U.S. patent application number 16/576236 was filed with the patent office on 2021-03-25 for interconnects having air gap spacers.
The applicant listed for this patent is International Business Machines Corporation. Invention is credited to Kenneth Chun Kuen Cheng, Joseph F. Maniscalco, Koichi Motoyama, Oscar van der Straten, Chih-Chao Yang.
Application Number | 20210090938 16/576236 |
Document ID | / |
Family ID | 1000005444608 |
Filed Date | 2021-03-25 |
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United States Patent
Application |
20210090938 |
Kind Code |
A1 |
Cheng; Kenneth Chun Kuen ;
et al. |
March 25, 2021 |
INTERCONNECTS HAVING AIR GAP SPACERS
Abstract
A method for making a semiconductor structure includes forming a
metallization layer on a substrate. The method further includes
forming a dielectric layer on the metallization layer. The method
further includes forming one or more openings in the dielectric
layer and the metallization layer exposing a top surface of the
substrate. The method further includes forming a polymer-adhering
liner layer on sidewalls of the dielectric layer in the one or more
openings. The method further includes selectively depositing a
dielectric polymer in at least a top portion of the one or more
openings and on the polymer-adhering liner layer. The dielectric
polymer seals an air gap positioned between a bottom surface of the
dielectric polymer and a top surface of the substrate.
Inventors: |
Cheng; Kenneth Chun Kuen;
(Albany, NY) ; Motoyama; Koichi; (Clifton Park,
NY) ; van der Straten; Oscar; (Guilderland Center,
NY) ; Maniscalco; Joseph F.; (Lake Katrine, NY)
; Yang; Chih-Chao; (Glenmont, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
International Business Machines Corporation |
Armonk |
NY |
US |
|
|
Family ID: |
1000005444608 |
Appl. No.: |
16/576236 |
Filed: |
September 19, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 23/53257 20130101;
H01L 23/49827 20130101; H01L 23/53214 20130101; H01L 23/49838
20130101; H01L 21/764 20130101; H01L 23/53228 20130101; H01L
21/7682 20130101; H01L 29/0649 20130101; H01L 21/76802
20130101 |
International
Class: |
H01L 21/768 20060101
H01L021/768; H01L 21/764 20060101 H01L021/764; H01L 29/06 20060101
H01L029/06; H01L 23/498 20060101 H01L023/498; H01L 23/532 20060101
H01L023/532 |
Claims
1. A method, comprising: forming a metallization layer on a
substrate; forming a dielectric layer on the metallization layer;
forming one or more first openings in the dielectric layer and
exposing a top surface of the metallization layer; forming a
polymer-adhering liner layer on sidewalls of the dielectric layer
and on the top surface of the metallization layer in the one or
more first openings; removing the dielectric layer and the
metallization layer to form one or more second openings and
exposing a top surface of the substrate; and selectively depositing
a dielectric polymer in at least a top portion of the one or more
second openings and on the polymer-adhering liner layer, wherein
the dielectric polymer seals an air gap positioned between a bottom
surface of the dielectric polymer and the top surface of the
substrate.
2. The method according to claim 1, wherein the dielectric polymer
comprises poly-p-xylylene.
3. The method according to claim 1, wherein the substrate comprises
a back-end-of-line substrate.
4. The method according to claim 1, further comprising forming an
etch stop layer on the substrate prior to forming the metallization
layer.
5. The method according to claim 1, wherein the metallization layer
comprises a conductive metal selected from the group consisting of
aluminum, ruthenium, tungsten, copper and cobalt.
6. The method according to claim 1, wherein the dielectric polymer
contains an additional air gap embedded within the dielectric
polymer.
7. The method according to claim 1, wherein the dielectric polymer
comprises an opening through a top surface of the dielectric
polymer and within a portion of the dielectric polymer.
