U.S. patent application number 13/291303 was filed with the patent office on 2012-03-01 for cleaning method.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. Invention is credited to Koji MAEKAWA.
Application Number | 20120048310 13/291303 |
Document ID | / |
Family ID | 37808847 |
Filed Date | 2012-03-01 |
United States Patent
Application |
20120048310 |
Kind Code |
A1 |
MAEKAWA; Koji |
March 1, 2012 |
CLEANING METHOD
Abstract
In a process chamber of a substrate processing apparatus, such
as an RTP apparatus, a carrier is placed and configured to carry
out a contaminant that has been attached to it. In this state, a
cleaning gas containing N.sub.2 and O.sub.2 is introduced into the
process chamber, and cleaning is performed under conditions
including a pressure of 133.3 Pa or less and a temperature of
700.degree. C. to 1,100.degree. C. This cleaning is repeatedly
performed by sequentially replacing a plurality of carriers.
Inventors: |
MAEKAWA; Koji;
(Nirasaki-shi, JP) |
Assignee: |
TOKYO ELECTRON LIMITED
Minato-ku
JP
|
Family ID: |
37808847 |
Appl. No.: |
13/291303 |
Filed: |
November 8, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12705148 |
Feb 12, 2010 |
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13291303 |
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12064721 |
Feb 25, 2008 |
7691208 |
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PCT/JP2006/317103 |
Aug 30, 2006 |
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12705148 |
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Current U.S.
Class: |
134/105 |
Current CPC
Class: |
C23C 16/4405 20130101;
B08B 7/0035 20130101 |
Class at
Publication: |
134/105 |
International
Class: |
B08B 3/00 20060101
B08B003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2005 |
JP |
2005-251819 |
Claims
1. A substrate processing apparatus comprising: a process chamber
including therein a process space having an inner surface defined
by a quartz member and configured to accommodate a target
substrate; a heating device configured to heat the target substrate
in the process chamber; a pressure-reducing device configured to
reduce a pressure inside the process chamber; and a controller
configured to control an operation of the substrate processing
apparatus, wherein the controller includes a computer readable
non-transitory storage medium that stores a control program for
execution on a computer, and the control program, when executed,
causes the controller to control the substrate processing apparatus
to conduct a cleaning sequence for removing a metal existing as a
contaminant in the process space, the cleaning sequence comprising:
introducing a cleaning gas containing N.sub.2 and O.sub.2 at a flow
rate ratio (N.sub.2:O.sub.2) of 1:0.1 to 3 into the process space,
and performing cleaning under conditions including a pressure of
1.3 Pa to 666.6 Pa and a temperature of 900.degree. C. to
1,100.degree. C., while placing a contaminant removal carrier in
the process space, thereby changing the metal to a secondary
substance with a higher vapor pressure and allowing the secondary
substance to be deposited on the contaminant removal carrier, and
then, unloading the contaminant removal carrier with part of the
secondary substance deposited thereon from the process space.
2. The apparatus according to claim 1 wherein the heating device
includes an upper heat generating unit and a lower heat generating
unit configured to heat the process space from above and from
below, respectively.
3. The apparatus according to claim 1, wherein the apparatus
further comprises a support mechanism configured to support the
target substrate, the support mechanism includes substrate support
pins configured to support and hold the target substrate inside the
process space, and a liner setting portion configured to support a
hot liner serving as a measurement target for measuring a
temperature of the target substrate.
4. The apparatus according to claim 3, wherein the apparatus
further comprises a pyrometer configured to measure heat rays from
the hot liner, thereby grasping a temperature of the target
substrate.
5. The apparatus according to claim 3, wherein the support
mechanism is configured to rotate about a vertical axis along with
the target substrate supported thereon.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present divisional application claims the benefit of
priority under 35 U.S.C. 120 to application Ser. No. 12/705,148,
filed on Feb. 12, 2010 which is a divisional application of U.S.
application Ser. No. 12/064,721, filed on Feb. 25, 2008 (now U.S.
Pat. No. 7,691,208), which was the National Stage of
PCT/JP2006/317103, filed Aug. 30, 2006, and claims the benefit of
priority under 35 U.S.C. 119 from Japanese Application No.
