U.S. patent number RE46,882 [Application Number 14/539,727] was granted by the patent office on 2018-05-29 for semiconductor device and method for manufacturing the same.
This patent grant is currently assigned to Longitude Semiconductor S.a.r.l.. The grantee listed for this patent is PS4 Luxco S.a.r.l.. Invention is credited to Noriaki Ikeda, Kenji Komeda, Yoshitaka Nakamura, Ryota Suewaka.
United States Patent |
RE46,882 |
Nakamura , et al. |
May 29, 2018 |
**Please see images for:
( Certificate of Correction ) ** |
Semiconductor device and method for manufacturing the same
Abstract
A semiconductor device comprises a memory cell region, a
peripheral circuit region and a boundary region. In the memory cell
region, a concave lower electrode and a foundation layer have a
same uppermost surface positioned in a height of H above the
plane-A. In the boundary region, one concave lower conductive
region and a foundation layer have a same uppermost surface
positioned in a height of H above the plane-A.
Inventors: |
Nakamura; Yoshitaka (Tokyo,
JP), Komeda; Kenji (Tokyo, JP), Suewaka;
Ryota (Tokyo, JP), Ikeda; Noriaki (Tokyo,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
PS4 Luxco S.a.r.l. |
Luxembourg |
N/A |
LU |
|
|
Assignee: |
Longitude Semiconductor
S.a.r.l. (Luxembourg, LU)
|
Family
ID: |
40849880 |
Appl.
No.: |
14/539,727 |
Filed: |
November 12, 2014 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
12318735 |
Jan 7, 2009 |
8188529 |
May 29, 2012 |
|
|
Foreign Application Priority Data
|
|
|
|
|
Jan 10, 2008 [JP] |
|
|
2008-003284 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
28/91 (20130101); H01L 27/10817 (20130101); H01L
27/10808 (20130101); H01L 27/0207 (20130101); H01L
27/10835 (20130101); H01L 27/10894 (20130101); H01L
27/10852 (20130101); H01L 29/78 (20130101) |
Current International
Class: |
H01L
27/108 (20060101) |
Field of
Search: |
;438/239,241,396
;257/296,306,309 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
07-007084 |
|
Jan 1995 |
|
JP |
|
11-026713 |
|
Jan 1999 |
|
JP |
|
2002-009259 |
|
Jan 2002 |
|
JP |
|
2003-297952 |
|
Oct 2003 |
|
JP |
|
Primary Examiner: Nguyen; Tuan H
Claims
What is claimed is:
1. A semiconductor device, comprising: a memory cell region; a
peripheral circuit region; a boundary region formed in a boundary
.Iadd.to extend across substantially all of a lower surface of an
isolation insulating film positioned .Iaddend.between the memory
cell region and the peripheral circuit region; and an interlayer
insulating film formed across the peripheral circuit region and
.Iadd.in .Iaddend.the boundary region, wherein the memory cell
region comprises: a concave lower electrode formed so as to extend
upwardly from below plane-A having level equal to an upper surface
of the interlayer insulating film and protruding by a height of H
above the plane-A; and a foundation layer having a thickness of H
formed at least in part on the plane-A other than .[.the.]. .Iadd.a
.Iaddend.part thereof taken up by the lower electrode,
.Iadd.wherein .Iaddend.the boundary region comprises: one concave
lower conductive region formed so as to extend upwardly from below
plane-A having level equal to the upper surface of the interlayer
insulating film and protruding by a height of H above the plane-A;
and the foundation layer having a thickness of H formed on the
upper surface of the interlayer insulating film .Iadd.in the
boundary region other than a part thereof taken up by the one
concave lower conductive region.Iaddend., and .Iadd.wherein
.Iaddend.the memory cell region and the boundary region comprise: a
dielectric film formed so as to cover surfaces of the lower
electrode, the lower conductive region and the foundation layer;
and an upper conductive region including a conductive layer formed
so as to have contact with an uppermost surface of a portion of the
dielectric film over the plane-A and the interlayer insulating
film, and a convex portion branching off from the conductive layer
and disposed facing to the lower electrode and the lower conductive
region with an intervention of the dielectric film
therebetween.Iadd.; and wherein the interlayer insulating film is
adjacent to and in contact with the foundation layer in a portion
of the boundary region between the lower conductive region and the
peripheral circuit region, and the interlayer insulating film is
removed from contact with the foundation layer in the memory cell
region.Iaddend..
2. The semiconductor device according to claim 1, wherein in the
memory cell region, the concave lower electrode, the dielectric
film covering the concave lower electrode, and the convex portion
of the upper conductive region constitute a capacitor.
3. The semiconductor device according to claim 2, wherein the
memory cell region includes at least two capacitors adjacent to
each other, and further includes at least two field-effect
transistors sharing a first impurity-diffused region and comprising
independent second impurity-diffused regions, and each of the
second impurity-diffused regions of the field-effect transistors is
electrically connected to the capacitor through a first contact
plug.
4. The semiconductor device according to claim 1, wherein the
boundary region further comprises a second contact plug
electrically connected to the conductive layer of the upper
conductive region, the peripheral circuit region further comprises:
a field-effect transistor; and two third contact plugs electrically
connected to a third impurity-diffused region and a fourth
impurity-diffused region of the field-effect transistor, and the
second contact plug and at least one of the third contact plugs are
electrically connected to each other through an interconnect
layer.
5. The semiconductor device according to claim 1, wherein the H is
50 nm to 200 nm.
6. The semiconductor device according to claim 1, wherein a height
of the lower electrode is 0.5 .mu.m to 4 .mu.m.
7. A semiconductor device, comprising: a memory cell region
comprising: a first capacitor with a crown structure; a second
capacitor with a crown structure having the same uppermost surface
as the first capacitor; and a first foundation layer formed between
the first capacitor and the second capacitor so as to have the same
uppermost surface as the first and second capacitors, a peripheral
circuit region formed surrounding the memory cell region, and a
boundary region formed .Iadd.to extend across substantially all of
a lower surface of an isolation insulating film positioned
.Iaddend.between the memory cell region and the peripheral circuit
region, comprising: a dummy capacitor disposed so as to surround
the memory cell region, and formed so as to have the same uppermost
surface as the first and second capacitors; and a second foundation
layer formed .Iadd.on an upper surface of an interlayer insulating
film in the boundary region and .Iaddend.between the capacitor
positioned in a boundary region side among the first and the second
capacitors and the dummy capacitor .Iadd.and to substantially cover
the boundary region other than a part thereof taken up by the dummy
capacitor.Iaddend., so as to have the same uppermost level as the
first and second capacitors.Iadd.; wherein the interlayer
insulating film is formed across the peripheral circuit region, and
is formed in the boundary region adjacent and in contact with the
second foundation layer, and is removed from contact with the first
foundation layer in the memory cell region.Iaddend..
