U.S. patent application number 12/877272 was filed with the patent office on 2011-03-17 for substrate liquid-processing method, substrate liquid-processing apparatus, and storage medium.
This patent application is currently assigned to Tokyo Electron Limited. Invention is credited to Tsuyoshi MIZUNO, Hiromitsu Namba.
Application Number | 20110062114 12/877272 |
Document ID | / |
Family ID | 43729466 |
Filed Date | 2011-03-17 |
United States Patent
Application |
20110062114 |
Kind Code |
A1 |
MIZUNO; Tsuyoshi ; et
al. |
March 17, 2011 |
SUBSTRATE LIQUID-PROCESSING METHOD, SUBSTRATE LIQUID-PROCESSING
APPARATUS, AND STORAGE MEDIUM
Abstract
First, hydrofluoric acid is supplied to the circumferential edge
of a substrate W while the substrate W provided with a polysilicon
film is rotated, to remove a natural oxide film provided along the
circumferential edge of the substrate W by etching so as to expose
the polysilicon film. Next, hydrofluoric-nitric acid is supplied to
the circumferential edge of the substrate W while the substrate W
from which the polysilicon film is exposed is rotated, to remove
the polysilicon film by etching. Such operation is performed by
controlling a rotational driving unit 20, a hydrofluoric acid
supplying unit 54, and a hydrofluoric-nitric acid supplying unit 52
by a control unit 50 of a substrate liquid-processing apparatus
1.
Inventors: |
MIZUNO; Tsuyoshi;
(Koshi-Shi, JP) ; Namba; Hiromitsu; (Koshi-Shi,
JP) |
Assignee: |
Tokyo Electron Limited
Minato-Ku
JP
|
Family ID: |
43729466 |
Appl. No.: |
12/877272 |
Filed: |
September 8, 2010 |
Current U.S.
Class: |
216/83 ;
156/345.15 |
Current CPC
Class: |
H01L 21/32134 20130101;
H01L 21/02087 20130101; H01L 21/6708 20130101 |
Class at
Publication: |
216/83 ;
156/345.15 |
International
Class: |
C23F 1/24 20060101
C23F001/24; C23F 1/08 20060101 C23F001/08 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 17, 2009 |
JP |
2009-215438 |
Claims
1. A substrate liquid-processing apparatus comprising: a holding
unit configured to hold a substrate; a rotational driving unit
configured to rotate the holding unit; a hydrofluoric acid
supplying unit configured to supply hydrofluoric acid to the
circumferential edge of the substrate held by the holding unit; a
hydrofluoric-nitric acid supplying unit configured to supply
hydrofluoric-nitric acid to the circumferential edge of the
substrate held by the holding unit; and a control unit configured
to control the rotational driving unit, the hydrofluoric acid
supplying unit, and the hydrofluoric-nitric acid supplying unit,
the control unit performing control such that the hydrofluoric acid
is supplied to the circumferential edge of the substrate by the
hydrofluoric acid supplying unit while the substrate provided with
a polysilicon film is rotated, to remove a natural oxide film
provided along the circumferential edge of the substrate by etching
so as to expose the polysilicon film, and then the
hydrofluoric-nitric acid is supplied to the circumferential edge of
the substrate by the hydrofluoric-nitric acid supplying unit while
the substrate from which the polysilicon film is exposed is
rotated, to remove the polysilicon film by etching.
2. The substrate liquid-processing apparatus according to claim 1,
wherein the control unit performs the control of the rotational
driving unit so as to rotate the substrate, when the
hydrofluoric-nitric acid is supplied to the circumferential edge of
the substrate, at a rotation speed lower than that when the
hydrofluoric acid is supplied to the circumferential edge of the
substrate.
3. The substrate liquid-processing apparatus according to claim 1,
wherein the hydrofluoric-nitric acid supplying unit supplies the
hydrofluoric-nitric acid to the position outward in the diameter
direction of the substrate from the position in which the
hydrofluoric acid is supplied to the substrate when the
hydrofluoric acid is supplied to the circumferential edge of the
substrate by the hydrofluoric acid supplying unit.
4. The substrate liquid-processing apparatus according to claim 3,
wherein the hydrofluoric-nitric acid supplying unit is positioned
outward in the diameter direction of the substrate held by the
holding unit from the hydrofluoric acid supplying unit.
