U.S. patent application number 10/083252 was filed with the patent office on 2003-08-28 for plasma processing method and apparatus.
Invention is credited to Kanai, Saburou, Kanekiyo, Tadamitsu, Kawaguchi, Tadayashi, Mitsuda, Akihiko, Shimada, Takeshi.
Application Number | 20030160024 10/083252 |
Document ID | / |
Family ID | 27753261 |
Filed Date | 2003-08-28 |
United States Patent
Application |
20030160024 |
Kind Code |
A1 |
Kawaguchi, Tadayashi ; et
al. |
August 28, 2003 |
Plasma processing method and apparatus
Abstract
In a plasma processing method which comprises supplying a
processing gas to a vacuum vessel 2 forming a plasma production
part, producing a plasma 6 using an antenna 1 and a Faraday shield
8 which are provided at outer periphery of the vacuum vessel and to
which a high-frequency electric power can be applied, and carrying
out the processing, a voltage of at least 500 V is applied to the
Faraday shield 8 and a sample 12 which is disposed in the vacuum
vessel 2 and which is a nonvolatile material as a material to be
etched is etched.
Inventors: |
Kawaguchi, Tadayashi;
(Kudamatsu, JP) ; Kanekiyo, Tadamitsu; (Kudamatsu,
JP) ; Mitsuda, Akihiko; (Kudamatsu, JP) ;
Shimada, Takeshi; (Hikari, JP) ; Kanai, Saburou;
(Hikari, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET
SUITE 1800
ARLINGTON
VA
22209-9889
US
|
Family ID: |
27753261 |
Appl. No.: |
10/083252 |
Filed: |
February 27, 2002 |
Current U.S.
Class: |
216/63 |
Current CPC
Class: |
H01J 37/32862 20130101;
H01J 37/321 20130101 |
Class at
Publication: |
216/63 |
International
Class: |
C23F 001/00; B44C
001/22; C03C 015/00; C03C 025/68 |
Claims
What is claimed is:
1. A plasma processing method which comprises supplying a
processing gas to a vacuum vessel forming a plasma production part,
producing a plasma using an antenna and a Faraday shield which are
provided at outer periphery of the vacuum vessel and to which a
high-frequency electric power can be applied, and carrying out the
processing, wherein a voltage of at least 500 V is applied to the
Faraday shield and a sample which is disposed in the vacuum vessel
and which is a nonvolatile material as a material to be etched is
etched.
2. A plasma processing method which comprises supplying a
processing gas to a vacuum vessel forming a plasma production part,
producing a plasma using an antenna and a Faraday shield which are
provided at outer periphery of the vacuum vessel and to which a
high-frequency electric power can be applied, and carrying out the
processing, wherein a voltage of at least 500 V is applied to the
Faraday shield and reaction products deposited on the inner wall of
the vacuum vessel are cleaned.
3. A plasma processing method according to claim 2, wherein the
processing gas is a mixed gas comprising boron trichloride and
chlorine.
4. A plasma processing method according to claim 3, wherein the
processing gas is supplied so that the mixed gas comprises 20% of
boron trichloride and 80% of chlorine, thereby cleaning the inner
wall of the vacuum vessel.
5. A plasma processing method according to claim 2, wherein a
voltage of at least 1500 V is applied to the Faraday shield.
6. A plasma processing method which comprises supplying a
processing gas to a vacuum vessel forming a plasma production part,
producing a plasma using an antenna and a Faraday shield which are
provided at outer periphery of the vacuum vessel and to which a
high-frequency electric power can be applied, and carrying out the
processing, wherein the method comprises the first step of carrying
a dummy wafer onto a sample stand, applying a voltage of at least
500 V to the Faraday shield and removing foreign matters in the
vacuum vessel with a plasma using a gas containing chlorine, the
second step of etching a sample which is disposed on the sample
stand in the vacuum vessel and which is a nonvolatile material as a
material to be etched after the first step, and the third step of
applying a voltage of at least 1500 V to the Faraday shield after
the second step, and removing reaction products in the vacuum
vessel using a mixed gas comprising boron trichloride and
chlorine.
