U.S. patent application number 16/817814 was filed with the patent office on 2021-03-18 for semiconductor device, manufacturing method thereof, and semiconductor storage device.
This patent application is currently assigned to Kioxia Corporation. The applicant listed for this patent is Kioxia Corporation. Invention is credited to Masayuki KITAMURA.
Application Number | 20210083057 16/817814 |
Document ID | / |
Family ID | 1000004720485 |
Filed Date | 2021-03-18 |
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United States Patent
Application |
20210083057 |
Kind Code |
A1 |
KITAMURA; Masayuki |
March 18, 2021 |
SEMICONDUCTOR DEVICE, MANUFACTURING METHOD THEREOF, AND
SEMICONDUCTOR STORAGE DEVICE
Abstract
A semiconductor device according to an embodiment includes an
oxide film containing first element and a conductive film provided
to be in contact with the oxide film, containing metal element and
oxygen element, and having conductivity. A range of a volume
density of the oxygen element in the conductive film is different
between cases where the metal element are tungsten (W), molybdenum
(Mo), titanium (Ti), chromium (Cr), vanadium (V), iron (Fe), copper
(Cu), tantalum (Ta), or niobium (Nb).
Inventors: |
KITAMURA; Masayuki;
(Yokkaichi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kioxia Corporation |
Minato-ku |
|
JP |
|
|
Assignee: |
Kioxia Corporation
Minato-ku
JP
|
Family ID: |
1000004720485 |
Appl. No.: |
16/817814 |
Filed: |
March 13, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/02565 20130101;
H01L 29/24 20130101 |
International
Class: |
H01L 29/24 20060101
H01L029/24; H01L 21/02 20060101 H01L021/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 18, 2019 |
JP |
2019-169528 |
Claims
1. A semiconductor device comprising: an oxide film containing
first element; and a conductive film provided to be in contact with
the oxide film, containing metal element and oxygen element,
wherein a volume density of the oxygen element in the conductive
film is less than 2.38.times.10.sup.22 atoms/cm.sup.3 when the
metal element is tungsten (W), less than 4.27.times.10.sup.22
atoms/cm.sup.3 when the metal element is molybdenum (Mo), less than
2.28.times.10.sup.22 atoms/cm.sup.3 when the metal element is
titanium (Ti), less than 5.00.times.10.sup.22 atoms/cm.sup.3 when
the metal element is chromium (Cr), less than 4.23.times.10.sup.22
atoms/cm.sup.3 when the metal element is vanadium (V), less than
4.84.times.10.sup.22 atoms/cm.sup.3 when the metal element is iron
(Fe), less than 2.82.times.10.sup.22 atoms/cm.sup.3 when the metal
element is copper (Cu), less than 3.32.times.10.sup.22
atoms/cm.sup.3 when the metal element is tantalum (Ta), and less
than 2.78.times.10.sup.22 atoms/cm.sup.3 when the metal element
niobium (Nb).
2. The device of claim 1, wherein the volume density of the oxygen
element in the conductive film is 1.0.times.10.sup.16
atoms/cm.sup.3 or more.
3. The device of claim 1, wherein an atom of the metal element is
bounded with an atom of the oxygen element in the conductive film,
and said atom of the oxygen element is bounded with an atom of the
first element.
4. The device of claim 1, wherein a binding energy between the
metal element and an oxygen element is smaller than a binding
energy between an oxygen element and the first element.
5. The device of claim 1, further comprising a film on the
conductive film, which contains metal element of a same type as or
a different type from the metal element and has a lower oxygen
concentration than the conductive film.
6. A manufacturing method of a semiconductor device, comprising:
forming an oxide film containing first element on a semiconductor
substrate; and forming a conductive film on the oxide film by using
a material gas that contains metal element, a reducing gas that
reduces the metal element, and a carrier gas that introduces the
material gas into the substrate, wherein at least one of the
material gas, the reducing gas, and the carrier gas contains oxygen
element, and a temperature of the substrate in formation of the
conductive film is higher than a sublimation temperature of metal
oxide of the metal element.