5. A substrate liquid-processing method which uses the substrate
liquid-processing apparatus according to claim 1, comprising:
supplying hydrofluoric acid to the circumferential edge of a
substrate while the substrate provided with a polysilicon film is
rotated, to remove a natural oxide film provided along the
circumferential edge of the substrate by etching so as to expose
the polysilicon film; and supplying hydrofluoric-nitric acid to the
circumferential edge of the substrate while the substrate from
which the polysilicon film is exposed is rotated, to remove the
polysilicon film by etching.
6. The substrate liquid-processing method according to claim 5,
wherein when the hydrofluoric-nitric acid is supplied to the
circumferential edge of the substrate, the substrate is rotated at
a rotation speed lower than that when the hydrofluoric acid is
supplied to the circumferential edge of the substrate.
7. The substrate liquid-processing method according to claim 5,
wherein when the hydrofluoric-nitric acid is supplied to the
circumferential edge of the substrate, the hydrofluoric-nitric acid
is supplied to the position outward in the diameter direction of
the substrate from the position in which the hydrofluoric acid is
supplied to the substrate when the hydrofluoric acid is supplied to
the circumferential edge of the substrate.
8. A storage medium which stores a program capable of being
executed by a control computer of the substrate liquid-processing
apparatus according to claim 1, in which the program is executed so
that the control computer controls the substrate liquid-processing
apparatus to execute the substrate liquid-processing method, the
substrate liquid-processing method including: supplying
hydrofluoric acid to the circumferential edge of a substrate while
the substrate provided with a polysilicon film is rotated, to
remove a natural oxide film provided along the circumferential edge
of the substrate by etching so as to expose the polysilicon film;
and supplying hydrofluoric-nitric acid to the circumferential edge
of the substrate while the substrate from which the polysilicon
film is exposed is rotated, to remove the polysilicon film by
etching.
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. 2009-215438
filed on Sep. 17, 2009, the entire contents of which are
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a substrate
liquid-processing method, a substrate liquid-processing apparatus
and a storage medium for removing a polysilicon film along the
circumferential edge of a substrate, such as a semiconductor wafer,
provided with the polysilicon film by etching.
BACKGROUND OF THE INVENTION
[0003] In a manufacturing process of a semiconductor device, there
is a process for providing a polysilicon film in order to form a
gate electrode or the like with respect to a semiconductor wafer
(hereinafter, also simply called a wafer) as a processed substrate.
However, there is a possibility that cracks and film separation can
occur along the circumferential edge, such as the edge and bevel,
of the wafer. When such cracks and film separation occur, the
polysilicon film may become particles and contaminate the
semiconductor device.
[0004] For this reason, the polysilicon film along the
circumferential edge of the wafer has conventionally been removed.
When the polysilicon film is removed, an etching method using, as
an etching solution, hydrofluoric-nitric acid which is a mixing
solution of hydrofluoric acid and nitric acid has hitherto been
adopted. Specifically, a portion not to be removed is protected by
a protective film (resist and hard mask), and only the
circumferential edge (edge and bevel) of the wafer is exposed and
the entire wafer into hydrofluoric-nitric acid is immersed.
[0005] However, such method is required to provide the protective
film according to a portion to be etched, with the result that the
process becomes troublesome and the number of processes is
increased. In addition, the adjustment of the cut width of the
polysilicon film is not easy.
[0006] On the contrary, although it is not the technique of
removing a polysilicon film, JP2001-319850A proposes a technique in
which after a film is provided over a wafer, a chemical solution is
supplied to a bevel portion while the wafer is rotated, to remove
the bevel portion by etching. It can be considered to be applied to
the etching of the polysilicon film provided along the
circumferential edge of the wafer.
DISCLOSURE OF THE INVENTION
[0007] However, if a hydrophobic polysilicon film is provided over
a wafer and a hydrophilic natural oxide film is stacked over the
polysilicon film, when hydrofluoric-nitric acid is supplied to the
circumferential, edge of the wafer using the method disclosed in
JP2001-319850A, it is found that the occurrence of etching failure
of the polysilicon film cannot be sufficiently prevented and that
the accuracy of an etching width is low.
[0008] An object of the present invention is to provide a substrate
liquid-processing method, a substrate liquid-processing apparatus
and a storage medium which, when a hydrophobic polysilicon film is
provided over a wafer and a hydrophilic natural oxide film is
stacked over the polysilicon film, can prevent the occurrence of
etching failure along the circumferential edge of the wafer and
improve the accuracy of an etching width.
