U.S. patent application number 09/940882 was filed with the patent office on 2002-01-31 for method of plasma etching.
Invention is credited to Nawata, Makoto, Tamura, Tomoyuki, Yakushiji, Mamoru.
Application Number | 20020011464 09/940882 |
Document ID | / |
Family ID | 26346898 |
Filed Date | 2002-01-31 |
United States Patent
Application |
20020011464 |
Kind Code |
A1 |
Nawata, Makoto ; et
al. |
January 31, 2002 |
Method of plasma etching
Abstract
A plasma etching system using a ground electrode made of silicon
carbide and a cover made of a dielectric material not containing
aluminum, where the cover is laid over the substrate electrode,
thereby preventing aluminum from being produced out of these parts
and reducing device damage. Namely, a plasma etching system has a
substrate electrode mounted in a vacuum process chamber, a ground
electrode and a plasma generating source, and uses plasma to
provide etching of substrates mounted on said substrate electrode.
The plasma etching system is characterized in that the ground
electrode is made of carbon or silicon carbide, and the dielectric
material containing a Si compound covers the surface portion of the
substrate electrode facing inside the substrate installation
portion of the vacuum process chamber, except for the substrate
installation portion.
Inventors: |
Nawata, Makoto;
(Kudamatsu-shi, JP) ; Yakushiji, Mamoru;
(Kudamatsu-shi, JP) ; Tamura, Tomoyuki;
(Kudamatsu-shi, JP) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
26346898 |
Appl. No.: |
09/940882 |
Filed: |
August 29, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09940882 |
Aug 29, 2001 |
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09866702 |
May 30, 2001 |
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09866702 |
May 30, 2001 |
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09487303 |
Jan 19, 2000 |
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Current U.S.
Class: |
216/67 ; 216/71;
216/79; 257/E21.312 |
Current CPC
Class: |
H01J 37/32009 20130101;
H01L 21/32137 20130101; H01J 37/32532 20130101; H01J 37/32192
20130101 |
Class at
Publication: |
216/67 ; 216/71;
216/79 |
International
Class: |
C23F 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 20, 1999 |
JP |
11-011471 |
Claims
What is claimed is:
1. A method for plasma etching a substrate, comprising: placing the
substrate, to be plasma etched, in a processing chamber having a
ground electrode and a substrate electrode, the substrate being
mounted on a portion of the substrate electrode; and generating a
plasma in the processing chamber, in an etching gas, and etching
the substrate by said plasma, wherein the ground electrode is made
of carbon or silicon carbide, and wherein a dielectric material
containing a silicon compound covers a portion of the surface of
the substrate electrode, except for the portion of the substrate
electrode upon which the substrate is mounted.
2. The method according to claim 1, wherein the etching gas
includes at least one of chlorine and hydrogen bromide gas.
3. The method according to claim 1, wherein said substrate includes
silicon to be etched.
Description
[0001] This application is a Divisional application of Ser. No.
09/866,702, filed May 30, 2001, which is a Continuation application
of Ser. No. 09/487,303, filed Jan. 19, 2000.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a plasma etching system
using a plasma for etching of substrates mounted on a substrate
electrode. More specifically, this invention relates to a plasma
etching system which uses chlorine gas (Cl.sub.2) alone or hydrogen
bromide gas (HBr) alone, or a mixture of chlorine gas (Cl.sub.2)
and oxygen gas (O.sub.2) or of hydrogen bromide gas (HBr) and
oxygen gas (O.sub.2) as an etching gas to provide silicon
etching.
[0003] A microwave plasma etching system, for example, is known
which uses chlorine gas (Cl.sub.2) alone or hydrogen bromide gas
(HBr) alone, or a mixture of chlorine gas (Cl.sub.2) and oxygen gas
(O.sub.2) or of hydrogen bromide gas (HBr) and oxygen gas (O.sub.2)
as an etching gas to provide silicon etching.
[0004] To prevent substrates from being contaminated by iron (Fe),
chromium (Cr) and nickel (Ni), a microwave plasma etching system
uses aluminum as the material of the electrode having a ground
potential (ground electrode), in place of the material containing
these impurities. To prevent the electrode from being damaged or
worn by a chlorine gas (Cl.sub.2) plasma or hydrogen bromide gas
(HBr) plasma, the surface of the aluminum (Al) is further treated
with anode oxidation (aluminized treatment). To prevent the
substrate electrode from being damaged or worn, the substrate
electrode, except for the substrate installation portion, is
covered with aluminum oxide (alumina), which acts as a dielectric
material.
[0005] Prior plasma etching systems do not take into account the
metallic contamination by aluminum (Al) generated out of the
components of the etching process chamber. Metallic contamination
of substrates by aluminum (Al) resulting from etching has occurred
in recent highly integrated devices, especially the devices
containing minute gates, thereby causing the interface state to be
increased.
SUMMARY OF THE INVENTION
[0006] An object of the present invention is to provide a plasma
etching system in which it is possible to avoid metallic
contamination by aluminum (Al) as well as metallic contamination by
iron (Fe), chromium (Cr) and nickel (Ni), and to suppress device
damage.