7. The method of claim 6, wherein forming the conductive film
comprising: forming a first layer that is in contact with the oxide
film and contains the metal element and the oxygen element; and
forming a second layer after forming the first layer, the second
layer contains a metal element of a same type as or a different
type from the metal element, and has a lower oxygen concentration
than the first layer.
8. The method of claim 6, wherein the metal element is tungsten
(W), titanium (Ti), molybdenum (Mo), chromium (Cr), vanadium (V),
iron (Fe), copper (Cu), tantalum (Ta), or niobium (Nb).
9. The method of claim 6, wherein the material gas contains a
tungsten compound, the reducing gas contains hydrogen gas
(H.sub.2), nitrogen dioxide gas (NO.sub.2), nitrous oxide gas
(N.sub.2O), carbon monoxide gas (CO), oxygen gas (O.sub.2), or
ozone gas (O.sub.3), and the carrier gas contains argon gas (Ar),
nitrogen gas (N.sub.2), or carbon dioxide gas (CO.sub.2).
10. A semiconductor storage device comprising: a plurality of
conductive films stacked apart from each other in a first
direction; a plurality of oxide films that are in contact with the
conductive films in the first direction and are stacked via the
conductive films; a semiconductor layer penetrating through the
conductive films and the oxide films in the first direction; and a
charge storage layer arranged between the semiconductor layer and
the conductive films in a second direction crossing the first
direction, wherein the oxide films contain first element, the
conductive films contain metal element and oxygen element, and a
volume density of the oxygen element in the conductive film is less
than 2.38.times.10.sup.22 atoms/cm.sup.3 when the metal element is
tungsten, less than 4.27.times.10.sup.22 atoms/cm.sup.3 when the
metal element is molybdenum, less than 2.28.times.10.sup.22
atoms/cm.sup.3 when the metal element is titanium, less than
5.00.times.10.sup.22 atoms/cm.sup.3 when the metal element is
chromium, less than 4.23.times.10.sup.22 atoms/cm.sup.3 when the
metal element is vanadium, less than 4.84.times.10.sup.22
atoms/cm.sup.3 when the metal element is iron, less than
2.82.times.10.sup.22 atoms/cm.sup.3 when the metal element is
copper, less than 3.32.times.10.sup.22 atoms/cm.sup.3 when the
metal element is tantalum, and less than 2.78.times.10.sup.22
atoms/cm.sup.3 when the metal element is niobium.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2019-169528, filed on
Sep. 18, 2019; the entire contents of which are incorporated herein
by reference.
FIELD
[0002] Embodiments of the present invention relate to a
semiconductor device, a manufacturing method thereof, and a
semiconductor storage device.
BACKGROUND
[0003] When a metal film is formed directly on an oxide film, there
is a possibility that the metal film peels off because adhesion
between the metal film and the oxide film is weak. Therefore, there
is known a technique of forming a metal nitride film between the
oxide film and the metal film. However, the resistivity of metal
nitride is higher than that of metal, and therefore a conductive
film including a metal nitride film and a metal film as a whole has
a high resistance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a cross-sectional view illustrating a structure of
relevant parts of a semiconductor device according to a first
embodiment;
[0005] FIG. 2 is an explanatory diagram of a manufacturing method
of the semiconductor device according to the first embodiment;
[0006] FIG. 3A is a diagram schematically illustrating a state of
an interface between an oxide film and a conductive film;
[0007] FIG. 3B is a diagram schematically illustrating a state of
the interface between an oxide film and a conductive film;
[0008] FIG. 4 is an example of a phase diagram of tungsten element
and oxygen element;
[0009] FIG. 5 is a cross-sectional view illustrating a structure of
relevant parts of a semiconductor device according to a second
embodiment; and
[0010] FIG. 6 is a cross-sectional view illustrating a structure of
relevant parts of a semiconductor device according to a third
embodiment.
DETAILED DESCRIPTION
[0011] Embodiments will now be explained with reference to the
accompanying drawings. The present invention is not limited to the
embodiments.