8. The semiconductor device according to claim 7, wherein the
memory cell region further comprises: a third capacitor with a
crown structure; two field-effect transistors sharing a first
impurity-diffused region and comprising independent second
impurity-diffused regions; and a first contact plug electrically
connecting each of the second impurity-diffused regions of the
field-effect transistors with the second and the third
capacitors.
9. The semiconductor device according to claim 7, wherein the
boundary region further comprises a second contact plug
electrically connected to the dummy capacitor, the peripheral
circuit region further comprises: a field-effect transistor; and
two third contact plugs electrically connected to a third
impurity-diffused region and a fourth impurity-diffused region of
the field-effect transistor, and the second contact plug and at
least one of the third contact plugs are electrically connected to
each other through an interconnect layer.
10. The semiconductor device according to claim 7, wherein a
thickness of the first and the second foundation layers is 50 nm to
200 nm.
11. The semiconductor device according to claim 7, wherein a height
of the dummy capacitor is 0.5 .mu.m to 4 .mu.m.
12. A semiconductor device comprising: a memory cell region; a
peripheral region; and a boundary region .Iadd.formed to extend
across substantially all of a lower surface of an isolation
insulating film positioned .Iaddend.between the memory cell region
and the peripheral region, the memory cell region including: a
plurality of cell capacitors; and a foundation layer coupling the
cell capacitors to one another at an uppermost portion of lower
electrodes of the cell capacitors .[.and.]..Iadd., the foundation
layer .Iaddend.including a plurality of holes, the foundation layer
being elongated to form an elongated portion .[.over.]. .Iadd.to
substantially cover .Iaddend.the boundary region.Iadd.; wherein an
interlayer insulating film is formed across the peripheral circuit
region, is formed adjacent and in contact with the elongated
portion of the foundation layer in the boundary region, and is
removed from contact with the foundation layer in the memory cell
region.Iaddend..
13. The semiconductor device according to claim 12, wherein the
boundary region comprises a dummy capacitor, the dummy capacitor
being coupled to the cell capacitors via the elongated portion of
the foundation layer.
14. The semiconductor device according to claim 12, wherein the
memory cell region further includes: at least two cell capacitors
adjacent to each other; two field-effect transistors sharing a
first impurity diffused region and comprising independent second
impurity diffused regions; and a first contact plug electrically
connecting each of the second impurity-diffused regions of the
field-effect transistors with the cell capacitors.
15. The semiconductor device according to claim 13, wherein the
boundary region further comprises a second contact plug
electrically connected to the dummy capacitor, the peripheral
circuit region comprises: a field-effect transistor; and two third
contact plugs electrically connected to a third impurity-diffused
region and a fourth impurity-diffused region of the field-effect
transistor, and the second contact plug and at least one of the
third contact plugs are electrically connected to each other
through an interconnect layer.
16. The semiconductor device according to claim 12, wherein the
thickness of the foundation layer is 50 nm to 200 nm.
17. The semiconductor device according to claim 13, wherein a
height of the dummy capacitor is 0.5 .mu.m to 4 .mu.m.
.Iadd.18. The semiconductor device according to claim 12, wherein
an end of the foundation layer substantially coinciding with the
boundary region..Iaddend.
.Iadd.19. The semiconductor device according to claim 1, wherein
the boundary region includes only one concave lower conductive
region..Iaddend.
Description
.Iadd.CROSS REFERENCE TO RELATED APPLICATIONS.Iaddend.
.Iadd.The present application is a reissue application of U.S. Pat.
No. 8,188,529; the entire contents of which are incorporated herein
by reference..Iaddend.
This application is based upon and claims the benefit of priority
from Japanese Patent Application No. 2008-003284, filed on Jan. 10,
2008, the disclosure of which is incorporated herein in its
entirety by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device which
includes a memory cell region, a peripheral circuit region, and a
boundary region in a boundary between the memory cell region and
the peripheral circuit region and in which no step difference is
formed in the boundary, and to a method for manufacturing the
semiconductor device.
2. Description of the Related Art
A memory device, such as a DRAM (Dynamic Random Access Memory),
generally comprises a memory cell region for storing information, a
peripheral circuit region for controlling the writing/reading of
information to this memory cell region, and a boundary region
present between the memory cell region and the peripheral circuit
region.
This memory cell region generally comprises a plurality of memory
cells, each of which comprises a select transistor and a capacitor.
In recent years, this memory device has had the problem of a
decrease in the amount of charge accumulated in the capacitor as a
result of the memory cells being miniaturized due to the
development of microfabrication technique.
Hence, a crown-structured capacitor has been adopted in order to
solve this problem. This crown-structured capacitor is constructed
in such a manner that a lower electrode, a dielectric film and an
upper electrode are formed within a concavely-formed opening so as
to extend along the inner wall thereof, thereby increasing the area
of the capacitor. Japanese Patent Laid-Open No. 7-7084 discloses a
semiconductor device with this crown-structured capacitor and a
method for manufacturing the semiconductor device.
When forming this crown-structured capacitor, it is important to
eliminate a step difference present in a boundary between the
memory cell region and the peripheral circuit region, from the
viewpoint of making a process in a later interconnection step
easy.
Hence, in the method disclosed in Japanese Patent Laid-Open No.
7-7084, several rows of trenches comprised of lower electrodes are
formed in the boundary region between the memory cell region and
the peripheral circuit region and an interlayer insulating film in
the memory cell region is removed by wet etching, with at least one
trench and the peripheral circuit region covered with a photoresist
film.
FIGS. 20 to 31 illustrate a method for manufacturing such a related
semiconductor device as shown by way of example in Japanese Patent
Laid-Open No. 7-7084. First, gate oxide film 3, gate electrode 4,
diffusion layer regions (source/drain regions) 5, 6, 7 and 7a,
polysilicon plugs 11 and 11a, metal plugs 12, 41, 41a, 42 and 42a,
bit line 8, first layer interconnects 8a and 8b, landing pad 81,
lower layers 81c (two layers parallel to each other), and the like
are formed on a substrate constituting the memory cell region and
the peripheral circuit region. FIG. 20 is a cross-sectional view
illustrating this condition, whereas FIG. 21 is a top view
illustrating the upper portion of the memory cell region after the
patterning of landing pad 81 and lower layers 81c.
Next, interlayer insulating film (silicon nitride film) 32 and
interlayer insulating film (oxide silicon film) 24 are successively
formed on the entire surface of the resulting structure. FIG. 22 is
a cross-sectional view illustrating this condition. After this,
cylinder hole 91 is created using a photolithographic technique and
a dry etching technique, so as to penetrate through interlayer
insulating films 24 and 32, thereby exposing a surface of landing
pad 81 on the bottom face of cylinder hole 91. At this time,
cylinder trench 91a is created in a boundary region concurrently
with creating cylinder hole 91, thereby exposing lower layer 81c on
the bottom of cylinder trench 91a. FIG. 23 is a cross-sectional
view illustrating this condition, whereas FIG. 24 is a top view
illustrating an edge of the memory cell region after the patterning
of cylinder hole 91 and cylinder trench 91a.
