to this configuration, it is possible to supply a
fresh etching liquid directly almost across the entire bottom
surface of the substrate that is rotating.
[0018] Also, it is preferable that the plural discharge ports of
the etching liquid nozzle are disposed more densely with distance
from the rotation center of the substrate rotated by the rotating
unit.
[0019] According to this configuration, discharge flow rates of the
etching liquid discharged toward the substrate from the etching
liquid nozzle increases with distance from the rotation center of
the substrate. Meanwhile, the positions on the bottom surface of
the substrate at which the etching liquid is supplied move at a
higher speed with distance from the rotation center. Consequently,
a fresh etching liquid discharged from the plural discharge ports
is supplied directly to the bottom surface of the substrate in such
a manner that discharge flow rates of the etching liquid per unit
area become equal.
[0020] It may be configured in such a manner that the plural
discharge ports of the etching liquid nozzle are aligned along a
rotation radius direction at almost same density so as to oppose a
region from a center to a peripheral edge of the substrate rotated
by the rotating unit.
[0021] The center of the substrate referred to herein means a
region in close proximity to the rotation center of the
substrate.
[0022] According to this configuration, because the etching liquid
is supplied to the substrate from the plural discharge ports
aligned at almost the same density, discharge flow rates of the
etching liquid discharged to the bottom surface of the substrate
from the etching liquid nozzle are almost equal from the center to
the peripheral edge of the substrate. The etching liquid discharged
from the respective discharge ports therefore interferes with one
another to a moderate degree, which further reduces an amount of
the etching liquid reaching the peripheral edge of the substrate.
It is thus possible to further suppress the etching liquid from
flowing over onto the top surface of the substrate.
[0023] Also, it is preferable that the plural discharge ports of
the etching liquid nozzle include plural peripheral discharge ports
aligned along a rotation radius direction almost at same density so
as to oppose a region of the substrate rotated by the rotating unit
excluding a center thereof.
[0024] According to this configuration, because the etching liquid
is supplied to the substrate from the plural peripheral discharge
ports aligned along the rotation radius direction at almost the
same density, discharge flow rates of the etching liquid discharged
to the bottom surface of the substrate from the etching liquid
nozzle are almost equal except for the center of the substrate. The
etching liquid discharged from the respective discharge ports
therefore interferes with one another to a moderate degree. An
amount of the etching liquid reaching the peripheral edge of the
substrate is thus reduced further. Consequently, it is possible to
further suppress the etching liquid from flowing over onto the top
surface of the substrate.
[0025] Further, by omitting the discharge port in a region opposing
the center of the bottom surface of the substrate or by disposing
the discharge ports in this region less densely than the peripheral
discharge ports, discharge flow rates of the etching liquid become
lower at the center of the bottom surface of the substrate than in
the other regions. It is thus possible to suppress an increase of
the etching rate at the center of the substrate where the
respective positions on the bottom surface of the substrate move at
a relatively slow speed. Consequently, it is possible to apply the
etching processing uniformly across the entire bottom surface of
the substrate.
[0026] In a case where the discharge port opposing the center of
the bottom surface of the substrate is provided to the etching
liquid nozzle, it is preferable to provide the discharge port at a
position displaced from the position opposing the rotation center
of the bottom surface of the substrate in the rotation radius
direction of the substrate. In this case, because the etching
liquid is not supplied directly to the rotation center of the
bottom surface of the substrate, it is possible to suppress an
abrupt increase of the etching rate at the rotation center of the
substrate. In addition, in this case, it is more preferable to
dispose the discharge port at a position at which it is possible to
supply the etching liquid to the rotation center of the bottom
surface of the substrate as the etching liquid spreads when the
etching liquid reaches the bottom surface of the substrate.
[0027] It is preferable that the plural discharge ports include a
discharge port for peripheral edge to supply the etching liquid to
a peripheral edge of the substrate rotated by the rotating unit and
plural inner discharge ports disposed closer to the rotation center
of the substrate than the discharge port for peripheral edge, and
that the discharge port for peripheral edge includes a larger
diameter discharge port having a larger diameter than the inner
discharge ports.
[0028] According to this configuration, a discharge flow rate of
the etching liquid of the discharge port for peripheral edge is
higher than the discharge flow rates of the inner discharge ports.
Hence, discharge flow rates of the etching liquid become higher in
the peripheral edge of the bottom surface of the substrate than in
the inner regions thereof. It is thus possible to suppress a
decrease of the etching rate in the peripheral edge of the
substrate where the respective positions on the bottom surface of
the substrate move relatively at a high speed. Consequently, it is
possible to apply the etching processing uniformly across the
entire bottom surface of the substrate.
[0029] Also, it is preferable that the plural discharge ports
include a discharge port for peripheral edge to supply the etching
liquid to a peripheral edge of the substrate rotated by the
rotating unit, and that the discharge port for peripheral edge has
an inclined discharge port that discharges the etching liquid in a
direction inclined outward in a radius direction of the substrate
with respect to a vertical direction.
[0030] According to this configuration, the etching liquid is
discharged in a direction inclined outward in the radius direction
of the substrate with respect to the vertical direction. Hence,
even in a case where the tip end of the etching liquid nozzle is
located at the position inner than the peripheral edge of the
substrate, it is possible to supply the etching liquid directly to
the peripheral edge of the substrate.
[0031] The substrate processing apparatus may be configured to
further include an etching liquid heating unit that heats the
etching liquid to be discharged from the plural discharge ports of
the etching liquid nozzle.
[0032] According to this configuration, a heated etching liquid is
discharged from the plural discharge ports of the etching liquid
nozzle. The heated etching liquid has high etching power. It is
therefore possible to etch away the bottom surface of the substrate
at a high etching rate.
[0033] The substrate holding unit may include plural holding
members that hold the substrate almost in the horizontal posture in
cooperation by abutting on a peripheral edge of the substrate at
different positions.
[0034] According to this configuration, because an amount of the
etching liquid reaching the peripheral edge of the substrate is
relatively small, even in a case where plural holding members are
used to hold the substrate, the etching liquid hardly flows over
onto the top surface of the substrate by running along the holding
members. It is thus possible to hold the substrate appropriately
without leaving plural traces of etching along the peripheral edge
on the top surface of the substrate.
