U.S. patent application number 15/074338 was filed with the patent office on 2017-09-07 for semiconductor device and method of manufacturing the same.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. The applicant listed for this patent is KABUSHIKI KAISHA TOSHIBA. Invention is credited to Natsuki FUKUDA, Masanori KOMURA, Atsushi OGA, Mutsumi OKAJIMA, Takeshi TAKAGI, Toshiharu TANAKA, Takeshi YAMAGUCHI.
Application Number | 20170256588 15/074338 |
Document ID | / |
Family ID | 59722889 |
Filed Date | 2017-09-07 |
United States Patent
Application |
20170256588 |
Kind Code |
A1 |
FUKUDA; Natsuki ; et
al. |
September 7, 2017 |
SEMICONDUCTOR DEVICE AND METHOD OF MANUFACTURING THE SAME
Abstract
A semiconductor device according to an embodiment includes: a
stacked body including a plurality of first conductive films
stacked via an inter-layer insulating film; a first conductive body
facing the stacked body to extend in a stacking direction; and a
plurality of first insulating films in the same layers as the first
conductive films and disposed between the first conductive body and
the first conductive films, the first conductive body including a
projecting part that projects along tops of one of the first
insulating films and one of the first conductive films, and a lower
surface of the projecting part contacting an upper surface of the
one of the first conductive films.
Inventors: |
FUKUDA; Natsuki; (Yokkaichi,
JP) ; OKAJIMA; Mutsumi; (Yokkaichi, JP) ; OGA;
Atsushi; (Yokkaichi, JP) ; TANAKA; Toshiharu;
(Yokkaichi, JP) ; YAMAGUCHI; Takeshi; (Yokkaichi,
JP) ; TAKAGI; Takeshi; (Yokkaichi, JP) ;
KOMURA; Masanori; (Kuwana, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA TOSHIBA |
Tokyo |
|
JP |
|
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
Tokyo
JP
|
Family ID: |
59722889 |
Appl. No.: |
15/074338 |
Filed: |
March 18, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62301903 |
Mar 1, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 27/11582 20130101;
H01L 27/2481 20130101; H01L 27/249 20130101; H01L 23/5329 20130101;
H01L 27/1157 20130101; H01L 27/11575 20130101; H01L 27/2454
20130101; H01L 21/76805 20130101; H01L 27/11573 20130101; H01L
27/11551 20130101; H01L 27/101 20130101; H01L 21/76831 20130101;
H01L 21/76816 20130101; H01L 23/5226 20130101; H01L 21/8221
20130101; H01L 21/3213 20130101; H01L 21/311 20130101; H01L
27/11556 20130101; H01L 27/11578 20130101; H01L 27/0688 20130101;
H01L 29/7926 20130101 |
International
Class: |
H01L 27/24 20060101
H01L027/24; H01L 21/3213 20060101 H01L021/3213; H01L 21/311
20060101 H01L021/311; H01L 21/768 20060101 H01L021/768 |
Claims
1. A semiconductor device, comprising: a stacked body including a
plurality of first conductive films stacked via an inter-layer
insulating film; a first conductive body facing the stacked body to
extend in a stacking direction; a plurality of first insulating
films in the same layers as the first conductive films and disposed
between the first conductive body and the first conductive films,
the first conductive body including a projecting part that projects
along tops of one of the first insulating films and one of the
first conductive films, and a lower surface of the projecting part
contacting an upper surface of the one of the first conductive
films; and a second insulating film configured from a material
different from that of the first insulating film, disposed on the
one of the first conductive films of the stacked body, and disposed
in the same layer as the projecting part of the first conductive
body.
2. The semiconductor device according to claim 1, further
comprising: a third insulating film configured from the same
material as the first insulating film, and disposed in a more upper
layer than the second insulating film and the projecting part.
3. The semiconductor device according to claim 1, further
comprising: a second conductive film extending in the stacking
direction; and a plurality of memory cells disposed at
intersections of the first conductive films and the second
conductive film.