Next, using a CVD method, first titanium nitride film 51 is grown
on the entire surface of the resulting structure. Next, a
photoresist film (not illustrated) is filled into cylinder hole 91
and cylinder trench 91a, and then a portion of the first titanium
nitride film located upper than interlayer insulating film 24 is
etched back and removed. Consequently, it is possible to obtain
concave lower electrode 51 on the inner wall of cylinder hole 91 in
the memory cell region and concave lower conductive region 51a on
the inner wall of cylinder hole 91a in the boundary region. Next,
the photoresist film is removed using an organic separating liquid.
FIG. 25 is a cross-sectional view illustrating this condition,
whereas FIG. 26 is a top view illustrating an edge of the memory
cell region after the etching back of the titanium nitride
film.
Next, using a photolithographic technique, photoresist film 96 is
formed in the peripheral circuit (logic circuit) region and in part
of the boundary region. At this time, alignment is performed so
that at least one of two parallel lower conductive regions 51a in
the boundary region is covered with the photoresist film. FIG. 27
is a cross-sectional view illustrating this condition, whereas FIG.
28 is a top view illustrating an edge of the memory cell region
after the formation of photoresist film 96.
The reason for two lower conductive regions 51a being formed in
this way is that, as shown in Japanese Patent Laid-Open No. 7-7084,
the photoresist film is formed so that an edge thereof is shifted
toward the peripheral circuit region side in some cases due to
misalignment. That is, the two lower conductive regions are formed
in order to prevent any portions, in which the photoresist film is
not present, from being formed on the peripheral circuit (logic
circuit) region, thereby preventing interlayer insulating film 24
in the peripheral circuit (logic circuit) region from being eroded
by later wet etching.
Next, a portion of interlayer insulating film (oxide silicon film)
24 in the memory cell region is removed by a wet etching method
using a dilute hydrofluoric acid (HF) solution. At this time,
photoresist film 96 serves as a mask in the peripheral circuit
region (logic circuit region) and, therefore, interlayer insulating
film (oxide silicon film) 24 remains without being removed. FIG. 29
is a cross-sectional view illustrating this condition, whereas FIG.
30 is a top view illustrating an edge of the memory cell region
after the removal of interlayer insulating film 24.
Next, dielectric film 52, upper electrode (second titanium nitride)
53, second layer interconnects 61 and 61a, and the like are formed,
thereby finally obtaining the semiconductor device. FIG. 31 is a
cross-sectional view illustrating this condition.
We have now discovered that there are the below-mentioned problems
with such a semiconductor device and a method for manufacturing the
semiconductor device as shown by way of example in FIGS. 21 to 30
mentioned above: (1) The area of the boundary region becomes large
due to the presence of two lower conductive regions (cylinder
trenches arranged around the memory cell region). As a result, the
chip area also becomes large and, therefore, the cost of
manufacture increases. (2) Since a photoresist film is used as a
mask for the peripheral circuit (logic circuit) region when
removing portions of the interlayer insulating film in the memory
cell region and the boundary region by a wet etching method,
foreign matter is produced during wet etching. That is, the
photoresist film reacts with a dilute hydrofluoric acid (HF)
solution at the time of wet etching and changes in quality, thus
producing polymer-like foreign matter. Alternatively, watermarks or
the like is produced since IPA (isopropyl alcohol) cannot be used
when drying a wafer after wet etching. Consequently, the yield of
manufacture degrades. (3) A lower electrode collapses or adjacent
lower electrodes come into contact with each other due to the
absence of a foundation layer in the memory cell region. In
particular, the lower electrode becomes easy to collapse due to
surface tension produced during wet etching with a lower electrode
exposed. Consequently, the yield of manufacture degrades.
Accordingly, the present inventors have recognized that it is
possible to solve problems (1) to (3) mentioned above by forming a
silicon nitride film which serves as a mask for the peripheral
circuit (logic circuit) region and as a foundation layer in the
memory cell region at the time of wet etching.
SUMMARY OF THE INVENTION
The present invention seeks to solve one or more of the above
problems, or to improve upon those problems at least in part.
In one embodiment, there is provided a semiconductor device,
comprising:
a memory cell region;
a peripheral circuit region;
a boundary region formed in a boundary between the memory cell
region and the peripheral circuit region; and
an interlayer insulating film formed across the peripheral circuit
region and the boundary region,
wherein the memory cell region comprises:
a concave lower electrode formed so as to extend upwardly from
below plane-A having level equal to an upper surface of the
interlayer insulating film and protruding by a height of H above
the plane-A; and
a foundation layer having a thickness of H formed at least in part
on the plane-A other than the part thereof taken up by the lower
electrode,
the boundary region comprises:
one concave lower conductive region turned so as to extend upwardly
from below plane-A having level equal to the upper surface of the
interlayer insulating film and protruding by a height of H above
the plane-A; and
the foundation layer having a thickness of H formed on the upper
surface of the interlayer insulating film, and
the memory cell region and the boundary region comprise:
a dielectric film formed so as to cover surfaces of the lower
electrode, the lower conductive region and the foundation layer;
and
an upper conductive region including a conductive layer formed so
as to have contact with an uppermost surface of a portion of the
dielectric film over the plane-A and the interlayer insulating
film, and a convex portion branching off from the conductive layer
and disposed facing to the lower electrode and the lower conductive
region with an intervention of the dielectric film
therebetween.
In another embodiment, there is provided a semiconductor device,
comprising:
a memory cell region comprising:
a first capacitor with a crown structure;
a second capacitor with a crown structure having the same uppermost
surface as the first capacitor; and
a first foundation layer formed between the first capacitor and the
second capacitor so as to have the same uppermost surface as the
first and second capacitors,
a peripheral circuit region formed surrounding the memory cell
region, and
a boundary region formed between the memory cell region and the
peripheral circuit region, comprising:
a dummy capacitor disposed so as to surround the memory cell
region, and formed so as to have the same uppermost surface as the
first and second capacitors; and
a second foundation layer formed between the capacitor positioned
in a boundary region side among the first and the second capacitors
and the dummy capacitor, so as to have the same uppermost level as
the first and second capacitors.
