U.S. patent application number 15/834151 was filed with the patent office on 2019-06-13 for interconnects with cuts formed by block patterning.
The applicant listed for this patent is GLOBALFOUNDRIES Inc.. Invention is credited to Rui Chen, Yuping Ren, Minghao Tang.
Application Number | 20190181040 15/834151 |
Document ID | / |
Family ID | 66697275 |
Filed Date | 2019-06-13 |
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United States Patent
Application |
20190181040 |
Kind Code |
A1 |
Tang; Minghao ; et
al. |
June 13, 2019 |
INTERCONNECTS WITH CUTS FORMED BY BLOCK PATTERNING
Abstract
Methods of fabricating an interconnect structure. A first
sacrificial layer is deposited over a dielectric layer, and a block
mask is formed that covers an area on the first sacrificial layer.
A second sacrificial layer is deposited over the block mask and the
first sacrificial layer. After the block mask is formed, the second
sacrificial layer is patterned to form a mandrel that is arranged
in part on a portion of the block mask.
Inventors: |
Tang; Minghao; (Ballston
Lake, NY) ; Chen; Rui; (Clifton Park, NY) ;
Ren; Yuping; (Clifton Park, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GLOBALFOUNDRIES Inc. |
Grand Cayman |
|
KY |
|
|
Family ID: |
66697275 |
Appl. No.: |
15/834151 |
Filed: |
December 7, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/0332 20130101;
H01L 21/76816 20130101; H01L 21/0335 20130101; H01L 21/76877
20130101; H01L 21/0338 20130101; H01L 21/0337 20130101 |
International
Class: |
H01L 21/768 20060101
H01L021/768; H01L 21/033 20060101 H01L021/033 |
Claims
1. A method comprising: depositing a first sacrificial layer over a
dielectric layer; forming a first block mask that covers an area on
the first sacrificial layer; depositing a second sacrificial layer
over the first block mask and the first sacrificial layer; and
after the first block mask is formed, patterning the second
sacrificial layer to form a first mandrel that is arranged in part
on a first portion of the first block mask, wherein the first
sacrificial layer is deposited on a third sacrificial layer
arranged between the first sacrificial layer and the dielectric
layer, and further comprising: before depositing the first
sacrificial layer, forming a second block mask covering an area on
the third sacrificial layer.
2. (canceled)
3. The method of claim 1 wherein a second mandrel is formed when
the second sacrificial layer is patterned, and further comprising:
forming a first sidewall spacer on the first mandrel and a second
sidewall spacer on the second mandrel to define a non-mandrel line
as a space between the first sidewall spacer and the second
sidewall spacer.
4. The method of claim 3 further comprising: etching the second
sacrificial layer with a first etching process to vertically
transfer the non-mandrel line from the second sacrificial layer to
the first sacrificial layer and form a non-mandrel line in the
first sacrificial layer, wherein the non-mandrel line in the first
sacrificial layer is arranged on a portion of the second block
mask, and the second sacrificial layer is etched selective to the
second block mask, the first sidewall spacer, and the second
sidewall spacer.
5. The method of claim 4 further comprising: etching the third
sacrificial layer with a second etching process to vertically
transfer the non-mandrel line from the first sacrificial layer to
the third sacrificial layer and form a non-mandrel line in the
third sacrificial layer, wherein the second block mask preserves an
underlying section of the third sacrificial layer when the third
sacrificial layer is etched by the second etching process.
6. The method of claim 5 further comprising: etching the dielectric
layer with a third etching process to vertically transfer the
non-mandrel line from the third sacrificial layer to the dielectric
layer as a first trench and a second trench, and to transfer the
section of the third sacrificial layer as a cut arranged between an
end of the first trench and an end of the second trench.
7. The method of claim 4 wherein the first block mask includes a
second portion exposed by the non-mandrel line, and further
comprising: before etching the second sacrificial layer, trimming
the second portion of the first block mask with a second etching
process.