7. A plasma processing method which comprises supplying a
processing gas to a vacuum vessel forming a plasma production part,
producing a plasma using an antenna and a Faraday shield which are
provided at outer periphery of the vacuum vessel and to which a
high-frequency electric power can be applied, and carrying out the
processing, wherein the number of foreign matters in the vacuum
vessel is detected by a monitor for foreign matters, cleaning by
applying a voltage to the Faraday shield is carried out in case the
number of foreign matters exceeds a given upper limit and the
cleaning is terminated in case the number of foreign matters
decreases below a given lower limit.
8. An apparatus for plasma processing which has a vacuum vessel
forming a plasma producing part, a gas supplying means for
supplying a gas to the vacuum vessel, an antenna generating an
electric field in the plasma producing part, a Faraday shield
provided at outer periphery of the vacuum vessel, a high-frequency
electric source supplying a high-frequency electric power to the
antenna and the Faraday shield, and an end point determination and
detection means, said end point determination and detection means
detecting the end point of cleaning of the inner wall of the vacuum
vessel by detecting emission wavelength of reaction products.
9. An apparatus for plasma processing which has a vacuum vessel
forming a plasma producing part, a gas supplying means for
supplying a gas to the vacuum vessel, an antenna generating an
electric field in the plasma producing part, a Faraday shield
provided at outer periphery of the vacuum vessel, a high-frequency
electric source supplying a high-frequency electric power to the
antenna and the Faraday shield, and an end point determination and
detection means, said end point determination and detection means
detecting the end point of cleaning of the inner wall of the vacuum
vessel by detecting emission wavelength of a material of the vacuum
vessel.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a plasma processing method
which comprises carrying out etching of samples and cleaning of
inner wall of vacuum vessels with plasma.
[0002] In the field of production of semiconductor devices,
nonvolatile materials are being used as materials to be etched for
FRAM (Ferroelectric Random Access Memory) or MRAM (Magnetic Random
Access Memory) in addition to materials such as Si, Al and
SiO.sub.2 which have been used as materials to be etched for DRAM
(Dynamic Random Access Memory) or LOGIC. The nonvolatile materials
are difficult to etch because reaction products at the time of
etching are high in melting point. Furthermore, since reaction
products after etching are low in vapor pressure and high in
coefficient of adhesion to inner wall of vacuum vessels, when
several to several hundred samples are processed, the inner wall of
the vacuum vessels is covered with deposits, which peel off later
to cause formation of many foreign matters. Moreover, the coupling
state of an induction antenna and plasma in the reaction vessel is
changed by the deposits to cause change with time of etching speed
or uniformity, verticality of etching, and state of adhering of
side wall to the etched side wall. As examples of the nonvolatile
materials, mention may be made of ferromagnetic materials or
antiferromagnetic materials used for MRAM or magnetic heads, such
as Fe, NiFe, PtMn and IrMn, noble metal materials used for
capacitor part or gate part of DRAM, capacitor part of FRAM or
element part of TMR (Tunneling Magneto Resistive) of MRAM, such as
Pt, Ir, Au, Ta, Ru, and, besides, high dielectric materials such as
Al.sub.2O.sub.3, HfO.sub.3 and Ta.sub.2O.sub.3, ferroelectric
materials such as PZT (lead titanate zirconate), BST (barium
strontium titanate) and SBT (strontium bismuth tantalate).
[0003] As one of conventional plasma processing methods and
processing apparatuses, there has been an induction type plasma
processing apparatus using a coil-shaped antenna provided at outer
periphery of a vacuum vessel or a plasma processing apparatus into
which a microwave is introduced. In both the apparatuses, the
countermeasure against deposits on the inner wall of the vacuum
vessel in etching of nonvolatile materials is not sufficient, and,
hence, cleaning with atmospheric exposure has been repeatedly
carried out. When cleaning is carried out once, 6-12 hours are
required before starting of next processing of the sample to cause
deterioration of working efficiency of the apparatuses.
