U.S. patent application number 15/014718 was filed with the patent office on 2017-03-02 for semiconductor manufacturing method and semiconductor manufacturing apparatus.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. The applicant listed for this patent is KABUSHIKI KAISHA TOSHIBA. Invention is credited to Kazumasa ITO, Takanobu Itoh, Ryota Nakanishi, Seiichi Omoto.
Application Number | 20170062286 15/014718 |
Document ID | / |
Family ID | 58104204 |
Filed Date | 2017-03-02 |
United States Patent
Application |
20170062286 |
Kind Code |
A1 |
ITO; Kazumasa ; et
al. |
March 2, 2017 |
SEMICONDUCTOR MANUFACTURING METHOD AND SEMICONDUCTOR MANUFACTURING
APPARATUS
Abstract
A semiconductor manufacturing method according to an embodiment
includes forming a first film on a semiconductor substrate. The
semiconductor manufacturing method includes forming cavities in the
first film. The semiconductor manufacturing method includes forming
a second film inside the cavities by a CVD method using first gas
containing a component of the second film, detecting a first time
point at which the second film blocks openings of the cavities in
forming the second film, and ending forming of the second film at a
second time point at which a predetermined time has elapsed from
the first time point.
Inventors: |
ITO; Kazumasa; (Kawasaki,
JP) ; Omoto; Seiichi; (Yokkaichi, JP) ; Itoh;
Takanobu; (Yokkaichi, JP) ; Nakanishi; Ryota;
(Yokkaichi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA TOSHIBA |
Minato-ku |
|
JP |
|
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
Minato-ku
JP
|
Family ID: |
58104204 |
Appl. No.: |
15/014718 |
Filed: |
February 3, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62212737 |
Sep 1, 2015 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 27/1157 20130101;
C23C 16/06 20130101; H01L 21/76879 20130101; H01L 27/11582
20130101; C23C 16/045 20130101; H01L 22/26 20130101; C23C 16/52
20130101 |
International
Class: |
H01L 21/66 20060101
H01L021/66; H01L 27/115 20060101 H01L027/115; C23C 16/52 20060101
C23C016/52; H01L 21/768 20060101 H01L021/768; H01L 23/532 20060101
H01L023/532; C23C 16/06 20060101 C23C016/06; H01L 23/522 20060101
H01L023/522; H01L 21/28 20060101 H01L021/28 |
Claims
1. A semiconductor manufacturing method comprising: forming a first
film on a semiconductor substrate; forming cavities in the first
film; and forming a second film inside the cavity by a CVD method
using first gas comprising a component of the second film,
detecting a first time point at which the second film blocks
openings of the cavities in forming the second film, and ending
forming of the second film at a second time point at which a
predetermined time has elapsed from the first time point.
2. The method of claim 1, further comprising detecting an amount of
byproducts generated in forming the second film, wherein detecting
the first time point is detecting a time point at which the amount
of byproducts has decreased.
3. The method of claim 2, wherein the byproduct is second gas
differing from the first gas.
4. The method of claim 3, wherein detecting the amount of
byproducts is detecting an amount of the second gas in discharge
gas used for forming the second film.
5. The method of claim 1, being a manufacturing method of a
three-dimensionally stacked semiconductor storage device, wherein
the first film is a stacked film in which silicon oxide films and
silicon nitride films are stacked alternately.
6. The method of claim 5, further comprising forming a recess that
penetrates the stacked film before forming the cavities, wherein
forming the cavities is removing the silicon nitride films in
respective layers selectively by bringing a chemical liquid into
contact with the silicon nitride films in respective layers through
the recess.
7. The method of claim 6, wherein the second film is word lines of
the semiconductor storage device.
8. The method of claim 7, wherein the second film contains
tungsten.
9. The method of claim 6, wherein forming the second film is
performed from inside of the cavities in respective layers that are
formed based on the stacked film to a sidewall of the recess, and
the method further comprising separating parts of the second film
that are formed inside the cavities in respective layers from each
other by removing parts of the second film that are formed on a
sidewall of the recess after forming the second film.
