U.S. patent application number 16/137111 was filed with the patent office on 2019-01-24 for method and system for forming memory fin patterns.
The applicant listed for this patent is Tokyo Electron Limited. Invention is credited to Anton J. deVilliers, Hoyoung Kang.
Application Number | 20190027481 16/137111 |
Document ID | / |
Family ID | 59387112 |
Filed Date | 2019-01-24 |
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United States Patent
Application |
20190027481 |
Kind Code |
A1 |
Kang; Hoyoung ; et
al. |
January 24, 2019 |
METHOD AND SYSTEM FOR FORMING MEMORY FIN PATTERNS
Abstract
Techniques disclosed herein, provide a method and fabrication
structure for accurately increasing feature density for creating
high-resolution features and also for cutting on pitch of
sub-resolution features. Techniques include using multiple
materials having different etch characteristics to selectively etch
features and create cuts or blocks where specified. A multiline
layer is formed of three or more different materials that provide
differing etch characteristics. Etch masks, including interwoven
etch masks, are used to selectively etch cuts within selected,
exposed materials. Structures can then be cut and formed. Forming
structures and cuts can be recorded in a memorization layer, which
can also be used as an etch mask.
Inventors: |
Kang; Hoyoung; (Guilderland,
NY) ; deVilliers; Anton J.; (Clifton Park,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tokyo Electron Limited |
Tokyo |
|
JP |
|
|
Family ID: |
59387112 |
Appl. No.: |
16/137111 |
Filed: |
September 20, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15416916 |
Jan 26, 2017 |
10115726 |
|
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16137111 |
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62288846 |
Jan 29, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/3081 20130101;
H01L 27/10879 20130101; H01L 21/3088 20130101; H01L 21/3086
20130101; H01L 21/0274 20130101; H01L 21/823431 20130101 |
International
Class: |
H01L 27/108 20060101
H01L027/108; H01L 21/308 20060101 H01L021/308; H01L 21/027 20060101
H01L021/027; H01L 21/8234 20060101 H01L021/8234 |
Claims
1. A method for patterning a substrate, the method comprising:
forming a multi-line layer above a memorization layer on a
substrate, the multi-line layer including a region having a pattern
of alternating lines of materials that differ chemically from each
other by having different etch resistivities relative to each
other, the materials include material A, material B, and material
C, the pattern of alternating lines alternate in a direction
parallel to a working surface of the substrate; forming a first
etch mask above the multi-line layer; etching through uncovered
portions of material A and portions of the memorization layer
directly underneath the uncovered portions of material A using the
first etch mask; forming a second etch mask above the multi-line
layer; and etching through uncovered portions of material C and
portions of the memorization layer directly underneath the
uncovered portions of material C using the second etch mask.
2. The method of claim 1, further comprising: etching through
material B and portions of the memorization layer directly
underneath material B while the multi-line layer is uncovered.
3. The method of claim 2, further comprising: removing remaining
materials above the memorization layer after completing etch
transfers based on etching through material A, material B, and
material C, the memorization layer resulting in a relief pattern
having an array of parallel line segments.
4. The method of claim 2, wherein parallel line segments of the
array of parallel line segments have a pitch less than 40
nanometers.
5. The method of claim 2, wherein line cuts are created in the
memorization layer prior to creating lines in the memorization
layer, and wherein the memorization layer comprises a hardmask
material.
6. The method of claim 2, wherein one or more lines of the
multi-line layer are formed by self-aligned double patterning or
self-aligned quadruple patterning.
7. The method of claim 2, further comprising: transferring the
relief pattern having the array of parallel line segments into an
underlying layer such that an array of fins are created in the
underlying layer.
8. The method of claim 2, wherein etching through material B occurs
subsequent to etching through material A and etching through
material C.
9. The method of claim 2, wherein etching through material B occurs
prior to etching through material A and etching through material
C.
10. The method of claim 1, further comprising forming a hardmask
layer above the multi-line layer prior to forming the first etch
mask and forming the second etch mask; and; etching through
corresponding portions of the hardmask layer using the first etch
mask and the second etch mask.
11. The method of claim 10, wherein forming the first etch mask
includes depositing a radiation-sensitive material on the
substrate, and developing the radiation-sensitive material after
photolithographic exposure; wherein forming the second etch mask
includes depositing a second radiation-sensitive material on the
substrate, and developing the second radiation-sensitive material
after photolithographic exposure; and further comprising, prior to
depositing the second radiation-sensitive material, and subsequent
to etching through the uncovered portions of material A and
portions of the memorization layer directly underneath the
uncovered portions of material A, filling openings in the
memorization layer and in the multi-line layer with material C.