4. The semiconductor device according to claim 1, wherein the first
conductive body contacts the first conductive film disposed in an
uppermost layer at a certain position when viewed from the stacking
direction.
5. The semiconductor device according to claim 1, further
comprising a second conductive body disposed between a
semiconductor substrate and the first conductive films in the
stacking direction, wherein the first conductive body contacts an
upper surface of the second conductive body at a bottom surface of
the first conductive body.
6. The semiconductor device according to claim 1, further
comprising a plurality of the first conductive bodies, wherein a
certain first conductive body and another first conductive body
contact a different first conductive film.
7. The semiconductor device according to claim 6, wherein the first
conductive films are formed in a stepped shape in which an end of
each first conductive film configures one step, and the first
conductive bodies contact the ends of the first conductive films
formed in the stepped shape.
8. The semiconductor device according to claim 6, wherein the first
conductive bodies have a bottom surface in the same position in the
stacking direction.
9. The semiconductor device according to claim 1, wherein the first
conductive body has the projecting part on both side surfaces
facing in a direction intersecting the stacking direction.
10. The semiconductor device according to claim 1, wherein the
first conductive body has the projecting part only on one of side
surfaces facing in a direction intersecting the stacking
direction.
11. The semiconductor device according to claim 1, wherein the
projecting part of the first conductive body contacts an upper
surface of one of the first insulating films at a side surface
facing in the stacking direction of the projecting part.
12. A method of manufacturing a semiconductor device, comprising:
forming a stacked body including a stacked plurality of first
conductive films; depositing a first insulating film on one of the
first conductive films; forming a hole that extends in a stacking
direction at least from an upper surface of the first insulating
film to a bottom surface of a certain first conductive film;
removing ends of the first conductive films exposed in a side
surface of the hole; implanting a plurality of second insulating
films configured from a material different from that of the first
insulating film, in places of the removed ends of the first
conductive films; removing an end of the first insulating film
exposed in the side surface of the hole until an upper surface of
the first conductive film is exposed; and implanting a first
conductive body in the hole.
13. The method of manufacturing a semiconductor device according to
claim 12, further comprising when removing the end of the first
insulating film, selectively removing the first insulating film, of
the first insulating film and the second insulating films.
14. The method of manufacturing a semiconductor device according to
claim 12, further comprising: before forming the stacked body,
depositing a second conductive body between a semiconductor
substrate and a position of forming the stacked body in the
stacking direction; and when forming the hole, continuing to dig
out the stacked body until an upper surface of the second
conductive body is exposed in a bottom part of the hole.
15. The method of manufacturing a semiconductor device according to
claim 14, further comprising after deposition of the second
conductive body and before formation of the stacked body,
depositing an etching stop film on the second conductive body.
16. The method of manufacturing a semiconductor device according to
claim 12, further comprising after formation of the stacked body
and before deposition of the first insulating film, forming, with
respect to a certain first conductive film, a first portion
projected from an arrangement region of a first conductive film in
a layer above this certain first conductive film, when viewing from
the stacking direction.
17. The method of manufacturing a semiconductor device according to
claim 16, further comprising when forming the hole, forming the
hole at a position where the first portion is exposed from both
side surfaces facing in a direction intersecting the stacking
direction of the hole.
18. The method of manufacturing a semiconductor device according to
claim 16, further comprising when forming the hole, forming the
hole at a position where the first portion is exposed from one of
side surfaces facing in a direction intersecting the stacking
direction of the hole.
19. The method of manufacturing a semiconductor device according to
claim 16, further comprising when depositing the first insulating
film, depositing the first insulating film so as to contact the
first portion of the first conductive films.
20. The method of manufacturing a semiconductor device according to
claim 16, further comprising when forming the hole, simultaneously
forming a plurality of the holes having the same depth in the
stacking direction.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior U.S. Provisional Application 62/301,903,
filed on Mar. 1, 2016, the entire contents of which are
incorporated herein by reference.
BACKGROUND
[0002] Field
[0003] Embodiments of the present invention relate to a
semiconductor device and a method of manufacturing the same.
