U.S. patent application number 10/874371 was filed with the patent office on 2005-12-29 for vertical cvd apparatus and cvd method using the same.
Invention is credited to Matsuura, Hiroyuki.
Application Number | 20050287806 10/874371 |
Document ID | / |
Family ID | 35506460 |
Filed Date | 2005-12-29 |
United States Patent
Application |
20050287806 |
Kind Code |
A1 |
Matsuura, Hiroyuki |
December 29, 2005 |
Vertical CVD apparatus and CVD method using the same
Abstract
A vertical CVD apparatus includes a supply system configured to
supply process gases into a process chamber, and a control section
configured to control an operation of the apparatus. The supply
system includes a plurality of first delivery holes connected to a
first reactive gas line to supply a first reactive gas, and a
plurality of second delivery holes connected to a second reactive
gas line to supply a second reactive gas. Each set of the first
delivery holes and the second delivery holes are arrayed in a
vertical direction at a position adjacent to edges of target
substrates, so as to be distributed entirely over the vertical
length of the target substrates stacked at intervals. The control
section controls the supply system to alternately supply first and
second reactive gases, thereby forming a thin film derived from the
first and second reactive gases on the target substrates.
Inventors: |
Matsuura, Hiroyuki; (Tokyo,
JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Family ID: |
35506460 |
Appl. No.: |
10/874371 |
Filed: |
June 24, 2004 |
Current U.S.
Class: |
438/680 ;
118/715; 257/E21.293 |
Current CPC
Class: |
C23C 16/45531 20130101;
C23C 16/45546 20130101; C23C 16/405 20130101; C23C 16/45525
20130101; H01L 21/31637 20130101; C23C 16/44 20130101; H01L 21/3185
20130101; C23C 16/36 20130101 |
Class at
Publication: |
438/680 ;
118/715 |
International
Class: |
H01L 021/44; C23C
016/00 |
Claims
What is claimed is:
1. A vertical CVD apparatus for performing a CVD process on a
plurality of target substrates all together, the apparatus
comprising: an airtight process chamber configured to accommodate
the target substrates; a holder configured to hold the target
substrates stacked at intervals in the process chamber; a heater
configured to heat an atmosphere in the process chamber; an exhaust
system configured to exhaust the process chamber; a supply system
configured to supply process gases into the process chamber, the
supply system comprising a plurality of first delivery holes
connected to a first reactive gas line to supply a first reactive
gas, and a plurality of second delivery holes connected to a second
reactive gas line to supply a second reactive gas, wherein each set
of the first delivery holes and the second delivery holes are
arrayed in a vertical direction at a position adjacent to edges of
the target substrates, so as to be distributed substantially
entirely over a vertical length of the target substrates stacked at
intervals; and a control section configured to control an operation
of the apparatus, so as to repeatedly execute first and second
steps a plurality of times, thereby forming a thin film derived
from the first and second reactive gases on the target substrates,
wherein the first step is a performed by supplying one gas of the
first and second reactive gases while stopping the other gas, so as
to cause said one gas to be adsorbed on surfaces of the target
substrates, and the second step is performed by supplying said
other gas while stopping said one gas, so as to cause said other
gas to act on said one gas adsorbed on the surfaces of the target
substrates.
2. The apparatus according to claim 1, wherein the supply system
comprises first and second pipes extending in a vertical direction
at a position adjacent to edges of the target substrates, so as to
be present substantially entirely over a vertical length of the
target substrates stacked at intervals, and wherein the first
delivery holes comprise holes formed in the first pipe and the
second delivery holes comprise holes formed in the second pipe.
3. The apparatus according to claim 1, wherein the supply system
comprises a first inactive gas line connected to the first delivery
holes, and a second inactive gas line connected to the second
delivery holes.
4. The apparatus according to claim 3, wherein the control section
is configured to execute a first purge step between the first and
second steps, and execute a second purge step between the second
and first steps, and wherein the first purge step is performed by
exhausting the process chamber while supplying an inactive gas from
the first delivery holes, so as to purge the first reactive gas
from the process chamber, and the second purge step is performed by
exhausting the process chamber while supplying an inactive gas from
the second delivery holes, so as to purge the second reactive gas
from the process chamber.
5. The apparatus according to claim 1, wherein the exhaust system
comprises an inner exhaust passage extending in a vertical
direction at a position adjacent to edges of the target substrates,
so as to be present substantially entirely over a vertical length
of the target substrates stacked at intervals.
6. The apparatus according to claim 5, wherein the process chamber
comprises an inner tube configured to accommodate the holder, and
an outer tube disposed concentrically with the inner tube with a
gap therebetween, the inner exhaust passage is formed along an
inner surface of the inner tube, an outer exhaust passage is formed
between the inner tube and the outer tube and communicates with the
inner exhaust passage at an end of the inner tube, and the outer
exhaust passage is connected to an exhaust apparatus disposed
outside the process chamber.
7. The apparatus according to claim 1, wherein the exhaust system
comprises a plurality of exhaust holes arrayed in a vertical
direction at a position adjacent to edges of the target substrates,
so as to be distributed substantially entirely over a vertical
length of the target substrates stacked at intervals, and the first
and second delivery holes are disposed on a first side of the
process chamber and the exhaust holes are disposed on a second side
of the process chamber opposite the first side.
8. The apparatus according to claim 7, wherein the process chamber
comprises an inner tube configured to accommodate the holder, and
an outer tube disposed concentrically with the inner tube with a
gap therebetween, the exhaust holes comprise holes formed in a wall
of the inner tube, an outer exhaust passage is formed between the
inner tube and the outer tube and communicates with the exhaust
holes, and the outer exhaust passage is connected to an exhaust
apparatus disposed outside the process chamber.
9. The apparatus according to claim 7, wherein the exhaust system
comprises an exhaust pipe extending in a vertical direction at a
position adjacent to edges of the target substrates, so as to be
present substantially entirely over a vertical length of the target
substrates stacked at intervals, and wherein the exhaust holes
comprise holes formed in the exhaust pipe.
10. The apparatus according to claim 1, wherein the first and
second reactive gases comprise a combination selected from the
group consisting of a first combination in which the first reactive
gas is a silane family gas and the second reactive gas is ammonia
gas, and a second combination in which the first reactive gas is an
organic metal gas containing aluminum and the second reactive gas
is an oxidizing gas.
11. A vertical CVD apparatus for performing a CVD process on a
plurality of target substrates all together, the apparatus
comprising: an airtight process chamber configured to accommodate
the target substrates; a holder configured to hold the target
substrates stacked at intervals in the process chamber; a heater
configured to heat an atmosphere in the process chamber; an exhaust
system configured to exhaust the process chamber; a supply system
configured to supply process gases into the process chamber, the
supply system comprising a first delivery hole connected to a first
reactive gas line to supply a first reactive gas, and a plurality
of second delivery holes connected to a second reactive gas line to
supply a second reactive gas, wherein the first delivery hole is
disposed at a substantial bottom of the process chamber, and the
second delivery holes are arrayed in a vertical direction at a
position adjacent to edges of the target substrates, so as to be
distributed substantially entirely over a vertical length of the
target substrates stacked at intervals; and a control section
configured to control an operation of the apparatus, so as to
repeatedly execute first and second steps a plurality of times,
thereby forming a thin film derived from the first and second
reactive gases on the target substrates, wherein the first step is
a performed by supplying one gas of the first and second reactive
gases while stopping the other gas, so as to cause said one gas to
be adsorbed on surfaces of the target substrates, and the second
step is performed by supplying said other gas while stopping said
one gas, so as to cause said other gas to act on said one gas
adsorbed on the surfaces of the target substrates.
12. The apparatus according to claim 11, wherein the supply system
comprises a supply pipe extending in a vertical direction at a
position adjacent to edges of the target substrates, so as to be
present substantially entirely over a vertical length of the target
substrates stacked at intervals, and wherein the second delivery
holes comprise holes formed in the supply pipe.
13. The apparatus according to claim 11, wherein the supply system
comprises a first inactive gas line connected to the first delivery
hole, and a second inactive gas line connected to the second
delivery holes.
14. The apparatus according to claim 13, wherein the control
section is configured to execute a first purge step between the
first and second steps, and execute a second purge step between the
second and first steps, and wherein the first purge step is
performed by exhausting the process chamber while supplying an
inactive gas from the first delivery hole, so as to purge the first
reactive gas from the process chamber, and the second purge step is
performed by exhausting the process chamber while supplying an
inactive gas from the second delivery holes, so as to purge the
second reactive gas from the process chamber.
15. The apparatus according to claim 11, wherein the exhaust system
comprises an inner exhaust passage extending in a vertical
direction at a position adjacent to edges of the target substrates,
so as to be present substantially entirely over a vertical length
of the target substrates stacked at intervals.