12. The method of claim 11, further comprising, prior to etching
through material B and portions of the memorization layer directly
underneath material B, filling openings in the memorization layer
and in the multi-line layer.
13. The method of claim 1, wherein forming the first etch mask
includes: forming bilayer mandrels that have an upper material and
a lower material, the upper material having a different etch
resistivity as compared to the lower material; forming sidewall
spacers on the bilayer mandrels, an array of the bilayer mandrels
and the sidewall spacers defining trenches between exposed
sidewalls of adjacent sidewall spacers.
14. The method of claim 13, wherein forming the second etch mask
includes: filling the defined trenches between the adjacent
sidewall spacers of the first etch mask; removing the upper
material of the bilayer mandrels such that the lower material is
uncovered; and removing the lower material of the bilayer
mandrels.
15. The method of claim 1, wherein forming the multi-line layer
above the memorization layer includes: forming mandrels using
material A; forming sidewall spacers on sidewalls of mandrels using
material B; and forming fill structures using material C, the fill
structures filling trenches between adjacent spacers.
16. The method of claim 15, wherein a first pitch between lines of
material B is less than 40 nanometers, and wherein a second pitch
between the mandrels and the fill structures is less than 40
nanometers.
17. A method for patterning a substrate, the method comprising:
forming a multi-line layer above a memorization layer on a
substrate, the multi-line layer including a region having a pattern
of alternating lines of materials that differ chemically from each
other by having different etch resistivities relative to each
other, alternating lines includes mandrels, sidewall spacers, and
fill structures, the pattern of alternating lines includes
alternating lines of the mandrels and lines of the fill structures
with the sidewall spacers positioned between lines of the mandrels
and lines of the fill structures; forming a first etch mask above
the multi-line layer; etching through uncovered portions of
mandrels and portions of the memorization layer directly underneath
the uncovered portions of mandrels using the first etch mask;
forming a second etch mask above the multi-line layer; etching
through uncovered portions of the fill structures and portions of
the memorization layer directly underneath the uncovered portions
of the fill structures using the second etch mask; and etching
through the sidewall spacers and portions of the memorization layer
directly underneath the sidewall spacers with the multi-line layer
uncovered.
18. The method of claim 17, further comprising: removing remaining
materials above the memorization layer after completing etch
transfers based on etching through the mandrels, the fill
structures, and the sidewall spacers, the memorization layer being
a relief pattern having an array of parallel line segments; and
transferring the relief pattern having the array of parallel line
segments into an underlying layer such that an array of fins is
created in the underlying layer.
19. A method of patterning a substrate, the method comprising:
creating a fin array pattern in a memorization layer by: forming a
first composite etch mask that includes a first etch mask
positioned on a multi-line layer, and selectively etching through a
first material of the multi-line layer and into a memorization
layer underlying the multi-line layer using the first composite
etch mask; subsequent to etching the first material, forming a
second composite etch mask that includes a second etch mask
positioned on the multi-line layer, and selectively etching through
a second material of the multi-line layer and into the memorization
layer using the second composite etch mask; and subsequent to
etching the second material, selectively etching through a third
material of the multi-line layer and into the memorization layer
without the multi-line layer being covered.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Ser. No.
15/416,916 entitled "METHOD AND SYSTEM FOR FORMING MEMORY FIN
PATTERNS," filed Jan. 26, 2017, which in turn claims priority to
U.S. Provisional Patent Application No. 62/288,846, filed on Jan.
29, 2016, entitled "METHOD AND SYSTEM FOR FORMING MEMORY FIN
PATTERNS," which is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] This disclosure relates to substrate processing, and, more
particularly, to techniques for patterning substrates including
patterning semiconductor wafers.
[0003] Methods of shrinking line-widths in lithographic processes
have historically involved using greater-NA optics (numerical
aperture), shorter exposure wavelengths, or interfacial media other
than air (e.g., water immersion). As the resolution of conventional
lithographic processes has approached theoretical limits,
manufacturers have started to turn to double-patterning (DP)
methods to overcome optical limitations.