[0035] The above and other objects, features, and advantages of the
invention will become more apparent from the following description
of embodiments with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1 is a cross section schematically showing the
configuration of a substrate processing apparatus according to a
first embodiment of the invention;
[0037] FIG. 2 is a plan view of a spin chuck in the substrate
processing apparatus shown in FIG. 1;
[0038] FIG. 3 is a plan view of an etching liquid nozzle in a
substrate processing apparatus according to a second embodiment of
the invention;
[0039] FIG. 4 is a longitudinal cross section showing the
configuration of a major portion of the etching liquid nozzle of
FIG. 3;
[0040] FIG. 5 is a graph showing an in-plane distribution of
etching amounts in etching tests;
[0041] FIG. 6 is a view showing flown over amounts of the etching
liquid in the etching tests;
[0042] FIG. 7 is a plan view of a spin chuck in a substrate
processing apparatus according to a third embodiment of the
invention;
[0043] FIG. 8 is a plan view showing a spin chuck in a substrate
processing apparatus according to a fourth embodiment of the
invention;
[0044] FIG. 9 is a plan view of the spin chuck in the substrate
processing apparatus shown in FIG. 8; and
[0045] FIG. 10 is a plan view of a spin chuck in a substrate
processing apparatus according to a fifth embodiment of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0046] FIG. 1 is a cross section schematically showing the
configuration of a substrate processing apparatus 300 according to
one embodiment (first embodiment) of the invention.
[0047] The substrate processing apparatus 300 is a single substrate
process type apparatus that applies etching processing for removing
an oxide film to the surface (bottom surface) 9 on the device
forming region side of a disc-shaped semiconductor wafer
(hereinafter, referred to simply as the wafer) W formed of, for
example, an oxide film silicon wafer. In this embodiment, for
example, hydrofluoric acid is used as an etching liquid.
[0048] The substrate processing apparatus 300 includes a spin chuck
301 as a substrate holding unit that rotates about a vertical shaft
line (rotation shaft line) 1a passing almost the center of the
wafer W while holding the wafer W almost in a horizontal
posture.
[0049] FIG. 2 is a plan view schematically showing the
configuration of the spin chuck 301 of the substrate processing
apparatus 300 shown in FIG. 1.
[0050] Referring to FIG. 1 and FIG. 2, the spin chuck 301 has a
disc-like spin base 302. Plural (six in this embodiment) pinching
members 303 are disposed at almost equiangular intervals along the
peripheral edge on the top surface of the spin base 302. The wafer
W is held almost in a horizontal posture as the plural pinching
members 303 pinch the peripheral edge of the wafer W. While holding
the wafer W, each pinching member 303 abuts on the end face of the
wafer W and the peripheral edge on the bottom surface 9 of the
wafer W.
[0051] The spin base 302 is configured to rotate by being coupled
to the top end of a rotation shaft 305 that is rotated by a chuck
rotary driving mechanism 304 including a motor. The rotation shaft
305 is a hollow shaft, inside of which an insertion tube 306 is
inserted through. The insertion tube 306 is held inside the
rotation shaft 305 in a non-rotating state.
[0052] An etching liquid nozzle 307 in the shape of a straight line
when viewed in a plane is disposed on the spin base 302. The
etching liquid nozzle 307 is a long nozzle extending along the
rotation radius direction of the wafer W by passing through the
rotation center C of the wafer W. In order to prevent interference
of the etching liquid nozzle 307 with the pinching members 303
during rotations of the spin base 302, the both ends of the etching
liquid nozzle 307 are stopped at positions slightly inner than the
peripheral edge of the spin base 302. The both ends of the etching
liquid nozzle 307 are therefore located on the inner side than the
end face of the wafer W held by the spin chuck 301.
[0053] The etching liquid nozzle 307 is made hollow inside and
linked to the insertion tube 306 at the center position of the
bottom thereof. The etching liquid nozzle 307 therefore remains
stationary and will never rotate in association with rotations of
the spin base 302.
[0054] A rotation shaft discharge port 311 disposed on the rotation
shaft axis (vertical shaft line) 1a of the wafer W and a pair of
peripheral discharge port groups 310 disposed with the rotation
shaft discharge port 311 in between are provided to the top surface
of the etching liquid nozzle 307. Each peripheral discharge port
group 310 includes plural peripheral discharge ports 312 each
having a different distance from the rotation center C of the wafer
W. The plural peripheral discharge ports 312 are aligned along the
shape of the etching liquid nozzle 307 (along the rotation radius
direction of the wafer W). The plural peripheral discharge ports
312 are disposed at regular intervals (at the same density, that
is, isopycnic) in a region opposing a region of the wafer W
excluding the rotation center C thereof. The etching liquid is
discharged upward (vertical direction) from the respective
discharge ports 311 and 312.
[0055] In this embodiment, an interval between each peripheral
discharge port 312 adjacent to the rotation shaft discharge port
311 and the rotation shaft discharge port 311 is set to a length
equal to an interval between one peripheral discharge port 312 and
another peripheral discharge port 312. In other words, the
discharge ports 311 and 312 are disposed at regular intervals (at
the same density) from one end to the other end of the etching
liquid nozzle 307.
[0056] In Example 1 described below in which an experiment for
trial production was conducted by the inventor of the present
application, the length of the etching liquid nozzle 307 was set to
272 mm, the diameter of the discharge ports 311 and 312 was set to
0.5 mm, and the interval among the respective discharge ports 311
and 312 was set to 5 mm.
[0057] In addition, a supply channel 313 extending linearly along
the shape of the etching liquid nozzle 307 and communicating with
the respective discharge ports 311 and 312 is formed inside the
etching liquid nozzle 307.
[0058] A circulation channel 314 is formed inside the insertion
tube 306 along the rotation shaft line 1a. The circulation channel
314 communicates with the supply channel 313. A collecting supply
tube 30 is connected to the circulation channel 314. An etching
liquid supply tube 27, to which the etching liquid is supplied from
an etching liquid supply source, is connected to the collecting
supply tube 30. An etching liquid valve 315 and a heater 28 to heat
the etching liquid circulating through the etching supply tube 27
are interposed in midstream of the etching liquid supply tube 27
sequentially in this order from the etching liquid supply source
side. When the etching liquid valve 315 is opened, the etching
liquid circulates through the etching liquid supply tube 27, and
the etching liquid heated to 40 to 80.degree. C. by the heater 28
while being circulated is supplied to the circulation channel 314.
In addition, a deionized water supply tube 29, to which deionized
water is supplied from a deionized water supply source, is
connected to the collecting supply tube 30. A deionized water valve
316 is interposed in midstream of the deionized water supply tube
29 for deionized water to be supplied to the circulation channel
314.
[0059] According to the configuration as above, by closing the
deionized water valve 316 and opening the etching liquid valve 315,
it is possible to supply the etching liquid heated to 40 to
80.degree. C. to the rotation shaft discharge port 311 and the
peripheral discharge ports 312 of the etching liquid nozzle 307 via
the circulation channel 314 and the supply channel 313. Conversely,
by closing the etching liquid valve 315 and opening the deionized
water valve 316, it is possible to supply deionized water to the
rotation shaft discharge port 311 and the peripheral discharge
ports 312 of the etching liquid nozzle 307 via the circulation
channel 314 and the supply channel 313.