16. The apparatus according to claim 15, wherein the process
chamber comprises an inner tube configured to accommodate the
holder, and an outer tube disposed concentrically with the inner
tube with a gap therebetween, the inner exhaust passage is formed
along an inner surface of the inner tube, an outer exhaust passage
is formed between the inner tube and the outer tube and
communicates with the inner exhaust passage at an end of the inner
tube, and the outer exhaust passage is connected to an exhaust
apparatus disposed outside the process chamber.
17. The apparatus according to claim 11, wherein the exhaust system
comprises a plurality of exhaust holes arrayed in a vertical
direction at a position adjacent to edges of the target substrates,
so as to be distributed substantially entirely over a vertical
length of the target substrates stacked at intervals, and the first
and second delivery holes are disposed on a first side of the
process chamber and the exhaust holes are disposed on a second side
of the process chamber opposite the first side.
18. The apparatus according to claim 17, wherein the process
chamber comprises an inner tube configured to accommodate the
holder, and an outer tube disposed concentrically with the inner
tube with a gap therebetween, the exhaust holes comprise holes
formed in a wall of the inner tube, an outer exhaust passage is
formed between the inner tube and the outer tube and communicates
with the exhaust holes, and the outer exhaust passage is connected
to an exhaust apparatus disposed outside the process chamber.
19. The apparatus according to claim 17, wherein the exhaust system
comprises an exhaust pipe extending in a vertical direction at a
position adjacent to edges of the target substrates, so as to be
present substantially entirely over a vertical length of the target
substrates stacked at intervals, and wherein the exhaust holes
comprise holes formed in the exhaust pipe.
20. The apparatus according to claim 11, wherein the first and
second reactive gases comprise a combination selected from the
group consisting of a first combination in which the first reactive
gas is a silane family gas and the second reactive gas is ammonia
gas, a second combination in which the first reactive gas is an
organic metal gas containing aluminum and the second reactive gas
is an oxidizing gas, and a third combination in which the first
reactive gas is an organic metal gas containing tantalum and the
second reactive gas is an oxidizing gas.
21. The apparatus according to claim 11, wherein the first reactive
gas has a vapor pressure of 1.33 kPa or less, or a
bond-dissociation energy of 250 kJ/mol or less.
22. A method for performing a CVD process on a plurality of target
substrates all together in a vertical CVD apparatus, the apparatus
comprising an airtight process chamber configured to accommodate
the target substrates, a holder configured to hold the target
substrates stacked at intervals in the process chamber, a heater
configured to heat an atmosphere in the process chamber, an exhaust
system configured to exhaust the process chamber, and a supply
system configured to supply process gases into the process chamber,
the method comprising: a first step of supplying one gas of first
and second reactive gases while stopping the other gas, so as to
cause said one gas to be adsorbed on surfaces of the target
substrates; and a second step of supplying said other gas while
stopping said one gas, so as to cause said other gas to act on said
one gas adsorbed on the surfaces of the target substrates, wherein
the first and second steps are repeatedly executed a plurality of
times, thereby forming a thin film derived from the first and
second reactive gases on the target substrates, and wherein the
first reactive gas is supplied from a plurality of first delivery
holes arrayed in a vertical direction at a position adjacent to
edges of the target substrates, so as to be distributed
substantially entirely over a vertical length of the target
substrates stacked at intervals, and the second reactive gas is
supplied from a plurality of second delivery holes arrayed in a
vertical direction at a position adjacent to edges of the target
substrates, so as to be distributed substantially entirely over a
vertical length of the target substrates stacked at intervals.
23. The method according to claim 22, wherein the first and second
reactive gases comprise a combination selected from the group
consisting of a first combination in which the first reactive gas
is a silane family gas and the second reactive gas is ammonia gas,
and a second combination in which the first reactive gas is an
organic metal gas containing aluminum and the second reactive gas
is an oxidizing gas.
24. A method for performing a CVD process on a plurality of target
substrates all together in a vertical CVD apparatus, the apparatus
comprising an airtight process chamber configured to accommodate
the target substrates, a holder configured to hold the target
substrates stacked at intervals in the process chamber, a heater
configured to heat an atmosphere in the process chamber, an exhaust
system configured to exhaust the process chamber, and a supply
system configured to supply process gases into the process chamber,
the method comprising: a first step of supplying one gas of first
and second reactive gases while stopping the other gas, so as to
cause said one gas to be adsorbed on surfaces of the target
substrates; and a second step of supplying said other gas while
stopping said one gas, so as to cause said other gas to act on said
one gas adsorbed on the surfaces of the target substrates, wherein
the first and second steps are repeatedly executed a plurality of
times, thereby forming a thin film derived from the first and
second reactive gases on the target substrates, and wherein the
first reactive gas is supplied from a first delivery hole disposed
at a substantial bottom of the process chamber, and the second
reactive gas is supplied from a plurality of second delivery holes
arrayed in a vertical direction at a position adjacent to edges of
the target substrates, so as to be distributed substantially
entirely over a vertical length of the target substrates stacked at
intervals.
25. The method according to claim 24, wherein the first and second
reactive gases comprise a combination selected from the group
consisting of a first combination in which the first reactive gas
is a silane family gas and the second reactive gas is ammonia gas,
a second combination in which the first reactive gas is an organic
metal gas containing aluminum and the second reactive gas is an
oxidizing gas, and a third combination in which the first reactive
gas is an organic metal gas containing tantalum and the second
reactive gas is an oxidizing gas.
26. The method according to claim 24, wherein the first reactive
gas has a vapor pressure of 1.33 kPa or less, or a
bond-dissociation energy of 250 kJ/mol or less.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a vertical CVD (Chemical
Vapor Deposition) apparatus and a CVD method using the same, for a
semiconductor processing system. The term "semiconductor process"
used herein includes various kinds of processes which are performed
to manufacture a semiconductor device or a structure having wiring
layers, electrodes, and the like to be connected to a semiconductor
device, on a target substrate, such as a semiconductor wafer or a
glass substrate used for an LCD (Liquid crystal display) or FPD
(Flat Panel Display), by forming semiconductor layers, insulating
layers, and conductive layers in predetermined patterns on the
target substrate.
[0003] 2. Description of the Related Art
[0004] In order to manufacture semiconductor devices, CVD processes
and pattern etching processes are repeatedly applied to a
semiconductor wafer. As semiconductor devices are becoming more and
more highly miniaturized and integrated, demands on CVD processes
have become stricter. For example, very thin insulating films, such
as capacitor insulating films and gate insulating films are still
required to be thinner and to be more insulating.
[0005] In relation to CVD processes, a so-called ALD (Atomic Layer
Deposition) is known as a technique for improving the quality of a
film to be formed. ALD is performed by alternately supplying at
least two reactive gases pulsewise to repeat two steps, i.e., a
step of causing one of the reactive gases to be adsorbed on a
wafer, and a step of causing the other of the reactive gases to act
on the adsorbed reactive gas. As a consequence, thin layers formed
by respective step-cycles are stacked, thereby forming a film
having a predetermined thickness.
[0006] In the process of manufacturing semiconductor devices, a
semiconductor processing apparatuses is used for performing a
process on a target substrate, such as a semiconductor wafer. A
vertical heat-processing apparatus for simultaneously
heat-processing a number of wafers is known as a processing
apparatus of this kind. In general, a vertical heat-processing
apparatus includes an airtight vertical process chamber (reaction
tube) configured to accommodate wafers. A load port is formed at
the bottom of the process chamber and is selectively opened and
closed by a lid, which is moved up and down by an elevator.
[0007] In the process chamber, the wafers are stacked at intervals
in a holder called a wafer boat, while they are placed in a
horizontal state. The wafer boat with the wafers held thereon is
placed on the lid, and loaded and unloaded into and from the
process chamber through the load port by the elevator.
[0008] U.S. Pat. No. 6,585,823 B1 discloses an example of a
vertical heat-processing apparatus arranged to perform a CVD
process of the ALD type. The apparatus disclosed in this
publication includes a process chamber having a double tube
structure, which is formed of an inner tube and an outer tube. Two
reactive gases are alternately supplied from the bottom of the
inner tube, and pass through gaps between the stacked wafers, and
then flow into an exhaust passage from the top of the inner
tube.
[0009] Jpn. Pat. Appln. KOKAI Publication Nos. 2003-45864 and
2003-297818 disclose other examples of a vertical heat-processing
apparatus arranged to perform a CVD process of the ALD type. The
apparatuses disclosed in these publications include a process
chamber having a single tube structure, in which a buffer chamber
common to two reactive gases is disposed and extends in a vertical
direction. The buffer chamber is provided with delivery holes
formed thereon and arrayed substantially entirely over the vertical
length of stacked wafers. The two reactive gases are alternately
supplied into the buffer chamber, and flows out toward wafers
through the delivery holes.