10. A semiconductor manufacturing apparatus comprising: a reactor
housing a semiconductor substrate having a first film including
cavities and supplying first gas containing a component of a second
film to the semiconductor substrate to form the second film inside
of the cavities; a first detector detecting a first time point at
which the second film blocks openings of the cavities; and a
controller executing control to stop supply of the first gas at a
second time point at which a predetermined time has elapsed from
the first time point.
11. The apparatus of claim 10, further comprising a second detector
detecting an amount of byproducts in the reactor, wherein the first
detector detects a time point at which the amount of byproducts has
decreased as the first time point.
12. The apparatus of claim 11, wherein the second detector detects
an amount of second gas differing from the first gas as the amount
of byproducts.
13. The apparatus of claim 12, wherein the second detector is
arranged on a discharge line of the reactor.
14. The apparatus of claim 10, manufacturing a three-dimensionally
stacked semiconductor storage device, wherein the first film
including the cavities has a plurality of layers of silicon oxide
films and the cavities are located between the silicon oxide films
in the respective layers.
15. The apparatus of claim 14, wherein the second film is word
lines of the semiconductor storage device.
16. The apparatus of claim 15, wherein the second film comprises
tungsten.
17. The apparatus of claim 14, wherein the semiconductor substrate
has a recess that penetrates the stacked film so as to be
communicated with the cavities, and the reactor forms the second
film extending from the inside of the cavities to a sidewall of the
recess.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior U.S. Provisional Patent Application No.
62/212,737 filed on Sep. 1, 2015, the entire contents of which are
incorporated herein by reference.
FIELD
[0002] Embodiments relate to a semiconductor manufacturing method
and a semiconductor manufacturing apparatus.
BACKGROUND
[0003] In a manufacturing process of a three-dimensionally stacked
memory, a stacked film of silicon oxide films and silicon nitride
films is formed on a wafer, trenches penetrating the stacked film
are formed, and thereafter a chemical liquid is brought into
contact with the silicon nitride films through the trenches to
remove the silicon nitride films selectively from the stacked film.
Subsequently, to form word lines, a CVD method using material gas
is performed to form tungsten films inside cavities in respective
layers from which the silicon nitride films have been removed.
[0004] The tungsten films are formed not only inside the cavities
in the respective layers but also on the sidewalls of the trenches
communicated with the cavities. The tungsten films on the sidewalls
of the trenches are continuous with the tungsten films in the
cavities of upper layers and the tungsten films in the cavities of
lower layers, respectively. If the tungsten films remain continuous
with one another, upper and lower word lines mutually
short-circuit. Accordingly, to isolate the upper and lower word
lines electrically, the tungsten films on the sidewalls of the
trenches are removed by etching.
[0005] Conventionally, a time point at which a predetermined time
has elapsed from start of film formation is used as an end point of
the film formation. In some cases, a difference in film-formation
rates of the tungsten films is generated between when the cavities
remain opened, that is, when the surface area of the stacked film
is large and when the cavities are blocked, that is, when the
surface area of the stacked film is small. Under this premise, when
the shapes of the openings of the cavities are non-uniform among
different wafers (lots), the film thicknesses of the tungsten films
on the sidewalls of the trenches are also non-uniform at an end
point of film formation. When the film thicknesses of the tungsten
films on the sidewalls of the trenches are non-uniform, etching
conditions of the tungsten films on the sidewalls of the trenches
cannot be uniformed among wafers. Accordingly, the manufacturing
efficiency becomes poor.
[0006] Furthermore, conventionally, the flow rate of material gas
is kept constant from start to an end point of film formation. For
this reason, after the openings of the cavities are blocked by the
tungsten films, an excessive amount of material gas is supplied
until the end point of film formation. Accordingly, the economic
efficiency becomes poor.