8. The method of claim 4 wherein the first mandrel and the second
mandrel are removed selective to the first block mask to form a
first mandrel line and a second mandrel line when the second
sacrificial layer is etched with the first etching process, and the
first portion of the first block mask is exposed when the first
mandrel is removed.
9. The method of claim 8 further comprising: etching the first
sacrificial layer with a second etching process to transfer the
first mandrel line and the second mandrel line to the first
sacrificial layer, wherein the first block mask preserves an
underlying section of the first sacrificial layer when the first
sacrificial layer is etched.
10. The method of claim 9 further comprising: etching the third
sacrificial layer with a third etching process to vertically
transfer the first mandrel line and the second mandrel line from
the first sacrificial layer to the third sacrificial layer and form
a first mandrel line and a second mandrel line in the third
sacrificial layer, wherein the section of the first sacrificial
layer preserves an underlying section of the third sacrificial
layer when the third sacrificial layer is etched by the third
etching process.
11. The method of claim 10 further comprising: etching the
dielectric layer to vertically transfer the first mandrel line from
the third sacrificial layer to the dielectric layer as a first
trench and a second trench, and to transfer the section of the
third sacrificial layer as a cut arranged between an end of the
first trench and an end of the second trench.
12. The method of claim 9 further comprising: filling the
non-mandrel line in the first sacrificial layer with a hardmask
before the first sacrificial layer is etched with the second
etching process.
13. The method of claim 8 wherein a first etch stop layer is formed
on the first sacrificial layer before the first block mask is
formed, and patterning the second sacrificial layer to form the
first mandrel comprises: etching the second sacrificial layer
selective to the first etch stop layer.
14. The method of claim 13 wherein a second etch stop layer is
formed on the third sacrificial layer before the second block mask
is formed, and the first etching process etches the second
sacrificial layer selective to the second etch stop layer when
forming the non-mandrel line in the first sacrificial layer.
15. The method of claim 1 wherein the second sacrificial layer is
patterned by an etching process that removes the first sacrificial
layer selective to the first block mask.
16. The method of claim 15 wherein an etch stop layer is formed on
the first sacrificial layer before the first block mask is formed,
and the etching process used to pattern the second sacrificial
layer removes the first sacrificial layer selective to the etch
stop layer.
17. The method of claim 16 wherein the first sacrificial layer and
the second sacrificial layer are composed of amorphous silicon, the
first block mask is composed of aluminum oxide, and the etch stop
layer is composed of silicon dioxide.
18. The method of claim 1 wherein patterning the second sacrificial
layer to form the first mandrel comprises: etching the second
sacrificial layer selective to the first block mask.
19. The method of claim 18 further comprising: after the second
sacrificial layer is etched, forming a sidewall spacer on a second
portion of the first block mask adjacent to the first portion of
the first block mask and the first mandrel.
20. The method of claim 18 wherein an etch stop layer is formed on
the first sacrificial layer before the first block mask is formed,
and the second sacrificial layer is etched selective to the etch
stop layer when patterning the second sacrificial layer to form the
first mandrel.
Description
BACKGROUND
[0001] The present invention relates to integrated circuits and
semiconductor device fabrication and, more specifically, to
interconnect structures and methods of fabricating an interconnect
structure.
[0002] A back-end-of-line (BEOL) interconnect structure may be used
to connect device structures, which are fabricated on a substrate
by front-end-of-line (FEOL) processing, with each other and with
the environment external to the chip. Self-aligned patterning
processes used to form a BEOL interconnect structure involve
mandrels as sacrificial features that establish a feature pitch.
Spacers, which have a thickness that is less than a dimension
permitted by the current ground rules for optical lithography, are
formed adjacent to the vertical sidewalls of the mandrels. After
selective removal of the mandrels, the spacers are used as an etch
mask to etch an underlying hardmask to define mandrel lines over
areas from which the mandrels are removed and non-mandrel lines
over areas between the spacers. The pattern of mandrel and
non-mandrel lines is transferred from the hardmask to an interlayer
dielectric layer as trenches in which the wires of the BEOL
interconnect structure are formed.