[0060] A gas supply channel 317 is defined between the inner wall
surface of the rotation shaft 305 formed of a hollow shaft and the
outer wall surface of the insertion tube 306. The gas supply tube
317 opens to the top surface of the spin base 302. It is configured
in such a manner that a nitrogen gas as an inert gas is supplied to
the gas supply channel 317 via a nitrogen gas valve 318.
[0061] A disc-shaped shield plate 320 having substantially the same
diameter as the wafer W is provided above the spin chuck 301. The
shield plate 320 has an opening 319 at the center thereof. A
rotation shaft 321 extending along a shaft line common with the
rotation shaft line 1a of the spin chuck 301 is fixed to the top
surface of the shield plate 320. The rotation shaft 321 is made
hollow, inside of which is formed a gas supply channel 323 that
communicates with the opening 319 in the shield plate 320 and
thereby supplies a nitrogen gas toward the center of the wafer W.
It is configured in such a manner that a nitrogen gas is supplied
to the gas supply channel 323 via a nitrogen gas valve 324.
[0062] The rotation shaft 321 is provided with a shield plate
elevation driving mechanism 325 to move the shield plate 320 up and
down between a proximity position at which the shield plate 320
comes in close proximity to the top surface of the wafer W held by
the spin chuck 301 and an evacuation position at which the shield
plate 320 evacuates far above the spin chuck 301, and a shield
plate rotary driving mechanism 326 to rotate the shield plate 320
almost in sync with rotations of the wafer W by the spin chuck
301.
[0063] Hereinafter, etching processing applied to the bottom
surface 9 of the wafer W in the substrate processing apparatus 300
will be described.
[0064] Before the wafer W subjected to processing is carried into
the substrate processing apparatus 300, the shield plate 320 is
located at the evacuation position at which it evacuates far above
the spin chuck 301 so as not to interrupt a carry-in operation.
[0065] In order to process the wafer W, the wafer W is first
carried into the substrate processing apparatus 300 by an
unillustrated delivery robot, and the wafer W is held by the spin
base 302 of the spin chuck 301 with the surface on the device
forming region side faced down. When the wafer W is held by the
spin base 302, the chuck rotary driving mechanism 304 is controlled
for the spin base 302 to start to rotate the wafer W, and the
rotating speed of the wafer W is increased, for example, to 1000
rpm. In this instance, the etching liquid nozzle 307 remains
stationary as has been described above and will never rotate in
association with rotations of the spin base 302. Also, the shield
plate elevation driving mechanism 325 is controlled for the shield
plate 320 to move down to the proximity position at which it comes
in close proximity to the top surface of the wafer W held by the
spin base 302. The shield plate rotary driving mechanism 326 is
then controlled for the shield plate 320 to keep rotating in the
same direction as the wafer W, while the nitrogen gas valve 324 is
opened for a nitrogen gas to be supplied from the opening 319 in
the shield plate 320 to a space between the wafer W and the shield
plate 320. Accordingly, a current of nitrogen gas flowing outward
in the radial direction from the center of the shield plate 320 is
produced in the space between the wafer W and the shield plate
320.
[0066] When the rotating speed of the wafer W reaches, for example,
1000 rpm, the etching liquid valve 315 is opened, and the etching
liquid heated to 40 to 80.degree. C. is discharged from the
rotation shaft discharge port 311 and the respective peripheral
discharge ports 312 of the etching liquid nozzle 307 toward the
bottom surface 9 of the wafer W that is rotating. The nitrogen gas
valve 318 is also opened and a nitrogen gas is supplied to a space
surrounded by the spin base 302 and the bottom surface 9 of the
wafer W.
[0067] The etching liquid discharged from the rotation shaft
discharge port 311 is supplied directly to the rotation center C of
the bottom surface 9 of the wafer W. The etching liquid discharged
from the respective peripheral discharge ports 312 is supplied
directly to the bottom surface 9 of the wafer W opposing the
respective peripheral discharge ports 312. Because the discharge
ports 311 and 312 are disposed at regular intervals, discharge flow
rates of the etching liquid discharged directly to the bottom
surface 9 of the wafer W are almost equal from the center (a region
in close proximity to the rotation center C) to the peripheral edge
of the wafer W.
[0068] The etching liquid discharged from the respective discharge
ports 311 and 312 are relatively hot at 40 to 80.degree. C. in
comparison with normal temperature. Etching power of the etching
liquid is therefore high. Because the etching liquid having high
etching power is supplied directly across the entire bottom surface
9 of the wafer W, almost the entire bottom surface 9 of the wafer W
is etched away at a high etching rate.
[0069] The etching liquid supplied to the bottom surface 9 of the
wafer W from the respective discharge ports 311 and 312 spreads
radially about the corresponding supplied regions, and then
migrates over the bottom surface 9 toward the peripheral edge of
the wafer W as it experiences a centrifugal force induced by
rotations of the wafer W to be wasted to the outside of the wafer W
from the peripheral edge.
[0070] The etching liquid supplied to the respective supplied
regions and then spreading toward the rotation center C falls down
because of a centrifugal force induced by rotations of the wafer W,
whereas the etching liquid spreading toward the peripheral edge of
the wafer W falls down as the etching liquid under consideration
interferes with the etching liquid supplied to regions closer to
the peripheral edge than the supplied region of the etching liquid
under consideration. In particular, because discharge flow rates of
the etching liquid discharged directly to the bottom surface 9 of
the wafer W are almost equal from the center to the peripheral edge
of the wafer W, etching liquid discharged from the respective
peripheral discharge ports 312 interferes with one another to a
moderate degree. Hence, in comparison with an amount of the etching
liquid supplied to the bottom surface 9 of the wafer W, an amount
of the etching liquid reaching the peripheral edge of the wafer W
is small.
[0071] Also, a current of nitrogen gas flowing outward in the
radial direction from the center of the shield plate 320 is
produced in the space between the wafer W (top surface) and the
shield plate 320. It is therefore difficult for the etching liquid
flowing toward the peripheral edge of the wafer W to flow over onto
the top surface of the wafer W. It is thus possible to further
suppress or prevent the etching liquid from flowing over onto the
top surface of the wafer W.
[0072] When a predetermined time (for example, one minute) has
elapsed since the supply of the etching liquid started, the etching
liquid valve 315 is closed. The deionized water valve 316 is then
opened for deionized water to be supplied across the entire bottom
surface 9 of the wafer W from the rotation shaft discharge port 311
and the peripheral discharge ports 312. The rotating speed of the
wafer W is reduced, for example, from 1000 rpm to 500 rpm. In this
instance, deionized water discharged from the rotation shaft
discharge port 311 is supplied directly to the rotation center C of
the bottom surface 9 of the wafer W. Deionized water discharged
from the respective peripheral discharge ports 312 is supplied
directly to regions on the bottom surface 9 of the wafer W opposing
the respective peripheral discharge ports 312.