[0007] Therefore, in manufacturing semiconductor devices,
improvement in manufacturing efficiency and economical efficiency
has been demanded.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic sectional view showing a semiconductor
storage device according to an embodiment;
[0009] FIG. 2A is a sectional view showing a semiconductor
manufacturing method according to the embodiment, and FIG. 2B is a
sectional view showing the semiconductor manufacturing method after
FIG. 2A;
[0010] FIG. 3A is a sectional view showing the semiconductor
manufacturing method according to the embodiment after FIG. 2B, and
FIG. 3B is a sectional view showing the semiconductor manufacturing
method after FIG. 3A;
[0011] FIG. 4A is a sectional view showing the semiconductor
manufacturing method according to the embodiment after FIG. 3B, and
FIG. 4B is a sectional view showing the semiconductor manufacturing
method after FIG. 4A;
[0012] FIG. 5 is a schematic diagram showing a semiconductor
manufacturing apparatus according to the embodiment;
[0013] FIG. 6 is a flowchart showing a formation process of
tungsten films in the semiconductor manufacturing method according
to the embodiment;
[0014] FIGS. 7A and 7B are sectional views showing the
semiconductor manufacturing method after FIG. 4B;
[0015] FIGS. 8A and 8B are sectional views showing the
semiconductor manufacturing method after FIGS. 7A and 7B; and
[0016] FIGS. 9A and 9B are sectional views showing the
semiconductor manufacturing method after FIGS. 8A and 8B.
DETAILED DESCRIPTION
[0017] A semiconductor manufacturing method according to an
embodiment includes forming a first film on a semiconductor
substrate. The semiconductor manufacturing method includes forming
cavities in the first film. The semiconductor manufacturing method
includes forming a second film inside the cavities by a CVD method
using first gas containing a component of the second film,
detecting a first time point at which the second film blocks
openings of the cavities in forming the second film, and ending
forming of the second film at a second time point at which a
predetermined time has elapsed from the first time point.
[0018] Embodiments will now be explained with reference to the
accompanying drawings. The present invention is not limited to the
embodiments.
[0019] FIG. 1 is a schematic sectional view showing a semiconductor
storage device 1 manufactured by a semiconductor manufacturing
method according to an embodiment. The semiconductor storage device
1 includes a semiconductor substrate 2, a first stacked film 3, and
memory cells 4.
[0020] The semiconductor substrate 2 has a diffusion layer (not
shown) on a surface thereof.
[0021] The first stacked film 3 is arranged on the semiconductor
substrate 2. The first stacked film 3 includes insulating layers 31
and conductive layers 32. The insulating layers 31 and the
conductive layers 32 are stacked alternately and repeatedly. The
insulating layers 31 are silicon oxide films. The conductive layers
32 each include a tungsten (W) film 321 that is an example of a
second film, a TiN film 322 for growing tungsten, and an AlO film
323 that is a block film. The tungsten film 321 is in contact with
the TiN film 322. The TiN film 322 is in contact also with the AlO
film 323. The AlO film 323 is in contact also with the insulating
layer 31. For example, the conductive layers 32 are word lines. The
conductive layers 32 may include select gate lines.
[0022] The memory cells 4 are each formed into a columnar shape and
are embedded in memory holes 40 that penetrate the first stacked
film 3. The memory cells 4 each include a silicon pillar
(polysilicon) and a charge accumulating layer surrounding the
silicon pillar. For example, the charge accumulating layer has an
ONO (oxide/nitride/oxide) structure.
[0023] The semiconductor storage device 1 has trenches 5 that are
an example of a recess. The trenches 5 penetrate the first stacked
film 3.
[0024] A manufacturing method for manufacturing the semiconductor
storage device 1 in FIG. 1 is explained next.
[0025] FIG. 2A is a sectional view showing a semiconductor
manufacturing method according to the present embodiment. First, as
shown in FIG. 2A, the silicon oxide films 31 and the silicon
nitride films 301 are stacked alternately on the semiconductor
substrate 2 to form a second stacked film 300. The second stacked
film 300 is an example of a first film. For example, the silicon
oxide films 31 and the silicon nitride films 301 may be formed by a
CVD method.
[0026] FIG. 2B is a sectional view showing the semiconductor
manufacturing method after FIG. 2A. After the second stacked film
300 is formed, the memory holes 40 penetrating the second stacked
film 300 are formed as shown in FIG. 2B. For example, the memory
holes 40 may be formed by reactive ion etching (RIE).
[0027] FIG. 3A is a sectional view showing the semiconductor
manufacturing method according to the present embodiment after FIG.
2B. After the memory holes 40 are formed, the memory cells 4 are
formed in the memory holes 40 as shown in FIG. 3A. For example, the
memory cells 4 may be formed by the CVD method.
[0028] FIG. 3B is a sectional view showing the semiconductor
manufacturing method according to the present embodiment after FIG.
