U.S. patent application number 13/102224 was filed with the patent office on 2012-11-08 for sidewall image transfer process employing a cap material layer for a metal nitride layer.
This patent application is currently assigned to INTERNATIONAL BUSINESS MACHINES CORPORATION. Invention is credited to John C. Arnold, Sean D. Burns, Matthew E. Colburn, David V. Horak, Yunpeng Yin.
Application Number | 20120282779 13/102224 |
Document ID | / |
Family ID | 47045744 |
Filed Date | 2012-11-08 |
United States Patent
Application |
20120282779 |
Kind Code |
A1 |
Arnold; John C. ; et
al. |
November 8, 2012 |
SIDEWALL IMAGE TRANSFER PROCESS EMPLOYING A CAP MATERIAL LAYER FOR
A METAL NITRIDE LAYER
Abstract
A cap material layer is deposited on a metal nitride layer. An
antireflective coating (ARC) layer, an organic planarizing layer
(OPL), and patterned line structures are formed upon the cap
material layer. The pattern in the patterned line structures is
transferred into the ARC layer and the OPL. Exposed portions of the
cap material layer are etched simultaneously with the etch removal
of the patterned line structures and the ARC layer. The OPL is
employed to etch the metal nitride layer. The patterned cap
material layer located over the metal nitride layer protects the
top surface of the metal nitride layer, and enables high fidelity
reproduction of the pattern in the metal nitride layer without
pattern distortion. The metal nitride layer is subsequently
employed as an etch mask for pattern transfer into an underlying
layer.
Inventors: |
Arnold; John C.; (Valatie,
NY) ; Burns; Sean D.; (Hopewell Junction, NY)
; Colburn; Matthew E.; (Schenectady, NY) ; Horak;
David V.; (Essex Junction, VT) ; Yin; Yunpeng;
(Guilderland, NY) |
Assignee: |
INTERNATIONAL BUSINESS MACHINES
CORPORATION
Armonk
NY
|
Family ID: |
47045744 |
Appl. No.: |
13/102224 |
Filed: |
May 6, 2011 |
Current U.S.
Class: |
438/703 ;
257/E21.214 |
Current CPC
Class: |
H01L 21/76816 20130101;
H01L 21/32139 20130101; H01L 21/76885 20130101; H01L 21/0337
20130101; H01L 21/31144 20130101 |
Class at
Publication: |
438/703 ;
257/E21.214 |
International
Class: |
H01L 21/302 20060101
H01L021/302 |
Claims
1. A method of patterning a structure comprising: forming a metal
nitride layer on a substrate; forming a cap material layer having a
different composition than said metal nitride layer directly on
said metal nitride layer; forming a stack of an organic planarizing
layer (OPL) and an antireflective coating (ARC) layer on said cap
material layer; forming patterned line structures comprising a
dielectric material on said ARC layer; simultaneously etching said
cap material layer and at least one of said patterned line
structures and said ARC layer, wherein a pattern present in said
ARC layer is transferred through said OPL and said cap material
layer, and a top surfaces of said metal nitride layer is exposed
after said simultaneous etching; transferring said pattern from
said OPL into said metal nitride layer; and transferring said
pattern from said metal nitride layer into an upper portion of said
substrate.
2. The method of claim 1, further comprising: forming a second OPL
over said patterned line structures; applying and patterning a
block level photoresist over said second OPL; and removing a
portion of said second OPL that is not covered by said patterned
block level photoresist.
3. The method of claim 2, further comprising forming a second ARC
layer on said second OPL, wherein said block level photoresist is
applied directly on said second ARC layer.
4. The method of claim 2, further comprising patterning said second
OPL by etching exposed portions of said second OPL employing said
patterned block level photoresist as an etch mask.
5. The method of claim 1, wherein said metal nitride layer is a TiN
layer, a TiW layer, or a WN layer.
6. The method of claim 5, wherein said cap material layer comprises
a dielectric material.
7. The method of claim 6, wherein said cap material layer comprises
silicon oxide, silicon nitride, silicon carbide, or a combination
thereof.
8. The method of claim 1, wherein said metal nitride layer is a TiN
layer, and said cap material layer comprises a metallic material
different from TiN.
9. A method of patterning a structure comprising: forming a metal
nitride layer on a substrate; forming a cap material layer having a
different composition than said metal nitride layer directly on
said metal nitride layer; forming a stack of an organic planarizing
layer (OPL) and an antireflective coating (ARC) layer on said cap
material layer; forming patterned line structures comprising a
dielectric material on said ARC layer; etching said cap material
layer and at least one of said patterned line structures and said
ARC layer employing at least said patterned line structures as an
etch mask, wherein a pattern present in said ARC layer is
transferred through said OPL and said cap material layer, and a top
surfaces of said metal nitride layer is exposed after said
simultaneous etching; transferring said pattern from said OPL into
said metal nitride layer; and transferring said pattern from said
metal nitride layer into an upper portion of said substrate.