2005-251819, filed on Aug. 31, 2005. Application Ser. Nos.
12/705,148 and 12/064,721 are hereby incorporated by reference in
their entirety.
TECHNICAL FIELD
[0002] The present invention relates to a cleaning method and, more
particularly, to a cleaning method for removing a contaminant from
the process chamber of a substrate processing apparatus which
processes a target substrate such as a semiconductor wafer by,
e.g., annealing.
BACKGROUND ART
[0003] RTP (Rapid Thermal Processing) is known as one semiconductor
device manufacturing process. For example, after implanting ions
into a semiconductor wafer (which may be merely referred to as a
"wafer" hereinafter), annealing is performed for rearranging
impurities or recovering crystal damage. When a thermal budget
(amount of heat during process) in the annealing step increases,
dopants (impurities) tend to diffuse in the source/drain regions,
in the case of, e.g., a transistor. This deepens the junction and
decreases the dopant concentration. A shallow junction is
indispensable under a micro-design rule. Hence, RTP is employed
which can decrease the total thermal budget by increasing and
decreasing the temperature rapidly within a short period of
time.
[0004] In such RTP, the wafer temperature must be increased and
decreased rapidly with a good controllability in a clean atmosphere
where no foreign substance or contaminant is present in a
container. For this purpose, after an RTP apparatus is delivered or
repaired, it is indispensable to calibrate the temperature of the
apparatus by increasing and decreasing the temperature while a TC
wafer (Si substrate with a thermocoulpe) having a temperature
measurement function is set in the process chamber thereof. Use of
the TC wafer for temperature calibration may, however, contaminate
the interior of the process chamber with Cu. When the interior of
the process chamber is contaminated with Cu, Cu may be attached to
a target wafer during later annealing and may infiltrate into a
device as a contaminant, greatly impairing the reliability of
semiconductor devices.
[0005] As a prior art for removing metal contamination in a thermal
processing apparatus, it is proposed in a thermal diffusion furnace
to supply a purge gas such as ammonia into a reaction chamber and
activate the gas to react with a metal contaminant contained in a
member inside the reaction chamber, thereby removing the metal
contaminant (for example, Jpn. Pat. Appln. KOKAI Publication No.
2004-311929; claim 2, FIG. 6 and so forth).
[0006] More specifically, the method of Jpn. Pat. Appln. KOKAI
Publication No. 2004-311929 activates ammonia gas at a temperature
of 950.degree. C. and a pressure of 15,960 Pa. Under these
conditions, ammonia gas provides a larger cleaning effect than
N.sub.2 gas. However, the method of Jpn. Pat. Appln. KOKAI
Publication No. 2004-311929 also has the function of nitriding the
surface of a quartz member in the reaction chamber so that
impurities such as a metal are confined in the quartz member,
thereby preventing the impurities such as a metal from diffusing in
the reaction chamber. This method is thus not aimed at reducing the
impurities such as a metal in the reaction chamber to a level that
does not cause a problem. Hence, according to the above method,
every time the interior of the reaction chamber is cleaned with a
fluorine-containing cleaning gas, a purge process must be performed
with ammonia gas.
DISCLOSURE OF INVENTION
[0007] It is an object of the present invention to provide a
cleaning method that can efficiently remove a contaminant such as
Cu which contaminates the interior of a process chamber.
[0008] In view of the above situations, the present inventor
conducted extensive studies and reached findings that in a process
such as a thermal process, Cu contamination of a wafer tends to
increase when the pressure inside a process chamber is low as
compared to a case in which the pressure is high. This may be
caused by the phenomenon that Cu attached to or mixed in the wall
or an instrument in the process chamber diffuses in the process
chamber during a low-pressure thermal process and is attached to
the wafer. Hence, to decrease Cu existing in the process chamber,
it may be better to decrease the pressure even during cleaning.
[0009] It has also been found that, to discharge Cu efficiently, it
is effective to cause metal Cu to change to a substance with a
higher vapor pressure, e.g., a metal oxynitride. This was followed
by achievement of the present invention.