3A. After the memory cells 4 are embedded, the trenches 5
penetrating the second stacked film 300 are formed as shown in FIG.
3B. For example, the trenches 5 may be formed by RIE.
[0029] FIG. 4A is a sectional view showing the semiconductor
manufacturing method according to the present embodiment after FIG.
3B. After the trenches 5 are formed, the silicon nitride films 301
are selectively removed from the second stacked film 300 to form
cavities 302 between the silicon oxide films 31 in respective
layers as shown in FIG. 4A. The cavities 302 are formed by wet
etching in which a chemical liquid is brought into contact with the
silicon nitride films 301 through the trenches 5. The chemical
liquid may be a heated phosphoric acid solution. Hereinafter, a
stacked film obtained by removing the silicon nitride films 301
from the second stacked film 300 is also referred to as "third
stacked film 310". The third stacked film 310 is an example of the
first film having cavities.
[0030] FIG. 4B is a sectional view showing the semiconductor
manufacturing method after FIG. 4A. After the cavities 302 are
formed, the AlO films 323 and the TiN films 322 are formed
sequentially on the inner walls of the cavities 302 and the
sidewalls of the trenches 5 as shown in FIG. 4B. For example, the
AlO films 323 and the TiN films 322 may be formed by the CVD
method.
[0031] Next, the tungsten films 321 are formed to fill the cavities
302. At that time, the tungsten films 321 are formed to extend from
the insides of the cavities 302 to the inner walls (the sidewalls
and the bottom walls) of the trenches 5 and the upper wall of the
third stacked film 310.
[0032] FIG. 5 is a schematic diagram showing a semiconductor
manufacturing apparatus 100 according to the present embodiment.
The tungsten films 321 are formed with the semiconductor
manufacturing apparatus 100 in FIG. 5. The semiconductor
manufacturing apparatus 100 is a CVD apparatus that forms films by
the CVD method. As shown in FIG. 5, the semiconductor manufacturing
apparatus 100 includes a reactor 110, a first detector 120, a
second detector 130, and a controller 140.
[0033] The reactor 110 includes a reaction furnace 111, a gas
supplier 112, a heater 113, and a gas discharge part 114.
[0034] The reaction furnace 111 houses the semiconductor substrate
2 with the third stacked film 310. The reaction furnace 111 can
include a holder (not shown) that holds the semiconductor substrate
112.
[0035] The gas supplier 112 includes a nozzle N and ejects material
gas G supplied from a gas source S through a supply line L1 to the
semiconductor substrate 2. The material gas G is an example of
first gas. The gas supplier 112 further includes a valve V and a
mass flow controller MFC on the supply line L1. The valve V can
open and close the supply line L1. The mass flow controller MFC can
control the flow rate of the material gas G.
[0036] The heater 113 thermally decomposes the material gas G
supplied from the gas supplier 112 and generates film formation
species to form the tungsten films 321 in the cavities 302. The
heater 113 may be provided inside the reaction furnace 111 as shown
in FIG. 5. Alternatively, the heater 113 may surround the sidewall
of the reaction furnace 111 at the outside of the reaction furnace
111.
[0037] The gas discharge part 114 includes a discharge line L2 and
a discharge pump P. The gas discharge part 114 discharges gas in
the reaction furnace 111 to the outside of the reaction furnace 111
through the discharge line L2 by a suction force of the discharge
pump P.
[0038] The second detector 130 is arranged on the discharge line
L2. The second detector 130 detects an amount of byproducts that
are generated in the reaction furnace 111 when the tungsten films
321 are formed.
[0039] For example, while tungsten hexafluoride (WF6) gas and
hydrogen gas (3H.sub.2), which are examples of the material gas,
are caused to react with each other to generate tungsten (W),
hydrogen fluoride gas (6HF) is simultaneously generated as a
byproduct. The second detector 130 may detect an amount of hydrogen
fluoride gas that is an example of second gas as an amount of
byproducts.
[0040] Alternatively, the second detector 130 may detect the amount
of byproducts by infrared spectroscopy (IR).
[0041] The first detector 120 detects a time point (hereinafter,
"opening-blocking time point") at which the tungsten films 321
block openings 302a (see FIG. 4B) of the cavities 302. The
opening-blocking time point is an example of a first time point.