[0004] On the other hand, there has been proposed an apparatus
according to which a Faraday shield is provided between antenna and
plasma and electric power is supplied by connecting a
high-frequency electric source to the Faraday shield, whereby
deposition of reaction products on the inner wall of vacuum vessel
is inhibited and cleaning of the inner wall of the vacuum vessel
can be performed. As examples thereof, there are techniques
disclosed in JP-A-10-275694 and JP-A2000-323298.
SUMMARY OF THE INVENTION
[0005] The above prior art have not made sufficient investigations
on etching method and cleaning method.
[0006] Therefore, the object of the present invention is to provide
a plasma processing method and a plasma processing apparatus
according to which deposition of reaction products on the inner
wall of a vacuum vessel in the processing of samples can be
inhibited or the deposited reaction products can be efficiently
removed in the plasma processing apparatus in which a Faraday
shield is provided between an induction antenna and plasma.
[0007] The present invention employs the following method and
apparatus for attaining the above object.
[0008] In a plasma processing method where a processing gas is
supplied to a vacuum vessel which forms a plasma production part
and plasma is produced using an antenna and a Faraday shield which
are provided at an outer periphery of the vacuum vessel and to
which a high-frequency electric power can be applied, whereby the
processing is carried out, a voltage of at least 500 V is applied
to the Faraday shield to carry out etching of a sample which is
disposed in the vacuum vessel and which is a nonvolatile material
as a material to be etched.
[0009] In an apparatus for plasma processing which has a vacuum
vessel forming a plasma producing part, a gas supplying means for
supplying a gas to the vacuum vessel, an antenna generating an
electric field in the plasma producing part, a Faraday shield
provided at outer periphery of the vacuum vessel, a high-frequency
electric source supplying a high-frequency electric power to the
antenna and the Faraday shield, and an end point determination and
detection means, the end point determination and detection means
detects the end point of cleaning of the inner wall of the vacuum
vessel by detecting emission wavelength of reaction products or a
material of the vacuum vessel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a sectional view of a plasma processing apparatus
used in the present invention.
[0011] FIG. 2 is a schematic view of a Faraday shield used in the
present invention.
[0012] FIG. 3 is a graph which shows a relation between Faraday
shield voltage and sheath voltage.
[0013] FIG. 4 is a graph which shows a relation between Faraday
shield voltage and cleaning speed and deposition speed of reaction
product.
[0014] FIG. 5 is a diagram which shows the plasma processing method
of the present invention.
[0015] FIG. 6 is a graph which shows a relation between the number
of processed samples and etching speed of Au.
[0016] FIG. 7 is a graph which shows a relation between the number
of processed samples and etching speed of Ta.
[0017] FIG. 8 is a graph which shows a relation between the number
of processed samples and etching speed of Pt.
[0018] FIG. 9 is a diagram which shows a method of determination of
end point in the present invention.
[0019] FIG. 10 is a diagram which shows a method of determination
of end point in the present invention.
[0020] FIG. 11 is a diagram which shows the plasma processing
method of the present invention.
[0021] FIG. 12 is a diagram which shows results of cleaning
according to the present invention.
[0022] FIG. 13 is a diagram which shows results of cleaning
according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] The present invention will be explained below, referring to
the drawings. FIG. 1 is a sectional view of a plasma processing
apparatus of the present invention. Vacuum vessel 2 has therein a
discharge part 2a which comprises an insulation material (e.g.,
non-conductive materials such as quartz, ceramics, etc.) and which
forms a plasma producing part and a processing part 2b in which a
sample 12 to be processed and an electrode 5 for placing the sample
12 thereon are disposed. The processing part 2b is grounded to an
earth and the electrode 5 is set at the processing part 2b with
interposing an insulation material between them. A coil-shaped
inductively coupled antenna 1 is disposed at outer periphery of the
discharge part 2a. Furthermore, a disc-like Faraday shield 8 which
capacitively couples with plasma 6 is provided outside the
discharge part 2a. The inductively coupled antenna 1 and the
Faraday shield 8 are connected in series to a first high-frequency
electric source 10 through a matching device (matching box) 3.