[0004] Description of the Related Art
[0005] A flash memory is a semiconductor device known for its low
cost and large capacity. One example of a semiconductor device to
replace the flash memory is a variable resistance type memory
(ReRAM: Resistance RAM) which employs a variable resistance film in
its memory cell. The ReRAM can configure a cross-point type memory
cell array, hence can achieve an increased capacity similarly to
the flash memory. Moreover, in order to further increase capacity,
there is also being developed a ReRAM having a so-called VBL
(Vertical Bit Line) structure in which bit lines which are
selection wiring lines are arranged in a perpendicular direction to
a semiconductor substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a view showing functional blocks of a
semiconductor device according to a first embodiment.
[0007] FIG. 2 is a circuit diagram of a memory cell array of the
semiconductor device according to the same embodiment.
[0008] FIG. 3 is a schematic perspective view of the memory cell
array of the semiconductor device according to the same
embodiment.
[0009] FIG. 4 is a perspective view showing a schematic structure
of a contact region of the memory cell array of the semiconductor
device according to the same embodiment.
[0010] FIG. 5 is a cross-sectional view of the contact region of
the memory cell array of the semiconductor device according to the
same embodiment.
[0011] FIGS. 6 to 13 are cross-sectional views describing
manufacturing steps of the contact region of the memory cell array
of the semiconductor device according to the same embodiment.
[0012] FIG. 14 is a cross-sectional view of a contact region of a
memory cell array of a semiconductor device according to a second
embodiment.
[0013] FIGS. 15 to 18 are cross-sectional views describing
manufacturing steps of the contact region of the memory cell array
of the semiconductor device according to the same embodiment.
DETAILED DESCRIPTION
[0014] A semiconductor device according to an embodiment including:
a stacked body including a plurality of first conductive films
stacked via an inter-layer insulating film; a first conductive body
facing the stacked body to extend in a stacking direction; and a
plurality of first insulating films in the same layers as the first
conductive films and disposed between the first conductive body and
the first conductive films, the first conductive body including a
projecting part that projects along tops of one of the first
insulating films and one of the first conductive films, and a lower
surface of the projecting part contacting an upper surface of the
one of the first conductive films.
[0015] Semiconductor devices and methods of manufacturing the same
according to embodiments will be described below with reference to
the drawings.
First Embodiment
[0016] First, an overall configuration of a semiconductor device
according to a first embodiment will be described. Note that
hereafter, a semiconductor device of three-dimensional structure
employing a memory cell including a variable resistance element
will be described as an example. However, all of the embodiments
described hereafter may be applied also to another semiconductor
device having a three-dimensional structure, including the case
where a memory cell including a charge accumulation film is
employed, and so on.
[0017] FIG. 1 is a view showing functional blocks of the
semiconductor device according to the present embodiment.
[0018] As shown in, FIG. 1, the semiconductor device of the present
embodiment comprises: a memory cell array 1; a row decoder 2; a
column decoder 3; a higher block 4; a power supply 5; and a control
circuit 6.
[0019] The memory cell array 1 includes: a plurality of word lines
WL (conductive films) and a plurality of bit lines BL (conductive
films) that intersect each other; and a plurality of memory cells
MC disposed at intersections of these word lines WL and bit lines
BL. The row decoder 2 selects the word line WL during an access
operation. The column decoder 3 selects the bit line BL during an
access operation, and includes a driver that controls the access
operation. The higher block 4 selects the memory cell MC which is
to be an access target in the memory cell array 1. The higher block
4 provides a row address and a column address to, respectively, the
row decoder 2 and the column decoder 3. The power supply 5, during
write/read of data, generates certain combinations of voltages
corresponding to respective operations, and supplies these
combinations of voltages to the row decoder 2 and the column
decoder 3. The control circuit 6 performs control of the likes of
sending the addresses to the higher block 4, and, moreover,
performs control of the power supply 5, based on a command from
external.
[0020] Hereafter, the memory cell array 1 will be described.