10. The method of claim 9, further comprising covering portions of
said patterned line structures with a patterned second OPL, wherein
said OPL is etched employing a combination of said patterned line
structures and said patterned second OPL as an etch mask.
11. The method of claim 10, further comprising: forming a stack of
a blanket OPL, a second ARC layer, and a block level photoresist;
and patterning said stack, wherein a patterned portion of said
blanket OPL is said patterned second OPL.
12. The method of claim 11, wherein said patterned line structures
are exposed outside an area of said patterned stack after said
patterning of said stack.
13. The method of claim 11, wherein exposed portions of said ARC
layer and a remaining portion of said second ARC layer after said
patterning of said stack are etched simultaneously in an etch.
14. The method of claim 13, further comprising simultaneously
etching said patterned second OPL and portions of said OPL that are
not covered by said patterned line structures or said second
OPL.
15. A method of patterning a structure comprising: forming a metal
nitride layer on a substrate; forming a cap material layer having a
different composition than said metal nitride layer directly on
said metal nitride layer; forming a stack of an organic planarizing
layer (OPL) and an antireflective coating (ARC) layer on said cap
material layer; forming mandrels having parallel sidewalls on said
ARC layer; depositing a conformal dielectric layer on said parallel
sidewalls and exposed surfaces of said ARC layer; anisotropically
etching said conformal dielectric layer, wherein remaining portions
of said conformal dielectric layer form patterned line structures
on said parallel sidewalls of said mandrels; etching said cap
material layer and at least one of said patterned line structures
and said ARC layer, wherein a pattern present in said ARC layer is
transferred through said OPL and said cap material layer, and a top
surfaces of said metal nitride layer is exposed after said
simultaneous etching; transferring said pattern from said OPL into
said metal nitride layer; and transferring said pattern from said
metal nitride layer into an upper portion of said substrate.
16. The method of claim 15, further comprising: depositing a
mandrel material layer on said ARC layer; and patterning said
mandrel material layer, wherein patterned portions of said mandrel
material layer are said mandrels.
17. The method of claim 15, wherein said mandrels comprise a
photoresist or amorphous carbon.
18. The method of claim 15, wherein said conformal dielectric layer
is deposited by molecular layer deposition (MLD) in which multiple
reactants are alternately provided in a process chamber to deposit
said conformal dielectric layer.
19. The method of claim 15, wherein said conformal dielectric layer
comprises silicon oxide, silicon nitride, or a combination
thereof.
20. The method of claim 15, wherein said mandrels have a
lithographic pitch in one direction, and a plurality of said
patterned line structures are formed by said anisotropic etching
within said lithographic pitch in said direction.
Description
BACKGROUND
[0001] The present disclosure generally relates to a process for
manufacturing semiconductor structures, and particularly to methods
for sidewall image transfer employing a dielectric cap material
layer on top of a metal nitride layer.
[0002] A sidewall image transfer (SIT) process as known in the art
employs a titanium nitride layer as an etch mask for transferring a
composite image of two independent images. An organic planarizing
layer (OPL) is formed directly on the titanium nitride layer, and
is consumed during the transfer of the composite pattern into the
titanium nitride layer. The OPL tends to be consumed during the
pattern transfer into the titanium nitride layer, resulting in
distortion or loss of fidelity in the transferred pattern in the
titanium nitride layer. A method of enhancing the fidelity of
pattern transfer during a SIT process is desired.
BRIEF SUMMARY
[0003] A cap material layer is deposited on a metal nitride layer.
An antireflective coating (ARC) layer, an organic planarizing layer
(OPL), and patterned line structures are formed upon the cap
material layer. The pattern in the patterned line structures is
transferred into the ARC layer and the OPL. Exposed portions of the
cap material layer are etched simultaneously with the etch removal
of the patterned line structures and the ARC layer. The OPL and the
dielectric cap material layer are employed to etch the metal
nitride layer. The patterned cap material layer located over the
metal nitride layer protects the top surface of the metal nitride
layer, and enables high fidelity reproduction of the pattern in the
metal nitride layer without pattern distortion. The metal nitride
layer is subsequently employed as an etch mask for pattern transfer
into an underlying layer.
[0004] According to an aspect of the present disclosure, a method
of patterning a structure includes: forming a metal nitride layer
on a substrate; forming a cap material layer having a different
composition than the metal nitride layer directly on the metal
nitride layer; forming a stack of an organic planarizing layer
(OPL) and an antireflective coating (ARC) layer on the cap material
layer; forming patterned line structures including a dielectric
material on the ARC layer; simultaneously etching the cap material
layer and at least one of the patterned line structures and the ARC
layer, wherein a pattern present in the ARC layer is transferred
through the OPL and the cap material layer and a top surfaces of
the metal nitride layer is exposed after the simultaneous etching;
transferring said pattern from the OPL into the metal nitride
layer; and transferring said pattern from the metal nitride layer
into an upper portion of the substrate.