[0004] In material processing methodologies (such as
photolithography), creating patterned layers comprises the
application of a thin layer of radiation-sensitive material, such
as photoresist, to an upper surface of a substrate. This
radiation-sensitive material is transformed into a relief pattern
which can be used as an etch mask to transfer a pattern into an
underlying layer on a substrate. Patterning of the
radiation-sensitive material generally involves exposure of actinic
radiation through a reticle (and associated optics) onto the
radiation-sensitive material using, for example, a
photo-lithography system. This exposure can then be followed by the
removal of irradiated regions of the radiation-sensitive material
(as in the case of positive photoresist), or non-irradiated regions
(as in the case of negative resist) using a developing solvent.
This mask layer can comprise multiple sub-layers.
[0005] Conventional lithographic techniques for exposing a pattern
of radiation or light onto a substrate have various challenges that
limit a size of features exposed, and limit pitch or spacing
between exposed features. One conventional technique to mitigate
exposure limitations is that of using a double patterning approach
to allow the patterning of smaller features at a smaller pitch than
what is currently possible with conventional lithographic
techniques.
SUMMARY
[0006] Semiconductor technologies are continually progressing to
smaller feature sizes including feature sizes of 14 nanometers, 7
nm, 5 nm, and below. This continual reduction in sizes of features
from which various elements are fabricated places ever-greater
demands on techniques used to form the features. The concept of
"pitch" can be used to describe the sizing of these features. Pitch
is the distance between the two identical points in two adjacent
repetitive features. Half-pitch then is half the distance between
identical features of an array.
[0007] Pitch reduction techniques, often somewhat erroneously, yet
routinely, termed "pitch multiplication" as exemplified by "pitch
doubling" etc., can extend the capabilities of photolithography
beyond feature size limitations (optical resolution limitations).
That is, conventional multiplication of pitch (more accurately
pitch reduction or multiplication of pitch density) by a certain
factor involves reducing a target pitch by a specified factor.
Double patterning techniques used with 193 nm immersion lithography
are conventionally considered as one of the most promising
techniques to pattern 22 nm nodes and smaller. Noteworthy is that
self-aligned double patterning (SADP) has already been established
as a pitch density doubling process and has been adapted in high
volume manufacturing of NAND flash memory devices. Moreover,
ultra-fine resolution can be obtained to repeat the SADP step,
resulting in pitch quadrupling.
[0008] Although there exist several patterning techniques to
increase pattern density or pitch density, conventional patterning
techniques suffer from poor resolution or rough surfaces of etched
features. Thus, conventional techniques cannot provide a level of
uniformity and fidelity desired for very small dimensions (20 nm
and smaller). Reliable lithographic techniques can produce features
having a pitch of about 80 nm. Conventional and emerging design
specifications, however, desire to fabricate features having
critical dimensions less than about 20 nm or 10 nm. Moreover, with
pitch density doubling and quadrupling techniques, sub-resolution
lines can be created, but making cuts or connections between these
lines is challenging, especially since the pitch and dimensions
needed for such cuts is far below capabilities of conventional
photo-lithography systems.
[0009] Techniques disclosed herein provide a method for pitch
reduction (increasing pitch/feature density) for creating
high-resolution features and also for cutting on pitch of
sub-resolution features, such as to create, for example, structures
for memory arrays. Techniques herein include forming a multi-line
layer of materials of different etch resistivities. Etch mask
combinations can be used to make cuts first followed by creating
fins, line segments, or other structures. With cuts and fins being
defined by multiple different material types--instead of being
defined by a photomask only--cuts can be self-aligned to fins to
create fin arrays or other structural arrays that have better
process margins as compared to conventional techniques for making
fins.
[0010] One embodiment includes a method for patterning a substrate,
such as to fabricate fins for memory arrays. A multi-line layer is
formed above a memorization layer on a substrate. The multi-line
layer includes a region having a pattern of alternating lines of
three materials that differ chemically from each other by having
different etch resistivities relative to each other. The three
differing materials include material A, material B, and material C.
The pattern of alternating lines of three materials includes a
repeating sequence of A-B-C-B-A-B-C-B in that materials alternate
in a direction parallel to a working surface of the substrate. Each
line of material extends from a top surface of the multi-line layer
to a bottom surface of the multi-line layer.
