U.S. patent application number 16/529972 was filed with the patent office on 2021-02-04 for method for increasing pattern density on a wafer.
The applicant listed for this patent is Tokyo Electron Limited. Invention is credited to Sanjana Das, Anton J. deVilliers, Daniel Fulford.
Application Number | 20210035815 16/529972 |
Document ID | / |
Family ID | 1000004290870 |
Filed Date | 2021-02-04 |
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United States Patent
Application |
20210035815 |
Kind Code |
A1 |
Das; Sanjana ; et
al. |
February 4, 2021 |
Method for Increasing Pattern Density on a Wafer
Abstract
Techniques herein include a method of patterning semiconductor
wafers with improved line edge roughness (LER) and/or line width
roughness (LWR), including lines below 12 nm in width. An initial
bilayer mandrel is formed. The top layer is trimmed to a particular
ratio. A reversal material protects uncovered portions of the lower
layer, while a central portion is removed, resulting in two
mandrels, each one fifth the initial mandrel width. The resulting
mandrels are transferred into two underlying layers to form second
bilayer mandrels. Sidewall spacers are formed on the second bilayer
mandrels, and a fill material can fill remaining spaces. A
planarization step can planarize the substrate to a bottom layer of
the second bilayer mandrels, which results in a multi-line layer
having square profile lines at 1:1 spacing ratio without spacer
rounding.
Inventors: |
Das; Sanjana; (Hillsboro,
OR) ; deVilliers; Anton J.; (Clifton Park, NY)
; Fulford; Daniel; (Cohoes, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tokyo Electron Limited |
Tokyo |
|
JP |
|
|
Family ID: |
1000004290870 |
Appl. No.: |
16/529972 |
Filed: |
August 2, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/0337 20130101;
H01L 21/32137 20130101; H01L 21/0338 20130101 |
International
Class: |
H01L 21/3213 20060101
H01L021/3213; H01L 21/033 20060101 H01L021/033 |
Claims
1. A method for patterning a substrate, the method comprising:
receiving a substrate having a first relief pattern formed on a
stack of underlying layers, the first relief pattern includes
linear structures having three layers of material, the three layers
of material include a layer of photoresist positioned on an
anti-reflective coating layer, the anti-reflective coating layer
positioned on a third layer; executing a first etch operation that
is isotropic and uses chemistry that selectively etches the layer
of photoresist without etching the anti-reflective coating layer,
without etching the third layer, and without etching the stack of
underlying layers, wherein the isotropic etch operation results in
the layer of photoresist being at least laterally etched from an
initial width of lines to a resulting width of lines, the resulting
width of lines being less than the initial width of lines;
depositing a fill material on the substrate that fills spaces
between structures of the first relief pattern, covers horizontal
top surfaces of the anti-reflective coating layer, and leaves top
surfaces of the layer of photoresist uncovered; executing a second
etch operation that removes the layer of photoresist and
anisotropically etches uncovered portions of the anti-reflective
coating layer and the third layer; removing the fill material from
the substrate and then transferring a pattern defined by remaining
portions of the third layer into a fourth layer and into a fifth
layer, the fourth layer positioned below the third layer, the fifth
layer positioned below the fourth layer, transferring the pattern
resulting in the fourth layer and the fifth layer forming bi-layer
mandrels; forming sidewall spacers on the bi-layer mandrels;
depositing a second fill material on the substrate that at least
partially fills spaces defined between the sidewall spacers on the
bi-layer mandrels, the second fill material being greater in height
as compared to the fifth layer; and planarizing the substrate by
removing the fourth layer, and removing material from the sidewall
spacers and the second fill material down to a top surface of the
fifth layer such that a multi-line layer is formed having a planar
surface at the top surface of the fifth layer.
2. The method of claim 1, wherein the linear structures have a
first pitch that has a line-to-space ratio of 5:3 in that lines
have a cross-sectional line width of five units while spaces have a
cross-sectional space width of three units.
3. The method of claim 1, wherein the layer of photoresist is
laterally etched such that a resulting width of lines of
photoresist is equal to three fifths of an initial width of lines
of photoresist.