[0010] It has further been found that the cleaning efficiency is
higher where an appropriate carrier is placed in the process
chamber and unloaded after Cu is positively attached to the
carrier, as compared to a case where purging is performed merely
with ammonia gas, as in the method described in Jpn. Pat. Appln.
KOKAI Publication No. 2004-311929.
[0011] According to a first aspect of the present invention, there
is provided a cleaning method for removing a contaminant including
a metal existing in a process chamber of a substrate processing
apparatus, the cleaning method comprising:
[0012] introducing a cleaning gas containing N.sub.2 and O.sub.2
into the process chamber, performing cleaning under conditions
including a pressure of not more than 133.3 Pa and a temperature of
700.degree. C. to 1,100.degree. C., and discharging the contaminant
in the form of a metal oxynitride from the process chamber.
[0013] In the first aspect, N.sub.2 and O.sub.2 in the cleaning gas
are preferably supplied at a flow rate ratio of 1:1. The metal
oxynitride preferably comprises CuNO.sub.x (where x represents a
stoichiometrically possible value). The temperature is preferably
1,000.degree. C. to 1,100.degree. C.
[0014] According to a second aspect of the present invention, there
is provided a cleaning method for removing a contaminant existing
in a process chamber of a substrate processing apparatus, the
cleaning method comprising:
[0015] introducing a cleaning gas into the process chamber, and
performing cleaning under conditions including a pressure of not
more than 666.6 Pa and a temperature of 700.degree. C. to
1,100.degree. C., while placing in the process chamber a carrier
which is configured to carry out the contaminant that has been
attached thereto.
[0016] The temperature is preferably 1.3 Pa to 133.3 Pa. The
cleaning gas preferably comprises a gas containing N.sub.2 and
O.sub.2. In this case N.sub.2 and O.sub.2 are preferably supplied
at a flow rate ratio of 1:1.
[0017] The contaminant preferably comprises a metal or a compound
thereof. The method preferably comprises repeating cleaning while
sequentially replacing a plurality of carriers corresponding to
said carrier. In this case, the carriers preferably comprise a
material containing silicon.
[0018] The substrate processing apparatus preferably comprises an
RTP apparatus. The process chamber may incorporate a quartz
member.
[0019] According to a third aspect of the present invention, there
is provided a cleaning method comprising:
[0020] loading into a process chamber of a substrate processing
apparatus a carrier which is configured to carry out a contaminant
that has been attached thereto;
[0021] increasing internal temperature of the process chamber;
[0022] reducing internal pressure of the process chamber and
exhausting gas therefrom;
[0023] introducing a cleaning gas into the process chamber and
performing a process under conditions including a pressure of not
more than 666.6 Pa and a temperature of 700.degree. C. to
1,100.degree. C.;
[0024] decreasing internal temperature of the process chamber;
[0025] stopping the cleaning gas and increasing internal pressure
of the process chamber; and
[0026] unloading the carrier, to which the contaminant is attached,
from the process chamber. In this case, the temperature is
preferably 1,000.degree. C. to 1,100.degree. C.
[0027] According to a fourth aspect of the present invention, there
is provided a control program for execution on a computer, wherein
the control program, when executed, controls a substrate processing
apparatus to perform a cleaning method for removing a contaminant
existing in a process chamber of the substrate processing
apparatus, by introducing a cleaning gas into the process chamber,
and performing cleaning under conditions including a pressure of
not more than 666.6 Pa and a temperature of 700.degree. C. to
1,100.degree. C., while placing in the process chamber a carrier
which is configured to carry out the contaminant that has been
attached thereto.
[0028] According to a fifth aspect of the present invention, there
is provided a computer readable storage medium that stores a
control program for execution on a computer, wherein the control
program, when executed, controls a substrate processing apparatus
to perform a cleaning method for removing a contaminant existing in
a process chamber of the substrate processing apparatus, by
introducing a cleaning gas into the process chamber, and performing
cleaning under conditions including a pressure of not more than
666.6 Pa and a temperature of 700.degree. C. to 1,100.degree. C.,
while placing in the process chamber a carrier which is configured
to carry out the contaminant that has been attached thereto.