[0005] According to another aspect of the present disclosure, a
method of patterning a structure includes: forming a metal nitride
layer on a substrate; forming a cap material layer having a
different composition than the metal nitride layer directly on the
metal nitride layer; forming a stack of an organic planarizing
layer (OPL) and an antireflective coating (ARC) layer on the cap
material layer; forming patterned line structures including a
dielectric material on the ARC layer; simultaneously etching the
cap material layer and at least one of the patterned line
structures and the ARC layer employing at least the patterned line
structures as an etch mask, wherein a pattern present in the ARC
layer is transferred through the OPL and the cap material layer,
and a top surfaces of the metal nitride layer is exposed after the
simultaneous etching; transferring the pattern from the OPL into
the metal nitride layer; and transferring the pattern from the
metal nitride layer into an upper portion of the substrate.
[0006] According to yet another aspect of the present disclosure, a
method of patterning a structure includes: forming a metal nitride
layer on a substrate; forming a cap material layer having a
different composition than the metal nitride layer directly on the
metal nitride layer; forming a stack of an organic planarizing
layer (OPL) and an antireflective coating (ARC) layer on the cap
material layer; forming mandrels having parallel sidewalls on the
ARC layer; depositing a conformal dielectric layer on the parallel
sidewalls and exposed surfaces of the ARC layer; anisotropically
etching the conformal dielectric layer, wherein remaining portions
of said conformal dielectric layer form patterned line structures
on the parallel sidewalls of the mandrels; simultaneously etching
the cap material layer and at least one of the patterned line
structures and the ARC layer, wherein a pattern present in the ARC
layer is transferred through the OPL and the cap material layer,
and a top surfaces of the metal nitride layer is exposed after the
simultaneous etching; transferring the pattern from the OPL into
the metal nitride layer; and transferring the pattern from the
metal nitride layer into an upper portion of the substrate.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0007] FIG. 1 is a vertical cross-sectional view of a first
exemplary structure after deposition of a metal nitride layer, a
cap material layer, an organic planarizing layer (OPL), a first
antireflective coating (ARC) layer, and mandrels having parallel
vertical sidewalls according to a first embodiment of the present
disclosure.
[0008] FIG. 2 is a vertical cross-sectional view of the first
exemplary structure after deposition of a conformal dielectric
layer according to the first embodiment of the present
disclosure.
[0009] FIG. 3 is a vertical cross-sectional view of the first
exemplary structure after formation of patterned line structures by
anisotropically etching the conformal dielectric layer and removal
of the mandrels according to the first embodiment of the present
disclosure.
[0010] FIG. 4 is a vertical cross-sectional view of the first
exemplary structure after deposition of a second OPL and a second
ARC layer according to the first embodiment of the present
disclosure.
[0011] FIG. 5 is a vertical cross-sectional view of the first
exemplary structure after application and lithographic patterning
of a block level photoresist according to the first embodiment of
the present disclosure.
[0012] FIG. 6 is a vertical cross-sectional view of the first
exemplary structure after etching portions of the second ARC layer
and the second OPL that are not covered by the patterned
photoresist according to the first embodiment of the present
disclosure.
[0013] FIG. 7 is a vertical cross-sectional view of the first
exemplary structure after simultaneous etching of the remaining
portions of the second ARC layer and exposed portions of the first
ARC layer, followed by simultaneous etching of the second OPL and
exposed portions of the first OPL according to the first embodiment
of the present disclosure.
[0014] FIG. 8 is a vertical cross-sectional view of the first
exemplary structure after simultaneous etching of the patterned
spacer line structures, the first ARC layer, and exposed portions
of the cap material layer according to the first embodiment of the
present disclosure.
[0015] FIG. 9 is a vertical cross-sectional view of the first
exemplary structure after etching exposed portions of the metal
nitride layer employing the first OPL as an etch mask according to
the first embodiment of the present disclosure.
[0016] FIG. 10 is a vertical cross-sectional view of the first
exemplary structure after transferring the pattern in the metal
nitride layer into an underlying material layer according to the
first embodiment of the present disclosure.
[0017] FIG. 11 is a vertical cross-sectional view of the first
exemplary structure after forming conductive line structures within
the underlying material layer according to the first embodiment of
the present disclosure.
[0018] FIG. 12 is a vertical cross-sectional view of a second
exemplary structure after transferring the pattern in the metal
nitride layer through an underlying material layer according to a
second embodiment of the present disclosure.
[0019] FIG. 13 is a vertical cross-sectional view of the second
exemplary structure after forming conductive line structures within
the underlying material layer according to the second embodiment of
the present disclosure.
[0020] FIG. 14 is a vertical cross-sectional view of a third
exemplary structure after forming trenches in the underlying
material layer including a conductive material according to a third
embodiment of the present disclosure.
[0021] FIG. 15 is a vertical cross-sectional view of the third
exemplary structure after forming a dielectric material layer over
the patterned underlying material layer according to the third
embodiment of the present disclosure.
DETAILED DESCRIPTION
[0022] As stated above, the present disclosure relates to methods
for sidewall image transfer process employing a cap material layer
for a dielectric metal nitride layer, which are now described in
detail with accompanying figures. It is noted that like reference
numerals refer to like elements across different embodiments. The
drawings are not necessarily drawn to scale.