In another embodiment, there is provided a method for manufacturing
a semiconductor device including a memory cell region, a peripheral
circuit region, and a boundary region formed in a boundary between
the memory cell region and the peripheral circuit region, the
method comprising:
(1) forming an interlayer insulating film across the memory cell
region, the peripheral circuit region, and the boundary region;
(2) forming a foundation layer having a thickness of H on the
entire surface of the interlayer insulating film;
(3) forming an opening extending within the foundation layer and
the interlayer insulating film of the memory cell region in a
thickness direction thereof, and one opening extending within the
foundation layer and the interlayer insulating film of the boundary
region in the thickness direction thereof;
(4) forming a concave lower electrode on an inner wall of the
opening in the memory cell region and a concave lower conductive
region on an inner wall or the opening in the boundary region;
(5) performing isotropic etching using the foundation layer, the
lower electrode and the lower conductive region as masks and
etching stoppers, to remove portions of the interlayer insulating
film within the memory cell region and the boundary region;
(6) forming a dielectric film so as to cover the memory cell
region, the peripheral circuit region, and the boundary region;
(7) depositing a conductive material on the memory cell region, the
peripheral circuit region and the boundary region, and forming a
conductive film disposed facing to the lower electrode and the
lower conductive region with an intervention of the dielectric film
therebetween; and
(8) removing portions of the foundation layer, the dielectric film
and the conductive film on the interlayer insulating film of the
peripheral circuit region.
BRIEF DESCRIPTION OF THE DRAWINGS
The above features and advantages of the present invention will be
more apparent from the following description of certain preferred
embodiments taken in conjunction with the accompanying drawings, in
which:
FIG. 1 is a schematic view illustrating one example of a
semiconductor device of the present invention;
FIG. 2 is a schematic view illustrating one step of a method for
manufacturing a semiconductor device of the present invention;
FIG. 3 is another schematic view illustrating one step of a method
for manufacturing the semiconductor device of the present
invention;
FIG. 4 is yet another schematic view illustrating one step of a
method for manufacturing the semiconductor device of the present
invention;
FIG. 5 is still another schematic view illustrating one step of a
method for manufacturing the semiconductor device of the present
invention;
FIG. 6 is still another schematic view illustrating one step of a
method for manufacturing the semiconductor device of the present
invention;
FIG. 7 is still another schematic view illustrating one step of a
method for manufacturing the semiconductor device of the present
invention;
FIG. 8 is still another schematic view illustrating one step of a
method for manufacturing the semiconductor device of the present
invention;
FIG. 9 is still another schematic view illustrating one step of a
method for manufacturing the semiconductor device of the present
invention;
FIG. 10 is still another schematic view illustrating one step of a
method for manufacturing the semiconductor device of the present
invention;
FIG. 11 is still another schematic view illustrating one step of a
method for manufacturing the semiconductor device of the present
invention;
FIG. 12 is still another schematic view illustrating one step of a
method for manufacturing the semiconductor device of the present
invention;
FIG. 13 is still another schematic view illustrating one step of a
method for manufacturing the semiconductor device of the present
invention;
FIG. 14 is still another schematic view illustrating one step of a
method for manufacturing the semiconductor device of the present
invention;
FIG. 15 is still another schematic view illustrating one step of a
method for manufacturing the semiconductor device of the present
invention;
FIG. 16 is still another schematic view illustrating one step of a
method for manufacturing the semiconductor device of the present
invention;
FIG. 17 is still another schematic view illustrating one step of a
method for manufacturing the semiconductor device of the present
invention;
FIG. 18 is still another schematic view illustrating one step of a
method for manufacturing the semiconductor device of the present
invention;
FIG. 19 is still another schematic view illustrating one step of a
method for manufacturing the semiconductor device of the present
invention;
FIG. 20 is a schematic view illustrating one step of a method for
manufacturing a related semiconductor device;
FIG. 21 is another schematic view illustrating one step of a method
for manufacturing the related semiconductor device;
FIG. 22 is yet another schematic view illustrating one step of a
method for manufacturing the related semiconductor device;
FIG. 23 is still another schematic view illustrating one step of a
method for manufacturing the related semiconductor device;
FIG. 24 is still another schematic view illustrating one step of a
method for manufacturing the related semiconductor device;
FIG. 25 is still another schematic view illustrating one step of a
method for manufacturing the related semiconductor device;
FIG. 26 is still another schematic view illustrating one step of a
method for manufacturing the related semiconductor device;
FIG. 27 is still another schematic view illustrating one step of a
method for manufacturing the related semiconductor device;
FIG. 28 is still another schematic view illustrating one step of a
method for manufacturing the related semiconductor device;
FIG. 29 is still another schematic view illustrating one step of a
method for manufacturing the related semiconductor device;
FIG. 30 is still another schematic view illustrating one step of a
method for manufacturing the related semiconductor device; and
FIG. 31 is still another schematic view illustrating one step of a
method for manufacturing the related semiconductor device.
In the drawings, numerals have the following meanings. 3: gate
insulating film, 4: gate electrode, 5, 6, 7, 7a: impurity-diffused
region (source/drain region), 8, 8a, 8b, 8c: first layer
interconnect, 10: silicon semiconductor substrate, 11, 11a: contact
plug, 12, 41, 41a, 42, 42a, 43, 43a, 44: metal plug, 21, 22, 25,
26, 36: interlayer insulating film, 24: interlayer insulating film
(oxide silicon film), 32: interlayer insulating film (silicon
nitride film), 51: lower electrode, 51a: lower conductive region,
52: dielectric film, 53: upper electrode, 61, 61a: second layer
interconnect, 71: upper surface of interlayer insulating film, 72:
conductive layer, 73: uppermost surface of dielectric film, 74:
convex portion, 81: landing pad, 81a, 81b: local interconnect, 91:
cylinder hole, 91a: cylinder trench, 96: photoresist film.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention will be now described herein with reference to
illustrative embodiments. Those skilled in the art will recognize
that many alternative embodiments can be accomplished using the
teachings of the present invention and that the invention is not
limited to the embodiments illustrated for explanatory
purposes.
1. Semiconductor Device
A semiconductor device comprises a memory cell region, a peripheral
circuit region, and a boundary region formed between the memory
cell region and the peripheral circuit region. In addition, an
interlayer insulating film is formed across the peripheral circuit
region and the boundary region. Typically, the interlayer
insulating film is formed in part in the boundary region.
This memory cell region includes a concave lower electrode and a
foundation layer having a thickness of H. This concave lower
electrode is formed so as to extend upwardly from below plane-A
having level equal to the upper surface of the interlayer
insulating film and protrudes by a height of H above plane-A. In
addition, the foundation layer having a thickness of H is formed at
least in part on plane-A other than the part thereof taken up by
the lower electrode. In this memory cell region, only the lower
electrode and the foundation layer may be formed on plane-A, or
other layers or regions may be formed thereon in addition to the
lower electrode and the foundation layer. For example, in the
memory cell region of FIG. 1, there are formed a dielectric film
and an upper conductive region on part of plane-A between adjacent
lower electrodes.