[0003] Cuts may be formed in mandrels with a cut mask and etching
in order to section the mandrels before the spacers are formed and
to define gaps in the cut mandrels. Non-mandrel cuts may also be
formed in the hardmask itself and define gaps that are filled by
dielectric material when the spacers are formed. The gaps may be
subsequently used to produce wires in the patterned interlayer
dielectric layer that are spaced apart at their tips with a
tip-to-tip spacing based on the dimensions of the cuts.
[0004] Improved interconnect structures and methods of fabricating
an interconnect structure are needed.
SUMMARY
[0005] In an embodiment of the invention, a method includes
depositing a first sacrificial layer over a dielectric layer,
forming a block mask covering an area on the first sacrificial
layer, and depositing a second sacrificial layer over the block
mask and the first sacrificial layer. After the block mask is
formed, the second sacrificial layer is patterned to form a mandrel
that is arranged in part on a portion of the block mask.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate various
embodiments of the invention and, together with a general
description of the invention given above and the detailed
description of the embodiments given below, serve to explain the
embodiments of the invention.
[0007] FIGS. 1-11 are cross-sectional views of a structure at
successive stages of a processing method in accordance with
embodiments of the invention.
[0008] FIG. 1A is a diagrammatic top view of FIG. 1 in which the
dimensions and relative locations of the block masks are
illustrated.
[0009] FIG. 11A is a diagrammatic top view in which FIG. 11 is
taken generally along line 11-11.
DETAILED DESCRIPTION
[0010] With reference to FIGS. 1, 1A and in accordance with
embodiments of the invention, an interlayer dielectric layer 10 may
be comprised of an electrically-insulating dielectric material,
such as hydrogen-enriched silicon oxycarbide (SiCOH) or another
type of low-k dielectric material, deposited by chemical vapor
deposition (CVD). The interlayer dielectric layer 10 may be located
on a substrate that includes device structures fabricated by
front-end-of-line (FEOL) processing to form an integrated circuit.
A hardmask 12 is located on the top surface of the interlayer
dielectric layer 10. The hardmask 12 may be comprised of a metal,
such as titanium nitride (TiN), deposited by physical vapor
deposition (PVD) and/or a dielectric material, such as silicon
nitride (Si.sub.3N.sub.4), deposited by chemical vapor deposition
(CVD). The hardmask 12 is removable from the interlayer dielectric
layer 10 selective to the material of the interlayer dielectric
layer 10. As used herein, the term "selective" in reference to a
material removal process (e.g., etching) denotes that the material
removal rate (i.e., etch rate) for the targeted material is higher
than the material removal rate (i.e., etch rate) for at least
another material exposed to the material removal process.
[0011] A layer stack that includes sacrificial layers 14, 16, 18
and etch stop layers 20, 22 is formed on a top surface of the
hardmask 12. Block masks 24, 26, 28, 30 are formed at strategic
locations in the layer stack and are subsequently used in the
process flow to form mandrel cuts and non-mandrel cuts. The
sacrificial layers 14, 16, 18 may be composed of a sacrificial
material, such as amorphous silicon (.alpha.-Si), deposited by, for
example, chemical vapor deposition (CVD). The etch stop layers 20,
22 may be composed of a dielectric material, such as silicon
dioxide (SiO.sub.2), deposited by, for example, chemical vapor
deposition (CVD) or atomic layer deposition (ALD). The block masks
24, 26, 28, 30 may be composed of a dielectric material, such as
aluminum dioxide (Al.sub.2O.sub.3), deposited by, for example,
atomic layer deposition (ALD). The layer stack materials are
selected to have a high etch selectivity relative to each other.