4. The method of claim 1, wherein depositing the fill material
results in an overburden of fill material that is removed by a fill
material etch back process.
5. The method of claim 1, wherein depositing the fill material
results in an overburden of fill material that is removed by
diffusing a solubility-changing agent a predetermined depth into
the fill material from a top surface of the fill material, and
removing soluble portions of the fill material thereby uncovering
top surfaces of the layer of photoresist.
6. The method of claim 1, wherein the fifth layer is selected as a
material resistant to chemical-mechanical planarization.
7. The method of claim 1, further comprising removing the sidewall
spacers from the multi-line layer.
8. The method of claim 1, further comprising forming an etch mask
on the multi-line layer, the etch mask defining openings that
uncover segments of all lines of the multi-line layer.
9. The method of claim 8, further comprising etching uncovered
portions of at least one material from the multi-line layer.
10. The method of claim 9, further comprising etching a sixth layer
positioned under the multi-line layer, wherein the multi-line layer
and the etch mask are used as a combined etch mask.
11. A method of patterning a substrate, the method comprising:
forming a first relief pattern on a stack of underlying layers on a
substrate, the first relief pattern includes linear structures
having three layers of material, the three layers of material
include a first layer positioned on a second layer, the second
layer positioned on a third layer, wherein the linear structures
are formed at a first pitch that has a line-to-space ratio of 5:3
in that lines have a cross-sectional line width of five units while
spaces have a cross-sectional space width of three units; executing
a first etch operation that is isotropic and uses chemistry that
selectively etches the first layer without etching the second
layer, without etching the third layer, and without etching the
stack of underlying layers, wherein the isotropic etch operation
results in the first layer being laterally etched resulting in the
cross-sectional line width of five units being trimmed to a second
cross-sectional line width of three units; depositing a fill
material on the substrate that fills spaces between structures of
the first relief pattern, covers horizontal top surfaces of the
second layer, but leaves top surfaces of the first layer uncovered;
executing a second etch operation that removes the first layer and
anisotropically etches uncovered portions of the second layer and
the third layer; and removing the fill material from the substrate
and then transferring a pattern defined by remaining portions of
the third layer into a fourth layer and a fifth layer, the fourth
layer positioned below the third layer, the fifth layer positioned
below the fourth layer, resulting in the fourth layer and the fifth
layer forming bi-layer mandrels having a second pitch that has a
second line-to-space ratio of 1:3 in that the bi-layer mandrels
have a second cross-sectional line width of one unit while spaces
defined between bi-layer mandrels have a second cross-sectional
space width of three units.
12. The method of claim 11, further comprising: forming sidewall
spacers on the bi-layer mandrels; depositing a second fill material
on the substrate that at least partially fills spaces defined
between the sidewall spacers on the bi-layer mandrels, the second
fill material being greater in height as compared to the fifth
layer; and planarizing the substrate by removing the fourth layer,
and removing material from the sidewall spacers and the second fill
material down to a top surface of the fifth layer such that a
multi-line layer is formed having a planar surface at the top
surface of the fifth layer.
13. The method of claim 11, wherein depositing the fill material
results in an overburden of fill material that is removed by a fill
material etch back process.
14. The method of claim 11, wherein depositing the fill material
results in an overburden of fill material that is removed by
diffusing a solubility-changing agent a predetermined depth into
the fill material from a top surface of the fill material, and
removing soluble portions of the fill material thereby uncovering
top surfaces of the first layer.
15. The method of claim 11, wherein the fifth layer is selected as
a material resistant to chemical-mechanical planarization.
16. The method of claim 12, further comprising removing the
sidewall spacers from the multi-line layer, remaining lines on the
multi-line layer having a third line-to-space ratio of 1:1 in that
each remaining line is one unit wide while each remaining space is
one unit wide.
