U.S. patent application number 14/179131 was filed with the patent office on 2014-08-21 for substrate processing apparatus.
This patent application is currently assigned to DAINIPPON SCREEN MFG. CO., LTD.. The applicant listed for this patent is DAINIPPON SCREEN MFG. CO., LTD.. Invention is credited to NAOKI FUJIWARA, TAIKI HINODE, TAKASHI OTA.
Application Number | 20140231013 14/179131 |
Document ID | / |
Family ID | 51310756 |
Filed Date | 2014-08-21 |
United States Patent
Application |
20140231013 |
Kind Code |
A1 |
HINODE; TAIKI ; et
al. |
August 21, 2014 |
SUBSTRATE PROCESSING APPARATUS
Abstract
A substrate processing apparatus includes a phosphoric acid
supply device for supplying phosphoric acid aqueous solution onto
the upper surface of a substrate held on a spin chuck, a heater for
emitting heat toward a portion of the upper surface of the
substrate with the phosphoric acid aqueous solution being held on
the substrate, a heater moving device for moving the heater to move
a position heated by the heater within the upper surface of the
substrate, a water nozzle for discharging water therethrough toward
a portion of the upper surface of the substrate with the phosphoric
acid aqueous solution being held on the substrate and a water
nozzle moving device for moving the water nozzle to move the water
landing position within the upper surface of the substrate.
Inventors: |
HINODE; TAIKI; (KYOTO-SHI,
JP) ; OTA; TAKASHI; (KYOTO-SHI, JP) ;
FUJIWARA; NAOKI; (KYOTO-SHI, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DAINIPPON SCREEN MFG. CO., LTD. |
KYOTO-SHI |
|
JP |
|
|
Assignee: |
DAINIPPON SCREEN MFG. CO.,
LTD.
KYOTO-SHI
JP
|
Family ID: |
51310756 |
Appl. No.: |
14/179131 |
Filed: |
February 12, 2014 |
Current U.S.
Class: |
156/345.23 ;
156/345.11 |
Current CPC
Class: |
H01L 21/67051 20130101;
H01L 21/31111 20130101; C09K 13/04 20130101; H01L 21/6708 20130101;
H01L 21/67109 20130101 |
Class at
Publication: |
156/345.23 ;
156/345.11 |
International
Class: |
C09K 13/04 20060101
C09K013/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 15, 2013 |
JP |
2013-028125 |
Claims
1. A substrate processing apparatus comprising: a substrate holding
device for holding a substrate horizontally; a phosphoric acid
supply device for supplying phosphoric acid aqueous solution onto
an upper surface of the substrate held on the substrate holding
device to form a liquid film of phosphoric acid aqueous solution
covering an entire upper surface of the substrate; a heater for
heating the liquid film of phosphoric acid aqueous solution from an
upper surface side of the substrate; a heater moving device for
moving the heater to move a position heated by the heater along the
upper surface of the substrate; a water nozzle for discharging
water therethrough toward the liquid film of phosphoric acid
aqueous solution to cause the water to land on the liquid film; and
a water nozzle moving device for moving the water nozzle to move a
water landing position along the upper surface of the
substrate.
2. The substrate processing apparatus according to claim 1, further
comprising a water flow rate control valve for supplying water
therethrough to the water nozzle at a flow rate at which the liquid
film of phosphoric acid aqueous solution is maintained in a puddle
shape on the substrate.
3. The substrate processing apparatus according to claim 1, wherein
the heater moving device is arranged to move the heater such that a
region adjacent to the water landing position is heated.
4. The substrate processing apparatus according to claim 3, wherein
the substrate holding device includes a spin motor for rotating the
substrate about a vertical line passing through a central portion
of the upper surface of the substrate, and wherein the heater
moving device is arranged to move the heater such that a region
downstream from the water landing position in a rotation direction
of the substrate is heated.
5. The substrate processing apparatus according to claim 1, wherein
the substrate holding device includes a spin motor for rotating the
substrate about a vertical line passing through a central portion
of the upper surface of the substrate, the substrate processing
apparatus further comprising a control device for controlling the
substrate holding device and the water nozzle moving device to move
the water landing position between the central portion of the upper
surface of the substrate and a peripheral portion of the upper
surface of the substrate while rotating the substrate, and wherein
the control device is arranged to, when a rotation speed of the
substrate is lower than a predetermined speed, move the water
landing position between the central portion of the upper surface
of the substrate and the peripheral portion of the upper surface of
the substrate at a constant speed, while the control device is
arranged to, when the rotation speed of the substrate is equal to
or higher than the predetermined speed, reduce a moving speed of
the water landing position as the water landing position comes
closer to the central portion of the upper surface of the substrate
or increase the moving speed of the water landing position as the
water landing position moves away from the central portion of the
upper surface of the substrate.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a substrate processing
apparatus for processing a substrate. Substrates to be processed
include, for example, semiconductor wafers, liquid crystal display
device substrates, plasma display substrates, FED (Field Emission
Display) substrates, optical disk substrates, magnetic disk
substrates, magneto-optical disk substrates, photomask substrates,
ceramic substrates, and photovoltaic cell substrates.
[0003] 2. Description of Related Art
[0004] In a process of manufacturing semiconductor devices and
liquid crystal display devices, etching treatment is performed as
required in which a high-temperature phosphoric acid aqueous
solution is supplied as an etchant onto the front surface of a
substrate with a silicon nitride film and a silicon oxide film
formed thereon to selectively etch the silicon nitride film.
[0005] US 2012/074102 A1 discloses a single substrate processing
type substrate processing apparatus in which phosphoric acid
aqueous solution of close to the boiling point is supplied onto a
substrate held on a spin chuck. In this substrate processing
apparatus, a high-temperature phosphoric acid aqueous solution of
100.degree. C. or higher is supplied onto a substrate.
SUMMARY OF THE INVENTION
[0006] Moisture evaporation from the phosphoric acid aqueous
solution supplied onto the substrate progresses gradually. During
this time, the phosphoric acid aqueous solution undergoes a
reaction of 2H.sub.3PO.sub.4--, H.sub.4P.sub.2O.sub.7+H.sub.2O,
that is, pyrophosphoric acid H.sub.4P.sub.2O.sub.7 is generated
from phosphoric acid H.sub.3PO.sub.4. Pyrophosphoric acid can etch
the silicon oxide film. It is primarily desirable to etch only the
silicon nitride film and leave unetched as large an area of the
silicon oxide film as possible. Increasing the amount of etching of
the silicon nitride film while suppressing the amount of etching of
the silicon oxide film can result in a higher value of the etching
selectivity ((etching amount of the silicon nitride film)/(etching
amount of the silicon oxide film)). However, pyrophosphoric acid,
if generated as mentioned above, can etch a portion of the silicon
oxide film that is primarily desired to be left unetched, resulting
in a reduction in the etching selectivity.
[0007] A preferred embodiment of the present invention provides a
substrate processing apparatus including a substrate holding device
for holding a substrate horizontally, a phosphoric acid supply
device for supplying phosphoric acid aqueous solution onto the
upper surface of the substrate held on the substrate holding device
to form a liquid film of phosphoric acid aqueous solution covering
the entire upper surface of the substrate, a heater for heating the
liquid film of phosphoric acid aqueous solution from the upper
surface side of the substrate, a heater moving device for moving
the heater to move a position heated by the heater along the upper
surface of the substrate, a water nozzle for discharging water
therethrough toward the liquid film of phosphoric acid aqueous
solution to cause the water to reach the liquid film and a water
nozzle moving device for moving the water nozzle to move the water
landing position along the upper surface of the substrate.
[0008] In accordance with the arrangement above, the phosphoric
acid supply device supplies phosphoric acid aqueous solution as an
etchant onto the upper surface of the substrate horizontally held
on the substrate holding device. The heater then heats the liquid
film of phosphoric acid aqueous solution from the upper surface
side of the substrate, and the heater moving device moves a
position heated by the heater along the upper surface of the
substrate. This allows the liquid film of phosphoric acid aqueous
solution to be heated without unevenness. The phosphoric acid
aqueous solution on the substrate is thus heated and thereby the
etching rate is increased.
[0009] The substrate processing apparatus also includes the water
nozzle for discharging water therethrough toward the liquid film of
phosphoric acid aqueous solution to cause the water to reach the
liquid film and the water nozzle moving device for moving the water
nozzle to move the water landing position along the upper surface
of the substrate, whereby water is supplied toward the entire upper
surface of the substrate.
[0010] The water nozzle discharges water therethrough toward the
liquid film of phosphoric acid aqueous solution. The water nozzle
moving device moves the water nozzle to move the water landing
position with respect to the liquid film within the upper surface
of the substrate. This allows the liquid film of phosphoric acid
aqueous solution to be supplied with water without unevenness.
Accordingly, pyrophosphoric acid (H.sub.4P.sub.2O.sub.7) in the
phosphoric acid aqueous solution decreases through a reaction of
H.sub.4P.sub.2O.sub.7+H.sub.2O.fwdarw.2H.sub.3PO.sub.4. This can
suppress the reduction in the etching selectivity.
[0011] In a preferred embodiment of the present invention, the
substrate processing apparatus may further include a water flow
rate control valve for supplying water therethrough to the water
nozzle at a flow rate at which the liquid film of phosphoric acid
aqueous solution is maintained in a puddle shape on the
substrate.
[0012] In accordance with the arrangement above, a puddle-shaped
liquid film of phosphoric acid aqueous solution covering the entire
upper surface of the substrate is formed. This causes the entire
upper surface of the substrate to be supplied with phosphoric acid
aqueous solution and etched.
[0013] Further, water is supplied onto the liquid film of
phosphoric acid aqueous solution with the removal of phosphoric
acid aqueous solution from the substrate being stopped. This can
prevent the phosphoric acid aqueous solution, which has sufficient
activity, from being removed from the substrate. This allows the
phosphoric acid aqueous solution to be used efficiently. Further,
since the amount of water supplied to the phosphoric acid aqueous
solution on the substrate is accordingly small, the changes in the
concentration and temperature of the phosphoric acid aqueous
solution can be suppressed. It is therefore possible to suppress
the fluctuation in the etching rate while suppressing the reduction
in the etching selectivity.
[0014] In a preferred embodiment of the present invention, the
heater moving device may be arranged to move the heater such that a
region adjacent to the water landing position with respect to the
upper surface of the substrate is heated.
[0015] In accordance with the arrangement above, the vicinity of
the water landing position is heated by the heater. It is therefore
possible to immediately compensate for the change in the
temperature of the phosphoric acid aqueous solution due to the
water supply. This can suppress the reduction in the in-plane
etching rate uniformity.
[0016] In a preferred embodiment of the present invention, the
substrate holding device may include a spin motor for rotating the
substrate about a vertical line passing through a central portion
of the upper surface of the substrate. The heater moving device may
be arranged to move the heater such that a region downstream from
the water landing position in the rotation direction of the
substrate is heated.
[0017] In accordance with the arrangement above, the heater can
heat the liquid film portion of phosphoric acid aqueous solution
supplied with water immediately even if the substrate may be
rotated. It is therefore possible to immediately compensate for the
change in the temperature of the phosphoric acid aqueous solution
due to the water supply. This can suppress the reduction in the
in-planar etching rate uniformity.
[0018] In a preferred embodiment of the present invention, the
substrate holding device may include a spin motor for rotating the
substrate about a vertical line passing through a central portion
of the upper surface of the substrate. The substrate processing
apparatus may further include a control device for controlling the
substrate holding device and the water nozzle moving device to move
the water landing position between the central portion of the upper
surface of the substrate and a peripheral portion of the upper
surface of the substrate while rotating the substrate. The control
device may be arranged to, when the rotation speed of the substrate
is lower than a predetermined speed, move the water landing
position between the central portion of the upper surface of the
substrate and the peripheral portion of the upper surface of the
substrate at a constant speed. The control device may be arranged
to, when the rotation speed of the substrate is equal to or higher
than the predetermined speed, reduce the moving speed of the water
landing position as the water landing position comes closer to the
central portion of the upper surface of the substrate or increase
the moving speed of the water landing position as the water landing
position moves away from the central portion of the upper surface
of the substrate.
