U.S. patent application number 12/403667 was filed with the patent office on 2009-07-09 for substrate processing apparatus.
This patent application is currently assigned to HITACHI KOKUSAI ELECTRIC INC.. Invention is credited to Kazuyuki Okuda, Masanori SAKAI, Nobuhito Shima.
Application Number | 20090176017 12/403667 |
Document ID | / |
Family ID | 32310513 |
Filed Date | 2009-07-09 |
United States Patent
Application |
20090176017 |
Kind Code |
A1 |
SAKAI; Masanori ; et
al. |
July 9, 2009 |
SUBSTRATE PROCESSING APPARATUS
Abstract
A substrate processing device comprises a reaction vessel 11
forming a space receiving a substrate 1 and adapted to have a
plurality of reaction gases supplied thereto to perform desired
processing of the substrate, an exhaust port 16 formed in the
reaction vessel 11 for exhausting the reaction vessel 11, and a gas
supply system 70A, 70B for supplying at least a plurality of
reaction gases into the reaction vessel 11, the gas supply system
70A, 70B including a cleaning gas supply unit for supplying a
cleaning gas to perform desired processing of the substrate 1 to
thereby remove adherents in the reaction vessel 11, and a
post-processing gas supply unit for supplying a post-processing gas
capable of removing the elements contained in the cleaning gas
remaining in the reaction vessel 11 after the adherents have been
removed by supplying the cleaning gas, the post-processing gas
containing all of the reaction gases used in performing desired
processing of the substrate.
Inventors: |
SAKAI; Masanori; (Tokyo,
JP) ; Shima; Nobuhito; (Tokyo, JP) ; Okuda;
Kazuyuki; (Tokyo, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
HITACHI KOKUSAI ELECTRIC
INC.
Tokyo
JP
|
Family ID: |
32310513 |
Appl. No.: |
12/403667 |
Filed: |
March 13, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10529896 |
Dec 27, 2005 |
|
|
|
PCT/JP2003/014162 |
Nov 6, 2003 |
|
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|
12403667 |
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Current U.S.
Class: |
427/255.28 |
Current CPC
Class: |
C23C 16/45536 20130101;
C23C 16/4405 20130101 |
Class at
Publication: |
427/255.28 |
International
Class: |
C23C 16/44 20060101
C23C016/44 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 11, 2002 |
JP |
2002-327193 |
Claims
1. A substrate processing method, comprising: with a substrate
processing apparatus including: a reaction container for
accommodating a substrate, the reaction container forming a space
where the substrate is subjected to desired processing using a
first reaction gas and a second reaction gas; an exhaust port in
the reaction container for exhausting gas from the reaction
container; a gas supply system for supplying the first reaction gas
and the second reaction gas and a cleaning gas to the reaction
container; and a controller for controlling the gas supply system,
subjecting the substrate to desired processing using the first
reaction gas and the second reaction gas; removing the processed
substrate from the reaction container; supplying the cleaning gas
to the reaction container; exhausting the cleaning gas from the
reaction container; and before processing an additional substrate,
supplying the first reaction gas to the reaction container,
exhausting the first reaction gas from the reaction container, and
supplying the second reaction gas to the reaction container.
2. The method of claim 1, wherein before processing the additional
substrate, the first reaction gas and the second reaction gas are
alternately supplied to the reaction container.
3. The method of claim 1, wherein the gas supply system comprises a
first supply nozzle for supplying the first reaction gas and a
second supply nozzle for supplying the second reaction gas
independently of the first reaction gas.
4. The method of claim 1, wherein one of the first reaction gas and
the second reaction gas is a reaction gas including silicon.
5. The method of claim 1, wherein one of the first reaction gas and
the second reaction gas is ammonia gas activated by plasma.
6. The method of claim 4, wherein the other of the first reaction
gas and the second reaction gas is ammonia gas activated by
plasma.
7. The method of claim 1, wherein the cleaning gas is a gas
including fluorine.
8. The method of claim 5, wherein the cleaning gas is a gas
including fluorine.
Description
[0001] This application is a Divisional of co-pending application
Ser. No. 10/529,896, filed on Dec. 27, 2005, the entire contents of
which are hereby incorporated by reference and for which priority
is claimed under 35 U.S.C. .sctn. 120.
TECHNICAL FIELD
[0002] The present invention relates to a substrate processing
apparatus, and more particularly, to a substrate processing
apparatus for effecting cleaning after a substrate is subjected to
desired processing.
BACKGROUND ART
[0003] A thermal CVD (Chemical Vapor Deposition) apparatus
comprises a furnace. According to the thermal CVD apparatus, a
plurality of raw material gases are mixed and allowed to flow into
in the furnace, and a film is formed on a substrate. If the film is
formed on the substrate, the film adheres not only to the substrate
but also to an inner side of the furnace. If the film adhering to
the inner side of the furnace is accumulated and becomes thicker,
the film is peeled off, and this generates foreign material.
[0004] To avoid this, etching gas is allowed to flow at regular
intervals, and cleaning is carried out to remove the film on the
inner side of the furnace. When the film is SiN for example, DCS
(SiH.sub.2Cl.sub.2: dichlorsilane) gas and non-plasma NH.sub.3 gas
are used as the raw material gas, and gas including F (fluorine)
such as NF.sub.3 and ClF.sub.3 is used as the etching gas.
[0005] The film on the inner side of the furnace is removed by the
cleaning, molecules including F (F component, hereinafter) adsorbs
and bonds to the inner wall surface of the furnace and remains
thereon immediately after the cleaning. The molecules are separated
at the time of subsequent film forming operation onto the substrate
and hinder the film formation, and the film forming speed is
decreased. This is because that F has etching function, F reacts
with Si of an SiN film formed on the substrate to form SiF.sub.4
(gas), and Si is removed from the substrate. Another reason is that
F reacts with reaction gas (DCS), and an amount of raw material gas
is reduced.
[0006] For this reason, in the conventional thermal CVD apparatus,
after the cleaning and before the film is formed on the substrate,
the film is forcibly deposited on the inner side of the furnace.
This is called film-preformation. With this film-preformation, F
component is allowed to react with the raw material of the film or
is encapsulated under the film (this is also called trap of F
component) so that F component is reduced from an atmosphere in the
furnace as much as possible and the film forming speed is recovered
when a film is formed.
[0007] In recent years, SiN films can be formed also by an ALD
(Atomic Layer Deposition) apparatus. In the ALD apparatus, DCS gas
and NH.sub.3 activated by plasma (also called NH.sub.3 plasma or
NH.sub.3 radical) are used as the reaction gases, and these two
reaction gases are alternately supplied and films are formed one
atom layer by one atom layer. If the ALD apparatus is used, even at
low temperature, it is possible to form a high quality film as high
as that formed by the thermal CVD apparatus which requires high
temperature process. However, even with the ALD apparatus, a film
must be preformed after cleaning to remove the remaining F like the
thermal CVD apparatus.
[0008] In the above-described conventional technique, elements
including the cleaning gas are trapped by the film-preformation,
and the elements are eliminated from an atmosphere in a reaction
container as much as possible. For this purpose, it is necessary to
carry out the film-preformation. Further, even if a thick
film-preformation is carried out, the elements included in the
cleaning gas can not effectively be eliminated from the atmosphere
in the reaction container. Further, since it is necessary to add a
thermal CVD film-forming nozzle in addition to a special-purpose
buffer nozzle, the structure of the reaction container becomes
complicated and costs thereof are increased. If the thermal CVD
film-forming nozzle is added, there is a problem that foreign
materials are generated due to film formation in the CVD
film-forming nozzle, and this is not preferable.