[0029] According to a sixth aspect of the present invention, there
is provided a substrate processing apparatus comprising:
[0030] a process chamber configured to accommodate a target
substrate;
[0031] a heating device for heating the target substrate in the
process chamber;
[0032] a pressure-reducing device for reducing a pressure inside
the process chamber; and
[0033] a controller configured to control the apparatus to perform
a cleaning method for removing a contaminant existing in the
process chamber, by introducing a cleaning gas into the process
chamber, and performing cleaning under conditions including a
pressure of not more than 666.6 Pa and a temperature of 700.degree.
C. to 1,100.degree. C., while placing in the process chamber a
carrier which is configured to carry out the contaminant that has
been attached thereto.
[0034] According to the present invention, since the interior of a
process chamber in a substrate processing apparatus can be cleaned
efficiently, metal contamination of a target substrate is
suppressed. This can improve the yield of semiconductor devices
manufactured by this method and the reliability of the devices.
BRIEF DESCRIPTION OF DRAWINGS
[0035] FIG. 1 is a sectional view schematically showing the
structure of a thermal processing apparatus;
[0036] FIG. 2 is a flowchart for explaining an example of a
cleaning sequence;
[0037] FIG. 3 is a flowchart for explaining cleaning;
[0038] FIG. 4 is a graph showing the measurement result of Cu
contamination amount before and after temperature calibration;
[0039] FIG. 5 is a graph showing the relationship between the
pressure and Cu contamination amount; and
[0040] FIG. 6 is a graph showing the Cu contamination amount before
and after cleaning.
BEST MODE FOR CARRYING OUT THE INVENTION
[0041] A preferred embodiment of the present invention will be
described hereinafter with reference to the accompanying
drawing.
[0042] FIG. 1 is a schematic view schematically showing the
structure of a thermal processing apparatus to which a cleaning
method according to the present invention can be applied. This
thermal processing apparatus 100 is constituted as a single wafer
type RTP apparatus for performing well-controllable rapid annealing
(RTA; Rapid Thermal Annealing). The thermal processing apparatus
100 can be employed in, e.g., high-temperature annealing in the
range of about 800.degree. C. to 1,100.degree. C. which takes place
after a thin film formed on a wafer W is doped with impurities.
[0043] Referring to FIG. 1, reference numeral 1 denotes a
cylindrical chamber. A lower heat generating unit 2 is detachably
arranged on the lower side of the chamber 1. An upper heat
generating unit 4 is detachably arranged on the upper side of the
chamber 1 to oppose the lower heat generating unit 2. The lower
heat generating unit 2 has a water-cooling jacket 3 and a plurality
of tungsten lamps 6 serving as a heating device arranged on the
upper surface of the water-cooling jacket 3. Similarly, the upper
heat generating unit 4 has a water-cooling jacket 5 and a plurality
of tungsten lamps 6 serving as a heating device arranged on the
lower surface of the water-cooling jacket 5. The lamps are not
limited to tungsten lamps but may be, e.g., xenon lamps. The
tungsten lamps 6 provided in the chamber 1 to oppose each other in
this manner are connected to a heater power supply (not shown). The
heat generation amount of the tungsten lamps 6 can be controlled by
adjusting a power supply amount from the heater power supply.
[0044] A support mechanism 7 for supporting the wafer W is arranged
between the lower heat generating unit 2 and upper heat generating
unit 4. The support mechanism 7 includes wafer support pins 7a for
supporting and holding the wafer W in a process space inside the
chamber 1, and a liner setting portion 7b which supports a hot
liner 8 for measuring the temperature of the wafer W during the
process. The support mechanism 7 is connected to a rotary mechanism
(not shown) which rotates the support mechanism 7 about a vertical
axis as a whole. Thus, the wafer W rotates at a predetermined speed
during the process, thereby improving the uniformity of the thermal
process.
[0045] A pyrometer 11 is arranged under the chamber 1. During the
thermal process, the pyrometer 11 measures heat rays from the hot
liner 8 through a port 11a and an optical fiber 11b, so that the
temperature of the wafer W can be grasped indirectly.
Alternatively, the temperature of the wafer W may be measured
directly.