In addition, the boundary region includes one concave lower
conductive region and a foundation layer having a thickness of H.
This concave lower conductive region is formed so as to extend
upwardly from below plane-A having level equal to the upper surface
of the interlayer insulating film, and protrudes by a height of H
above plane-A. The foundation layer having a thickness of H is
formed on the upper surface of a portion of the interlayer
insulating film present in the boundary region. That is, the
concave lower conductive region and the foundation layer having a
thickness of H exist respectively on plane-A and on the upper
surface of the interlayer insulating film in the boundary
region.
Consequently, all of the uppermost surface of the lower electrode,
the uppermost surface of the lower conductive region, and the
uppermost surface of the foundation layer are located at a height
of H from plane-A and the upper surface of the interlayer
insulating film within the memory cell region and the boundary
region, thereby constituting one level plane.
If another interlayer insulating film is formed above the concave
lower conductive region and the concave lower electrode,
"interlayer insulating film" as described in the claims of the
present invention denotes an insulating layer in which the
above-described foundation layer is formed. Therefore, the surface
of the insulating layer with which the above-described foundation
layer has contact corresponds to the "upper surface of the
interlayer insulating film" described in the claims. In addition,
"plane-A" denotes a plane conceived as having level equal to the
upper surface of this interlayer insulating film in the memory cell
region and the boundary region. This means that the concave lower
conductive region and the concave lower electrode protrude upwardly
by a height of H from this plane-A.
Since only one concave lower conductive region suffices in this
boundary region, it is possible to miniaturize the boundary region.
In the boundary region of the present invention, "one concave lower
conductive region" denotes a conductive region comprised of one
continuous concave structure. The shape of this lower conductive
region is not limited in particular, as long as the lower
conductive region is one continuous concave structure. Preferably,
however, the concave structure is formed so as to surround the
memory cell region in one trip therearound.
In the memory cell region and the boundary region, a dielectric
film is formed so as to cover the entire surfaces of the concave
lower electrode, the concave lower conductive region and the
foundation layer. The thickness of the dielectric film and the
diameters of the lower electrode and the lower conductive region
are adjusted so that the concave lower electrode and the concave
lower conductive region are not completely filled with the
dielectric film. In addition, the uppermost surface of the lower
electrode, the uppermost surface of the lower conductive region and
the uppermost surface of the foundation layer altogether constitute
one level plane within the memory cell region and the boundary
region, and the thickness of the dielectric film is constant. This
means that the uppermost surfaces of the dielectric film on the
upper surface of the interlayer insulating film and on plane-A
altogether constitute one level plane.
Furthermore, an upper conductive region is formed on the entire
surfaces of the memory cell region and the boundary region, so as
to have contact with the dielectric film. This upper conductive
region includes a laminated conductive layer having a predetermined
thickness and formed on the entire surface of the dielectric film
so as to have contact with the uppermost surface thereof, and a
convex portion branching off from this conductive layer and filled
into the concave lower electrode and the concave lower conductive
region covered with the dielectric film.
This laminated conductive layer is formed so as to have contact
with the uppermost surface of the dielectric film, and the
uppermost surface of this dielectric film is level across the
memory cell region and the boundary region. Consequently, in the
present invention, it is possible to level the uppermost surface of
the conductive layer of this upper conductive region in the memory
cell region and the boundary region, thereby constituting the
uppermost surface of the conductive layer as a level plane.
As described above, in the semiconductor device of the present
invention, it is possible to level the uppermost surface of the
conductive layer of the upper conductive region in the memory cell
region and the boundary region. Consequently, even if an interlayer
insulating film is formed on the entire surfaces of the memory cell
region, the boundary region and the peripheral circuit (logic
circuit) region or even if an interconnect layer is formed on this
interlayer insulating film, it is possible to eliminate step
differences among these regions and planarize the interlayer
insulating film and the interconnect layer.
When forming a foundation layer on the upper surface of the
interlayer insulating film and on plane-A in the memory cell region
and die boundary region in the course of manufacturing this
semiconductor device, the foundation layer, which functions as a
mask at the time of wet etching, is formed simultaneously also on
the interlayer insulating film of the peripheral circuit (logic
circuit) region (this interlayer insulating film is removed and is,
therefore, not present in a finished semiconductor device). In
addition, a portion of the foundation layer located upper than the
interlayer insulating film of this peripheral circuit (logic
circuit) region still remains when portions of the interlayer
insulating film in the memory cell region and the boundary region
are removed by wet etching. Since the foundation layer in this
peripheral circuit (logic circuit) region therefore serves as a
mask at the time of wet etching, there is no need to newly form a
photoresist film to serve as a mask in the peripheral circuit
(logic circuit) region. As a result, there is no need to form,
within the boundary region, a margin for alignment to be carried
out between the photoresist film and the peripheral circuit (logic
circuit) region. Thus, it is possible to miniaturize the boundary
region. As a result, foreign matter attributable to the use of the
photoresist film is not produced at the time of wet etching. Thus,
it is possible to improve a yield at the time of manufacture.
Furthermore, a mechanically high-strength foundation layer is
formed on a portion of plane-A between adjacent lower electrodes in
the memory cell region. Consequently, the lower electrodes in the
memory cell region do not collapse and the adjacent lower
electrodes do not come into contact with each other. In particular,
there arises no such a problem as the collapse of the lower
electrodes due to surface tension produced during wet etching with
the lower electrodes exposed. As a result, it is possible to
improve a yield at the time of manufacture.
2. Method for Manufacturing Semiconductor Device
In a manufacturing method, a foundation layer having a thickness of
H is formed on the entire surface of the interlayer insulating film
in one step. In another step, there is formed an opening extending
within portions of the interlayer insulating film and the
foundation layer in the memory cell region and the boundary region
in the thickness direction thereof. Then, a concave lower electrode
is formed on the inner wall of an opening in the memory cell
region, and a concave lower conductive region is formed on the
inner wall of an opening in the boundary region. Consequently, all
of the uppermost surface of the lower electrode, the uppermost
surface of the lower conductive region, and the uppermost surface
of the foundation layer on plane-A and on the interlayer insulating
film are located at a height of H upward from plane-A and the
interlayer insulating film within the memory cell region and the
boundary region, thereby constituting one level plane.
Next, isotropic etching is performed using the foundation layer,
the lower electrode and the lower conductive region as masks and
etching stoppers, thereby removing portions of the interlayer
insulating film in the memory cell region and in part of the
boundary region. At this time, a portion of the foundation layer on
the interlayer insulating film of the peripheral circuit (logic
circuit) region remains. Consequently, the foundation layer in this
peripheral circuit (logic circuit) region serves as a mask at the
time of wet etching in this step. In addition, the lower electrode
and the lower conductive region serve as etching stoppers at the
time of wet etching. Accordingly, there is no need to newly form a
photoresist film in the peripheral circuit (logic circuit) region
as a mask. In addition, the lower electrode and the lower
conductive region remain as they are without being removed by wet
etching.