[0011] A first etch mask is formed above the multi-line layer. The
first etch mask defines first trenches that uncover a first portion
of the multi-line layer such that defined first trenches
elevationally intersect multiple lines from the pattern of
alternating lines. Uncovered portions of material A and portions of
memorization layer directly underneath uncovered portions of
material A are etched through using the first etch mask. A second
etch mask is formed above the multi-line layer. The second etch
mask defines second trenches that uncover a second portion of the
multi-line layer such that second defined trenches elevationally
intersect multiple lines from the pattern of alternating lines.
Uncovered portions of material C and portions of memorization layer
directly underneath uncovered portions of material C are then
etched through using the second etch mask. Material B and portions
of memorization layer directly underneath material B are etched
through while the multi-line layer is uncovered.
[0012] Accordingly, fins can be created with cuts that are
self-aligned and not dependent on accurate photolithographic
registration. Instead of relying on photolithographic alignment,
cut placement can be based on deposited material thicknesses and
differential etch resistivities.
[0013] Of course, the order of discussion of the different steps as
described herein has been presented for clarity sake. In general,
these steps can be performed in any suitable order. Additionally,
although each of the different features, techniques,
configurations, etc. herein may be discussed in different places of
this disclosure, it is intended that each of the concepts can be
executed independently of each other or in combination with each
other. Accordingly, the present invention can be embodied and
viewed in many different ways.
[0014] Note that this summary section does not specify every
embodiment and/or incrementally novel aspect of the present
disclosure or claimed invention. Instead, this summary only
provides a preliminary discussion of different embodiments and
corresponding points of novelty over conventional techniques. For
additional details and/or possible perspectives of the invention
and embodiments, the reader is directed to the Detailed Description
section and corresponding figures of the present disclosure as
further discussed below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] A more complete appreciation of various embodiments of the
invention and many of the attendant advantages thereof will become
readily apparent with reference to the following detailed
description considered in conjunction with the accompanying
drawings. The drawings are not necessarily to scale, with emphasis
instead being placed upon illustrating the features, principles and
concepts.
[0016] FIGS. 1A-10A are cross-sectional schematic views of an
example substrate segment showing a process flow according to
embodiments disclosed herein.
[0017] FIGS. 1B-10B are schematic top views of an example substrate
segment showing a process flow according to embodiments disclosed
herein.
[0018] FIGS. 3C and 6C are cross-sectional top views of an example
substrate segment showing a process flow according to embodiments
disclosed herein.
[0019] FIG. 10C is an example perspective view of an example
substrate segment showing a process flow according to embodiments
disclosed herein.
[0020] FIGS. 11A-20A are cross-sectional schematic views of an
example substrate segment showing a process flow according to
embodiments disclosed herein.
[0021] FIGS. 11B-20B are schematic top views of an example
substrate segment showing a process flow according to embodiments
disclosed herein.
DETAILED DESCRIPTION
[0022] Techniques disclosed herein, provide a method and
fabrication structure for accurately increasing feature density for
creating high-resolution features and also for cutting on pitch of
sub-resolution features. Techniques include using multiple
materials having different etch characteristics to selectively etch
features and create cuts or blocks where specified. In general, a
multiline layer is formed of three or more different materials that
provide differing etch characteristics. Then etch masks can be
used, including interwoven etch masks, to selectively etch cuts
within selected, exposed materials. Structures can then be cut and
formed. Forming structures and cuts can be recorded in a
memorization layer, which (when component patterns have been
recorded) can be used as an etch mask for forming structures in an
underlying layer.
[0023] There are various types of structures that can be formed
with techniques herein. For convenience in describing embodiments,
focus will primarily be in describing forming memory fin patterns
or fin arrays. Techniques herein, for example, can enable creating
DRAM (dynamic random-access memory) fin patterns with better
process margins. In DRAM fin patterning, line cutting is extremely
challenging. For example, with progression of feature scaling or
size reduction, lines for such fin patterns are being formed at
sub-resolution dimensions, such as by using self-aligned quad
patterning techniques to form mandrels and lines. In a conventional
fin fabrication flow, fins or lines are formed in a memorization
layer, such as a hardmask layer. This hardmask layer is then
planarized with one or more materials, and then an etch mask is
formed on top by photolithographic patterning techniques. After
developing a photoresist layer exposed to a photomask of cuts, the
result is that the photoresist layer looks like an array of
relatively small holes. These holes are designed to align directly
over sub-resolution formed lines to make cuts in these lines as
that pattern is transferred (etched) through several layers to cut
buried lines in the hardmask layer at specified locations. The
challenge is that with overlay or photolithographic misalignment,
the lines can be only partially cut or not cut at all if a cut
lands between two adjacent lines, which leads to or causes device
failure. For sub-resolution cuts, there may be two different cut
masks to cut the buried lines at desired locations.