[0009] Therefore, it is a main object of the present invention to
provide a substrate processing apparatus capable of effectively
eliminating elements included in cleaning gas.
[0010] It is another object of the invention to provide a substrate
processing apparatus capable of effectively preventing foreign
materials from generating from a gas supply system, and to
eliminate the need of the gas supply system itself.
DISCLOSURE OF THE INVENTION
[0011] According to a first aspect of the present invention, there
is provided a substrate processing apparatus, comprising:
[0012] a reaction container which accommodates a substrate, to
which a plurality of reaction gases are supplied, and which forms a
space where said substrate is subjected to desired processing,
[0013] an exhaust port which is opened in said reaction container
for exhausting gas from said reaction container, and
[0014] a gas supply system for supplying at least the plurality of
reaction gases to said reaction container, wherein
[0015] said gas supply system comprises
[0016] a cleaning gas supply unit for supplying cleaning gas which
removes accretion adhering to an inner side of said reaction
container by subjecting said substrate to the desired
processing,
[0017] a post-processing gas supply unit for supplying
post-processing gas which can remove an element included in the
cleaning gas remaining in said reaction container after the
accretion is removed by supplying the cleaning gas, and
[0018] said post-processing gas includes all reaction gases used
when said substrate is subjected to the desired processing.
[0019] According to a second aspect of the present invention, there
is provided a substrate processing apparatus which supplies a
plurality of reaction gases alternately and forms a thin film on a
substrate, comprising:
[0020] a reaction container,
[0021] a plurality of exclusive supply nozzles for respectively and
exclusively supplying the reaction gases, and
[0022] a control apparatus for controlling the substrate processing
apparatus such that cleaning gas is supplied from one of the supply
nozzles into said reaction container at a time of cleaning, all
reaction gases used for processing a substrate are alternately
supplied into said reaction container from the exclusive supply
nozzles after the cleaning gas is supplied and before the substrate
is processed.
BRIEF DESCRIPTION OF THE FIGURES IN THE DRAWINGS
[0023] FIG. 1 is a schematic transverse sectional view of a furnace
constituting a vertical ALD apparatus according to an embodiment of
the present invention.
[0024] FIG. 2 is a schematic vertical sectional view of a furnace
constituting the vertical ALD apparatus according to the embodiment
of the present invention.
[0025] FIG. 3 is a perspective view of a buffer nozzle in a
reaction tube according to the embodiment of the invention.
[0026] FIGS. 4A and 4B show comparison of processing temperatures
of cleaning, film-preformation, film formation when an ALD method
and a thermal CVD method are employed for film-preformation.
[0027] FIG. 5 shows an outline entire structure of the vertical ALD
apparatus according to the embodiment of the invention.
PREFERABLE MODE FOR CARRYING OUT THE INVENTION
[0028] According to a preferable embodiment of the present
invention, there is provided a first substrate processing apparatus
comprising:
[0029] a reaction container which accommodates a substrate, to
which a plurality of reaction gases are supplied, and which forms a
space where said substrate is subjected to desired processing,
[0030] an exhaust port which is opened in said reaction container
for exhausting gas from said reaction container, and
[0031] a gas supply system for supplying at least the plurality of
reaction gases to said reaction container, wherein
[0032] said gas supply system comprises
[0033] a cleaning gas supply unit for supplying cleaning gas which
removes accretion adhering to an inner side of said reaction
container by subjecting said substrate to the desired
processing,
[0034] a post-processing gas supply unit for supplying
post-processing gas which can remove an element included in the
cleaning gas remaining in said reaction container after the
accretion is removed by supplying the cleaning gas, and
[0035] said post-processing gas includes all reaction gases used
when said substrate is subjected to the desired processing.
[0036] Here, the desired processing includes a thin film formation
by vapor phase epitaxy or surface reaction, processing for working
or machining a substrate, such as formation of an oxide film,
dispersion processing and the like.
[0037] Since the post-processing gas which can remove element
included in the cleaning gas from the reaction container is
supplied from the post-processing gas supply unit, the element
included in the cleaning gas can be removed also from the reaction
container as compared with a case in which a film is preformed in
the reaction container and the element is trapped. Since the
post-processing gas supply unit supplies to a substrate, as
post-processing gases, all reaction gases used when said substrate
is subjected to the desired processing, the reaction gases react
with element included in the cleaning gas to produce volatile
material, and the produced volatile material can effectively be
removed from the reaction container. If the post-processing gas
supply unit comprises gas supply means which supplies all reaction
gases used when the substrate is subjected to desired processing,
it is unnecessary to newly add a gas supply system, the structure
does not become complicated. Further, foreign material from a gas
supply system generated when the gas supply system is added can be
prevented from being generated.
[0038] According to another preferred embodiment of the invention,
in the first substrate processing apparatus, there is provided a
second substrate processing apparatus, wherein said post-processing
gas supply unit includes exclusive supply nozzles for independently
supplying each of the reaction gases, and when the reaction gases
are to be supplied as the post-processing gases, the reaction gases
are alternately supplied from the exclusive supply nozzles.
[0039] In the second substrate processing apparatus, the
post-processing gas supply unit can alternately supply reaction
gases as post-processing gases from the exclusive supply nozzles
which respectively supply a plurality of reaction gases used when a
substrate is subjected to desired processing. Thus, gases supplied
from the exclusive supply nozzles effectively affect elements
included in the cleaning gases remaining in the exclusive supply
nozzles and thus, it is possible to effectively remove the elements
included in the cleaning gases remaining in the exclusive supply
nozzles. In this case, examples of combination between a method in
which a substrate is subjected to desired processing and a method
in which the post-processing is carried out are ALD method+ALD
method, and thermal CVD method+ALD method.
[0040] According to still another preferred embodiment of the
invention, in the second substrate processing apparatus, there is
provided a third substrate processing apparatus in which each of
the reaction gases supplied from said post-processing gas supply
unit remove the element remaining in said exclusive supply nozzles
and said reaction container, and form a desired film in said
reaction container.
[0041] In the third substrate processing apparatus, the
post-processing gas supply unit can supply reaction gases for
removing elements remaining in the exclusive supply nozzles and the
reaction container. Thus, it is possible to effectively remove,
from the reaction container, elements remaining in the exclusive
supply nozzles and the reaction container. If the post-processing
gas supply unit can supply reaction gases for forming a desired
film, i.e., for performing a film on the reaction container,
element remaining in the reaction container can be encapsulated in
the preformed film. Therefore, remaining element can be eliminated
from the atmosphere in the reaction container from both removal and
encapsulation and thus, reduction in film forming speed caused by
the remaining element can be avoided. If the reaction gases can
alternately be supplied, the desired films formed in the exclusive
supply nozzles and the reaction container may be thin, and the
throughput is enhanced.
[0042] According to still another preferred embodiment of the
invention, in the third substrate processing apparatus, there is
provided a fourth substrate processing apparatus, wherein the
plurality of reaction gases supplied from the exclusive supply
nozzles are a gas including silicon, and ammonia gas activated by
plasma.
[0043] In the fourth substrate processing apparatus, the gas
including silicon can effectively eliminate element included in the
cleaning gas remaining in the exclusive supply nozzle which
supplies gas including silicon from the atmosphere in the reaction
container. The ammonia gas activated by plasma can effectively
eliminate element included in the cleaning gas remaining in the
exclusive supply nozzle which supplies the ammonia gas from the
atmosphere in the reaction container.