For example, the etch selectivity of aluminum dioxide to silicon
and to silicon dioxide is, respectively, 7:1 and 10:1, the etch
selectivity of silicon to aluminum dioxide and to silicon dioxide
is, respectively, 50:1 and 100:1, and the etch selectivity of
silicon dioxide to aluminum dioxide and to silicon is,
respectively, 50:1 and 10:1.
[0012] The etch stop layer 20 and sacrificial layer 14 are serially
deposited on the hardmask 12. The block masks 24, 26 are formed by
depositing a layer of their constituent material on the etch stop
layer 20 and patterning the deposited layer with lithographic and
etching processes to form the block masks 24, 26 as patterned
features. The etch stop layer 22 and sacrificial layer 16 are
serially deposited on the etch stop layer 20. The block masks 24,
26 are arranged between the sacrificial layer 16 and the etch stop
layer 20, and are thinner than the sacrificial layer 16. The block
masks 28, 30 are formed by depositing a layer of their constituent
material on etch stop layer 22 and patterning the deposited layer
with lithographic and etching processes to form the block masks 28,
30 as patterned features. The sacrificial layer 18 is then
deposited on the etch stop layer 22. The block masks 28, 30 are
arranged between the sacrificial layer 18 and the etch stop layer
22, and are thinner than the sacrificial layer 18. In vertical
projection, the block mask 28 and the block mask 30 are positioned
to partially overlap so as to provide, as part of the subsequent
process flow, respective cuts in mandrel and non-mandrel spaces
that are adjacent in position.
[0013] With reference to FIG. 2 in which like reference numerals
refer to like features in FIG. 1 and at a subsequent fabrication
stage of the processing method, mandrels 32 are formed from the
sacrificial layer 18 on a top surface of the etch stop layer 22 and
the block masks 28, 30 to provide overlapping relationships. For
example, a sidewall image transfer (SIT) process or a self-aligned
double patterning (SADP) process may be used to pattern the
mandrels 32. The layout of the mandrels 32 is selected in
coordination with the locations of the block masks 24, 26 and the
block masks 28, 30.
[0014] A conformal layer 34 comprised of a dielectric material may
be deposited using, for example, atomic layer deposition (ALD) over
the mandrels 32 and the etch stop layer 22. The material
constituting the conformal layer 34 may be chosen so as to be
removed by a given etch chemistry selective to the material of the
mandrels 32. For example, if the mandrels 32 are composed of
amorphous silicon, the dielectric material constituting the
conformal layer 34 may be composed of silicon dioxide (SiO.sub.2)
such that the mandrels 32 can be pulled or removed without removing
sidewall spacers formed using the conformal layer 34.
[0015] With reference to FIG. 3 in which like reference numerals
refer to like features in FIG. 2 and at a subsequent fabrication
stage of the processing method, sidewall spacers 36 are formed from
the conformal layer 34 at locations adjacent to the vertical
sidewalls of the mandrels 32. The sidewall spacers 36 may be formed
by shaping the conformal layer 34 with an anisotropic etching
process, such as reactive ion etching (RIE), that removes the
material of the conformal layer 34 selective to the materials of
the mandrels 32 and block masks 28, 30. Non-mandrel spaces 38 are
defined between the groups of mandrels 32 and sidewall spacers 36.
Sections of the material of the etch stop layer 22 may also be
removed from the sacrificial layer 16 with an anisotropic etching
process, such as reactive ion etching (ME), in the non-mandrel
spaces 38. In an embodiment, the anisotropic etching process used
to form the sidewall spacers 36 may also remove the sections of the
etch stop layer 22 from these unmasked areas in the non-mandrel
spaces 38. Areas of the block masks 28, 30 in the non-mandrel
spaces 38 are exposed at the edges of the overlying sidewall
spacers 36 by the etching of the conformal layer 34.