BRIEF SUMMARY OF THE INVENTION
[0010] As described later, the present inventor has found problems
in the above conventional apparatuses, in that films formed on
wafers are not good in the inter-substrate uniformity (uniformity
among wafers) in terms of characteristics, such as the quality and
thickness of the films, and exchange of reactive gases is
inefficient and thus brings about a low productivity. An object of
the present invention is therefore to provide a vertical CVD
apparatus and a CVD method using the same, for a semiconductor
processing system, which can solve at least one of these
problems.
[0011] According to a first aspect of the present invention, there
is provided a vertical CVD apparatus for performing a CVD process
on a plurality of target substrates all together, the apparatus
comprising;
[0012] an airtight process chamber configured to accommodate the
target substrates;
[0013] a holder configured to hold the target substrates stacked at
intervals in the process chamber;
[0014] a heater configured to heat an atmosphere in the process
chamber;
[0015] an exhaust system configured to exhaust the process
chamber;
[0016] a supply system configured to supply process gases into the
process chamber, the supply system comprising a plurality of first
delivery holes connected to a first reactive gas line to supply a
first reactive gas, and a plurality of second delivery holes
connected to a second reactive gas line to supply a second reactive
gas, wherein each set of the first delivery holes and the second
delivery holes are arrayed in a vertical direction at a position
adjacent to edges of the target substrates, so as to be distributed
substantially entirely over a vertical length of the target
substrates stacked at intervals; and
[0017] a control section configured to control an operation of the
apparatus, so as to repeatedly execute first and second steps a
plurality of times, thereby forming a thin film derived from the
first and second reactive gases on the target substrates, wherein
the first step is a performed by supplying one gas of the first and
second reactive gases while stopping the other gas, so as to cause
the one gas to be adsorbed on surfaces of the target substrates,
and the second step is performed by supplying the other gas while
stopping the one gas, so as to cause the other gas to act on the
one gas adsorbed on the surfaces of the target substrates.
[0018] According to a second aspect of the present invention, there
is provided a vertical CVD apparatus for performing a CVD process
on a plurality of target substrates all together, the apparatus
comprising:
[0019] an airtight process chamber configured to accommodate the
target substrates;
[0020] a holder configured to hold the target substrates stacked at
intervals in the process chamber;
[0021] a heater configured to heat an atmosphere in the process
chamber;
[0022] an exhaust system configured to exhaust the process
chamber;
[0023] a supply system configured to supply process gases into the
process chamber, the supply system comprising a first delivery hole
connected to a first reactive gas line to supply a first reactive
gas, and a plurality of second delivery holes connected to a second
reactive gas line to supply a second reactive gas, wherein the
first delivery hole is disposed at a substantial bottom of the
process chamber, and the second delivery holes are arrayed in a
vertical direction at a position adjacent to edges of the target
substrates, so as to be distributed substantially entirely over a
vertical length of the target substrates stacked at intervals;
and
[0024] a control section configured to control an operation of the
apparatus, so as to repeatedly execute first and second steps a
plurality of times, thereby forming a thin film derived from the
first and second reactive gases on the target substrates, wherein
the first step is a performed by supplying one gas of the first and
second reactive gases while stopping the other gas, so as to cause
the one gas to be adsorbed on surfaces of the target substrates,
and the second step is performed by supplying the other gas while
stopping the one gas, so as to cause the other gas to act on the
one gas adsorbed on the surfaces of the target substrates.
[0025] According to a third aspect of the present invention, there
is provided a method for performing a CVD process on a plurality of
target substrates all together in a vertical CVD apparatus,
[0026] the apparatus comprising
[0027] an airtight process chamber configured to accommodate the
target substrates,
[0028] a holder configured to hold the target substrates stacked at
intervals in the process chamber,
[0029] a heater configured to heat an atmosphere in the process
chamber,
[0030] an exhaust system configured to exhaust the process chamber,
and
[0031] a supply system configured to supply process gases into the
process chamber,
[0032] the method comprising:
[0033] a first step of supplying one gas of first and second
reactive gases while stopping the other gas, so as to cause the one
gas to be adsorbed on surfaces of the target substrates; and
[0034] a second step of supplying the other gas while stopping the
one gas, so as to cause the other gas to act on the one gas
adsorbed on the surfaces of the target substrates,
[0035] wherein the first and second steps are repeatedly executed a
plurality of times, thereby forming a thin film derived from the
first and second reactive gases on the target substrates, and
[0036] wherein the first reactive gas is supplied from a plurality
of first delivery holes arrayed in a vertical direction at a
position adjacent to edges of the target substrates, so as to be
distributed substantially entirely over a vertical length of the
target substrates stacked at intervals, and the second reactive gas
is supplied from a plurality of second delivery holes arrayed in a
vertical direction at a position adjacent to edges of the target
substrates, so as to be distributed substantially entirely over a
vertical length of the target substrates stacked at intervals.
[0037] According to a fourth aspect of the present invention, there
is provided a method for performing a CVD process on a plurality of
target substrates all together in a vertical CVD apparatus,
[0038] the apparatus comprising
[0039] an airtight process chamber configured to accommodate the
target substrates,
[0040] a holder configured to hold the target substrates stacked at
intervals in the process chamber,
[0041] a heater configured to heat an atmosphere in the process
chamber,
[0042] an exhaust system configured to exhaust the process chamber,
and
[0043] a supply system configured to supply process gases into the
process chamber,
[0044] the method comprising:
[0045] a first step of supplying one gas of first and second
reactive gases while stopping the other gas, so as to cause the one
gas to be adsorbed on surfaces of the target substrates; and
[0046] a second step of supplying the other gas while stopping the
one gas, so as to cause the other gas to act on the one gas
adsorbed on the surfaces of the target substrates,
[0047] wherein the first and second steps are repeatedly executed a
plurality of times, thereby forming a thin film derived from the
first and second reactive gases on the target substrates, and
[0048] wherein the first reactive gas is supplied from a first
delivery hole disposed at a substantial bottom of the process
chamber, and the second reactive gas is supplied from a plurality
of second delivery holes arrayed in a vertical direction at a
position adjacent to edges of the target substrates, so as to be
distributed substantially entirely over a vertical length of the
target substrates stacked at intervals.
[0049] Additional objects and advantages of the invention will be
set forth in the description which follows, and in part will be
obvious from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and
combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0050] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate presently
preferred embodiments of the invention, and together with the
general description given above and the detailed description of the
preferred embodiments given below, serve to explain the principles
of the invention.
[0051] FIG. 1 is a sectional view showing a CVD apparatus according
to a first embodiment of the present invention;
[0052] FIG. 2 is a plan view of the apparatus shown in FIG. 1;
[0053] FIG. 3 is an enlarged view showing an upper portion of the
process chamber of the apparatus shown in FIG. 1, and the gas flow
formed therein;
[0054] FIG. 4 is a timing chart showing gas supply patterns
according to the first embodiment of the present invention;
[0055] FIG. 5 is a sectional view showing the process chamber of a
CVD apparatus according to a second embodiment of the present
invention;
[0056] FIG. 6 is an enlarged view showing an upper portion of the
process chamber of the apparatus shown in FIG. 5, and the gas flow
formed therein;
[0057] FIG. 7 is a sectional view showing the process chamber of a
CVD apparatus according to a third embodiment of the present
invention;
[0058] FIG. 8 is a plan view of the apparatus shown in FIG. 7;
[0059] FIG. 9 is a sectional view showing the process chamber of a
CVD apparatus according to a fourth embodiment of the present
invention;
[0060] FIG. 10 is a sectional view showing a CVD apparatus
according to a fifth embodiment of the present invention;
[0061] FIG. 11 is an enlarged view showing an upper portion of the
process chamber of the apparatus shown in FIG. 10, and the gas flow
formed therein;
[0062] FIG. 12 is a timing chart showing gas supply patterns
according to the fifth embodiment of the present invention;
[0063] FIG. 13 is a sectional view showing the process chamber of a
CVD apparatus according to a sixth embodiment of the present
invention;
[0064] FIG. 14 is an enlarged view showing an upper portion of the
process chamber of the apparatus shown in FIG. 13, and the gas flow
formed therein;
[0065] FIG. 15 is a sectional view showing the process chamber of a
CVD apparatus according to a seventh embodiment of the present
invention; and
[0066] FIG. 16 is a plan view of the apparatus shown in FIG.
15.
DESCRIPTION OF THE INVENTION
[0067] In the process of developing the present invention, the
inventor studied the cause of problems in vertical heat-processing
apparatuses arranged to perform a CVD process of the ALD type. As a
result, the inventor has arrived at the findings given below.