[0009] The substrate liquid-processing apparatus of the present
invention includes: a holding unit configured to hold a substrate;
a rotational driving unit configured to rotate the holding unit; a
hydrofluoric acid supplying unit configured to supply hydrofluoric
acid to the circumferential edge of the substrate held by the
holding unit; a hydrofluoric-nitric acid supplying unit configured
to supply hydrofluoric-nitric acid to the circumferential edge of
the substrate held by the holding unit; and a control unit
configured to control the rotational driving unit, the hydrofluoric
acid supplying unit, and the hydrofluoric-nitric acid supplying
unit, the control unit performing control such that the
hydrofluoric acid is supplied to the circumferential edge of the
substrate by the hydrofluoric acid supplying unit while the
substrate provided with a polysilicon film is rotated, to remove a
natural oxide film provided along the circumferential edge of the
substrate by etching so as to expose the polysilicon film, and then
the hydrofluoric-nitric acid is supplied to the circumferential
edge of the substrate by the hydrofluoric-nitric acid supplying
unit while the substrate from which the polysilicon film is exposed
is rotated, to remove the polysilicon film by etching.
[0010] In the substrate liquid-processing apparatus of the present
invention, the control unit may perform the control of the
rotational driving unit so as to rotate the substrate, when the
hydrofluoric-nitric acid is supplied to the circumferential edge of
the substrate, at a rotation speed lower than that when the
hydrofluoric acid is supplied to the circumferential edge of the
substrate.
[0011] In the substrate liquid-processing apparatus of the present
invention, the hydrofluoric-nitric acid supplying unit may supply
the hydrofluoric-nitric acid to the position outward in the
diameter direction of the substrate from the position in which the
hydrofluoric acid is supplied to the substrate when the
hydrofluoric acid is supplied to the circumferential edge of the
substrate by the hydrofluoric acid supplying unit.
[0012] In this case, the hydrofluoric-nitric acid supplying unit
may be positioned outward in the diameter direction of the
substrate held by the holding unit from the hydrofluoric acid
supplying unit.
[0013] The substrate liquid-processing method of the present
invention uses the substrate liquid-processing apparatus described
above and includes: supplying hydrofluoric acid to the
circumferential edge of a substrate while the substrate provided
with a polysilicon film is rotated, to remove a natural oxide film
provided along the circumferential edge of the substrate by etching
so as to expose the polysilicon film; and supplying
hydrofluoric-nitric acid to the circumferential edge of the
substrate while the substrate from which the polysilicon film is
exposed is rotated, to remove the polysilicon film by etching.
[0014] In the substrate liquid-processing method of the present
invention, when the hydrofluoric-nitric acid is supplied to the
circumferential edge of the substrate, the substrate may be rotated
at a rotation speed lower than that when the hydrofluoric acid is
supplied to the circumferential edge of the substrate.
[0015] In the substrate liquid-processing method of the present
invention, when the hydrofluoric-nitric acid is supplied to the
circumferential edge of the substrate, the hydrofluoric-nitric acid
may be supplied to the position outward in the diameter direction
of the substrate from the position in which the hydrofluoric acid
is supplied to the substrate when the hydrofluoric acid is supplied
to the circumferential edge of the substrate.
[0016] The storage medium of the present invention stores a program
capable of being executed by a control computer of the substrate
liquid-processing apparatus described above, in which the program
is executed so that the control computer controls the substrate
liquid-processing apparatus to execute the substrate
liquid-processing method, and includes: supplying hydrofluoric acid
to the circumferential edge of a substrate while the substrate
provided with a polysilicon film is rotated, to remove a natural
oxide film provided along the circumferential edge of the substrate
by etching so as to expose the polysilicon film; and supplying
hydrofluoric-nitric acid to the circumferential edge of the
substrate while the substrate from which the polysilicon film is
exposed is rotated, to remove the polysilicon film by etching.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic longitudinal sectional view of a
substrate liquid-processing apparatus according to an embodiment of
the present invention;
[0018] FIG. 2 is a control block diagram of the substrate
liquid-processing apparatus shown in FIG. 1;
[0019] FIG. 3 is a flowchart showing a wafer processing method by
the substrate liquid-processing apparatus shown in FIG. 1; and
[0020] FIGS. 4A, 4B, and 4C are explanatory views each showing a
region on the surface of a wafer, to which each chemical solution
or a rinse solution is supplied, by the wafer processing method
shown in FIG. 3.
DETAILED DESCRIPTION OF THE INVENTION
[0021] Hereinafter, an embodiment of the present invention will be
described with reference to the drawings. FIGS. 1 to 4C are
diagrams showing a substrate liquid-processing apparatus and a
substrate liquid-processing method according to this embodiment.