8. The method according to claim 7, further comprising selectively
depositing a barrier layer over at least the top surface of the
dielectric polymer and fills at least an upper portion of the
opening in the dielectric polymer to form a plug and seal an
additional air gap positioned between a bottom surface of the plug
and a bottom surface of the dielectric polymer in the opening.
9. The method according to claim 8, further comprising removing the
barrier layer from the top surface of the dielectric polymer
thereby leaving the plug.
10. A method, comprising: forming a metallization layer on a
substrate; forming an etch stop layer on the metallization layer;
forming a dielectric layer on the metallization layer; forming a
hardmask on the dielectric layer; patterning and forming a
plurality of vias through the hardmask, the dielectric layer and
the etch stop layer and exposing a top surface of the metallization
layer; forming a polymer-adhering liner layer on sidewalls of the
plurality of vias; depositing a conductive metal in each of the
plurality of vias; forming a lithography material on a top surface
of the polymer-adhering liner layer and the conductive metal in the
plurality of vias and on a top surface of the hardmask disposed
between adjacent vias; forming one or more first openings by
selectively etching exposed portions of the hardmask, the
dielectric layer, the etch stop layer and the metallization layer
to expose the substrate; removing the lithography material and
selectively etching the hardmask and the dielectric layer between
the adjacent vias to form a second opening exposing the etch stop
layer; and selectively depositing a dielectric polymer in at least
a top portion of the one or more first openings and on the
polymer-adhering liner layer, wherein the dielectric polymer seals
an air gap positioned between a bottom surface of the dielectric
polymer and a top surface of the substrate.
11. The method according to claim 10, wherein the dielectric
polymer comprises poly-p-xylylene.
12. The method according to claim 10, further comprising
selectively depositing the dielectric polymer in the second
opening.
13. The method according to claim 10, wherein the dielectric
polymer contains an additional air gap embedded within the
dielectric polymer.
14. The method according to claim 12, wherein the dielectric
polymer contains an additional air gap embedded within the
dielectric polymer.
15. The method according to claim 10, wherein the dielectric
polymer comprises an opening through a top surface of the
dielectric polymer and within a portion of the dielectric
polymer.
16. The method according to claim 15, further comprising
selectively depositing a barrier layer over a top surface of the
structure and to fill at least an upper portion of the opening of
the dielectric polymer to form a plug and seal an additional air
gap positioned between a bottom surface of the plug and a bottom
surface of the dielectric polymer in the opening.
17. The method according to claim 16, further comprising removing
the barrier layer from the top surface of the structure thereby
leaving the plug.
18. The method according to claim 15, wherein the dielectric
polymer comprises poly-p-xylylene.
19. A semiconductor structure comprising: a substrate; a
metallization layer disposed on the substrate; a dielectric layer
disposed on the metallization layer; one or more openings in the
metallization layer, the one or more openings configured to expose
exposing a top surface of the substrate; a polymer-adhering liner
layer disposed on the metallization layer; and a dielectric polymer
disposed above a top portion of the one or more openings and on the
polymer-adhering liner layer, wherein the dielectric polymer seals
an air gap positioned between a bottom surface of the dielectric
polymer and the top surface of the substrate.
20. The semiconductor structure according to claim 19, wherein the
dielectric polymer comprises poly-p-xylylene.
Description
BACKGROUND
[0001] With the current trends in IC miniaturization, and
increasingly smaller critical dimensions, it is desirable in
semiconductor device technology to integrate many different
functions on a single chip. In the IC chip fabrication industry,
there are three sections referred to in a typical IC chip build:
front-end-of-line (FEOL), back-end-of-line (BEOL) and the section
that connects those two together, the middle-of-line (MOL). The
FEOL is made up of the semiconductor devices, e.g., transistors,
the BEOL is made up of interconnects and wiring, and the MOL is an
interconnect between the FEOL and BEOL that includes material to
prevent the diffusion of BEOL metals to FEOL devices.