[0007] Aluminum (Al) contamination has been found to be caused by a
ground electrode made of aluminum (Al) and the cover (alumina) laid
over the substrate electrode, according to an analysis made by the
present inventors, namely, according to an evaluation of metallic
contamination using total reflection X-ray fluorescence
spectrometry.
[0008] This shows that the object of the present invention can be
achieved by using a ground electrode made of silicon carbide and a
cover made of a dielectric material that does not contain aluminum
(Al) where the cover is laid over the substrate electrode. This
prevents aluminum (Al) from being produced out of these parts.
[0009] The present invention is characterized by a plasma etching
system comprising a substrate electrode mounted in a vacuum process
chamber, a ground electrode and a plasma generating source, wherein
plasma is used to provide etching of substrates mounted on the
substrate electrode. In accordance with the invention, the ground
electrode is made of carbon or silicon carbide, and a dielectric
material containing a Si compound covers the surface portion of the
substrate electrode facing inside the substrate installation
portion of the vacuum process chamber, except for the substrate
installation portion itself.
[0010] The present invention prevents metallic impurities (Fe, Cr.
Ni and Al) from being generated out of the components of the
etching process chamber, thereby reducing device damage.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a vertical cross sectional view of a microwave
plasma etching system representing one embodiment of the present
invention;
[0012] FIG. 2 is a transverse sectional view of the etching process
chamber in FIG. 1;
[0013] FIG. 3 is a cross sectional view of a substrate immediately
before etching by the system in FIG. 1;
[0014] FIG. 4 is a cross sectional view of a substrate immediately
after etching by the system in FIG. 1;
[0015] FIG. 5 is a vertical cross sectional view of a microwave
plasma etching system representing another embodiment of the
present invention;
[0016] FIG. 6 is a transverse sectional view of the etching process
chamber in FIG. 5; and
[0017] FIG. 7 is a diagram showing the relationship between the
ground electrode and substrate installation surface of the
substrate electrode in accordance with the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0018] One embodiment of the present invention will be described
with reference to FIGS. 1 and 2.
[0019] FIG. 1 is a cross sectional view of a microwave plasma
etching system, while FIG. 2 is a transverse sectional view of the
etching process chamber in FIG. 1.
[0020] Microwaves generated by magnetron 1 are transferred to
waveguide 2 and launched into etching process chamber 4 through
bell jar 3. The etching process chamber 4 comprises the quartz bell
jar 3, a substrate electrode 5, a quartz-made electrode cover 6 and
silicon carbide-made ground electrode 7. The electrode portion of
the substrate electrode 5 is made of a material containing
aluminum. The etching process chamber 4 incorporates a magnetic
field generating DC power supply 8, a solenoid coil 9 and a gas
supply unit 10.
[0021] Gas fed to the etching process chamber 4 from the gas supply
unit 10 is turned into a plasma by the electric field formed by the
microwave (electric field) and the magnetic field formed by the
direct current supplied to the solenoid coil 9 from the magnetic
field generating DC power supply 8. A substrate 11 is etched by the
plasma. The etching pressure is controlled by a vacuum exhaust unit
12. The energy of the ions incident on the substrate 11 is
controlled by the radio-frequency power supplied to the substrate
electrode 5 from a radio-frequency power source 13.
[0022] FIG. 3 is a cross sectional view of a substrate immediately
before etching by the system in FIG. 1. The substrate 11 has an
oxide film 15 and a polycrystalline silicon layer 16 formed on the
silicon substrate 14, and mask 17 is patterned on the
polycrystalline silicon layer 16. A mixture of Cl.sub.2 and O.sub.2
is used as the etching gas. The etching gas is turned into a plasma
by the magnetic field and microwave electric field, and the
polycrystalline silicon layer 16 of the substrate 11 mounted on the
substrate electrode 5 is etched by ions and radicals in the plasma.
In this case, the energy of the ions in the plasma incident on the
substrate 11 is controlled by radio-frequency power having a
frequency of 800 Hz supplied from the radio-frequency power source
13.
[0023] FIG. 4 is a cross sectional view of a substrate immediately
after etching. When the oxide film 15 is etched upon completion of
etching of the polycrystalline silicon layer 16, the incident
energy of ions in the plasma is reduced by decreasing the
radio-frequency power supplied from the radio-frequency power
source 13 in order to control the yield of the etching of the oxide
film 15.
[0024] The present invention uses the quartz-made electrode cover 6
and the silicon carbide-made ground electrode 7 to ensure that iron
(Fe), chromium (Cr), nickel (Ni) and aluminum (Al) as metallic
impurities of the substrate are not generated from the electrode
cover 6 and ground electrode 7 at the time of etching.
[0025] As disclosed above, the present invention prevents metallic
impurities (Fe, Cr, Ni and Al) from being generated out of the
components of the etching process chamber.
[0026] Another embodiment of the present invention will be
described.