Furthermore, a circuit whose impedance can be varied is grounded to
earth in parallel with the Faraday shield 8. A processing gas is
supplied into the vacuum vessel 2 from a gas supplying device 4 and
simultaneously the pressure is reduced to a given pressure to
perform exhaustion by an exhaust device 7. The processing gas is
supplied into the vacuum vessel 2 from the gas supplying device 4,
and this processing gas is converted to plasma by the action of an
electric field generated by the inductively coupled antenna 1 and
the Faraday shield 8. A second high-frequency electric source 11 is
connected to the electrode 5. Moreover, an electric field for
production of plasma is obtained by supplying to the inductively
coupled antenna 1 and the Faraday shield 8 a high-frequency
electric power generated by the first high-frequency electric
source 10, e.g., an HF band such as 13.56 MHz, 27.12 MHz, or 40.68
MHz, or a VHF band further higher in frequency, but in order to
inhibit reflection of the electric power, impedance of the
inductively coupled antenna 1 is matched with output impedance of
the first high-frequency electric source 10 using the matching
device (matching box) 3. The matching device (matching box) 3 used
generally includes two variable condensers 9 capable of varying
electrostatic capacity which are called inverted L type.
Furthermore, in order to lead ions present in the plasma 6 to the
sample 12, a bias voltage is applied to the electrode 5 by the
second high-frequency electric source 11.
[0024] Next, the Faraday shield 8 will be explained in detail. As
shown in FIG. 2, the Faraday shield 8 comprises a metal conductor
having slits in the form of vertical stripes and is disposed in
such a manner that it is superposed upon the vacuum vessel.
Application of voltage to the Faraday shield 8 can be controlled by
the variable condenser 9c shown by VC3 in FIG. 1. Application of
voltage to the Faraday shield 8 can be set at a given value by a
processing recipe of the sample.
[0025] Next, for attaining optimization of the voltage applied to
the Faraday shield 8, the relation between the voltage applied to
the Faraday shield 8 and the sheath voltage applied to the inner
wall of the vacuum vessel was calculated through simulation.
[0026] When a high-frequency voltage Vfs is applied to the Faraday
shield 8, a direct voltage Vsh is applied to the inner wall of the
vacuum vessel. Therefore, ions in the plasma are accelerated
towards the inner wall of the vacuum vessel and strike the wall.
This ion acceleration voltage Vsh is given by the following formula
(1).
Vsh=Vfs/2*Dsh/((Dfs+Dch/.epsilon.)+Dsh)+Vs (1)
[0027] In the above formula (1), Dsh denotes thickness of a sheath
formed on the inner wall of the vacuum vessel, Dch denotes
thickness of the vacuum vessel, .epsilon. denotes a relative
dielectric constant of the vacuum vessel, and Vs denotes a plasma
space potential (normally about 15 V). The thickness Dsh of the
sheath formed on the inner wall of the vacuum vessel is given by
the following formula (2).
Dsh=1E3*(2.sup.6/4)/3*(ICF/8.85E-12).sup.-0.5*((Mi/1.602E-19).sup.-0.25*Vs-
h.sup.0.76 (2)
[0028] In the above formula (2), ICF denotes a saturated current
density of plasma and Mi denotes an ion mass. The above formulas of
Vsh and Dsh are simultaneous and have non-linear dependence.