More specifically, FIG. 1 is a schematic longitudinal sectional
view of the substrate liquid-processing apparatus according to this
embodiment, and FIG. 2 is a control block diagram of the substrate
liquid-processing apparatus shown in FIG. 1. In addition, FIG. 3 is
a flowchart showing a wafer processing method by the substrate
liquid-processing apparatus shown in FIG. 1. Further, FIGS. 4A to
4C are explanatory views each showing a region on the surface of a
wafer, to which each chemical solution or a rinse solution is
supplied, by the wafer processing method shown in FIG. 3.
[0022] As shown in FIG. 1, a substrate liquid-processing apparatus
1 has a holding unit 10 which holds a substrate W (hereinafter,
also called a wafer W), such as a semiconductor wafer, into a
substantially horizontal state, a rotational shaft 12 extending
downward from the holding unit 10, and a rotational driving unit 20
which rotates the holding unit 10 via the rotational shaft 12. The
holding unit 10 holds the wafer W placed on the holding unit 10 by,
e.g., vacuum absorption.
[0023] As shown in FIG. 1, the rotational shaft 12 extends in the
vertical direction. The rotational driving unit 20 has a pulley 24
arranged outward of the circumferential edge of the lower end of
the rotational shaft 12, a driving belt 26 entrained on the pulley
24, and a motor 22 which rotates the rotational shaft 12 via the
pulley 24 by applying a driving force to the driving belt 26. In
addition, a bearing 14 is arranged outward of the circumferential
edge of the rotational shaft 12 in the position above the pulley
24.
[0024] A chamber 2 covering the wafer W is provided around the
wafer W held by the holding unit 10. An upper opening 4 which sends
a gas, such as an N2 gas (nitrogen gas) or the like, to the wafer W
by downflow is formed in the upper portion (ceiling portion) of the
chamber 2. In addition, lower openings 5 for exhausting the gas
sent from the upper opening 4 by downflow from the inside of the
chamber 2 are formed in the lower portion (bottom portion) of the
chamber 2. Further, a side opening 3 for passing a transferring arm
which transfers the wafer W into the chamber 2 or transfers out the
wafer W from the inside of the chamber 2 is formed in the side
portion of the chamber 2. The side opening 3 can be opened and
closed by a shutter 3a provided to the side opening 3.
[0025] As shown in FIG. 1, nozzles 30, 33, and 36 for supplying
each chemical solution and a rinse solution to the circumferential
edge of the wafer W held by the holding unit 10 are integrally
provided in parallel. More specifically, of the three nozzles 30,
33, and 36, the hydrofluoric-nitric acid supplying nozzle 30
located on the outermost side (the furthest side from the center of
the wafer W) in the diameter direction of the wafer W supplies
hydrofluoric-nitric acid to the circumferential edge of the wafer W
held by the holding unit 10. Of the three nozzles 30, 33, and 36,
the hydrofluoric acid supplying nozzle 33 located on the inner side
from the hydrofluoric-nitric acid supplying nozzle 30 in the
diameter direction of the wafer W supplies hydrofluoric acid to the
circumferential edge of the wafer W held by the holding unit 10. Of
the three nozzles 30, 33, and 36, the rinse solution supplying
nozzle 36 located on the innermost side (the nearest side from the
center of the wafer W) in the diameter direction of the wafer W
supplies a rinse solution, such as pure water, to the
circumferential edge of the wafer W held by the holding unit
10.
[0026] A hydrofluoric-nitric acid supplying source 32 is connected
via a hydrofluoric-nitric acid supplying pipe 31 to the
hydrofluoric-nitric acid supplying nozzle 30, thereby supplying the
hydrofluoric-nitric acid from the hydrofluoric-nitric acid
supplying source 32 via the hydrofluoric-nitric acid supplying pipe
31 to the hydrofluoric-nitric acid supplying nozzle 30. In
addition, a valve 31a which controls the presence or absence of
supplying and the supplying amount of the hydrofluoric-nitric acid
to the hydrofluoric-nitric acid supplying nozzle 30 is provided to
the hydrofluoric-nitric acid supplying pipe 31. The
hydrofluoric-nitric acid supplying nozzle 30, the
hydrofluoric-nitric acid supplying pipe 31, the valve 31a, and the
hydrofluoric-nitric acid supplying source 32 configure a
hydrofluoric-nitric acid supplying unit 52 which supplies the
hydrofluoric-nitric acid to the circumferential edge of the wafer W
held by the holding unit 10.