[0027] Similarly to the previous embodiment, this embodiment uses
the microwave plasma etching system shown in FIGS. 1 and 2 to etch
the polycrystalline silicon gate structure. The substrate 11 before
etching has an oxide film 15 and polycrystalline silicon layer 16
formed on the silicon substrate 14, as shown in the cross sectional
view of FIG. 3. The mask 17 is patterned on the polycrystalline
silicon layer 16. A mixture of HBr and O.sub.2 is used as the
etching gas, and the etching gas is turned into a plasma by the
magnetic field and microwave electric field. The polycrystalline
silicon layer 16 of the substrate 11 is etched by ions and radicals
in the plasma. In this case, the energy of the ions in the plasma
incident on the substrate 11 is controlled by the 800 kHz
radio-frequency power supplied from the radio-frequency power
source 13.
[0028] FIG. 4 is a cross sectional view of the substrate 11
immediately after etching. In order to control the yield of etching
of the oxide film 15 upon completion of etching of the
polycrystalline silicon layer 16, the energy of incident ions in
the plasma is reduced by decreasing the radio-frequency power
supplied from the radio-frequency power source 13. The quartz-made
electrode cover 6 and the silicon carbide-made ground electrode 7
are used to ensure that iron (Fe), chromium (Cr) or nickel (Ni) and
aluminum (Al) as metallic impurities are not generated from the
electrode cover 6 and ground electrode 7 at the time of
etching.
[0029] As disclosed above, the present invention prevents metallic
impurities (Fe, Cr, Ni and Al) from being generated out of the
components of the etching process chamber.
[0030] Still another embodiment of the present invention will be
described with reference to FIG. 5 and FIG. 6.
[0031] FIG. 5 is a cross sectional view of a microwave plasma
etching system. FIG. 6 is a transverse sectional view of the
etching process chamber in FIG. 5.
[0032] Microwaves generated by the magnetron 18 are transferred to
waveguide 19 and launched into the etching process chamber 21
through quartz-made window 20. The etching process chamber 21 is
composed of a quartz-made inner cylinder 22, an aluminum-made
vacuum vessel 23, a substrate electrode 24, the quartz-made
electrode cover 25 and the silicon carbide-made ground electrode
26. Gas fed from the gas supply unit 29 is turned into a plasma by
a microwave electric field and a magnetic field formed by the
direct current supplied to the solenoid coil 28 from the DC power
supply 27. Substrate 30 is etched by the plasma, and the pressure
during etching is controlled by the vacuum exhaust unit 31. The
energy of the ions incident on the substrate 30 is controlled by
the radio-frequency power applied to the substrate electrode 24
from the radio-frequency power source 32.
[0033] Etching of the substrate 30 is carried out using the same
steps as those for the above disclosed embodiment. The etching
process chamber is composed of a quartz-made inner cylinder 25 and
a silicon carbide-made ground electrode 26 to ensure that iron
(Fe), chromium (Cr) or nickel (Ni) and aluminum (Al) as metallic
impurities are not generated from the electrode cover 25 and ground
electrode 27 at the time of etching.
[0034] These measures according to the present invention avoid
contamination by metals (Fe, Cr, Ni and Al) coming out of the
components of the etching process chamber.
[0035] The above embodiment has been used to explain the effect of
using a quartz-made electrode cover. The same effect can be
obtained when a silicon nitride cover is used.
[0036] To control the energy of ions incident on the substrate, it
is preferred that the ground electrode is clearly visible from the
substrate electrode; in other words, the ground electrode
preferably should have a sufficient area. As shown in FIG. 7, it is
preferred to meet the conditions of Es/Ws>2, where the substrate
area is Ws, and the ground electrode area is Es. If the substrate
area Ws is increased, the preferred ground electrode area must be
increased accordingly. From the view point of the ground area,
there is no upper limit to the ratio Es/Ws, but the ratio Es/Ws is
limited by other structural restrictions of the etching process
chamber.
[0037] As shown in FIG. 7, the bottom end face of the ground
electrode is preferably almost as high as the substrate
installation surface of the substrate electrode, or extended
slightly below the installation surface. By way of example, the
height of the ground electrode h is about 45 to 70 mm. The ground
electrode as a whole preferably constitutes a part of the inner
wall of the vacuum process chamber at the inclined upward position
on the outside in the radial direction of the substrate
installation surface of the substrate electrode.
[0038] Radio-frequency power supplied to the substrate electrode
described with reference to this embodiment is preferably not to
exceed 2 MHz, or is more preferably within the range from 400 to
800 kHz. The same effect can be obtained even when time modulation
bias is applied to this radio-frequency (13, 32).
[0039] The effect of the microwave plasma etching system has been
described with reference to this embodiment. The same effect can
also be gained according to other discharging methods, for example,
Helicon Type and TCP (Transform Coupled Plasma) methods.
[0040] As disclosed above, the present invention prevents metallic
impurities (Fe, Cr, Ni and Al) from being generated out of the
components of the etching process chamber, thereby suppressing
device damage.
* * * * *