[0073] Deionized water supplied to the bottom surface 9 of the
wafer W flows toward the peripheral edge of the wafer W owing to a
centrifugal force induced by rotations of the wafer W. Deionized
water is then wasted to the outside from the peripheral edge of the
wafer W. The etching liquid adhering onto the bottom surface 9 of
the wafer W is thus rinsed away by deionized water.
[0074] A current of nitrogen gas flowing outward in the rotation
radial direction of the wafer W from the center of the shield plate
320 is produced in the space between the wafer W (top surface) and
the shield plate 320. It is thus possible to suppress or prevent a
mixed liquid of deionized water and the etching liquid from flowing
over onto the top surface of the wafer W.
[0075] When a predetermined time (for example, 30 seconds) has
elapsed since the supply of deionized water started, the deionized
water valve 316 is closed to stop the supply of deionized water to
the bottom surface 9 of the wafer W. In addition, the nitrogen gas
valve 324 is closed and the shield plate elevation driving
mechanism 325 is controlled for the shield plate 320 to move up to
the evacuation position at which it evacuates far above the spin
chuck 301.
[0076] The rotating speed of the wafer W is then increased from 500
rpm to 2500 rpm to apply spin dry processing in which the wafer W
is dried by throwing off deionized water adhering onto the surface
thereof using a centrifugal force after the water rinse processing.
When the spin dry processing is applied over, for example, 120
seconds, the wafer W is stopped rotating, and the wafer W having
undergone the etching processing is carried out from the spin chuck
301.
[0077] As has been described, according to this embodiment, an
amount of the etching liquid reaching the peripheral edge of the
wafer W is relatively small. Hence, not only is it possible to
apply the etching processing across the entire bottom surface 9 of
the wafer W, but it is also possible to suppress or prevent the
etching liquid from flowing over onto the top surface of the wafer
W.
[0078] Also, because the discharge ports 311 and 312 are disposed
at regular intervals, discharge flow rates of the etching liquid
discharged directly to the bottom surface 9 of the wafer W from the
etching liquid nozzle 307 become almost equal from the center to
the peripheral edge of the wafer W. The etching liquid discharged
from the respective peripheral discharge ports 312 thus interferes
with one another to a moderate degree. Accordingly, an amount of
the etching liquid reaching the peripheral edge of the wafer W is
further reduced. It is thus possible to further suppress the
etching liquid from flowing over onto the top surface of the wafer
W.
[0079] Further, because an amount of the etching liquid reaching
the peripheral edge of the wafer W is relatively small, the etching
liquid hardly flows over onto the top surface by running along the
plural pinching members 303. It is thus possible to suppress or
prevent plural traces of etching (so-called pin marks) from being
left along the peripheral edge on the top surface of the wafer
W.
[0080] FIG. 3 is a plan view of an etching liquid nozzle 407 of a
substrate processing apparatus 400 according to another embodiment
(second embodiment) of the invention. FIG. 4 is a longitudinal
cross section showing the configuration of a major portion of the
etching liquid nozzle 407. In the second embodiment, portions
corresponding to the respective portions described in the
embodiment with reference to FIG. 2 (first embodiment) are labeled
with the same reference numerals as those in FIG. 2, and
descriptions of these portions are omitted.
[0081] As with the etching liquid nozzle 307 of the first
embodiment, the etching liquid nozzle 407 of the second embodiment
is a long nozzle extending along the rotation radius direction of
the wafer W to positions slightly inner than the peripheral edge of
the spin base 302 (the positions inner than the end face of the
wafer W) by passing through the rotation center C. The etching
liquid nozzle 407 is different from the etching liquid nozzle 307
in that a discharge port (rotation shaft discharge port) opposing
the rotation center C of the bottom surface 9 of the wafer W is
omitted. Larger diameter discharge ports 413 having a larger
diameter than the other discharge ports 411 and 412 are disposed at
the both ends of the etching liquid nozzle 407. In this point, too,
the etching liquid nozzle 407 is different from the etching liquid
nozzle 307 of the first embodiment.
[0082] A center discharge port 411 disposed at the center of the
etching liquid nozzle 407 (a region opposing the center of the
wafer W (a region in close proximity to the rotation center C)) and
a pair of peripheral discharge port groups 410 disposed with the
center in between are provided to the top surface of the etching
liquid nozzle 407. Each peripheral discharge port group 410
includes plural peripheral discharge ports 412 and 413 aligned
along the shape of the etching liquid nozzle 407 (along the
rotation radius direction of the wafer W) on the top surface of the
etching liquid nozzle 407.
[0083] In this embodiment, the discharge ports 411, 412, and 413 on
one side of the etching liquid nozzle 407 (on the right of the
etching liquid nozzle 407 in FIG. 3) and those on the other side
(on the left of the etching liquid nozzle 407 shown in FIG. 3) are
disposed at asymmetric positions. In particular, the center
discharge port 411 is disposed at an asymmetric position.
[0084] The center discharge port 411 is disposed at a specific
interval from the rotation shaft line 1a of the wafer W. The center
discharge port 411 is provided to only one side of the etching
liquid nozzle 407, and it is not provided to the other side of the
etching liquid nozzle 407. Accordingly, in comparison with other
regions of the etching liquid nozzle 407, the discharge ports 411,
412, and 413 are disposed less densely at the center of the etching
liquid nozzle 407.
[0085] The center discharge port 411 is disposed at a position at
which it is possible to supply the etching liquid to the rotation
center C of the wafer W owing to spreading of the etching liquid
when the etching liquid reaches the bottom surface 9 of the wafer
W.
[0086] The peripheral discharge ports 412 and 413 are disposed at
regular intervals (at the same density) in a region opposing a
region of the bottom surface 9 of the wafer W excluding the center
thereof (a region between the center and the peripheral edge and
the peripheral edge).
[0087] The peripheral discharge ports 412 and 413 disposed at the
both ends of the etching liquid nozzle 407 are to discharge the
etching liquid to the peripheral edge of the wafer W. The
peripheral discharge ports 412 and 413 disposed at the both ends of
the etching liquid nozzle 407 include plural (two on the right end
and three on the left end of the etching liquid nozzle 407 in FIG.
3) larger diameter discharge ports 413 having a larger diameter
than the other peripheral discharge ports 412. Referring to FIG. 4,
the diameter W2 of the larger diameter discharge ports 413 is set
to a size about 1.8 times larger than the diameter W1 of the
peripheral discharge ports 412. A discharge flow rate of the
etching liquid of the larger diameter discharge ports 413 is thus
about 3.2 times higher than a discharge flow rate of the etching
liquid of the peripheral discharge ports 412.
[0088] The etching liquid nozzle 407 is configured in such a manner
that the etching liquid is discharged upward (vertical direction)
from the center discharge port 411 and the peripheral discharge
ports 412.