[0016] One of the mandrels 32 has a section along its length that
is aligned with, and longitudinally crosses over, the block mask
28. The extent of the overlap is equal to the length of the block
mask 28. The subsequent effect in the process flow is a cut in a
mandrel space at the location of the block mask 28. Another of the
mandrels 32 has a section along its length that is aligned with,
and longitudinally crosses over, the block mask 30. The extent of
the overlap is equal to the length of the block mask 30. The
subsequent effect in the process flow is another cut in a different
mandrel space at the location of the block mask 30. Similarly, one
of the non-mandrel spaces 38 has a section along its length that is
aligned with, and longitudinally crosses over (i.e., overlaps), the
block mask 24. The extent of the overlap is equal to the length of
the block mask 24. The subsequent effect in the process flow is a
cut in this non-mandrel space 38 at the location of the block mask
24. Another of the non-mandrel spaces 38 has a section along its
length that is aligned with, and longitudinally crosses over (i.e.,
overlaps), the block mask 26. The extent of the overlap is equal to
the length of the block mask 26. The subsequent effect in the
process flow is another cut in this different non-mandrel space 38
at the location of the block mask 26. The block masks 24, 26 and
the block masks 28, 30 are provided in the as-deposited layer stack
before the mandrels 32 and sidewall spacers 36 are formed, which
differs from conventional process flows.
[0017] With reference to FIG. 4 in which like reference numerals
refer to like features in FIG. 3 and at a subsequent fabrication
stage of the processing method, an anisotropic etching process,
such as reactive ion etching (RIE), of suitable etch chemistry is
used to trim the exposed portions of the block masks 28, 30 in the
non-mandrel spaces 38. Areas of the etch stop layer 22 in the
non-mandrel spaces 38 are exposed when the exposed portions of the
block masks 28, 30 are trimmed. An anisotropic etching process,
such as reactive ion etching (ME), of suitable etch chemistry is
used to remove these exposed areas of the etch stop layer 22. These
etches adjust the dimensions of the block masks 28, 30 in a
self-aligned manner such that their respective width dimensions are
reduced and such that the non-mandrel spaces 38 are no longer
partially covered by the block masks 28, 30. The length dimensions
of the block masks 28, 30 parallel to the length dimensions of the
non-mandrel spaces 38 are unchanged.
[0018] With reference to FIG. 5 in which like reference numerals
refer to like features in FIG. 4 and at a subsequent fabrication
stage of the processing method, the mandrels 32 are pulled and
removed selective to the sidewall spacers 36 and etch stop layer 22
with an etching process having a suitable etch chemistry. The
etching process removing the mandrels 32 stops on the etch stop
layer 22 without penetrating through the etch stop layer 22 and
into the underlying sacrificial layer 16 at the locations of the
removed mandrels 32. The removal of the mandrels 32 generates
mandrel spaces 40. The mandrel spaces 40 and the non-mandrel spaces
38 are arranged as parallel lines in one direction and alternate
with each other in an orthogonal direction. The etching process is
also selective to the block masks 24, 26 and the block masks 28, 30
such that they are not etched. The block mask 28 interrupts and
cuts one of the mandrel spaces 40, and the block mask 30 similarly
interrupts and cuts another of the mandrel spaces 40. The length
dimension of the block masks 28, 30 determines the length dimension
of the cuts in the mandrel spaces 40.
[0019] The sacrificial layer 16, which is composed of the same
material as the mandrels 32, is also patterned by the etching
process to form sections 42 composed of its sacrificial material.
Sections of the sacrificial layer 16 are removed from areas that
are not covered by the sidewall spacers 36 and the etch stop layer
22 in the non-mandrel spaces 38, which extends the non-mandrel
spaces 38 through the sacrificial layer 16 to the etch stop layer
20. Adjacent sections 42 of the sacrificial layer 16 are separated
from each other by one of the extended non-mandrel spaces 38. Each
of the sections 42 is aligned with one of the mandrel spaces 40.
The block mask 24 interrupts and cuts one of the non-mandrel spaces
38, and the block mask 26 similarly interrupts and cuts another of
the non-mandrel spaces 38.
