U.S. patent application number 15/070231 was filed with the patent office on 2016-07-07 for self-aligned via interconnect structures.
The applicant listed for this patent is INTERNATIONAL BUSINESS MACHINES CORPORATION. Invention is credited to Benjamin C. BACKES, Brian A. COHEN, Joyeeta NAG, Carl J. RADENS.
Application Number | 20160197038 15/070231 |
Document ID | / |
Family ID | 56094969 |
Filed Date | 2016-07-07 |
United States Patent
Application |
20160197038 |
Kind Code |
A1 |
BACKES; Benjamin C. ; et
al. |
July 7, 2016 |
SELF-ALIGNED VIA INTERCONNECT STRUCTURES
Abstract
A self-aligned via interconnect structures and methods of
manufacturing thereof are disclosed. The method includes forming a
wiring structure in a dielectric material. The method further
includes forming a cap layer over a surface of the wiring structure
and the dielectric material. The method further includes forming an
opening in the cap layer to expose a portion of the wiring
structure. The method further includes selectively growing a metal
or metal-alloy via interconnect structure material on the exposed
portion of the wiring structure, through the opening in the cap
layer. The method further includes forming an upper wiring
structure in electrical contact with the metal or metal-alloy via
interconnect structure.
Inventors: |
BACKES; Benjamin C.;
(Poughkeepsie, NY) ; COHEN; Brian A.; (Beacon,
NY) ; NAG; Joyeeta; (Wappingers Falls, NY) ;
RADENS; Carl J.; (LaGrangeville, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTERNATIONAL BUSINESS MACHINES CORPORATION |
Armonk |
NY |
US |
|
|
Family ID: |
56094969 |
Appl. No.: |
15/070231 |
Filed: |
March 15, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14563554 |
Dec 8, 2014 |
|
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15070231 |
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Current U.S.
Class: |
257/751 |
Current CPC
Class: |
H01L 21/76885 20130101;
H01L 21/2885 20130101; H01L 21/76849 20130101; H01L 21/76834
20130101; H01L 23/53257 20130101; H01L 21/76846 20130101; H01L
23/53295 20130101; H01L 21/76897 20130101; H01L 21/31111 20130101;
H01L 21/76802 20130101; H01L 23/53238 20130101; H01L 23/5226
20130101; H01L 23/528 20130101; H01L 23/53209 20130101; H01L
2924/0002 20130101; H01L 2924/0002 20130101; H01L 2924/00
20130101 |
International
Class: |
H01L 23/522 20060101
H01L023/522; H01L 23/532 20060101 H01L023/532; H01L 23/528 20060101
H01L023/528 |
Claims
1. A structure comprising a self-aligned cobalt interconnect
structure between and in electrical contact with an upper wiring
layer and a lower wiring layer, the self-aligned cobalt
interconnect structure is an overgrowth of cobalt within an opening
of a dielectric cap material on the lower wiring layer.
2. The structure of claim 1, wherein the self-aligned cobalt
interconnect structure is a lateral growth on a surface of the
dielectric cap.
3. The structure of claim 1, wherein: an interface between the
self-aligned cobalt interconnect structure and the lower wiring
layer is devoid of a barrier material and a liner material; and an
interface between the self-aligned cobalt interconnect structure
and the upper wiring layer includes a barrier material and a liner
material.
4. The structure of claim 1, wherein the lower wiring layer is
formed in a dielectric layer.
5. The structure of claim 4, further comprising a barrier/liner
material formed between the dielectric layer and the lower wiring
layer.
6. The structure of claim 5, wherein the barrier liner material is
a combination of a barrier material and a liner material.
7. The structure of claim 6, wherein the barrier material is TaN or
TiN and the liner material is Ta, Ti or Co.
8. The structure of claim 6, wherein the dielectric cap material is
deposited material on the lower wiring layer and the dielectric
layer.
9. The structure of claim 8, wherein the dielectric cap material is
dielectric hard mask layer.
10. The structure of claim 9, wherein the opening in the dielectric
cap material is a slot pattern, crossing over a segment of the
lower wiring layer to expose a portion thereof.
11. The structure of claim 10, wherein the slot pattern is
orthogonal to the lower wiring layer.
12. The structure of claim 11, wherein an interlevel dielectric
material is deposited on the self-aligned cobalt interconnect
structure and the upper wiring layer is formed in a trench of the
interlevel dielectric material.