[0024] Accordingly, embodiments herein can be used for patterning a
substrate. This can include making a composite etch mask for
transferring sub-resolution patterns, such as a fin array.
Referring now to FIGS. 1A and 1B, a multi-line layer 150 is formed
above a memorization layer 140 on a substrate. Underlying layer 135
can be positioned under memorization layer 140. Note that this
substrate stack can include additional intermediate layers or films
to assist with fabrication. FIG. 1A shows a side cross-sectional
view of an example substrate segment, while FIG. 1B shows a top
view of the corresponding substrate segment. Note that this figure
numbering repeats for subsequent figures herein in that figure
numbers with a letter "A" designate side views while figure numbers
with a letter "B" designate top views. The multi-line layer 150
includes a region having a pattern of alternating lines of three or
more materials that differ chemically from each other by having
different etch resistivities relative to each other. The three
differing materials include material A, material B, and material C.
One or more lines of the multi-line layer can be formed by
self-aligned double patterning or self-aligned quadruple patterning
or other pitch multiplication techniques.
[0025] The pattern of alternating lines of three materials includes
a repeating sequence of A-B-C-B-A-B-C-B in that materials alternate
in a direction parallel to a working surface of the substrate. In
other words, the pattern of alternating lines of three materials
alternates horizontally across a substrate, assuming that a working
surface of the substrate is oriented horizontally. Bracket 151
shows an example repeating sequence. In one embodiment, a shortest
segment of the repeating pattern is A-B-C-B, which then repeats.
FIGS. 1A and 1B show letters A, B, and C above each line or
material type. Each line of material extends from a top surface of
the multi-line layer to a bottom surface of the multi-line layer.
In other words, each line of material is accessible to etchants
from above, and can be etched completely through multi-line layer
150 to access the memorization layer 140 and any intervening
films.
[0026] Having different etch resistivities from each other, as used
herein, means that there is at least one etchant (or etchant
combination) that etches a given one material at a greater rate
than the other material(s). Note that there can exist particular
etchants that etch two or more given materials at a same rate, but
there is at least one etchant that etches an included material
faster relative to the other material(s). Etching one material
relative to another can include etching one material without
substantially etching the other, or etching one material at a
substantially greater rate as compared to the other material such
as having an etch rate ratio of 3:1, 4:1, 10:1, etc. For two
materials to have different etch resistivities this typically means
that two materials are chemically different from each other such as
by particular atomic elements included. Two materials that are
largely the same, except that one of the two materials includes a
dopant, can nevertheless have different etch resistivities.
Moreover, materials having the same atomic elements but with
differing molecular or crystal structures can provide an etch
resistivity differential also.
[0027] Referring now to FIGS. 2A and 2B, a first etch mask 161 is
formed above the multi-line layer 150. The first etch mask defines
first trenches that uncover a first portion of the multi-line layer
such that defined first trenches elevationally intersect multiple
lines from the pattern of alternating lines. In other words,
trenches defined by the first etch mask 161 cross over the
underlying pattern of alternating lines, such as from a viewpoint
of a directional etch or normal to the working surface of the
substrate. In FIG. 2B it is possible to see (looking between the
defined trenches) line segments and the repeating pattern. Note
that the intersection or crossing of lines does not need to be
perpendicular, but can cross at acute/oblique angles also. Note
that for convenience of explanation, first etch mask 161 is
illustrated as a single layer positioned directly on multi-line
layer 150. First etch mask 161 can be formed via conventional
photolithographic techniques, which can include first depositing a
planarization layer on the substrate, then an anti-reflective
coating, and then a layer of radiation-sensitive material, such as
photoresist, then exposure, and development of portions that are
soluble or have become soluble. In alternative embodiments, a
hardmask layer can be deposited on multi-line layer 150 prior to
the planarization layer, or deposited on the planarization layer.
Having a hardmask layer deposited above the multi-line layer 150
and below the first etch mask 161 can be beneficial in some process
flows.