[0020] With reference to FIG. 6 in which like reference numerals
refer to like features in FIG. 5 and at a subsequent fabrication
stage of the processing method, an etch mask 44 is formed by
applying an organic dielectric layer (ODL) with spin-coating and
recessing the applied ODL with reactive ion etching to provide
access from above to the sections 42 of the sacrificial layer 16
between the sidewall spacers 36. The etch stop layer 22 aligned
with and exposed by the mandrel spaces 40 is removed from the
sections 42 with an anisotropic etching process, such as reactive
ion etching (RIE), selective to the materials of the etch mask 44,
the sacrificial layer 16, and block masks 28, 30.
[0021] The mandrel spaces 40 are extended vertically into and
completely through the sections 42 of the sacrificial layer 16 by
an etching process. The etching process extending the mandrel
spaces 40 stops on the etch stop layer 20 without penetrating into
the underlying sacrificial layer 14 at the locations of the
extended mandrel spaces 40. Areas of the of the block masks 24, 26
are exposed on the sacrificial layer 14 in the extended mandrel
spaces 40. The mandrel spaces 40 are not extended into portions of
the sections 42 covered by the block masks 28, 30, which remain
intact and subsequently define mandrel cuts.
[0022] With reference to FIG. 7 in which like reference numerals
refer to like features in FIG. 6 and at a subsequent fabrication
stage of the processing method, an anisotropic etching process,
such as reactive ion etching (RIE), of suitable etch chemistry is
used to trim the exposed portions of the block masks 24, 26 inside
the mandrel spaces 40. The etch mask 44 protects the areas of the
block masks 24, 26 inside the non-mandrel spaces 38. These etches
adjust the dimensions of the block masks 24, 26 in a self-aligned
manner such that their respective width dimensions are reduced and
such that the mandrel spaces 40 adjacent to the block masks 24, 26
are no longer partially covered by the block masks 24, 26. The
length dimensions of the block masks 24, 26 are unchanged. Portions
of the block masks 28, 30 exposed by the mandrel spaces 40 are
removed by the etching process when the block mask 24, 26 are
trimmed.
[0023] With reference to FIG. 8 in which like reference numerals
refer to like features in FIG. 7 and at a subsequent fabrication
stage of the processing method, the etch mask 44 is stripped to
open the non-mandrel spaces 38. An etch mask 46 may be formed by
applying an organic dielectric layer (ODL) with spin-coating and
recessing the applied ODL with reactive ion etching to expose the
sidewall spacers 36. The sidewall spacers 36, etch stop layer 22,
and block masks 28, 30 are sequentially removed with etching
process of suitable chemistries selective to the materials of the
etch mask 46 and sacrificial layer 16. In an embodiment, the
sidewall spacers 36, etch stop layer 22, and block masks 28, 30 may
not be removed, in which instance the etch mask 46 is not
formed.
[0024] With reference to FIG. 9 in which like reference numerals
refer to like features in FIG. 8 and at a subsequent fabrication
stage of the processing method, the etch mask 46 is stripped to
open the non-mandrel spaces 38 and the mandrel spaces 40. The
unmasked sections of the etch stop layer 20 that are not covered by
the sections 42 of the sacrificial layer 16 and the remainder of
the etch stop layer 22 are removed with an etching process of a
suitable chemistry selective to the materials of the sections 42 of
sacrificial layer 16, the sacrificial layer 14, and the block masks
24, 26.
[0025] With reference to FIG. 10 in which like reference numerals
refer to like features in FIG. 9 and at a subsequent fabrication
stage of the processing method, the sacrificial layer 14 is etched
using an etching process and an etch mask that includes the
sections 42 of the sacrificial layer 16 and the block masks 24, 26.
The sections 42 of the sacrificial layer 16 are removed by the
etching process, which is selective to the materials of the
hardmask 12, the etch stop layer 20, and the block masks 24, 26.
The patterned sacrificial layer 14 includes sections that are
arranged as spaced-apart parallel lines separated by either one of
the non-mandrel spaces 38 or one of the mandrel spaces 40.