[0089] On the contrary, a discharge direction of the larger
diameter discharge ports 413 is inclined outward in the rotation
radius direction of the wafer W at 45 to 60.degree. with respect to
the vertical direction. It is thus possible to supply the etching
liquid directly to the peripheral edge of the wafer W positioned on
the outside of the both ends of the etching liquid nozzle 407 in
the rotation direction of the wafer W.
[0090] In Example 2 described below in which an experiment for
trial production was conducted by the inventor of the present
application, the center discharge port 411 was provided at a
position 5 mm away from the rotation center. Further, two discharge
ports, that is, the outermost and second outermost discharge ports,
at the end on one side (on the right in FIG. 3) of the etching
liquid nozzle 407 were provided as the larger diameter discharge
ports 413, and three discharge ports, that is, the outermost and
following two discharge ports, at the end on the other side (on the
left in FIG. 3) were provided as the larger diameter discharge
ports 413. In addition, in Example 2, the length of the etching
liquid nozzle 407 was set to 272 mm, the diameter of the discharge
ports 411 and 412 was set to 0.5 mm, the intervals among the
discharge ports 411 and 412 were set to 5 mm, and the discharge
direction of the larger diameter discharge ports 413 was inclined
at 30.degree. with respect to the vertical direction.
[0091] During the etching processing, the etching liquid discharged
from the center discharge port 411 is supplied directly to the
center of the wafer W. The etching liquid discharged from the
peripheral discharge ports 412 and 413 is supplied directly to the
regions of the wafer W excluding the center thereof. Because the
peripheral discharge ports 412 and 413 are disposed at regular
intervals, discharge flow rates of the etching liquid discharged
directly to the bottom surface 9 of the wafer W are almost equal
except for the center of the wafer W.
[0092] In the second embodiment, because the discharge flow rates
of the etching liquid discharged directly to the bottom surface 9
of the wafer W are almost equal except for the center of the wafer
W, the etching liquid discharged from the respective peripheral
discharge ports 412 and 413 interferes with one another to a
moderate degree. Accordingly, an amount of the etching liquid
reaching the peripheral edge of the wafer W is reduced. It is thus
possible to suppress the etching liquid from flowing over onto the
top surface of the wafer W.
[0093] Because the center discharge port 411 is disposed less
densely at the center of the etching liquid nozzle 407 than in the
other regions of the etching liquid nozzle 407, a discharge flow
rate of the etching liquid discharged directly to the center of the
bottom surface 9 of the wafer W is lower than the discharge flow
rates in the other regions. It is thus possible to suppress an
increase of the etching rate at the center of the wafer W where the
moving speeds at the respective positions on the bottom surface 9
of the wafer W are relatively slow.
[0094] In particular, because the center discharge port 411 is
disposed at the position displaced in the rotation radius direction
of the wafer W from the position opposing the rotation center C of
the bottom surface 9 of the wafer W, it is possible to effectively
suppress an increase of the etching rate particularly at the
rotation center C of the wafer W.
[0095] Further, the discharge flow rates of the larger diameter
discharge ports 413 are higher than the discharge flow rates of the
other peripheral discharge ports 412. It is therefore possible to
suppress a decrease of the etching rate in the peripheral edge of
the wafer W where the moving speeds of the respective positions on
the bottom surface 9 are relatively fast. It is thus possible to
apply the etching processing uniformly across the entire bottom
surface 9 of the wafer W.
[0096] FIG. 5 is a graph showing the in-plane distribution of
etching amounts in etching tests. The abscissa is used for the
X-axis coordinate in reference to the rotation center C of the
wafer W.
[0097] Etching tests were conducted by discharging hydrofluoric
acid at 55.degree. C. (concentration: 50 wt %) at a discharge flow
rate of 1.0 L/min from etching liquid nozzles of Example 1 and
Example 2 described above and Comparative Example described below
to the bottom surface (surface on the device forming region side) 9
of the wafer W made of oxide film silicon having an outer diameter
of 300 mm and rotating at a rate of 1000 rpm. In the etching tests
to measure the in-plane distribution of etching amounts, the
etching time was 11 seconds.
[0098] The distribution of the etching amount was measured by
measuring etching amounts at plural points on a straight line
passing through the rotation center C of the wafer W. In FIG. 5,
etching amounts were measured at points at every 6.3 mm interval in
two opposite directions from the rotation center C of the wafer
W.
[0099] Comparative Example was a case where the etching test was
conducted under the same conditions as described above using a
so-called bevel etching liquid nozzle. The configuration of the
etching liquid nozzle of Comparative Example is described in United
States Patent Application Publication No. US2003/0194878A1
supra.
[0100] In a case where the etching liquid nozzle of Example 1 was
used, the etching uniformity was 10.56%. In a case where the
etching liquid nozzle of Example 2 was used, the etching uniformity
was 5.29%. In a case where the etching liquid nozzle of Comparative
Example was used, the etching uniformity was 8.98%. The etching
uniformity is expressed by Equation (1):
etching uniformity (%)=100.times.(maximum etching amount-minimum
etching amount)/2/average etching amount (1)
[0101] FIG. 6 is a view showing flown over amounts of the etching
liquid in etching tests.
[0102] Etching tests were conducted under the same conditions as
above to measure flown over amounts. In the etching tests to
measure the flown over amounts, the etching time was 135 seconds.
The etching test was conducted seven times to measure the maximum
flown over amount and the average flown over amount in the
peripheral edge on the top surface of the wafer W.
[0103] In a case where the etching liquid nozzle 307 of Example 1
was used, an average flown over amount was 0.80 mm and the maximum
flown over amount was 0.90 mm and no traces of etching were
observed in portions abutted on the pinching members 303. In a case
where the etching liquid nozzle 407 of Example 2 was used, the
average flown over amount was 1.10 mm and the maximum flown over
amount was 1.25 mm, and traces of etching of 0.5 mm at the maximum
were observed in portions abutted on the pinching members 303. In a
case where the etching liquid nozzle in the related art was used,
the average flown over amount was 1.21 mm and the maximum flown
over amount was 1.55 mm, and traces of etching of 1.55 mm at the
maximum were observed in portions abutted on the pinching members
303.
[0104] It is understood from FIG. 5 and FIG. 6 that flowing over
onto the top surface of the wafer W was suppressed particularly in
a case where the etching liquid nozzle 307 of Example 1 was used.
Also, it is understood that not only was it possible to suppress
the flowing over onto the top surface of the wafer W, but it was
also possible to achieve excellent in-plane uniformity by etching
in a case where the etching liquid nozzle 407 of Example 2 was
used.
[0105] FIG. 7 is a plan view of a spin chuck in a substrate
processing apparatus 500 according to still another embodiment
(third embodiment) of the invention. In the third embodiment,
portions corresponding to the respective portions described in the
first embodiment above are labeled with the same reference numerals
as those in FIG. 1 and FIG. 2, and descriptions of these portions
are omitted. In the third embodiment, an etching liquid nozzle 507
is not in the shape of a straight line when viewed in a plane but
in the shape of a cross when viewed in a plane.