[0002] The FEOL transistor devices are typically processed using
single crystal and poly-crystalline silicon. The BEOL interconnects
are typically made of multiple metals; the bulk of the conductor is
copper. If copper diffuses into the FEOL silicon-based devices, it
can cause shorting or alter sensitive transistor characteristics
and render the semiconductor useless. This is the reason for the
MOL connection. BEOL generally begins when the first layer of metal
is deposited on the wafer. BEOL includes contacts, insulating
layers (dielectrics), metal levels, and bonding sites for
chip-to-package connections.
SUMMARY
[0003] According to an exemplary embodiment of the present
invention, a method for fabricating a semiconductor structure
device includes forming a metallization layer on a substrate. The
method further comprises forming a dielectric layer on the
metallization layer. The method further comprises forming one or
more openings in the dielectric layer and the metallization layer
exposing a top surface of the substrate. The method further
comprises forming a polymer-adhering liner layer on sidewalls of
the dielectric layer in the one or more openings. The method
further comprises selectively depositing a dielectric polymer in at
least a top portion of the one or more openings and on the
polymer-adhering liner layer. The dielectric polymer seals an air
gap positioned between a bottom surface of the dielectric polymer
and a top surface of the substrate.
[0004] According to an exemplary embodiment of the present
invention, a method for fabricating a semiconductor structure
device includes forming a metallization layer on a substrate. The
method further comprises forming an etch stop layer on the
metallization layer. The method further comprises forming a
dielectric layer on the metallization layer. The method further
comprises forming a hardmask on the dielectric layer. The method
further comprises patterning and forming a plurality of vias
through the hardmask, the dielectric layer and the etch stop layer
exposing a top surface of the metallization layer. The method
further comprises forming a polymer-adhering liner layer on
sidewalls of the plurality of vias. The method further comprises
depositing a conductive metal in each of the plurality of vias. The
method further comprises forming a lithography material on a top
surface of the polymer-adhering liner layer and the conductive
metal in the plurality of vias and on a top surface of the hardmask
disposed between adjacent vias. The method further comprises
forming one or more first openings by selectively etching exposed
portions of the hardmask, the dielectric layer, the etch stop layer
and the metallization layer to expose the substrate. The method
further comprises removing the lithography material and selectively
etching the hardmask and the dielectric layer between the adjacent
vias to form a second opening exposing the etch stop layer. The
method further comprises selectively depositing a dielectric
polymer in at least a top portion of the one or more first openings
and on the polymer-adhering liner layer. The dielectric polymer
seals an air gap positioned between a bottom surface of the
dielectric polymer and a top surface of the substrate.
[0005] According to an exemplary embodiment of the present
invention, a semiconductor structure includes a substrate. The
semiconductor structure further comprises a metallization layer
disposed on the substrate. The semiconductor structure further
comprises a dielectric layer disposed on the metallization layer.
The semiconductor structure further comprises one or more openings
in the dielectric layer and the metallization layer exposing a top
surface of the substrate. The sidewalls of the dielectric layer in
the one or more openings have a polymer-adhering liner layer
disposed thereon. The semiconductor structure further comprises a
dielectric polymer disposed in a top portion of the one or more
openings and on the polymer-adhering liner layer. The dielectric
polymer seals an air gap positioned between a bottom surface of the
dielectric polymer and a top surface of the substrate.
[0006] These and other exemplary embodiments of the invention will
be described in or become apparent from the following detailed
description of exemplary embodiments, which is to be read in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Exemplary embodiments of the present invention will be
described below in more detail, with reference to the accompanying
drawings, of which:
[0008] FIG. 1 is a cross-sectional view illustrating a
semiconductor structure at a first-intermediate fabrication stage,
according to an illustrative embodiment.
[0009] FIG. 2 is a cross-sectional view illustrating the
semiconductor structure at a second-intermediate fabrication stage,
according to an illustrative embodiment.
[0010] FIG. 3 is a cross-sectional view illustrating the
semiconductor structure at a third-intermediate fabrication stage,
according to an illustrative embodiment.
