U.S. patent application number 10/765272 was filed with the patent office on 2004-10-28 for wet etching apparatus and wet etching method using ultraviolet light.
This patent application is currently assigned to Semiconductor Leading Edge Technologies, Inc.. Invention is credited to Kume, Satoshi, Nishimori, Hirotomo.
Application Number | 20040211756 10/765272 |
Document ID | / |
Family ID | 32950862 |
Filed Date | 2004-10-28 |
United States Patent
Application |
20040211756 |
Kind Code |
A1 |
Kume, Satoshi ; et
al. |
October 28, 2004 |
Wet etching apparatus and wet etching method using ultraviolet
light
Abstract
A substrate having a film to be etched is held on a rotating
stage. While rotating the substrate, a chemical solution containing
an etchant is supplied onto the substrate from a nozzle. A lamp
house with a drive unit is positioned so that the distance between
the substrate and a glass window of the lamp house becomes 2 to 5
mm, the lamp house accommodating a lamp generating ultraviolet
light. The ultraviolet light irradiates the film through the
chemical solution. The ultraviolet light has a higher energy than
the binding energy of constituent molecules of the film.
Inventors: |
Kume, Satoshi; (Ibaraki,
JP) ; Nishimori, Hirotomo; (Kyoto, JP) |
Correspondence
Address: |
LEYDIG VOIT & MAYER, LTD
700 THIRTEENTH ST. NW
SUITE 300
WASHINGTON
DC
20005-3960
US
|
Assignee: |
Semiconductor Leading Edge
Technologies, Inc.
Ibaraki
JP
Ushio Denki Kabushiki Kaisha
Tokyo-to
JP
|
Family ID: |
32950862 |
Appl. No.: |
10/765272 |
Filed: |
January 28, 2004 |
Current U.S.
Class: |
216/92 ;
257/E21.251 |
Current CPC
Class: |
H01L 21/31645 20130101;
H01L 21/6708 20130101; H01L 21/67086 20130101; H01L 21/31111
20130101 |
Class at
Publication: |
216/092 |
International
Class: |
C23F 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 30, 2003 |
JP |
2003-021566 |
Claims
1. A wet etching apparatus comprising: a chemical-solution supply
component for supplying a chemical solution to a film to be
processed, the film being supported by a substrate, and an
ultraviolet-light radiating component for irradiating the film with
ultraviolet light through the chemical solution.
2. The wet etching apparatus according to claim 1, wherein the
ultraviolet-light radiating component radiates ultraviolet light
having an energy higher than binding energy of constituent
molecules of the film.
3. The wet etching apparatus according to claim 1, further
comprising a drive unit for moving the ultraviolet-light radiating
component, wherein the ultraviolet-light radiating component is
moved at a location 2 mm to 5 mm above a surface of the film, when
the film is being irradiated with the ultraviolet light.
4. The wet etching apparatus according to claim 1, wherein the
ultraviolet-light radiating component comprises: a light source
generating the ultraviolet light; a storage component for
accommodating the light source and having a light-transmitting
window for facing the film; and a nozzle in the chemical-solution
supply component, disposed at a gap between the light-transmitting
window and the film, for continuously supplying the chemical
solution in the gap.
5. The wet etching apparatus according to claim 4, further
comprising a stage for holding the substrate, the stage including a
pair of guides parallel to the nozzle, for sandwiching the
substrate.
6. The wet etching apparatus according to claim 4, including a
layer of a surface-active agent located at a surface of the
light-transmitting window and contacting the chemical solution.
7. The wet etching apparatus according to claim 4, wherein the
chemical-solution supply component comprises: a switching valve
connected to the nozzle through a pipe and for switching between a
supply of the chemical solution and a supply of ultra-pure water; a
pipe for supplying the chemical solution and connected to the
switching valve; and a pipe for supplying the ultra-pure water and
connected to the switching valve.
8. A method for wet etching of a film, comprising: supplying a
chemical solution to a film to be processed, the film being
disposed on a substrate; and irradiating the film with ultraviolet
light through the chemical solution.