17. The method of claim 12, further comprising: forming an etch
mask on the multi-line layer, the etch mask defining openings that
uncover segments of all lines of the multi-line layer; etching
uncovered portions of at least one material from the multi-line
layer; and etching a sixth layer positioned under the multi-line
layer, wherein the multi-line layer and the etch mask are used as a
combined etch mask.
18. A method for patterning a substrate, the method comprising:
receiving a substrate having a first relief pattern formed on a
stack of underlying layers, the first relief pattern includes
linear structures having at least two layers of material, the two
layers of material include a first layer positioned on a second
layer; executing a first etch operation that is isotropic and uses
chemistry that selectively etches the first layer without etching
the second layer and without etching the stack of underlying
layers, wherein the isotropic etch operation results in the first
layer being at least laterally etched from an initial width of
lines to a resulting width of lines, the resulting width of lines
being less than the initial width of lines; depositing a fill
material on the substrate that fills spaces between structures of
the first relief pattern and covers horizontal top surfaces of the
second layer, but leaves top surfaces of the first layer; executing
a second etch operation that removes the first layer and
anisotropically etches uncovered portions of the second layer;
removing the fill material from the substrate and then transferring
a pattern defined by remaining portions of the second layer into a
third layer, the third layer positioned below the second layer,
resulting in the third layer forming mandrels for sidewall spacers;
forming sidewall spacers on the mandrels; and removing the mandrels
from the substrate.
19. The method of claim 18, wherein the linear structures have a
first pitch that has a line-to-space ratio of 5:3 in that lines
have a cross-sectional line width of five units while spaces have a
cross-sectional space width of three units.
20. The method of claim 19, wherein the first layer is laterally
etched such that the resulting width of lines of the first layer is
equal to three fifths of the initial width of lines of the first
layer.
Description
BACKGROUND OF THE INVENTION
[0001] This disclosure relates to substrate processing, and, more
particularly, to techniques for patterning substrates including
patterning of semiconductor wafers.
[0002] Methods of shrinking line-widths in lithographic processes
have historically involved using greater-NA (numerical aperture)
optics, shorter exposure wavelengths, or interfacial media other
than air (e.g., water immersion). As the resolution of traditional
lithographic processes has approached theoretical limits,
manufacturers have started to turn to double-patterning (DP)
methods to overcome optical limitations.
[0003] 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 a surface of a substrate. This
radiation-sensitive material is transformed into a relief pattern
(patterned mask) that can be used to etch or transfer a pattern
into an underlying layer on a substrate. Patterning of the
radiation-sensitive material generally involves exposure by a
radiation source through a reticle (and associated optics) onto the
radiation-sensitive material using, for example, a photolithography
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 patterned
mask may comprise multiple sub-layers.
SUMMARY
[0004] Semiconductor technologies are continually progressing to
smaller feature sizes of 14 nanometers and below. The continual
reduction in sizes of features from which the foregoing 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 two
identical points in two adjacent repetitive features.
[0005] Pitch reduction techniques, often somewhat erroneously
termed "pitch multiplication" as exemplified by "pitch doubling"
and "pitch quadrupling," can extend the capabilities of
photolithography beyond feature size limitations (exposure
limitations). That is, conventional "multiplication" of pitch by a
certain factor actually involves reducing the pitch by that factor.
Double patterning techniques (DPT) with 193 nm immersion
lithography are being thought to be one of the most promising
candidates for the 22 nm node and beyond. Especially because
self-aligned spacer double patterning (SADP) has already been
established as a pitch doubling process and adapted in high volume
manufacturing of NAND flash memory devices. Moreover, ultra-fine
resolution can be obtained to repeat the SADP step twice as pitch
quadrupling. The introduction of the reversal layer enables forming
a fine trench pattern and hole pattern. Here the initial pattern is
obtained by X-Y double line exposures. Then, the reversal material
is applied on the initial pattern and subsequent etching process
converts the initial trench pattern to line.
[0006] One embodiment includes a method of patterning a substrate.