[0011] FIG. 4 is a cross-sectional view illustrating the
semiconductor structure at a fourth-intermediate fabrication stage,
according to an illustrative embodiment.
[0012] FIG. 5 is a cross-sectional view illustrating the
semiconductor structure at a fifth-intermediate fabrication stage,
according to an illustrative embodiment.
[0013] FIG. 6 is a cross-sectional view illustrating the
semiconductor structure at a sixth-intermediate fabrication stage,
according to an illustrative embodiment.
[0014] FIG. 7 is a cross-sectional view illustrating the resulting
semiconductor structure at a seventh-intermediate fabrication
stage, according to an illustrative embodiment.
[0015] FIG. 8 is a cross-sectional view illustrating of a
semiconductor structure at a seventh-intermediate fabrication stage
starting from FIG. 6, according to an alternative illustrative
embodiment.
[0016] FIG. 9 is a cross-sectional view illustrating a
semiconductor structure at a seventh-intermediate fabrication stage
starting from FIG. 6, according to an alternative illustrative
embodiment.
[0017] FIG. 10 is a cross-sectional view illustrating the
semiconductor structure at an eighth-intermediate fabrication stage
from FIG. 9, according to an alternative illustrative
embodiment.
[0018] FIG. 11 is a cross-sectional view illustrating the resulting
semiconductor structure at a ninth-intermediate fabrication stage
from FIG. 10, according to an alternative illustrative
embodiment.
DETAILED DESCRIPTION
[0019] This disclosure relates generally to integrated circuits
(IC), and more particularly to semiconductor ICs, and methods for
their construction.
[0020] Exemplary embodiments of the invention will now be discussed
in further detail with regard to integrated circuits and a method
of manufacturing the IC, and more particularly to top-via
interconnects having an air gap using a selective deposition of a
dielectric. Interconnect structures in integrated circuits induce a
delay in the propagation of the information between semiconductor
devices such as transistors. Introducing air gaps between
laterally-spaced top-via interconnects can significantly reduce the
parasitic capacitance and the device delay caused by this parasitic
capacitance. One common way of introducing air gaps between
laterally-spaced top-via interconnects is by pinching off the space
between the top-via interconnects with a layer of non-conformal
coating. However, depositing this non-conformal pinch-off coating
will create unwanted material on the side walls of the metal
lines/vias, thereby offsetting the capacitance benefits created by
the air gap. Thus, embodiments described herein provide top-via
interconnects having an air gap that uses selectively-deposited
dielectric polymer as the pinch-off layer. This
selectively-deposited pinch off dielectric polymer will deposit on
a liner and etch stop layer over the metal conductor and pinch off
the top-via interconnect containing both metal lines and vias with
minimal dielectric deposition on the side walls of the metal
conductor, thereby minimizing any offset to the capacitance benefit
created by the air gaps due to unwanted material on metal line side
walls.
[0021] It is to be understood that the various layers, structures,
and regions shown in the accompanying drawings are schematic
illustrations that are not drawn to scale. In addition, for ease of
explanation, one or more layers, structures, and regions of a type
commonly used to form semiconductor devices or structures may not
be explicitly shown in a given drawing. This does not imply that
any layers, structures, and regions not explicitly shown are
omitted from the actual semiconductor structures.
[0022] Furthermore, it is to be understood that the embodiments
discussed herein are not limited to the particular materials,
features, and processing steps shown and described herein. In
particular, with respect to semiconductor processing steps, it is
to be emphasized that the descriptions provided herein are not
intended to encompass all of the processing steps that may be
required to form a functional semiconductor integrated circuit
device. Rather, certain processing steps that are commonly used in
forming semiconductor devices, such as, for example, wet cleaning
and annealing steps, are purposefully not described herein for
economy of description.