[0029] FIG. 3 shows the relation between voltage Vfs applied to the
Faraday shield 8 and sheath voltage Vsh in the case of using
alumina vacuum vessels of 10 mm and 15 mm in thickness and a quartz
vacuum vessel of 10 mm in thickness. In this case, plasma is
chlorine plasma and saturated ionic current is 4 mA/cm.sup.2. It
can be seen that in the case of the alumina vacuum vessel of 10 mm
in thickness, when a voltage of 500 V is applied to the Faraday
shield 8, the sheath voltage is about 60 V, and when a voltage of
1500 V is applied, the sheath voltage is about 360 V. Furthermore,
in the case of an alumina vacuum vessel of 15 mm in thickness or a
quartz vacuum vessel of 10 mm in thickness, the sheath voltage
lowers to 70% and 40% of the sheath voltage obtained using the
alumina vessel of 10 mm in thickness, respectively, and it can be
seen that for obtaining the similar effects, the higher voltage
must be applied.
[0030] FIG. 4 shows deposition speed of the reaction product
deposited on the inner wall of the vacuum vessel when Pt, namely,
the material to be etched on the sample is etched in the alumina
vacuum vessel of 10 mm in thickness and further shows reaction
product cleaning speed for removing the reaction product deposited
on the inner wall of the vacuum vessel by applying a voltage to the
Faraday shield 8. It can be seen from FIG. 4 that the reaction
product deposition speed and the reaction product cleaning speed
nearly match with each other when the Faraday shield voltage is
about 500 V. That is, it can be seen that in processing of Pt, no
reaction product deposits on the inner wall of the vacuum vessel by
applying a Faraday shield voltage of about 500 V. Moreover, since
the inner wall of the vacuum vessel is not excessively cleaned,
alumina of the inner wall of the vacuum vessel is not damaged and a
stable processing is possible over a long period of time. Thus,
deposition of the reaction product on the inner wall of the vacuum
vessel during the etching can be inhibited.
[0031] Next, various plasma processing methods will be explained
referring to FIG. 5.
[0032] The processing method shown in A is a method of carrying out
the processing under application of Faraday shield voltage for
inhibition of deposition of the reaction product on the inner wall
of the vacuum vessel in etching of a sample. According to this
method, deposition of the reaction product on the inner wall of the
vacuum vessel can be diminished, and, hence, stable discharging can
be attained. Furthermore, since the number of washing or cleaning
can be reduced, working efficiency of the apparatus is high.
[0033] The processing method shown in B is a method of carrying out
the cleaning every after n pieces of samples are etched. This
processing method is employed in case the reaction product cannot
be completely removed even if etching is carried out under
application of a voltage to the Faraday shield or is employed for
such processing as taking preference of the etching speed without
application of voltage to the Faraday shield. According to this
method, a gas different from the etching gas for the sample can be
used for cleaning. Therefore, when a gas high in cleaning effect is
selected, the reaction product can be completely removed. Moreover,
cleaning time can be shortened.
[0034] The processing method shown in C is a method in which an
aging treatment is carried out before the processing method of A.
This method is used for obtaining a stable state of the apparatus
immediately after washing which involves atmospheric exposure. In
the apparatus after subjected to washing, various materials adhere
to the inner wall of the vacuum vessel and foreign matters are apt
to be produced. Therefore, a dummy wafer is fed to the electrode 5,
and plasma discharge mainly composed of chlorine gas is generated
under application of a voltage of at least 500 V to the Faraday
shield, thereby carrying out the treatment to diminish the foreign
matters in the vacuum vessel. Thereafter, etching is carried out,
whereby influence by the foreign matters can be reduced.
[0035] The processing method shown in D comprises combination of
the aging treatment explained as to C and the cleaning explained as
to B. This is a method suitable when production of foreign matters,
change of discharge state and change with time of process are
particular problems. By using this processing method in the
conventional process in which washing which involves atmospheric
exposure must be frequently carried out, also, diminishment of
foreign matters can be attained, besides a stable etching
performance can be obtained, and working efficiency of the
apparatus can be improved.