13. The structure of claim 12, wherein the trench is lined with a
barrier/liner material.
Description
FIELD OF THE INVENTION
[0001] The invention relates to semiconductor structures and, more
particularly, to self-aligned via interconnect structures and
methods of manufacturing thereof.
BACKGROUND
[0002] Scaling of semiconductor devices is becoming ever more
difficult in sub-22 nm technologies. For example, as structures
continue to scale downward, via contact resistance becomes a
performance limiting factor; that is, the via contact resistance
becomes very high, particularly in back end of the line (BEOL) via
interconnect structures.
[0003] By way of example, dual-damascene fill processes require PVD
liner/barrier deposition. Due to the line width requirements in
scaled technologies, e.g., sub 22 nm, the liner/barrier deposition
will displace the primary conductor. As the PVD liner/barrier
materials, e.g., TaN and Ta, have higher resistance than the
primary conductors, e.g., Cu, dual-damascene fill processes have
become a major contributor to increased contact resistance. This
increased contact resistance, in turn, leads to decreased
performance of the semiconductor device.
[0004] Also, as process technologies continue to shrink towards
14-nanometers (nm) and beyond, it is becoming difficult to build
self-aligned fine pitch vias with current lithography processes.
This is mainly due to the size of the underlying wiring lines,
e.g., width of the underling wiring structure, as well as current
capabilities of lithography tool optics for 32 nm and smaller
dimension technologies.
SUMMARY
[0005] In an aspect of the invention, a method includes forming a
wiring structure in a dielectric material. The method further
includes forming a cap layer over a surface of the wiring structure
and the dielectric material. The method further includes forming an
opening in the cap layer to expose a portion of the wiring
structure. The method further includes selectively growing a metal
or metal-alloy via interconnect structure material on the exposed
portion of the wiring structure, through the opening in the cap
layer. The method further includes forming an upper wiring
structure in electrical contact with the metal or metal-alloy via
interconnect structure.
[0006] In an aspect of the invention, a method includes: forming a
wiring structure within a dielectric material; forming a dielectric
masking layer over the wiring structure and the dielectric
material; forming an opening in the dielectric masking layer,
exposing a portion of the wiring structure; overfilling the opening
with metal or metal-alloy material to form a via interconnect
structure in direct electrical contact with the wiring structure;
and forming an upper wiring structure in electrical contact with
the via interconnect structure, within a trench formed in an upper
dielectric material.
[0007] In an aspect of the invention, a method includes: forming a
wiring structure in a dielectric layer; depositing a dielectric cap
layer over the wiring structure and the dielectric layer; etching
an opening in the dielectric layer, exposing a surface of the
wiring structure; forming a self-aligned via interconnect structure
in direct electrical contact with the metal material of the wiring
structure by overfilling the opening with a metal or metal-alloy
growth process; depositing an interlevel dielectric material over
the self-aligned via interconnect structure and the dielectric cap
layer; etching a trench within the interlevel dielectric material
to expose one or more surfaces of the self-aligned via interconnect
structure; depositing a barrier material and liner material over
the exposed one or more surfaces of the self-aligned via
interconnect structure and on sidewalls of the trench; and
electroplating a metal or metal-alloy material on the liner
material to complete formation of an upper wiring structure, in
electrical contact with the via interconnect structure.
[0008] In an aspect of the invention, a structure includes a
self-aligned cobalt interconnect structure between and in
electrical contact with an upper wiring layer and a lower wiring
layer. The self-aligned cobalt interconnect structure is an
overgrowth of cobalt within an opening of a dielectric cap material
on the lower wiring layer.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0009] The present invention is described in the detailed
description which follows, in reference to the noted plurality of
drawings by way of non-limiting examples of exemplary embodiments
of the present invention.
[0010] FIGS. 1, 2a and 2b-6 show structures and respective
processing steps in accordance with aspects of the present
invention; and
[0011] FIG. 7 shows an alternative structure and respective
processing steps in accordance with aspects of the present
invention.