As a result, there is no need to form a margin for alignment to be
carried out between the photoresist film and the peripheral circuit
(logic circuit) region within the boundary region. Thus, it is
possible to miniaturize the boundary region. Furthermore, there
arises no such a problem at the time of wet etching that the
photoresist film reacts with a dilute hydrofluoric acid (HF)
solution and changes in quality, thus producing polymer-like
foreign matter, or watermarks or the like is produced when drying a
water after wet etching. Consequently, it is possible to improve a
yield at the time of manufacture.
Next, a dielectric film having a predetermined thickness is formed
so as to cover the entire surfaces of the memory cell region, the
peripheral circuit region and the boundary region. In addition, a
conductive material is deposited on the entire surfaces of the
memory cell region, the peripheral circuit region and the boundary
region, and filled into the concave lower electrode and the concave
lower conductive region covered with the dielectric film, thereby
forming a convex portion. Concurrently with this step, a laminated
conductive layer having a predetermined thickness is formed so as
to have contact with the uppermost surface of the dielectric film.
This laminated conductive layer is formed so as to have contact
with the uppermost surface of the dielectric film, and the
uppermost surface of this dielectric film is level across the
memory cell region and the boundary region. Consequently, in the
present invention, it is possible to level the uppermost surface of
the conductive layer of this upper conductive region in the memory
cell region and the boundary region, thereby constituting the
uppermost surface of the conductive layer as a level plane.
As described above, in the semiconductor device of the present
invention, it is possible to level the uppermost surface of the
conductive layer of the upper conductive region in the memory cell
region and the boundary region. Consequently, even if an interlayer
insulating film is formed on the entire surfaces of the memory cell
region, the boundary region and the peripheral circuit (logic
circuit) region or even if an interconnect layer is formed on this
interlayer insulating film, it is possible to eliminate step
differences among these regions and planarize the interlayer
insulating film and the interconnect layer.
Furthermore, a mechanically high-strength foundation layer is
formed between adjacent lower electrodes in the memory cell region.
Consequently, the lower electrodes in the memory cell region do not
collapse and the adjacent lower electrodes do not come into contact
with each other. In particular, there arises no such a problem as
the collapse of the lower electrodes due to surface tension
produced during wet etching with the lower electrodes exposed. As a
result, it is possible to improve a yield at the time of
manufacture.
Hereinafter, the present invention will be described by referring
to exemplary embodiments. However, the present invention is not
limited to the below-described exemplary embodiments. Rather,
various modifications understandable to a person skilled in the art
may be made to the configuration and specifics of the present
invention within the technical scope thereof.
(First Exemplary Embodiment)
Semiconductor Device
Next, a semiconductor device according to a first exemplary
embodiment will be described in detail with reference to the
accompanying drawings. FIG. 1 is a vertical cross-sectional view
illustrating the semiconductor device of the first exemplary
embodiment. This semiconductor device is comprised of a memory cell
region for storing information, a peripheral circuit region for
controlling the writing/reading of information to/from this memory
cell region, and a boundary region present between the memory cell
region and the peripheral circuit region. Thus, the semiconductor
device as a whole constitutes a memory device.
First, an explanation will be made of the memory cell region and
the boundary region. In the memory cell region of FIG. 1, two gate
electrodes 4 are formed, by way of gate insulating film 3, on the
principal surface of an active region defined by isolation
insulating film 2 in the principal surface of silicon semiconductor
substrate 10. In addition, a pair of impurity-diffused regions 5
and 6 (first and second impurity-diffused regions) to serve as a
source region and a drain region are formed on one and the other
sides of gate electrode 4 within silicon semiconductor substrate
10. One select transistor (field-effect transistor) is comprised of
one gate electrode 4, one layer of gate insulating film 3, and a
pair of impurity-diffused regions 5 and 6. In FIG. 1, two select
transistors are shown within the memory cell region. In addition,
impurity-diffused region 6 (first impurity-diffused region) of the
respective select transistors is shared by the transistors as one
common impurity-diffused region. Only two select transistors
(field-effect transistors) are shown in the memory cell region of
FIG. 1. Typically however, three or more select transistors are
formed in the memory cell region.
Impurity-diffused region 6 (first impurity-diffused region) of this
select transistor is electrically connected to bit line 8 (tungsten
(W) film) formed on interlayer insulating film 21 by way of
polysilicon plug 11 a penetrating through interlayer insulating
film 21. This bit line 8 is covered with interlayer insulating film
22.
On this interlayer insulating film 22, there are laminated lower
electrode 51 made of a first titanium nitride film, dielectric film
52 made of a laminated film composed of an aluminum oxide film (3
nm-thick) and a hafnium oxide film (4 nm-thick), and upper
electrode 53 (15 nm-thick) made of a second titanium nitride film,
thereby forming a capacitor. In addition, foundation layer 36 is
formed above interlayer insulating film 22.
In the semiconductor device of FIG. 1, "interlayer insulating film"
as described in the appended claims refers to interlayer insulating
film 24 and the upper surface thereof is denoted by reference
numeral 71. Lower electrode 51 in the memory cell region is formed
so as to extend upwardly from below plane-A having level equal to
upper surface 71 of the interlayer insulating film, and protrudes
by a height of H above this plane-A. In addition, foundation layer
36 is formed on plane-A so as to have a thickness of H. Lower
conductive region 51a in the boundary region is formed upwardly
from below plane-A having level equal to upper surface 71 of the
interlayer insulating film, and protrudes by a height of H above
plane-A. Foundation layer 36 is formed on interlayer insulating
film 24 so as to have a thickness of H. In addition, another
foundation layer 36a is formed on this interlayer insulating film
24.
In the memory cell region and the boundary region, foundation
layers 36 and 36a are formed on plane-A and on interlayer
insulating film 24, and dielectric film 52 is formed so as to have
contact with these foundation layers 36 and 36a. In addition,
conductive layer 72 of upper conductive region 53 is formed so as
to have contact with uppermost surface 73 of this dielectric film
52. The upper conductive region 53 is disposed facing to the lower
electrode 51 and the lower conductive region 51a with an
intervention of the dielectric film 52 therebetween. Convex portion
74 of upper conductive region 53 is formed within lower electrode
51 and lower conductive region 51a.
Lower electrode 51 is concave and the bottom face thereof is
electrically connected to metal plug 12 by way of landing pad 81
made of a laminated film composed of a tungsten film and a tungsten
nitride film. This metal plug 12 is, in turn, electrically
connected to impurity-diffused region 5 (second impurity-diffused
region) of the select transistor by way of polysilicon plug 11
located below the metal plug. This metal plug 12 and polysilicon
plug 11 constitute a first contact plug. The lower conductive
region 51a, the dielectric film 52 and the upper conductive region
at the boundary region operates as a dummy capacitor.