A substrate is received having a first relief pattern positioned on
a stack of underlying layers. The first relief pattern includes
linear structures having three layers of material. The three layers
of material include a layer of photoresist positioned on an
anti-reflective coating layer. The anti-reflective coating layer is
positioned on a third layer. The linear structures can have a first
pitch that has a line-to-space ratio of 5:3. An etch operation
selectively etches the layer of photoresist only resulting in the
layer of photoresist being laterally etched from an initial width
of lines to a resulting width of lines equal to three fifths of an
initial width of lines of photoresist. A fill material fills spaces
between structures of the first relief pattern, covers horizontal
top surfaces of the anti-reflective coating layer, and leaves top
surfaces of the layer of photoresist uncovered. A second etch
operation is executed that removes the layer of photoresist and
anisotropically etches uncovered portions of the anti-reflective
coating layer and the third layer. The fill material is removed
from the substrate. A pattern defined by remaining portions of the
third layer is transferred into a fourth layer and into a fifth
layer, using the third layer and second layer as an etch mask. The
fourth layer is positioned below the third layer, and the fifth
layer positioned below the fourth layer. This pattern transfer
results in the fourth layer and the fifth layer forming bi-layer
mandrels. Sidewall spacers are then formed on the bi-layer
mandrels. A second fill material can be deposited on the substrate
that at least partially fills spaces defined between the sidewall
spacers on the bi-layer mandrels. The substrate is then planarized
by removing the fourth layer and removing material from the
sidewall spacers and the second fill material down to a top surface
of the fifth layer such that a multi-line layer is formed having a
planar surface at the top surface of the fifth layer and having
lines with a 1:1 ratio.
[0007] 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.
[0008] 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
[0009] 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.
[0010] FIG. 1 is a cross-sectional view of an example substrate
segment showing a process flow according to embodiments disclosed
herein.
[0011] FIG. 2 is a cross-sectional view of an example substrate
segment showing a process flow according to embodiments disclosed
herein.
[0012] FIG. 3 is a cross-sectional view of an example substrate
segment showing a process flow according to embodiments disclosed
herein.
[0013] FIG. 4 is a cross-sectional view of an example substrate
segment showing a process flow according to embodiments disclosed
herein.
[0014] FIG. 5 is a cross-sectional view of an example substrate
segment showing a process flow according to embodiments disclosed
herein.
[0015] FIG. 6 is a cross-sectional view of an example substrate
segment showing a process flow according to embodiments disclosed
herein.
[0016] FIG. 7 is a cross-sectional view of an example substrate
segment showing a process flow according to embodiments disclosed
herein.
[0017] FIG. 8 is a cross-sectional view of an example substrate
segment showing a process flow according to embodiments disclosed
herein.
[0018] FIG. 9 is a cross-sectional view of an example substrate
segment showing a process flow according to embodiments disclosed
herein.
[0019] FIG. 10 is a cross-sectional view of an example substrate
segment showing a process flow according to embodiments disclosed
herein.
[0020] FIG. 11 is a cross-sectional view of an example substrate
segment showing a process flow according to embodiments disclosed
herein.
[0021] FIG. 12 is a cross-sectional view of an example substrate
segment showing a process flow according to embodiments disclosed
herein.
[0022] FIG. 13 is a cross-sectional view of an example substrate
segment showing a process flow according to embodiments disclosed
herein.
[0023] FIG. 14 is a cross-sectional view of an example substrate
segment showing a process flow according to embodiments disclosed
herein.
DETAILED DESCRIPTION
[0024] Techniques herein include a method of patterning
semiconductor wafers with improved line edge roughness (LER) and/or
line width roughness (LWR), even applicable to lines below 12 nm in
width. An initial bilayer mandrel is formed. The top layer is
trimmed to a particular ratio. A reversal material protects
uncovered portions of the lower layer, while a central portion is
removed, resulting in two mandrels, each one fifth the initial
mandrel width. The resulting mandrels are transferred into two
underlying layers to form second bilayer mandrels. Sidewall spacers
are formed on the second bilayer mandrels, and a fill material can
fill remaining spaces. A planarization step can planarize the
substrate to a bottom layer of the second bilayer mandrels, which
results in a multi-line layer having square profile lines at 1:1
spacing ratio without spacer rounding.