[0019] In accordance with the arrangement above, when the rotation
speed of the substrate is lower than the predetermined speed, the
control device moves the water landing position between the central
portion of the upper surface of the substrate and the peripheral
portion of the upper surface of the substrate at a constant speed.
On the other hand, when the rotation speed of the substrate is
equal to or higher than the predetermined speed, the control device
reduces the moving speed of the water landing position as the water
landing position comes closer to the central portion of the upper
surface of the substrate. Accordingly, when the rotation speed of
the substrate is equal to or higher than the predetermined speed,
the central portion of the upper surface of the substrate is
supplied with water at an amount larger than the peripheral portion
of the upper surface of the substrate.
[0020] The present inventors have confirmed that when the substrate
rotates at a high speed, the amount of etching is larger in the
central portion of the upper surface of the substrate than in the
peripheral portion of the upper surface of the substrate. The
difference in the amount of etching can be for the reason that the
concentration of phosphoric acid aqueous solution is higher in the
central portion of the upper surface of the substrate than in the
peripheral portion of the upper surface of the substrate. Hence,
the control device is arranged to supply water onto the central
portion of the upper surface of the substrate at an amount larger
than onto the peripheral portion of the upper surface of the
substrate to thereby reduce the concentration of phosphoric acid
aqueous solution in the central portion of the upper surface of the
substrate. The control device can thus be arranged to reduce the
amount of etching in the central portion of the upper surface of
the substrate. This can increase the etching uniformity.
[0021] The foregoing and other objects, features and advantages of
the present invention will become more apparent from the
description of preferred embodiments provided below with reference
to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a horizontal schematic view of the interior of a
processing unit included in a substrate processing apparatus
according to a first preferred embodiment of the present
invention.
[0023] FIG. 2 is a horizontal schematic view showing a spin chuck,
an infrared heater and a pure water nozzle.
[0024] FIG. 3 is a schematic plan view showing the spin chuck, the
infrared heater and the pure water nozzle.
[0025] FIG. 4 is a process flow chart illustrating an example of
substrate processing performed by the processing unit.
[0026] FIG. 5A is a schematic view showing a substrate during a
phosphoric acid supply step.
[0027] FIG. 5B is a schematic view showing the substrate during a
puddle step.
[0028] FIG. 5C is a schematic view showing the substrate during the
puddle step, a heating step and a pure water supply step.
[0029] FIG. 6 is a graph showing an example of the relationship
between the radial distance from the center of the substrate to the
pure water landing position and the moving speed of the pure water
landing position as well as the amount of pure water supply.
[0030] FIG. 7 is a graph showing another example of the
relationship between the radial distance from the center of the
substrate to the pure water landing position and the moving speed
of the pure water landing position as well as the amount of pure
water supply.
[0031] FIG. 8 is a graph showing the relationship between the
temperature of phosphoric acid aqueous solution supplied onto the
substrate and the etching rate as well as the etching
selectivity.
[0032] FIG. 9 is a horizontal schematic view showing an infrared
heater and a spin chuck according to a second preferred embodiment
of the present invention.
[0033] FIG. 10 is a vertical cross-sectional view of the infrared
heater according to the second preferred embodiment of the present
invention.
[0034] FIG. 11 is a horizontal schematic view showing a heating
nozzle and a spin chuck according to a third preferred embodiment
of the present invention.
[0035] FIG. 12 is a schematic view showing the vertical
cross-section and the bottom surface of an infrared heater and a
pure water nozzle according to a fourth preferred embodiment of the
present invention.
[0036] FIG. 13 is a schematic view of a pure water supply device
according to a fifth preferred embodiment of the present
invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
First Preferred Embodiment
[0037] FIG. 1 is a horizontal schematic view of the interior of a
processing unit 2 included in a substrate processing apparatus 1
according to a first preferred embodiment of the present invention.
FIG. 2 is a horizontal schematic view showing a spin chuck 5, an
infrared heater 31 and a pure water nozzle 38. FIG. 3 is a
schematic plan view showing the spin chuck 5, the infrared heater
31 and the pure water nozzle 38.
[0038] The substrate processing apparatus 1 is a single substrate
processing type in which a disk-like substrate W such as a
semiconductor wafer is processed one by one. The substrate
processing apparatus 1 includes multiple processing units 2 (only
one processing unit 2 is shown in FIG. 1) for processing the
substrate W with processing fluid such as processing liquid and/or
processing gas and a control device 3 for controlling the operation
of devices and the opening/closing of valves included in the
substrate processing apparatus 1. It is noted that the substrate
processing apparatus 1 may include a single processing unit 2.
[0039] The processing unit 2 includes a box-shaped chamber 4 having
an interior space, the spin chuck 5 for holding the substrate W
horizontally within the chamber 4 and rotating the substrate W
about a vertical rotation axis A1 passing through the center of the
substrate W, processing liquid supply devices (phosphoric acid
supply device 6, SC1 supply device 7, rinse liquid supply device 8
and pure water supply device 36) for supplying processing liquid
onto the substrate W, a cylindrical cup 9 surrounding the spin
chuck 5, and a heating device 10 for heating the substrate W.
[0040] As shown in FIG. 1, the chamber 4 includes a box-shaped
partition wall 11 housing the spin chuck 5 and other components
therein, an FFU 12 (fan filter unit 12) serving as a blower unit
for feeding clean air (filtered air) into the partition wall 11
through an upper portion of the partition wall 11 and an exhaust
duct 13 for discharging gas within the chamber 4 through a lower
portion of the partition wall 11. The FFU 12 is disposed over the
partition wall 11. The FFU 12 feeds clean air downward into the
chamber 4 through the ceiling of the partition wall 11. The exhaust
duct 13 is connected to a bottom portion of the cup 9 and guides
gas within the chamber 4 toward an exhaust installation provided in
the factory in which the substrate processing apparatus 1 is
installed. Accordingly, a downflow (downward flow) flowing
downwardly within the chamber 4 is formed by the FFU 12 and the
exhaust duct 13. The substrate W is processed with such a downflow
being formed within the chamber 4.
[0041] As shown in FIG. 1, the spin chuck 5 includes a horizontally
held disk-like spin base 14, multiple chuck pins 15 for holding the
substrate W horizontally over the spin base 14, a rotary shaft 16
extending downward from a central portion of the spin base 14 and a
spin motor 17 serving as a substrate rotating device for rotating
the rotary shaft 16 to rotate the substrate W and the spin base 14
about the rotation axis A1. The spin chuck 5 may be not only of a
clamping type in which the multiple chuck pins 15 are brought into
contact with the circumferential end surface of the substrate W,
but also of a vacuum type in which the rear surface (lower surface)
of the substrate W, on which no device is to be formed, is vacuumed
onto the upper surface of the spin base 14 so that the substrate W
is horizontally held.
[0042] As shown in FIG. 1, the cup 9 is disposed on an outer side
(in the direction away from the rotation axis A1) further than the
substrate W held on the spin chuck 5. The cup 9 surrounds the spin
base 14. Processing liquid, when supplied onto the substrate W with
the spin chuck 5 rotating the substrate W, is diverted from the
substrate W. When the processing liquid is supplied onto the
substrate W, an upper end portion 9a of the cup 9 opened upward is
disposed at a position higher than that of the spin base 14.
Accordingly, the processing liquid, such as chemical liquid and/or
rinse liquid, diverted from the substrate W is received by the cup
9. The processing liquid received by the cup 9 is then sent to a
collect apparatus or a waste liquid disposal apparatus not
shown.
[0043] As shown in FIG. 1, the phosphoric acid supply device 6
includes a phosphoric acid nozzle 18 for discharging phosphoric
acid aqueous solution therethrough toward the substrate W held on
the spin chuck 5, a phosphoric acid pipe 19 for supplying
phosphoric acid aqueous solution therethrough to the phosphoric
acid nozzle 18, a phosphoric acid valve 20 for switching between
start and stop of the supply of phosphoric acid aqueous solution
from the phosphoric acid pipe 19 to the phosphoric acid nozzle 18
and a phosphoric acid temperature control device 21 for bringing
the temperature of phosphoric acid aqueous solution to be supplied
to the phosphoric acid nozzle 18 up to a temperature higher than
the room temperature (a predetermined temperature within the range
from 20.degree. C. to 30.degree. C.).
[0044] When the phosphoric acid valve 20 is opened, phosphoric acid
aqueous solution, the temperature of which is controlled through
the phosphoric acid temperature control device 21, is supplied
through the phosphoric acid pipe 19 to the phosphoric acid nozzle
18 and discharged through the phosphoric acid nozzle 18. The
phosphoric acid temperature control device 21 maintains the
temperature of phosphoric acid aqueous solution at a constant
temperature within the range from 80.degree. C. to 215.degree. C.,
for example. The phosphoric acid temperature control device 21 may
control the temperature of phosphoric acid aqueous solution to the
boiling point or lower at the current concentration. The phosphoric
acid aqueous solution consists primarily of phosphoric acid, the
concentration thereof being, for example, 50% to 100% and
preferably around 800.
[0045] As shown in FIG. 1, the phosphoric acid supply device 6
further includes a nozzle arm 22 with the phosphoric acid nozzle 18
attached to the tip portion thereof and a phosphoric acid nozzle
moving device 23 for swinging the nozzle arm 22 about a swing axis
A2 vertically extending around the spin chuck 5 and moving the
nozzle arm 22 vertically upward and downward along the swing axis
A2 to move the phosphoric acid nozzle 18 horizontally and
vertically. The phosphoric acid nozzle moving device 23 moves the
phosphoric acid nozzle 18 horizontally between a processing
position where phosphoric acid aqueous solution discharged through
the phosphoric acid nozzle 18 is supplied onto the upper surface of
the substrate W and a retracted position where the phosphoric acid
nozzle 18 is retracted around the substrate W in a plan view.
[0046] As shown in FIG. 1, the SC1 supply device 7 includes an SC1
nozzle 24 for discharging SC1 (mixture liquid containing NH.sub.4OH
and H.sub.2O.sub.2) therethrough toward the substrate W held on the
spin chuck 5, an SC1 pipe 25 for supplying SC1 therethrough to the
SC1 nozzle 24, an SC1 valve 26 for switching between start and stop
of the supply of SC1 from the SC1 pipe 25 to the SC1 nozzle 24 and
an SC1 nozzle moving device 27 for moving the SC1 nozzle 24
horizontally and vertically. When the SC1 valve 26 is opened, SC1
supplied through the SC1 pipe 25 to the SC1 nozzle 24 is discharged
through the SC1 nozzle 24. The SC1 nozzle moving device 27 moves
the SC1 nozzle 24 horizontally between a processing position where
SC1 discharged through the SC1 nozzle 24 is supplied onto the upper
surface of the substrate W and a retracted position where the SC1
nozzle 24 is retracted around the substrate W in a plan view.
[0047] As shown in FIG. 1, the rinse liquid supply device 8
includes a rinse liquid nozzle 28 for discharging rinse liquid
therethrough toward the substrate W held on the spin chuck 5, a
rinse liquid pipe 29 for supplying rinse liquid therethrough to the
rinse liquid nozzle 28 and a rinse liquid valve 30 for switching
between start and stop of the supply of rinse liquid from the rinse
liquid pipe 29 to the rinse liquid nozzle 28. The rinse liquid
nozzle 28 is a fixed nozzle arranged to discharge rinse liquid
therethrough with the discharge port of the rinse liquid nozzle 28
kept still. The rinse liquid supply device 8 may include a rinse
liquid nozzle moving device for moving the rinse liquid nozzle 28
to move the position at which rinse liquid lands with respect to
the upper surface of the substrate W.
[0048] When the rinse liquidvalve 30 is opened, rinse liquid
supplied through the rinse liquid pipe 29 to the rinse liquid
nozzle 28 is discharged through the rinse liquid nozzle 28 toward a
central portion of the upper surface of the substrate W. The rinse
liquid is, for example, pure water (deionized water). The rinse
liquid is not limited to pure water, but may be carbonated water,
electrolyzed ionic water, hydrogen water, ozone water, IPA
(isopropyl alcohol), or hydrochloric acid water of a dilute
concentration (e.g. about 10 to 100 ppm).