DETAILED DESCRIPTION
[0012] The invention relates to semiconductor structures and, more
particularly, to self-aligned via interconnect structures and
methods of manufacturing thereof. More specifically, the present
invention relates to self-aligned inverted via interconnect
structures formed with selective CVD cobalt processes, which are
self-aligned to underlying metal wiring structures. In embodiments,
the self-aligned inverted via interconnect, e.g., cobalt via, is
formed between an upper copper wiring structure and a lower copper
wiring structure; although, other materials are also contemplated
for use with the wiring structures. In embodiments, the
self-aligned inverted via interconnect structure can be deposited
by a selective metal growth process formed through a via in a
dielectric cap layer formed over the upper wiring structure. In
embodiments, the selective metal growth process is a selective
cobalt growth process, which overfills the opening in the
dielectric cap layer and can even be allowed to grow laterally on
the surface of the dielectric cap layer.
[0013] In embodiments, the self-aligned inverted via interconnect
structure introduces minimal interfacial resistance to the
underlying wiring level. This is due to the fact that the
self-aligned inverted via interconnect structure does not require a
barrier material and a liner material at the interface with the
underlying wiring structure. That is, by using the self-aligned
inverted via interconnect structure, it is now possible to
eliminate the liner/barrier interface between the via and
underlying wire structure. Moreover, the self-aligned inverted via
interconnect structure does not displace any primary conductive
material in a via and, in fact, increases a contact area with an
upper wiring structure, hence reducing the interfacial resistance
with the upper wiring structure.
[0014] The self-aligned inverted via interconnect structure can be
manufactured in a number of ways using a number of different tools.
In general, though, the methodologies and tools are used to form
structures with dimensions in the micrometer and nanometer scale.
The methodologies, i.e., technologies, employed to manufacture the
optimized wires have been adopted from integrated circuit (IC)
technology. For example, the structures, e.g., self-aligned
inverted via interconnect structure, are built on wafers and are
realized in films of material patterned by photolithographic
processes on the top of a wafer. In particular, the fabrication of
the self-aligned inverted via interconnect structure uses three
basic building blocks: (i) deposition of thin films of material on
a substrate, (ii) applying a patterned mask on top of the films by
photolithographic imaging, and (iii) etching the films selectively
to the mask.
[0015] FIG. 1 shows a structure and respective processing steps in
accordance with aspects of the present invention. In particular,
FIG. 1 shows a structure 10 comprising an interlevel dielectric
layer 12. In embodiments, the interlevel dielectric layer 12 can
be, for example, an oxide material or other low-k dielectric
material. A wiring structure 14 is formed within the dielectric
layer 12 using conventional lithography, etching and deposition
processes. For example, the formation of the wiring structure 14
begins with the deposition and patterning of a resist on the
interlevel dielectric layer 12. The resist patterned by exposure to
energy (light) to form a pattern (openings), which corresponds to
the dimensions of the wiring structure 14. A reactive ion etching
(RIE) process is performed through the resist pattern to form a
trench. The resist can then be removed using conventional etchants
and/or stripping techniques, e.g., oxygen ashing.
[0016] A barrier/liner material 16' is formed within the opening.
In embodiments, the barrier/liner material 16' can be a combination
of a barrier metal or metal alloy material and a liner metal or
metal alloy material. In embodiments, the barrier/liner material
16' is deposited using either plasma vapor deposition (PVD),
chemical vapor deposition (CVD) or atomic layer deposition (ALD)
processes. The PVD process provides a dense layer of barrier/liner
material 16', thus providing significantly improved barrier
performance due to increased barrier density. Specifically,
compared to CVD or ALD processes, in PVD processes, the copper fill
will not leak into the interlevel dielectric layer thereby
preventing time-dependent dielectric breakdown TDDB. Also, due to
the increased barrier density, oxygen will not leak into the copper
fill thereby decreasing interconnect resistance and increasing via
interconnect and wiring structure lifetime.
[0017] In embodiments, the barrier material can be TaN or TiN with
the liner material being Ta or Ti, respectively, or Co. A seed
layer is deposited on the barrier/liner material 16' followed by a
deposition of wiring metal to form the wiring structure 14. By way
of example, a seed layer of copper can be deposited using a PVD
process, followed by an electroplating of copper material (both of
represented at reference numeral 16''). In embodiments, other metal
materials can also be used for the wiring structure 14.
[0018] Still referring to FIG. 1, any residual barrier/liner
material 16' and wiring material 16'' can be removed from the upper
surface of the interlevel dielectric layer 12 using a chemical
mechanical polishing (CMP) process. The CMP process will also
planarize the wiring structure 14 and the interlevel dielectric
layer 12, for subsequent processing.