[0026] A cut mask 48 is formed as one of the sections of the
patterned sacrificial layer 14 that is masked and protected by the
trimmed block mask 24 during the etching process. The cut mask 48
interrupts the continuity of one of the non-mandrel spaces 38. The
cut mask 48 subsequently provides a cut between a pair of
linearly-arranged metal lines that is to be formed in the
interlayer dielectric layer 10 using the associated non-mandrel
space 38. The dimension of the cut mask 48 in a direction parallel
to the length of the associated non-mandrel space 38 determines a
tip-to-tip space or distance between the ends of linearly-aligned
and subsequently-formed metal lines with ends or tips terminating
at the cut and on opposite sides of the cut provided by the cut
mask 48.
[0027] A cut mask 50 is formed as one of the sections of the
patterned sacrificial layer 14 that is masked and protected during
the etching process by the section 42 of the sacrificial layer 14
formerly coinciding with the area and location of the trimmed block
mask 30. The cut mask 50 interrupts the continuity of one of the
mandrel spaces 40. The cut mask 50 subsequently provides a cut
between a pair of linearly-arranged metal lines subsequently formed
in the interlayer dielectric layer 10 using the associated mandrel
space 40. The dimension of the cut mask 50 in a direction parallel
to the length of the associated mandrel space 40 determines a
tip-to-tip space or distance between the ends of linearly-aligned
and subsequently-formed metal lines terminating at the cut and on
opposite sides of the cut provided by the cut mask 50.
[0028] A cut mask 52 is formed as one of the sections of the
patterned sacrificial layer 14 that is masked and protected during
the etching process by a combination of the block mask 26 and the
section 42 of the sacrificial layer 14 formerly coinciding with the
area and location of the trimmed block mask 28. The cut mask 52
interrupts the continuity of one of the non-mandrel spaces 38 and
also interrupts the continuity of one of the mandrel spaces 40. The
cut mask 52 subsequently provides a cut between a pair of
linearly-arranged metal lines subsequently formed in the interlayer
dielectric layer 10 using the associated non-mandrel space 38 and
between a pair of linearly-arranged metal lines subsequently formed
in the interlayer dielectric layer 10 using the associated mandrel
space 40. The dimension of the cut mask 52 in a direction parallel
to the length of the associated non-mandrel space 38 and the
associated mandrel space 40 determines a tip-to-tip space or
distance between the ends of the metal lines terminating at the cut
and on opposite sides of the cut provided by the cut mask 52. The
tip-to-tip distances are equal due to the shared length dimension
of the cut mask 52.
[0029] With reference to FIGS. 11, 11A in which like reference
numerals refer to like features in FIG. 10 and at a subsequent
fabrication stage of the processing method, the hardmask 12 is
patterned by an etching process with the patterned sacrificial
layer 14 operating as an etch mask to transfer the pattern of
non-mandrel spaces 38 and mandrel spaces 40, as well as the cut
masks 48, 50, 52 in the pattern, to the hardmask 12. The
sacrificial layer 14 may be stripped after the pattern is
transferred. The interlayer dielectric layer 10 is then patterned
by an etching process with the patterned hardmask 12 operating as
an etch mask to transfer the pattern of non-mandrel spaces 38 and
mandrel spaces 40 to the interlayer dielectric layer 10 as trenches
54.
[0030] A back-end-of-line (BEOL) interconnect structure 60 is
formed by filling the trenches 54 in the interlayer dielectric
layer 10 with a conductor to form non-mandrel wires 56 and mandrel
wires 58 as features embedded in the interlayer dielectric layer
10. A liner (not shown) comprised of titanium (Ti), titanium
nitride (TiN), tantalum (Ta), tantalum nitride (TaN), or a layered
combination of these materials (e.g., a bilayer of TaN/Ta) may be
applied to the trenches 54 before filling with a primary electrical
conductor. The primary conductor may be comprised of a
low-resistivity metal formed using a deposition process, such as
copper (Cu) or cobalt (Co) deposited by electroplating or
electroless deposition. The shapes and geometries of the wires 56,
58 reflect the areas exposed for trench formation in the interlayer
dielectric layer 10 by the patterned hardmask 12. In an embodiment,
the wires may be conductive features located in a first
metallization (MO) level that is the closest of multiple
metallization levels of the BEOL interconnect structure 60 to FEOL
device structures, and in which wires 56, 58 may be connected with
FEOL device structures by vertical contacts in a contact (CA)
level.