[0023] Moreover, the same or similar reference numbers are used
throughout the drawings to denote the same or similar features,
elements, or structures, and thus, a detailed explanation of the
same or similar features, elements, or structures will not be
repeated for each of the drawings. It is to be understood that the
terms "about" or "substantially" as used herein with regard to
thicknesses, widths, percentages, ranges, etc., are meant to denote
being close or approximate to, but not exactly. For example, the
term "about" or "substantially" as used herein implies that a small
margin of error may be present, such as 1% or less than the stated
amount.
[0024] Reference in the specification to "one embodiment" or "an
embodiment" of the present principles, as well as other variations
thereof, means that a particular feature, structure,
characteristic, and so forth described in connection with the
embodiment is included in at least one embodiment of the present
principles. Thus, the appearances of the phrase "in one embodiment"
or "in an embodiment", as well any other variations, appearing in
various places throughout the specification are not necessarily all
referring to the same embodiment. The term "positioned on" means
that a first element, such as a first structure, is present on a
second element, such as a second structure, wherein intervening
elements, such as an interface structure, e.g. interface layer, may
be present between the first element and the second element. The
term "direct contact" means that a first element, such as a first
structure, and a second element, such as a second structure, are
connected without any intermediary conducting, insulating or
semiconductor layers at the interface of the two elements.
[0025] It will be understood that, although the terms first,
second, etc. may be used herein to describe various elements, these
elements should not be limited by these terms. These terms are only
used to distinguish one element from another element. Thus, a first
element discussed below could be termed a second element without
departing from the scope of the present concept.
[0026] As used herein, "height" refers to a vertical size of an
element (e.g., a layer, trench, hole, opening, etc.) in the
cross-sectional views measured from a bottom surface to a top
surface of the element, and/or measured with respect to a surface
on which the element is located. Conversely, a "depth" refers to a
vertical size of an element (e.g., a layer, trench, hole, opening,
etc.) in the cross-sectional views measured from a top surface to a
bottom surface of the element. Terms such as "thick", "thickness",
"thin" or derivatives thereof may be used in place of "height"
where indicated.
[0027] As used herein, "width" or "length" refers to a size of an
element (e.g., a layer, trench, hole, opening, etc.) in the
drawings measured from a side surface to an opposite surface of the
element. Terms such as "thick", "thickness", "thin" or derivatives
thereof may be used in place of "width" or "length" where
indicated.
[0028] The present embodiments may include a design for an
integrated circuit chip, which may be created in a graphical
computer programming language, and stored in a computer storage
medium (such as a disk, tape, physical hard drive, or virtual hard
drive such as in a storage access network). If the designer does
not fabricate chips or the photolithographic masks used to
fabricate chips, the designer may transmit the resulting design by
physical means (e.g., by providing a copy of the storage medium
storing the design) or electronically (e.g., through the Internet)
to such entities, directly or indirectly. The stored design is then
converted into the appropriate format (e.g., GDSII) for the
fabrication of photolithographic masks, which typically include
multiple copies of the chip design in question that are to be
formed on a wafer. The photolithographic masks are utilized to
define areas of the wafer (and/or the layers thereon) to be etched
or otherwise processed.
[0029] Methods as described herein may be 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] Illustrative embodiments for forming a semiconductor device
will be described below with reference to FIGS. 1-11. Note that the
same reference numeral (100) is used to denote the semiconductor
structure through the various intermediate fabrication stages
illustrated in FIGS. 1-11. Note also that the semiconductor
structure described herein can also be considered to be a
semiconductor device and/or an integrated circuit, or some part
thereof. For the purpose of clarity, some fabrication steps leading
up to the production of the semiconductor structure as illustrated
in FIGS.1-11 are omitted. In other words, one or more well-known
processing steps which are not illustrated but are well-known to
those of ordinary skill in the art have not been included in the
figures.
[0031] For example, according to a first embodiment, FIG. 1
illustrates a schematic cross-sectional side view of a
semiconductor structure 100 for use in forming an interconnect
structure. For the purpose of clarity, fabrication steps leading up
to the production of semiconductor structure 100 as illustrated in
FIG. 1 are omitted. In other words, semiconductor structure 100
does not necessarily start out in the form illustrated in FIG. 1,
but may develop into the illustrated structure over one or more
well-known processing steps which are not illustrated but are
well-known to those of ordinary skill in the art.