[0044] According to still another preferred embodiment of the
invention, in the fourth substrate processing apparatus, there is
provided a fifth substrate processing apparatus, wherein the
cleaning gas is a gas including fluorine, and the gas including
fluorine is supplied from the exclusive supply nozzle which
supplies a gas including silicon.
[0045] In the fifth substrate processing apparatus, since a film is
easily formed using gas including silicon as compared with ammonia
gas, more accretions adhere to the exclusive supply nozzle which
supplies gas including silicon as compared with the exclusive
supply nozzle which supplies ammonia gas. Therefore, if gas
including fluorine is supplied as cleaning gas from the exclusive
supply nozzle which supplies gas including silicon, the accretions
in the exclusive supply nozzle which supplies gas including silicon
can be removed, and the exclusive supply nozzle can effectively be
cleaned.
[0046] According to still another preferred embodiment of the
invention, in the fourth or fifth substrate processing apparatus,
there is provided a sixth substrate processing apparatus, wherein
the gas including silicon is DCS (SiH.sub.2Cl.sub.2).
[0047] According to still another preferred embodiment of the
invention, in the fifth substrate processing apparatus, there is
provided a seventh substrate processing apparatus, wherein the gas
including fluorine is NF.sub.3 or ClF.sub.3.
[0048] According to still another preferred embodiment of the
invention, there is provided an eighth substrate processing
apparatus which supplies a plurality of reaction gases alternately
and forms a thin film on a substrate, comprising:
[0049] a reaction container,
[0050] a plurality of exclusive supply nozzles for respectively and
exclusively supplying the plurality of the reaction gases, and
[0051] a control apparatus for controlling the substrate processing
apparatus such that cleaning gas is supplied from one of the supply
nozzles into said reaction container at a time of cleaning, all
reaction gases used for processing a substrate are alternately
supplied into said reaction container from the exclusive supply
nozzles after the cleaning gas is supplied and before the substrate
is processed.
[0052] According to still another preferred embodiment of the
invention, there is provided a first semiconductor device producing
method for producing a semiconductor device using a substrate
processing apparatus in which all reaction gases used when a
substrate is processed are supplied to the reaction container after
the process for cleaning the inside of the reaction container and
an element included in the cleaning gas supplied into the reaction
container is removed.
[0053] If a semiconductor device is produced using a substrate
processing apparatus in which all reaction gases used when a
substrate is processed are supplied to the reaction container after
the process for cleaning the inside of the reaction container and
element included in the cleaning gas supplied into the reaction
container is removed, the element remaining in the reaction
container can effectively be removed, reduction in film forming
speed caused by the element is prevented at the time of film
forming process which is carried out the cleaning process, and it
is possible to produce a high quality semiconductor device in which
the film forming amount is stable.
[0054] According to still another preferred embodiment of the
invention, in the first semiconductor device producing method,
there is provided a second semiconductor device producing method
wherein the reaction gases are supplied from the respective
exclusive supply nozzles to the reaction container, and the process
for removing element included in the cleaning gas includes process
for alternately supplies the reaction gases from the exclusive
supply nozzles.
[0055] In the second semiconductor device producing method, the
reaction gases are supplied from the respective exclusive supply
nozzles to the reaction container, and the process for removing
element included in the cleaning gas includes process for
alternately supplies the reaction gases from the exclusive supply
nozzles. Therefore, it is possible to remove the elements remaining
in the reaction container and the exclusive supply nozzles, the
reduction in film forming speed caused by the elements can further
be prevented at the time of film forming process which is carried
out after the cleaning process, and a high quality semiconductor
device having further stable film thickness can be produced.
[0056] According to still another preferred embodiment of the
invention, in the second semiconductor device producing method,
there is provided a third semiconductor device producing method
wherein the process for removing elements included in the cleaning
gas includes the process for removing the element remaining in the
exclusive supply nozzles and the reaction container, and the
process for forming a desired film on a constituent surface in the
reaction container.
[0057] In the third semiconductor device producing method the
process for removing elements included in the cleaning gas includes
the process for removing the element remaining in the exclusive
supply nozzles and the reaction container, and the process for
forming a desired film on a constituent surface in the reaction
container. Thus, it is possible to remove the elements remaining in
the reaction container and the exclusive supply nozzles, and to
encapsulate the elements in the film formed in the reaction
container. The reduction in film forming speed caused by the
elements can further be prevented at the time of the film forming
process which is carried out after the cleaning process, and a high
quality semiconductor device having further stable film thickness
can be produced.
[0058] According to still another preferred embodiment of the
invention, in the first to third semiconductor device producing
methods, there is provided a fourth semiconductor device producing
method wherein the plurality of reaction gases are a gas including
silicon and ammonia gas.
[0059] In the fourth semiconductor device producing method,
preferably, the ammonia gas is ammonia gas activated by plasma. If
the plurality of reaction gases are gas including silicon and
ammonia activated by plasma, the elements remaining in the
exclusive supply nozzles can be removed. The reduction in film
forming speed caused by the elements remaining in the reaction
container and the exclusive supply nozzles can further be prevented
at the time of the film forming process which is carried out after
the cleaning process, and a high quality semiconductor device
having further stable film thickness can be produced.
[0060] According to still another preferred embodiment of the
invention, in the fourth semiconductor device producing method,
there is provided a fifth semiconductor device producing method
wherein the cleaning gas is gas including fluorine, and the
cleaning gas is supplied to the reaction container from the supply
nozzle which supplies gas including silicon.
[0061] In the fifth semiconductor device producing method, the
cleaning gas is gas including fluorine, and the cleaning gas is
supplied to the reaction container from the supply nozzle which
supplies gas including silicon. Therefore, it is possible to
effectively remove the accretions in the exclusive supply nozzle
which supplies gas including silicon which can easily form a film
as compared with ammonia gas, and the inside of the exclusive
supply nozzle can be cleaned effectively, and it is possible to
produce a semiconductor device which suppresses affect of foreign
materials.
[0062] According to still another preferred embodiment of the
invention, in the fourth or fifth semiconductor device producing
method, there is provided a sixth semiconductor device producing
method, wherein the gas including silicon is DCS
(SiH.sub.2Cl.sub.2).
[0063] According to still another preferred embodiment of the
invention, in the fifth semiconductor device producing method,
there is provided a seventh semiconductor device producing method,
wherein the gas including fluorine is NF.sub.3 or ClF.sub.3.
[0064] Next, a preferred embodiment of the present invention will
be explained in more detail with reference to the drawings.
[0065] FIG. 5 shows an outline entire structure of a vertical ALD
apparatus according to the embodiment of the invention. A substrate
processing apparatus 50 is provided at its front surface with a
cassette delivery/receiving unit 49. In the substrate processing
apparatus 50, a cassette shelf 51 is provided such as to be opposed
to the cassette delivery/receiving unit 49, and a spare cassette
shelf 52 is provided above the cassette delivery/receiving unit 49.
A cassette transfer unit 53 is provided with the cassette
delivery/receiving unit 49 and the cassette shelf 51, and a
substrate loader 54 is provided behind the cassette shelf 51. A
boat elevator 55 is provided behind the substrate loader 54, and a
vertical reaction furnace 10 is provided above the boat elevator
55.