[0012] A semiconductor device according to an embodiment comprises:
an oxide film containing first element; and a conductive film
provided to be in contact with the oxide film, containing metal
element and oxygen atoms, and having conductivity. A volume density
of the oxygen element in the conductive film is less than
2.38.times.10.sup.22 atoms/cm.sup.3 when the metal element is
tungsten (W), less than 4.27.times.10.sup.22 atoms/cm.sup.3 when
the metal element is molybdenum (Mo), less than
2.28.times.10.sup.22 atoms/cm.sup.3 when the metal element is
titanium (Ti), less than 5.00.times.10.sup.22 atoms/cm.sup.3 when
the metal element is chromium (Cr), less than 4.23.times.10.sup.22
atoms/cm.sup.3 when the metal element is vanadium (V), less than
4.84.times.10.sup.22 atoms/cm.sup.3 when the metal element is iron
(Fe), less than 2.82.times.10.sup.22 atoms/cm.sup.3 when the metal
element is copper (Cu), less than 3.32.times.10.sup.22
atoms/cm.sup.3 when the metal element is tantalum (Ta), and less
than 2.78.times.10.sup.22 atoms/cm.sup.3 when the metal element is
niobium (Nb).
First Embodiment
[0013] FIG. 1 is a cross-sectional view illustrating a structure of
relevant parts of a semiconductor device according to a first
embodiment. The semiconductor device 1 according to the present
embodiment includes a substrate 10, an oxide film 20, and a
conductive film 30.
[0014] The substrate 10 is a silicon substrate, for example. The
oxide film 20 is formed on the substrate 10. The oxide film 20
contains silicon oxide (SiO.sub.2) or aluminum oxide
(Al.sub.2O.sub.3), for example. The conductive film 30 is formed on
the oxide film 20.
[0015] The conductive film 30 contains metal element and oxygen
element. The metal element is, for example, tungsten (W), titanium
(Ti), molybdenum (Mo), chromium (Cr), vanadium (V), iron (Fe),
copper (Cu), tantalum (Ta), or niobium (Nb). The conductive film 30
has conductivity and has an electrical resistivity (a resistivity)
of 1.0.times.10.sup.6 .mu..OMEGA./cm or less, for example.
[0016] A manufacturing method of the semiconductor device 1
according to the present embodiment is described below.
Manufacturing steps of the conductive film 30 are described
here.
[0017] First, as illustrated in FIG. 2, the substrate 10 is
accommodated in a chamber 101 while being fixed on a stage 100. At
this time, the oxide film 20 has already been formed on the
substrate 10. The oxide film 20 is a silicon oxide film in the
present embodiment.
[0018] Subsequently, the conductive film 30 is formed on the oxide
film 20 by CVD (Chemical Vapor Deposition). Specifically, a
material gas 201 containing metal element and oxygen element and a
reducing gas 202 that reduces the metal element contained in the
material gas 201 are alternately introduced into the chamber 101.
At this time, a carrier gas 203 is introduced between the material
gas 201 and the reducing gas 202. A gas remaining in the chamber
101 is discharged by the carrier gas 203.
[0019] In the present embodiment, the material gas 201 is a gas
containing tungsten dichloride dioxide (WO.sub.2Cl.sub.2). The
reducing gas 202 is hydrogen (H.sub.2) gas. The carrier gas 203 is
argon (Ar) gas.
[0020] FIGS. 3A and 3B are diagrams schematically illustrating
states of atoms at an interface between the oxide film 20 and the
conductive film 30. When the material gas 201, the reducing gas
202, and the carrier gas 203 described above are introduced into
the chamber 101, the conductive film 30 containing tungsten element
and oxygen element is formed on the oxide film 20 to be in contact
therewith, as illustrated in FIG. 3A.