[0021] FIG. 2 is a circuit diagram of the memory cell array of the
semiconductor device according to the present embodiment; and FIG.
3 is a schematic perspective view of the memory cell array of the
same semiconductor device.
[0022] As shown in FIG. 2, the memory cell array 1 includes a
select transistor STR, a global bit line GBL, and a select gate
line SG, in addition to the previously mentioned word line WL, bit
line BL, and memory cell MC.
[0023] As shown in FIG. 3, the memory cell array 1 has a so-called
VBL (Vertical Bit Line) structure in which the bit line BL extends
perpendicularly to a principal plane of a semiconductor substrate
SS. In other words, the word lines WL are arranged in a matrix in a
Y direction and a Z direction (stacking direction), and extend in
an X direction. The bit lines BL are arranged in a matrix in the X
direction and the Y direction, and extend in the Z direction.
Moreover, the memory cell MC is disposed at an intersection of the
word line WL and the bit line BL. Due to the above, the memory
cells MC are arranged in a three-dimensional matrix in the X
direction, the Y direction, and the Z direction.
[0024] As shown in FIG. 2, the memory cell MC includes a variable
resistance element VR. The variable resistance element VR undergoes
transition between a high-resistance state and a low-resistance
state, based on an applied voltage. The memory cell MC stores data
in a nonvolatile manner by a resistance state of this variable
resistance element VR. The variable resistance element VR generally
has: a setting operation where it undergoes transition from the
high-resistance state (reset state) to the low-resistance state
(set state); and a resetting operation where it undergoes
transition from the low-resistance state (set state) to the
high-resistance state (reset state). In addition, the variable
resistance element VR has a forming operation required only
immediately after manufacturing. This forming operation is an
operation in which a region (filament path) where locally it is
easy for a current to flow is formed in the variable resistance
element VR. The forming operation is executed by applying to both
ends of the variable resistance element VR a voltage which is
higher than an applied voltage employed during the setting
operation and the resetting operation.
[0025] The select transistor STR is disposed between the global bit
line GBL and a lower end of the bit line BL. As shown in FIG. 3,
the global bit lines GBL are arranged in the X direction, and
extend in the Y direction. Each of the global bit lines GEL is
commonly connected to one ends of a plurality of the select
transistors STR arranged in the Y direction.
[0026] The select transistor STR is controlled by the select gate
line SG functioning as a gate. The select gate lines SG are
arranged in the Y direction, and extend in the X direction. A
plurality of the select transistors STR arranged in the X direction
are collectively controlled by one select gate line SG functioning
as gates of these select transistors STR. On the other hand, in the
case of FIG. 3, a plurality of the select transistors STR arranged
in the Y direction are independently controlled by separately
provided select gate lines SG.
[0027] Next, a connection structure of the memory cell array 1 and
a peripheral circuit on the semiconductor substrate will be
described exemplifying a connection structure of the word line WL
and the peripheral circuit. Hereafter, a region where a connection
wiring line with the peripheral circuit is disposed, of the memory
cell array 1 will be called a "contact region 1b". Note that
hereafter, description is made using an example where the memory
cell array 1 has word lines WL<0> to WL<3>, but the
embodiments described hereafter are not limited to this.
[0028] FIG. 4 is a perspective view showing a schematic structure
of the contact region of the memory cell array of the semiconductor
device according to the present embodiment.
[0029] As shown in FIG. 4, each of the word lines WL<i> (i=0
to 3) connected to the memory cell MC is electrically connected to
the peripheral circuit (not illustrated) disposed on the
semiconductor substrate, via two vias Z1<i> (conductive body)
and Z0<i> (conductive film). Each of the word lines
WL<i> has a contact portion WLb<i> for contacting with
the via Z1<i>, in the contact region 1b. Each of the vias
Z1<i> is formed so as to extend in the Z direction and
penetrate the contact portion WLb<i>. Formed in each of the
vias Z1<i>, on at least both side surfaces facing in the X
direction, is a projecting part Z1b<i> that projects. The via
Z1<i> contacts the word line WL<i> by a bottom surface
which is one of side surfaces of this projecting part Z1b<i>
contacting an upper surface of the contact portion WLb<i>. On
the other hand, each of the vias Z0<i> is disposed between
the semiconductor substrate and the lowermost layer word line
WL<0>, and is electrically connected to the peripheral
circuit at a bottom surface of the via Z0<i>. Moreover, the
word line WL<i> and the peripheral circuit are electrically
connected by a bottom surface of the via Z1<i> and an upper
surface of the via Z0<i> being in contact.