[0049] As shown in FIG. 1, the heating device 10 includes a radiant
heating device for radiationally heating the substrate W. The
radiant heating device includes the infrared heater 31 for
irradiating the substrate W with infrared light, a heater arm 32
with the infrared heater 31 attached to the tip portion thereof and
a heater moving device 33 for moving the heater arm 32.
[0050] As shown in FIG. 2, the infrared heater 31 includes an
infrared lamp 34 for emitting infrared light and a lamp housing 35
housing the infrared lamp 34 therein. The infrared lamp 34 is
disposed within the lamp housing 35. As shown in FIG. 3, the lamp
housing 35 is smaller than the substrate W in a plan view.
Accordingly, the infrared lamp 34 disposed within the lamp housing
35 is also smaller than the substrate W in a plan view. The
infrared lamp 34 and the lamp housing 35 are attached to the heater
arm. 32. Accordingly, the infrared lamp 34 and the lamp housing 35
move together with the heater arm 32.
[0051] The infrared lamp 34 includes a filament and a quartz tube
housing the filament therein. The infrared lamp 34 (e.g. halogen
lamp) in the heating device 10 may be a carbon heater or another
type of heating element. At least a portion of the lamp housing 35
is made of a material having optical transparency and heat
resistance, such as quartz.
[0052] When the infrared lamp 34 emits light, light containing
infrared light is emitted from the infrared lamp 34. The light
containing infrared light transmits through the lamp housing 35 to
be emitted from the outer surface of the lamp housing 35 or heats
the lamp housing 35 to emit radiant light from the outer surface of
the lamp housing 35. The substrate W and a liquid film of
phosphoric acid aqueous solution held on the upper surface of the
substrate W are heated by the transmitted light and radiant light
from the outer surface of the lamp housing 35. Although transmitted
or radiant light containing infrared light is thus emitted from the
outer surface of the lamp housing 35, the infrared lamp 34 will
hereinafter be described focusing on infrared light transmitting
through the outer surface of the lamp housing 35.
[0053] As shown in FIG. 2, the lamp housing 35 has a bottom wall
parallel to the upper surface of the substrate W. The infrared lamp
34 is disposed over the bottom wall. The lower surface of the
bottom wall includes a flat substrate opposing surface parallel to
the upper surface of the substrate W. With the infrared heater 31
being disposed over the substrate W, the substrate opposing surface
of the lamp housing 35 is vertically opposed to the upper surface
of the substrate W with a space therebetween. Infrared light, when
emitted from the infrared lamp 34 in this state, transmits through
the substrate opposing surface of the lamp housing 35 to irradiate
the upper surface of the substrate W. The substrate opposing
surface has, for example, a circular shape with a diameter smaller
than the radius of the substrate W. The substrate opposing surface
is not limited to having a circular shape, but may have a
rectangular shape with a longitudinal length equal to or greater
than the radius of the substrate W or a shape other than circular
or rectangular.
[0054] As shown in FIG. 1, the heater moving device 33 holds the
infrared heater 31 at a predetermined height. The heater moving
device 33 moves the infrared heater 31 vertically. Further, the
heater moving device 33 swings the heater arm 32 about a swing axis
A3 vertically extending around the spin chuck 5 to move the
infrared heater 31 horizontally. This causes a heated region
irradiated and heated with light such as infrared light (a portion
within the upper surface of the substrate W) to move within the
upper surface of the substrate W. As shown in FIG. 2, the heater
moving device 33 moves the tip portion of the heater arm 32
horizontally along an arc-like trajectory X1 passing through the
center of the substrate W in a plan view. Accordingly, the infrared
heater 31 moves within a horizontal plane including the space over
the spin chuck 5.
[0055] The heated region within the upper surface of the substrate
W is irradiated with infrared light from the infrared heater 31.
With the infrared heater 31 emitting light, the control device 3
controls the heater moving device 33 to swing the infrared heater
31 about the swing axis A3 while controlling the spin chuck 5 to
rotate the substrate W. This causes the heated region as a result
of the infrared heater 31 to scan the upper surface of the
substrate W. As a result, light such as infrared light is absorbed
by at least one of the upper surface of the substrate W and the
processing liquid film held on the upper surface of the substrate W
and thus radiant heat is transferred from the infrared lamp 34 to
the substrate W. When the infrared lamp 34 thus emits light with
liquid such as processing liquid being held on the substrate W, the
temperature of the substrate W rises and accordingly the
temperature of the liquid on the substrate W also rises.
Alternatively, the liquid on the substrate W itself is heated to
undergo a temperature rise.
[0056] As shown in FIG. 1, the processing unit 2 includes the pure
water supply device 36 for discharging pure water toward the
substrate W. The pure water supply device 36 includes the pure
water nozzle 38 for discharging pure water through a pure water
discharge port 37 toward the substrate W, a pure water pipe 39 for
supplying pure water therethrough to the pure water nozzle 38, a
pure water valve 40 for switching between start and stop of the
supply of pure water from the pure water pipe 39 to the pure water
nozzle 38, and a pure water flow rate control valve 41 for
controlling the flow rate of pure water supplied from the pure
water pipe 39 to the pure water nozzle 38.
[0057] The pure water nozzle 38 includes single pure water
discharge port 37 for intermittently discharging pure water
therethrough and preferably pure water droplets one by one. The
pure water nozzle 38 may include multiple pure water discharge
ports 37. Pure water drops vertically downward from the pure water
discharge port 37 serving as a droplet discharge port. Therefore,
when the pure water discharge port 37 is vertically opposed to the
upper surface of the substrate W, pure water droplets drop
vertically downward to the upper surface of the substrate W.
Switching between start and stop of the discharge of droplets is
performed by the pure water valve 40 and the size of the droplets
is adjusted with the degree of opening of the pure water flow rate
control valve 41.
[0058] As shown in FIG. 1, the pure water nozzle 38 is attached to
the heater arm 32. Accordingly, the pure water nozzle 38 moves
horizontally and vertically together with the infrared heater 31.
The infrared heater 31 is attached to the heater arm 32 closer to
the base of the heater arm 32 than the pure water nozzle 38. This
results in the horizontal distance from the swing axis A3 to the
pure water nozzle 38 is longer than the horizontal distance from
the swing axis A3 to the infrared heater 31.
[0059] As shown in FIG. 3, when the heater arm 32 is swung by the
heater moving device 33, pure water from the pure water nozzle 38
lands on the upper surface of the substrate W along the arc-like
trajectory X1 passing through the center of the substrate W. On the
other hand, the infrared heater 31 moves over the upper surface of
the substrate W with a swing radius smaller than the trajectory X1.
The heater moving device 33 moves not only the infrared heater 31
but also the pure water nozzle 38 along the upper surface of the
substrate W. This allows the heater moving device 33 to serve also
as a pure water supply position moving device.
[0060] As shown in FIG. 3, the control device 3 controls the spin
chuck 5 to rotate the substrate W in a certain rotation direction
Dr.
[0061] During a heating step and a pure water supply step (step S4
in FIG. 4) to be described hereinafter, the control device 3 makes
the heater arm 32 swing back and forth between the central portion
of the upper surface of the substrate W (the position shown in FIG.
3) and the peripheral portion of the upper surface of the substrate
W such that the position at which pure water discharged through the
pure water nozzle 38 lands moves back and forth within the range
indicated by the arrow in FIG. 3. This allows pure water discharged
through the pure water nozzle 38 to land on a region of phosphoric
acid aqueous solution upstream from the region irradiated with
infrared light by the infrared heater 31 with respect to the
rotation direction Dr of the substrate W.
[0062] Pure water droplets dropping on the upper surface of the
rotating substrate W move in the rotation direction Dr of the
substrate W. That is, the pure water droplets move downstream in
the rotation direction Dr of the substrate W. The infrared heater
31 irradiates and heats with light such as infrared light a region
downstream from the pure water landing position. Accordingly, when
pure water droplets drop on a partial region within the upper
surface of the substrate W with the substrate W rotating and the
infrared heater 31 emitting light such as infrared light, the
region rapidly moves to the heated region to be heated. As a
result, even if droplets with a temperature lower than that of the
substrate W may be supplied onto the substrate W, the temperature
of the substrate W is approximated to the original temperature (the
temperature before the droplets are supplied).
[0063] FIG. 4 is a process flow chart illustrating an example of
processing of the substrate W performed by the processing unit 2.
FIGS. 5A, 5B and 5C are schematic views showing the substrate W
being processed. Reference will be made to FIG. 1 below. Reference
to FIGS. 4, 5A, 5B and 5C will be made appropriately.
[0064] Hereinafter will be described selective etching in which
phosphoric acid aqueous solution is supplied onto a surface of a
substrate W (silicon wafer) with an LP-SiN (Low Pressure-Silicon
Nitride) thin film as an example silicon nitride film and an
LP-TEOS (Low Pressure-Tetraethyl Orthosilicate) thin film as an
example silicon oxide film formed superficially thereon to
selectively etch the LP-SiN thin film. The silicon oxide film is
not limited to a TEOS thin film, but may be a thermally oxidized
film or a silicate glass-based oxide film.
[0065] In processing of the substrate W by the processing unit 2, a
carry-in step (step S1 in FIG. 4) is performed to carry the
substrate W into the chamber 4. Specifically, with all the nozzles
being retracted from over the spin chuck 5, the control device 3
controls a transfer robot (not shown) holding the substrate W to
move its hand into the chamber 4. The control device 3 then
controls the transfer robot to place the substrate W on the spin
chuck 5. Thereafter, the control device 3 controls the spin chuck 5
to hold the substrate W thereon. Subsequently, the control device 3
controls the spin chuck 5 to start rotating the substrate W at a
low speed (e.g. 1 to 30 rpm). After the substrate W is placed on
the spin chuck 5, the control device 3 controls the transfer robot
to retract its hand from inside the chamber 4.
[0066] Next, a phosphoric acid supply step (step S2 in FIG. 4) is
performed as an etching step to supply phosphoric acid aqueous
solution, an example of etching liquid, onto the substrate W.
Specifically, the control device 3 controls the phosphoric acid
nozzle moving device 23 to move the phosphoric acid nozzle 18 from
the retracted position to the processing position. This causes the
phosphoric acid nozzle 18 to be disposed over the substrate W on
the rotation axis A1 of the substrate W. Thereafter, the control
device 3 opens the phosphoric acid valve 20 to cause phosphoric
acid aqueous solution, the temperature of which is controlled by
the phosphoric acid temperature control device 21, to be discharged
through the phosphoric acid nozzle 18 toward the upper surface of
the rotating substrate W. In this state, the control device 3
controls the phosphoric acid nozzle moving device 23 to move the
position at which the phosphoric acid aqueous solution lands with
respect to the upper surface of the substrate W between the central
portion and the peripheral portion.
[0067] As shown in FIG. 5A, the phosphoric acid aqueous solution
discharged through the phosphoric acid nozzle 18 lands on the upper
surface of the substrate W and then, due to a centrifugal force,
flows outward along the upper surface of the substrate W. The
phosphoric acid aqueous solution is thus supplied over the entire
upper surface of the substrate W, so that a liquid film of
phosphoric acid aqueous solution covering the entire upper surface
of the substrate W is formed on the substrate W. This causes the
upper surface of the substrate W to be etched, that is, the silicon
nitride film to be removed selectively. Further, since with the
substrate W rotating, the control device 3 moves the position at
which the phosphoric acid aqueous solution lands with respect to
the upper surface of the substrate W between the central portion
and the peripheral portion, the phosphoric acid aqueous solution
landing position passes across and scans the entire upper surface
of the substrate W. This causes the phosphoric acid aqueous
solution discharged through the phosphoric acid nozzle 18 to be
directly supplied over the entire upper surface of the substrate W,
so that the entire upper surface of the substrate W is processed
uniformly.