[0023] Referring to FIG. 1, a first exemplary structure according
to a first embodiment of the present disclosure includes a
substrate 10 and a material stack formed thereupon. The substrate
10 can include a semiconductor substrate having semiconductor
devices (not shown) therein. The semiconductor devices can include,
for example, field effect transistors, junction transistors,
diodes, resistors, capacitors, inductors, or any other
semiconductor device known in the art. The substrate 10 may, or may
not, include contact-level dielectric material layers (not shown)
and/or interconnect level dielectric material layers (not shown) as
well as embedded contact via structures (not shown) and/or embedded
wiring level metal interconnect structures. Alternately, the
topmost portion of the substrate 10 can include a semiconductor
material such as single crystalline silicon.
[0024] An underlying material layer 20 can be formed on the
substrate 10. The underlying material layer 20 can be a single
dielectric material layer, a plurality of dielectric material
layers, or a stack of at least one dielectric material layer and a
conductive material layer. For example, the underlying material
layer 20 can be a wiring-level dielectric material layer, a
contact-level dielectric material layer, a conductive material
layer such as a metal layer or a doped semiconductor layer, or
layers for a gate stack such as a stack of a gate dielectric layer
and a gate conductor layer. Exemplary materials that can be
included in the underlying material layer include, but are not
limited to, silicon oxide, silicon nitride, silicon oxynitride,
organosilicate glass, gate dielectric materials known in the art,
gate conductor materials known in the art, doped semiconductor
materials, and conductive metallic materials. The underlying
material layer 20 can be deposited, for example, by chemical vapor
deposition (CVD), spin coating, or by any other deposition method
known in the art. The thickness of the underlying material layer 20
can be from 10 nm to 2,000 nm, although lesser and greater
thicknesses can also be employed.
[0025] An adhesion promotion layer 30 can be optionally deposited
on the top surface of the underlying material layer 20. The
adhesion promotion layer 30 can help enhance adhesion of
subsequently deposited material layers to the underlying material
layer 20. The adhesion promotion layer 30 can include a dielectric
material such as silicon oxide, although other materials can be
employed for the adhesion promotion layer provided that the
material enhances adhesion between the underlying material layer 20
and a metal nitride layer to be subsequently deposited. If the
adhesion promotion layer 30 includes silicon oxide, the adhesion
promotion layer 30 can be deposited by a chemical vapor deposition
(CVD) using tetraethylorthosilicate (TEOS) as a precursor material.
Silicon oxide derived from TEOS, commonly referred to as TEOS
oxide, can be deposited by low pressure chemical vapor deposition
(LPCVD) or plasma enhanced chemical vapor deposition (PECVD). The
thickness of the adhesion promotion layer 30 can be from 3 nm to 60
nm, and typically from 6 nm to 30 nm, although lesser and greater
thicknesses can also be employed.
[0026] A metal nitride layer 40 is deposited on the adhesion
promotion layer 30, or on the underlying material layer 20 if an
adhesion promotion layer is present. The metal nitride layer 40
includes a metal nitride such as TiN, TaN, WN, or other metal
nitride that can function as an etch mask for etching the material
of the underlying material layer 20. Thus, the composition of the
metal nitride layer 40 can be selected depending on the composition
of the underlying material layer 20. For an underlying material
layer 20 including dielectric materials, TiN, TaN, and WN generally
function as a suitable etch mask material. In one embodiment, TiN
is preferred because TiN provides high etch selectivity relative to
silicon oxide, silicon nitride, organosilicate glass, and
semiconductor materials such as silicon and germanium. For an
underlying material layer including other materials (such as
conductive materials), the composition of the metal nitride layer
can be optimized to enhance the etch selectivity of an etch process
that employs the metal nitride layer as an etch mask.
[0027] The metal nitride layer 40 can be deposited, for example, by
chemical vapor deposition (CVD), physical vapor deposition (PVD),
or a combination thereof. The thickness of the metal nitride layer
40 can be from 2 nm to 60 nm, and typically from 4 nm to 30 nm,
although lesser and greater thicknesses can also be employed.
[0028] A cap material layer 50 is deposited on the metal nitride
layer 40. The cap material layer 50 includes a material different
from the material of the metal nitride layer 40.
[0029] In one embodiment, the cap material layer 50 includes a
dielectric material. Exemplary dielectric materials that can be
employed for the cap material layer 50 include, but are not limited
to, silicon oxide, silicon nitride, silicon carbide, and
combinations thereof. If the cap material layer 50 includes a
dielectric material, the cap material layer 50 can be deposited,
for example, by chemical vapor deposition (CVD), molecular layer
deposition (MLD), and/or spin coating. A thermal treatment (such as
an anneal) or a radiation treatment (such as exposure to
ultraviolet light) can be performed on the cap material layer as
needed. The thickness of the cap material layer 50 including a
dielectric material can be from 2 nm to 60 nm, and typically from 4
nm to 30 nm, although lesser and greater thicknesses can also be
employed.