9. The method for wet etching according to claim 8, including
supplying the chemical solution and irradiating the film with
ultraviolet light simultaneously.
10. The method for wet etching according to claim 8, including
irradiating the film with ultraviolet light having an energy higher
than the binding energy of constituent molecules of the film.
11. The method for wet etching according to claim 8, wherein the
film is a high-k dielectric film that has been annealed.
Description
1. FIELD OF THE INVENTION
[0001] The present invention relates to a semiconductor
manufacturing apparatus, and specifically to a wet etching
apparatus and a wet etching method.
2. DESCRIPTION OF THE BACKGROUND ART
[0002] In recent years, a high-dielectric-constant film (hereafter
referred to as "high-k dielectric film") is used as a gate
insulating film for an advanced device. The high-k dielectric film
is acceleratedly densified by heat treatment (i.e. annealing)
performed after film formation, and high-k dielectric film is
changed to have properties difficult to etch.
[0003] Heretofore, for etching of films to be etched, there have
been used wet etching wherein a film to be etched is made to
contact a chemical solution and etching is performed by an etchant
dissociated in the chemical solution; and dry etching wherein
radicals and ionic species excited in plasma are drawn in a
substrate to forcedly etching a film to be etched.
[0004] However, there has been the problem of very low etching rate
when a dense thin film, such as a high-k dielectric film after
annealing, is subjected to wet etching. Therefore, there has been
the problem of significantly low throughputs.
[0005] When a dense thin film is subjected to dry etching in place
of wet etching, there has been a problem that although a higher
etching rate is obtained than wet etching, the base member that
should not be etched is continuously etched. That is to say, there
has been a problem that a sufficient etching selectivity to the
base member cannot be obtained by dry etching.
[0006] Heretofore, such difficulty of etching has been a drawback
when a high-k dielectric film is applied to advanced devices.
SUMMARY OF THE INVENTION
[0007] The present invention has been conceived to solve the
previously-mentioned problems and a general object of the present
invention is to provide a novel and useful wet etching apparatus
and is to provide a novel and useful wet etching method.
[0008] A more specific object of the present invention is to
provide a wet etching apparatus and a wet etching method having a
high etching selectivity to a base member below a film to be
processed, and having a high etching rate.
[0009] The above object of the present invention is attained by a
following wet etching apparatus and a following method for wet
etching of a film.
[0010] According to one aspect of the present invention, the wet
etching apparatus comprises a chemical-solution supply component
for supplying a chemical solution on a film to be processed on a
substrate. An ultraviolet-light radiating component radiates
ultraviolet light to the film through the chemical solution.
[0011] According to another aspect of the present invention, in the
method for wet etching of a film, a chemical solution is supplied
on a film to be processed on a substrate. Ultraviolet light is
radiated to the film through the chemical solution.
[0012] Other objects and further features of the present invention
will be apparent from the following detailed description when read
in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic sectional view for illustrating a wet
etching apparatus according to a first embodiment of the present
invention;
[0014] FIG. 2 is a schematic sectional view for illustrating a wet
etching apparatus according to a second embodiment of the present
invention;
[0015] FIG. 3 is a top view showing vicinity of a substrate in the
wet etching apparatus shown in FIG. 2; and
[0016] FIG. 4 is a sectional view for illustrating a substrate to
be wet etched.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] In the following, principles and embodiments of the present
invention will be described with reference to the accompanying
drawings. The members and steps that are common to some of the
drawings are given the same reference numerals and redundant
descriptions therefore may be omitted.
First Embodiment
[0018] FIG. 1 is a schematic sectional view for illustrating an
etching apparatus according to a first embodiment of the present
invention. Specifically, FIG. 1 is a diagram for illustrating an
etching apparatus for wet etching of a film to be etched formed on
a substrate.