[0032] As shown in FIG. 1, the semiconductor structure 100
comprises an optional metal nucleation/etch stop layer 104 disposed
on the surface of substrate 102 having devices formed therein.
Substrate 102 may be a semiconductor chip or wafer which is
prepared using conventional techniques well known in the art.
Substrate 102 may contain various interconnect regions on the
surface thereof. In one embodiment, semiconductor structure
including substrate 102 can be, for example, a back-end-of-line
(BEOL) interconnect structure which includes a metallization (M1)
level and a first via (V1) level.
[0033] As one skilled in the art will appreciate, metal
nucleation/etch stop layer 104 can be used to assist in the
deposition process of the metallization layer 106 discussed
hereinbelow when using atomic layer deposition (ALD) or chemical
vapor deposition (CVD). When using a physical vapor deposition
(PVD) to deposit the metallization layer 106, a metal
nucleation/etch stop layer is not necessary on the substrate. Metal
nucleation/etch stop layer 104 is also an etch stop layer when
etching the metallization layer into line patterns as shown in FIG.
5 in order to prevent the etching process to over etch into the
substrate.
[0034] Metal nucleation/etch stop layer 104 includes, but is not
limited to, TaN, TiN, TiO and WN. The metal nucleation/etch stop
layer 104 can be conformally deposited using known methods such as
ALD, CVD, PVD, electroplating, or electroless plating. A chemical
mechanical planarization (CMP) process can be performed to
planarize the structure surface prior to deposition of the
metallization layer 106. In general, metal nucleation/etch stop
layer 104 can have a thickness ranging from about 0.5 to about 5
nanometers (nm).
[0035] A metallization layer 106, i.e., metallization level 1, is
deposited on the substrate or optional metal nucleation/etch stop
layer 104 using a suitable deposition process, for example CVD,
ALD, PVD, plasma enhanced chemical vapor deposition (PECVD),
chemical solution deposition or other like processes. Suitable
conductive metals for metallization layer 106 are any conductive
material that can be dry etched or patterned including, for
example, aluminum (Al), chromium (Cr), hafnium (Hf), iridium (Ir),
molybdenum (Mo), niobium (Nb), osmium (Os), rhenium (Re), rhodium
(Rh), ruthenium (Ru), tantalum (Ta), titanium (Ti), tungsten (W),
vanadium (V), zirconium (Zr), and alloys thereof. In one
embodiment, metallization layer 106 is formed by one or more of Al,
Ru, Ta, Ti or W. In one embodiment, metallization layer 106 is
Ru.
[0036] Next, etch stop layer 108 is deposited on metallization
layer 106. As one skilled in the art will understand, etch stop
layer 108 will be made of a material with either a higher
resistivity or a lower resistivity than the resistivity of
metallization layer 106. Suitable materials for etch stop layer 108
include, for example, Ir, TaN, SiN, hydrogen-doped SiN, a
nitrogen-doped silicon carbide (e.g., NBloK), etc., although other
material suitable in providing etch-stop function may be used as
well. The etch stop layer 108 may be formed using known deposition
techniques, such as, for example, CVD, PVD, PECVD, ALD, or spin on
deposition, followed by a standard planarization process (e.g.,
CMP) to planarize the upper surfaces. In general, etch stop layer
108 can have a thickness ranging from about 0.5 to about 10 nm.
[0037] Dielectric layer 110, i.e., via level V1, is deposited on
etch stop layer 108. Dielectric layer 110 may be made of any known
dielectric material such as octamethylcyclotetrasiloxane (OMCTS),
SiO.sub.2, AlO.sub.x, SiN, TiN, etc. The dielectric layer 110 may
be formed by any suitable deposition technique known in the art,
including ALD, CVD, PVD, molecular beam deposition (MBD), pulsed
laser deposition (PLD), or liquid source misted chemical deposition
(LSMCD).