The openings 302a of the cavities 302 can be also considered to be
boundaries between the cavities 302 and the trenches 5. The first
detector 120 detects a time point at which the amount of byproducts
detected by the second detector 130 has decreased as the
opening-blocking time point. The first detector 120 can be embodied
as an arithmetic processing unit such as a CPU. The controller 140
may also serve as the first detector 120.
[0042] The controller 140 executes control to stop supply of the
material gas G at a time point (hereinafter, also "film-formation
end point") at which a predetermined time has elapsed from the
opening-blocking time point. The film-formation end point is an
example of a second time point. The controller 140 may close the
valve V to stop supply of the material gas G. The controller 140
can control the whole operation of the semiconductor manufacturing
apparatus 100.
[0043] As described above, the semiconductor manufacturing
apparatus 100 detects an opening-blocking time point that may be
different among the semiconductor substrates 2 (lots) as a
reference time point for detecting a film-formation end point. The
semiconductor manufacturing apparatus 100 uses a time point at
which a predetermined time has elapsed from the detected
opening-blocking time point as a film-formation end point to absorb
variation in the opening-blocking time point among the
semiconductor substrates 2.
[0044] More specifically, in forming the tungsten films 321, the
semiconductor manufacturing apparatus 100 operates as follows.
[0045] FIG. 6 is a flowchart showing a formation process of the
tungsten films 321 in the semiconductor manufacturing method
according to the present embodiment.
[0046] As shown in FIG. 6, first, the semiconductor manufacturing
apparatus 100 places the semiconductor substrate 2 with the third
stacked film 310 inside the reaction furnace 111 using an automatic
conveying mechanism (not shown) (Step S1).
[0047] Next, the gas supplier 112 supplies the material gas G to
the inside of the reaction furnace 111 (Step S2).
[0048] Next, the heater 113 heats the material gas G supplied to
the inside of the reaction furnace 111 to start forming the
tungsten films 321 in the cavities 302 of the semiconductor
substrate 2 (Step S3). The tungsten films 321 may be formed on the
inner walls of the cavities 302, the inner walls of the trenches 5,
and the upper wall of the third stacked film 310, respectively, at
an equal film-formation rate.
[0049] In forming the tungsten films 321, a main tungsten film with
a low resistance may be formed after forming an initial tungsten
film that is less likely to generate film-formation delay. For
example, B.sub.2H.sub.6, SiH.sub.4, or SiH.sub.4 and H.sub.2 are
used as reducing gas for the initial film. For example, H.sub.2 is
used as reducing gas for the main film.
[0050] Next, the second detector 130 detects an amount of
byproducts inside the reaction furnace 111 at the discharge line L2
(Step S4).
[0051] Next, to detect the opening-blocking time point, the first
detector 120 determines whether the amount of byproducts has
decreased based on the amount of byproducts detected by the second
detector 130 (Step S5).
[0052] The reason why the opening-blocking time point can be
detected by determining whether the amount of byproducts has
decreased is as follows.
[0053] The film-formation rate of the tungsten films 321 formed of
the initial film and the main film described above was calculated.
The film-formation rate before the openings 302a were blocked was
0.045 nm/sec. The film-formation rate after the openings 302a were
blocked was 0.195 nm/sec. That is, the film-formation rate after
the openings 302a were blocked was approximately four times larger
than that before the openings 302a were blocked.
[0054] The change rate of the surface area of the third stacked
film 310 was also calculated. The surface area after the openings
302a were blocked was 5.6% of that before the openings 302a were
blocked.
[0055] The generation amount of hydrogen fluoride as a byproduct
was calculated based on the film-formation rate and the change rate
of the surface area. The generation amount before the opening 302a
was blocked was 2.07 nm/sec. The generation amount after the
openings 302a were blocked was 0.51 nm/sec. That is, the generation
amount of byproducts after the openings 302a were blocked was
approximately one fourth of that before the openings 302a were
blocked.
[0056] As described above, blocking the openings 302a is
accompanied by decrease in the generation amount of byproducts.
Therefore, decrease in the generation amount of byproducts can be
an indicator for determining whether the openings 302a are
blocked.