[0106] The etching liquid nozzle 507 has four long array nozzle
portions 508 extending radially in the rotation radius direction of
the wafer W from the rotation shaft line 1a of the wafer W, and the
respective array nozzle portions 508 are disposed at equiangular
intervals of 90.degree.. A rotation shaft discharge port 511
disposed on the rotation shaft line 1a of the wafer W and plural
peripheral discharge ports 512 lined up along the shapes of the
respective array nozzle portions 508 (along the rotation radius
direction of the wafer W) are provided to the top surface of the
etching liquid nozzle 507. A supply channel 513 through which the
etching liquid is supplied to the respective discharge ports 511
and 512 is in the shape of a cross extending along the shapes of
the respective array nozzle portions 508 and crossing on the
rotation shaft line 1a when viewed in a plane.
[0107] Because the etching liquid nozzle 507 has a cross shape when
viewed in a plane, an etching liquid at a high temperature is
successively supplied directly across the entire bottom surface 9
of the wafer W. It is thus possible to etch away the entire bottom
surface 9 of the wafer W at a high etching rate.
[0108] While three embodiments have been described, it should be
appreciated that the invention is applicable not only to the
etching processing for removing an oxide film on the semiconductor
wafer W, but also to etching processing for other purposes.
Hereinafter, a case where the invention is applied to etching
processing for thinning a semiconductor wafer will be
described.
[0109] FIG. 8 is a cross section schematically showing the
configuration of a substrate processing apparatus 100 according to
still another embodiment (fourth embodiment) of the invention.
[0110] For thinning the semiconductor wafer W, for example,
hydrofluoric-nitric acid (a mixed liquid of hydrofluoric acid and
nitric acid) is used as the etching liquid.
[0111] Hydrofluoric-nitric acid is an etching liquid having
extremely high etching power. However, it loses its etching power
and deteriorates as soon as it exerts an etching action when it
comes into contact with a subject subjected to etching. Hence, when
the etching processing is applied to the semiconductor wafer using
hydrofluoric-nitric acid, only a region brought into a direct
contact with fresh hydrofluoric-nitric acid is sufficiently etched
away and a region not brought into a direct contact with fresh
hydrofluoric-nitric acid is etched away insufficiently. This raises
a problem that the etching processing gives rise to in-plane
nonuniformity.
[0112] Referring to FIG. 8, the substrate processing apparatus 100
is a single substrate process type apparatus to apply etching
processing for thinning to the wafer W on the back surface (bottom
surface) 10 opposite to the surface (top surface) on the device
forming region side. In this embodiment, hydrofluoric-nitric acid
(a mixed liquid of hydrofluoric acid and nitric acid) is used as
the etching liquid. The wafer W, on the top surface of which
devices have been formed, is placed in the substrate processing
apparatus 100 with the surface on the device forming region side
faced up. The substrate processing apparatus 100 includes a spin
chuck 1 as a substrate holding unit that rotates about a vertical
rotation shaft line 1a passing through almost the center of the
wafer W while holding the wafer W in an almost horizontal
posture.
[0113] FIG. 9 is a plan view schematically showing the
configuration of the spin chuck 1 in the substrate processing
apparatus 100 shown in FIG. 8.
[0114] Referring to FIG. 8 and FIG. 9, the spin chuck 1 has a
disc-like spin base 2. Plural (six in this embodiment) pinching
members 3 are disposed on the top surface of the spin base 2 almost
at equiangular intervals along the peripheral edge. The spin base 2
is configured to rotate by being coupled to the top end of a
rotation shaft 5 that is rotated by a chuck rotary driving
mechanism 4 including a motor. The rotation shaft 5 is a hollow
shaft, inside of which an insertion tube 6 is inserted through. The
insertion tube 6 is held inside the rotation shaft 5 in a
non-rotating state.
[0115] An etching liquid nozzle 7 in the shape of a cross when
viewed in a plane is disposed on the spin base 2. The etching
liquid nozzle 7 has four long array nozzle portions 8 extending
radially in the rotation radius direction of the wafer W from the
rotation shaft line 1a, and the respective array nozzle portions 8
are disposed at equiangular intervals of 90.degree.. Distances from
the tip ends of the respective array nozzle portions 8 to the
rotation shaft line 1a are all equal, and the tip ends of the
respective array nozzle portions 8 are located at positions
slightly inner than the end edge of the spin base 2. The etching
liquid nozzle 7 is made hollow inside and linked to the insertion
tube 6 at the center position at the bottom thereof. The etching
liquid nozzle 7 thus remains stationary and will never rotate in
association with rotations of the spin base 2.
[0116] A rotation shaft discharge port 11 disposed on the rotation
shaft line 1a and plural peripheral discharge ports 12 lined up
along the shapes of the respective array nozzle portions 8 (along
the rotation radius direction of the wafer W) are provided to the
top surface of the etching liquid nozzle 7. The peripheral
discharge ports 12 are disposed more densely with distance from the
rotation shaft line 1a of the wafer W. To be more concrete, the
peripheral discharge ports 12 are disposed at shorter intervals as
distances from the rotation shaft line 1a increase. A supply
channel 13 communicating with the respective discharge ports 11 and
12 is formed inside the etching liquid nozzle 7. The supply channel
13 is in the shape of a cross extending along the shapes of the
respective array nozzle portions 8 and crossing on the rotation
shaft line 1a when viewed in a plane.
[0117] A circulation channel 14 is formed inside the insertion tube
6 along the rotation shaft line 1a. The circulation channel 14
communicates with the supply channel 13. An etching liquid is
supplied to the circulation channel 14 from an etching liquid
supply source via an etching liquid valve 15. Also, deionized water
is supplied to the circulation channel 14 from a deionized water
supply source via a deionized water valve 16.
[0118] According to the configuration as above, by closing the
deionized water valve 16 and opening the etching liquid valve 15,
it is possible to supply the etching liquid to the rotation shaft
discharge port 11 and the peripheral discharge ports 12 of the
etching liquid nozzle 7 via the circulation channel 14 and the
supply channel 13. Conversely, by closing the etching liquid valve
15 and opening the deionized water valve 16, it is possible to
supply deionized water to the rotation shaft discharge port 11 and
the peripheral discharge ports 12 of the etching liquid nozzle 7
via the circulation channel 14 and the supply channel 13. In
addition, a gas supply channel 17 is defined between the inner wall
surface of the rotation shaft 5 formed of a hollow shaft and the
outer wall surface of the insertion tube 6. The gas supply tube 17
opens to the top surface of the spin base 2. It is configured in
such a manner that a nitrogen gas as an inert gas is supplied to
the gas supply channel 17 via a nitrogen gas valve 18.