[0021] In general, oxygen atoms have a property of being easily
bonded with silicon atoms. Therefore, as illustrated in FIG. 3B,
oxygen atoms contained in the conductive film 30 are bonded with
silicon atoms contained in the oxide film 20 at the interface
between the conductive film 30 and the oxide film 20. In other
words, metal atoms contained in the conductive film 30 are bonded
with the silicon atoms in the oxide film 20 via the oxygen atoms.
That is, an atom of the metal element is bounded with an atom of
the oxygen element in the conductive film 30, and said atom of the
oxygen element is bounded with an atom of the silicon element.
[0022] Therefore, according to the present embodiment, it is
possible to increase adhesion between the conductive film 30 and
the oxide film 20 without forming a high-resistance metal nitride
film between the conductive film 30 and the oxide film 20.
[0023] Further, a binding energy between a metal atom (a tungsten
atom) and an oxygen atom is smaller than a binding energy between a
silicon atom and an oxygen atom. Therefore, in the present
embodiment, the oxygen atoms contained in the conductive film 30
are to be bonded with the silicon atoms contained in the oxide film
20, rather than the metal atoms, at the interface between the
conductive film 30 and the oxide film 20. Accordingly, it is
possible to further increase the adhesion between the conductive
film 30 and the oxide film 20. Meanwhile, in the present
embodiment, when the oxygen concentration in the conductive film 30
is high, metal oxide is easily generated in the conductive film 30,
which causes increase in the resistivity of the conductive film
30.
[0024] FIG. 4 is an example of a phase diagram of tungsten element
and oxygen element. According to the phase diagram illustrated in
FIG. 4, tungsten oxide having the lowest oxygen atom ratio is
pentatungsten trioxide (W.sub.5O.sub.3). An oxide concentration in
this pentatungsten trioxide is about 37.5 atom %. When the oxide
concentration in the conductive film 30 exceeds 37.5 atom %,
tungsten oxide is generated, causing increase in the resistivity of
the conductive film 30.
[0025] Because the number of atoms per unit volume of tungsten is
about 6.3.times.10.sup.22 atoms/cm.sup.3, the volume density of
oxygen element corresponding to 37.5% of the number of atoms
described above is about 2.38.times.10.sup.22 atoms/cm.sup.3.
Therefore, in order to ensure high adhesion between the oxide film
20 and the conductive film 30, suppress increase in the resistivity
of the conductive film 30, and cause the conductive film 30 to have
conductivity, it is desirable that the volume density of oxygen
element in the conductive film 30 is less than 2.38.times.10.sup.22
atoms/cm.sup.3.
[0026] Further, also for metal other than tungsten, an upper limit
of the volume density of oxygen element for causing the conductive
film 30 to have the conductivity can be obtained by using a phase
diagram or the like, as represented in the following Table 1.
TABLE-US-00001 TABLE 1 Oxide having Metal lowest oxygen Upper limit
of volume density of element ratio oxygen element (atoms/cm.sup.3)
Ti Ti.sub.3O.sub.2 2.28 .times. 10.sup.22 Mo MoO.sub.2 4.27 .times.
10.sup.22 Cr Cr.sub.2O.sub.3 5.00 .times. 10.sup.22 V
V.sub.2O.sub.3 4.23 .times. 10.sup.22 Fe Fe.sub.3O.sub.4 4.84
.times. 10.sup.22 Cu Cu.sub.2O 2.82 .times. 10.sup.22 Ta
Ta.sub.2O.sub.3 3.32 .times. 10.sup.22 Nb NbO 2.78 .times.
10.sup.22
[0027] Meanwhile, it is desirable that the conductive film 30 has a
volume density of a certain number or more from a viewpoint of
adhesion. For example, the adhesion with an oxide film can be
further increased when the volume density of oxygen element in the
conductive film 30 is 1.0.times.10.sup.16 atoms/cm.sup.3 or
more.