[0068] Next, a puddle step (step S3 in FIG. 4) is performed to hold
the liquid film of phosphoric acid aqueous solution on the
substrate W with the supply of phosphoric acid aqueous solution
onto the substrate W being stopped. Specifically, the control
device 3 controls the spin chuck 5 to keep the substrate W still or
decelerate the rotation of the substrate W to a rotation speed
(e.g. lower than 10 rpm) lower than the rotation speed of the
substrate W during the phosphoric acid supply step with the entire
upper surface of the substrate W being covered with the liquid film
of phosphoric acid aqueous solution. As a result, the centrifugal
force acting on the phosphoric acid aqueous solution on the
substrate W decreases and thereby the amount of phosphoric acid
aqueous solution removed from the substrate W decreases. With the
substrate W being kept still or rotating at the low rotation speed,
the control device 3 closes the phosphoric acid valve 20 to stop
the discharge of phosphoric acid aqueous solution through the
phosphoric acid nozzle 18. This causes, as shown in FIG. 5B, a
puddle-shaped liquid film of phosphoric acid aqueous solution
covering the entire upper surface of the substrate W to be held on
the substrate W with the supply of phosphoric acid aqueous solution
onto the substrate W being stopped. After the supply of phosphoric
acid aqueous solution onto the substrate W is stopped, the control
device 3 controls the phosphoric acid nozzle moving device 23 to
retract the phosphoric acid nozzle 18 from over the spin chuck
5.
[0069] Next, a heating step (step S4 in FIG. 4) to heat the
phosphoric acid aqueous solution on the substrate W and a pure
water supply step (step S4 in FIG. 4) to supply pure water droplets
onto the phosphoric acid aqueous solution on the substrate W are
performed in parallel to the puddle step. Specifically, the control
device 3 controls the infrared heater 31 to start light emitting.
Thereafter, the control device 3 controls the heater moving device
33 to move the infrared heater 31 and the pure water nozzle 38 from
the retracted position to the processing position. After the
infrared heater 31 and the pure water nozzle 38 are disposed over
the substrate W, the control device 3 controls the heater moving
device 33 to move the infrared heater 31 and the pure water nozzle
38 horizontally such that the region with respect to the upper
surface of the substrate W irradiated with infrared light moves
back and forth between the central portion and the peripheral
portion of the substrate W within the range indicated by the arrow
in FIG. 3. At this time, the control device 3 may move the infrared
heater 31 with the substrate opposing surface of the infrared
heater 31 being in contact with the liquid film of phosphoric acid
aqueous solution on the substrate W or with the lower surface of
the infrared heater 31 being separated by a predetermined distance
from the liquid film of phosphoric acid aqueous solution on the
substrate W.
[0070] The control device 3 opens and closes the pure water valve
40 multiple times while the position irradiated with infrared light
moves back and forth between the central portion of the upper
surface of the substrate W and the peripheral portion of the upper
surface of the substrate W. This causes, as shown in FIG. 5C, the
pure water landing position to move between the central portion of
the upper surface of the substrate W and the peripheral portion of
the upper surface of the substrate W and multiple pure water
droplets to be discharged one by one through the pure water
discharge port 37 of the pure water nozzle 38. With the removal of
phosphoric acid aqueous solution from the substrate W being
stopped, the multiple pure water droplets are thus supplied to
multiple positions within the upper surface of the substrate W.
After the substrate W is heated by the infrared heater 31 over a
predetermined period of time, the control device 3 stops the
discharge of droplets through the pure water nozzle 38 and retracts
the infrared heater 31 and the pure water nozzle 38 from over the
substrate W. Thereafter, the control device 3 controls the infrared
heater 31 to stop light emitting.
[0071] Since with the substrate W rotating, the control device 3
moves the position with respect to the upper surface of the
substrate W irradiated with infrared light back and forth between
the central portion and the peripheral portion, the substrate W is
uniformly heated. Accordingly, the liquid film of phosphoric acid
aqueous solution covering the entire upper surface of the substrate
W is also uniformly heated. The temperature to which the substrate
W is to be heated by the infrared heater 31 is set to a temperature
equal to or higher than the boiling point of phosphoric acid
aqueous solution at the current concentration (100.degree. C. or
higher and, for example, a predetermined temperature within the
range from 140.degree. C. to 160.degree. C.). The phosphoric acid
aqueous solution on the substrate W is therefore heated to the
boiling point at the current concentration and maintained in the
boiled state. Particularly, in the case where the temperature to
which the substrate W is to be heated by the infrared heater 31 is
set higher than the boiling point of phosphoric acid aqueous
solution at the current concentration, the temperature of the
interface between the substrate W and the phosphoric acid aqueous
solution is maintained at a temperature higher than the boiling
point, which enhances the etching of the substrate W.
[0072] Since the phosphoric acid aqueous solution is maintained in
a boiled state in the heating step (S4), a large amount of moisture
is evaporated from the phosphoric acid aqueous solution. With the
evaporation, a reaction of
2H.sub.3PO.sub.4.fwdarw.H.sub.4P.sub.2O.sub.7+H.sub.2O causes
pyrophosphoric acid (H.sub.4P.sub.2O.sub.7) to be generated, which
may etch the silicon oxide film. However, the control device 3
supplies pure water onto the phosphoric acid aqueous solution on
the substrate W at an amount corresponding to the amount of water
evaporated from the phosphoric acid aqueous solution, which
replenishes the phosphoric acid aqueous solution with evaporated
moisture and thereby reduces the change in the concentration of the
phosphoric acid aqueous solution. This suppresses the fluctuation
in the etching rate. Further, pyrophosphoric acid once generated in
the phosphoric acid aqueous solution decreases through reaction
with the replenished pure water, which suppresses or prevents the
reduction in the etching selectivity.
[0073] The etching of the silicon oxide film is thus suppressed
efficiently by reducing pyrophosphoric acid existing at the
interface between the substrate W and the phosphoric acid aqueous
solution. In the pure water supply step, pure water is supplied
onto the phosphoric acid aqueous solution on the substrate W in the
form of droplets. Since the supplied pure water droplets move
without breaking up in the phosphoric acid aqueous solution (see
FIG. 5C), it is possible to reliably cause the pure water to reach
the interface between the substrate W and the phosphoric acid
aqueous solution and to reliably reduce pyrophosphoric acid
existing at the interface between the substrate W and the
phosphoric acid aqueous solution. This reliably suppresses or
prevents the reduction in the etching selectivity.
[0074] Pure water with which to replenish the phosphoric acid
aqueous solution may be atomized through the pure water discharge
port 37. However, since atomized pure water would mostly be
absorbed at the superficial layer of the phosphoric acid aqueous
solution, it may be impossible to cause a sufficient amount of pure
water to reach the interface between the substrate W and the
phosphoric acid aqueous solution. It is therefore desirable to
discharge droplet pure water through the pure water discharge port
37. In addition, since the phosphoric acid aqueous solution on the
substrate W is heated to 100.degree. C. or higher, it is initially
difficult for atomized pure water, which is easily evaporated, to
reach the superficial layer of the phosphoric acid aqueous
solution. Also in view of the above, it is desirable to discharge
droplet pure water through the pure water discharge port 37.
[0075] Pure water with which to replenish the phosphoric acid
aqueous solution may be continuously discharged through the pure
water discharge port 37 or may be intermittently discharged through
the pure water discharge port 37. It is, however, difficult to
supply a small amount of water continuously at high accuracy. On
the other hand, in the case of intermittent discharging of pure
water, it is possible to supply a small amount of water at
relatively high accuracy. For this reason, intermittently
discharging pure water through the pure water discharge port 37
allows the changes in the concentration and temperature of the
phosphoric acid aqueous solution to be more reliably
suppressed.
[0076] It is noted that in the case of performing substrate heating
and pure water supply in step S4 with the substrate opposing
surface of the infrared heater 31 being in contact with the liquid
film of phosphoric acid aqueous solution on the substrate W as
shown in FIG. 5C, it is desirable that the supplied pure water is
not interposed between the liquid film of phosphoric acid aqueous
solution and the substrate opposing surface of the infrared heater
31. This is for the reason that pure water has a boiling point
lower than that of phosphoric acid aqueous solution and, if
interposed as above, pure water might be evaporated instantaneously
due to heating by the infrared heater 31.
[0077] Next, a phosphoric acid removing step (step S5 in FIG. 4) is
performed to remove the phosphoric acid aqueous solution on the
substrate W. Specifically, with the supply of liquid onto the
substrate W being stopped, the control device 3 controls the spin
chuck 5 to rotate the substrate W at a rotation speed (e.g. 500 to
3000 rpm) higher than the rotation speed of the substrate W during
the puddle step. This causes a centrifugal force larger than in the
puddle step to act on the phosphoric acid aqueous solution on the
substrate W, whereby the phosphoric acid aqueous solution on the
substrate W is diverted from the substrate W. Also, the phosphoric
acid aqueous solution scattered around the substrate W is received
by the cup 9 and guided to the collect apparatus via the cup 9. The
phosphoric acid aqueous solution guided to the collect apparatus is
then resupplied to the substrate W. This reduces the amount of use
of phosphoric acid aqueous solution.
[0078] Next, a first rinse liquid supply step (step S6 in FIG. 4)
is performed to supply pure water, an example of rinse liquid, onto
the substrate W. Specifically, the control device 3 opens the rinse
liquid valve 30 so that pure water is discharged through the rinse
liquid nozzle 28 toward the central portion of the upper surface of
the substrate W, while rotating the substrate W. This causes a
liquid film of pure water covering the entire upper surface of the
substrate W to be formed and the phosphoric acid aqueous solution
remaining on the substrate W to be rinsed off by the pure water.
When a predetermined period of time elapses after the rinse liquid
valve 30 is opened, the control device 3 closes the rinse liquid
valve 30 to stop pure water discharging.
[0079] Next, a chemical liquid supply step (step S7 in FIG. 4) is
performed to supply SC1, an example of chemical liquid, onto the
substrate W. Specifically, the control device 3 controls the SC1
nozzle moving device 27 to move the SC1 nozzle 24 from the
retracted position to the processing position. After the SC1 nozzle
24 is disposed over the substrate W, the control device 3 opens the
SC1 valve 26 to discharge SC1 through the SC1 nozzle 24 toward the
upper surface of the rotating substrate W. In this state, the
control device 3 controls the SC1 nozzle moving device 27 to move
the position at which SC1 lands on, with respect to the upper
surface of the substrate W, back and forth between the central
portion and the peripheral portion. When a predetermined period of
time elapses after the SC1 valve 26 is opened, the control device 3
closes the SC1 valve 26 to stop SC1 discharging. The control device
3 then controls the SC1 nozzle moving device 27 to retract the SC1
nozzle 24 from over the substrate W.
[0080] The SC1 discharged through the SC1 nozzle 24 lands on the
upper surface of the substrate W and then, due to a centrifugal
force, flows outward along the upper surface of the substrate W.
Accordingly, the pure water on the substrate W is washed away
outward by the SC1 and removed to around the substrate W. This
causes the liquid film of pure water on the substrate W to be
replaced with the liquid film of SC1 covering the entire upper
surface of the substrate W. Further, since with the substrate W
rotating, the control device 3 moves the position at which the SC1
lands on, with respect to the upper surface of the substrate W,
between the central portion and the peripheral portion, the SC1
landing position passes across and scans the entire upper surface
of the substrate W. This causes the SC1 discharged through the SC1
nozzle 24 to be sprayed directly over the entire upper surface of
the substrate W, so that the entire upper surface of the substrate
W is processed uniformly.
[0081] Next, a second rinse liquid supply step (step S8 in FIG. 4)
is performed to supply pure water, an example of rinse liquid, onto
the substrate W. Specifically, the control device 3 opens the rinse
liquid valve 30 so that pure water is discharged through the rinse
liquid nozzle 28 toward the central portion of the upper surface of
the substrate W, while rotating the substrate W. Accordingly, the
SC1 on the substrate W is washed away outward by the pure water and
removed to around the substrate W. This causes the liquid film of
SC1 on the substrate W to be replaced with the liquid film of pure
water covering the entire upper surface of the substrate W. When a
predetermined period of time elapses after the rinse liquid valve
30 is opened, the control device 3 closes the rinse liquid valve 30
to stop pure water discharging.