[0027] A hydrofluoric acid supplying source 35 is connected via a
hydrofluoric acid supplying pipe 34 to the hydrofluoric acid
supplying nozzle 33, thereby supplying the hydrofluoric acid from
the hydrofluoric acid supplying source 35 via the hydrofluoric acid
supplying pipe 34 to the hydrofluoric acid supplying nozzle 33. In
addition, a valve 34a which controls the presence or absence of
supplying and the supplying amount of the hydrofluoric acid to the
hydrofluoric acid supplying nozzle 33 is provided to the
hydrofluoric acid supplying pipe 34. The hydrofluoric acid
supplying nozzle 33, the hydrofluoric acid supplying pipe 34, the
valve 34a, and the hydrofluoric acid supplying source 35 configure
a hydrofluoric acid supplying unit 54 which supplies the
hydrofluoric acid to the circumferential edge of the wafer W held
by the holding unit 10.
[0028] A rinse solution supplying source 38 is connected via a
rinse solution supplying pipe 37 to the rinse solution supplying
nozzle 36, thereby supplying the rinse solution, such as pure
water, from the rinse solution supplying source 38 via the rinse
solution supplying pipe 37 to the rinse solution supplying nozzle
36. In addition, a valve 37a which controls the presence or absence
of supplying and the supplying amount of the rinse solution to the
rinse solution supplying nozzle 36 is provided to the rinse
solution supplying pipe 37. The rinse solution supplying nozzle 36,
the rinse solution supplying pipe 37, the valve 37a, and the rinse
solution supplying source 38 configure a rinse solution supplying
unit 56 which supplies the rinse solution, such as pure water, to
the circumferential edge of the wafer W held by the holding unit
10.
[0029] A nozzle driving mechanism 39 is provided on the three
nozzles 30, 33, and 36 integrally provided in parallel. The three
nozzles 30, 33, and 36 are integrally moved by the nozzle driving
mechanism 39.
[0030] As shown in FIG. 2, a control unit 50 which controls each
component of the substrate liquid-processing apparatus 1 is
provided in the substrate liquid-processing apparatus 1.
Specifically, the control unit 50 is connected to the holding unit
10, the rotational driving unit 20, the hydrofluoric-nitric acid
supplying unit 52, the hydrofluoric acid supplying unit 54, the
rinse solution supplying unit 56, and the nozzle driving mechanism
39. The control unit 50 transmits a control signal to each
component connected to the control unit 50 to control each
component. The specific contents of the control of each component
by the control unit 50 will be described below.
[0031] In this embodiment, the control unit 50 is connected to a
storage medium 60 which stores a control program for realizing each
process executed by the substrate liquid-processing apparatus 1 by
the control of the control unit 50, and a program (or a recipe) for
allowing each component of the substrate liquid-processing
apparatus 1 to execute a process according to the processing
conditions. The storage medium 60 can have a memory such as a ROM
or a RAM, a hard disk, a disc-like storage medium such as a CD-ROM
or a DVD-ROM, and other known storage medium. The arbitrary recipe
is called from the storage medium 60 so as to be executed by the
control unit 50, if necessary, so that a desired process in the
substrate liquid-processing apparatus 1 is performed under the
control of the control unit 50.
[0032] An operation (the processing method of the wafer W) of the
substrate liquid-processing apparatus 1 described above will be
described with reference to the flowchart shown in FIG. 3 and the
explanatory views shown in FIGS. 4A to 4C. It should be noted that
the operation of the substrate liquid-processing apparatus 1 is
performed by controlling each component of the substrate
liquid-processing apparatus 1 by the control unit 50 according to
the program (recipe) stored in the storage medium 60.
[0033] First, the wafer W is transferred from the outside of the
substrate liquid-processing apparatus 1 via the side opening 3 of
the chamber 2 into the chamber 2 by the transferring arm, not
shown. Specifically, the wafer W is placed on the holding unit 10
in the chamber 2 by the transferring arm (see STEP 1 of FIG. 3).
Here, a polysilicon film and a natural oxide film are provided in
the stacked state over the surface of the wafer W placed on the
holding unit 10 by the transferring arm (more specifically, the
polysilicon film is provided over the surface of the wafer W, and
the natural oxide film is stacked over the polysilicon film). It
should be noted that the polysilicon film is hydrophobic and the
natural oxide film is hydrophilic.
[0034] Next, the rotational shaft 12 is rotated about an axis
extending in the vertical direction by the rotational driving unit
20. As a result, the wafer W held by the holding unit 10 is
rotated. At this time, the rotational shaft 12 is rotated by
applying a driving force from the motor 22 via the driving belt 26
to the pulley 24.