[0068] In the case of the apparatus disclosed in U.S. Pat. No.
6,585,823 B1, a wafer closer to the side from which reactive gases
are fed (the bottom side) tends to be given a larger amount of
adsorbed process gas molecules, although this depends on process
conditions (temperature, gas flow rate, pressure, time, etc.).
Accordingly, the quality and thickness of films formed on wafers
vary depending on the position of the wafers in a vertical
direction (i.e., the inter-substrate uniformity is low).
Furthermore, the reactive gases tend to stagnate between the
wafers, and thus exchange of the reactive gases is inefficient. As
a consequence, purging between supply pulses of the reactive gases
takes a longer time, which brings about a low productivity.
[0069] In the case of the apparatuses disclosed in Jpn. Pat. Appln.
KOKAI Publication Nos. 2003-45864 and 2003-297818, reactive gases
tend to remain in the common buffer chamber in which the two
reactive gases are alternately supplied. As a consequence, a
problem arises in that reaction by-products are deposited in the
buffer chamber, or partially block delivery holes, which hinders
the gas supply from taking place as designed. In order to solve
this problem, it is necessary to increase the purge time between
supply pulses of the reactive gases, which brings about a low
productivity.
[0070] Embodiments of the present invention achieved on the basis
of the findings given above will now be described with reference to
the accompanying drawings. In the following description, the
constituent elements having substantially the same function and
arrangement are denoted by the same reference numerals, and a
repetitive description will be made only when necessary.
First Embodiment
[0071] FIG. 1 is a sectional view showing a CVD apparatus according
to a first embodiment of the present invention. FIG. 2 is a plan
view of the apparatus shown in FIG. 1. FIG. 3 is an enlarged view
showing an upper portion of the process chamber of the apparatus
shown in FIG. 1, and the gas flow formed therein. This CVD
apparatus 2 is arranged to alternately supply a first gas
consisting essentially of a silane family gas (silicon source gas),
a second gas consisting essentially of a nitriding gas, and a third
gas consisting essentially of a carbon hydride gas, so as to form a
silicon nitride film. For example, where dichlorosilane (DCS:
SiH.sub.2Cl.sub.2) and NH.sub.3 gases are used to deposit a silicon
nitride film, a carbon hydride gas is supplied to cause carbon
components to be contained in the film.
[0072] As shown in FIG. 1, the CVD apparatus 2 includes a process
chamber 8 having a double tube structure, which is formed of a
cylindrical inner tube 4 made of quartz, and an outer tube 6 made
of quartz and disposed concentrically with the inner tube 4 with a
predetermined gap 10 therebetween. The process chamber 8 is
surrounded by a heating cover 16, which includes a heater or
heating means 12 and a thermal insulator 14. The heating means 12
is disposed over the entire inner surface of thermal insulator 14.
In this embodiment, the inner tube 4 of the process chamber 8 has
an inner diameter of about 240 mm, and a height of about 1300 mm.
The process chamber 8 has a volume of about 110 liters.
[0073] The bottom of the process chamber 8 is supported by a
cylindrical manifold 18 made of, e.g., stainless steel. A ring
support plate 18A extends inward from the inner wall of the
manifold 18 and supports the bottom of the inner tube 4. A number
of target substrates or semiconductor wafers W are stacked on a
wafer boat 20 made of quartz. The wafer boat 20 is loaded and
unloaded into and from the process chamber 8 through the bottom of
the manifold 18. In this embodiment, the wafer boat 20 can support,
e.g., 100 to 150 product wafers having a diameter of 200 mm at
substantially regular intervals in the vertical direction. The size
of wafers W and the number of wafers W to be loaded are not limited
to this example. For example, wafers having a diameter of 300 mm
may be handled.
[0074] The wafer boat 20 is placed on a rotary table 24 through a
heat-insulating cylinder 22 made of quartz. The rotary table 24 is
supported by a rotary shaft 28, which penetrates a lid 26 used for
opening and closing the bottom port of the manifold 18. The portion
of the lid 26 where the rotary shaft 28 penetrates is provided
with, e.g., a magnetic-fluid seal 30, so that the rotary shaft 28
is rotatably supported in an airtightly sealed state. A seal member
32, such as an O-ring is interposed between the periphery of the
lid 26 and the bottom of the manifold 18, so that the interior of
the process chamber 8 can be kept sealed.
[0075] The rotary shaft 28 is attached at the distal end of an arm
36 supported by an elevating mechanism 34, such as a boat elevator.
The elevating mechanism 34 moves up and down the wafer boat 20 and
lid 26 integratedly. An exhaust port 38 is formed in the side of
the manifold 18 to exhaust the atmosphere in the process chamber 8
through the bottom of the gap 10 between the inner tube 4 and outer
tube 6. The exhaust port 38 is connected to a vacuum exhaust
section 39 including a vacuum pump and so forth.
[0076] A gas supply section 40 is connected to the side of the
manifold 18 to supply predetermined process gases into the inner
tube 4. More specifically, the gas supply section 40 includes a
silane family gas supply circuit 42, a nitriding gas supply circuit
44, and a carbon hydride gas supply circuit 46. The gas supply
circuits 42, 44, and 46 respectively include gas nozzles 48, 50,
and 52, which penetrate the sidewall of the manifold 18 side by
side in a horizontal direction. However, for the sake of
convenience, FIG. 1 shows the gas nozzles 48, 50, and 52 in a state
where they penetrate the sidewall of the manifold 18 side by side
in a vertical direction.
[0077] Each of the gas nozzles 48, 50, and 52 makes a right-angled
turn at the bottom of the process chamber 8, and vertically extends
along the wafer boat 20 to the uppermost position. Since the gas
nozzles 48, 50, and 52 penetrate the sidewall of the manifold 18
side by side in a horizontal direction, their vertical portions are
also arrayed side by side around the wafer boat 20, as shown in
FIG. 2. The vertical portion of each of the gas nozzles 48, 50, and
52 is provided with a number of delivery holes 53 formed thereon
for supplying a process gas, as shown in FIG. 3. The delivery holes
53 are arrayed in a vertical direction at a position adjacent to
the edges of the wafers W, so that they are distributed
substantially entirely over the vertical length of the stacked
wafers W.
[0078] The gas nozzles 48, 50, and 52 are respectively connected to
gas passages 60, 62, and 64 provided with flow rate controllers 54,
56, and 58, such as mass-flow controllers, and switching valves 55,
57, and 59. The gas passages 60, 62, and 64 are arranged to
respectively supply a silane family gas, a nitriding gas, and a
carbon hydride gas at controlled flow rates. For example, the
silane family gas is DCS gas, the nitriding gas is NH.sub.3 gas,
and the carbon hydride gas is ethylene (C.sub.2H.sub.4) gas.
[0079] The gas supply section 40 also includes an inactive gas
supply circuit 72 for supplying an inactive gas (to be used as
carrier gas or purge gas). The inactive gas supply circuit 72
includes inactive gas lines 76a, 76b, and 76c respectively
connected to the gas passages 60, 62, and 64. The inactive gas
lines 76a, 76b, and 76c are respectively provided with flow rate
controllers 74a, 74b, and 74c, such as mass-flow controllers, and
switching valves 75a, 75b, and 75c. For example, N.sub.2 gas or Ar
is used as the inactive gas.
[0080] To summarize, the gas supply circuits 42, 44, and 46 of the
apparatus according to the first embodiment respectively include
gas nozzles 48, 50, and 52, each of which can supply the
corresponding reactive gas and an inactive gas selectively or
simultaneously. Each of the nozzles 48, 50, and 52 is provided with
a number of delivery holes 53 formed thereon, which are arrayed in
a vertical direction at a position adjacent to the edges of the
wafers W, so that they are distributed substantially entirely over
the vertical length of the stacked wafers W. An inner exhaust
passage 9 is formed along the inner surface of the inner tube 4
around the wafers W. The inner exhaust passage 9 extends in a
vertical direction at a position adjacent to the edges of the
wafers W, so that it is present substantially entirely over the
vertical length of the stacked wafers W. At the top of the inner
tube 4, the inner exhaust passage 9 communicates with the gap
(outer exhaust passage) 10 formed between the inner tube 4 and
outer tube 6 and connected to the vacuum exhaust section 39.
[0081] Next, an explanation will be given of a CVD method performed
in the apparatus described above. The following method (including
gas supply and stop) can be performed in accordance with a CVD
process recipe stored in advance in the memory section 5s of a CPU
5, e.g., in accordance with the film thickness of an silicon
nitride film to be formed. The relationship between the process gas
flow rates and the film thickness of a silicon nitride film to be
formed is also stored in advance in the memory section 5s as a
control data. Accordingly, the CPU 5 can control the gas supply
section 40 and so forth, based on the stored process recipe and
control data.