[0025] Embodiments herein include substrate processing techniques
to pattern substrates for microfabrication. Referring to FIG. 1, a
substrate layer stack is prepared on substrate 100. Layers within
the substrate stack can be of various materials and thicknesses, as
well as having different etch resistivities. Substrate 100 includes
layer 107, layer 109, layer 111, layer 114, layer 116, layer 118,
and layer 120. Layer 107 can be a layer of photoresist. Layer 109
can be a bottom anti-reflective coating. Layer 111 can be amorphous
carbon. Layer 114 can be a hardmask material. Layer 116 and layer
118 can be additional memorization layers. Layer 120 can be poly
silicon. The various layers can be deposited by chemical vapor
deposition (CVD), physical vapor deposition (PVD), spin-on
deposition, or any other deposition technique. Different substrate
stacks can have various arrangements of layers and thicknesses
depending on design objectives.
[0026] The layer of photoresist is then exposed to a pattern of
actinic radiation, which creates a latent pattern in the layer of
photoresist. The layer of photoresist is developed, such as by
using negative tone developer, and this results in relief pattern
131 of photoresist, as illustrated in FIG. 2. This relief pattern
can include lines or structures having a 5:3 pitch. By way of a
non-limiting example, the latent pattern can be obtained by using
an X-Y double line dipole exposure on a negative tone develop
photoresist. FIG. 2 and remaining figures include scale 190, which
shows a simplified, relative scale of lines and spaces.
[0027] The photoresist relief pattern is then transferred to one or
more underlying layers. The relief pattern functions as an etch
mask for anisotropically etching underlying layers, such as with
plasma-based etchants. This can include pattern transfer to a layer
of anti-reflective coating, SiON, amorphous carbon, et cetera. A
reactive-ion etching (RIE) process can be used to transfer the
photoresist relief pattern into an anti-reflective coating layer,
and into a planarization film such as an amorphous carbon layer. An
example result is shown in FIG. 3, in which the photoresist relief
pattern has been transferred into layer 109 and layer 111,
resulting in relief pattern 132. As can be seen with scale 190,
relief pattern 132 has a pitch of 8 units, which has a
line-to-space ratio of 5:3 in that lines have a cross-sectional
line width of five units while spaces have a cross-sectional space
width of three units
[0028] Next, the relief pattern of photoresist is trimmed from an
initial width to a modified width that is smaller than the initial
width. By way of a non-limiting example, the photoresist can be
trimmed to three fifths (3/5) of an initial width. FIG. 4
illustrates lines of photoresist that were initially 5 units in
width, but have been trimmed to 3 units of width. This trimming of
the first layer can be executed using an isotropic etch selective
to the photoresist, in that the etch chemistry does not
significantly etch the ARC coating, the amorphous carbon layer, and
the hardmask floor, which could be silicon nitride (SiN), TiN, et
cetera.
[0029] Referring now to FIG. 5, a fill material 122 is deposited on
the substrate to function as a reversal material or reversal layer.
The substrate 100 can be coated with the fill material 122 using
various deposition techniques. If deposition of the fill material
results in an overburden then a top portion of the fill material
can be etched back uniformly or otherwise planarized until
uncovering the relief pattern 131. Another option for planarization
is a diffusion-limited solubility shifting process. The fill
material can be recessed below a top surface of the photoresist
relief pattern. For example an acid or solubility-shifting agent is
deposited on top of the fill material and diffused vertically down
into developable fill material, which makes the diffused
portion/thickness soluble or soluble after a bake step.
Subsequently, the soluble top portion can be developed and removed,
uncovering the relief pattern of photoresist. The fill material can
nevertheless cover the first underlying layer in areas where the
photoresist relief pattern was trimmed. A silicon-containing
developable bottom anti-reflective coating (Si-DBARC) can be used
as the fill material.