[0030] Now, each of the word lines WL<i> is stacked in the Z
direction, hence when disposing the via Z1<i>, care must be
taken about interference between the via Z1<i> and the word
line WL<j> (j=0 to 3, excluding i) other than the word line
WL<i>.
[0031] In this respect, in the present embodiment, the contact
portion WLb<i> of the word line WL<i> is formed at a
position projected from an arrangement region of the word line
WL<u> (u=i to 3) in a higher layer than the word line
WL<i>. In the case of the example of FIG. 4, ends of the word
lines WL stacked in the Z direction are formed in a stepped shape,
and a portion corresponding to a step of the stepped shape
functions as the contact portion WLb. As a result, interference
between the via Z1<i> and the higher layer word line
WL<u> can be avoided.
[0032] However, interference between the via Z1<i> and the
word line WL<l> (l=0 to i-1) cannot be avoided by this
alone.
[0033] Therefore, in the present embodiment, the connection
structure of the word line WL and the peripheral circuit is further
configured as follows.
[0034] FIG. 5 is a cross-sectional view of the contact region of
the memory cell array of the semiconductor device according to the
present embodiment. FIG. 5 is a cross-sectional view of ranges a101
to a104 indicated by the dot-chain lines and broken lines shown in
FIG. 4.
[0035] The memory cell array 1 includes: the via Z0; an inter-layer
insulating film 102 that insulates between the vias Z0 adjacent in
the X direction; an etching stop film 103 disposed on the via Z0
and the inter-layer insulating film 102; an inter-layer insulating
film 104 and the word line WL disposed alternately on the etching
stop film 103; an inter-layer insulating film 106 disposed on the
uppermost layer word line WL<i> (i=0 to 3) in each of places
(positions indicated by the ranges a101 to a104) viewed from the Z
direction; and an inter-layer insulating film 107 disposed on the
inter-layer insulating film 106. Now, the via Z0 is formed from
titanium nitride (TiN), for example. The inter-layer insulating
films 102, 104, and 107 are formed from silicon oxide (SiO.sub.2),
for example. The etching stop film 103 is formed from a metal
oxide, for example. The word line WL is formed from titanium
nitride (TiN), for example. The inter-layer insulating film 106 is
formed by a material different from that of the inter-layer
insulating films 104 and 107, and is formed from silicon nitride
(SiN), for example.
[0036] In addition, the memory cell array 1 includes the via
Z1<i> that extends in the Z direction and reaches at least
from an upper surface of the inter-layer insulating film 106 to a
bottom surface of the word line WL<i>. In the case of FIG. 5,
the via Z1<i> reaches from an upper surface of the
inter-layer insulating film 107 to an upper surface of the via
Z0<i>. The via Z1<i> penetrates the contact portion
WLb<i> of the word line WL<i> that the via Z1<i>
contacts. Side surfaces of each of the vias Z1<i> and side
surfaces of the word lines WL<0> to WL<i> have an
insulating film 109 disposed between them, and the two are not in
contact. The insulating film 109 is formed by a material different
from that of the inter-layer insulating film 106, and is formed
from silicon oxide (SiO.sub.2), for example. In addition, each of
the vias Z1<i> has the projecting part Z1b<i> that
projects on both sides in the X direction at the same height as the
inter-layer insulating film 106. This projecting part Z1b<i>
has a width that exceeds the insulating film 109 to reach the
contact portion WLb<i> in the X direction, and a bottom
surface of the projecting part Z1b<i> contacts the contact
portion WLb<i> and the insulating film 109. In other words,
due to the above-described connection structure of the contact
region 1b of the memory cell array 1, the via Z1<i> contacts
the word line WL<i> while being insulated from the word line
WL<l> in a lower layer.