[0082] At first, when the CVD apparatus is in a waiting state with
no wafers loaded therein, the interior of the process chamber 8 is
kept at a process temperature of, e.g., about 550 .degree. C. On
the other hand, a number of wafers, e.g., 100 wafers W are
transferred into the wafer boat 20. After the wafers are
transferred, the wafer boat 20, which is at a normal temperature,
is moved up from below the process chamber 8 and loaded into the
process chamber 8. Then, the lid 26 closes the bottom port of the
manifold 18 to airtightly seal the interior of the process chamber
8.
[0083] Then, the interior of the process chamber 8 is vacuum
exhausted and kept at a predetermined process pressure.
Furthermore, the wafer temperature is increased to a process
temperature for film formation. After the temperature becomes
stable, DCS gas used as a silane family gas, ammonia gas used as a
nitriding gas, and ethylene gas used as a carbon hydride gas are
supplied from the respective nozzles 48, 50, and 52 of the gas
supply section 40 at controlled flow rates. At this time, the
following gas supply patterns are used to form a silicon nitride
film. The interior of the process chamber 8 is kept
vacuum-exhausted throughout the periods of the film formation.
[0084] FIG. 4 is a timing chart showing gas supply patterns
according to the first embodiment of the present invention. As
shown in FIG. 4, the supply periods, i.e., supply timings, of the
reactive gases of three kinds differ from each other. Specifically,
one cycle is formed of first supplying DCS gas (T1), then supplying
NH.sub.3 gas (T3), and lastly supplying C.sub.2H.sub.4 gas (T5).
This cycle is continuously repeated a plurality of times. Between
the gas supply periods T1, T3, and T5, intermitting periods T2, T4,
and T6 are respectively interposed, where all the three reactive
gases are stopped and purging is performed with an inactive
gas.
[0085] The flow rate of DCS gas is set at 50 to 2000 sccm, e.g.,
300 sccm, the flow rate of NH.sub.3 gas is set at 150 to 5000 sccm,
e.g., 1000 sccm, and the flow rate of C.sub.2H.sub.4 gas is set at
50 to 2000 sccm, e.g., 500 sccm. The process temperature is set at
a constant value of 450 to 600.degree. C., e.g., 550.degree. C.,
and the process pressure is set at 13 Pa to 1.33 kPa, e.g., 133 Pa
(1 Torr) during the gas supply periods T1, T3, and T5, and at 13 to
133 Pa, e.g., 40 Pa (0.3 Torr) during the intermitting periods T2,
T4, and T6. Each one (one pulse) of the gas supply periods T1, T3,
and T5 is set at 15 to 60 seconds, while each one of the
intermitting periods T2, T4, and T6 is set at 30 to 180 seconds.
For example, where the gas supply period is set at 30 seconds and
the intermitting period is set at 30 seconds, the length of one
cycle T1 to T6 totals around three minutes.
[0086] In each cycle T1 to T6, the following process proceeds on
the surface of each wafer W. Specifically, in the first supply
period T1 where the first reactive gas or DCS gas is supplied, the
DCS gas is adsorbed on the surface of the wafer W. In the second
supply period T3 where the second reactive gas or NH.sub.3 gas is
supplied, the NH.sub.3 gas acts on the adsorbed DCS gas on the
surface of the wafer W, and a unit layer of silicon nitride is
thereby formed on the surface of the wafer W. In the third supply
period T5 where the third reactive gas or C.sub.2H.sub.4 gas is
supplied, n-bonds of C.dbd.C double bonds of the C.sub.2H.sub.4 gas
are split and react with silicon nitride, so that carbon components
are contained in the unit layer of silicon nitride. Thin unit
layers thus formed by respective cycles (T1 to T6) are stacked to
complete a silicon nitride film that contains carbon components and
has a predetermined thickness.
[0087] In the intermitting periods T2, T4, and T6, purging is
performed with an inactive gas, thereby removing unnecessary gases
from the surface of the wafer W. Since the interior of the process
chamber 8 is kept vacuum-exhausted throughout the periods T1 to T6
of the film formation, the purging can be performed by stopping
supply of the three gases, and only supplying an inactive gas, such
as N.sub.2 gas, from the delivery holes 53 of the respective
nozzles 48, 50, and 52. In this respect, only vacuum-exhaust of the
interior of the process chamber 8 may be maintained, without
supplying an inactive gas.
[0088] As described above, when a silicon nitride film is formed on
a wafer surface, a carbon hydride gas, such as C.sub.2H.sub.4 gas,
is supplied into the process chamber 8, and carbon components are
thereby contained in the silicon nitride film. This brings about a
low etching rate of the silicon nitride film surface relative to
dilute hydrofluoric acid used in a cleaning process or etching
process, even though the film-formation temperature is set at,
e.g., 550.degree. C., which is lower than the conventional
film-formation temperature of, e.g., about 760.degree. C. As a
consequence, it is possible to prevent the silicon nitride film
from being excessively etched during the cleaning process, thereby
improving the controllability in the film thickness. Furthermore,
it is possible for the silicon nitride film to sufficiently
function as an etching stopper film.
[0089] Each of the intermitting periods T2, T4, and T6 functions as
a reforming period for improving the quality of the film formed on
the surface of the wafer W. The reforming behavior in the
intermitting periods is thought to proceed as follows.
Specifically, when a silicon nitride film containing carbon atoms
is formed, some C1 atoms derived from DCS gas cannot separate from
the uppermost surface of the thin film during the deposition, but
bond thereto in an activated state. In the intermitting period
where supply of the DCS gas is stopped, C atoms or N atoms derived
from C.sub.2H.sub.4 gas or NH.sub.3 gas replace the C1 atoms in the
uppermost surface of the thin film. As a consequence, the film
decreases in C1 components contained therein, thereby providing a
lower etching rate. Particularly, where C.sub.2H.sub.4 gas is used,
C atoms taken into the silicon nitride film increase, thereby
providing a still lower etching rate.
[0090] In the apparatus according to the first embodiment, the gas
supply periods T1, T3, and T5 are performed such that the
respective gases of three kinds are forcibly fed into the gaps
between the wafers W in almost horizontal directions from the
delivery holes 53 of the corresponding one of the nozzles 48, 50,
and 52 (see arrows A1 in FIG. 3). Furthermore, the intermitting
periods T2, T4, and T6 used as purging periods are performed such
that an inactive gas is forcibly fed into the gaps between the
wafers W in almost horizontal directions from the delivery holes 53
of the corresponding one of the nozzles 48, 50, and 52 (see arrows
A1 in FIG. 3). The gases thus supplied are exhausted by the agency
of the vacuum exhaust section 39 from the gaps between the wafers W
and flow upward through the inner exhaust passage 9 that extends in
a vertical direction at a position adjacent to the edges of the
wafers W (see arrows A2 in FIG. 3).
[0091] The gas supply and exhaust described above allows all the
wafers W to be equally supplied with the reactive gases,
irrespective of the position of the wafers W in a vertical
direction. As a consequence, films formed on the wafers W are
improved in the inter-substrate uniformity (uniformity among
wafers) in terms of characteristics, such as the quality and
thickness of the films. Furthermore, since the gases are forcibly
fed into the gaps between the wafers W, the reactive gases are
efficiently exchanged on the surface of the wafers W. As a
consequence, the purging periods (intermitting periods) can be
shorter to shorten each cycle T1 to T6, thereby improving the
productivity by that much.
[0092] Since an inactive gas is supplied through the nozzles 48,
50, and 52, by-products are prevented from being deposited in the
nozzles 48, 50, and 52 or at the delivery holes 53. In this
respect, each of the purging periods may be performed such that an
inactive gas is supplied through only one nozzle that has been used
to supply the corresponding reactive gas until immediately before
it. In other words, it is optional to use the other nozzles along
with the former one to supply an inactive gas.
Second Embodiment
[0093] FIG. 5 is a sectional view showing the process chamber of a
CVD apparatus according to a second embodiment of the present
invention. FIG. 6 is an enlarged view showing an upper portion of
the process chamber of the apparatus shown in FIG. 5, and the gas
flow formed therein. This apparatus is also arranged to alternately
supply DCS gas used as a silane family gas, ammonia gas used as a
nitriding gas, and ethylene gas used as a carbon hydride gas, so as
to form a silicon nitride film.
[0094] The apparatus shown in FIG. 5 is similar to the apparatus
shown in FIG. 1, but has a different arrangement in relation to the
exhaust system. As shown in FIGS. 5 and 6, a plurality of exhaust
holes 81 are formed in an inner tube 4X on a second side opposite a
first side where delivery holes 53 are arrayed on gas nozzles 48,
50, and 52. The exhaust holes 81 are arrayed in a vertical
direction at a position adjacent to the edges of wafers W, so that
they are distributed substantially entirely over the vertical
length of the stacked wafers W. The exhaust holes 81 communicate
with a gap (outer exhaust passage) 10 formed between the inner tube
4X and outer tube 6 and connected to a vacuum exhaust section 39.