[0057] For the above reason, the opening-blocking time point can be
detected by determining whether the amount of byproducts has
decreased.
[0058] When the amount of byproducts has not decreased (Step S5:
No), the first detector 120 does not detect the opening-blocking
time point. In this case, the first detector 120 repeats the
determination (Step S5).
[0059] FIGS. 7A and 7B are sectional views showing the
semiconductor manufacturing method after FIG. 4B. FIG. 7A shows a
state where the tungsten films 321 near the upper ends of the
memory cells 4 do not block the openings 302a. FIG. 7B shows a
state where the tungsten films 321 near the lower ends of the
memory cells 4 do not block the openings 302a.
[0060] In a state where the openings 302a are not blocked (Step S5:
No) as shown in FIGS. 7A and 7B, it is difficult to detect the
film-formation end point with accuracy because a required time for
blocking the openings 302a may vary depending on the shape of the
openings 302a. If a delay time of start of film formation is
detected based on the detected amount of byproducts before the
openings 302a are blocked and a time point at which a predetermined
time has lapsed from the delay time is used as a film-formation end
point, a film-formation end point in consideration of variation in
the shape of the openings 302a (that is, variation in the surface
area of the cavities 302) among the semiconductor substrates 2
cannot be obtained. When no consideration can be given to variation
in the shape of the openings 302a, the film-formation end point may
be too early for the semiconductor substrate 2 that requires a long
time for blocking the openings 302a while the film-formation end
point may be too late for the semiconductor substrate 2 that
requires a short time for blocking the openings 302a. In this case,
if different semiconductor substrates 2 use the same etching
condition for tungsten films on the sidewalls of trenches, the
tungsten films on the sidewalls of the trenches are excessively
thin in the semiconductor substrate 2 for which the film-formation
end point is too early and thus the tungsten films 321 in the
cavities 302 are also etched. If the tungsten films 321 in the
cavities 302 are etched, word lines cannot provide desired
electrical characteristics. In the semiconductor substrate 2 for
which the film-formation end point is too late, the tungsten films
on the sidewalls of the trenches are excessively thick and thus the
tungsten films on the sidewalls of the trenches cannot be
completely removed. If the tungsten films on the sidewalls of the
trenches are not completely removed, the upper and lower conductive
layers 32 mutually short-circuit.
[0061] On the other hand, according to the present embodiment, the
film-formation end point is detected by using as a reference (a
starting point) not a time point before the openings 302a are
blocked such as a film-formation delay time but the
opening-blocking time point as described later. When the
opening-blocking time point is used as a reference, an optimum
film-formation end point that enables etching of the tungsten films
on the sidewalls of the trenches in appropriate amounts under the
same etching condition can be detected regardless of variation in
the shape of the openings 302a among different semiconductor
substrates 2 (lots).
[0062] When the amount of byproducts has decreased (Step S5: Yes)
in the above determination (Step S5), the first detector 120
detects (determines) a current time point (clock time) as the
opening-blocking time point (Step S6).
[0063] FIGS. 8A and 8B are sectional views showing the
semiconductor manufacturing method after FIGS. 7A and 7B. FIG. 8A
shows the tungsten films 321 that have blocked the openings 302a
near the upper ends of the memory cells 4. FIG. 8B shows the
tungsten films 321 that have blocked the openings 302a near the
lower ends of the memory cells 4.
[0064] At the opening-blocking time point, the film thickness of
the tungsten films 321 on sidewalls 5a is relatively thin at
positions facing the openings 302a due to the recesses of the
cavities 302. To prevent excessive etching of the tungsten films
321 at the positions facing the openings 302a, it is preferable
that the film thickness of the tungsten films 321 on the sidewalls
5a be formed to be sufficiently thick by continuing the film
formation after the opening-blocking time point. As shown in FIGS.
8A and 8B, the openings 302a are already blocked at the
opening-blocking time point. For this reason, in forming the
tungsten films 321 after the opening-blocking time point, it is not
necessary to give consideration to variation in the required time
for blocking the openings 302a due to variation in the shape of the
openings 302a among different semiconductor substrates 2. After the
opening-blocking time point, the tungsten films 321 are formed on
the inner walls (the sidewalls 5a and bottom walls 5b) of the
trenches 5 and an upper wall 310a of the third stacked film 310.