[0038] Hardmask 112 is deposited on dielectric layer 110. Hardmask
112, e.g., SiN, may be formed by any suitable deposition technique
known in the art, including ALD, CVD, and PVD. Next, a conventional
lithography material 114 such as a photoresist is deposited on
hardmask 112 using conventional techniques. The photoresist is then
patterned for forming vias in the V1 level as discussed
hereinbelow.
[0039] FIG. 2 illustrates the semiconductor structure 100 at a
second intermediate stage of fabrication after etching via openings
114a using the lithography material 114 as a guide. The etch may,
for example, comprise a reactive ion etch (RIE) as known to those
skilled in the art. As shown in FIG. 2, the via openings 114a are
extended through hardmask 112, dielectric layer 110 and etch stop
layer 108, exposing a top surface of metallization layer 106. The
photoresist 114 is completely removed during the etching process.
In addition, the etch stop layer 108 is removed from the via
openings 114a by known RIE or wet etching techniques as shown in
FIG. 2.
[0040] FIG. 3 illustrates the semiconductor structure 100 at a
third intermediate stage of fabrication wherein polymer-adhering
liner layer 116 is deposited in via opening 114a and on a top
surface of hardmask 112. Suitable material used for
polymer-adhering liner layer 116 can be any of those material for
metal nucleation/etch stop layer 104, for example, a nitride-based
material such as TaN, TiN and WN. The polymer-adhering liner layer
116 can be conformally deposited using known methods such as ALD,
CVD, PVD, electroplating, or electroless plating. The
polymer-adhering liner layer 116 assists in the metal deposition
process to fill the vias as discussed below, in the dielectric
polymer selective deposition process as shown in FIG. 7. In
general, polymer-adhering liner layer 116 can have a thickness
ranging from about 0.5 to about 5 nm.
[0041] FIG. 4 illustrates the semiconductor structure 100 at a
fourth intermediate stage of fabrication wherein a conductive metal
layer 118 is deposited in and fills via openings 114a using known
methods such as PVD, electroplating, or electroless plating.
Conductive metal layer 118 can be any of the metals discussed above
for metallization layer 106. In one embodiment, conductive metal
layer 118 is the same as metallization layer 106. Subsequently, any
metal overburden of conductive metal layer 118 and the horizontal
surfaces of polymer-adhering liner layer 116 are then planarized
by, for example, a planarization process such as CMP, exposing the
top surfaces of hardmask 112.
[0042] Next, semiconductor structure 100 is patterned by depositing
a conventional lithography material 120 such as a photoresist on
the top surfaces of conductive metal layer 118 and hardmask 112
disposed between adjacent vias using conventional techniques.
[0043] FIG. 5 illustrates the semiconductor structure 100 at a
fifth intermediate stage of fabrication wherein the exposed
hardmasks 112 are first removed by conventional techniques. Next,
dielectric layer 110, etch stop layer 108, metallization layer 106,
and optional metal nucleation/etch stop layer 104 are subsequently
removed using one or more directional etching processes such as
RIE. As one skilled in the art will understand, other structures
for the metallization level M1 and via level 1 not shown in this
figure are contemplated to make up the integrated circuit herein
and as shown in FIG. 7. A via (not shown) is formed following
removal of these layers.
[0044] FIG. 6 illustrates the semiconductor structure 100 at a
sixth intermediate stage of fabrication wherein lithography
material 120 is first removed from semiconductor structure 100
using conventional techniques. Next, hardmask 112 and dielectric
layer 110 are removed using a directional etching process such as
RIE to expose a top surface of etch stop layer 108 to form via
opening 121.