[0119] A disc-shaped shield plate 20 having substantially the same
diameter as the wafer W is provided above the spin chuck 1. The
shield plate 20 has an opening 19 at the center thereof. A rotation
shaft 21 extending along a shaft line common with the rotation
shaft line 1a of the spin chuck 1 is fixed to the top surface of
the shield plate 20. The rotation shaft 21 is made hollow, inside
of which is formed a gas supply channel 23 that communicates with
the opening 19 in the shield plate 20 and thereby supplies a
nitrogen gas toward the center of the wafer W. It is configured in
such a manner that a nitrogen gas is supplied to the gas supply
channel 23 via a nitrogen gas valve 24.
[0120] The rotation shaft 21 is provided with a shield plate
elevation driving mechanism 25 to move the shield plate 20 up and
down between a proximity position at which the shield plate 20
comes in close proximity to the top surface of the wafer W held by
the spin chuck 1 and an evacuation position at which the shield
plate 20 evacuates far above the spin chuck 1, and a shield plate
rotary driving mechanism 26 to rotate the shield plate 20 almost in
sync with rotations of the wafer W by the spin chuck 1.
[0121] Hereinafter, etching processing applied to the bottom
surface 10 of the wafer W by the substrate processing apparatus 100
will be described.
[0122] Before the wafer W subjected to processing is carried into
the substrate processing apparatus 100, the shield plate 20 is
located at the evacuation position at which it evacuates far above
the spin chuck 1 so as not to interrupt a carry-in operation.
[0123] In order to process the wafer W, the wafer W is first
carried into the substrate processing apparatus 100 by an
unillustrated delivery robot, and the wafer W is held by the spin
base 2 of the spin chuck 1 with the surface on the device forming
region side faced up. When the wafer W is held by the spin base 2,
the chuck rotary driving mechanism 4 is controlled for the spin
base 2 to start to rotate the wafer W, and the rotating speed of
the wafer W is increased, for example, to 3000 rpm. In this
instance, the etching liquid nozzle 7 remains stationary as has
been described above and will never rotate in association with
rotations of the spin base 2. Also, the shield plate elevation
driving mechanism 25 is controlled for the shield plate 20 to move
down to the proximity position at which it comes in close proximity
to the top surface of the wafer W held by the spin base 2. The
shield plate rotary driving mechanism 26 is then controlled for the
shield plate 20 to keep rotating in the same direction as the wafer
W, while the nitrogen gas valve 24 is opened for a nitrogen gas to
be supplied from the opening 19 in the shield plate 20 to a space
between the wafer W and the shield plate 20. Accordingly, a current
of nitrogen gas flowing outward in the radial direction from the
center of the shield plate 20 is produced in the space between the
wafer W and the shield plate 20.
[0124] When the rotating speed of the wafer W reaches, for example,
3000 rpm, the etching liquid valve 15 is opened, and the etching
liquid is discharged from the rotation shaft discharge port 11 and
the respective peripheral discharge ports 12 of the etching liquid
nozzle 7 toward the bottom surface 10 of the wafer W that is
rotating. The nitrogen gas valve 18 is also opened and a nitrogen
gas is supplied to a space surrounded by the spin base 2 and the
bottom surface 10 of the wafer W. The space surrounded by the spin
base 2 and the wafer W is eventually filled with a nitrogen
gas.
[0125] In this instance, the etching liquid discharged from the
rotation shaft discharge port 11 is supplied directly to the center
of the wafer W. The etching liquid discharged from the respective
peripheral discharge ports 12 is supplied directly to the bottom
surface 10 of the wafer W in regions opposing the respective
peripheral discharge ports 12. As has been described, the
peripheral discharge ports 12 are disposed more densely with
distance from the rotation shaft line 1a of the wafer W. Discharge
flow rates of the etching liquid therefore become higher with
distance from the rotation shaft line 1a of the wafer W. Meanwhile,
moving speeds of the respective positions on the surface of the
wafer W become faster with distance from the rotation shaft line 1a
of the wafer W. Discharge flow rates of the etching liquid per unit
area therefore become equal almost across the entire bottom surface
10 of the wafer W. In other words, a fresh etching liquid is
supplied uniformly almost across the entire bottom surface 10 of
the wafer W that is rotating.
[0126] Hydrofluoric-nitric acid used as the etching liquid in this
embodiment has extremely high etching power when it is fresh.
However, it deteriorates so fast that it loses its etching power
almost completely in an instant.
[0127] Nevertheless, because a fresh etching liquid is uniformly
supplied almost across the wafer W that is rotating, the bottom
surface 10 of the wafer W is uniformly etched away at an extremely
high etching rate (about 50 .mu.m/min at normal temperature). In
addition, because the etching liquid nozzle 7 has a cross shape
when viewed in a plane, a fresh etching liquid is successively
supplied across the entire bottom surface 10 of the wafer W that is
rotating.
[0128] Further, because the space surrounded by the spin base 2 and
the bottom surface 10 of the wafer W is filled with a nitrogen gas,
it is possible to suppress deterioration of the etching liquid
supplied to the wafer W.
[0129] The etching liquid supplied to the bottom surface 10 of the
wafer W flows toward the peripheral edge by running over the bottom
surface 10 of the wafer W owing to a centrifugal force induced by
rotations of the wafer W and wasted to the outside of the wafer W
from the peripheral edge. Because a current of nitrogen gas flowing
outward in the radial direction from the center of the shield plate
20 is produced in the space between the wafer W (top surface) and
the shield plate 20, the etching liquid flowing toward the
peripheral edge of the wafer W will not flow over onto the top
surface of the wafer W. It is thus possible to prevent the devices
formed on the top surface of the wafer W from being damaged by the
etching liquid.
[0130] When a predetermined time (for example, ten minutes) has
elapsed since the supply of the etching liquid started, the etching
liquid valve 15 is closed. The deionized water valve 16 is then
opened for deionized water to be supplied across the entire bottom
surface 10 of the wafer W from the rotation shaft discharge port 11
and the peripheral discharge ports 12. The rotating speed of the
wafer W is reduced, for example, from 3000 rpm to 1500 rpm. In this
instance, deionized water discharged from the rotation shaft
discharge port 11 is supplied directly to the center of the wafer
W. Deionized water discharged from the respective peripheral
discharge ports 12 is supplied directly to the bottom surface 10 of
the wafer W in regions opposing the respective peripheral discharge
ports 12.
[0131] Deionized water supplied to the bottom surface 10 of the
wafer W flows toward the peripheral edge of the wafer W owing to a
centrifugal force induced by rotations of the wafer W. Deionized
water is then wasted to the outside from the peripheral edge of the
wafer W. The etching liquid adhering onto the bottom surface 10 of
the wafer W is thus rinsed away by deionized water.
[0132] A current of nitrogen gas flowing outward in the rotation
radial direction from the center of the shield plate 20 is produced
in the space between the wafer W and the shield plate 20.