In the semiconductor device of FIG. 1, one memory cell is comprised
of one field-effect transistor, one first contact plug, and one
capacitor. In the memory cell region of FIG. 1, there are shown two
memory cells. This memory cell region of FIG. 1 constitutes a DRAM
(Dynamic Random Access Memory).
Second interlayer insulating film 25 is formed on second titanium
nitride film 53 of the upper electrode. On this second interlayer
insulating film 25, there is formed second layer interconnect 61.
This upper electrode 53 and second layer interconnect 61 are
electrically connected to each other by way of connecting plug 44
(second contact plug) penetrating through interlayer insulating
film 25. The reason for connecting lower electrode 51 and
connecting plug 12 to each other by way of landing pad 81 in the
semiconductor device of FIG. 1 is to stabilize electrical
connection by enlarging a contact area between lower electrode 51
and connecting plug 12. Accordingly, landing pad 81 may not be
formed in some cases.
Next, an explanation will be made of the peripheral circuit region.
In the peripheral circuit region (logic circuit region) of FIG. 1,
a field-effect transistor for a peripheral circuit is formed in an
active region defined by isolation insulating film 2 in the
principal surface of silicon substrate 10. This field-effect
transistor includes gate electrode 4 formed on the principal
surface of the active region through gate insulating film 3. In
addition, impurity-diffused regions 7 and 7a (third and fourth
impurity-diffused regions) in a pair to serve as a source region
and a drain region are respectively formed on one and the other
sides of gate electrode 4 within silicon semiconductor substrate
10.
One impurity-diffused region 7 of this transistor is electrically
connected to second layer interconnect 61 by way of metal plugs 41,
42 and 43, first layer interconnect 8a, and local interconnect 81a.
These metal plugs 41, 42 and 43 constitute a third contact
plug.
The other impurity-diffused region 7a is electrically connected to
first layer interconnect 8b by way of metal plug 41a. First layer
interconnect 8b is, in turn, electrically connected to local
interconnect 81b by way of metal plug 42a. This first layer
interconnect 8b is also electrically connected, by way of another
metal plug, to another impurity-diffused region located in the
depth direction of the drawing. In addition, local interconnect 81b
is electrically connected by way of metal plug 43a to second layer
interconnect 61a.
There is a 1.5 .mu.m-high capacitor in the memory cell region and
foundation layer 36 made of a silicon nitride film is formed on a
portion of plane-A between adjacent lower electrodes 51. The
foundation layer 36 support the lower electrodes so that the
electrodes neither come into contact with each other nor collapse.
In addition, lower conductive region 51a made of a first titanium
nitride film is provided in the boundary region and interlayer
insulating film 24 is formed on a closer side to the peripheral
circuit region (logic circuit region) than this lower conductive
region 51a.
In the present exemplary embodiment, a dielectric film having the
same thickness as in the memory cell region, the convex portion of
the upper conductive region, the conductive layer of the upper
conductive region are formed on lower conductive region 51a of the
boundary region. In addition, a dielectric film having the same
thickness as in the memory cell region and the conductive layer of
the upper conductive region having the same thickness as in the
memory cell region are formed on the foundation layer of the
boundary region. In this way, in the semiconductor device of the
present exemplary embodiment, the dielectric film, the convex
portion of the upper conductive region and the conductive layer are
formed on the lower conductive region in the boundary region, and
the dielectric film and the conductive layer of the upper
conductive region are formed on the foundation layer, as in the
memory cell region. Consequently, it is possible to prevent step
differences from being produced in the boundary region and the
peripheral circuit region with respect to the memory cell
region.
In addition, in the peripheral circuit region, it is possible to
use the foundation layer (this foundation layer is removed in an
intermediate step and is, therefore, not illustrated in the
peripheral circuit region of FIG. 1) as a mask when removing the
interlayer insulating film at the time of wet etching.
Consequently, there is no need to newly form a photoresist film to
be used as a mask. As a result, it is possible to prevent foreign
matter attributable to wet etching from being produced. In
addition, there is no need to secure a margin for alignment between
this photoresist film and the lower conductive region. Thus, it is
possible to miniaturize the boundary region between the memory cell
region and the peripheral circuit (logic circuit) region.
Furthermore, by forming the foundation layer in a portion of
plane-A between lower electrodes, it is possible to prevent the
lower electrodes from collapsing and adjacent lower electrodes from
coming into contact with each other. As a result, it is possible to
improve a yield at the time of manufacture.
Method for Manufacturing Semiconductor Device
Next, a method for manufacturing the semiconductor memory device
illustrated in FIG. 1 will be described using FIGS. 1 to 19. First,
the principal surface of silicon substrate 10 was defined by
isolation insulating film 2. Next, gate oxide film 3, gate
electrode 4, diffusion layer regions 5, 6, 7 and 7a, polysilicon
plugs 11 and 11a, metal plugs 41 and 41a, interlayer insulating
film 21 (oxide silicon film), interlayer insulating film 31
(silicon nitride film), bit line 8, and first layer interconnects
8a and 8b were formed successively. Bit line 8 and first
interconnect layers 8a and 8b can be formed using the same
interconnect layer.
Subsequently, interlayer insulating film 22 (oxide silicon film)
was formed on bit line 8 and on first layer interconnects 8a and
8b. After this, contact holes were created within interlayer
insulating film 22. Then, in the memory cell region, a surface of
polysilicon plug 11 was exposed on the bottom face of a contact
hole. Likewise, in the peripheral circuit region (logic circuit
region), surfaces of first interconnects 8a and 8b were exposed on
the bottom faces of contact holes. Next, a titanium film, a
titanium nitride film and a tungsten film were filled into the
contact holes within the memory cell region and the peripheral
circuit region (logic circuit region). After this, portions of the
titanium film, the titanium nitride film and the tungsten film
external to the contact holes were removed using a CMP method,
thereby forming metal plugs 12, 42 and 42a.
After this, a tungsten nitride film and a tungsten film were formed
using a sputtering method, and then these films were subjected to
patterning using a photolithographic technique and a dry etching
technique. Consequently, there were formed landing pad 81 in the
memory cell region, local interconnects 81a and 81b in the
peripheral circuit region (logic circuit region), and lower layer
81c in the boundary region. FIG. 2 is a cross-sectional view
illustrating this condition, whereas FIG. 3 is a top view taken at
an edge of the memory cell region after the patterning of landing
pad 81 and lower layer 81c. The cross-section denoted by line A-B
in FIG. 3 corresponds to the cross-section denoted by line A-B in
FIG. 2.