[0082] Next, a drying step (step S9 in FIG. 4) is performed to dry
the substrate W. Specifically, the control device 3 controls the
spin chuck 5 to accelerate the rotation of the substrate W and
thereby to rotate the substrate W at a rotation speed (e.g. 500 to
3000 rpm) higher than the rotation speed up to the second rinse
liquid supply step. This causes a large centrifugal force to act on
the liquid on the substrate W, so that the liquid adhering to the
substrate W is diverted from the substrate W. The liquid is thus
removed from the substrate W and hence the substrate W is dried.
When a predetermined period of time elapses after the substrate W
starts to rotate at a high speed, the control device 3 stops the
rotation of the substrate W by the spin chuck 5.
[0083] Next, a carry-out step (step S10 in FIG. 4) is performed to
carry the substrate W out of the chamber 4. Specifically, the
control device 3 controls the spin chuck 5 to release the substrate
W held thereon. Thereafter, with all the nozzles being retracted
from over the spin chuck 5, the control device 3 controls the
transfer robot (not shown) to move its hand into the chamber 4. The
control device 3 then controls the transfer robot to hold the
substrate W on the spin chuck 5 with its hand. Thereafter, the
control device 3 controls the transfer robot to retract its hand
from inside the chamber 4. The processed substrate W is thus
carried out of the chamber 4.
[0084] FIG. 6 is a graph showing an example of the relationship
between the radial distance from the center of the substrate W to
the pure water landing position and the radial moving speed of the
pure water landing position as well as the amount of pure water
supply. FIG. 7 is a graph showing another example of the
relationship between the radial distance from the center of the
substrate W to the pure water landing position and the radial
moving speed of the pure water landing position as well as the
amount of pure water supply.
[0085] The control device 3 controls the heater moving device 33 to
move the pure water nozzle 38 horizontally and thereby to move the
position at which pure water lands on, with respect to the upper
surface of the substrate W. Further, the control device 3 controls
the degree of opening of the pure water flow rate control valve 41
to change the size (volume) of droplets discharged through the pure
water nozzle 38 and thereby to control the flow rate of pure water
discharged through the pure water discharge port 37.
[0086] It is desirable that the amount of etching of the silicon
nitride film be uniform over the entire upper surface of the
substrate W. It is therefore necessary to increase the in-plane
etching rate uniformity. In other words, the silicon nitride film
is required to have substantially the same etching rate in both the
peripheral portion and the central portion of the upper surface of
the substrate W. Since the etching rate of the silicon nitride film
depends on the concentration of phosphoric acid aqueous solution,
pure water replenishment is required to make the concentration
constant over the entire upper surface of the substrate W. It is
desirable that when the substrate W stops or substantially stops
(rotates at several revolutions per minute), the speed of the pure
water landing position moving radially on the upper surface of the
substrate W (hereinafter referred to as substrate traversing speed)
be constant and the flow rate of pure water discharged through the
pure water discharge port 37 be constant. This allows both the
peripheral portion and the central portion of the upper surface of
the substrate W to be supplied with substantially the same amount
of pure water per unit area and thereby the concentration of
phosphoric acid aqueous solution to be uniformized over the upper
surface of the substrate W. It is therefore possible to increase
the in-plane etching rate uniformity.
[0087] Meanwhile, when the substrate W is rotated at a relatively
high speed during the above-described pure water supply step, an
approximately equivalent centrifugal force may cause a
concentration unevenness in the radial direction of the substrate W
to act on the phosphoric acid aqueous solution on the substrate W.
It can be considered that phosphoric acid aqueous solution, which
has a viscosity higher than that of water, is less likely to move
outward on the substrate W compared to pure water. It is therefore
conceivable that a large amount of pure water may move from the
central portion of the upper surface of the substrate W to the
peripheral portion of the upper surface of the substrate W,
resulting in the phosphoric acid aqueous solution having a
relatively high concentration in the central portion of the
substrate W, while having a relatively low concentration in the
peripheral portion of the substrate W.
[0088] In fact, the present inventors have confirmed a phenomenon
that when the substrate traversing speed is constant and the flow
rate of pure water discharged through the pure water discharge port
37 is also constant, increasing the rotation speed of the substrate
W to, for example, up to about 10 rpm results in the amount of
etching of the silicon nitride film being smaller in the peripheral
portion of the upper surface of the substrate W than in the central
portion of the upper surface of the substrate W.
[0089] This can be for the reason that the above-described
mechanism acts on the liquid film on the substrate W. That is, it
can be considered that despite the generally uniform thickness of
the liquid film on the substrate W in the case where the rotation
speed of the substrate W is about 10 rpm, the difference in the
amount of etching exists because a large amount of pure water moves
to the peripheral portion of the substrate W and, as a result, the
concentration of phosphoric acid aqueous solution in the peripheral
portion of the substrate W decreases. It is therefore conceivable
that when supplying pure water onto the liquid film of phosphoric
acid aqueous solution on the substrate W while rotating the
substrate W at a relatively high speed (e.g. 10 rpm or higher),
setting the amount of pure water supply per unit area larger in the
central portion of the upper surface of the substrate W than in the
peripheral portion of the upper surface of the substrate W can
reduce the variation in the concentration of phosphoric acid
aqueous solution in the radial direction of the substrate W and, as
a result, can suppress or prevent the variation in the etching rate
in the radial direction of the substrate W.
[0090] To set the amount of pure water supply per unit area larger
in the central portion of the upper surface than in the peripheral
portion of the upper surface of the substrate W, it suffices to
control at least one of the substrate traversing speed and the flow
rate of pure water discharged through the pure water discharge port
37 according to the pure water landing position. For example, the
control device 3 controls the heater moving device 33 such that the
substrate traversing speed becomes lower in the central portion of
the upper surface of the substrate W than in the peripheral portion
of the upper surface of the substrate W. Alternatively, it suffices
to control the pure water supply device 36 such that the flow rate
of pure water discharged through the pure water discharge port 37
becomes higher in the central portion of the upper surface of the
substrate W than in the peripheral portion of the upper surface of
the substrate W (see FIG. 6).
[0091] In the case of rotating the substrate W at a higher speed,
it is necessary to further increase the amount of pure water supply
per unit area in the central portion of the upper surface of the
substrate W. In this case, it suffices that the control device 3
controls as shown in FIG. 7. That is, as the pure water landing
position comes close to the central portion of the upper surface of
the substrate W from the peripheral portion of the upper surface of
the substrate W, the control device 3 may control the heater moving
device 33 such that the substrate traversing speed decreases and
control the pure water supply device 36 such that the flow rate of
pure water discharged through the pure water discharge port 37
increases, which interact to result in the amount of pure water
supply per unit area of the substrate W rapidly increasing as the
pure water nozzle 38 comes close to the central portion of the
substrate W.
[0092] On the other hand, as the pure water landing position moves
away from the central portion of the upper surface of the substrate
W, the control device 3 may control the heater moving device 33
such that the substrate traversing speed increases and control the
pure water supply device 36 such that the flow rate of pure water
discharged through the pure water discharge port 37 decreases,
which interact to result in the amount of pure water supply per
unit area of the substrate W rapidly decreasing as the pure water
nozzle 38 moves away from the central portion of the substrate
W.
[0093] FIG. 8 is a graph showing the relationship between the
temperature of phosphoric acid aqueous solution supplied onto the
substrate W and the etching rate as well as the etching
selectivity.
[0094] As shown in FIG. 8, the etching rate of LP-SiN, an example
of the silicon nitride film, acceleratedly increases as the
temperature of phosphoric acid aqueous solution increases. On the
other hand, the etching rate of LP-TEOS, an example of the silicon
oxide film, is approximately zero when the temperature of
phosphoric acid aqueous solution is in the range of 140.degree. C.
or lower. When the temperature of phosphoric acid aqueous solution
is within the range from 140.degree. C. to 170.degree. C., the
etching rate of LP-TEOS increases gradually as the temperature of
phosphoric acid aqueous solution increases and when the temperature
of phosphoric acid aqueous solution is in the range of 170.degree.
C. or higher, acceleratedly increases as the temperature of
phosphoric acid aqueous solution increases. Increasing the
temperature of phosphoric acid aqueous solution involves an
increase in the etching rate of the silicon nitride film, however,
when the temperature of phosphoric acid aqueous solution is in the
range of 140.degree. C. or higher, this results in the silicone
oxide film also being etched. This leads to a reduction in the
etching selectivity. Hence, setting the temperature of phosphoric
acid aqueous solution to a predetermined temperature within the
range from 120.degree. C. to 160.degree. C. (preferably 140.degree.
C.) can increase the etching rate while maintaining a high etching
selectivity.
[0095] In the first preferred embodiment, a low amount of pure
water is supplied onto the liquid film of phosphoric acid aqueous
solution. More specifically, the flow rate of pure water supplied
onto the substrate W is set by the pure water flow rate control
valve 41 to a value at which the phosphoric acid aqueous solution
is not removed from the substrate W, that is, the liquid film of
phosphoric acid aqueous solution is maintained in a puddle shape on
the substrate W. This can prevent the phosphoric acid aqueous
solution, which has sufficient activity, from being removed from
the substrate W. This allows the phosphoric acid aqueous solution
to be used efficiently. Further, since the amount of pure water
supplied to the phosphoric acid aqueous solution on the substrate W
is small, the changes in the concentration and temperature of the
phosphoric acid aqueous solution can be suppressed. It is therefore
possible to suppress the fluctuation in the etching rate.
[0096] In the first preferred embodiment, pure water is supplied
onto the liquid film of phosphoric acid aqueous solution at an
amount corresponding to the amount of water evaporated from the
liquid film of phosphoric acid aqueous solution. That is, the
liquid film of phosphoric acid aqueous solution is replenished with
pure water by the evaporated amount. This results in the
pyrophosphoric acid in the phosphoric acid aqueous solution
decreasing through reaction with the supplied pure water and the
change in the concentration of the phosphoric acid aqueous solution
associated with the pure water supply being substantially
prevented. Further, since the amount of pure water supplied to the
phosphoric acid aqueous solution on the substrate W is small, the
changes in the concentration and temperature of the phosphoric acid
aqueous solution can be suppressed. It is therefore possible to
suppress the fluctuation in the etching rate while suppressing the
reduction in the etching selectivity.
[0097] In the first preferred embodiment, pure water droplets, not
in an atomized form, are discharged through the pure water
discharge port 37 one by one toward the upper surface of the
substrate W. That is, pure water droplets are intermittently
discharged through the pure water discharge port 37. Pure water
droplets landing on the phosphoric acid aqueous solution on the
substrate W move without breaking up in the phosphoric acid aqueous
solution toward the interface between the substrate Wand the
phosphoric acid aqueous solution. Pure water does not diffuse
immediately in the phosphoric acid aqueous solution and therefore a
relatively large amount of pure water can reach the interface
between the substrate W and the phosphoric acid aqueous solution,
which in turn causes pyrophosphoric acid existing at the interface
between the substrate W and the phosphoric acid aqueous solution to
decrease. This can suppress or prevent the reduction in the etching
selectivity.
[0098] In the first preferred embodiment, the substrate W is
irradiated with infrared light emitted from the infrared heater 31
and radiant heat is transferred from the infrared heater 31 to the
substrate W. This heats the substrate W and therefore the
phosphoric acid aqueous solution on the substrate W. Alternatively,
the infrared light directly heats the phosphoric acid aqueous
solution. The infrared heater 31 emits infrared light with at least
a portion thereof being in contact with the liquid film of
phosphoric acid aqueous solution. Accordingly, the infrared heater
31 suppresses water evaporation from the phosphoric acid aqueous
solution. This can suppress the change in the concentration of the
phosphoric acid aqueous solution. It is further possible to
suppress the generation of pyrophosphoric acid in the phosphoric
acid aqueous solution and thereby to prevent the etching
selectivity from decreasing while stabilizing the etching rate.
[0099] In the first preferred embodiment, the heating device 10
heats the phosphoric acid aqueous solution on the substrate W to
the boiling point. This can increase the etching rate of the
silicon nitride film. While the amount of water evaporation from
the phosphoric acid aqueous solution increases, the pure water
supply device 36 replenishes the phosphoric acid aqueous solution
with pure water at an amount corresponding to the amount of
evaporation, whereby the concentration of the phosphoric acid
aqueous solution does not significantly change. It is therefore
possible to stabilize the etching rate.