[0046] Under the hot liner 8, a quartz member 9 is arranged between
the hot liner 8 and the tungsten lamps 6 of the lower heat
generating unit 2. As shown in FIG. 1, the port 11a is provided to
the quartz member 9. The port 11a may comprise a plurality of
ports.
[0047] Above the wafer W, a quartz member 10a is arranged between
the wafer W and the tungsten lamps 6 of the upper heat generating
unit 4. A quartz member 10b is disposed on the inner surface of the
chamber 1 to surround the wafer W.
[0048] Lifter pins (not shown) for supporting and vertically moving
the wafer W are arranged to extend through the hot liner 8. The
lifter pins are used when loading/unloading the wafer W.
[0049] Seal members (not shown) are disposed between the lower heat
generating unit 2 and chamber 1 and between the upper heat
generating unit 4 and chamber 1, respectively. The seal members
render the interior of the chamber 1 airtight.
[0050] A gas source 13 connected to a gas introduction pipe 12 is
provided on a side of the chamber 1. A cleaning gas such as N.sub.2
gas or O.sub.2 gas, an inert gas such as argon gas, and so forth
can be introduced into the process space in the chamber 1 through
the gas introduction pipe 12. An exhaust pipe 14 is connected to a
lower portion of the chamber 1. An exhaust unit (not shown) can
reduce the pressure inside the chamber through the exhaust pipe
14.
[0051] The respective components of the thermal processing
apparatus 100 are connected to a process controller 21 comprising a
CPU and controlled by the process controller 21. The process
controller 21 is connected to a user interface 22 comprising a
keyboard through which an operator inputs commands to manage the
thermal processing apparatus 100, a display which visually displays
the operation status of the thermal processing apparatus 100, and
so forth.
[0052] The process controller 21 is also connected to a storage
section 23 which stores recipes such as a control program
(software) for implementing various types of processes to be
executed by the thermal processing apparatus 100 under the control
of the process controller 21, process condition data, and so
forth.
[0053] As needed, a required recipe is called from the storage
section 23 upon instruction or the like from the user interface 22
and executed by the process controller 21, so a desired process is
performed in the thermal processing apparatus 100 under the control
of the process controller 21. For example, the heating rate and
heating temperature of the wafer W can be controlled by the process
controller 21 by controlling power supply amounts to the respective
tungsten lamps 6 provided to the lower heat generating unit 2 and
upper heat generating unit 4. Also, the pressure inside the chamber
1 can be adjusted by the process controller 21 by, e.g.,
controlling driving of the exhaust unit (not shown) and a gas
introduction amount from the gas source 13.
[0054] Recipes with control programs and process condition data
recorded therein may be stored in a computer readable storage
medium, such as a CD-ROM, hard disk, flexible disk, or flash
memory. Further, recipes may be utilized on-line, while it is
transmitted from another apparatus through, e.g., a dedicated line,
as needed.
[0055] In the thermal processing apparatus 100 having the above
arrangement, a wafer W is processed in the following manner. First,
the wafer W is loaded into the chamber 1 through a wafer transfer
port (not shown) and set on the support mechanism 7. Then, an
airtight space is formed in the chamber 1. Under the control of the
process controller 21, a predetermined power is supplied from the
heater power supply (not shown) to the respective tungsten lamps 6
of the lower heat generating unit 2 and upper heat generating unit
4 to turn on the tungsten lamps 6. Then, the respective tungsten
lamps 6 generate heat. The generated heat reaches the wafer W
through the quartz members 9 and 10a so the wafer W is rapidly
heated from above and below under conditions (temperature increase
rate, heating temperature, and so forth) in accordance with a
recipe. The exhaust unit (not shown) is actuated while heating the
wafer W to exhaust gas through the exhaust pipe 14, thereby
reducing the pressure inside the chamber 1.
[0056] During the thermal process, the rotary mechanism (not shown)
rotates the support mechanism 7 in, e.g., the horizontal direction
about a vertical axis as a whole to rotate the wafer W. As a
result, the uniformity of the amount of heat supplied to the wafer
W is ensured.