The inner tube 4X has a top portion completely closed by a top
plate 80 to prevent gases from flowing out.
[0095] A CVD method performed in the apparatus shown in FIG. 5 is
substantially the same as that explained with reference to the
apparatus shown in FIG. 1. In this method, gas supply patterns used
are as those shown in the timing chart of FIG. 4. Also in the
apparatus shown in FIG. 5, each of the nozzles 48, 50, and 52 is
arranged to forcibly feed gases from the delivery holes 53 into the
gaps between the wafers W in almost horizontal directions (see
arrows AS in FIG. 6). On the other hand, the gases thus supplied
are drawn and exhausted by the agency of the vacuum exhaust section
39 from the gaps between the wafers W through the exhaust holes 81
in almost horizontal directions into the outer exhaust passage 10
(see arrows A6 in FIG. 6).
[0096] The gas supply and exhaust described above allows the
apparatus shown in FIG. 5 to provide the following effects in
addition to those of the apparatus shown in FIG. 1. Specifically,
the gases are drawn from the gaps between the wafers W through the
exhaust holes 81 in almost parallel with the surface of the wafers
W, a uniform laminar flow tends to be formed from one end to the
other on the surface of each wafer W. As a consequence, a film
formed on each wafer W is improved in the planar uniformity
(uniformity on the surface of one wafer) in terms of
characteristics, such as the quality and thickness of the film.
Furthermore, since the exhaust holes 81 are arrayed at a position
adjacent to the edges of the wafers W, the gases are more
efficiently exhausted from the gaps between the wafers W. As a
consequence, the purging periods (intermitting periods) can be
shorter to shorten each cycle T1 to T6, thereby improving the
productivity by that much.
Third Embodiment
[0097] FIG. 7 is a sectional view showing the process chamber of a
CVD apparatus according to a third embodiment of the present
invention. FIG. 8 is a plan view of the apparatus shown in FIG. 7.
This apparatus is also arranged to alternately supply DCS gas used
as a silane family gas, ammonia gas used as a nitriding gas, and
ethylene gas used as a carbon hydride gas, so as to form a silicon
nitride film.
[0098] The apparatus shown in FIG. 7 is similar to the apparatus
shown in FIG. 5, but has a process chamber 8X of the single tube
type with no inner tube. The process chamber 8X is provided with a
thin shape exhaust pipe 85 extending vertically on a side opposite
to a side where gas nozzles 48, 50, and 52 extend vertically, with
stacked wafers W interposed therebetween (i.e., with a wafer boat
20 interposed therebetween). The exhaust pipe 85 is defined by a
casing 87 airtightly connected onto the inner surface of the quartz
tube by welding. The casing 87 is provided with a plurality of
exhaust holes 86 formed in the wall facing the wafers W. The
exhaust holes 86 are arrayed in a vertical direction at a position
adjacent to the edges of the wafers W, so that they are distributed
substantially entirely over the vertical length of the stacked
wafers W.
[0099] Although the apparatus shown in FIG. 7 has the process
chamber 8X of the single tube type, it can provide almost the same
operations and effects as those of the apparatus shown in FIG.
5.
Fourth Embodiment
[0100] FIG. 9 is a sectional view showing the process chamber of a
CVD apparatus according to a fourth embodiment of the present
invention. This apparatus is also arranged to alternately supply
DCS gas used as a silane family gas, ammonia gas used as a
nitriding gas, and ethylene gas used as a carbon hydride gas, so as
to form a silicon nitride film.
[0101] The apparatus shown in FIG. 9 is similar to the apparatus
shown in FIG. 5, but has an exhaust port 38X formed at the top of
an outer tube 6 to exhaust the atmosphere in a process chamber 8.
The exhaust port 38X is connected to a vacuum exhaust section 39
including a vacuum pump and so forth, through a pipe passing
through the top of a heating cover 16 (see FIG. 1). Since the
exhaust port 38X is disposed at the top of the process chamber 8,
the apparatus can be made compact as a whole. In the other
respects, the apparatus shown in FIG. 9 can provide almost the same
operations and effects as those of the apparatus shown in FIG.
5.
Matters Common to First to Fourth Embodiments
[0102] The supply order of the reactive gases shown in the timing
chart of FIG. 4 is only an example, and may be arbitrarily changed.
However, in processing a target substrate having a silicon surface,
it is preferable to first supply a process gas containing C, so as
to form Si--C bonds in the silicon surface and thereby protect the
silicon surface. Specifically, it is preferable to first supply DCS
gas alone (or along with C.sub.2H.sub.4 gas) and then supply
NH.sub.3 gas. If NH.sub.3 gas is first supplied, N--Si bonds are
formed in the wafer surface, which are low in chemical resistance
(i.e., easy to etch). In order to prevent this problem, DCS gas
and/or C.sub.2H.sub.4 gas is first supplied to form Si--C bonds,
which are high in chemical resistance (i.e., difficult to
etch).
[0103] C.sub.2H.sub.4 (ethylene) has been given as an example of a
carbon hydride gas for a silicon nitride film to contain carbon
components. In this respect, the carbon hydride gas may be a single
or a plurality of gases selected from the group consisting of
acetylene, ethylene, methane, ethane, propane, and butane. For
example, where the carbon hydride gas is ethane, the gas is
preferably preheated to about 500 to 1000.degree. C., and then
supplied into the process chamber 8.
[0104] C.sub.2H.sub.4 gas or the carbon hydride gas is used to
reduce the etching rate of a silicon nitride film relative to
dilute hydrofluoric acid. Accordingly, depending on the intended
use of a silicon nitride film, no carbon hydride gas needs to be
supplied, i.e., the carbon hydride gas supply circuit 46 (see FIG.
1) is unnecessary. In this case, the timing chart of FIG. 4 is
modified such that each cycle for forming a unit layer of a silicon
nitride film is formed of the periods T1 to T4.
[0105] Dichlorosilane (DCS) has been given as an example of a
silane family gas for forming a silicon nitride film. In this
respect, suitably for the apparatus according to any one of the
first to fourth embodiments, the silane family gas for forming a
silicon nitride film may be a single or a plurality of gases
selected from the group consisting of monosilane (SiH.sub.4),
disilane (Si.sub.2H.sub.6), trichlorosilane (SiHCl.sub.3),
tetra-chlorosilane (SiCl.sub.4), and bistertialbutylaminosilane
(BTBAS).
[0106] The apparatus according to any one of the first to fourth
embodiments may be applied to a process for forming a film other
than a silicon nitride film. One example is a process for forming
an alumina (Al.sub.2O.sub.3) film. In this case, an organic metal
gas containing aluminum, such as Al(CH.sub.3).sub.3, is used as a
first reactive gas, and an oxidizing gas, such as O.sub.2, O.sub.3,
or H.sub.2O, is used as a second reactive gas.
[0107] In the apparatus according to any one of the first to fourth
embodiments, since all the gas nozzles 48, 50, and 52 extend to the
uppermost wafer W, it is necessary to consider the type of reactive
gas to be supplied therethrough. Specifically, where a reactive gas
has a low bond-dissociation energy (easy to decompose), or a low
vapor pressure (difficult to uniformly supply up to the uppermost
position), it does not suit a nozzle long in a vertical direction.
In light of this, a gas supplied through the gas nozzles 48, 50,
and 52 preferably has a vapor pressure of 2.66 kPa or more, and a
bond-dissociation energy of 250 kJ/mol or more, and more preferably
has a vapor pressure of 4 kPa or more, and a bond-dissociation
energy of 300 kJ/mol or more.
Fifth Embodiment
[0108] FIG. 10 is a sectional view showing a CVD apparatus
according to a fifth embodiment of the present invention. FIG. 11
is an enlarged view showing an upper portion of the process chamber
of the apparatus shown in FIG. 10, and the gas flow formed therein.
This CVD apparatus 102 is arranged to alternately supply a first
gas consisting essentially of an organic metal gas containing
tantalum, and a second gas consisting essentially of an oxidizing
gas, so as to form a tantalum oxide film. For example, a metal
alkoxide of tantalum, such as Ta(OC.sub.2H.sub.5).sub.5
(pentoethoxytantalum: PET) gas and H.sub.2O gas (water vapor) are
used to deposit a tantalum oxide film (Ta.sub.2O.sub.5).
[0109] Although the apparatus shown in FIG. 10 is similar to the
apparatus shown in FIG. 1, it has a gas supply section and a
control section both totally different from those of the apparatus
shown in FIG. 1, due to difference in deposition film.