[0100] In the first preferred embodiment, the substrate W is heated
to a temperature equal to or higher than the boiling point of
phosphoric acid aqueous solution. The temperature of the upper
surface of the substrate W in contact with the phosphoric acid
aqueous solution is thus brought up to a temperature equal to or
higher than the boiling point of phosphoric acid aqueous solution.
It is therefore possible to maintain the phosphoric acid aqueous
solution in a boiled state at the interface between the substrate W
and the phosphoric acid aqueous solution. This can increase the
etching rate.
[0101] In the first preferred embodiment, the heater moving device
33 moves the infrared heater 31 and the pure water nozzle 38 while
maintaining the positional relationship between the pure water
landing position and the position irradiated with infrared light.
At this time, the heater moving device 33 moves the infrared heater
31 such that a region adjacent to the pure water landing position
is heated by the infrared heater 31. Accordingly, the vicinity of
the pure water landing position is heated by the infrared heater
31. It is hence possible to shorten the time required for the
substrate W and the phosphoric acid aqueous solution, even if the
temperature of which may change with the pure water supply, to
return to the original temperature. This can suppress the reduction
in the etching uniformity.
[0102] In the first preferred embodiment, the heater moving device
33 moves the infrared heater 31 such that a region downstream from
the position at which pure water lands on, with respect to the
upper surface of the substrate W, with respect to the rotation
direction Dr of the substrate W is heated. Accordingly, the pure
water landing region (a portion of the substrate W) moves
immediately, with the rotation of the substrate W, to the heated
region (the region irradiated with infrared light) to be heated by
the infrared heater 31. It is hence possible to shorten the time
required for the substrate W and the phosphoric acid aqueous
solution, even if the temperature of which may decrease temporarily
with the pure water supply, to return to the original temperature.
This can suppress the reduction in the etching uniformity.
[0103] In the first preferred embodiment, the control device 3
changes the speed of the pure water landing position traveling
across the substrate W from the peripheral portion to the central
portion of the substrate (or the speed traveling across the
substrate W from the central portion to the peripheral portion of
the substrate, i.e., substrate traversing speed) according to the
rotation speed of the substrate W. Specifically, when the rotation
speed of the substrate W is lower than a predetermined speed, the
control device 3 moves the pure water landing position at a
constant substrate traversing speed between the central portion of
the upper surface of the substrate W and the peripheral portion of
the upper surface of the substrate W. On the other hand, when the
rotation speed of the substrate W is equal to or higher than the
predetermined speed, the control device 3 reduces the substrate
traversing speed of the pure water landing position as the pure
water landing position comes close to the central portion of the
upper surface of the substrate W from the peripheral portion of the
substrate W or increases the substrate traversing speed of the pure
water landing position as the pure water landing position moves
away from the central portion of the upper surface of the
substrate. Accordingly, when the rotation speed of the substrate W
is equal to or higher than the predetermined speed, the central
portion of the upper surface of the substrate W is supplied with
pure water at an amount larger than the peripheral portion of the
upper surface of the substrate W.
[0104] The present inventors have confirmed a phenomenon that when
the rotation speed of the substrate W is high, the amount of
etching is larger in the central portion of the upper surface of
the substrate W than in the peripheral portion of the upper surface
of the substrate W. The difference in the amount of etching can be
for the reason that the concentration of phosphoric acid aqueous
solution is higher in the central portion of the upper surface of
the substrate W than in the peripheral portion of the upper surface
of the substrate W. Hence, the control device 3 is arranged to
supply pure water onto the central portion of the upper surface of
the substrate W at an amount larger than onto the peripheral
portion of the upper surface of the substrate W to thereby reduce
the concentration of phosphoric acid aqueous solution in the
central portion of the upper surface of the substrate W. The
control device 3 can thus be arranged to prevent the amount of
etching from increasing in the central portion of the upper surface
of the substrate W. This can increase the in-plane etching
uniformity.
Second Preferred Embodiment
[0105] Next will be described a second preferred embodiment of the
present invention. The second preferred embodiment differs from the
first preferred embodiment primarily in that the processing unit 2
further includes a humidifying device 242. In the following
description of FIGS. 9 and 10, components identical to those shown
in FIGS. 1 to 8 described above are designated by the same
reference symbols as in FIG. 1 and other drawings are omitted from
the description thereof.
[0106] FIG. 9 is a horizontal schematic view showing an infrared
heater 231 and the spin chuck 5 according to the second preferred
embodiment of the present invention. FIG. 10 is a vertical
cross-sectional view of the infrared heater 231 according to the
second preferred embodiment of the present invention.
[0107] The processing unit 2 according to the second preferred
embodiment further includes the humidifying device 242 for
discharging humidifying gas with a humidity higher than that within
the chamber 4 over the substrate W. The humidifying device 242
includes a humidifying nozzle 250 for discharging humidifying gas
therethrough over the substrate W. The humidifying nozzle 250 may
be provided integrally with or separately from the infrared heater
31. FIGS. 9 and 10 show an example in which the humidifying nozzle
250 is provided integrally with the infrared heater 31.
[0108] The heating device 10 includes the infrared heater 231, in
place of the infrared heater 31 according to the first preferred
embodiment. The infrared heater 231 includes an infrared lamp 234
for emitting infrared light and a lamp housing 235 housing the
infrared lamp 234 therein. The infrared lamp 234 is disposed within
the lamp housing 235. The lamp housing 235 is smaller than the
substrate W in a plan view. Accordingly, the infrared lamp 234
disposed within the lamp housing 235 is also smaller than the
substrate W in a plan view. The infrared lamp 234 and the lamp
housing 235 are attached to the heater arm 32. Accordingly, the
infrared lamp 234 and the lamp housing 235 swing together with the
heater arm 32 about the swing axis A3 (see FIG. 1).
[0109] The infrared lamp 234 includes a filament and a quartz tube
housing the filament therein. As shown in FIG. 10, the infrared
lamp 234 includes an ended annular portion 243a disposed along a
horizontal plane and a pair of vertical portions 243b extending
upward from one and the other end portions of the annular portion
243a. The infrared lamp 234 (e.g. halogen lamp) may be a carbon
heater or another type of heating element. At least a portion of
the lamp housing 235 is made of a material having optical
transparency and heat resistance, such as quartz.
[0110] When the infrared lamp 234 emits light, light containing
infrared light is emitted from the infrared lamp 234. The light
containing infrared light transmits through the lamp housing 235 to
be emitted from the outer surface of the lamp housing 235 or heats
the lamp housing 235 to emit radiant light from the outer surface
of the lamp housing 235. The substrate W and a liquid film of
phosphoric acid aqueous solution held on the upper surface of the
substrate W are heated by the transmitted light and radiant light
from the outer surface of the lamp housing 235. Although
transmitted or radiant light containing infrared light is thus
emitted from the outer surface of the lamp housing 235, the
infrared lamp 234 will hereinafter be described focusing on
infrared light transmitting through the outer surface of the lamp
housing 235.
[0111] The lamp housing 235 includes a transmissive member through
which infrared light can transmit. As shown in FIG. 10, the
transmissive member includes a vertically extending cylindrical
housing portion 244, a disk-like bottom plate portion 245 closing
the lower end of the housing portion 244, a central tube 246
vertically extending along the center line of the housing portion
244 and protruding downward from the lower surface of the bottom
plate portion 245 and a disk-like opposing plate 247 disposed below
the bottom plate portion 245 and supported on the lower end of the
central tube 246. The lamp housing 235 further includes a lid
member 248 closing the upper end of the housing portion 244 and a
support member 249 supporting the pair of vertical portions 243b of
the infrared lamp 234. The infrared lamp 234 is supported on the
lid member 248 via the support member 249.
[0112] As shown in FIG. 10, the annular portion 243a of the
infrared lamp 234 is disposed in a cylindrical space defined by the
housing portion 244, the bottom plate portion 245 and the central
tube 246. The annular portion 243a of the infrared lamp 234
surrounds the central tube 246 inside the housing portion 244. The
bottom plate portion 245 is disposed below the infrared lamp 234
and vertically opposed to the infrared lamp 234 with a space
therebetween. Similarly, the opposing plate 247 is disposed below
the bottom plate portion 245 and vertically opposed to the bottom
plate portion 245 with a space therebetween. The bottom plate
portion 245 and the opposing plate 247 have the same outside
diameter with respect to each other. The lower surface of the
bottom plate portion 245 and the upper surface of the opposing
plate 247 are vertically opposed parallel to each other with a
space therebetween.
[0113] Infrared light from the infrared lamp 234 transmits downward
through the bottom plate portion 245 and the opposing plate 247,
which are made of quartz, to be emitted downward from the lower
surface of the opposing plate 247. The lower surface of the
opposing plate 247 includes a flat irradiation surface parallel to
the upper surface of the substrate W. When the infrared heater 231
is disposed over the substrate W, the irradiation surface of the
lamp housing 235 is vertically opposed to the upper surface of the
substrate W with a space therebetween. In this state, infrared
light, when emitted from the infrared lamp 234, transmits through
the lamp housing 235 and then travels from the irradiation surface
of the lamp housing 235 toward the upper surface of the substrate W
to be irradiated onto the upper surface of the substrate W. This
allows radiant heat transferred from the infrared lamp 234 to the
substrate W to heat the substrate W.
[0114] As shown in FIG. 10, the humidifying device 242 includes the
humidifying nozzle 250 constituted by the bottom plate portion 245
and the opposing plate 247, a humidifying gas pipe 251 for
supplying humidifying gas therethrough to the central tube 246 and
a humidifying gas valve 252 for switching between start and stop of
the supply of humidifying gas from the humidifying gas pipe 251 to
the central tube 246. The lower end of the central tube 246 is
closed by the opposing plate 247. The central tube 246 includes
multiple (e.g. eight) through holes 253 disposed at heights between
the lower surface of the bottom plate portion 245 and the upper
surface of the opposing plate 247. The multiple through holes 253
extend from the inner peripheral surface to the outer peripheral
surface of the central tube 246 to be opened in the outer
peripheral surface of the central tube 246. The multiple through
holes 253 are disposed circumferentially with a space therebetween.
The humidifying nozzle 250 includes an annular discharge port 254
constituted by the outer peripheral portion of the bottom plate
portion 245 and the outer peripheral portion of the opposing plate
247. The annular discharge port 254 continues in the entire
circumferential direction and is disposed around the multiple
through holes 253.
[0115] When the humidifying gas valve 252 is opened, humidifying
gas supplied through the humidifying gas pipe 251 to the central
tube 246 is discharged through the multiple through holes 253 to
around the central tube 246 to flow outward in the radial direction
of the substrate W between the lower surface of the bottom plate
portion 245 and the upper surface of the opposing plate 247. After
reaching the outer peripheral portions of the bottom plate portion
245 and the opposing plate 247, the humidifying gas is then
horizontally discharged through the annular discharge port 254.
This causes an airflow of the humidifying gas radially spreading
from the annular discharge port 254 to be formed. The humidifying
gas is vapor of lower than 100.degree. C. The humidifying gas is
not limited to vapor, but may be a mist of pure water (atomized
pure water of the room temperature) or superheated vapor of
100.degree. C. or higher.
[0116] In processing of the substrate W by the processing unit 2,
the control device 3 (see FIG. 1) performs a humidifying step to
discharge vapor, an example of humidifying gas, within the chamber
4 in parallel to the radiant heating step, the pure water supply
step and the puddle step described above. Specifically, the control
device 3 opens the humidifying gas valve 252, before moving the
infrared heater 231 and the pure water nozzle 38 over the substrate
W, to start discharging vapor through the humidifying nozzle 250.
This increases the humidity within the chamber 4 and the vapor
pressure approaches the saturation vapor pressure. Since the
discharge of vapor through the humidifying nozzle 250 continues
even after the control device 3 moves the infrared heater 231 and
the pure water nozzle 38 over the substrate, the atmosphere over
the substrate W can approach the saturation vapor pressure. It is
noted that the discharge of vapor through the humidifying nozzle
250 may be started after the infrared heater 231 starts emitting
infrared light, although performed from before the infrared heater
231 starts emitting infrared light in this preferred
embodiment.