[0045] FIG. 7 illustrates the semiconductor structure 100 in which
the resulting structure with air gaps are formed. During this
stage, a dielectric polymer 122 is selectively deposited in and
fills via opening 121, i.e., dielectric polymer 122 is selectively
deposited on polymer-adhering liner layer 116 and etch stop layer
108 in via opening 121. In addition, dielectric polymer 122 is
selectively deposited in and fills a top portion of via opening and
on polymer-adhering liner layer 116 in the via such that air gap
124 is sealed between the bottom surface of dielectric polymer 122
and the top surface of substrate 102. Air gap 124 may be comprised
of a gas from the ambient air, or may be comprised of an inert gas,
e.g., nitrogen gas, helium, etc. The dielectric polymer 122 can be,
for example, a dielectric such as poly-p-xylylene. For example, the
air gap shown in FIG. 7, such as air gap 124, may be formed via a
single-step dielectric deposition process in which the dielectric
polymer is deposited on the liner layer.
[0046] FIG. 8 illustrates the semiconductor structure 100 at an
alternative intermediate stage of fabrication from FIG. 6 where
dielectric polymer 122 is selectively deposited in and fills via
opening 121. As discussed above, with the selective deposition of
the dielectric polymer 122 on polymer-adhering liner layer 116 in
the top portion of via (not shown), air gap 124 is sealed between
the bottom surface of dielectric polymer 122 and the top surface of
substrate 102. In this embodiment, an additional air gap 126 is
formed by being embedded within dielectric polymer 122 when the
polymer deposition rate is uneven. Thus, the dielectric polymer
will have a greater deposition near the top portion of via opening
121, causing the dielectric polymer in the top portion of via
opening 121 to seal off completely and form an air gap within the
dielectric polymer.
[0047] FIGS. 9-11 illustrate the semiconductor structure 100 at
another alternative intermediate stage of fabrication from FIG. 6.
Referring to FIG. 9, dielectric polymer 122 is selectively
deposited in and fills via opening 121. Also as discussed above,
with the selective deposition of the dielectric polymer 122 on
polymer-adhering liner layer 116 in the via (not shown), air gap
124 is sealed between the bottom surface of dielectric polymer 122
and the top surface of substrate 102. In this embodiment, an
additional air gap 128 is formed in dielectric polymer 122 and
having an opening at the top of air gap 128 when the polymer
deposition rate is uneven. Thus, the dielectric polymer 122 will
have a greater deposition near the top portion of each of the vias
thereby resulting in the dielectric polymer 122 in the top portion
of each of the vias to form an air gap within the dielectric
polymer 122 and leave an opening at the top of the air gap.
[0048] FIG. 10 illustrates the semiconductor structure 100 at an
intermediate stage of fabrication wherein barrier layer 130 is
deposited on a top surface of semiconductor structure 100 and in a
portion of air gap 128, i.e., to fill at least an upper portion of
the opening of the dielectric polymer to form a plug and seal an
additional air gap positioned between a bottom surface of the plug
and a bottom surface of the dielectric polymer in the opening. In
one embodiment, barrier layer 130 is deposited on a top surface of
semiconductor structure 100 and fills air gap 128. Suitable
material for barrier layer 130 includes, for example, a
nitrogen-doped silicon carbide (e.g., NBlok), OMCTS, SiO.sub.2,
AlO.sub.x, SiN, SiC, etc. The barrier layer 130 can be conformally
deposited using known methods such as ALD, CVD, PVD,
electroplating, or electroless plating.
[0049] FIG. 11 illustrates the semiconductor structure 100 at
another intermediate stage of fabrication wherein barrier layer 130
is removed from the top surface of semiconductor structure 100
leaving barrier layer 130 in at least a portion of air gap 128 and
plug the opening. A CMP process is performed to remove the
overburden of barrier layer 130, and to planarize the structure
surface.
[0050] Although illustrative embodiments have been described herein
with reference to the accompanying drawings, it is to be understood
that the invention is not limited to those precise embodiments, and
that various other changes and modifications may be made by one
skilled in art without departing from the scope or spirit of the
invention.
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