[0028] Further, when the conductive film 30 is formed, it is
desirable to set the temperature of the substrate 10 (a film
forming temperature) to be higher than a sublimation temperature of
metal oxide in which metal element contained in the conductive film
30 and oxygen element are bonded together, in order to suppress
generation of the metal oxide. For example, when the temperature of
the substrate 10 is higher than 750.degree. C., it is possible to
sublimate tungsten oxide. As a result, generation of the tungsten
oxide in the conductive film 30 can be suppressed. Further, in a
case where the metal element contained in the conductive film 30 is
molybdenum, molybdenum oxide is sublimated at 400.degree. C. to
600.degree. C. Therefore, generation of the molybdenum oxide can be
suppressed by setting the temperature of the substrate 10 to be
higher than 400.degree. C.
[0029] The following Table 2 represents stable oxides of the metal
element described above and sublimation temperatures of those
oxides. In film formation of atoms of each metal element, it is
desirable to set the temperature of the substrate 10 (the film
forming temperature) to be higher than the sublimation temperature
described in Table 2. Such setting enables the metal oxide to be
sublimated.
TABLE-US-00002 TABLE 2 Example of Metal most stable element oxide
Sublimation temperature (.degree. C.) Ti TiO.sub.2 935 Mo MoO.sub.2
397.5 Cr Cr.sub.2O.sub.3 1217.5 V V.sub.2O.sub.5 345 Fe
Fe.sub.3O.sub.4 798.5 Cu Cu.sub.2O 617.5 Ta Ta.sub.2O.sub.5 734 Nb
Nb.sub.2O.sub.5 760 W WO.sub.3 736.5
[0030] Although the material gas 201 contains oxygen element in the
present embodiment, a film forming method of the conductive film 30
is not limited thereto. It suffices that the conductive film 30 is
formed by using a combination of the material gas 201, the reducing
gas 202, and the carrier gas 203 at least one of which contains
oxygen element.
[0031] For example, when a combination of the material gas 201
containing a tungsten compound (W(CO).sub.6, WF.sub.6, WCl.sub.6,
WCl.sub.5, WO.sub.2Cl.sub.2, WOCl.sub.4, or W(CO).sub.6), the
reducing gas 202 containing hydrogen gas (H.sub.2), nitrogen
dioxide gas (NO.sub.2), nitrous oxide gas (N.sub.2O), carbon
monoxide gas (CO), oxygen gas (O.sub.2), or ozone gas (O.sub.3),
and the carrier gas 203 containing argon gas (Ar), nitrogen gas
(N.sub.2), or carbon dioxide gas (CO.sub.2), at least one of which
contains oxygen, is used, tungsten element and oxygen element are
contained in the conductive film 30. Therefore, the adhesion
between the conductive film 30 and the oxide film 20 is increased.
Although tungsten has been referred to as an example here, the
present embodiment can be achieved by another metal element
similarly. For example, a gas containing a molybdenum compound
(MoO.sub.2Cl.sub.2, MoOCl.sub.4, Mo(CO).sub.6), a titanium compound
(Ti[OCH(CH.sub.3).sub.2].sub.4), a tantalum compound
(Ta(OC.sub.2H.sub.5).sub.5), or a niobium compound
(Nb(OC.sub.2H.sub.5).sub.5) can be used as the material gas.
Second Embodiment
[0032] FIG. 5 is a cross-sectional view illustrating a structure of
relevant parts of a semiconductor device according to a second
embodiment. Constituent elements identical to those of the
semiconductor device 1 according to the first embodiment described
above are denoted by like reference signs, and detailed
explanations thereof are omitted.
[0033] As illustrated in FIG. 5, a semiconductor device 2 according
to the present embodiment is different from that of the first
embodiment in the structure of the conductive film 30. While the
conductive film 30 according to the first embodiment has a
single-layer structure, the conductive film 30 according to the
present embodiment has a double-layer structure including a first
layer 31 and a second layer 32.
[0034] The first layer 31 is in contact with the oxide film 20 and
contains metal element and oxygen element. The first layer 31 is
formed by identical manufacturing steps to those of the conductive
film 30 according to the first embodiment described above. For
example, when CVD is performed by using the material gas 201
containing tungsten dichloride dioxide, the reducing gas 202
containing hydrogen element, and the carrier gas 203 containing
argon element, the first layer 31 containing tungsten element and
oxygen element can be formed on the oxide film 20. At this time, if
the first layer 31 is formed thick, its resistance becomes high.