[0028] Referring now to FIGS. 3A and 3B, an etching operation is
executed that etches through uncovered portions of material A and
then uncovered portions of memorization layer 140 directly
underneath uncovered portions of material A using the first etch
mask 161. If a hardmask has been deposited on multi-line layer 150,
then the hardmask is etched through corresponding to the first etch
mask 161. In FIG. 3B, material A is no longer visible through the
trenches, but portions of underlying layer 135 are now visible. For
better understanding, FIG. 3C shows a top view of what memorization
layer 140 looks like at this stage in the process if overlying
layers were removed from memorization layer 140.
[0029] Referring now to FIGS. 4A and 4B, spaces in multi-line layer
150 and memorization layer 140 are then filled with a particular
material. For example, material C can be deposited on the substrate
to fill openings. Such a fill could initially result in an
overburden of material C, and then the substrate can be planarized
back to a top of the multi-line layer 150, as shown in FIG. 4B.
Prior to such a fill, the first etch mask 161, and accompanying
layers, can be removed. If a hardmask layer is incorporated on top
of the multi-line layer 150, this hardmask layer can remain on the
substrate. Note also that planarizing back to a top surface of
multi-line layer 150 is not needed. Instead, one option, is to use
the fill layer of material C (or other material) as a planarization
layer for depositing a subsequent etch mask.
[0030] Referring now to FIGS. 5A and 5B, a second etch mask 162 is
formed above the multi-line layer 150. The second etch mask defines
second trenches that uncover a second portion of the multi-line
layer such that defined second trenches elevationally intersect
multiple lines from the pattern of alternating lines. In FIG. 5B,
between the defined second trenches it is possible to see line
segments and the repeating pattern. Second etch mask 162 can be
formed via conventional photolithographic techniques, which can
include first depositing a planarization layer on the substrate,
then an anti-reflective coating, and then a layer of photoresist.
Note that second etch mask 162 is similar to first etch mask 161,
except that trench locations are shifted to be positioned in
between positions of trenches from the first etch mask 161.
[0031] Referring now to FIGS. 6A and 6B, an etching operation is
executed that etches through uncovered portions of material C and
then uncovered portions of memorization layer 140 directly
underneath uncovered portions of material C using the second etch
mask 162. If a hardmask layer is used above multi-line layer 150,
then the hardmask layer is etched through corresponding to the
second etch mask 162. In FIG. 6B, material C is no longer visible
between the trenches, but portions of underlying layer 135 are now
visible. For better visualization, FIG. 6C shows a top view of what
memorization layer 140 looks like at this stage in the process if
overlying layers were removed from memorization layer 140.
[0032] At this point, second etch mask 162 (and associated layers)
can be removed. Referring now to FIGS. 7A and 7B, spaces in
multi-line layer 150 and memorization layer 140 are then filled
with a particular material. For example, material C can be
deposited on the substrate to fill these openings. Such a fill
could initially result in an overburden of material C. This
overburden can be removed as the substrate is planarized back to a
top of the multi-line layer 150, as shown in FIG. 7B. If a hardmask
layer is optionally incorporated on top of the multi-line layer
150, then this hardmask layer is removed either before or after
filling spaces and planarizing down to a top surface of multi-line
layer 150 so that all of material B (lines of material B) is
uncovered.
[0033] Referring now to FIGS. 8A and 8B, an etching operation is
executed that etches through uncovered portions of material B and
then uncovered portions of memorization layer 140 directly
underneath uncovered portions of material B. Note that a separate
etch mask is not needed for etching material B. Instead, materials
A and C (and material used to fill spaces) function as an etch mask
having different etch resistivities to a particular etchant as
compared to material B. In FIG. 8B, material B is no longer visible
and trenches have been etched into memorization layer 140 so that
portions of underlying layer 135 are now visible.
[0034] Referring now to FIGS. 9A and 9B, remaining materials above
the memorization layer can be removed after completing etch
transfers based on etching through material A, material B, and
material C. The memorization layer results in a relief pattern
having an array of parallel line segments. In some embodiments,
parallel line segments of the array of line segments have a pitch
less than 40 nanometers. For example, a pitch between adjacent
lines of material B is less than 40 nanometers, and a pitch between
adjacent lines of material A and material C is less than 40
nanometers. The memorization layer 140 (which can be comprised of
hardmask material, such as titanium nitride) can then be used as an
etch mask for transferring the pattern of line segments into
underlying layer 135 to create an array of fins, as shown in FIGS.
10A and 10B. FIG. 10C is a perspective view of the substrate
segment showing fabricated line segments with memorization layer
140 still on the substrate. Additional processing can include
removing the memorization layer 140, and/or further blocking,
cutting, doping, etc.