[0117] After the infrared heater 231 and the pure water nozzle 38
are disposed over the substrate W, the control device 3 controls
the heater moving device 33 to move the infrared heater 231 and the
pure water nozzle 38 horizontally such that the position with
respect to the upper surface of the substrate W irradiated with
infrared light moves from one to the other of the central portion
and the peripheral portion. At this time, the control device 3 may
move the infrared heater 231 with the lower surface of the opposing
plate 247 being in contact with the liquid film of phosphoric acid
aqueous solution on the substrate W or with the lower surface of
the infrared heater 231 being separated by a predetermined distance
from the liquid film of phosphoric acid aqueous solution on the
substrate W.
[0118] The control device 3 opens and closes the pure water valve
40 multiple times while the position irradiated with infrared light
moves between the central portion of the upper surface of the
substrate W and the peripheral portion of the upper surface of the
substrate W. This causes the pure water landing position to move
between the central portion of the upper surface of the substrate W
and the peripheral portion of the upper surface of the substrate W
and pure water to be intermittently discharged, preferably several
pure water droplets to be discharged one by one through the pure
water discharge port 37 of the pure water nozzle 38. With the
removal of phosphoric acid aqueous solution from the substrate W
being stopped, the multiple pure water droplets are thus supplied
to multiple positions within the upper surface of the substrate W.
After the substrate W is heated by the infrared heater 231 over a
predetermined period of time, the control device 3 stops the
discharge of droplets through the pure water nozzle 38 and retracts
the infrared heater 231 and the pure water nozzle 38 from over the
substrate W. Thereafter, the control device 3 controls the infrared
heater 231 to stop light emitting and controls the humidifying
nozzle 250 to stop vapor discharging. The discharge of vapor
through the humidifying nozzle 250 may be stopped before or after
the infrared heater 231 stops emitting infrared light.
[0119] Since with the phosphoric acid aqueous solution on the
substrate W being heated, the control device 3 thus makes the
humidifying nozzle 250 discharge humidifying gas with a humidity
higher than that within the chamber 4, the humidity within the
chamber 4 increases. This reduces the amount of water evaporation
from the phosphoric acid aqueous solution. Particularly in the
second preferred embodiment, since the humidifying gas is radially
discharged through the annular discharge port 254 and an airflow of
the humidifying gas flowing along the upper surface of the
substrate W is formed, the entire upper surface of the liquid film
is covered with the airflow of the humidifying gas. As a result,
compared to the case where humidifying gas is discharged at a
position away from the substrate W, the humidity in the vicinity of
the substrate W can be reliably increased and thereby the water
evaporation from the phosphoric acid aqueous solution can be
suppressed efficiently. It is therefore possible to efficiently
suppress the generation of pyrophosphoric acid and suppress the
reduction in the etching selectivity.
[0120] In the above-described second preferred embodiment,
humidifying gas with a humidity higher than that within the chamber
4 is supplied into the chamber 4. This results in an increase in
the humidity within the chamber 4 and therefore an increase in the
vapor pressure within the chamber 4 to a value equal to or lower
than the saturation vapor pressure. This suppresses water
evaporation from the phosphoric acid aqueous solution on the
substrate W. It is therefore possible to efficiently suppress the
generation of pyrophosphoric acid in the phosphoric acid aqueous
solution and suppress the reduction in the etching selectivity.
[0121] In the second preferred embodiment, humidifying gas with a
humidity higher than that within the chamber 4 and a temperature
higher than the ambient temperature (room temperature) within the
chamber 4 is supplied into the chamber 4. This results in an
increase in the humidity and ambient temperature within the chamber
4. It is therefore possible to suppress the reduction in the
etching rate.
[0122] In the second preferred embodiment, the humidifying gas is
radially discharged through the annular discharge port 254 in a
direction parallel to the upper surface of the substrate W. This
causes an airflow of the humidifying gas radially spreading from
the annular discharge port 254 to be formed over the liquid film of
phosphoric acid aqueous solution and thus the liquid film of
phosphoric acid aqueous solution to be covered with the airflow of
the humidifying gas. This reliably increases the humidity over the
liquid film of phosphoric acid aqueous solution. This suppresses
water evaporation from the phosphoric acid aqueous solution on the
substrate W. It is therefore possible to suppress the generation of
pyrophosphoric acid in the phosphoric acid aqueous solution and
suppress the reduction in the etching selectivity.
Third Preferred Embodiment
[0123] Next will be described a third preferred embodiment of the
present invention. The third preferred embodiment differs from the
first preferred embodiment primarily in that the heating device 10
includes a heating fluid supply device for supplying heating fluid
onto the lower surface of the substrate W to heat the substrate W,
in addition to the radiant heating device according to the first
preferred embodiment. In the following description of FIG. 11,
components identical to those shown in FIGS. 1 to 10 described
above are designated by the same reference symbols as in FIG. 1 and
other drawings are omitted from the description thereof.
[0124] FIG. 11 is a horizontal schematic view showing a fluid
nozzle 356 and the spin chuck 5 according to the third preferred
embodiment of the present invention.
[0125] The heating device 10 according to the third preferred
embodiment further includes a heating fluid supply device for
discharging heating fluid onto the substrate W to heat the
substrate W and increase the humidity within the chamber 4. The
heating fluid supply device includes the fluid nozzle 356 for
discharging heating fluid with a temperature higher than that of
the substrate W through a fluid discharge port 355 toward the lower
surface of the substrate W, a fluid pipe 357 for supplying heating
fluid therethrough to the fluid nozzle 356 and a fluid valve 358
for switching between start and stop of the supply of heating fluid
from the fluid pipe 357 to the fluid nozzle 356. The fluid nozzle
356 includes the fluid discharge port 355 for discharging heating
fluid therethrough upward.
[0126] The fluid discharge port 355 of the fluid nozzle 356 is
disposed between the lower surface of the substrate W and the upper
surface of the spin base 14. The fluid discharge port 355 of the
fluid nozzle 356 is vertically opposed to a central portion of the
lower surface of the substrate W with a space therebetween. The
heating fluid is superheated vapor. The heating fluid is not
limited to superheated vapor, but may be high-temperature pure
water (with a temperature higher than that of the substrate W) or
high-temperature gas (inert gas or clean air with a temperature
higher than that of the substrate W). That is, the heating fluid
may be liquid (heating liquid) or gaseous (heating gas).
[0127] When the fluid valve 358 is opened, heating fluid is
discharged through the fluid discharge port 355 of the fluid nozzle
356 toward the central portion of the lower surface of the
substrate W. If the heating fluid is heating liquid, the heating
liquid, when discharged through the fluid discharge port 355 of the
fluid nozzle 356 with the substrate W rotating, collides with the
central portion of the lower surface of the substrate W and then,
due to a centrifugal force, radially diffuses along the lower
surface of the substrate W from the central portion of the lower
surface of the substrate W to a peripheral portion of the lower
surface of the substrate W. If the heating fluid is heating gas,
the heating fluid, when discharged through the fluid nozzle 356,
collides with the central portion of the lower surface of the
substrate W and then radially diffuses between the lower surface of
the substrate W and the upper surface of the spin base 14, that is,
in the space between the substrate W and the spin base 14. The
heating fluid, if may be either heating liquid or heating gas, is
thus supplied onto the entire lower surface of the substrate W, so
that the substrate W is heated entirely and uniformly.
[0128] In processing of the substrate W by the processing unit 2,
the control device 3 (see FIG. 1) starts a heating fluid supply
step to discharge superheated vapor, an example of heating fluid,
toward the lower surface of the substrate W before starting the
above-described phosphoric acid supply step. Specifically, the
control device 3 opens the fluid valve 358 so that superheated
vapor is discharged through the fluid nozzle 356 toward the central
portion of the lower surface of the substrate W. The discharge of
superheated vapor may be started with the substrate W rotating or
not rotating.
[0129] The superheated vapor discharged through the fluid nozzle
356 collides with the central portion of the lower surface of the
substrate W and then radially diffuses between the lower surface of
the substrate W and the upper surface of the spin base 14, that is,
in the space between the substrate W and the spin base 14. The
superheated vapor then comes into contact with the entire lower
surface and the circumferential end surface of the substrate W, so
that heat of the superheated vapor is transferred to the entire
lower surface of the substrate W. This heats the substrate W
uniformly.
[0130] With the fluid nozzle 356 discharging superheated vapor
therethrough, the control device 3 performs the above-described
phosphoric acid supply step. Similarly, with the fluid nozzle 356
discharging superheated vapor therethrough, the control device 3
performs the radiant heating step, the pure water supply step and
the puddle step described above. After retracting the infrared
heater 31 and the pure water nozzle 38 from over the substrate W,
the control device 3 then closes the fluid valve 358 to stop
superheated vapor discharging through the fluid nozzle 356. The
discharge of superheated vapor through the fluid nozzle 356 may be
stopped before or after the infrared heater 31 stops emitting
infrared light.
[0131] In the above-described third preferred embodiment, the upper
surface of the substrate W is irradiated with infrared light
emitted from the infrared heater 31, so that the substrate W is
heated. Further, heating fluid discharged through the fluid nozzle
356 is supplied onto the entire lower surface of the substrate W,
so that the substrate W is heated in its entirety. The heating
fluid with a temperature higher than that of the substrate W is
thus supplied onto the entire lower surface of the substrate W,
which can increase the processing temperature uniformity over the
entire substrate W. It is therefore possible to increase the
temperature uniformity of the liquid film of phosphoric acid
aqueous solution and therefore the etching uniformity.
[0132] Particularly in the case where superheated vapor of
100.degree. C. or higher, serving as heating fluid and heating gas,
is discharged through the fluid nozzle 356 serving as a heating
device and supplied onto the entire lower surface of the substrate
W, the substrate W and the liquid film of phosphoric acid aqueous
solution on the substrate W can be heated efficiently. Further, the
superheated vapor on the lower surface of the substrate W can flow
around through the circumferential end surface of the substrate W
onto the upper surface of the substrate W or diffuse around the
spin chuck 5 holding the substrate W thereon to humidify the
interior of the chamber 4. This suppresses water evaporation from
the phosphoric acid aqueous solution on the substrate W. It is
therefore possible to reduce pyrophosphoric acid in the phosphoric
acid aqueous solution and suppress the reduction in the etching
selectivity.
Fourth Preferred Embodiment
[0133] Next will be described a fourth preferred embodiment of the
present invention. The fourth preferred embodiment differs from the
first preferred embodiment primarily in that the pure water
discharge port 37 for discharging pure water therethrough is
provided in a central portion of the lower surface of an infrared
heater 431. In the following description of FIG. 12, components
identical to those shown in FIGS. 1 to 11 described above are
designated by the same reference symbols as in FIG. 1 and other
drawings are omitted from the description thereof.
[0134] FIG. 12 is a schematic view showing the vertical
cross-section and the bottom surface of the infrared heater 431 and
the pure water nozzle 38 according to the fourth preferred
embodiment of the present invention.
[0135] The heating device 10 according to the fourth preferred
embodiment includes the infrared heater 431, in place of the
infrared heater 31 according to the first preferred embodiment. The
infrared heater 431 includes the infrared lamp 234 for emitting
infrared light and a lamp housing 435 housing the infrared lamp 234
therein. The infrared lamp 234 is disposed within the lamp housing
435. The lamp housing 435 is smaller than the substrate W in a plan
view. Accordingly, the infrared lamp 234 disposed within the lamp
housing 435 is also smaller than the substrate W in a plan view.
The infrared lamp 234 and the lamp housing 435 are attached to the
heater arm 32 (see FIG. 1). Accordingly, the infrared lamp 234 and
the lamp housing 435 swing together with the heater arm 32 about
the swing axis A3 (see FIG. 1). It is noted that in the heating and
pure water supply step S4 in the first preferred embodiment, the
heater arm 32 is swung such that the pure water landing position
moves only between the central portion of the upper surface of the
substrate W and one peripheral position of the upper surface of the
substrate W (the range indicated by the arrow in FIG. 3). However,
in the fourth preferred embodiment, the swing range of the heater
arm 32 in the heating and pure water supply step S4 is expanded
such that the pure water landing position moves between two
peripheral positions of the substrate W.