[0037] Next, manufacturing steps of the contact region 1b of the
memory cell array 1 will be described.
[0038] FIGS. 6 to 13 are cross-sectional views describing the
manufacturing steps of the contact region of the memory cell array
of the semiconductor device according to the present
embodiment.
[0039] First, the etching stop film 103 is deposited on each of the
conductive films 101<i> (i=0 to 3) and the inter-layer
insulating film 102. Each of the conductive films 101<i> is
formed by titanium nitride (TiN), for example, and functions as the
via Z0<i>. The etching stop film 103 is formed by a metal
oxide, for example, and will be a film for suppressing over-etching
of the conductive film 101 during formation of a hole 122 in a
later step. Next, a plurality of the inter-layer insulating films
104 and conductive films 105 are stacked alternately on the etching
stop film 103. Now, the inter-layer insulating film 104 is formed
by silicon oxide (SiO.sub.2), for example. The conductive film 105
is formed from titanium nitride (TiN), for example, and functions
as the word line WL. Next, as shown in FIG. 6, the conductive films
105 are formed in a stepped shape in the contact region 1b of the
memory cell array 1. As a result, a contact portion 105b<i>
is formed in each of the conductive films 105<i>.
[0040] Next, the inter-layer insulating film 106 is deposited on a
stacked conductive film configured from the conductive films
101<0> to 101<3>. This inter-layer insulating film 106
contacts each of the contact portions 105b<i>. The
inter-layer insulating film 106 is formed by a material allowing an
etching selectivity ratio to be taken with respect to materials of
the inter-layer insulating film 104 and the inter-layer insulating
film 107 and insulating film 109 formed in a later step. When the
inter-layer insulating films 104 and 107 and the insulating film
109 are formed by silicon oxide (SiO.sub.2), the inter-layer
insulating film 106 is formed by silicon nitride (SiN), for
example. Next, the inter-layer insulating film 107 is deposited on
top of the inter-layer insulating film 106. Now, the inter-layer
insulating film 107 is formed by silicon oxide (SiO.sub.2), for
example. Next, as shown in FIG. 7, a resist film 121 having a
pattern of the via Z1 is deposited on the inter-layer insulating
film 107.
[0041] Next, as shown in FIG. 8, the hole 122<i> reaching
from an inter-layer insulating film 107 upper surface to an upper
surface of the etching stop film 103 is formed at a position of
each of the contact portions 105b<i>, by anisotropic etching
using the resist film 121.
[0042] Next, as shown in FIG. 9, each of the holes 122<i> is
continued to be dug out, by anisotropic etching using the resist
film 121, until the etching stop film 103 is penetrated to expose
an upper surface of the conductive film 101<i>. Note that a
plurality of the holes 122 can be formed simultaneously during the
steps shown in FIGS. 8 and 9.
[0043] Next, as shown in FIG. 10, ends of the conductive films
105<0> to 105<i> exposed in a side surface of the hole
122<i> (places 105e shown by the broken lines of FIG. 10) are
selectively removed by isotropic etching via the hole
122<i>.
[0044] Next, the resist film 121 is removed, and then, as shown in
FIG. 11, the insulating film 109 is implanted in the place 105e
shown in FIG. 10. The insulating film 109 is formed by silicon
oxide (SiO.sub.2), for example.
[0045] Next, as shown in FIG. 12, an end of the inter-layer
insulating film 106 exposed in the side surface of the hole
122<i> is selectively removed, by isotropic etching via the
hole 122<i>, until the upper surface of the uppermost layer
conductive film 105<i> at each place is exposed. As a result,
a place 106e for disposing the projecting part Z1b<i> of the
via Z1<i> contacting the contact portion 105b<i> is
formed in the side surface of the hole 122<i>.