[0030] In another embodiment, the cap material layer 50 includes a
conductive material. Exemplary conductive materials that can be
employed for the cap material layer 50 include, but are not limited
to, TaN, WN, Ti, Ta, W, Cu, and combinations thereof. For example,
the metal nitride layer 40 can be a TiN layer, and the cap material
layer 50 can include a metallic material different from TiN. If the
cap material layer 50 includes a metallic material, the cap
material layer 50 can be deposited, for example, by physical vapor
deposition (PVD), chemical vapor deposition (CVD), or a combination
thereof. The thickness of the cap material layer 50 including a
metallic material can be from 3 nm to 100 nm, and typically from 10
nm to 50 nm, although lesser and greater thicknesses can also be
employed.
[0031] An organic planarizing layer (OPL) is deposited on the
surface of the cap material layer 50. This OPL is herein referred
to as a first OPL 60. The first OPL 60 includes a
non-photosensitive organic polymer including carbon, hydrogen,
oxygen, and optionally fluorine. For example, the first OPL 60 can
include hydrocarbons and/or hydrofluorocarbons. The first OPL 60
can be formed, for example, by spin coating. The thickness of the
first OPL 60 can be from 50 nm to 300 nm, although lesser and
greater thicknesses can also be employed.
[0032] An antireflective coating (ARC) layer is deposited on the
first OPL 60. The antireflective coating (ARC) layer is herein
referred to as the first antireflective coating (ARC) layer 62. The
first ARC layer 62 can include a hydrocarbon based material having
a different material composition than the first OPL 60. In one
embodiment, the first ARC layer 62 comprises silicon at an atomic
concentration from 1% to 50%, and typically from 15% to 43%. In
another embodiment, the first ARC layer 62 comprises a refractory
metal at an atomic concentration from 1% to 50%, and typically from
8% to 45%. The first ARC layer 62 controls reflectivity of the
surface (i.e., the surface of the cap material layer 50) over which
the first OPL 60 is patterned by reducing standing waves and
optical notching. The thickness of the first ARC layer 62 may be
from 15 nm to 150 nm, and typically from 30 nm to 100 nm, although
lesser and greater thicknesses are explicitly contemplated herein.
The first ARC layer can be applied, for example, by spin
coating.
[0033] A mandrel material layer is deposited on the first ARC layer
62. The mandrel material layer can include a photoresist, an
amorphous carbon layer, or a material that can be removed selective
to the material of a conformal dielectric layer to be subsequently
deposited. The mandrel material layer is deposited as a blanket
layer (unpatterned layer), for example, by chemical vapor
deposition (CVD) or spin coating. The thickness of the mandrel
material layer can be from 30 nm to 300 nm, and typically from 60
nm to 150 nm, although lesser and greater thicknesses can also be
employed.
[0034] In one embodiment, the mandrel material layer is a
photoresist layer that can be directly patterned by lithographic
exposure and development. The mandrel material layer is patterned
by lithographic means, i.e., exposure and development, to form
mandrels 70. The lithographic pattern may be a pattern of a
periodic array, or may be an irregular pattern. Preferably, the
lithographic pattern is a pattern of a regular periodic array. The
lithographic pattern may contain an array of lines and spaces, or
may contain a pattern of via holes in a matrix of the mandrel
material layer, or may contain a pattern of isolated structures
separated from one another by a contiguous cavity that laterally
surrounds each isolated structure, i.e., each mandrel 70. Each of
the mandrels 70 may be separated from one another as in the case of
a lithographic pattern containing an array of lines and spaces, or
may be adjoined among one another as in the case of a lithographic
pattern containing an array of via holes.
[0035] In case the pattern in the mandrels 70 comprises a periodic
one dimensional array, the pitch of the pattern in the mandrels 70
is a lithographic dimension, which is herein referred to as a
lithographic pitch p. If the pattern in the mandrels 70 is a
pattern of lines and spaces, the lithographic pitch p is the
lateral dimension of a unit pattern comprising one line and one
space. If the pattern in the mandrels 70 is a pattern of via holes
in a matrix of a contiguous mandrel 70, the lithographic pitch is
the lateral dimension of a unit pattern comprising at least one via
hole. In addition to having periodicity in one direction at the
lithographic pitch p, the pattern in the mandrels 70 may have
another periodicity in another direction. Optionally, overexposure
or underexposure may be employed so that the width of each pattern
between a neighboring pair of the mandrels 70 is less than one half
of the lithographic pitch p.
[0036] The lithographic pitch p is a lithographic dimension, i.e.,
a dimension that may be formed by lithographic means. The
lithographic pitch p is the same as, or greater than, the minimum
lithographic pitch that may be obtained by commercially available
lithography tools. For example, if ArF lithography employing 193 nm
wavelength light is used, the lithographic pitch p is the same as,
or greater than 80 nm, which is the lithographic minimum pitch.