Next, there were successively formed a silicon nitride film as
interlayer insulating film 32, a 1.5 .mu.m-thick oxide silicon film
as interlayer insulating film 24, and a 100 nm-thick silicon
nitride film as foundation layer 36 (FIG. 4). A thickness of the
interlayer insulating film is preferably in a range from 0.5 .mu.m
to 4.0 .mu.m. A thickness of the foundation layer is preferably in
a range from 50 nm to 200 nm.
Next, foundation layer 36 was processed using a photolithographic
technique and a dry etching technique, so as to comprise an opening
in a position corresponding to landing pad 81 in the memory cell
region. At this time, the processing was performed so that
foundation layer 36 remained on the entire surfaces of the boundary
region and the peripheral circuit region (logic circuit region).
FIG. 5 is a cross-sectional view illustrating this condition,
whereas FIG. 6 represents a top view taken at an edge of the memory
cell region after the patterning of foundation layer 36. The
foundation layer at the memory cell region operates as a support
layer of the lower electrode of the capacitor.
Next, after forming interlayer insulating film (oxide silicon film)
26 so as to fill the opening of foundation layer 36 (FIG. 7),
interlayer insulating film 26 on foundation layer 36 was removed
using a CMP method. FIG. 8 is a cross-sectional view illustrating
this condition, whereas FIG. 9 represents a top view taken at an
edge of the memory cell region after the chemical-mechanical
polishing of interlayer insulating film 26.
Next, cylinder hole 91 was created using a photolithographic
technique and a dry etching technique, so as to penetrate through
interlayer insulating films 24 and 32 and foundation layer 36.
Then, a surface of landing pad 81 was exposed on the bottom face of
this cylinder hole 91. In addition, one cylinder trench 91a was
created on lower layer 81c of the landing pad layer in the boundary
region concurrently with creating cylinder hole 91. FIG. 10 is a
cross-sectional view illustrating this condition, whereas FIG. 11
represents a top view taken at an edge of the memory cell region
after the creation of cylinder hole 91. Hereinafter, the foundation
layer covering the peripheral circuit region will be symbolized as
36a.
Next, first titanium nitride film 51 was grown on the entire
surface of the semiconductor device being manufactured using a CVD
method. Subsequently, portions of the titanium nitride film except
for cylinder trench 91 and to the bottom and side surfaces of
cylinder trench 91a were etched back and removed, while protecting
the titanium nitride film in the bottom of the trenches from being
etched by forming a photoresist film (not illustrated) within
cylinder trenches 91 and 91a. Next, the photoresist film was
removed using an organic separating liquid, thereby obtaining
concave lower electrode 51 in the memory cell region and concave
lower conductive region 51a in the boundary region. FIG. 12 is a
cross-sectional view illustrating this condition, whereas FIG. 13
represents a top view taken at an edge of the memory cell region
after the etching back of the titanium nitride film.
Next, interlayer insulating film (oxide silicon film) 24 in the
memory cell region and in part of the boundary region was removed
by a wet etching method using a dilute hydrofluoric acid (HF)
solution. Since wet etching proceeded isotropically at this time,
interlayer insulating films 24 were also removed, which are present
immediately below portion of foundation layer 36 in the memory cell
region and in a closer side to the memory cell region than lower
conductive region 51a in the boundary region. In addition,
foundation layers 36 and 36a functioned as masks, and concave lower
electrode 51 and concave lower conductive region 51a functioned as
etching stoppers. Consequently, portions of interlayer insulating
film (oxide silicon film) 24 remained without being removed, in a
part of the boundary region on a closer side to the peripheral
circuit region than lower conductive region 51a and in the
peripheral circuit region. The foundation layer at the memory cell
region keeps a position of the lower electrode, and prevents the
lower electrode from collapsing during the wet etching. FIG. 14 is
a cross-sectional view illustrating this condition, whereas FIG. 15
represents a top view taken at an edge of the memory cell region
after wet etching.
Next, using an ALD (Atomic Layer Deposition) method, laminated film
(dielectric film) 52 composed of an aluminum oxide film and a
hafnium oxide film was formed on the entire surface of the
semiconductor device being manufactured. Subsequently, using a CVD
method, second titanium nitride film 53 was formed on the entire
surface as an upper electrode. As a result, in the memory cell
region, there was obtained a 1.5 .mu.m-high, crown-shaped capacitor
comprised of lower electrode 51, dielectric film 52, and upper
electrode 53 (FIG. 16). A height of the capacitor is preferably in
a range from 0.5 .mu.m to 4.0 .mu.m.
After this, using a photolithographic technique and a dry etching
technique, second titanium nitride film 53, dielectric film 52, and
anti-wet etching protective film (foundation layer) 36a in the
peripheral circuit region were removed (FIG. 17). Here, the reason
for removing anti-wet etching protective film (foundation layer)
36a in the peripheral circuit region is to avoid causing a failure
of hole making when creating a contact hole in a later step of
forming metal plugs 43 and 43a.
Next, after forming interlayer insulating film (oxide silicon film)
25 on the entire surface of the semiconductor device being
manufactured, a step difference between the memory cell region and
the peripheral circuit region was eliminated (FIG. 18) using a CMP
method.
Next, after creating contact holes within the interlayer insulating
films 24, 25 and 32, a third titanium nitride film and a tungsten
film were filled into the contact holes. After this, portions of
the third titanium nitride film and the tungsten film external to
the contact holes were removed using a CMP method to form metal
plugs 43, 43a and 44 (second and third contact plugs) (FIG. 19).
Subsequently, using a sputtering method, a titanium film, an
aluminum film and a titanium nitride film were formed successively.
Next, a laminated film composed of these films was subjected to
patterning using a photolithographic technique and a dry etching
technique, thereby forming second layer interconnects 61 and 61a
(FIG. 1).
In the present exemplary embodiment, lower layer 81c, landing pad
81, lower conductive region 51a, lower electrode 51, anti-wet
etching protective film 36a in the peripheral circuit region, and
foundation layer 36 are formed simultaneously in one
photolithography step and in one dry etching step. Consequently,
the present exemplary embodiment has the advantage of being able to
eliminate step differences between the memory cell region and the
boundary region and between the memory cell region and the
peripheral circuit (logic circuit) region without increasing the
number of steps necessary in particular to alleviate a step
difference between the memory cell region and the peripheral
circuit region.
It should be noted that in the exemplary embodiment described
heretofore, alterations may be made to aspects of a manufacturing
method, an interconnect structure, and the like other than those
characteristic of the present invention.
The semiconductor device of the present invention can be used as a
memory cell or the like for a DRAM (Dynamic Random Access
Memory).
It is apparent that the present invention is not limited to the
above embodiments, but may be modified and changed without
departing from the scope and spirit of the invention.
* * * * *