[0019] FIG. 2a shows a cross sectional view of a structure and
respective processing steps in accordance with aspects of the
present invention; whereas, FIG. 2b shows a top down view of the
structure of FIG. 2a. In both of these views, a cap layer 18 is
shown deposited on the planarized surface of the wiring structure
14 and the interlevel dielectric layer 12. In FIG. 2b, the cap
layer 18 is represented in a partial transparent view to show the
underlying structures, e.g., wiring structure 14 and the interlevel
dielectric layer 12, for descriptive purposes only.
[0020] In embodiments, the cap layer 18 is a thin dielectric hard
mask layer of, e.g., SiN or SiNC; although other capping materials
are also contemplated by the present invention. The thin dielectric
hard mask layer can have a thickness of about 25 nm or less, by way
of one non-limiting illustrative example. In embodiments, the cap
layer 18 can be deposited using a conventional chemical vapor
deposition (CVD) process. An opening 20 is formed in the cap layer
18 using conventional lithography and etching processes, e.g., a
wet etching process. As shown in FIG. 2b, the opening 20 crosses
over the wiring structure 14 in order to expose a surface thereof.
In embodiments, the opening 20 can be a slot pattern, crossing over
a segment of the underlying wiring structure 14 to expose a portion
thereof for further processing. By way of further example, the slot
20 can be formed orthogonal to the underlying wiring structure 14.
In this way, subsequently formed structures, e.g., via and wiring
structure, can be self-aligned with the underlying wiring structure
14.
[0021] In FIG. 3, the exposed surface of the wiring structure 14
undergoes a cleaning process, prior to a selective CVD Co growth.
More specifically, in embodiments, the exposed surface of the
wiring structure 14 is cleaned with a hydrogen plasma process to
remove any oxide that formed on the surface of the wiring structure
14 when exposed to air, e.g., after the wet etching process. After
the cleaning process to remove oxide, a selective CVD Co growth
process overfills the opening 20, which is in direct electrical
contact with the exposed metal surface of the wiring structure 14.
The selective CVD Co growth process will overfill the opening 20,
forming a self-aligned inverted via interconnect structure 22. In
embodiments, the selective CVD Co growth will not nucleate on the
interlevel dielectric layer 12 or the cap layer 18.
[0022] By utilizing the processes described herein, it is no longer
necessary to form a barrier/liner material at the interface between
the wiring structure 14 and the self-aligned inverted via
interconnect structure 22. By not using the barrier/liner material,
the structure, e.g., self-aligned inverted via interconnect
structure 22 and underlying metal wiring structure, will exhibit
decreased contact resistance. Also, advantageously, the
self-aligned inverted via interconnect structure 22 can be used to
prevent electromigration, e.g., the transport of material caused by
the gradual movement of ions in a conductor due to the momentum
transfer between conducting electrons and diffusing metal atoms. In
fact, the self-aligned inverted via interconnect structure 22 can
prevent two types of failure modes for via interconnect structures
and wiring structures: (i) via depletion; and (ii) line depletion.
Via depletion occurs when electrons flow from a wiring line below
into the via interconnect structure above. On the other hand, line
depletion occurs when electrons flow from the via interconnect
structure down to the wiring line below.
[0023] In FIG. 4, an interlevel dielectric material 24 is deposited
on the self-aligned inverted via interconnect structure 22 and the
cap layer 18. In embodiments, the interlevel dielectric material 24
can be an oxide material deposited using a conventional CVD
process. An opening (trench) 24a is formed in the interlevel
dielectric material 24, exposing one or more surfaces of the
self-aligned inverted via interconnect structure 22. Depending on
the designed contact resistance, the opening (trench) 24a can be
formed at different depths, exposing more or less surface area of
the self-aligned inverted via interconnect structure 22 as shown
representatively in both FIG. 4 and FIG. 7, in order to adjust the
surface contact resistance between the self-aligned inverted via
interconnect structure 22 and an upper wiring structure. In
embodiments, the opening (trench) 24a is formed using conventional
lithography and etching processes, as described herein.
[0024] In FIG. 5, following the formation of the opening (trench)
24a, barrier/liner material 26 is formed on the surfaces of the
interlevel dielectric material 24, in addition to any exposed
surfaces of the self-aligned inverted via interconnect structure 22
within the opening (trench) 24a. In embodiments, the barrier/liner
material 26 can be a combination of a barrier material and a liner
material. For example, the barrier material can be TaN or TiN with
the liner material being Ta, Ti or Co, respectively. In
embodiments, the barrier/liner material 26 can be deposited on
exposed surfaces of the self-aligned inverted via interconnect
structure 22 and surfaces of the interlevel dielectric material 24
(including sidewalls of the opening (trench) 24a, using a
conventional PVD process.