[0057] During the thermal process, the pyrometer 11 measures the
temperature of the hot liner 8 to control the temperature of the
wafer W indirectly. The temperature data measured by the pyrometer
11 is fed back to the process controller 21. If the measured
temperature is different from the preset temperature of the recipe,
power supply to the tungsten lamps 6 is adjusted.
[0058] When the thermal process is ended, the tungsten lamps 6 of
the lower heat generating unit 2 and upper heat generating unit 4
are turned off, and the pressure inside the chamber 1 is increased.
Further, gas is exhausted from inside the chamber 1 through the
exhaust pipe 14 while supplying a purge gas such as nitrogen into
the chamber 1 through a purge port (not shown), thereby cooling the
wafer W. After that, the wafer W is unloaded from the chamber 1
through the wafer transfer port (not shown).
[0059] Cleaning in the thermal processing apparatus 100 will be
described with reference to FIGS. 2 and 3. Cleaning is done under a
predetermined pressure by using a cleaning wafer CW as a carrier
which carries a contaminant such as Cu outside the chamber 1. The
material and so forth of the cleaning wafer CW can be selected in
accordance with the type of the contaminant. For example, if the
contaminant to be removed is Cu, the cleaning wafer CW may be
formed of a member made of a silicon-containing material such as an
Si substrate, or a substrate containing poly-silicon, silicon
nitride, silicon oxide, or the like as a constituent element. The
cleaning wafer CW may be made of a different material in accordance
with the type of a contaminant.
[0060] First, in step S1, the cleaning wafer CW is loaded into the
chamber 1 and set on the support mechanism 7. After that, an
airtight space is formed in the chamber 1. In step S2, under the
control of the process controller 21, the heater power supply (not
shown) is turned on to supply a predetermined power to the
respective tungsten lamps 6 of the lower heat generating unit 2 and
upper heat generating unit 4, thereby turning on the tungsten lamps
6. Heat rays (with a wavelength of 800 nm to 3,000 nm in the
near-infrared range) thus generated heat the hot liner 8 in the
chamber 1 to heat the wafer W to a predetermined temperature.
[0061] Subsequently, a cleaning gas is introduced from the gas
source 13 into the chamber 1 while heating the cleaning wafer CW
(step S3). Although the type of cleaning gas is not particularly
limited, N.sub.2 and O.sub.2 are preferably used. This is so
because if heating is done with only N.sub.2 gas, the quartz member
in the chamber 1 may be damaged and generate particles.
[0062] N.sub.2 and O.sub.2 react at a high temperature of, e.g.,
900.degree. C. and more particularly 1,000.degree. C. or more and
form NO. If NO reacts with, e.g., Cu as the contaminant, it forms a
metal oxynitride such as CuNO.sub.x (where x represents a
stoichiometrically possible value). The metal oxynitride has a
higher vapor pressure than the metal alone and, in the vacuum, can
be emitted easily into the atmosphere. Thus, Cu as the contaminant
in the chamber 1 can be emitted in the form of a metal oxynitride
into the atmosphere and discharged outside the chamber 1
efficiently together with the exhaust gas. In this case, for
example, the flow rate ratio of N.sub.2 to O.sub.2 can be set to
N.sub.2:O.sub.2=1:0.1 to 3, and is preferably 1:1 for the sake of
forming NO efficiently.
[0063] Subsequently, in step S4, the exhaust unit (not shown) is
actuated to exhaust gas through the exhaust pipe 14. This sets the
interior of the chamber 1 to a predetermined low-pressure state and
stabilizes the flow rate of the cleaning gas.
[0064] In step S5, cleaning is performed for a predetermined period
of time at a preset temperature and a preset pressure. Step S5 is
done under a cleaning pressure of 666.6 Pa or less. If the cleaning
pressure exceeds 666.6 Pa, a sufficient cleaning effect cannot be
obtained. From the viewpoint of improving the cleaning effect, the
cleaning pressure is preferably set to, e.g., 1.3 Pa to 133.3 Pa,
and more preferably 6.7 Pa to 106.7 Pa. The reason for this is as
follows. For example, Cu has a very low vapor pressure of as low as
133.3 Pa/1,628.degree. C., whereas the metal oxynitride, which is
formed when Cu and NO react in the chamber, has a higher vapor
pressure than Cu alone, and thus can be discharged easily into the
vacuum. Hence, cleaning under low-pressure conditions is
effective.