Specifically, a gas supply section 140 is connected to the side of
a manifold 18 to supply predetermined process gases into an inner
tube 4. More specifically, the gas supply section 140 includes an
organic metal gas supply circuit 142, and an oxidizing gas supply
circuit 144. The gas supply circuits 142 and 144 respectively
include gas nozzles 148 and 150, which penetrate the sidewall of
the manifold 18 side by side in a horizontal direction. However,
for the sake of convenience, FIG. 10 shows the gas nozzles 148 and
150 in a state where they penetrate the sidewall of the manifold 18
side by side in a vertical direction.
[0110] The gas nozzle 148 for supplying PET used as an organic
metal gas is opened upward at the bottom of the process chamber 8.
The gas nozzle 150 for supplying water vapor used as an oxidizing
gas makes a right-angled turn at the bottom of the process chamber
8, and vertically extends along a wafer boat 20 to the uppermost
position. The vertical portion of the gas nozzle 150 is provided
with a number of delivery holes 153 formed thereon for supplying a
process gas, as shown in FIG. 11. The delivery holes 153 are
arrayed in a vertical direction at a position adjacent to the edges
of wafers W, so that they are distributed substantially entirely
over the vertical length of the stacked wafers W.
[0111] The gas nozzles 148 and 150 are respectively connected to
gas passages 160 and 162 provided with flow rate controllers 154
and 156, such as mass-flow controllers, and switching valves 155
and 157. The gas passages 160 and 162 are arranged to respectively
supply an organic metal gas and an oxidizing gas at controlled flow
rates. For example, the organic metal gas is PET gas, and the
oxidizing gas is water vapor.
[0112] The gas supply section 140 also includes an inactive gas
supply circuit 72 for supplying an inactive gas (to be used as
carrier gas or purge gas). The inactive gas supply circuit 72
includes inactive gas lines 76a and 76b respectively connected to
the gas passages 160 and 162. The inactive gas lines 76a and 76b
are respectively provided with flow rate controllers 74a and 74b,
such as mass-flow controllers, and switching valves 75a and 75b.
For example, N.sub.2 gas or Ar is used as the inactive gas.
[0113] To summarize, the gas supply circuits 142 and 144 of the
apparatus according to the fifth embodiment respectively include
gas nozzles 148 and 150, each of which can supply the corresponding
reactive gas and an inactive gas selectively or simultaneously. The
gas nozzle 148 is provided with a delivery hole opened upward at
the bottom of the process chamber 8. The nozzle 150 is provided
with a number of delivery holes 153 formed thereon, which are
arrayed in a vertical direction at a position adjacent to the edges
of the wafers W, so that they are distributed substantially
entirely over the vertical length of the stacked wafers W. An inner
exhaust passage 9 is formed along the inner surface of the inner
tube 4 around the wafers W. The inner exhaust passage 9 extends in
a vertical direction at a position adjacent to the edges of the
wafers W, so that it is present substantially entirely over the
vertical length of the stacked wafers W. At the top of the inner
tube 4, the inner exhaust passage 9 communicates with a gap (outer
exhaust passage) 10 formed between the inner tube 4 and outer tube
6 and connected to a vacuum exhaust section 39.
[0114] Next, an explanation will be given of a CVD method performed
in the apparatus described above. The following method (including
gas supply and stop) can be performed in accordance with a CVD
process recipe stored in advance in the memory section 5s of a CPU
5, e.g., in accordance with the film thickness of a tantalum oxide
film to be formed. The relationship between the process gas flow
rates and the film thickness of a tantalum oxide film to be formed
is also stored in advance in the memory section 5s as a control
data. Accordingly, the CPU 5 can control the gas supply section 140
and so forth, based on the stored process recipe and control
data.
[0115] At first, when the CVD apparatus is in a waiting state with
no wafers loaded therein, the interior of the process chamber 8 is
kept at a process temperature of, e.g., about 300.degree. C. On the
other hand, a number of wafers, e.g., 100 wafers W are transferred
into the wafer boat 20. After the wafers are transferred, the wafer
boat 20, which is at a normal temperature, is moved up from below
the process chamber 8 and loaded into the process chamber 8. Then,
the lid 26 closes the bottom port of the manifold 18 to airtightly
seal the interior of the process chamber 8.
[0116] Then, the interior of the process chamber 8 is vacuum
exhausted and kept at a predetermined process pressure.
Furthermore, the wafer temperature is increased to a process
temperature for film formation. After the temperature becomes
stable, PET gas used as an organic metal gas and water vapor used
as an oxidizing gas are supplied from the respective nozzles 148
and 150 of the gas supply section 140 at controlled flow rates. At
this time, the following gas supply patterns are used to form a
tantalum oxide film. The interior of the process chamber 8 is kept
vacuum-exhausted throughout the periods of the film formation.
[0117] FIG. 12 is a timing chart showing gas supply patterns
according to the fifth embodiment of the present invention. As
shown in FIG. 12, the supply periods, i.e., supply timings, of the
reactive gases of two kinds differ from each other. Specifically,
one cycle is formed of first supplying water vapor (T11), and then
supplying PET gas (T13). This cycle is continuously repeated a
plurality of times. The PET gas is supplied along with an inactive
gas, such as N.sub.2 gas, used as a carrier gas. Between the gas
supply periods T11 and T13, intermitting periods T12 and T14 are
respectively interposed, where all the two reactive gases are
stopped and purging is performed with an inactive gas.
[0118] The flow rate of water vapor is set at 10 to 1000 sccm, and
the flow rate of PET gas is set at about 0.05 to 5.0 ml/min in a
value converted into liquid PET, and the flow rate of N.sub.2 gas
used as a carrier gas is set at 1000 sccm. The process temperature
is set at a constant value of 200 to 450.degree. C., and the
process pressure is set at 13 to 133 Pa during the gas supply
periods T11 and T13, and at 13 to 133 Pa during the intermitting
periods T12 and T14. Each one (one pulse) of the gas supply periods
T11 and T13 is set at 60 to 120 seconds, while each one of the
intermitting periods T12 and T14 is set at 30 to 60 seconds. For
example, where the gas supply period is set at 60 seconds and the
intermitting period is set at 30 seconds, the length of one cycle
T11 to T14 totals around three minutes.
[0119] In each cycle T11 to T14, the following process proceeds on
the surface of each wafer W. Specifically, in the first supply
period T11 where the first reactive gas or water vapor is supplied,
the water vapor is adsorbed on the surface of the wafer W. In the
second supply period T13 where the second reactive gas or PET gas
is supplied, the PET gas acts on the adsorbed water vapor on the
surface of the wafer W, and a unit layer of tantalum oxide is
thereby formed on the surface of the wafer W. Thin unit layers thus
formed by respective cycles (T11 to T14) are stacked to complete a
tantalum oxide film having a predetermined thickness.
[0120] In the intermitting periods T12 and T14, purging is
performed with an inactive gas, thereby removing unnecessary gases
from the surface of the wafer W. Since the interior of the process
chamber 8 is kept vacuum-exhausted throughout the periods T11 to
T14 of the film formation, the purging can be performed by stopping
supply of the two gases, and only supplying an inactive gas, such
as N.sub.2 gas, from the nozzle 148 and delivery holes 153 of the
nozzle 150. In this respect, only vacuum-exhaust of the interior of
the process chamber 8 may be maintained, without supplying an
inactive gas.
[0121] As described above, since thin unit layers are stacked to
form a tantalum oxide film, the surface morphology and electrical
characteristics of the tantalum oxide film are improved. Each of
the intermitting periods T12 and T14 functions as a reforming
period for improving the quality of the film formed on the surface
of the wafer W.
[0122] In the apparatus according to the fifth embodiment, the gas
supply period T11 is performed such that water vapor is forcibly
fed into the gaps between the wafers W in almost horizontal
directions from the delivery holes 153 of the nozzle 150 (see
arrows A11 in FIG. 11). Furthermore, the intermitting period T12
used as a purging period is performed such that an inactive gas is
forcibly fed into the gaps between the wafers W in almost
horizontal directions from the delivery holes 153 of the nozzle 150
(see arrows A11 in FIG. 11). The gases thus supplied are exhausted
by the agency of the vacuum exhaust section 39 from the gaps
between the wafers W and flow upward through the inner exhaust
passage 9 that extends in a vertical direction at a position
adjacent to the edges of the wafers W (see arrows A12 in FIG.
11).
[0123] The gas supply and exhaust described above allows all the
wafers W to be equally supplied with water vapor, irrespective of
the position of the wafers W in a vertical direction. As a
consequence, films formed on the wafers W are improved in the
inter-substrate uniformity (uniformity among wafers) in terms of
characteristics, such as the quality and thickness of the films.