[0036] Examples where various nonvolatile materials are etched by
the processing method of the present invention will be explained
below.
[0037] FIG. 6 shows the etching speed when 1 lot (8 pieces) of Au
were continuously processed by applying a voltage of about 600 V to
the Faraday shield. It can be seen that if the processing was
carried out without applying the Faraday shield voltage, plasma
disappeared by the influence of reaction product at the processing
of the eighth wafer, and continuation of the etching was impossible
while if the processing with application of voltage to the Faraday
shield was carried out, a stable processing of 2.6% in uniformity
of the etching speed in the lot could be performed. The uniformity
in the lot means variation of etching speed of wafers in one lot
(for example, a unit of 8 wafers, 12 wafers, 25 wafers), and the
lower value means that the stabler etching was performed. As in the
etching of Au, a stable etching speed was also obtained in the
etching of NiFe, and the uniformity in the lot was 1.3%.
Furthermore, in the etching of FeN, the uniformity in the lot was
about 3%, and stable etching could be performed.
[0038] FIG. 7 shows etching speed when 1 lot (8 pieces) of Ta were
continuously processed without applying a voltage to the Faraday
shield. In the processing of Ta, since etching speed is in
preference to the change with time, the processing is carried out
without applying the Faraday shield voltage. Thereafter, in order
to remove the reaction product adhering to the inner wall of the
vacuum vessel, cleaning was carried out after processing of 1 lot.
The uniformity in the lot was about 4.8%, and the uniformity
between the lots by carrying out the cleaning was about 1.7%. The
uniformity between the lots means variation of etching speed of,
for example, the first wafer in each lot, and the lower value means
that the stabler etching was performed.
[0039] FIG. 8 shows etching speed when Pt was processed by applying
a voltage of about 700 V to the Faraday shield. A cleaning which
comprised applying a voltage of 1500 V to the Faraday shield was
carried out for about 10 minutes after processing of 1 lot (25
pieces), and as a result, stable processing of about 1.3% in both
the uniformity in the lot and the uniformity between the lots could
be performed. Moreover, as for Ir, when processing was carried out
by applying a voltage of about 600 V to the Faraday shield, and the
above cleaning was carried out after processing of 1 lot (25
pieces), a uniformity in the lot of about 2.9% and a uniformity
between the lots of about 3% could be obtained.
[0040] Next, a method of determination of end point for detecting
an end point of a cleaning time for cleaning in a proper time the
reaction product adhering to the inner wall of the vacuum vessel
using the Faraday shield will be explained referring to FIG. 9 and
FIG. 10. The abscissa axis shows cleaning time and the ordinate
axis shows emission intensity.
[0041] FIG. 9 shows a method of determination of end point in the
case of observing wavelength of the reaction product. By applying a
voltage to the Faraday shield, the reaction product adhering to the
inner wall of the vacuum vessel begins to be removed. Thereby,
since the reaction product is ionized and floats in the vacuum
vessel, the emission intensity of the reaction product becomes
strong. When the reaction product in the vacuum vessel gradually
begins to be removed, the emission intensity also lowers and the
secondary finite difference of the emission also decreases. The
secondary finite difference of the emission gradually begins to
rise and when the secondary finite difference of the emission
crosses 0, this point is the end point.
[0042] FIG. 10 shows a method of determination of end point in the
case of observing wavelength of the product formed from the vacuum
vessel per se. For example, when the vacuum vessel is made of
alumina, the emission wavelength is 308 nm (Al), 396 nm (Al), or
the like, and when it is made of quartz, the emission wavelength is
391 nm (SiCl), 437 nm (SiF), or the like. By applying a voltage to
the Faraday shield, the reaction product adhering to the inner wall
of the vacuum vessel begins to be removed, but emission intensity
is low because the reaction product covers the inner wall of the
vacuum vessel. Since the reaction product adhering to the inner
wall of the vacuum vessel gradually reduces, the surface layer part
of the vacuum vessel appears. Thus, the emission intensity
increases, and the secondary finite difference of the emission also
rises. The secondary finite difference of the emission gradually
begins to descend, and when the secondary finite difference of the
emission crosses 0, this point is the end point.