[0019] As FIG. 1 shows, a substrate 11 to be wet etched is
rotatably held on a rotating stage 5. Specifically, a plurality of
pins 4 are installed on the rotating stage 5, and the end portion
(edge portion) of the substrate 11 is held between these pins 4.
The substrate 11 may also be held using an electrostatic chuck.
[0020] A rotating shaft 6 is disposed on the center of the rotating
stage 5, and when the rotating stage 5 rotates around the rotating
shaft 6, the substrate 11 is also rotates at a desired rotating
speed. The rotating stage 5 rotates at a rotating speed of, for
example, about 300 to 500 rpm during coating of a chemical
solution, and about 2,000 to 3,000 rpm during drying.
[0021] As FIG. 4 shows, a film to be etched (film to be processed)
11a is formed on the substrate 11 serving as a base member, and a
mask 11b is formed on the film 11a. The film 11a is, for example, a
dense thin film such as a high-k dielectric film. The high-k
dielectric film is, for example, HfO.sub.2 film and HfAlO film
formed using an ALD (atomic layer deposition) method and performed
an annealing (PDA: post deposition annealing) treatment after film
formation.
[0022] A chemical solution 9 is supplied to the surface of the film
to be etched on the substrate 11 through a nozzle 8 installed on
the end of a chemical pipe 7. The chemical-solution pipe 7 is
connected to a chemical tank (not shown) for storing the chemical
solution, or to a chemical-supply line of an incidental apparatus
(not shown)through a valve 7a and a pump 7b.
[0023] A chemical solution 9 containing, for example, a
phosphoric-acid-based etchant may also be used. In order to obtain
desired properties, a surface active agent or the like may be added
to the chemical solution 9.
[0024] Lamp house 2 stores a lamp 1. Lamp house 2 accommodating a
lamp 1, which radiates ultraviolet light to the film (11a) through
the chemical solution 9, is disposed above the substrate 11. The
lamp 1 serving as a light source is, for example, KrCl (wavelength:
222 nm), Xe.sub.2 (172 nm), Kr.sub.2 (147 nm), Ar.sub.2 (126 nm)
excimer lamps or the like. Here, the lamp 1 radiates ultraviolet
light at energy higher than binding energy of constituent molecules
of the film to be etched (11a). Energy of the ultraviolet light can
be controlled by a radiating time of the ultraviolet light. The
radiating time is, for example, 10 to 200 sec.
[0025] The materials of the chemical solution 9 and the thickness
of the film to be etched (11a) are selected so as to attain a high
transmissivity for the wavelength of the ultraviolet light radiated
from the lamp 1.
[0026] On the lower surface of the lamp house 2 is formed an
opening having the size same as, or larger than the size the
substrate 11. This opening is covered with a light-transmitting
window 3 formed by a material that transmits ultraviolet light from
the lamp 1. The light-transmitting window 3 is, for example, a
window formed of quartz glass (hereafter referred to as "quartz
glass window").
[0027] The inside of the lamp house 2 sealed with the quartz glass
window 3 is filled with an inert gas such as nitrogen. Thereby, a
lamp 1 having a wavelength absorbed in the presence of oxygen can
be used. Illuminance of the ultraviolet light at the quartz glass
window 3 is preferably 5 to 20 mW/cm.sup.2.
[0028] On the upper surface of the lamp house 2 is installed a
drive unit 10 for driving the lamp house 2 in the vertical
direction. The drive unit 10 drives the lamp house 2 to vicinity of
the substrate 11 when ultraviolet light is radiated, thereby acting
the ultraviolet light from the lamp 1 to the film (11a) in the
close distance. Specifically, the lamp house 2 is disposed so that
the quartz glass window 3 is disposed 2 to 5 mm above the surface
of the substrate 11.
[0029] Next, the operation of the etching apparatus, that is the
wet etching of the film to be etched will be described.