[0066] The cassette delivery/receiving unit 49 includes a cassette
stage 58 on which two cassettes 57 can be placed. The cassette 57
is a substrate transfer container. The cassette delivery/receiving
unit 49 also includes two substrate-posture aligners 59 below the
cassette stage 58. If the cassettes 57 transferred by an external
transfer apparatus (not shown) are placed on the cassette stage 58
in a vertical posture (i.e., wafers 1 accommodated in the cassettes
57 are in a vertical posture), the substrate-posture aligners 59
align the postures of the wafers such that notches and orientation
flats of substrates (not shown) such as wafers in the cassette 57
are located at the same positions.
[0067] The cassette stage 58 is rotated through 90.degree. to set
the cassettes 57 horizontally so that the cassette transfer unit 53
can transfer the cassettes 57.
[0068] The cassette transfer unit 53 includes a robot arm 60 which
can move forward and backward in the longitudinal direction, and
the robot arm 60 can move laterally and vertically. The cassettes
57 are transferred from the cassette stage 58 to the cassette shelf
51 or the spare cassette shelf 52 by combination of longitudinal,
vertical and lateral movements of the robot arm 60.
[0069] An arm 61 extends from the boat elevator 55. The arm 61 is
provided with a seal cap 17. A boat which is a substrate holder is
placed on the seal cap 17. The boat 2 holds the multi-stacked
wafers in their horizontal postures. The wafers are brought into
and out from the vertical reaction furnace 10 by the boat elevator
55.
[0070] The substrate loader 54 can rotate and vertically move, and
includes a wafer holder 62 which can move forward and backward. The
wafer holder 62 has a plurality of wafer holding plates 63, and
each wafer holding plate 63 can holds a plurality of wafers
collectively, or can hold one wafer.
[0071] The substrate loader 54 loads a plurality of wafers
collectively or one by one to the boat 2 which is lowered from the
cassette 57 of the cassette shelf 51.
[0072] If the necessary number of wafers are loaded onto the, the
boat 2 is inserted into the vertical reaction furnace 10, and the
wafers are subjected to processing. The ALD method is used for this
wafer processing, and a plurality kinds of raw material gases as
reaction gas are used for the processing. In the processing, the
raw material gases are alternately supplied onto the wafers one
kind by one kind, adsorption and reaction of the gasses are
repeated one atom layer by one atom layer, thereby carrying out the
processing.
[0073] The processed substrates are loaded on the cassettes 57 of
the cassette shelf 51 through a reversed operation of the
above-described operation, the substrates are transferred to the
cassette delivery/receiving unit 49 by the cassette transfer unit
53, and are transferred out by the external transfer apparatus (not
shown).
[0074] FIG. 2 shows a structure of the vertical reaction furnace 10
(simply furnace 10, hereinafter) of the vertical ALD apparatus of
the embodiment. The furnace 10 includes a heater 14 and a
cylindrical quartz reaction tube 11 as a reaction container
provided inside the heater 14. A reaction chamber 12 which is a
substrate processing region is formed in the reaction tube 11. A
furnace opening of the reaction tube 11 is occluded air-tightly by
the seal cap 17. The boat 2 stands on a quartz cap 7 provided on
the seal cap 17. The boat 2 is inserted into the reaction tube 11.
The boat 2 includes a plurality of columns 5 standing between a top
plate 3 and a bottom plate 4. These columns 5 are provided with
grooves 6 formed at distances from one another in the vertical
direction. In the boat 2, the wafers 1 are held horizontally in a
multi-stacked manner in the grooves 6. The boat 2 is vertically
movably supported by the boat elevator 55 (see FIG. 5) and the boat
2 can be brought into and out from the reaction tube 11. The boat 2
is rotated around the rotation shaft 19 in the reaction tube 11 by
a rotation mechanism (not shown). A reference number 18 represents
a sealing O-ring.
[0075] The reaction tube 11 is provided with gas supply means 70.
The plurality of reaction gases are supplied from the gas supply
means 70 into the reaction tube 11. The gas supply means 70
includes a cleaning gas supply system and a post-processing gas
supply system. The reaction tube 11 is provided with an exhaust
port 16 as an exhaust system, and it is possible to exhaust gas
from the reaction tube 11.
[0076] Although only one gas supply means 70 is shown in FIG. 2 as
a matter of convenience, there are provided a plurality of gas
supply means in the actually case so that a plurality kinds of raw
material gases (here, two raw material gases) can be supplied into
the reaction tube 11. One or a portion of the plurality kinds of
raw material gases is gas which is activated by plasma and
supplied, and the remainder is gas which is not activated by plasma
and supplied. For example, a film to be formed on the substrate is
SiN film, the raw material gases includes NH.sub.3 gas which is
required to be activated, and DCS gas which is not required to be
activated. The gas supply means 70 shown here is first gas supply
means (NH.sub.3 gas supply means) 70A which supplies NH.sub.3 gas
activated by plasma. The first gas supply means 70A includes an
NH.sub.3 gas introducing port 20 provided on the one side at a
lower portion of the reaction tube 11, and a quartz NH.sub.3 buffer
nozzle 34 which is connected to the NH.sub.3 gas introducing port
20 and provided in the reaction tube 11. The NH.sub.3 buffer nozzle
34 equalizes the flow rate and the velocity of flow of NH.sub.3 gas
introduced into the reaction tube 11 over the all wafers.
[0077] The NH.sub.3 buffer nozzle 34 extends in an axial direction
of the reaction tube 11 along the tube inner wall 13 from the lower
portion of the reaction tube 11 to a portion in the vicinity of a
top of the reaction tube 11 where a top of the boat 2 is located.
As compared with a normal nozzle whose diameter is uniformly small,
the NH.sub.3 buffer nozzle 34 has a relatively wide nozzle space,
and NH.sub.3 gas is injected into the reaction tube 11 through the
nozzle space. The NH.sub.3 buffer nozzle 34 is provided with a
large number of injection holes (not shown) with the same pitch as
adjacent wafers 1 such as to correspond to the large number of
wafers 1 held in the multi-stacked manner in the vertical
direction.
[0078] The NH.sub.3 buffer nozzle 34 is provided therein with a
pair of plasma electrodes 27 (since the electrodes are superposed
on each other, only one of them is shown in the drawing) for
generating plasma, and the introduced NH.sub.3 gas is activated
with plasma. The pair of plasma electrodes 27 are respectively
inserted into a pair of electrode protection tubes 25 provided in
the NH.sub.3 buffer nozzle 34. Plasma 40 is formed in a plasma
producing region 33 sandwiched between the pair of electrode
protection tubes 25.
[0079] FIG. 1 is a sectional view taken along the line I-I in FIG.
2. There are provided the first gas supply means (NH.sub.3 gas
supply means) 70A and a second gas supply means (DCS gas supply
means) 70B so that two kinds of raw material gases can individually
be introduced into the reaction tube 11. The first gas supply means
70A and the second gas supply means 70B are connected to a control
apparatus 100 and controlled by the control apparatus 100. The
first gas supply means 70A includes an NH.sub.3 gas introducing
tube 22, an NH.sub.3 gas introducing port 20 connected to the
NH.sub.3 gas introducing tube 22, and the NH.sub.3 buffer nozzle 34
which is in communication with the NH.sub.3 gas introducing port
20. The second gas supply means 70B includes a DCS gas introducing
tube 23, a DCS gas introducing port 21 connected to the DCS gas
introducing tube 23, and a DCS buffer nozzle 44 which is in
communication with the DCS gas introducing port 21.