[0037] In other embodiments, the mandrel material layer includes
amorphous carbon or other non-photosensitive material. In such
embodiments, a photoresist (not shown) can be applied over the
mandrel material and is lithographically patterned into shapes
including multiple parallel lines. In one embodiment, the multiple
parallel lines can have the same width and the same pitch. The
pitch of the multiple parallel lines is a lithographic pitch, i.e.,
a pitch that can be printed by a single lithographic exposure
employing a commercially available lithography tool and
photoresist. A minimum lithographic pitch is herein referred to as
a critical pitch, and a pitch that is less than the critical pitch
is herein referred to as a sublithographic pitch. The pattern in
the photoresist is transferred into the mandrel material layer to
pattern the mandrel material layer into mandrels 70. In the case
amorphous carbon or even amorphous silicon is employed as the
mandrel material, the first OPL layer 60 can be replaced by a
organic layer that has degas temperature higher than the mandrel
deposition temperature. In one embodiment, OPL layer 60 can be
replaced by amorphous carbon material through CVD deposition.
[0038] The mandrels have parallel sidewalls. The parallel sidewalls
of the mandrels may vertically coincide with parallel sidewalls of
the patterned photoresist, or may be laterally recessed inward (so
that the mandrels 70 have lesser widths than the widths of the
patterned photoresist). In one embodiment, the mandrels 70 have a
lithographic pitch in one direction, which is a horizontal
direction perpendicular to the parallel sidewalls of the mandrels
70.
[0039] Referring to FIG. 2, a conformal dielectric layer 72L is
deposited on the mandrels 70 and the exposed top surface of the
first ARC layer 62. The conformal dielectric layer 72L is deposited
employing a conformal deposition method such as molecular layer
deposition (MLD), in which multiple reactants are alternately
provided in a process chamber to deposit the conformal dielectric
layer. In MLD, the deposition of the material of the conformal
dielectric layer 72L occurs one molecular layer at a time. The
dielectric material of the conformal dielectric layer 72L can
include, but is not limited to, silicon oxide, silicon nitride, or
a combination thereof. The temperature of the deposition process is
maintained below the decomposition temperature of the material of
the mandrels 70.
[0040] In one embodiment, the mandrels 70 include a photoresist,
and the conformal dielectric layer includes silicon dioxide.
Silicon oxide can be deposited at room temperature employing a
molecular layer deposition process.
[0041] In another embodiment, the mandrels 70 include amorphous
carbon, and the conformal dielectric layer includes silicon oxide
or silicon nitride. Silicon nitride can be deposited at a
temperature about 400.degree. C. employing a molecular layer
deposition process.
[0042] Any other combination of materials for the mandrels 70 and
the conformal dielectric layer 72L can be employed provided that
the material of the mandrels 70 can withstand the deposition
process for the conformal dielectric layer, that the conformal
dielectric layer 72L can be conformally deposited on the sidewalls
of the mandrels 70, and that the mandrels can be removed selective
to the material of the conformal dielectric layer 72L and the first
ARC layer 62.
[0043] Referring to FIG. 3, an anisotropic etch is performed to
remove horizontal portions of the conformal dielectric layer 72L.
The vertical portions of the conformal dielectric layer 72L that
remains on the vertical sidewalls of the mandrels constitute
patterned line structures 72, which include the same dielectric
material as the conformal dielectric layer 72L.
[0044] The mandrels 70 are removed by another etch, which can be an
anisotropic etch or an isotropic etch, that is selective to the
materials of the patterned line structures 72 and the first ARC
layer 62.
[0045] The pattern in the patterned line structures 72 is herein
referred to as a first pattern. The first pattern may include two
patterned line structures within a lithographic pitch p. If the
lithographic pitch is a minimum lithographic pitch that can be
lithographically printed, the width of the patterned line
structures 72 can be a sublithographic width, i.e., a width that is
less than the minimum width of a patterned structure that can be
formed by single exposure and development.
[0046] Referring to FIG. 4, a stack of a blanket organic
planarizing layer and another antireflective coating layer is
deposited, for example, by a spin coating. The blanket organic
planarizing layer is herein referred to as a second OPL 80, which
can have the same composition and range of thickness as the first
OPL 60. The same deposition method can be employed for the second
OPL 80 as for the first OPL 60. The other antireflective coating
layer is herein referred to as a second ARC layer 82, which can
have the same composition and range of thickness as the first ARC
layer 62. The same deposition method can be employed for the second
ARC layer 82 as for the first ARC layer 62.
[0047] Referring to FIG. 5, a block level photoresist 90 is applied
over the stack of the second OPL 80 and the second ARC layer 82.
The block level photoresist 90 is applied directly on the second
ARC layer 82. The block level photoresist 90 is lithographically
patterned to block areas in which the transfer of the pattern in
the patterned line structures 72 is not desired. Specifically,
openings in the block level photoresist 90 are formed only in areas
within which the pattern of the patterned line structures is to be
transferred to underlying layers.