[0035] In the state that the wafer W held by the holding unit 10 is
rotated, the hydrofluoric acid is supplied to the circumferential
edge of the wafer W by the hydrofluoric acid supplying unit 54.
Specifically, the hydrofluoric acid is supplied from the
hydrofluoric acid supplying source 35 via the hydrofluoric acid
supplying pipe 34 to the hydrofluoric acid supplying nozzle 33 to
discharge the hydrofluoric acid from the hydrofluoric acid
supplying nozzle 33 to the circumferential edge of the wafer W. At
this time, the wafer W is rotated at a high speed (e.g., 1000 rpm).
As a result, the natural oxide film provided along the
circumferential edge of the wafer W is removed by etching (see STEP
2 of FIG. 3). In this manner, the polysilicon film provided over
the wafer W is exposed. As the advantage of rotating the wafer W at
a high speed, the control of an etching width with respect to the
natural oxide film can be easily performed at high accuracy. The
hydrofluoric acid supplied to the surface of the wafer W is flowed
outward in the circumferential direction from the wafer W by a
centrifugal force of the rotation of the wafer W.
[0036] In the process for supplying the hydrofluoric acid to the
circumferential edge of the wafer W by the hydrofluoric acid
supplying unit 54, the region on the wafer W, to which the
hydrofluoric acid is supplied, is a region indicated by the
reference numeral 40 of FIG. 4A.
[0037] The concentration of the hydrofluoric acid supplied from the
hydrofluoric acid supplying unit 54 to the circumferential edge of
the wafer W is set to a concentration at which the natural oxide
film can be etched for a short time and the polysilicon film can be
exposed completely. Specifically, the concentration of the
hydrofluoric acid is set to a magnitude within the range of, e.g.,
1 to 50%. Therefore, when the hydrofluoric acid is supplied from
the hydrofluoric acid supplying unit 54 to the circumferential edge
of the wafer W, only the natural oxide film is removed without
removing the polysilicon film.
[0038] Next, in the state that the wafer W held by the holding unit
10 is rotated, the hydrofluoric-nitric acid is supplied to the
circumferential edge of the wafer W by the hydrofluoric-nitric acid
supplying unit 52. Specifically, the hydrofluoric-nitric acid is
supplied from the hydrofluoric-nitric acid supplying source 32 via
the hydrofluoric-nitric acid supplying pipe 31 to the
hydrofluoric-nitric acid supplying nozzle 30 to discharge the
hydrofluoric-nitric acid from the hydrofluoric-nitric acid
supplying nozzle 30 to the circumferential edge of the wafer W. As
a result, the polysilicon film provided along the circumferential
edge of the wafer W is removed by etching (see STEP 3 of FIG. 3).
The hydrofluoric-nitric acid supplied to the surface of the wafer W
is flowed outward in the circumferential direction from the wafer W
by the centrifugal force of the rotation of the wafer W.
[0039] It should be noted that the hydrofluoric-nitric acid
supplying nozzle 30 is arranged outward of the hydrofluoric acid
supplying nozzle 33 in the diameter direction of the wafer W held
by the holding unit 10. For this reason, when the
hydrofluoric-nitric acid is supplied to the circumferential edge of
the wafer W, the hydrofluoric-nitric acid is supplied to the
position outward in the diameter direction of the wafer W from the
position in which the hydrofluoric acid is supplied to the wafer W
when the hydrofluoric acid is supplied to the circumferential edge
of the wafer W. Therefore, when the hydrofluoric-nitric acid is
supplied to the circumferential edge of the wafer W, the
hydrofluoric-nitric acid is supplied into the region 40 along the
circumferential edge of the wafer W, to which the hydrofluoric acid
is supplied (see FIG. 4A), that is, into the hydrophobic plane of
the polysilicon film. FIG. 4B shows a region on the wafer W, to
which the hydrofluoric-nitric acid is supplied, indicated by the
reference numeral 41. As shown in FIG. 4B, the region 41 on the
wafer W, to which the hydrofluoric-nitric acid is supplied, is
included in the region 40 on the wafer W, to which the hydrofluoric
acid is supplied.