[0030] A third etch step is then executed. This third etch step is
directional and selective. The fill material resists being etched,
while the photoresist is etched as well as uncovered portions of
the second layer (layer 109) and the third layer (layer 111)
underlying the photoresist. Note that different etch chemistries
can be used to target each individual layer. Thus, the third etch
step my comprise three individual etch operations. The photoresist
can be removed using an ashing step. Note also that other layers
including interfacial layers can be used. Any interfacial layer
between layer 107 and 109, and 109 and 111 can be etched in turn.
Note that the fill material 122 functions as an etch mask, covering
and protecting a portion of the relief pattern 132. This process
essentially turns a line pattern into a trench pattern as an
opening or trench is formed within each line of the relief pattern
132. FIG. 6 illustrates an example result.
[0031] The fill material 122 can then be removed with a selective
plasma etch, wet etch, or developing chemistry. FIG. 7 illustrates
an example result. The resulting lines or structures now have a
width that is one fifth (1/5) of the initial thickness of
photoresist lines. Thus, each initial mandrel of five units in
length was split into two mandrels of one unit length, with a three
unit space between each new line.
[0032] The remaining (narrowed) structures can then be used as an
etch mask to transfer into layer 114, which can be a hardmask layer
(amorphous carbon, SiN, et cetera). Remaining structures from
relief pattern 132 can then be removed. An example result is shown
in FIG. 8. The result can include a pattern of lines having a new
pitch of 4 units, with lines having a width of one unit while
spaces have a width of three units. The line-to-space ratio is thus
1:3. At this point, any of various microfabrication steps can then
be continued. For example, the new lines formed in the hardmask
material can be used as a mandrel in a self-aligned double
patterning (SADP) process.
[0033] In additional steps, the resulting pattern is transferred
into an underlying layer, which can include two underlying layers
(layer 116 and layer 118). The etch mask of layer 114 can then be
removed. An example result is illustrated in FIG. 9. Note that
relief pattern 135 includes lines that form a bilayer mandrel.
[0034] The bilayer mandrels can then be used for sidewall spacer
formation. For example, a conformal deposition is executed, such as
an ALD oxide conformal coat. An example result is shown in FIG. 10.
This conformal coat deposits a film of approximately equal
thickness on all surfaces.
[0035] The conformal deposition can be followed by a spacer open
etch to remove spacer material (such as silicon dioxide) from
horizontal surfaces. An example result is shown in FIG. 11, which
shows sidewall spacers 137 now on two-layer mandrels, with spaces
between sidewall spacers.
[0036] A second fill material can then be deposited on the
substrate. FIG. 12 illustrates fill material 142 filling spacers
between sidewall spacers 137. An example fill material is spin-on
amorphous carbon overfill or organic planarization layer. Any
overburden from deposition can be etched back to uncover sidewall
spacers and mandrels.
[0037] The substrate is then planarized by chemical-mechanical
polishing (CMP). The lower layer of the two-layer/bi-layer mandrel
can be selected as a CMP stop material, such as silicon nitride. A
CMP stop material is a material that resists CMP planarization and
functions as an effective material for stopping a CMP process. An
example result is shown in FIG. 13. Note that the resulting pattern
on the substrate can be a multi-line layer having a planar top
surface and a repeating pattern of materials of different etch
resistivities, without any top rounding of materials.
Alternatively, the substrate can be etched to expose the hardmask
mandrel. The result can be alternating lines of amorphous carbon
and SiN with spacer silicon oxide in between.
[0038] Any further steps can be continued from this point. For
example, spacer oxide material can be removed via etch (FIG. 14).
Alternatively, the CMP stop material and fill material 142 can both
be removed, leaving a pattern of lines and spaces at a 1:1 ratio,
all of a same material. In another option, an etch mask can be
formed on top of the multi-line layer, and/or the pattern can be
transferred into an underlying poly silicon layer.
[0039] Accordingly, one embodiment includes a method of patterning
a substrate. A substrate is received or formed having a first
relief pattern positioned on a stack of underlying layers. The
first relief pattern includes linear structures having three layers
of material. The three layers of material include a layer of
photoresist positioned on an anti-reflective coating layer. The
anti-reflective coating layer is positioned on a third layer. The
linear structures can have a first pitch that has a line-to-space
ratio of 5:3 in that lines have a cross-sectional line width of
five units while spaces have a cross-sectional space width of three
units.