[0080] The first gas supply means 70A supplies NH.sub.3 gas which
is one of the two kinds of raw material gases into the reaction
chamber 12 from the NH.sub.3 buffer nozzle 34 as an exclusive
supply nozzle. The first gas supply means 70A also supplies
NH.sub.3 gas or inert gas such as N.sub.2 which is post-processing
gas into the reaction chamber 12 from the NH.sub.3 buffer nozzle
34. The NH.sub.3 gas is activated by plasma and supplied at the
time of film forming operation and at the time of
post-processing.
[0081] The NH.sub.3 buffer nozzle 34 includes a gas introducing
nozzle portion 28 connected to the NH.sub.3 gas introducing port
20, and a plasma producing nozzle portion 29 for activating gas.
The gas introducing nozzle portion 28 and the plasma producing
nozzle portion 29 are provided side by side with a division wall 26
interposed therebetween, and are brought into communication with
each other through a communication port 30 provided in the division
wall 26. The plasma producing nozzle portion 29 is provided with
the pair of plasma electrodes 27 for generating plasma so that the
introduced gas can be activated by the plasma 40. The activated
NH.sub.3 gas 42 is injected from an injection hole 45 formed in the
plasma producing nozzle portion 29. The pair of plasma electrodes
27 are respectively inserted into the pair of electrode protection
tubes 25 provided in the plasma producing nozzle portion 29. The
pair of plasma electrodes 27 are introduced out from the furnace 10
through the electrode protection tubes 25 and are connected to a
high frequency power supply 31 through a variable capacity aligner
32.
[0082] The NH.sub.3 gas introducing port 20 is connected to a
bifurcated gas introducing tube 22. The gas introducing tube 22
selectively supplies NH.sub.3 gas or inert gas N.sub.2 to the
NH.sub.3 buffer nozzle 34 through the first valve 35 and the second
valve 36. The gas introduced from the NH.sub.3 gas introducing port
20 flows into the gas introducing nozzle portion 28 of the NH.sub.3
buffer nozzle 34, and is supplied to the plasma producing nozzle
portion 29 through the communication port 30. Here, high frequency
electricity is applied between the plasma electrodes 27, plasma 40
is generated in a plasma producing region 46, and NH.sub.3 gas is
activated by the plasma 40. The activated NH.sub.3 gas is injected
from the injection hole 45 of the plasma producing nozzle portion
29 onto the wafers 1 in the reaction chamber 12.
[0083] Since the NH.sub.3 buffer nozzle 34 has the relatively wide
nozzle space therein, radicals generated when the gas is activated
very little collide against the wall of the nozzle, pressure in the
vicinity of the plasma producing region 46 becomes low, this
ensures lifetime of the generated radicals, and NH.sub.3 radicals
can be sent to the reaction chamber (substrate processing region)
12 as they are.
[0084] The second gas supply means 70B supplies DCS gas which is
one of the two kinds of raw material gases to the reaction chamber
12 from the DCS buffer nozzle 44 as an exclusive supply nozzle. The
second gas supply means 70B also supplies NF.sub.3 gas which is
cleaning gas, DCS gas which is post-processing gas, or inert gas to
the reaction chamber 12 from the DCS buffer nozzle 44. The DCS gas
and NF.sub.3 gas are supplied without being activated unlike the
NH.sub.3.
[0085] Unlike the NH.sub.3 buffer nozzle 34, the DCS buffer nozzle
44 does not have a plasma producing nozzle portion, and has only a
portion corresponding to the gas introducing nozzle portion 28. Gas
is injected from an injection hole 47 of the DCS buffer nozzle 44
onto the wafers 1 in the reaction chamber 12. The g21 is connected
to a trifurcated gas introducing tube 23. The trifurcated gas
introducing tube 23 selectively supplies DCS gas, NF.sub.3 gas or
inert gas to the DCS buffer nozzle 44. The trifurcated gas
introducing tube 23 comprises gas introducing tubes 23A, 23B and
23C. The gas introducing tube 23A supplies DCS gas. Since it is
preferable that the pressure in the reaction tube (this pressure is
also called internal pressure of the furnace) rises to a pressure
higher than that of NH.sub.3 gas within a short time, the DCS gas
introducing tube 23A includes a buffer tank 41 for storing DCS gas.
The buffer tank 41 is sandwiched between a fourth valve 38 and a
sixth valve 43. When DCS gas is to be supplied to the reaction
chamber 12, DCS gas is previously stored in the buffer tank 41, the
DCS gas stored in the buffer tank 41 is supplied from the buffer
tank 41 into the reaction chamber 12 at a stroke in a state in
which exhausting operation from the exhaust port 16 of the reaction
chamber 12 is stopped for example, and the plurality of wafers 1 in
the reaction chamber 12 are exposed to the DCS gas. Since it is
preferable that NF.sub.3 gas and inert gas are supplied without
through the buffer tank 41, the gas introducing tubes 23B and 23C
which supplies these gases are connected to the downstream portions
of the buffer tank 41.
[0086] When the gas introducing tube 23B, the DCS gas introducing
port 21 and the DCS buffer nozzle 44 form films on the wafers 1,
reaction by-products as accretions adhering to the inner side of
the reaction tube 11. A cleaning gas supply system 71 supplies
cleaning gas for removing the reaction by-products. After first gas
supply means (NH.sub.3 gas supply means) 70A and second gas supply
means (DCS gas supply means) 70B supply cleaning gas and remove the
reaction by-products, a post-processing gas supply system 72
removes F components included in cleaning gas remaining in the
reaction tube 11.
[0087] FIG. 3 shows the NH.sub.3 buffer nozzle 34 and the DCS
buffer nozzle 44 in the reaction tube 11, and is a perspective view
of the reaction tube 11 as viewed from the hollow arrow shown at
the upper right in FIG. 1. Hole sizes of the gas injection holes 45
and 47 of the buffer nozzles 34 and 44 are increased from upstream
portions toward downstream portions of the buffer nozzles 34 and
44. This is because that since the pressure in the nozzle spaces of
the buffer nozzles 34 and 44 are decreased from the upstream
portions toward the downstream portions, the hole sizes are
increased toward the downstream portions so that the injection
amount of gases injected from the gas injection holes 45 and 47 is
ensured even on the downstream side, and the flow rate is equalized
from the upstream portions toward the downstream portions. As
described above, the gas injection holes 45 and 47 are provided
with the same pitch as adjacent wafers 1 such as to correspond to
the large number of wafers 1 held in the multi-stacked manner in
the vertical direction.
[0088] Next, the operation of the vertical ALD apparatus of the
embodiment having the above-described structure will be explained.
If the film formation (film forming process A) is repeated in the
reaction tube 11 of the vertical ALD apparatus, reaction
by-products adhere and remain to the inner side of the furnace.
Cleaning (cleaning process B) is carried out to remove the reaction
by-products. After the cleaning, post-processing (post-processing
process C) for eliminating elements included in the cleaning gas
remaining in the furnace is carried out. After the post-processing
process C, the film forming process A and the cleaning process B
are repeated. These processes will be explained individually. Here,
time described in the following explanation is a value from which
overhead is subtracted. Here, the overhead means time required for
bringing the boat 2 into and out from the reaction tube 11, and
time required for evacuation and restoration to normal pressure in
the reaction tube. That is, the overhead means time from which time
during which gas is introduced into the reaction chamber is
subtracted.
[0089] Film Forming Process A
[0090] This process is an actual film forming process for forming a
desired film on a wafer. The boat elevator 55 (FIG. 5) moves the
boat 2 down through the seal cap 17, the boat 2 holds a large
number of wafers 1, and the boat elevator 55 inserts the boat 2
into the reaction tube 11. The furnace opening of the reaction tube
11 is completely closed by the seal cap 17 air-tightly and then,
the reaction tube 11 is evacuated from the exhaust port 16 to
exhaust gas from the reaction tube 11. The interior of the reaction
tube 11 is heated to a predetermined temperature, e.g., 400 to
600.degree. C. and the temperature is stabilized. While raw
material gases are supplied from the two buffer nozzles 34 and 44
into the reaction tube 11, the gases are discharged from the
exhaust port 16, and films are formed on the surfaces of the wafers
1.
[0091] As described above, the ALD apparatus is designed such that
DCS gas and NH.sub.3 plasma are alternately supplied from the
exclusive supply DCS nozzle and NH.sub.3 nozzle. Especially in the
case of a vertical ALD apparatus which processes a large number of
stacked substrates at a time, in order to equally supply gases to
the stacked substrates, buffer nozzles having large nozzle spaces
are used as the DCS nozzle and NH.sub.3 nozzle instead of normal
thin nozzles in some cases. Unlike the DCS buffer nozzle, the
NH.sub.3 buffer nozzle is provided therein with a having a plasma
electrode, and a plasma non-producing region into which NH.sub.3
gas is introduced so that NH.sub.3 gas introduced into the plasma
non-producing region is less prone to be activated by plasma in the
plasma producing region. When DCS gas is supplied from the DCS
buffer nozzle so that SiN is less prone to be formed in each buffer
nozzle, inert gas such as N.sub.2 is allowed to flow from the
NH.sub.3 buffer nozzle, and when NH.sub.3 plasma is supplied from
the NH.sub.3 buffer nozzle, inert gas such as N.sub.2 is allowed to
flow from the DCS buffer nozzle.
[0092] This film forming processing is carried out by ALD film
forming processing using two kinds of reaction gases, i.e., DCS and
NH.sub.3, and comprises the following four steps 1) to 4).
[0093] 1) High frequency electricity is not applied between the
plasma electrodes 27 of the NH.sub.3 buffer nozzle 34. To prevent
DCS gas from entering into the NH.sub.3 buffer nozzle 34, the
second valve 36 is opened to allow a small amount of N.sub.2 gas to
flow. The fourth valve 38 is opened, DCS gas which was previously
stored in the buffer tank 41 is supplied to the DCS buffer nozzle
44, and the DCS gas is injected into the reaction chamber 12 from
the injection hole 47. The flow rate of the injected DCS is 0.5 slm
for example, the exhausting operation of the exhaust port 16 is
stopped, and the internal pressure in the furnace is set to 266 to
931 Pa for example. If the wafers 1 are exposed to DCS gas, DCS raw
materials adsorb to the wafers 1.
[0094] 2) The fourth valve 38 is closes and the supply of DCS gas
is stopped. The sixth valve 43 is opened, and storing operation of
DCS gas into the buffer tank 41 is started. Then, the exhaust port
16 is opened, the fifth valve 39 is opened, and N.sub.2 gas which
is inert gas is introduced from the DCS buffer nozzle (second
buffer nozzle) 44 into the reaction tube 11 to purse the DCS buffer
nozzle 44 and the reaction tube 11, thereby eliminating DCS
atmosphere from the DCS buffer nozzle 44 and the reaction tube 11.
The DCS atmosphere may be eliminated by evacuation instead of
N.sub.2 purge.
[0095] 3) To prevent NH.sub.3 radical 42 from entering into the DCS
buffer nozzle 44, the fifth valve 39 is opened to allow a small
amount of N.sub.2 gas. High frequency electricity is applied
between the plasma electrodes 27, the first valve 35 is opened, and
NH.sub.3 gas is supplied to the NH.sub.3 buffer nozzle (first
buffer nozzle) 34. The NH.sub.3 gas is introduced into the plasma
producing nozzle portion 29 from the gas introducing nozzle portion
28 through the communication port 30, and is activated by plasma 40
generated between the plasma electrodes 27. The activated NH.sub.3
radical 42 is injected into the reaction chamber 12 from the
injection hole 45. The flow rate of the injected NH.sub.3 gas is
3.0 to 4.5 slm for example, and the internal pressure in the
furnace is set to 40 to 60 Pa which is lower than the internal
pressure when DCS gas is introduced by conductance control of the
exhaust port 16. If the wafers 1 are exposed to the activated
NH.sub.3 gas, the DCS raw material and the NH.sub.3 raw material
adsorbed to the wafers 1 are reacted with each other, and an SiN
film is formed on each wafer 1 by one atom layer.
[0096] 4) The first valve 35 is closed, the supply of NH.sub.3 gas
is stopped, and the application of high frequency electricity
between the plasma electrodes 27 is stopped. The exhaust port 16 is
held opened, the second valve 36 is opened, N.sub.2 gas which is
inert gas is introduced into the NH.sub.3 buffer nozzle 34, the
N.sub.2 gas is introduced into the reaction tube 11 from the gas
introducing nozzle portion 28 through the plasma producing nozzle
portion 29, the NH.sub.3 buffer nozzle 34 and the reaction tube 11
are purged to eliminate NH.sub.3 atmosphere from the NH.sub.3
buffer nozzle 34 and the reaction tube 11. The NH.sub.3 atmosphere
may be eliminated by evacuation instead of N.sub.2 purge.
[0097] The procedure is returned to the step 1), the steps 1) to 4)
are repeated by desired times. If the steps 1) to 4) is defined as
one cycle, the film is formed by a constant film thickness in one
cycle. Thus, the film thickness can be varied depending upon the
number of cycles. The film forming time depends on the film
thickness, and if the film forming temperature is 550.degree. C.
and the film thickness is 300 .ANG., the film forming time is about
100 minutes. Although the DCS gas was supplied first and then the
NH.sub.3 plasma was supplied in the above steps, this supply order
may be reversed, and the NH.sub.3 plasma may be supplied first and
then the DCS gas may be supplied.
[0098] After the film forming operation is completed in this
manner, gas in the reaction tube 11 is replaced by the inert gas
N.sub.2, the pressure is restored to the normal pressure, the boat
2 is lowered, and the wafers 1 formed with films are taken out from
the boat 2.
[0099] However, even if inert gas is allowed to flow from the other
buffer nozzle when the raw material gas is allowed to flow from one
of the buffer nozzles as described above, it is inevitable that a
little gas is mixed between the buffer nozzles by dispersion
phenomenon. If DCS gas enters the NH.sub.3 buffer nozzle in which
raw material gas is activated by plasma, the nozzle becomes a
generation source of foreign materials. Reasons when the nozzle
becomes the generation source of foreign materials are as
follows:
[0100] 1) If DCS gas is mixed in the plasma producing region of the
NH.sub.3 buffer nozzle at the time of plasma discharge, DCS and
NH.sub.3 plasma react with each other dramatically, polymers are
formed and a film adheres to an inner side of the NH.sub.3 buffer
nozzle. This generates foreign materials.
[0101] 2) A film adheres to the plasma producing region by the
reaction between the DCS and NH.sub.3 plasma, if the film adheres
thickly, NH.sub.3 radicals abruptly collide against the film, the
film is damaged and the film may be peeled off. This also generates
foreign materials.
[0102] In the case of a vertical ALD apparatus using a plurality of
exclusive supply buffer nozzles for alternately supplying a
plurality of gases, it is necessary that cleaning gas enters the
buffer nozzle also in a later-described cleaning process B to
eliminate a film in the buffer nozzle.
[0103] Cleaning Process B
[0104] In a state in which the boat 2 does not hold wafers 1, the
boat elevator 55 inserts the boat 2 into the reaction tube 11. The
seal cap 17 completely closes the furnace opening of the reaction
tube 11 air-tightly and then, the reaction tube 11 is evacuated
from the exhaust port 16 to exhaust gas from the reaction tube 11.
The internal pressure in the reaction tube is set to about
610.degree. C. for example. The third valve 37 is opened, and
NF.sub.3 gas which functions as cleaning gas is injected into the
reaction chamber 12 from the DCS buffer nozzle 44. The flow rate of
the injected NF.sub.3 gas is 0.25 to 1.5 slm. At that time,
evacuation in the reaction tube 11 is continued, and the evacuation
degree is controlled such that the internal pressure in the
reaction tube 11 becomes equal to a predetermined pressure.
NF.sub.3 molecules are activated by heat in the furnace. With this,
reaction by-products adhering to portions in the furnace which were
in contact with the gas, i.e., an inner wall surface of the DCS
buffer nozzle 44, an inner wall surface of the reaction tube 11, a
low temperature portion of the furnace in the vicinity of the
furnace opening 8 and other portions which were in contact are
etched. The NF.sub.3 gas also enters the NH.sub.3 buffer nozzle 34,
and reaction by-products in the plasma producing nozzle portion 29
are etched. The etched reaction by-products are discharged out from
the exhaust port 16. The cleaning time is varied depending upon the
film thickness, but when the film thickness is 0.75 .mu.m, the
cleaning time is about two hours.
[0105] Here, the inside of the gas introducing nozzle portion 28 of
the NH.sub.3 buffer nozzle 34 is the plasma non-producing region 48
other than the plasma producing region 46, and if NF.sub.3 gas
enters the gas introducing nozzle portion 28 and F component
adsorbs and bonds to and remains on the inner wall surface of the
nozzle, the F component cannot be removed because no NH.sub.3
plasma exists. Therefore, a very small amount of nitrogen N.sub.2
is allowed to flow from the gas introducing nozzle portion 28 at
the time of cleaning so that cleaning gas is not mixed in the gas
introducing nozzle portion 28. A reason why the amount of nitrogen
N.sub.2 is very small is as follows. That is, since it is conceived
that reaction by-products adhere to the inner side of the plasma
producing nozzle portion 29 in some degree by the dispersion of DCS
gas, it is necessary to allow cleaning gas to flow into the plasma
producing nozzle portion 29 to remove the reaction by-products as
described above. Therefore, the amount of nitrogen N.sub.2 is
increased, the cleaning gas does not enter the plasma producing
nozzle portion 29, and the reaction by-products can not be removed.
Therefore, the amount of nitrogen N.sub.2 is very small to avoid
this case.
[0106] In this embodiment, the cleaning gas is allowed to flow not
from the NH.sub.3 buffer nozzle 34 which supplies NH.sub.3 gas but
from the DCS buffer nozzle 44 which supplies DCS gas. This is
because of the following three reasons.
[0107] 1) It is conceived that since a film can also be formed
using DCS gas only, a film of reaction by-product adhering to an
inner side of the DCS buffer nozzle 44 is thicker than a film of
reaction by-product adhering to the inner side of the NH.sub.3
buffer nozzle 34. Therefore, it is necessary to effectively remove
the former reaction by-product.
[0108] 2) If a film is formed after the cleaning, the film forming
speed is decreased. This is because that film forming gas is
affected by remaining F component and film formation is hindered.
When reaction gas is DCS and NH.sub.3 plasma, reaction probability
between the remaining F and NH.sub.3 plasma is higher than that
between the remaining F and DCS gas, and NH.sub.3 plasma is more
susceptible to F. For this reason, when NH.sub.3 gas is allowed to
flow from the NH.sub.3 buffer nozzle 34, the film forming speed is
more decreased as compared with a case in which NF.sub.3 gas is
allowed to flow from the DCS buffer nozzle 44. Thus, it is
preferable that gas which is less susceptible to F is allowed to
flow first.
[0109] 3) If cleaning gas enters the NH.sub.3 buffer nozzle, F
component adsorbs and bonds to the inner wall surface of the
NH.sub.3 buffer nozzle. If NH.sub.3 is not activated by plasma,
NH.sub.3 does not react with fluorine F. Therefore, when NF.sub.3
gas is supplied from the NH.sub.3 buffer nozzle 34, if F component
adsorbs and bonds to and remains in the plasma non-producing region
48 other than the plasma producing region 46, this F component can
not be removed. Thus, it is necessary to keep supplying F into the
reaction chamber 12 for a while after wafer processing is started,
and the film forming speed is not stabilized for a while. It is
necessary to avoid such a case.
[0110] Post-Processing Process C
[0111] The post-processing process is carried out after the
cleaning process. The post-processing process comprises a removing
process for removing element F remaining in the buffer nozzles 34
and 44 and the reaction chamber 12 from the reaction tube 11, and a
film-preformation process for forming desires films on constituent
surfaces in the buffer nozzles 34 and 44 and the reaction tube 11.
These two removing process and the film-preformation process may be
independent different processes, but if the ALD method is used,
both the processes can be carried out as one process. The
film-preformation procedure when the two processes are carried out
as one process using the ALD method is basically the same as the
above-described film forming process A, and is different from the
film forming process A in that the processing time is as short as
about 13 minutes. If the film formation of about 40 cycles is
carried out with this processing time, it is possible to stabilize
the film thickness of the wafer film formation which is carried out
after the post-processing.
[0112] If the post-processing process is carried out using the ALD
method in which NH.sub.3 radical activated by plasma and DCS gas
are alternately supplied, F component on portions in the furnace
which are in contact with gas are removed as in the following
manner.
[0113] 1) NH.sub.3 Buffer Nozzle
[0114] NH.sub.3 gas is supplied to the NH.sub.3 buffer nozzle 34 as
post-processing gas. Then, since the NH.sub.3 is activated by
plasma, F component which adsorbs and bonds to and remained on the
wall surface of the plasma producing nozzle portion 29 of the
NH.sub.3 buffer nozzle 34 reacts with H atom which is ionized from
the NH.sub.3 by the activation, and they become HF which is easily
be discharged from the NH.sub.3 buffer nozzle 34. The HF gas is
discharged from the exhaust port 16 of the reaction tube 11 from
the NH.sub.3 buffer nozzle 34 through the reaction chamber 12.
Further, at the time of film-preformation, an SiN film which is a
preformed film is not intentionally formed in the NH.sub.3 buffer
nozzle 34, but since a certain amount of DCS gas flows into the
NH.sub.3 buffer nozzle 34 by the dispersion effect of gas when the
DCS gas is supplied, it is conceived that a certain amount of
preformed SiN film is formed in the NH.sub.3 buffer nozzle 34.
Therefore, F component which adsorbs and bonds to and remains on
the wall surface of the NH.sub.3 buffer nozzle 34 is discharged
from the atmosphere in the reaction tube by the reaction with
respect to these film raw materials and by encapsulation under the
films. At the time of cleaning, a very small amount of nitrogen
N.sub.2 is allowed to flow into the gas introducing nozzle portion
28 where no NH.sub.3 radical is produced so that F component is
mixed. Therefore, it is unnecessary to suppress the F component by
removing the same by NH.sub.3 radical or by film-preformation.