[0040] When the hydrofluoric-nitric acid is supplied to the
circumferential edge of the wafer W, the wafer W is rotated at a
rotation speed lower than that when the hydrofluoric acid is
supplied to the circumferential edge of the wafer W, as shown in
STEP 2 of FIG. 3. More specifically, the wafer W is rotated at
e.g., 300 rpm. As the wafer W is rotated at a low speed in this
manner, the time during which the polysilicon film provided along
the circumferential edge of the wafer W is contacted becomes
longer, whereby the occurrence of partial etching failure along the
circumferential edge of the wafer W can be prevented. For this
reason, the partial remaining of the polysilicon film along the
circumferential edge of the wafer W after the etching process is
performed can be prevented. In addition, as the advantage of
rotating the wafer W at a low speed, as the polysilicon film is
hydrophobic, the hydrofluoric-nitric acid cannot enter into the
center side of the wafer W at the time of the supply of the
hydrofluoric-nitric acid to the circumferential edge of the wafer W
and the hydrofluoric-nitric acid can be contacted for a long time
owing to a low speed. According to an experiment of the present
inventors, when the rotation speed of the wafer W is relatively
high (specifically, when the rotation speed of the wafer W is e.g.,
500 rpm or more), the time during which the hydrofluoric-nitric
acid is contacted with the polysilicon film provided along the
circumferential edge of the wafer W becomes shorter. Therefore, it
is found that etching failure partially occurs along the
circumferential edge of the wafer W and that the polysilicon film
partially remains along the circumferential edge of the wafer W
even after the etching process is performed.
[0041] Next, in the state that the wafer W held by the holding unit
10 is rotated, the rinse solution, such as pure water, is supplied
to the circumferential edge of the wafer W by the rinse solution
supplying unit 56. Specifically, the rinse solution is supplied
from the rinse solution supplying source 38 via the rinse solution
supplying pipe 37 to the rinse solution supplying nozzle 36 to
discharge the rinse solution from the rinse solution supplying
nozzle 36 to the circumferential edge of the wafer W. At this time,
the wafer W is rotated at a high speed (e.g., 1000 rpm). Therefore,
the rinse process of the circumferential edge of the wafer W (see
STEP 4 of FIG. 3) is performed. The rinse solution supplied to the
surface of the wafer W is flowed outward in the circumferential
direction from the wafer W by the centrifugal force of the rotation
of the wafer W.
[0042] It should be noted that the rinse solution supplying nozzle
36 is arranged inward of the hydrofluoric-nitric acid supplying
nozzle 30 and the hydrofluoric acid supplying nozzle 33 in the
diameter direction of the wafer W held by the holding unit 10.
Therefore, when the rinse solution is supplied to the
circumferential edge of the wafer W, the rinse solution is supplied
to the position inward in the diameter direction of the wafer W
from the position in which the hydrofluoric-nitric acid or the
hydrofluoric acid is supplied to the wafer W. As a result, all the
hydrofluoric-nitric acid and the hydrofluoric acid adhering to the
circumferential edge of the wafer W are washed away by the rinse
solution so that the rinse process of the wafer W can be reliably
performed. It should be noted that in the process for supplying the
rinse solution to the circumferential edge of the wafer W by the
rinse solution supplying unit 56 to perform the rinse process of
the wafer W, the region on the wafer W, to which the rinse solution
is supplied, is a region, indicated by the reference numeral 42 of
FIG. 4C.
[0043] Thereafter, the wafer W held by the holding unit 10 is
continued to be rotated at a high speed to perform the drying
process of the wafer W (see STEP 5 of FIG. 3).
[0044] Finally, the transferring arm is put into the chamber 2 via
the side opening 3 of the chamber 2, the wafer W is taken out from
the holding unit 10 by the transferring arm, and the taken-out
wafer W is transferred to the outside of the substrate
liquid-processing apparatus 1 (see STEP 6 of FIG. 3). In this
manner, a series of processes of the wafer W are completed.
[0045] As described above, according to the substrate
liquid-processing apparatus 1 and the substrate liquid-processing
method of this embodiment, the hydrofluoric acid is supplied to the
circumferential edge of the wafer W while the wafer W provided with
the polysilicon film is rotated, to remove the natural oxide film
provided along the circumferential edge of the wafer W by etching
so as to expose the polysilicon film (see STEP 2 of FIG. 3), and
then the hydrofluoric-nitric acid is supplied to the
circumferential edge of the wafer W while the wafer W from which
the polysilicon film is exposed is rotated, to remove the
polysilicon film by etching (see STEP 3 of FIG. 3). It should be
noted that the above operation is performed by controlling the
rotational driving unit 20, the hydrofluoric acid supplying unit
54, and the hydrofluoric-nitric acid supplying unit 52 by the
control unit 50 of the substrate liquid-processing apparatus 1.