[0035] Note that in this embodiment, cuts are created prior to
creating lines to be cut. For example, etching through material B
occurs subsequent to etching through material A and etching through
material C. Thus, cuts (removed material) from the memorization
layer 140 can be created prior to creating lines in the
memorization layer 140 to be cut. In other embodiments, however,
etching through material B can occur prior to etching through
material A and etching through material C.
[0036] FIGS. 11-20 illustrate another example process flow that
uses bilayer mandrels for forming etch masks to access the
multi-line layer. FIGS. 11A and 11B are similar to FIGS. 1A and 1B,
with a difference that the substrate segment has been rotated 90
degrees to better depict cross sections of masking layers above
multi-line layer 150.
[0037] Referring now to FIGS. 12A and 12B, forming the first etch
mask 161 includes forming bilayer mandrels 165 that have an upper
material 166 and a lower material 167. The upper material 166 has a
different etch resistivity as compared to the lower material 167.
Sidewall spacers 171 are formed on the bilayer mandrels. FIG. 12A
shows sidewall spacers 171 in a formed state, but forming can
involve depositing a conformal film over the bilayer mandrels, and
then executing a spacer open etch to remove conformal material from
over the bilayer mandrel and over the multi-line layer 150 between
sidewall spacers 171. First etch mask 161 includes multiple bilayer
mandrels 165 and sidewall spacers 171 defining trenches between
exposed sidewalls of adjacent sidewall spacers.
[0038] FIGS. 13A and 13B are similar to FIGS. 3A and 3B. An etching
operation is executed that etches through uncovered portions of
material C and then uncovered portions of memorization layer 140
directly underneath uncovered portions of material C using the
first etch mask 161. After this etching operation, a fill layer 168
is deposited on the substrate as shown in FIGS. 14A and 14B. This
includes filling defined trenches between adjacent sidewall spacers
of the first etch mask. Fill layer 168 can be a same material as
upper material 166. The substrate is then planarized down to an
upper surface of lower material 167 of the bilayer mandrels 165.
Thus, the lower portion of the bilayer mandrels 165 can function as
a planarization stop material such as with chemical mechanical
polishing. A result of such a planarization step is shown in FIGS.
15A and 15B.
[0039] With the lower material 167 of the bilayer mandrels 165
exposed, the bilayer mandrels 165 can be completely removed to
result in a second etch mask 162, as shown in FIG. 16A. The second
etch mask defines second trenches that uncover a second portion of
the multi-line layer such that defined second trenches
elevationally intersect multiple lines from the pattern of
alternating lines. An etching operation is executed that etches
through uncovered portions of material A and then uncovered
portions of memorization layer 140 directly underneath uncovered
portions of material A using the second etch mask 162. A result of
such etch transfer is shown in FIGS. 16A and 16B as underlying
layer 135 is now visible from the top view in FIG. 16B.
[0040] Second etch mask 162 (and associated films) can be removed.
Referring now to FIGS. 17A and 17B, spaces in multi-line layer 150
and memorization layer 140 can be filled with a particular
material. For example, material C can be deposited on the substrate
to fill openings. Such a fill could initially result in an
overburden of material C, and then the substrate can be planarized
back to a top of the multi-line layer 150, as shown in FIG. 17B. If
a hardmask layer is incorporated on top of the multi-line layer
150, then this hardmask layer can be removed either before or after
filling spaces and planarizing down to a top surface of multi-line
layer 150 so that all of material B (lines of material B) is
uncovered.
[0041] Referring now to FIGS. 18A and 18B, an etching operation is
executed that etches through uncovered portions of material B and
then uncovered portions of memorization layer 140 directly
underneath uncovered portions of material B. Note that a separate
etch mask is not needed for etching material B. Instead, materials
A and C and filler materials function as an etch mask having
different etch resistivities to a particular etchant as compared to
material B. In FIG. 18B, material B is no longer visible and
trenches have been etched into memorization layer 140 so that
portions of underlying layer 135 are now visible.
[0042] Referring now to FIGS. 19A and 19B, remaining materials
above the memorization layer 140 can be removed after completing
etch transfers based on etching through material A, material B, and
material C, the memorization layer resulting in a relief pattern
having an array of parallel line segments. The memorization layer
140 (which can be comprised of hardmask material or metal hardmask
material) can then be used as an etch mask for transferring the
pattern of line segments into underlying layer 135 to create an
array of fins, as shown in FIGS. 20A and 20B. Additional processing
can include removing the memorization layer 140, further blocking,
cutting, doping, etc.