[0115] 2) DCS Buffer Nozzle
[0116] DCS gas is supplied to the DCS buffer nozzle 44 as
post-processing gas. Then, since this DCS (SiH.sub.2Cl.sub.2) gas
can easily form Si--F bond, F component which adheres to and
remains on the wall surface of the DCS buffer nozzle 44 reacts with
DCS gas and they become SiF (silicon fluoride) gas. This SiF gas is
discharged from the exhaust port 16 of the reaction tube 11 through
the reaction chamber 12 from the DCS buffer nozzle 44. An SiN film
which is a preformed film is not intentionally formed in the DCS
buffer nozzle 44 when the film is to be preformed, but since a
small amount of NH.sub.3 radical flows into the DCS buffer nozzle
44 by the dispersion effect of gas when NH.sub.3 radical is
supplied, it is conceived that a small amount of preform SiN film
is formed in the DCS buffer nozzle 44. Therefore, F component which
adheres to and remains on the wall surface of the DCS buffer nozzle
44 is discharged from the atmosphere in the reaction tube by the
reaction with respect to these film raw materials and by
encapsulation under the films.
[0117] 3) Low Temperature Portion of Furnace
[0118] A reaction probability between F component which adsorbs and
bonds to and remains on a low temperature portion of the furnace
(furnace low temperature portion, hereinafter) in the vicinity
furnace opening 8 and NH.sub.3 radical supplied from the NH.sub.3
buffer nozzle 34 into the reaction chamber 12 is also high.
Therefore, the NH.sub.3 radical especially effectively functions,
the F component becomes HF and if discharged from the reaction tube
11. Since the NH.sub.3 radical and DCS gas are alternately supplied
into the reaction tube 11 from the buffer nozzles 34 and 44, F
component which adsorbs and bonds to and remains on the wall
surface is encapsulated under the film also by the preformed film
formed on the furnace low temperature portion, and the F component
is discharged from the atmosphere in the reaction tube.
[0119] 4) Portions Other than Those Described Above
[0120] Portions in the furnace which are in contact with gas other
than portions in the furnace described above can suppress the F
component which adsorbs and bonds to and remains on the wall
surface by volatilization of F component due to film-preformation
and reaction with respect to DCS gas or NH.sub.3 gas, and can
discharge the F component.
[0121] By the above-described removing effects 1) to 4), F
component on the portions in the furnace which are in contact with
gas can effectively be removed. Thus, even immediately after the
cleaning, F component is separated and does not hinder the film
formation when a film is to be formed on a substrate, and reduction
in film forming speed can effectively be prevented.
[0122] According to the embodiment, as described above, the ALD
method is employed instead of the thermal CVD method when the
film-preformation which is the post-processing process is to be
carried out, and all of raw material gases to be used for actual
film formation are supplied to the post-processing process at that
time. Therefore, it is possible to remove F element from the
furnace by the NH.sub.3 radical and DCS, and to trap F element in
the furnace by the film-preformation and thus, it is possible to
effectively eliminate F element from the atmosphere in the reaction
tube.
[0123] When a film is to be preformed by the thermal CVD method, a
thick film is required for trapping F component. That is, in the
case of the thermal CVD method, the film forming speed is slow in
the low temperature portion in the vicinity of furnace opening 8 as
compared with other portions in the furnace which are in contact
with gas. Therefore, if a film is preformed for trapping the F
component based on the low temperature portion, the film forming
time is increased, and the thickness of a film at other portion of
furnace which is in contact with gas is increased. Further, since
plasma is not used in the thermal CVD method, the thermal CVD
method does not have a function for discharging remaining F
component from the reaction chamber 12 by NH.sub.3 plasma. It is
necessary to encapsulate a large amount of remaining F component
under the preformed film and as a result, a thick preformed film is
required. On the other hand, in the case of a preformed film formed
by the ALD method as in the embodiment, a thin film suffices to
trap F component. That is, in the case of the ALD method, since
NH.sub.3 plasma effectively removes reaction chamber remaining in
the vicinity of the low temperature portion, it is only necessary
to preform a thin film. When the preformed film is thin, time
required until reaction by-product adhering to the inner wall
surface of the reaction tube starts peeling off by the subsequent
substrate processing becomes long, and the number of cleaning
operations can be reduced.
[0124] Therefore, as shown in FIGS. 4A and 4B, when a film is to be
preformed, a thick film is required if the thermal CVD method is
used as in the conventional technique, and it is necessary to
increase the processing temperature to increase the film forming
speed (FIG. 4B). On the other hand, since the embodiment uses the
ALD method, a thin film can be preformed by the removing effect of
remaining F component by NH.sub.3 plasma and DCS gas. Thus, the
film-preformation temperature can be the same as the film formation
temperature of the actual film, and throughput can be enhanced
(FIG. 4A).
[0125] Further, according to the embodiment, the NH.sub.3 buffer
nozzle and the DCS gas buffer nozzle which are exclusive supply
nozzles are utilized as they are as post-processing gas supply
system which supplies post-processing gas, and it is unnecessary to
add a thermal CVD film forming nozzle in addition to the exclusive
supply nozzle. Thus, the structure of the reaction tube does not
become complicated, and costs are not increased. Since the thermal
CVD film forming nozzle is not added, foreign materials are not
generated by the film formation in the CVD film forming nozzle.
[0126] If a substrate processing apparatus which uses the
above-described film forming process, cleaning process and
post-processing process is used, it is possible to produce a
semiconductor device which is less affected by element included in
cleaning gas remaining in a reaction chamber.
[0127] Although the SiN film was formed using DCS and NH.sub.3
activated by plasma as raw material gases, the kinds of gases are
not limited to those. For example, the SiN film can also be formed
using Si.sub.2Cl.sub.6 (hexachloro disilane: HCD) and NH.sub.3 (it
may be or may not be activated by plasma) as raw material
gases.
[0128] Although NF.sub.3 was used as cleaning gas in this
embodiment, etching gas including other F (fluorine) such as
ClF.sub.3 may also be used.
[0129] Although the actual film forming operation and the
post-processing process are carried out by the ALD method in the
embodiment, the invention is not limited to this. For example, the
actual film forming operation may be carried out by the thermal CVD
method, and only the post-processing process may be carried out by
the ALD method. Although the present invention is applied to the
batch type vertical ALD apparatus in the embodiment, the invention
can also be applied to a single wafer type ALD apparatus.
[0130] Although two buffer nozzles having large space capacities as
compared with a normal nozzle are used and gas is activated by
plasma in one of the buffer nozzles in the embodiment, the
invention is not limited to this structure. For example, although
the processing time of the post-processing process is increased,
the present invention can also be applied to a structure in which
gas is activated by plasma outside of the buffer nozzle, or a
normal thin nozzle is used and gas is activated by plasma outside
of the nozzle.
[0131] The entire disclosure of Japanese Patent Application No.
2002-327193 filed on Nov. 11, 2002 including specification, claims,
drawings and abstract is incorporated herein by reference in its
entirety.
INDUSTRIAL APPLICABILITY
[0132] According to the preferred embodiment of the invention as
described above, since reaction gas is used as post-processing gas
carried out after the cleaning, element included in the cleaning
gas can effectively be removed. If all reaction gases used when a
substrate is subjected to desired processing are introduced as
post-processing gases, it is unnecessary to add a gas supply
system, and it is possible to prevent the structure from becoming
complicated. Further, foreign material from a gas supply system
generated when the gas supply system is added can be prevented from
being generated.
[0133] As a result, the present invention can suitably be utilized
especially for a substrate processing apparatus which forms a film
on a semiconductor substrate by the ALD (Atomic Layer Deposition)
also.
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