[0065] The cleaning temperature is preferably, e.g., 700.degree. C.
to 1,100.degree. C., more preferably 900.degree. C. to
1,100.degree. C., and most preferably 1,000.degree. C. to
1,100.degree. C.
[0066] During the cleaning, the rotary mechanism (not shown)
rotates the support mechanism 7 about the vertical axis (i.e., in
the horizontal direction) as a whole at a rotational speed of,
e.g., 20 rpm, thereby rotating the cleaning wafer CW. As a result,
the amount of heat supplied to the cleaning wafer CW is
uniformized.
[0067] During the cleaning, the pyrometer 11 measures the
temperature of the cleaning wafer CW indirectly through the hot
liner 8. The temperature data measured by the pyrometer 11 is fed
back to the process controller 21. If the measured temperature is
different from the preset cleaning temperature of the recipe, power
supply to the tungsten lamps 6 is adjusted.
[0068] After the cleaning is ended, the heater power supply (not
shown) is turned off to turn off the tungsten lamps 6 of the lower
heat generating unit 2 and upper heat generating unit 4, thereby
decreasing the temperature (step S6). In step S7, the cleaning gas
is stopped and the pressure inside the chamber 1 is increased. In
step S8, the cleaning wafer CW is unloaded from the chamber 1.
Cleaning using one cleaning wafer CW is ended through the process
of the above steps S1 to S8.
[0069] As shown in FIG. 3, using, e.g., first to nth cleaning
wafers CW, steps S1 to S8 are repeatedly performed, thus ending the
cleaning of the chamber 1. Regarding the cleaning end point, the Cu
contamination amounts on the respective cleaning wafers CW employed
are measured by a device such as an ICP-MS (inductively coupled
plasma ion mass spectrometer). A time point when the Cu
contamination amounts decrease to a predetermined value or less can
be determined as the cleaning end point. Usually, about 25 to 50
cleaning wafers CW are used depending on the degree of
contamination and the required value, and steps S1 to S8 are
repeated to decrease the contaminant such as Cu to a level that
poses no problem, so that the interior of the chamber 1 can be
cleaned. The type of cleaning wafer CW to be used can be changed
for each cleaning cycle consisting of steps S1 to S8, so a
plurality of contaminants can be removed.
[0070] In this manner, according to the present invention, the
interior of the chamber 1 is purged with the cleaning gas, and
simultaneously the plurality of cleaning wafers CW are used as
carriers for contaminants. As a result, the amount of Cu removed
from the chamber 1 is the sum amount of Cu discharged to the
outside of the chamber 1 by exhaust and Cu carried out to the
outside of the chamber using the cleaning wafers CW as the
carriers. Accordingly, as compared to a case in which cleaning is
performed by only exhaust merely using a cleaning gas, the Cu
removing efficiency, i.e., the cleaning efficiency, can be
increased.
[0071] Results of experiments that form the base of the present
invention will be described with reference to FIGS. 4 and 5.
[0072] FIG. 4 shows results obtained where wafers W were thermally
processed and the Cu amount per unit area of the surface of each
wafer W was measured by ICP-MS, before and after temperature
calibration was performed in the thermal processing apparatus 100
by using a TC wafer having a temperature measurement function. As
shown in FIG. 4, the Cu amount on the surface of the wafer W
processed before the temperature calibration was
0.9.times.10.sup.10 [atoms/cm.sup.2], whereas the Cu amount on the
surface of the wafer W processed after the temperature calibration
was 7.0.times.10.sup.10 [atoms/cm.sup.2], showing a great increase
in Cu amount.
[0073] FIG. 5 shows results obtained where wafers W were thermally
processed while changing the pressure and the Cu amount per unit
area of the surface of each wafer W was measured by ICP-MS, after
temperature calibration was performed in the thermal processing
apparatus 100 by using the TC wafer having a temperature
measurement function. Four different pressures, i.e., 6.7 Pa (50
mTorr), 106.7 Pa (800 mTorr), 10,666 Pa (80 Ton), and 79,992 Pa
(600 Ton), were employed in this thermal process. O.sub.2 gas was
introduced into the chamber 1 with a flow rate of 2 L/min (slm),
and the process was performed at 1,100.degree. C. (where the
processing pressure was 6.7 Pa, the O.sub.2 gas was introduced with
a flow rate of 20 mL/min (sccm)).
[0074] As shown in FIG. 5, as the pressure of the thermal process
changed from the high-pressure side (79,992 Pa) to the low-pressure
side (6.7 Pa), the Cu contamination amount increased. In
particular, when the processing pressure was 6.7 Pa, a typical
increase was observed in the Cu contamination amount. This led to a
supposition that in the chamber 1 contaminated with Cu by
temperature calibration, if low-pressure conditions were employed
for cleaning as well, a contaminant such as Cu attached to or mixed
in the inner wall of the chamber 1 or the members in the chamber 1
could be efficiently emitted into the process space.
[0075] A certain amount of emitted Cu was attached to the wafer W.
This led to a possibility that, where cleaning is performed by
placing a contaminant carrier member, e.g., a cleaning wafer CW,
the contaminant is carried out outside the chamber by the carrier,
thereby performing efficient cleaning.
[0076] The result of a test that confirmed the effect of the
present invention will be described.
[0077] In a thermal processing apparatus 100 identical to that in
FIG. 1, temperature calibration was performed using a TC wafer
having a temperature measurement function. After that, cleaning was
performed. Thermal processing was performed before and after the
cleaning. The Cu contamination amount of a wafer W after the
process was measured by the ICP-MS. FIG. 6 shows the result. The
cleaning conditions and thermal processing conditions are as
follows.
[0078] <Cleaning Conditions>
[0079] Process gas: N.sub.2 and O.sub.2 were used with a flow rate
ratio of N.sub.2:O.sub.2=1,000:1,000 mL/min (sccm)
[0080] Processing pressure: 133.3 Pa (1 Torr)
[0081] Processing temperature (maximum temperature): 1,100.degree.
C.
[0082] Process time: 50 sec per cleaning wafer
[0083] Number of times of cleaning operations: 25
[0084] <Thermal Processing Conditions>
[0085] Process gas: N.sub.2 and O.sub.2 were used with a flow rate
ratio of 1:1
[0086] Processing pressure: 133.3 Pa (1 Ton)
[0087] Processing temperature (maximum temperature): 1,100.degree.
C.
[0088] Duration of maximum temperature: 50 sec
[0089] As shown in FIG. 6, the Cu amount on the surface of the
wafer W processed before the cleaning (immediately after
temperature calibration) was 7.0.times.10.sup.10 [atoms/cm.sup.2],
whereas that of the wafer W processed after the cleaning decreased
to 0.9.times.10.sup.10 [atoms/cm.sup.2]. The Cu contamination
amount could thus be decreased to the level equivalent to that
before temperature calibration (see FIG. 4).
[0090] The above result shows that by practicing a cleaning method
according to the present invention, metal contamination of the
wafer W can be suppressed, and the yield of semiconductor devices
to be manufactured utilizing this cleaning method and the
reliability of the devices can be improved.
[0091] Although the embodiment of the present invention has been
described, the present invention is not limited to the above
embodiment and various modifications can be made.
[0092] For example, although the RTP thermal processing apparatus
100 was described as an example in FIG. 1, a cleaning method
according to the present invention can be applied to a substrate
processing apparatus which forms a film on a substrate or a
processing apparatus which forms a CVD film by use plasma.
[0093] The technical idea of the present invention can also be
applied to a case in which the target substrate is a glass
substrate for a flat panel display (FPD) represented by a liquid
crystal display (LED) and a case in which the target substrate is a
compound semiconductor substrate.
INDUSTRIAL APPLICABILITY
[0094] The present invention can be suitably used for cleaning of
the interior of the process chamber of a substrate processing
apparatus which is used in the manufacturing process of various
types of semiconductor devices.
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