[0043] When such method is used, the reaction product does not
remain on the inner wall of the vacuum vessel and, besides, the
inner wall of the vacuum vessel is not damaged by excessive
cleaning, and therefore the processing can be stably carried out
over a long period of time and the life of the vacuum vessel can be
prolonged.
[0044] Next, optimization of interval between cleanings of the
inner wall of the vacuum vessel using a monitor for foreign matters
will be explained. Conventionally, in order to inhibit production
of defective products caused by unstable etching, the cleanings
have been forcedly carried out at previously set intervals, for
example, at every one lot. In this example, measurement of foreign
matters is carried out at real time during processing of samples,
and optimization of cleaning interval is effected on the basis of
the previously determined upper limit (for example, the number of
foreign matters having the possibility of hindering the etching)
and lower limit (for example, the number of foreign matters before
the processing of samples). FIG. 11 shows a relation between the
processing time and the number of foreign matters. With repeating
the processing of the samples, the number of foreign matters in the
plasma increases. When the number of foreign matters exceeds the
given upper limit during processing of the nth sample, the next
(n+1)th sample is not processed after the processing of the nth
sample, and at this time a cleaning is carried out by applying a
voltage to the Faraday shield. This cleaning is preferably set so
as to be able to perform automatically. In this cleaning,
monitoring of the number of foreign matters is also carried out,
and if the number of foreign matters reduces below the given lower
limit, the cleaning is stopped and processing of the (n+1)th sample
is started. By repeating this procedure, optimization of cleaning
interval can be attained, and working efficiency of the apparatus
is improved.
[0045] Next, a cleaning with a mixed gas comprising boron
trichloride and chlorine will be explained. FIG. 12(a) shows inside
of the discharge part 2a of a vacuum vessel made of alumina before
carrying out the etching of Ru. Furthermore, (b) shows the state
after etching. The portion which is seen black is the portion on
which the reaction product is deposited. For removing this reaction
product, cleaning was carried out for about 30 minutes using a
mixed gas of chlorine and oxygen as a cleaning gas, and the result
is shown in (c). The reaction product could not be completely
removed. Next, etching was carried out under the same conditions,
and then cleaning was carried out for about 30 minutes using a
mixed gas of boron trichloride and chlorine. The result is shown in
(d). The reaction product could be removed nearly completely.
[0046] FIG. 13(a) shows the inside of the discharge part 2a of a
vacuum vessel made of alumina before carrying out the etching of
Au. Furthermore, in (b), the etching was carried out without
applying a voltage to the Faraday shield, and it can be seen that
the reaction product was deposited on the whole surface. In order
to remove this reaction product, cleaning was carried out for about
10 minutes using a mixed gas of boron trichloride and chlorine, and
the reaction product could be removed nearly completely as shown in
(c).
[0047] As mentioned above, a mixed gas of boron trichloride and
chlorine is high in efficiency as a cleaning gas, and a mixed gas
comprising 20% of boron trichloride and 80% of chlorine is most
effective for cleaning. It is further found that a mixed gas of
boron trichloride and chlorine has cleaning effect for reaction
products produced by etching of various nonvolatile materials.
[0048] As explained above, the present invention provides a plasma
processing method and an apparatus, according to which deposition
of reaction products on the inner wall of vacuum vessel during
processing of samples can be inhibited for any nonvolatile samples
by applying an optimum Faraday shield voltage, and, besides,
reaction products deposited on the inner wall of vacuum vessel can
be efficiently removed.
[0049] It should be further understood by those skilled in the art
that the foregoing description has been made on embodiments of the
invention and that various changes and modifications may be made in
the invention without departing from the spirit of the invention
and the scope of the appended claims.
* * * * *