[0046] Finally, as shown in FIG. 13, a conductive film 108<i>
is implanted in the hole 122<i>, and then an upper surface of
the conductive film 108<i> is planarized by the likes of CMP
(Chemical Mechanical Polishing). The conductive film 108<i>
is formed by titanium nitride (TiN), for example, and functions as
the via Z1<i>. As a result, as shown in FIG. 5, the via
Z1<i> contacting the word line WL<i> and the via
Z0<i>, is formed.
[0047] As a result of the above manufacturing steps, the connection
structure of the contact region 1b of the memory cell array 1 shown
in FIG. 5 is formed.
[0048] Next, advantages of the present embodiment will be described
using a comparative example.
[0049] In a semiconductor device according to the comparative
example employed herein, each of the word lines and the peripheral
circuit are electrically connected by a first via (corresponding to
the via Z1 of the present embodiment) that reaches from the word
line to an upper layer wiring line, a second via that passes
outside an arrangement region of the word line to reach from the
upper layer wiring line to a third via (corresponding to the via Z0
of the present embodiment), and the third via that reaches from the
second via to the peripheral circuit. Note that the first via does
not have a portion corresponding to the projecting part Z1b of the
present embodiment, and a bottom surface of the first via directly
contacts an upper surface of the word line. In the case of the
comparative example, interference between the word line of a lower
layer and the via is avoided by once diverting a current path
reaching from the word line to the peripheral circuit, to the upper
layer wiring line.
[0050] In the case of this comparative example, three vias become
necessary for every one word line. In particular, a space for
disposing the second via becomes unnecessarily required for the
contact region of the memory cell array, and this leads to an
increase in chip size.
[0051] In this respect, in the case of the present embodiment, only
the two vias Z1 and Z0 need be disposed for one word line WL, and
when viewed from the Z direction, only a single via portion of
arrangement region need be prepared. In other words, the present
embodiment enables the space for via arrangement to be suppressed
to half or less, compared to in the comparative example.
[0052] Moreover, in the case of the comparative example, as
previously mentioned, the bottom surface of the first via and the
upper surface of the word line are in direct contact, hence when
forming a hole (corresponding to 122 of the present embodiment) for
disposing the first via, a bottom surface of this hole must be
matched to the upper surface of the word line. Now, when
considering the case of forming a plurality of first vias
contacting a plurality of word lines of different heights, the
holes for disposing these first vias will each have a different
depth. Therefore, if it is attempted to form these holes
simultaneously, there is a risk that due to the influence of
etching of a deeper hole, a shallower hole is over-etched. In a
particularly severe case, it is also conceivable that the hole not
only penetrates the word line desired to be brought into contact
with the first via, but also ends up reaching the word line of a
lower layer.
[0053] In this respect, in the case of the present embodiment, not
only is it possible to align positions of the bottom surfaces of
the vias Z1, but furthermore, there is a connection structure
presupposing that each of the vias Z1<i> penetrates the word
lines WL<0> to WL<i>. Therefore, even when the holes
122 are formed simultaneously, the risk of over-etching when
forming holes of different depths as in the comparative example,
can be eliminated.
[0054] As is clear from the above, the present embodiment makes is
possible to provide: a semiconductor device that achieves a
reduction in chip size by reducing space of a contact region and
achieves a reduction in processing difficulty during via formation;
and a method of manufacturing the same.
Second Embodiment
[0055] First, a connection structure of a memory cell array 1 and a
peripheral circuit on a semiconductor substrate related to a second
embodiment will be described exemplifying a connection structure of
a word line WL and the peripheral circuit.
[0056] FIG. 14 is a cross-sectional view of a contact region of the
memory cell array of a semiconductor device according to the
present embodiment. FIG. 14 is a cross-sectional view of a via
Z1<3> periphery.
[0057] A via Z1<i> of the present embodiment (i=0 to 3; in
the case of FIG. 14, i=3) has a projecting part Z1b<i> formed
only on one of side surfaces facing in the X direction, and
contacts the word line WL<i> only on one side in the X
direction.