[0048] The lithographic pattern of the block level photoresist 90,
which is herein referred to as a second pattern, may be a pattern
of a periodic array, or may be an irregular pattern. In some
embodiments, the dimensions of the second pattern are longer than
the lithographic pitch p in the first pattern. The second pattern
defines areas in which the first pattern is to be transferred
during a subsequent image transfer, which is referred to as a
sidewall image transfer (SIT) process. The area of the opening in
the patterned block level photoresist 90 corresponds to the area in
which the first pattern is subsequently transferred into the cap
material layer 50 and the metal nitride layer 40, and the area in
which the patterned block level photoresist 90 is present
corresponds to the area within which the first pattern is not to be
transferred.
[0049] Referring to FIG. 6, exposed portions of the second ARC
layer 82 and the second OPL that are not covered by the patterned
block level photoresist 90 are removed by an etch that employs the
patterned block level photoresist 90 as an etch mask. This etch can
be an anisotropic etch. The second ARC layer 82 and second OPL 80
are patterned to replicate the pattern in the patterned block level
photoresist 90, i.e., the patterned remaining portion of the
blanket OPL as originally deposited is the patterned second OPL 80.
The patterned block level photoresist 90 is removed by the end of
OPL layer 80 patterning. The pattern of the patterned line
structures 72 is exposed within the area from which the second OPL
80 is removed, and the rest of the patterned line structures 72
outside the exposed area are covered by the patterned second OPL 80
and the second ARC layer 82. The patterned line structures 72 are
exposed outside the area of the patterned stack 84 after the
patterning of the stack of the second ARC layer 82 and the second
OPL 80.
[0050] Referring to FIG. 7, the remaining second ARC layer 82 and
the exposed portions of the first ARC layer 62 between the exposed
patterned line structures 72 are simultaneously etched.
Specifically, exposed portions of the first ARC layer 62 and the
remaining portion of the second ARC layer 82 are etched
simultaneously in an etch, which can be an anisotropic etch. This
anisotropic etch is herein referred to as a first anisotropic etch.
The pattern of the patterned line structures 72 is transferred into
the first ARC layer 62 within the area in which the second OPL 80
is not present. Openings are formed within the first ARC layer 62
during the anisotropic etch employing at least the patterned line
structures 72 as an etch mask. If the block level photoresist 90 is
employed in previous processing steps, the first ARC layer 62 is
patterned during the anisotropic etch employing a combination of
the patterned line structures 72 and the patterned second OPL 80 as
an etch mask.
[0051] Once the second ARC layer 82 and the exposed portions of the
first ARC layer 62 are etched through, the second OPL 80 and the
portions of the first OPL underlying the openings in the first ARC
layer are simultaneously etched, for example, by another
anisotropic etch, which is herein referred to as a second
anisotropic etch. Thus, the patterned second OPL 80 and portions of
the first OPL 60 that are not covered by the patterned line
structures or the second OPL 80 are etched by this anisotropic
etch. This anisotropic etch proceeds until the second OPL 80 is
completely consumed and the trenches formed within the first OPL 60
extends to the bottom surface of the first OPL 60, i.e., to the top
surface of the cap material layer. Thus, while the patterned line
structures 72 are partly removed, the pattern present in the
patterned line structures 72 within the area not covered by the
second OPL is transferred through the first ARC layer, and the
first OPL.
[0052] Referring to FIG. 8, the patterned line structures 72, the
first ARC layer 62, and the exposed portions of the cap material
layer 50 underneath the trenches within the first OPL are
simultaneously etched by another etch, which can be an anisotropic
etch. This anisotropic etch is herein referred to as a third
anisotropic etch. The pattern in the first ARC layer 62 is
transferred into the cap material layer 50. The third anisotropic
etch can be a reactive ion etch employing a plasma of at least one
fluorocarbon gas such as CF.sub.4, CHF.sub.3, and C.sub.4F.sub.8.
Argon or nitrogen can also be added to the plasma. In general, the
chemistry of the third anisotropic etch is selected to
simultaneously etch the material of the cap material layer 50 and
the materials for the patterned line structures and/or the first
ARC layer 62. Thus, the pattern in the first OPL 60 is transferred
into the cap material layer 50 to form a pattern of trenches
therein, and the top surface of the metal nitride layer 40 is
exposed at the bottom of the trenches. In one embodiment, the
patterned line structures 72 and the first ARC layer 62 are
consumed during the third anisotropic etch.
[0053] While the first, second, and third anisotropic etches are
described herein as three distinctive consecutive etch steps, any
pair of two adjacent anisotropic etches or all three anisotropic
etches can be integrated into a single anisotropic etch step that
employs the same etch chemistry throughout or changes the etch
chemistry during the etch process.
[0054] Referring to FIG. 9, exposed portions of the metal nitride
layer 40 is etched employing the first OPL 60 and the cap material
layer 50 as the etch mask.