[0031] The cut mask 48 in the hardmask pattern is transferred to
the interlayer dielectric layer 10 as a cut 49 between
linearly-aligned non-mandrel wires 56 defining an area over which
the interlayer dielectric layer 10 is not etched and remains
intact. The non-mandrel wires 56 have a tip-to-tip spacing between
their respective ends, which are broken by the insertion of the
dielectric material of the interlayer dielectric layer 10 in the
cut 49, given by a length dimension of the cut 49 parallel to the
length, L, of the wires 56. The cut mask 50 in the hardmask pattern
is transferred to the interlayer dielectric layer 10 as a cut 51
between linearly-aligned mandrel wires 58 defining an area over
which the interlayer dielectric layer 10 is not etched and remains
intact. The mandrel wires 58 have a tip-to-tip spacing between
their respective ends, which are broken by the insertion of the
dielectric material of the interlayer dielectric layer 10 in the
cut 51, given by a length dimension of the cut 51 parallel to the
length of the wires 58.
[0032] The cut mask 52 in the hardmask pattern is transferred to
the interlayer dielectric layer 10 as a cut 53 between
linearly-aligned non-mandrel wires 56 and as a cut 55 between
linearly-aligned mandrel wires 58 each defining respective areas
over which the interlayer dielectric layer 10 is not etched and
remains intact. The non-mandrel wires 56 have a tip-to-tip spacing
between their respective ends, which are broken by the insertion of
the dielectric material of the interlayer dielectric layer 10 in
the cut 53, given by a length dimension of the cut 53 parallel to
the length of the wires 56. The mandrel wires 58 have a tip-to-tip
spacing between their respective ends, which are broken by the
insertion of the dielectric material of the interlayer dielectric
layer 10 in the cut 55, given by a length dimension of the cut 55
parallel to the length of the wires 58. The non-mandrel wires 56
cut by the cut 53 are positioned adjacent to the mandrel wires 58
cut by the cut 55, which in turn may be arranged adjacent to cut
53.
[0033] The methods as described above are used in the fabrication
of integrated circuit chips. The resulting integrated circuit chips
can be distributed by the fabricator in raw wafer form (e.g., as a
single wafer that has multiple unpackaged chips), as a bare die, or
in a packaged form. The chip may be integrated with other chips,
discrete circuit elements, and/or other signal processing devices
as part of either an intermediate product or an end product. The
end product can be any product that includes integrated circuit
chips, such as computer products having a central processor or
smartphones.
[0034] References herein to terms such as "vertical", "horizontal",
"lateral", etc. are made by way of example, and not by way of
limitation, to establish a frame of reference. Terms such as
"horizontal" and "lateral" refer to a direction in a plane parallel
to a top surface of a semiconductor substrate, regardless of its
actual three-dimensional spatial orientation. Terms such as
"vertical" and "normal" refer to a direction perpendicular to the
"horizontal" and "lateral" direction. Terms such as "above" and
"below" indicate positioning of elements or structures relative to
each other and/or to the top surface of the semiconductor substrate
as opposed to relative elevation.
[0035] A feature "connected" or "coupled" to or with another
element may be directly connected or coupled to the other element
or, instead, one or more intervening elements may be present. A
feature may be "directly connected" or "directly coupled" to
another element if intervening elements are absent. A feature may
be "indirectly connected" or "indirectly coupled" to another
element if at least one intervening element is present.
[0036] 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.
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