[0030] First, the substrate 11, which has an HfO.sub.2 film serving
as the film to be etched (11a) and the mask (11b), is held by pins
4 on the rotating stage 5. The chemical solution 9 containing a
phosphoric-acid-based is supplied on the substrate 11 from the
nozzle 8, while rotating the substrate 11 at a rotation speed of
300 to 500 rpm by rotating the rotating stage 5 around the rotating
shaft 6. Thereafter, when the chemical solution 9 is sufficiently
thinly and evenly spread on the substrate 11, the rotation of the
substrate 11 is stopped. At this time, the chemical solution 9 has
been applied on the entire surface of the substrate 11 in a desired
thickness without running off the substrate 11.
[0031] The lamp house 2 is lowered by the drive unit 10 so that the
quartz glass window 3 locates 2 to 5 mm above the surface of the
substrate 11 without interfering the pins 4. Ultraviolet light is
radiated from the lamp 1 that has previously been turned on to the
HfO.sub.2 film through the chemical solution 9. At this-time,
energy of the ultraviolet light breaks the Hf--O bonds of the
HfO.sub.2 film, and etching reaction proceeds by etchant contained
in the chemical solution 9 previously applied on the substrate
11.
[0032] After desired etching has been completed, radiating of the
ultraviolet light from the lamp 1 is stopped, the lamp house 2 is
elevated with by the drive unit 10. Ultra-pure water is supplied
from the water-cleaning nozzle (not shown) on the substrate 11 to
wash away the chemical solution 9 remaining on the substrate
11.
[0033] Thereafter, the substrate 11 is rotated at about 2,000 to
3,000 rpm with the rotating stage 5 to sprinkle the ultra-pure
water and to dry the substrate 11.
[0034] In the first embodiment, as described above, after a
chemical solution 9 has been applied to dense film to be etched,
ultraviolet light having energy larger than binding energy of
constituent molecules of the film to be etched is radiated to the
film to be etched through the chemical solution 9. Since the
ultraviolet light breaks the bonds of the molecules of the film to
be etched, the etching rate of the film to be etched contacting the
chemical solution 9 is significantly increased. In other words, by
wet etching performed in the state wherein the most molecular bonds
of the film to be etched have been broken, the etching rate can be
significantly increased. Therefore, the time of etching process can
be shortened, and the throughput can be improved. Also because of a
high etching selectivity to the base member (i.e. substrate 11),
the problem of continuous etching of the base member, as in the use
of dry etching, does not arise. Thereby, a dense high-k dielectric
film can be used in advanced semiconductor devices.
[0035] The chemical solution 9 used in the first embodiment has a
high transmissivity to the wavelength of the lamp 1. Therefore,
little ultraviolet light radiated from the lamp 1 is absorbed by
the chemical solution 9, and the ultraviolet light having
sufficient light energy can reach the film to be etched. Thus, the
loss of light energy of ultraviolet light by the chemical solution
9 can be decreased as much as possible.
[0036] The etching rate can further be improved by elevating the
temperature of the chemical solution 9 and/or the substrate 11
using a heat exchanger or a hot plate. In this case, however, the
quantity of vaporized chemical solution 9 increases, and cloud of
the surface of the quartz glass window 3 on the bottom of the lamp
house 2 may occur due to condensation of the vapor. The haze may
scatter the ultraviolet radiation, thereby causing insufficiency of
the action of the ultraviolet radiation to the film to be
etched.
[0037] To cope with this problem, it is preferable to apply a
surface-active agent having hydrophobic groups, or the like, to the
quartz glass window 3. The film of the surface-active agent
prevents the condensation of the vaporized chemical solution 9 on
the quartz glass window 3, and can prevent the loss of the light
energy of ultraviolet light (the same applies to the second
embodiment described below).
[0038] It is also considered that the quantity of the etchant in
the chemical solution 9 is insufficient by a single application of
the chemical solution 9, and the etching reaction ceases in the
middle. In the case where the supply of the etchant becomes the
rate-limiting factor, it is recommended the lamp house 2 is once
separated (elevated) from the vicinity of the substrate 11 using
the drive unit 10 to supply the chemical solution 9 again from the
nozzle 8, and the lamp house 2 is again lowered to the vicinity of
the substrate 11 to radiate ultraviolet light again.
[0039] However, when the supply of the etchant significantly
becomes the rate-limiting factor due to the mechanism of the
etching, since the supply of the chemical solution and the
radiation of the ultraviolet light must be repeated many times, the
processing time increases, and the throughput lowers. There also is
a case where the chemical solution 9 dries up due to heat given by
the light energy of ultraviolet light radiated after the
application of the chemical solution 9, and an irreversible state
may occur during water cleaning after wet etching. The effective
means in such a case will be described below as a second
embodiment.
[0040] In the first embodiment, the case where the film to be
etched was a high-k dielectric film was described. However, the
present invention is not limited thereto, but can be applied to a
film having a low wet-etching rate, and is particularly preferable
to a dense thin film (the same applies to the second embodiment
described below).
[0041] As a comparative example of the first embodiment, the
present inventors first radiated ultraviolet light from the lamp 1
to the film to be etched, and then the chemical solution 9 was
applied on the film to be etched. However, in the comparative
example, increase in the etching rate was little compared with the
first embodiment, and the desired effect could not be achieved.
Second Embodiment
[0042] FIG. 2 is a schematic sectional view for illustrating an
etching apparatus according to a second embodiment of the present
invention; and FIG. 3 is a top view showing vicinity of a substrate
in the etching apparatus shown in FIG. 2.
[0043] The etching apparatus according to the second embodiment is
particularly suitable in the case where supply of an etchant
significantly becomes the rate-limiting factor as described
above.
[0044] As FIG. 2 shows, a substrate 11 to be etched is held on a
plate-like stage 12 having a wider area than the substrate 11. On
the stage 12 are installed a plurality of pins 4 having a height
of, for example, 2 to 5 mm, and the end portion (edge portion) of
the substrate 11 is held between these pins 4. As FIG. 4 shows, a
film to be etched (film to be processed) 11a is formed on the
substrate 11, and a mask 11b is formed on the film 11a. The film
11a is, for example, a dense thin film such as a high-k dielectric
film. The high-k dielectric film is, for example, HfO.sub.2 film
and HfAlO film formed using an ALD (atomic layer deposition)
method, and annealing (PDA: post deposition annealing)
treatment.
[0045] As in the first embodiment, the lamp house 2 accommodating a
lamp 1 is driven by the drive unit 10 in the vertical direction.
When ultraviolet light is radiated, the lamp house 2 is disposed so
that the quartz glass window 3 is disposed 2 to 5 mm above the
surface of the substrate 11.
[0046] In the gap between the quartz glass window 3 and the
substrate 11, a tip portion 13a of a slit-like flat nozzle 13 is
inserted. Chemical solution 9 is continuously supplied to the gap
from the flat nozzle 13. Here, as FIG. 3 shows, on the stage 12, a
pair of guides 16 are formed so as to be parallel to the flat
nozzle 13 and so as to sandwich the substrate 11. Thereby, the
chemical solution 9, supplied to an end of the substrate 11 from
the flat nozzle 13, is guided by the guides 16 in the direction of
the other end of the substrate 11 facing the end (i.e., the
direction opposite from the flat nozzle 13), and gradually fills
the gap. Furthermore, the excess of the chemical solution 9
supplied from the flat nozzle 13 runs out in the direction opposite
from the flat nozzle 13.
[0047] The flat nozzle 13 is connected to an end of a pipe 15. The
other end of the pipe 15 is connected, through a switching valve
14, to a pipe 15a for chemical solution and a pipe 15b for
ultra-pure water. Specifically, the switching operation of the
switching valve 14 connects the flat nozzle 13 to the pipe 15a or
the pipe 15b through the pipe 15. That is to say, the flat nozzle
13 is connected to a chemical-solution supply line or a
ultra-pure-water supply line by switching the switching valve
14.
[0048] Next, the operation of the above-descried etching apparatus,
that is the wet etching of the film to be etched will be
described.
[0049] First, a substrate 11, which has an HfO.sub.2 film serving
as the film to be etched (11a) and mask (11b), is held by pins 4 on
the stage 12.
[0050] Then, the lamp house 2 is lowered with the drive unit 10 so
that the quartz glass window 3 locates 2 to 5 mm apart from the
surface of the substrate 11 without interfering the pins 4.
[0051] Next, the tip portion of the flat nozzle 13 is inserted in
the gap between the quartz glass window 3 and the substrate 11 from
the side to continuously supply the chemical solution 9 from the
flat nozzle 13 into the gap. At the same time as the supply of the
chemical solution 9, ultraviolet radiation is radiated from the
lamp 1 onto the HfO.sub.2 film through the chemical solution 9.
[0052] At this time, the light energy of the ultraviolet radiation
breaks the Hf--O bonds of the HfO.sub.2 film, and the etchant
contained in the chemical solution 9 supplied from the flat nozzle
13 proceeds the etching reaction. The chemical solution 9 supplied
from the flat nozzle 13 is led by the guide 16 to the opposite side
of the flat nozzle 13, and gradually enters into the gap, and
finally fills the gap. By further continuing the supply of the
chemical solution 9 at a constant flow rate, the excessive chemical
solution 9 runs out of the substrate 11 at the opposite side of the
flat nozzle 13. Thereby, the chemical solution 9 rich in the
etchant is supplied onto the film to be etched.
[0053] After desired etching has been completed, radiation of the
ultraviolet light from the lamp 1 is stopped. The location of the
lamp house 2 is stayed as it is, the switching valve 14 is switched
to supply ultra-pure water from the flat nozzle 13 into the gap,
and to wash away the chemical solution 9 remaining on the substrate
11. At this time, not only the chemical solution 9 remaining on the
substrate 11 is washed away, but also the parts that have contacted
the chemical solution 9, such as the quartz glass window 3, are
simultaneously cleaned.
[0054] In the second embodiment, as described above, the supply of
the chemical solution 9 from the flat nozzle 13 is performed
simultaneously with the radiation of the ultraviolet light from the
lamp 1 for wet etching. Therefore the same effect as in the first
embodiment is obtained.
[0055] Furthermore, in the second embodiment, while ultraviolet
light is radiated from the lamp 1 (i.e. during wet etching), the
chemical solution 9 is continuously supplied from the flat nozzle
13 into the gap between the quartz glass window 3 and the substrate
11. Thereby, the chemical solution 9 rich in the etchant can always
been supplied onto the film to be etched. Therefore, the etching
rate can be further increased compared with the first embodiment.
Thus, even in the etching reaction wherein the supply of the
etchant significantly becomes the rate-limiting factor, there is no
need to repeat the supply of the chemical solution and radiation of
the ultraviolet light, and the elongation of the processing time
and the lowering of the throughput can be prevented. The drying up
of the chemical solution 9 due to the evaporation of the chemical
solution 9 to change to an irreversible state can also be
prevented.
[0056] Also in the second embodiment, ultra-pure water is supplied
from the flat nozzle 13 by the switching operation of the switching
valve 14. Thereby, not only the substrate 11, but also
liquid-contacting parts, such as the flat nozzle 13 and the quartz
window 3 can be cleaned. Therefore, the installation of the
separate nozzle for ultra-pure water is not required, and the
etching apparatus can be simplified, and the costs thereof can be
reduced.
[0057] This invention, when practiced illustratively in the manner
described above, provides the following major effects:
[0058] According to the present invention, there can be provided an
etching apparatus and an etching method having a high etching
selectivity to the base member below the film to be processed, and
a high etching rate.
[0059] Further, the present invention is not limited to these
embodiments, but variations and modifications may be made without
departing from the scope of the present invention.
[0060] The entire disclosure of Japanese Patent Application No.
2003-21556 filed on Jan. 30, 2003 containing specification, claims,
drawings and summary are incorporated herein by reference in its
entirety.
* * * * *