[0055] The pattern present in the cap material layer 50 and the
first OPL 60 and transferred into the metal nitride layer 40 is a
composite pattern of the first pattern and the second pattern
because only the portion of the first pattern that is located
within the openings of the block level photoresist 90, as defined
by the second pattern, is transferred into the cap material layer
50 and the first OPL 60, and subsequently into the metal nitride
layer 40. Etch chemistry that removes a metal nitride layer with
high selectivity to an organic planarizing material is not known in
the art. Thus, it is inevitable that a significant portion of the
first OPL 60 is consumed during the transfer of the pattern in the
first OPL 60 into the metal nitride layer 40.
[0056] In one embodiment, the first OPL 60 is partially consumed
during the pattern transfer into the metal nitride layer 40. A
substantial portion of the first OPL 60 is consumed during the
pattern transfer into the metal nitride layer 40, but a portion of
the first OPL may be present at the end of this pattern transfer.
In another embodiment, all or almost all of the first OPL 60 is
consumed during the pattern transfer into the metal nitride layer
40, i.e., by the time the metal nitride layer 40 is etched through.
In such embodiment, the presence of the composite pattern within
the cap material layer 50 enhances the fidelity of pattern
replication in the metal nitride layer 40 because the effect of
erosion of the first OPL 60 toward the end of the pattern transfer
does not affect the fidelity of the pattern that is present in the
cap material layer 50. In other words, the combination of the cap
material layer 50 and the first OPL 60 function as an etch mask so
that the erosion of edges in the first OPL 60 during the etch does
not affect the fidelity of the pattern transfer, but the pattern
present in the cap material layer 50 is replicated with high
fidelity even if the pattern in the first OPL 60 is degraded toward
the end of the etch process due to edge erosion. Any residual first
OPL at the end of the etch is removed, for example, by ashing.
[0057] Referring to FIG. 10, the pattern in the metal nitride layer
40 is transferred into the underlying material layer 20, for
example, by an anisotropic etch such as a reactive ion etch. The
underlying material layer 20 is located in the upper portion of the
substrate 10. In one case, the cap material layer 50 may be removed
selective to the metal nitride layer 40 prior to the transfer of
the pattern through the adhesion promotion layer 30, if present,
and into the underlying material layer 20. In another case, the cap
material layer 50 may be employed as an additional etch mask that
is consumed during an initial phase of the anisotropic etch that
transfers the pattern in the metal nitride layer 40 through the
adhesion promotion layer 30, if present, and into the underlying
material layer 20. In this case, the combination of the cap
material layer 50 and the metal nitride layer 40 is employed as an
etch mask for transferring the composite pattern of the first
pattern and the second pattern into the underlying material layer
20. Once the cap material layer 50 is consumed, the metal nitride
layer is used as the etch mask.
[0058] The underlying material layer 20 can be a dielectric
material layer such as a contact-level dielectric material layer in
which contact via structures can be subsequently formed, or a
wiring-level dielectric material layer in which metal line
structures or metal via structures can be subsequently formed. The
trenches 21 formed in the underlying material layer 20 can extend
to a depth between the top surface and the bottom surface of the
underlying material layer 20.
[0059] Referring to FIG. 11, conductive line structures 22 are
formed within the underlying material layer 20 by depositing a
conductive material such as Cu or W into the trenches 21 in the
underlying material layer 20, and removing excess conductive
material above the topmost surface of the underlying material layer
20 or the adhesion promotion layer 30, for example, by chemical
mechanical planarization (CMP). The remaining portions of the metal
nitride layer 40 can be removed during the removal of the excess
conductive material from above the underlying material layer 20.
Optionally, the adhesion promotion layer 30 may be removed.
[0060] Referring to FIG. 12, a second exemplary structure according
to a second embodiment of the present disclosure can be derived
from the first exemplary structure by extending the duration of the
etch and the depth of the trenches 21 at a processing step
corresponding to FIG. 10. The trenches 21 are extended to the
bottom of the underlying material layer 20 at the end of the etch
step.
[0061] Referring to FIG. 13, conductive line structures 22 are
formed within the underlying material layer 20 employing the same
processing steps as in the first embodiment.
[0062] Referring to FIG. 14, in a third exemplary structure
according to a third embodiment of the present disclosure, the
underlying material layer 20 can include a conductive material. The
trenches 21 are formed through the underlying material layer 20 to
the top surface of the substrate 10, which may include a dielectric
surface. The underlying material layer 20 can be patterned into
multiple conductive portions that do not contact one another.
[0063] Referring to FIG. 15, a dielectric material layer 24 can be
deposited over the patterned underlying material layer 20 to
provide electrical isolation between the various conductive
portions of the patterned underlying material layer 20. Optionally,
additional conductive structures (not shown) may be formed in an
upper portion of the dielectric material layer 24 to provide
electrical connections among the various conductive portions of the
underlying material layer 20.
[0064] While the present disclosure has been particularly shown and
described with respect to preferred embodiments thereof, it will be
understood by those skilled in the art that the foregoing and other
changes in forms and details may be made without departing from the
spirit and scope of the present disclosure. It is therefore
intended that the present disclosure not be limited to the exact
forms and details described and illustrated, but fall within the
scope of the appended claims.
* * * * *