The surface area of these portions 5a, 5b, and 310a is far smaller
than the surface area of the cavities 302. Therefore, even when the
shapes of the inner walls 5a and 5b of the trenches 5 and the upper
wall 310a of the third stacked film 310 vary among different
semiconductor substrates 2, such variation can be considered to
have little influence on the film thickness of the tungsten films
321. That is, after the opening-blocking time point, the
film-formation rates of the tungsten films 321 in different
semiconductor substrates 2 can be considered to be almost identical
with one another.
[0065] For the above reasons, in the present embodiment, also after
the opening-blocking time point, forming the tungsten films 321 is
continued while a time point at which a predetermined time has
elapsed from the opening-blocking time point is used as the
film-formation end point.
[0066] More specifically, the controller 140 determines whether a
predetermined time has elapsed from the opening-blocking time point
(Step S7). When the predetermined time has elapsed (Step S7: Yes),
the controller 140 executes control to stop supply of the material
gas (Step S8). When the predetermined time has not elapsed (Step
S7: No), the controller 140 repeats the determination (Step
S7).
[0067] In this manner, when a time point at which a predetermined
time has elapsed from the opening-blocking time point is used as
the film-formation end point, the film thicknesses of the tungsten
films 321 on the sidewalls of the trenches can be equalized among
different semiconductor substrates 2 (lots) under simple control of
end points.
[0068] If film formation is performed based on a film-formation end
point using a time point before the openings 302a are blocked such
as a film-formation delay time as a reference (a starting point),
film formation cannot be performed in consideration of increase in
the film-formation rate for the material gas of the same flow rate
after the openings 302a are blocked. When film formation in
consideration of increase in the film-formation rate cannot be
performed, the film formation is continued for a longer time even
after a sufficient film thickness of the tungsten films 321 is
formed on the sidewalls 5a. Consequently, the material gas is
wastefully consumed. On the other hand, in the present embodiment,
increase in the film-formation rate after the openings 302a are
blocked is allowed for and a time until the film-formation end
point can be set to be relatively short after the openings 302a are
blocked. Consequently, the amount of the material gas can be
reduced.
[0069] FIGS. 9A and 9B are sectional views showing the
semiconductor manufacturing method after FIGS. 8A and 8B. FIG. 9A
shows the separated conductive layers 32 near the upper ends of the
memory cells 4. FIG. 9B shows the separated conductive layers 32
near the lower ends of the memory cells 4.
[0070] As shown in FIGS. 8A and 8B, the tungsten films 321 are
formed not only inside the cavities 302 but also on the sidewalls
5a of the trenches 5 and the like. The tungsten films 321 on the
sidewalls 5a need to be removed to prevent the upper and lower
conductive layers 32 from short-circuiting.
[0071] Accordingly, as shown in FIGS. 9A and 9B, the tungsten films
321 on the sidewalls 5a are removed by etching to separate the
upper and lower conductive layers 32. At that time, the tungsten
film 321 on the upper end of the third stacked film 310 and the
tungsten films 321 on the bottoms of the trenches 5 are also
removed.
[0072] The respective film thicknesses of the tungsten films 321 on
the sidewalls 5a in different semiconductor substrates 2 are equal
because the tungsten films 321 are formed according to
film-formation end points using the opening-blocking time points as
references, respectively. Therefore, the tungsten films 321 on the
sidewalls 5a in the respective semiconductor substrates 2 can be
etched in appropriate amounts under the same etching condition.
[0073] As described above, according to the semiconductor
manufacturing apparatus 100 and the semiconductor manufacturing
method of the present embodiment, a film-formation end point using
an opening-blocking time point as a reference is used. Accordingly,
an etching condition for separating the upper and lower conductive
layers 32 can be uniformed among different semiconductor substrates
2, and consumption of material gas can be reduced. As a result,
manufacturing efficiency and economical efficiency in manufacturing
semiconductor devices can be improved.
[0074] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
methods and systems described herein may be embodied in a variety
of other forms; furthermore, various omissions, substitutions and
changes in the form of the methods and systems described herein may
be made without departing from the spirit of the inventions. The
accompanying claims and their equivalents are intended to cover
such forms or modifications as would fall within the scope and
spirit of the inventions.
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