[0043] The multi-line layer 150 can be formed with various
techniques. One technique is similar to how second etch mask 162 of
FIG. 15A is formed. For example, forming the multi-line layer can
include forming mandrels using material A. Mandrels can be a result
of self-aligned quad patterning or other pitch multiplication
patterning. Sidewall spacers are then formed on sidewalls of
mandrels using material B. Then fill structures are formed using
material C, with the fill structures filling trenches between
adjacent spacers. Accordingly, an alternating pattern of lines of
differing materials is created in which each material can be
selectively accessed for etching with respect to the other
materials.
[0044] In another embodiment, a method of patterning a mask
includes forming a multi-line layer above a memorization layer on a
substrate. The multi-line layer includes a region having a pattern
of alternating lines of three materials that differ chemically from
each other by having different etch resistivities relative to each
other. Note that it is not required that the entire multi-line
layer have the pattern of alternating lines, but at least a
portion. The alternating lines includes mandrels, sidewall spacers,
and fill structures. The pattern of alternating lines of three
materials includes alternating lines of mandrels and lines of fill
structures with sidewall spacers positioned between lines of
mandrels and lines of fill structures with each line of material
extending from a top surface of the multi-line layer to a bottom
surface of the multi-line layer.
[0045] A first etch mask is formed above the multi-line layer. The
first etch mask defines first trenches that uncover a first portion
of the multi-line layer such that defined first trenches
elevationally intersect (cross over) multiple lines from the
pattern of alternating lines. An etching operation is executed that
etches through uncovered portions of mandrels and portions of
memorization layer directly underneath uncovered portions of
mandrels using the first etch mask.
[0046] A second etch mask is formed above the multi-line layer. The
second etch mask defines second trenches that uncover a second
portion of the multi-line layer such that second defined trenches
elevationally intersect multiple lines from the pattern of
alternating lines. Another etching operation is executed that
etches through uncovered portions of fill structures and portions
of memorization layer directly underneath uncovered portions of
fill structures using the second etch mask. The multi-line layer is
then uncovered and sidewall spacers and portions of memorization
layer directly underneath sidewall spacers are etched away to
transfer this pattern into the memorization layer, thereby creating
an array of line segments in the memorization layer that are
self-aligned.
[0047] In the preceding description, specific details have been set
forth, such as a particular geometry of a processing system and
descriptions of various components and processes used therein. It
should be understood, however, that techniques herein may be
practiced in other embodiments that depart from these specific
details, and that such details are for purposes of explanation and
not limitation. Embodiments disclosed herein have been described
with reference to the accompanying drawings. Similarly, for
purposes of explanation, specific numbers, materials, and
configurations have been set forth in order to provide a thorough
understanding. Nevertheless, embodiments may be practiced without
such specific details. Components having substantially the same
functional constructions are denoted by like reference characters,
and thus any redundant descriptions may be omitted.
[0048] Various techniques have been described as multiple discrete
operations to assist in understanding the various embodiments. The
order of description should not be construed as to imply that these
operations are necessarily order dependent. Indeed, these
operations need not be performed in the order of presentation.
Operations described may be performed in a different order than the
described embodiment. Various additional operations may be
performed and/or described operations may be omitted in additional
embodiments.
[0049] " Substrate" or "target substrate" as used herein
generically refers to an object being processed in accordance with
the invention. The substrate may include any material portion or
structure of a device, particularly a semiconductor or other
electronics device, and may, for example, be a base substrate
structure, such as a semiconductor wafer, reticle, or a layer on or
overlying a base substrate structure such as a thin film. Thus,
substrate is not limited to any particular base structure,
underlying layer or overlying layer, patterned or un-patterned, but
rather, is contemplated to include any such layer or base
structure, and any combination of layers and/or base structures.
The description may reference particular types of substrates, but
this is for illustrative purposes only.
[0050] Those skilled in the art will also understand that there can
be many variations made to the operations of the techniques
explained above while still achieving the same objectives of the
invention. Such variations are intended to be covered by the scope
of this disclosure. As such, the foregoing descriptions of
embodiments of the invention are not intended to be limiting.
Rather, any limitations to embodiments of the invention are
presented in the following claims.
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