[0136] The infrared lamp 234 includes a filament and a quartz tube
housing the filament therein. The infrared lamp 234 further
includes the ended annular portion 243a disposed along a horizontal
plane and the pair of vertical portions 243b extending upward from
one and the other end portions of the annular portion 243a. The
infrared lamp 234 serving as a heating device (e.g. halogen lamp)
may be a carbon heater or another type of heating element. At least
a portion of the lamp housing 435 is made of a material having
optical transparency and heat resistance, such as quartz.
[0137] When the infrared lamp 234 emits light, light containing
infrared light is emitted from the infrared lamp 234. The light
containing infrared light transmits through the lamp housing 435 to
be emitted from the outer surface of the lamp housing 435 or heats
the lamp housing 435 to emit radiant light from the outer surface
of the lamp housing 435. The substrate W and a liquid film of
phosphoric acid aqueous solution held on the upper surface of the
substrate W are heated by the transmitted light and radiant light
from the outer surface of the lamp housing 435. Although
transmitted or radiant light containing infrared light is thus
emitted from the outer surface of the lamp housing 435, the
infrared lamp 234 will hereinafter be described focusing on
infrared light transmitting through the outer surface of the lamp
housing 435.
[0138] The lamp housing 435 includes a transmissive member through
which infrared light can transmit. The transmissive member includes
the vertically extending cylindrical housing portion 244, the
disk-like bottom plate portion 245 closing the lower end of the
housing portion 244 and the central tube 246 vertically extending
along the center line of the housing portion 244 and opened in a
central portion of the lower surface of the bottom plate portion
245. The lamp housing 435 further includes the lid member 248
closing the upper end of the housing portion 244 and the support
member 249 supporting the pair of vertical portions 243b of the
infrared lamp 234. The infrared lamp 234 is supported on the lid
member 248 via the support member 249.
[0139] The annular portion 243a of the infrared lamp 234 is
disposed in a cylindrical space defined by the housing portion 244,
the bottom plate portion 245 and the central tube 246. The annular
portion 243a of the infrared lamp 234 surrounds the central tube
246 inside the housing portion 244. The bottom plate portion 245 is
disposed below the infrared lamp 234 and vertically opposed to the
infrared lamp 234 with a space therebetween. The pure water nozzle
38 is inserted into the central tube 246. The pure water discharge
port 37 of the pure water nozzle 38 is disposed inside the central
tube 246. As shown in the lower part of FIG. 12, the pure water
discharge port 37 is surrounded by the lower surface of the bottom
plate portion 245 serving as an irradiation surface when the
infrared heater 431 is viewed from below. Accordingly, pure water
droplets discharged through the pure water nozzle 38 are discharged
through the lower surface of the bottom plate portion 245.
[0140] In accordance with the arrangement above, since pure water
droplets are discharged through the irradiation surface of the
infrared heater 431, the pure water landing position is included in
the position irradiated with infrared light. That is, when the pure
water discharge port 37 discharges pure water droplets therethrough
with the substrate W rotating and the infrared heater 431 emitting
infrared light, the region on which the pure water droplets land,
regardless of its position within the upper surface of the
substrate W, moves immediately to the irradiated position to be
heated. Accordingly, even if the infrared heater 431 and the pure
water nozzle 38 may move between two positions at which pure water
droplets land on the peripheral portion of the upper surface of the
substrate W, the region on which the pure water droplets land is
heated immediately. This can suppress the fluctuation in the
temperature of the substrate W.
Fifth Preferred Embodiment
[0141] Next will be described a fifth preferred embodiment of the
present invention. The fifth preferred embodiment differs from the
first preferred embodiment primarily in that the pure water supply
device 36 further includes a pure water temperature control device
559 for controlling the temperature of pure water discharged
through the pure water nozzle 38. In the following description of
FIG. 13, components identical to those shown in FIGS. 1 to 12
described above are designated by the same reference symbols as in
FIG. 1 and other drawings are omitted from the description
thereof.
[0142] FIG. 13 is a schematic view of the pure water supply device
36 according to the fifth preferred embodiment of the present
invention.
[0143] The pure water supply device 36 includes the pure water
nozzle 38, the pure water pipe 39, the pure water valve 40 and the
pure water flow rate control valve 41, and additionally the pure
water temperature control device 559 for controlling the
temperature of pure water supplied through the pure water pipe 39
to the pure water nozzle 38. The pure water temperature control
device 559 includes a temperature controller 560 (at least one of a
heater and a cooler) for controlling the temperature of pure water
flowing within the pure water pipe 39. FIG. 13 shows an example in
which both a heater and a cooler are provided in the pure water
temperature control device 559. The pure water temperature control
device 559 may further include a temperature sensor 561 for
detecting the temperature of pure water the temperature of which is
controlled by the temperature controller 560.
[0144] In accordance with the arrangement above, pure water
droplets, the temperature of which is controlled by the pure water
temperature control device 559, are supplied onto the substrate W
in the above-described pure water supply step. The pure water, if
having an excessively high temperature, may be evaporated before
reaching the interface between the substrate W and the phosphoric
acid aqueous solution. On the other hand, if the pure water has an
excessively low temperature, the temperature of the phosphoric acid
aqueous solution on the substrate W may significantly change.
Hence, pure water droplets, the temperature of which is controlled
by the pure water temperature control device 559, are discharged
through the pure water nozzle 38 to allow the pure water to reach
the interface between the substrate W and the phosphoric acid
aqueous solution while suppressing the fluctuation in the
temperature of the phosphoric acid aqueous solution on the
substrate W. If the temperature sensor 561 is provided in the pure
water temperature control device 559, the control device 3 can
control the temperature set by the temperature controller 560 based
on a value detected by the temperature sensor 561. The control
device 3 can therefore control the temperature of pure water to be
supplied onto the substrate W more precisely.
Other Preferred Embodiments
[0145] Although the first to fifth preferred embodiments of the
present invention have been described heretofore, the present
invention is not limited to the description of the above-described
first to fifth preferred embodiments and various modifications may
be made within the scope of the appended claims.
[0146] For example, the first to fifth preferred embodiments
describe the case where the infrared heater 31 including the
infrared lamp 34 is used as a heater. However, another type of
heating element such as a heating wire may be used as a heating
device for heating the substrate W to substitute for the infrared
lamp 34.
[0147] The first to fifth preferred embodiments describe the case
where the spin chuck 5 for horizontally holding and rotating the
substrate W thereon is used as a substrate holding device. However,
the processing unit 2 may include a substrate holding device for
horizontally holding the substrate W thereon in a still state to
substitute for the spin chuck 5.
[0148] Although the first to fifth preferred embodiments describe
the case where the infrared heater 31 and the pure water nozzle 38
are attached to the common movable arm (heater arm 32), the
infrared heater 31 and the pure water nozzle 38 may be attached to
different movable arms. That is, the pure water supply device 36
may include a nozzle arm with a pure water nozzle attached to the
tip portion thereof (movable arm different from the heater arm 32)
and a pure water nozzle moving device for moving the nozzle arm to
move the pure water nozzle. In this case, the positional
relationship between the position irradiated with infrared light
and pure water landing position may not be constant. The phosphoric
acid nozzle 18, the infrared heater 31 and the pure water nozzle 38
may also be attached to a common movable arm (e.g. heater arm 32).
It is noted that in the fourth preferred embodiment, since the pure
water nozzle 38 is disposed inside the infrared heater 431, the
pure water nozzle 38 and the infrared heater 431 are attached to
the same movable arm (heater arm 32).
[0149] Although the first, second, third and fifth preferred
embodiments describe the case where the control device 3 swings the
infrared heater 31 and the pure water nozzle 38 between the center
position where the pure water landing position is in the central
portion of the upper surface of the substrate W and the edge
position where the pure water landing position is in the peripheral
portion of the upper surface of the substrate W, the control device
3 may move the infrared heater 31 and the pure water nozzle 38
between two edge positions at which pure water droplets discharged
through the pure water nozzle 38 land on the peripheral portion of
the upper surface of the substrate W.
[0150] Although the first, second, third and fifth preferred
embodiments describe the case where the pure water nozzle 38 is
attached to the heater arm 32 closer to the tip of the heater arm
32 than the infrared heater 31, the pure water nozzle 38 may be
attached to the heater arm 32 closer to the base of the heater arm
32 than the infrared heater 31. Alternatively, the infrared heater
31 and the pure water nozzle 38 may be disposed at the same
distance from the swing axis A3 in a plan view and laid
side-by-side in the swing direction of the heater arm 32.
[0151] The first to fifth preferred embodiments describe the case
where the pure water valve 40 is opened and closed to form pure
water droplets. However, the pure water nozzle 38 may include a
piezo element for vibrating and thereby splitting pure water
discharged through the pure water discharge port 37 with the pure
water valve 40 being opened.
[0152] Although the first to fifth preferred embodiments describe
the case where the rotation speed of the substrate W is maintained
constant during the pure water supply step, the rotation speed of
the substrate W may be changed during the pure water supply
step.
[0153] Specifically, a low-speed rotation step to rotate the
substrate W at a rotation speed (e.g. 1 to 30 rpm) lower than the
rotation speed of the substrate W during the phosphoric acid supply
step and a high-speed rotation step to rotate the substrate W at a
rotation speed (e.g. 50 rpm) higher than the low rotation speed may
be performed in parallel to the pure water supply step. In this
case, a large centrifugal force acts on pure water droplets
supplied onto the substrate W during the high-speed rotation step,
whereby pure water can diffuse to a wider range within the upper
surface of the substrate W in a short time.
[0154] The first to fifth preferred embodiments describe the case
where the infrared heater 31 starts heating the substrate W after
phosphoric acid aqueous solution is supplied onto the substrate W.
However, the infrared heater 31 may start heating the substrate W
before phosphoric acid aqueous solution is supplied onto the
substrate W. In this case, phosphoric acid aqueous solution is
supplied onto the substrate W with the substrate W being heated,
which can shorten the time required to bring the temperature of the
phosphoric acid aqueous solution up to a predetermined
temperature.
[0155] Although the first to fifth preferred embodiments describe
the case where the infrared heater 31 heats the substrate W and the
pure water nozzle 38 supplies pure water therethrough with the
supply of phosphoric acid aqueous solution onto the substrate W
being stopped, the infrared heater 31 may heat the substrate W and
the pure water nozzle 38 may supply pure water therethrough with
the phosphoric acid nozzle 18 discharging phosphoric acid aqueous
solution therethrough. That is, the radiant heating step and the
pure water supply step may be performed in parallel to the
phosphoric acid supply step. In this case, the puddle step may be
omitted.
[0156] Although the third preferred embodiment describes the case
where the fluid nozzle 356 is provided to discharge heating fluid
therethrough toward the substrate W, the fluid nozzle 356 may not
be provided if a hot plate with a heating element incorporated
therein is used to substitute for the spin base 14. In this case,
since the substrate W is horizontally held on the hot plate with
the entire lower surface of the substrate W being in contact with
the upper surface of the hot plate, heat constantly emitted from
the hot plate is uniformly transferred to the entire substrate W.
This allows the substrate W to be uniformly heated.
[0157] Although the first to fifth preferred embodiments describe
the case where the substrate processing apparatus 1 is arranged to
process a disk-like substrate W, the substrate processing apparatus
1 may be arranged to process a polygonal substrate W such as a
liquid crystal display device substrate.
[0158] The preferred embodiments of the present invention, which
have heretofore been described in detail, are merely specific
examples used to clarify the technical details of the present
invention. The present invention should not be understood to be
limited to these specific examples. The spirit and scope of the
present invention is limited only by the terms of the appended
claims.
[0159] This application corresponds to Japanese Patent Application
No. 2013-28125 filed with the Japan Patent Office on Feb. 15, 2013,
the disclosure of which is incorporated by reference herein in its
entirety.
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