[0058] In the case of the first embodiment, the projecting part
Z1b<i> was formed so as to surround an entire periphery of
the via Z1<i>, but contact with the word line WL<i> is
possible even when the projecting part Z1b<i> is formed only
on part of the periphery of the via Z1<i> as in the present
embodiment. In other words, the present embodiment enables contact
between the via Z1<i> and the word line WL<i>,
similarly to in the first embodiment, even when the word line
WL<i> has a contact portion WLb<i> of a shape not
allowing the entire periphery of the via Z1<i> to be
surrounded.
[0059] Next, manufacturing steps of a contact region 1b of the
memory cell array 1 will be described.
[0060] FIGS. 15 to 18 are cross-sectional views describing the
manufacturing steps of the contact region of the memory cell array
of the semiconductor device according to the present
embodiment.
[0061] First, a conductive film 201<i> (corresponding to 101
of FIG. 6) functioning as the via Z1<i> (i=0 to 3; in the
case of FIGS. 15 to 18, i=3) and an inter-layer insulating film 202
(corresponding to 102 of FIG. 6) have a stacked body formed
thereon, the stacked body being configured from: an etching stop
film 203 (corresponding to 103 of FIG. 6); a plurality of
inter-layer insulating films 204 (corresponding to 104 of FIG. 6);
a plurality of conductive films 205 (corresponding to 105 of FIG.
6) functioning as a plurality of the word lines WL; and an
inter-layer insulating film 206 (corresponding to 106 of FIG. 7).
Now, the inter-layer insulating film 206 is formed by a material
allowing an etching selectivity ratio to be taken with respect to
materials of the inter-layer insulating film 204 and an inter-layer
insulating film 207 (corresponding to 107 of FIG. 7) and insulating
film 209 (corresponding to 109 of FIG. 11) formed in a later step.
Next, ends of the inter-layer insulating film 204, the conductive
film 205, and the inter-layer insulating film 206 are removed at a
position of the conductive film 201<i>, and then the
inter-layer insulating film 207 is deposited on the conductive film
201<i>, the inter-layer insulating film 202, and the
inter-layer insulating film 206. Next, as shown in FIG. 15, a
resist film 221 having a pattern of the via Z1<i> is
deposited on the inter-layer insulating film 207.
[0062] Next, as shown in FIG. 16, a hole 222<i> reaching from
an upper surface of the inter-layer insulating film 206 to an upper
surface of the conductive film 201<i> is formed at a position
where the end of the conductive film 205 appears on a side surface,
by anisotropic etching using the resist film 221.
[0063] Next, ends of the conductive films 205<0> to
205<i> exposed in the side surface of the hole 222<i>
are selectively removed by isotropic etching via the hole
222<i>. Next, as shown in FIG. 17, the insulating film 209 is
implanted in said removed places.
[0064] Next, as shown in FIG. 18, an end of the inter-layer
insulating film 206 exposed in the side surface of the hole
222<i> is selectively removed, by isotropic etching via the
hole 222<i>, until an upper surface of the conductive film
205<i> is exposed. As a result, a place 206e for disposing
the projecting part Z1b<i> of the via Z1<i> contacting
a contact portion 205b<i> is formed on one of side surfaces
of the hole 222<i>.
[0065] Next, the resist film 221 is detached. Finally, a conductive
film functioning as the via Z1<i> is implanted in the hole
222<i>, and then an upper surface of this conductive film is
planarized by the likes of CMP. As a result, as shown in FIG. 14,
the via Z1<i> contacting the word line WL<i> and the
via Z0<i>, is formed.
[0066] As a result of the above manufacturing steps, the connection
structure of the contact region 1b of the memory cell array 1 shown
in FIG. 14 is formed.
[0067] As is clear from the above, the present embodiment also
allows similar advantages to those of the first embodiment to be
obtained even when contact is made with a wiring line of the memory
cell array by part of the periphery of the via.
OTHERS
[0068] 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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