[0025] In FIG. 6, an upper wiring structure 28 is formed in direct
contact with the barrier/liner material 26 and hence in electrical
contact with the self-aligned inverted via interconnect structure
22 within the opening (trench) 24a. In embodiments, the upper
wiring structure 28 is formed by a deposition of a seed layer,
followed by an electroplating process for the remaining portions of
the wiring structure 28. By way of more specific example, a seed
layer of copper is deposited using a PVD process, followed by an
electroplating of copper material (both represented at reference
numeral 28). In embodiments, other metal materials can also be used
for the upper wiring structure 28. Any residual barrier/liner
material 26 and wiring material of the wiring structure 28 can be
removed from the upper surface of the interlevel dielectric layer
24 using a chemical mechanical polishing (CMP) process. The CMP
process will also planarize the material of the wiring structure 28
and the interlevel dielectric layer 24, for subsequent
processing.
[0026] In this way, the upper wiring structure 28 is self-aligned
with the self-aligned inverted via interconnect structure 22, with
an increased contact surface area (compared to conventional
structures). This increased contact surface area will reduce the
interfacial resistance with the upper wiring structure 28 (i.e., an
inverted via-gouging approach). Also, the barrier/liner material 26
at the interface between the wiring structure 28 and the
self-aligned inverted via interconnect structure 22 will minimize
electromigration. Moreover, the surface contact areas can be
adjusted by forming a deeper opening (trench) 24a as described with
respect to FIG. 7.
[0027] FIG. 7 shows an alternative structure and respective
fabrication processes in accordance with aspects of the invention.
In FIG. 7, the self-aligned inverted via interconnect structure 22'
is shown to be overgrown, e.g., larger than the opening 20. For
example, the self-aligned inverted via interconnect structure 22'
can be formed by a lateral overgrowth of the cobalt onto edges of
the opening 20, on the cap layer 18, e.g., the cobalt overlaps onto
the cap layer 18 by "x" distance on one or both sides. In
embodiments, distance "x" can equal any overlap of the upper wiring
structure 28, thereby effectively increasing the contact area
between the self-aligned inverted via interconnect structure 22'
and the upper wiring structure 28. This increased contact surface
area, in turn, will decrease the contact resistance of the
structure.
[0028] Also, by adjusting the depth of the opening (trench) 24a, a
contact area between the wiring structure 28 and the self-aligned
inverted via interconnect structure 22 can be increased. For
example, as further shown in FIG. 7, the opening 24a can be deeper
than shown in FIG. 6, for example, to expose more surface area of
the self-aligned inverted via interconnect structure 22' (as
represented by dimension "y"). This deeper opening 24a will also
effectively increase the contact surface area between the
self-aligned inverted via interconnect structure 22' and the upper
wiring structure 28, hence decreasing the resistance of the
structure (i.e., inverted via-gouging).
[0029] The method(s) as described above is used in the fabrication
of integrated circuit chips. The resulting integrated circuit chips
can be distributed by the fabricator in raw wafer form (that is, as
a single wafer that has multiple unpackaged chips), as a bare die,
or in a packaged form. In the latter case the chip is mounted in a
single chip package (such as a plastic carrier, with leads that are
affixed to a motherboard or other higher level carrier) or in a
multichip package (such as a ceramic carrier that has either or
both surface interconnections or buried interconnections). In any
case the chip is then integrated with other chips, discrete circuit
elements, and/or other signal processing devices as part of either
(a) an intermediate product, such as a motherboard, or (b) an end
product. The end product can be any product that includes
integrated circuit chips, ranging from toys and other low-end
applications to advanced computer products having a display, a
keyboard or other input device, and a central processor.
[0030] The descriptions of the various embodiments of the present
invention have been presented for purposes of illustration, but are
not intended to be exhaustive or limited to the embodiments
disclosed. Many modifications and variations will be apparent to
those of ordinary skill in the art without departing from the scope
and spirit of the described embodiments. The terminology used
herein was chosen to best explain the principles of the
embodiments, the practical application or technical improvement
over technologies found in the marketplace, or to enable others of
ordinary skill in the art to understand the embodiments disclosed
herein.
* * * * *