According to the substrate liquid-processing apparatus 1 and the
substrate liquid-processing method, the hydrofluoric acid is first
supplied to the circumferential edge of the wafer W so that the
hydrophilic natural oxide film provided along the circumferential
edge of the wafer W can be removed by etching so as to expose the
hydrophobic polysilicon film along the circumferential edge of the
wafer W. Therefore, when hydrofluoric-nitric acid is supplied to
the circumferential edge of the wafer W, the erosion of the
hydrofluoric-nitric acid toward the center of the wafer W can be
prevented. As a result, the accuracy of the etching width can be
improved. In addition, when the erosion of the hydrofluoric-nitric
acid toward the center of the wafer W can be prevented, the wafer W
can be rotated at a low speed at the time of the supply of the
hydrofluoric-nitric acid to the circumferential edge of the wafer
W. Then, the occurrence of partial etching failure along the
circumferential edge of the wafer W can be prevented.
[0046] According to the substrate liquid-processing apparatus 1 and
the substrate liquid-processing method of this embodiment, when the
hydrofluoric-nitric acid is supplied to the circumferential edge of
the wafer W, the wafer W is rotated at a rotation speed lower than
that when the hydrofluoric acid is supplied to the circumferential
edge of the wafer W. Specifically, the rotation speed when the
hydrofluoric acid is supplied to the circumferential edge of the
wafer W is 500 rpm or more, more specifically, e.g., 1000 rpm,
whereas the rotation speed of the wafer W when the
hydrofluoric-nitric acid is supplied to the circumferential edge of
the wafer W is e.g., 300 rpm. As the wafer W is rotated at a low
speed when the hydrofluoric-nitric acid is supplied to the
circumferential edge of the wafer W in this manner, the time during
which the hydrofluoric-nitric acid is contacted with the
polysilicon film provided along the circumferential edge of the
wafer W can be longer. Therefore, the occurrence of partial etching
failure along the circumferential edge of the wafer W can be
prevented. For this reason, the partial remaining of the
polysilicon film along the circumferential edge of the wafer W
after the etching process is performed can be prevented.
[0047] In addition, according to the substrate liquid-processing
apparatus 1 and the substrate liquid-processing method of this
embodiment, when the hydrofluoric-nitric acid is supplied to the
circumferential edge of the wafer W, the hydrofluoric-nitric acid
is supplied to the region along the circumferential edge of the
wafer W, to which the hydrofluoric acid is already supplied (see
FIGS. 4A and 4B). More specifically, the hydrofluoric-nitric acid
supplying nozzle 30 of the hydrofluoric-nitric acid supplying unit
52 is arranged outward in the diameter direction of the wafer W
held by the holding unit 10 from the hydrofluoric acid supplying
nozzle 33 of the hydrofluoric acid supplying unit 54. For this
reason, when the hydrofluoric-nitric acid is supplied to the
circumferential edge of the wafer W, the hydrofluoric-nitric acid
is supplied to the position outward in the diameter direction of
the wafer W from the position in which the hydrofluoric acid is
supplied to the wafer W (the position in which the hydrofluoric
acid is supplied from the hydrofluoric acid supplying nozzle 33 to
the wafer W) when the hydrofluoric acid is supplied to the
circumferential edge of the wafer W. As a result, the
hydrofluoric-nitric acid can be reliably supplied to the position
on the surface of the wafer W, in which the natural oxide film is
removed to expose the polysilicon film. In addition, at this time,
the hydrofluoric-nitric acid is reliably supplied into the
hydrophobic plane on the surface of the wafer W. Therefore, the
erosion of the hydrofluoric-nitric acid toward the center of the
wafer W can be prevented more reliably.
[0048] Further, the concentration of the hydrofluoric acid supplied
to the circumferential edge of the wafer W is set to a
concentration at which the natural oxide film can be etched for a
short time and the polysilicon film can be completely exposed. For
this reason, when the hydrofluoric acid is supplied to the
circumferential edge of the wafer W, only the natural oxide film
provided over the surface of the wafer W can be removed. Then, the
surface of the wafer W can be reliably brought into the hydrophobic
state.
[0049] The substrate liquid-processing apparatus and the substrate
liquid-processing method of this embodiment are not limited to the
above embodiment and various changes can be added. For instance,
the hydrofluoric-nitric acid supplying nozzle 30, the hydrofluoric
acid supplying nozzle 33, and the rinse solution supplying nozzle
36 are not required to be integrally provided. In other words, the
nozzles 30, 33, and 36 may also be driven independently.
* * * * *