Furthermore, since the gases are forcibly fed into the gaps between
the wafers W, the reactive gases are efficiently exchanged on the
surface of the wafers W. As a consequence, the purging periods
(intermitting periods) can be shorter to shorten each cycle T11 to
T14, thereby improving the productivity by that much.
[0124] On the other hand, PET gas, which has a low
bond-dissociation energy, is supplied from the delivery hole of the
nozzle 148 opened at the bottom of the process chamber 8. The PET
gas is drawn upward and flows in the gaps between the wafers W by
the agency of the vacuum exhaust section 39. Since the nozzle 148
includes substantially no vertical portion that receives the
influence of heat in the process chamber 8, the PET gas is less
likely to be decomposed (a cause of by-product deposition) in the
nozzle 148.
[0125] Since an inactive gas is supplied through the nozzles 148
and 150, by-products are prevented from being deposited in the
nozzles 148 and 150 or at the delivery holes 153. In this respect,
each of the purging periods may be performed such that an inactive
gas is supplied through only one nozzle that has been used to
supply the corresponding reactive gas until immediately before it.
In other words, it is optional to use the other nozzle along with
the former one to supply an inactive gas.
Sixth Embodiment
[0126] FIG. 13 is a sectional view showing the process chamber of a
CVD apparatus according to a sixth embodiment of the present
invention. FIG. 14 is an enlarged view showing an upper portion of
the process chamber of the apparatus shown in FIG. 13, and the gas
flow formed therein. This apparatus is also arranged to alternately
supply PET gas used as an organic metal gas containing tantalum and
water vapor used as an oxidizing gas, so as to form a tantalum
oxide film.
[0127] The apparatus shown in FIG. 13 is similar to the apparatus
shown in FIG. 10, but has a different arrangement in relation to
the exhaust system. As shown in FIGS. 13 and 14, an exhaust port
38X is formed at the top of an outer tube 6 to exhaust the
atmosphere in a process chamber 8. The exhaust port 38X is
connected to a vacuum exhaust section 39 including a vacuum pump
and so forth, through a pipe passing through the top of a heating
cover 16 (see FIG. 10).
[0128] A plurality of exhaust holes 81 are formed in an inner tube
4X on a second side opposite a first side where delivery holes 153
are arrayed on a gas nozzle 150. The exhaust holes 81 are arrayed
in a vertical direction at a position adjacent to the edges of
wafers W, so that they are distributed substantially entirely over
the vertical length of the stacked wafers W. The exhaust holes 81
communicate with a gap (outer exhaust passage) 10 formed between
the inner tube 4X and outer tube 6 and connected to a vacuum
exhaust section 39. The inner tube 4X has a top portion completely
closed by a top plate 80 to prevent gases from flowing out.
[0129] A CVD method performed in the apparatus shown in FIG. 13 is
substantially the same as that explained with reference to the
apparatus shown in FIG. 10. In this method, gas supply patterns
used are as those shown in the timing chart of FIG. 12. Also in the
apparatus shown in FIG. 13, the nozzle 150 is arranged to forcibly
feed gases from the delivery holes 153 into the gaps between the
wafers W in almost horizontal directions (see arrows A15 in FIG.
14). The nozzle 148 is arranged to feed gases from the delivery
hole such that the gases flow upward from the bottom of the process
chamber 8 and flow in the gaps between the wafers W. On the other
hand, the gases thus supplied are drawn and exhausted by the agency
of the vacuum exhaust section 39 from the gaps between the wafers W
through the exhaust holes 81 in almost horizontal directions into
the outer exhaust passage 10 (see arrows A16 in FIG. 14).
[0130] The gas supply and exhaust described above allows the
apparatus shown in FIG. 13 to provide the following effects in
addition to those of the apparatus shown in FIG. 10. Specifically,
the gases are drawn from the gaps between the wafers W through the
exhaust holes 81 in almost parallel with the surface of the wafers
W, a uniform laminar flow tends to be formed from one end to the
other on the surface of each wafer W. As a consequence, a film
formed on each wafer W is improved in the planar uniformity
(uniformity on the surface of one wafer) in terms of
characteristics, such as the quality and thickness of the film.
Furthermore, since the exhaust holes 81 are arrayed at a position
adjacent to the edges of the wafers W, the gases are more
efficiently exhausted from the gaps between the wafers W. As a
consequence, the purging periods (intermitting periods) can be
shorter to shorten each cycle T11 to T14, thereby improving the
productivity by that much.
Seventh Embodiment
[0131] FIG. 15 is a sectional view showing the process chamber of a
CVD apparatus according to a seventh embodiment of the present
invention. FIG. 16 is a plan view of the apparatus shown in FIG.
15. This apparatus is also arranged to alternately supply PET gas
used as an organic metal gas containing tantalum and water vapor
used as an oxidizing gas, so as to form a tantalum oxide film.
[0132] The apparatus shown in FIG. 15 is similar to the apparatus
shown in FIG. 13, but has a process chamber 8X of the single tube
type with no inner tube. The process chamber 8X is provided with a
thin shape exhaust pipe 85 extending vertically on a side opposite
to a side where a gas nozzle 150 extends vertically, with stacked
wafers W interposed therebetween (i.e., with a wafer boat 20
interposed therebetween). The exhaust pipe 85 is defined by a
casing 87 airtightly connected onto the inner surface of the quartz
tube by welding. The casing 87 is provided with a plurality of
exhaust holes 86 formed in the wall facing the wafers W. The
exhaust holes 86 are arrayed in a vertical direction at a position
adjacent to the edges of the wafers W, so that they are distributed
substantially entirely over the vertical length of the stacked
wafers W.
[0133] Although the apparatus shown in FIG. 15 has the process
chamber 8X of the single tube type, it can provide almost the same
operations and effects as those of the apparatus shown in FIG.
13.
Matters Common to Fifth to Seventh Embodiments
[0134] The supply order of the reactive gases shown in the timing
chart of FIG. 12 is only an example, and may be reversed. PET has
been given as an example of an organic metal gas for forming a
tantalum oxide film. In this respect, another organic metal gas
containing tantalum, such as TBTDET
(trisdiethylaminotertbutyl-imino tantalum: (C.sub.4H.sub.10N).sub.-
3Ta(NC.sub.4H.sub.9)), may be used. Water vapor has been given as
an example of an oxidizing gas for forming a tantalum oxide film.
In this respect, another oxidizing gas, such as O.sub.2 or O.sub.3,
may be used.
[0135] The apparatus according to any one of the fifth to seventh
embodiments may be applied to a process for forming a film other
than a tantalum oxide film. One example is a process for forming a
silicon nitride film by supplying a silane family gas having a low
bond-dissociation energy, such as hexachlorodisilane (HCD:
Si.sub.2Cl.sub.6) gas, and NH.sub.3 gas. In this case, the silane
family gas is supplied from the nozzle 148, and the NH.sub.3 gas is
supplied from the nozzle 150. Another example is a process for
forming a hafnium oxide (HfO.sub.x) film by supplying TDMAH
(tetrakis(dimethylamino)hafnium- : Hf[N(CH.sub.3).sub.2].sub.4) or
TEMAH (tetrakis(ethylmethylamino)hafnium- :
Hf[N(CH.sub.3)(C.sub.2H.sub.5)].sub.4) gas, and an oxidizing gas.
In this case, the TDMAH or TEMAH gas is supplied from the nozzle
148, and the oxidizing gas is supplied from the nozzle 150.
[0136] The apparatus according to any one of the fifth to seventh
embodiments may be applied to a process for forming still another
film. One example is a process for forming a silicon nitride film
by supplying a silane family gas and a nitriding gas, as described
with reference to first to fourth embodiments. Another example is a
process for forming an alumina (Al.sub.2O.sub.3) film by supplying
an organic metal gas containing aluminum, and an oxidizing gas, as
described with reference to first to fourth embodiments. In these
cases, it is preferable to use the shorter nozzle 148 to supply a
gas easier to decompose or lower in vapor pressure.
[0137] To summarize, the apparatus according to any one of the
fifth to seventh embodiments is preferably applied to a case where
two reactive gases used greatly differ from each other in a
characteristic, such as bond-dissociation energy or vapor pressure.
Specifically, where a reactive gas has a low bond-dissociation
energy (easy to decompose), or a low vapor pressure (difficult to
uniformly supply up to the uppermost position), it does not suit
the nozzle 150 long in a vertical direction. In light of this, a
reactive gas that has a vapor pressure of 1.33 kPa or less, or a
bond-dissociation energy of 250 kJ/mol or. less, is supplied from
the shorter nozzle 148. On the other hand, a reactive gas that
satisfies the requirement of vapor pressure or bond-dissociation
energy described in "Matters common to first to fourth embodiments"
is supplied from the longer nozzle 150.
[0138] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *