U.S. patent application number 09/791553 was filed with the patent office on 2001-08-30 for apparatus of processing a sample surface and method thereof.
Invention is credited to Nakaune, Koichi, Oyama, Masatoshi.
Application Number | 20010017190 09/791553 |
Document ID | / |
Family ID | 18575708 |
Filed Date | 2001-08-30 |
United States Patent
Application |
20010017190 |
Kind Code |
A1 |
Nakaune, Koichi ; et
al. |
August 30, 2001 |
Apparatus of processing a sample surface and method thereof
Abstract
A surface processing apparatus is provided. In the apparatus, an
etching rate ratio of an organic material such as a BARC of
anti-reflective film to a resist of mask forming a pattern, that
is, a selective ratio is high, the anti-reflective film being a
means for forming the pattern with a high accuracy in surface
processing of a semiconductor. In the surface processing apparatus
using a plasma, a deposition gas is added to a light element of
hydrogen as the etching gas. Ions accelerated by a bias electric
power supply accelerate etching reaction. Sputtering at edges of
the mask can be reduced by using the light element of hydrogen as
the etching gas, and the selective ratio of the anti-reflective
film to the masking material can be increased by mixing the
deposition gas with the hydrogen.
Inventors: |
Nakaune, Koichi; (Kudamatsu,
JP) ; Oyama, Masatoshi; (Kudamatsu, JP) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
18575708 |
Appl. No.: |
09/791553 |
Filed: |
February 26, 2001 |
Current U.S.
Class: |
156/345.3 ;
118/723R; 216/41; 216/67; 257/E21.257 |
Current CPC
Class: |
H01L 21/31144
20130101 |
Class at
Publication: |
156/345 ; 216/41;
216/67; 118/723.00R |
International
Class: |
B44C 001/22; C23F
001/00; H01L 021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 25, 2000 |
JP |
2000-054459 |
Claims
What is claimed is:
1. An apparatus of processing a sample surface comprising a vacuum
chamber; a means for generating a plasma in said vacuum chamber; a
sample table for mounting a sample to be performed with surface
processing using said plasma; and an electric power supply for
applying a radio frequency bias to the sample, the surface
processing of the sample being performed using a masking material
and an anti-reflective film, the apparatus further comprising means
for introducing a mixed gas of hydrogen gas and a deposition gas as
an etching gas into said vacuum chamber.
2. An apparatus of processing a sample surface according to claim
1, wherein an amount of said deposition gas added to said hydrogen
gas is set to a value, said value being around an amount E0 at
which a cut-down amount of said masking material becomes zero and
within a range in which a selective ratio of said anti-reflective
film to said masking material is larger than 2.
3. A method of processing a sample surface which performs surface
processing of a sample by using a plasma by generating the plasma
in a vacuum chamber; applying a radio frequency bias to a sample
table mounting the sample; using a masking material and an
anti-reflective film, the method comprising the step of introducing
a mixed gas of hydrogen gas and a deposition gas as an etching gas
into said vacuum chamber.
4. A method of processing a sample surface according to claim 3,
wherein an amount of said deposition gas added to said hydrogen gas
is set to a value, said value being an amount E0 at which a
cut-down amount of said masking material becomes zero.
5. A method of processing a sample surface according to any one of
claim 3 and claim 4, wherein said deposition gas mixed with said
hydrogen gas is a gas containing carbon as a constituent
element.
6. A method of processing a sample surface according to any one of
claim 3 and claim 4, wherein said deposition gas contains one kind
selected from the group consisting of CHF.sub.3, CH.sub.2F.sub.2
and CF.sub.4.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a surface processing
apparatus and a surface processing method for a sample such as a
semiconductor element and, more particularly to a surface
processing apparatus and a surface processing method suitable for
performing etching and film forming on a semiconductor surface
using a plasma.
[0002] Apparatuses widely used for processing such as etching and
film forming of a semiconductor element are apparatuses using a
plasma. The present invention can be applied to such apparatuses
using a plasma, but here, a conventional technology will be
explained in taking an apparatus called as an ECR (electron
cyclotron resonance) type among them as an example. In the
apparatus of this type, the plasma is generated by a microwave in a
vacuum chamber applied with a magnetic field from the external. A
bias voltage is applied to a sample in order to accelerate ions
incident to the sample. The apparatus is used for film deposition
as well as etching.
[0003] Recent semiconductor elements are required to be processed
with high accuracy as the structure of semiconductor elements
becomes finer. Therefore, a new technology is also required to
improve the dimensional accuracy of a masking pattern in order to
process the etched material highly accurately. As a method of
controlling dimensions in forming a pattern of the masking
material, a technology using an anti-reflective film such as BARC
(bottom anti-reflective coating) is used in order to prevent
reflection of light such as ultraviolet light and to expose finely
and accurately. In general, the anti-reflective film is a film made
of a material which is the same organic group as a material used
for the resist, and the anti-reflective film is etched by a
fluorocarbon group gas or a halogen group gas mixed with oxygen,
and the selective ratio of the anti-reflective film material to the
masking material at processing the anti-reflective film is nearly
1. Further, edge portions of the masking pattern are apt to be cut
down by sputtering at the etching, which is a trouble at processing
the base etched material. (Refer to FIG. 3 (b))
SUMMARY OF THE INVENTION
[0004] In order to solve the above-mentioned new problem, an object
of the present invention is to provide a surface processing
apparatus and a surface processing method in which the selective
ratio, that is, a ratio of etching rate of the organic group film
such as the BARC to the film made of the same group material such
as the resist is increased, and the surface processing is performed
while an initial shape of the resist is changed as small as
possible.
[0005] The present invention is characterized by an apparatus of
processing a sample surface comprising a vacuum chamber; a means
for generating a plasma in the vacuum chamber; a sample table for
mounting a sample to be performed with surface processing using the
plasma; and an electric power supply for applying a radio frequency
bias to the sample, the surface processing of the sample being
performed using a masking material and an anti-reflective film,
which further comprises a means for introducing a mixed gas of
hydrogen gas and a deposition gas as an etching gas into the vacuum
chamber.
[0006] Further, the present invention is characterized by a method
of processing a sample surface which performs surface processing of
a sample by using a plasma by generating the plasma in a vacuum
chamber; applying a radio frequency bias to a sample table mounting
the sample; using a masking material and an anti-reflective film,
the method comprising the step of introducing a mixed gas of
hydrogen gas and a deposition gas as an etching gas into said
vacuum chamber.
[0007] Further, the present invention is characterized by that an
amount of the deposition gas added to the hydrogen gas is set to an
amount E0 at which a cut-down amount of the masking material
becomes zero.
[0008] According to the present invention, the anti-reflective film
can be highly accurately etched by using a light element of
hydrogen as the etching gas to reduce the cut-down amount of edges
of the masking material of resist caused by sputtering and at the
same time by mixing the deposition gas with the hydrogen gas to
increase the selective ratio of the anti-reflective film to the
masking material of resist.
BRIEF DESCRIPTION OF DRAWINGS
[0009] FIG. 1 is a diagram showing the overall construction of an
etching apparatus to which the present invention is applied.
[0010] FIG. 2 is a graph showing the relationship between the
etching rates of a BARC and a resist depending on the added amount
of a deposition gas.
[0011] FIG. 3 is a view showing differences in etched shapes
depending on presence or absence of an etching gas and a deposition
gas.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] Embodiments of the present invention will be described
below.
[0013] FIG. 1 is a schematic diagram showing a plasma etching
apparatus to which the present invention is applied. The apparatus
is a plasma etching apparatus utilizing electron cyclotron
resonance. A coil 2 for generating a magnetic field for the
electron cyclotron resonance (ECR) is arranged around an etching
chamber 1 of vacuum chamber. An etching gas is supplied through a
gas supply pipe 4 which is connected to a gas source through a mass
flow controller 3, and introduced into the etching chamber 1 from a
gas supply plate 5 made of silicone or glass form carbon having
several hundreds fine holes having a diameter of 0.4 to 0.5 mm.
[0014] A disk-shaped antenna 6 for radiating a microwave of the UHF
band is arranged above the gas supply plate 5, and the microwave to
the antenna 6 is transmitted from an electric power supply 7
through a matching circuit 8 and a guide tube 9. The microwave is
radiated from the periphery of the antenna 6, and a resonance
electric field in a space above the antenna 6 is introduced into
the etching chamber through a dielectric body 10. The frequency of
the microwave is selected a value from a band which can heat the
plasma up to a low electron temperature of 0.25 eV to 1 eV, that
is, it is within a range of 300 MHz to 1 GHz. In the present
embodiment, a frequency band near 450 MHz was used. Quartz or
alumina may be used for the dielectric body 10. Otherwise, a
heat-resistant polymer having a small dielectric loss such as
polyimide may be used.
[0015] A wafer mounting electrode 11 is arranged below the gas
supply plate 5, and a wafer 12 is supported on the wafer mounting
electrode by electrostatic attraction (an electric power supply for
the electrostatic attraction is not shown). In order to draw the
ions in the plasma into the wafer 12, a radio frequency bias is
applied to the wafer mounting electrode 11 from a radio frequency
electric power supply 13.
[0016] Temperature of the antenna 6 and an inner wall 14 of the
etching chamber are controlled. That is, the temperature is
controlled by introducing a coolant into the antenna 6 and the
inner wall 14 of the etching chamber from a temperature controller,
not shown, to maintain the antenna 6 and the inner wall 14 at a
constant temperature. In the present embodiment, the temperature is
controlled so that the antenna 6 and the inner wall 14 was
maintained at a temperature of 30 to 80.degree. C.
[0017] A turbo molecular pump having an evacuating speed of 2000 to
3000 L/s is arranged in a vacuum chamber directly connected to the
etching chamber 1. A conductance valve, not shown, for controlling
the evacuation speed is arranged at an opening portion of the turbo
molecular pump to adjust the evacuation speed in order to attain a
flow rate and a pressure suitable for the etching. Further, a stop
valve is provided in order to isolate the turbo molecular pump at
opening the etching chamber to atmosphere.
[0018] An embodiment of BARC etching using the plasma etching
apparatus in accordance with the present invention will be
described below.
[0019] A wafer is loaded from a transfer chamber into the etching
chamber 1 under a condition evacuated to a high vacuum using a
transfer arm, not shown, and transferred onto the wafer mounting
electrode 11. After the transfer arm is drawn back and a valve
between the etching chamber 1 and the transfer chamber is closed,
the wafer mounting electrode 11 is moved upward and stopped at a
position suitable for etching. In the case of the present
embodiment, the distance between the wafer 12 and the gas
introducing plate 5 (distance between the electrodes) was set to 50
mm to 100 mm.
[0020] A mixed gas of H.sub.2 and N.sub.2 was used as the etching
gas, and H.sub.2 and N.sub.2 were introduce at the flow rates of
100 sccm and 5 sccm, respectively. CHF.sub.3 was added to the mixed
gas as a deposition gas. The output power of the UHF microwave
electric power supply was set to 1.5 kW, and the output power of
the bias electric power supply 12 to the wafer was set 60 W. A
resonance magnetic field of 0.016 T of UHF microwave 450 MHz was
generated between the gas supply plate 5 and the wafer mounting
electrode 11 (that is, the wafer 12). Then, the microwave electric
power supply 7 was operated. Thereby, a strong plasma was generated
in the ECR region of the magnetic field intensity of 0.016 T by the
electron cyclotron resonance.
[0021] It is necessary that the incident ion density on the surface
of the wafer 12 is made uniform in order to make the etching
property uniform. An optimal ion density distribution can be
obtained because the ECR position can be freely adjusted using the
magnetic field coil 2. In the present embodiment, the shape of the
ECR region was formed in a convex state to the wafer 12 side.
[0022] After the plasma is ignited, a high voltage is applied to
the wafer electrode 11 from a direct current electric power supply,
not shown, connected to the radio frequency electric power supply
13 in parallel to electrostatically attract the wafer 12 onto the
wafer mounting electrode 11. Helium gas is introduced to the
backside surface of the elecrostatically attracted wafer 12, and
temperature control of the wafer is performed between the wafer
mounting surface of the wafer mounting electrode 11
temperature-controlled by a coolant and the wafer through the
helium gas.
[0023] Next, the radio frequency electric power supply 13 is
operated to apply the radio frequency bias to the wafer mounting
electrode 11. By doing so, ions are vertically incident to the
wafer 12 from the plasma. When the bias voltage is applied to the
wafer 12, etching is initiated. The etching is terminated in a
preset etching time. Otherwise, the change in a light emission
intensity of the plasma caused by a reaction product is monitored,
and an etching termination time is obtained by judging the etching
termination, and then the etching is terminated after performing
appropriate over-etching. The termination of etching is the time
when the application of the radio frequency bias voltage is
stopped. At the same time, the supply of the etching gas is also
stopped.
[0024] Next, a process to detach the electrostatically attached
wafer 12 from the wafer mounting electrode 10 is necessary, and in
this process argon or a kind of gas actually used in the etching is
used as a discharging gas. After stopping the supply of the
electrostatic attracting voltage and the power supply line is
grounded, the discharging is performed for approximately 10 seconds
while the microwave is being discharged. By doing so, the charge on
the wafer 12 is removed to the ground through the plasma, and
consequently the wafer 12 can be easily detached. After completion
of the discharging process, the supply of the discharging gas is
stopped and the supply of the microwave is also stopped. Further,
the current supply to the coil 2 is also stopped. The level of the
wafer mounting electrode 11 is lowered down to the wafer transfer
position.
[0025] After that, the etching chamber 1 is evacuated to a high
vacuum for a while. At the time when the high vacuum evacuation is
completed, the valve between the transfer chamber and the etching
chamber is opened and the transfer arm is inserted to receive and
unload the wafer 12. When there is a next wafer to be etched, the
new wafer is loaded and the etching is performed according to the
above-mentioned procedure.
[0026] The above is a typical flow of the etching process.
[0027] An effect of adding a deposition gas will be briefly
described below. FIG. 2 is a graph showing the relationship between
the added amount of CHF.sub.3 of one of deposition gases and the
etching rates of a BARC and a resist depending on, and FIG. 3 is a
view showing etched shapes.
[0028] It can be understood from FIG. 2 that as the amount of the
additive gas is increased, the etching rate of the resist 15 is
largely decreased, that is, cut down not so much though the etching
rate of the BARC 16 is decreased not so much. However, when the
amount of the additive gas exceeds a a value, the resist 15 is
accumulated to the contrary. Therefore, at an added amount E0 of
the gas in which the cut-down amount of the resist becomes zero,
etching having the selective ratio of infinity can be performed. It
is practical that the amount of additive gas is set to a value
around the amount E0 and within a range in which a selective ratio
of the anti-reflective film to the masking material is larger than
2.
[0029] FIG. 3 (a) a view showing an initial shape of a sample to be
etched. FIG. 3 (b) a comparative view showing an etched shape which
is etched through a conventional technology, that is, using a mixed
gas of halogen and O.sub.2 as the additive gas. In the conventional
technology, edge cutting-down appears at an opening portion of the
resist.
[0030] On the other hand, in an embodiment of the present
invention, that is, in a case where hydrogen is used as the main
etching gas and no additive gas is not mixed, an etched shape
becomes as shown in FIG. 3 (c). Edge cutting-down at an opening
portion is reduced compared to that in the conventional technology
because a light element of hydrogen is used as the main etching
gas. Further, by mixing an additive gas to hydrogen
(H.sub.2+CHF.sub.3), etching with edge cutting-down of the resist
can be performed.
[0031] In regard to the adding amount of CHF.sub.3 in the present
embodiment, the flow rate of CHF.sub.3 was varied from 0 sccm to 2
sccm and 8 sccm against the flow rates of H.sub.2 of 100 sccm and
N.sub.2 of 5 sccm. The cut-down amounts of the resist of masking
material after etching the BARC having a film thickness of 80 nm
under the above conditions were 120 nm to the initial film
thickness of 720 nm when the added amount of CHF.sub.3 was zero,
and 0 nm when the added amount of CHF.sub.3 was 2 sccm. On the
contrary, when the added amount of CHF.sub.3 was 8 sccm, the
sedimentation was 83 nm. Therefore, by etching the BARC under the
condition of the added amount of CHF.sub.3 E0=2 sccm, etching of
the selective ratio to the masking material of infinity can be
performed. Further, because the light element of hydrogen is used
as the main gas of the etching gas, the cut-down amount of edges of
the opening portion of the resist caused by sputtering is very
small.
[0032] The reason why the resist is not cut down but only the
etching reaction of the BARC made of the same kind material is
progressed is considered that by introducing CHF.sub.3 as the
deposition gas, a CH group sediment having a strong deposition
property is accumulated only on the resist surface so much as to
inhibit the etching reaction. Although the present embodiment has
been described on the premise that CHF.sub.3 is used as the
deposition gas, the deposition gas is not limited to CHF.sub.3, and
any gas capable of producing a CH group sediment which reacts with
hydrogen and has a high adhesive coefficient may be used.
[0033] Although the present embodiment has been described on the
premise that the UHF type ECR plasma etching apparatus is used, the
apparatus is not limited to the UHF type ECR plasma etching
apparatus, and the other plasma source may be used. Therefore, the
present invention can be applied to an induction type plasma
apparatus other than the microwave type.
[0034] Further, although the temperature control in the embodiment
is performed using a coolant, it is not limited to the coolant, and
water cooling, forced cooling by gas, or use of a heater, lamp
heating using infrared rays may be used.
[0035] As described above, in the present invention, the selective
ratio of the BARC (the anti-reflective film) to the resist of mask
made of the same group material can be increased, and at the same
time the BARC can be etched with maintaining the initial shape of
the resist by the effect of using the etching gas mainly composed
of the light element of hydrogen and adding the deposition gas.
[0036] As having been described above, according to the present
invention, an organic material such as the material of BARC can be
etched with a high selective ratio to the same find of materials
used for the resist or the like and with maintaining the initial
shape of the resist. That is, the sputtering property in the edge
portions of the mask is reduced by using the light element of
hydrogen as the etching gas, and the selective ratio of the BARC
material to the masking material can be increased by mixing the
deposition gas with the etching gas. By the synergistic effect, an
anti-reflective film can be etched with a high selective ratio
while an initial shape of the resist is changed as small as
possible.
* * * * *