Accordingly, a mixed liquid of deionized water and the etching
liquid flowing toward the peripheral edge of the wafer W will not
flow over onto the top surface of the wafer W. It is thus possible
to prevent the devices formed on the top surface of the wafer W
from being damaged by the etching liquid.
[0133] When a predetermined time (for example, 30 seconds) has
elapsed since the supply of deionized water started, the deionized
water valve 16 is closed to stop the supply of deionized water to
the bottom surface 10 of the wafer W. In addition, the nitrogen gas
valve 24 is closed and the shield plate elevation driving mechanism
25 is controlled for the shield plate 20 to move up to the
evacuation position at which it evacuates far above the spin chuck
1.
[0134] The rotating speed of the wafer W is then increased from
1500 rpm to 3000 rpm to apply spin dry processing in which the
wafer W is dried by throwing off deionized water adhering onto the
surface thereof using a centrifugal force after the water rinse
processing. When the spin dry processing is applied over, for
example, 120 seconds, the wafer W is stopped rotating, and the
wafer W having undergone the etching processing is carried out from
the spin chuck 1.
[0135] As has been described, according to the fourth embodiment,
the etching liquid discharged from the rotation shaft discharge
port 11 is supplied directly to the center of the wafer W and the
etching liquid discharged from the respective peripheral discharge
ports 12 is supplied directly to the bottom surface 10 of the wafer
W in portions opposing the respective peripheral discharge ports
12. Because the peripheral discharge ports 12 are disposed more
densely with distance from the rotation shaft line 1a of the wafer
W, while the wafer W is rotating, a fresh etching liquid is
supplied uniformly almost across the entire bottom surface 10 of
the wafer W that is rotating. The etching liquid has extremely high
etching power when it is fresh. It is thus possible to apply the
etching processing uniformly almost across the entire bottom
surface 10 of the wafer W at a high etching rate.
[0136] In addition, because the etching liquid nozzle 7 has a cross
shape when viewed in a plane, a fresh etching liquid is
successively supplied directly across the entire bottom surface 10
of the wafer W. It is thus possible to apply the etching processing
to the bottom surface 10 of the wafer W at a high etching rate.
[0137] FIG. 10 is a plan view of a spin chuck in a substrate
processing apparatus 200 according to still another embodiment
(fifth embodiment) of the invention. An etching liquid nozzle 107
of the substrate processing apparatus 200 of the fifth embodiment
is different from the etching liquid nozzle 7 of FIG. 4 in that it
is not in the shape of a cross when viewed in a plane but it is in
the shape of a straight line when viewed in a plane. In other
words, the etching liquid nozzle 107 is a long nozzle extending
along the rotation radius direction of the wafer W by passing
through the rotation shaft line 1a. The both ends of the etching
liquid nozzle 107 extend to positions slightly inner than the
peripheral edge of the spin base 2.
[0138] A rotation shaft discharge port 111 disposed in a region
opposing the rotation center C of the wafer W and plural peripheral
discharge ports 112 lined up along the shape of the etching liquid
nozzle 107 (along the rotation radius direction of the wafer W) are
provided to the top surface of the etching nozzle 107. As with the
peripheral discharge ports 12 of FIG. 9, the peripheral discharge
ports 112 are disposed more densely (at short intervals) with
distance from the rotation shaft center C of the wafer W. Hence,
while the wafer W is rotating, discharge flow rates of the etching
liquid per unit area become equal almost across the entire bottom
surface 10 of the wafer W. A fresh etching liquid is thus supplied
uniformly almost across the entire bottom surface 10 of the wafer W
that is rotating.
[0139] While five embodiments have been described, it should be
appreciated that the invention can be implemented in still another
embodiment. For example, the etching liquid nozzle 507 having a
cross shape when viewed in a plane in the third embodiment above
may be configured in such a manner that the discharge port is not
provided at the position opposing the rotation center C of the
wafer W as with the etching liquid nozzle 407 in the second
embodiment above. Also, as with the etching liquid nozzle 407 of
the second embodiment, larger diameter discharge ports having a
larger diameter than the other discharge ports may be provided to
the both ends of the etching liquid nozzle 507.
[0140] The substrate processing apparatus 100 and 200 in the fourth
and fifth embodiments above, respectively, are configured in such a
manner that an etching liquid at normal temperature is discharged
from the respective discharge ports 11 and 12 and the respective
discharge ports 111 and 112 provided to the etching liquid nozzles
7 and 107, respectively. However, as in the first embodiment above,
they may be provided with a heater to heat the etching liquid to be
discharged from the respective discharge ports 11 and 12 and the
respective discharge ports 111 and 112 provided to the etching
liquid nozzles 7 and 107, respectively.
[0141] The etching liquid nozzles 7 and 107 of the fourth and fifth
embodiments, respectively, may be configured in such a manner that
density of the discharge ports is increased with distance from the
rotation center C by increasing the number of aligned lines with
distance from the rotation center C. Alternatively, the etching
liquid nozzle may be formed in the shape of a disc opposing the
bottom surface 10 of the wafer W to distribute the discharge ports
homogeneously on the top surface thereof.
[0142] The respective embodiments above have described cases where
the etching liquid nozzles 7, 107, 307, 407, and 507 are in the
shape of a cross or in the shape of a straight line when viewed in
a plane. However, the etching liquid nozzle may extend radially in
an arbitrary number of directions at equiangular intervals, for
example, in three, five, six, seven, or eight directions extending
outward in the rotation radius direction from the rotation center C
when viewed in a plane. Further, the etching liquid nozzles may
have a length extending in one rotation radius direction of the
wafer W from the rotation center C (that is, a length about the
half of the etching liquid nozzles 307, 407, and 107 shown in FIG.
2, FIG. 3, and FIG. 10, respectively).
[0143] The respective embodiments have described a case where the
peripheral discharge ports 312, 412, 413, 512, 12, and 112 are
formed in a line in the rotation radius direction. However, the
peripheral discharge ports 312, 412, 413, 512, 12, and 112 may be
formed in more than one line.
[0144] Further, the etching liquid nozzles 307, 407, 507, 7, and
107 may be configured to be rotatable about the rotation shaft line
1a together with the insertion tubes 306 and 6, so that the etching
liquid is discharged toward the wafer W from the etching liquid
nozzles 307, 407, 507, 7, and 107 that are rotating.
[0145] While the embodiments of the invention have been described
in detail, it should be appreciated that these embodiments
represent examples to provide clear understanding of the technical
contents of the invention, and the invention is not limited to
these examples. The sprit and the scope of the invention,
therefore, are limited solely by the scope of the appended
claims.
[0146] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No. 2006-276502
filed with the Japanese Patent Office on Oct. 10, 2006 and the
prior Japanese Patent Application No. 2007-41313 filed with the
Japanese Patent Office on Feb. 21, 2007, the entire contents of
which are incorporated herein by reference.
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