Therefore, it is desirable that the thickness of the first layer 31
is 10 nm or less.
[0035] The second layer 32 is formed on the first layer 31. The
second layer 32 is formed by using the material gas 201 that is
different from that for the first layer 31. For example, when CVD
is performed by using the material gas 201 containing tungsten
hexafluoride (WF.sub.6), the reducing gas 202 containing hydrogen
element, and the carrier gas 203 containing argon element, the
second layer 32 containing tungsten element can be formed on the
first layer 31. The second layer 32 has a lower resistance than the
first layer 31, because the second layer 32 does not contain oxygen
element. In order to reduce the resistance of the conductive film
30 as a whole, it is desirable that the second layer 32 is thicker
than the first layer 31.
[0036] According to the present embodiment, it is possible to
increase adhesion between the oxide film 20 and the conductive film
30 by forming the first layer 31 containing oxygen element on the
oxide layer 20. Further, the resistance of the conductive film 30
can be reduced by forming the second layer 32 containing less
impurities on the first layer 31. Accordingly, it is possible to
achieve the conductive film 30 in which the adhesion and the low
resistance are balanced.
[0037] Although metal element contained in the first layer 31 is
the same type as metal element contained in the second layer 32 in
the present embodiment, the metal element contained in the
respective layers may be of different types from each other. For
example, a structure may be employed in which molybdenum element is
used for the first layer 31 and tungsten element is used for the
second layer 32. Also in this case, the adhesion and the low
resistance can be balanced. Further, although the second layer 32
has been described as a layer not containing oxygen element, the
second layer 32 that is formed to have a lower oxygen concentration
than the first layer 31 can also have identical effects to those in
a case where the second layer 32 does not contain oxygen
element.
Third Embodiment
[0038] FIG. 6 is a cross-sectional view illustrating a structure of
relevant parts of a semiconductor device according to a third
embodiment. A semiconductor device 3 illustrated in FIG. 6 is a
three-dimensional semiconductor memory in which word lines are
stacked. In the semiconductor device 3, the oxide films 20 and the
conductive films 30 are alternately stacked on the substrate 10.
Each conductive film 30 functions as a word line.
[0039] When each conductive film 30 of the third embodiment is
formed, first, the oxide films 20 and sacrificial films are
alternately stacked on the substrate 10. The sacrificial film is a
silicon nitride (SiN) film, for example. The sacrificial film is
removed by a chemical containing phosphoric acid, for example,
after formation of a memory element film 40 described later. By
removal of the sacrificial film, a cavity is formed between the
oxide films 20. In this cavity, each conductive film 30 is formed
in the manner described in the above first or second
embodiment.
[0040] The memory element film 40 is formed in a hole that
penetrates through a stack of the oxide films 20 and the above
sacrificial films. A charge blocking film 41 is formed in an outer
peripheral portion of this hole. A charge storage film 42 is formed
inside the charge blocking film 41. A tunnel insulation film 43 is
formed inside the charge storage film 42. A channel film 44 is
formed inside the tunnel insulation film 43. A core film 45 is
formed inside the channel film 44.
[0041] Each of the charge blocking film 41, the tunnel insulation
film 43, and the core film 45 is a silicon oxide film, for example.
The charge storage film 42 is a silicon nitride (SiN) film, for
example. The channel film 44 is a polysilicon film, for
example.
[0042] In the present embodiment, the conductive film 30 is formed
in the manner described in the above first or second embodiment,
and therefore contains oxygen element. Adhesion between the oxide
film 20 and the conductive film 30 is improved because of this
oxygen element. Therefore, metal nitride having a high resistance
is not required. Accordingly, it is possible to reduce the
resistance of the conductive film 30 while increasing the adhesion
between the oxide film 20 and the conductive film 30.
[0043] 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
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments 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.
* * * * *