[0040] A first etch operation is executed. This etch operation is
isotropic or non-directional and uses chemistry that selectively
etches the layer of photoresist without etching the anti-reflective
coating layer, without etching the third layer, and without etching
the stack of underlying layers. This isotropic etch operation
results in the layer of photoresist being, at least, laterally
etched from an initial width of lines to a resulting width of
lines. Height can also decrease with uniform etching. The resulting
width of lines is less than the initial width of lines. This layer
of photoresist can be laterally etched such that a resulting width
of lines of photoresist is equal to three fifths of an initial
width of lines of photoresist.
[0041] A fill material is deposited on the substrate that fills
spaces between structures of the first relief pattern, covers
horizontal top surfaces of the anti-reflective coating layer, and
leaves top surfaces of the layer of photoresist uncovered.
Depositing the fill material can include multiple steps. For
example, depositing the fill material can result in an overburden
of material, that completely covers the substrate and structures
thereon. The overburden, or amount above top surfaces of
structures, can be removed by an etch back process or acid based
diffusion process. A solubility-changing agent can be diffused a
predetermined depth into the fill material from a top surface of
the fill material, rendering this portion soluble to a particular
solvent. Diffusion can be driven by heat or light. Soluble portions
of the fill material can then be developed (removed) thereby
uncovering top surfaces of the layer of photoresist.
[0042] A second etch operation is executed that removes the layer
of photoresist and anisotropically etches uncovered portions of the
anti-reflective coating layer and the third layer. This essentially
forms a trench within a mandrel/line. The fill material is removed
from the substrate. A pattern defined by remaining portions of the
third layer is transferred into a fourth layer and into a fifth
layer, using the third layer and second layer as an etch mask. The
fourth layer is positioned below the third layer, and the fifth
layer positioned below the fourth layer. This pattern transfer
results in the fourth layer and the fifth layer forming bi-layer
mandrels. Sidewall spacers are then formed on the bi-layer
mandrels. A second fill material can be deposited on the substrate
that at least partially fills spaces defined between the sidewall
spacers on the bi-layer mandrels, the second fill material being
greater in height as compared to the fifth layer. In other words,
the second fill material is at least as thick as the fifth layer.
This second fill can also initially be an overburden deposition
that is recessed or etched back. The substrate is then planarized
by removing the fourth layer and removing material from the
sidewall spacers and the second fill material down to a top surface
of the fifth layer such that a multi-line layer is formed having a
planar surface at the top surface of the fifth layer. The fifth
layer can be selected as a material resistant to
chemical-mechanical planarization. Additional steps can optionally
be executed. The sidewall spacers can be removed from the
multi-line layer. An etch mask can be formed on the multi-line
layer. This etch mask defines openings that uncover segments of all
lines of the multi-line layer, and then uncovered portions of at
least one material from the multi-line layer can be etched. A sixth
layer positioned under the multi-line layer can be etched using the
multi-line layer and the etch mask as a combined etch mask.
[0043] Another embodiment includes a method of patterning a
substrate. A first relief pattern is formed on a stack of
underlying layers on a substrate. The first relief pattern includes
linear structures having three layers of material. The three layers
of material include a first layer positioned on a second layer, and
the second layer positioned on a third layer. The linear structures
are formed at a first pitch that has a line-to-space ratio of 5:3
in that lines have a cross-sectional line width of five units while
spaces have a cross-sectional space width of three units.
[0044] A first etch operation is executed that is isotropic and
uses chemistry that selectively etches the first layer without
etching the second layer, without etching the third layer, and
without etching the stack of underlying layers. The isotropic etch
operation results in the first layer being laterally etched
resulting in the cross-sectional line width of five units being
trimmed to a second cross-sectional line width of three units. A
fill material is deposited on the substrate that fills spaces
between structures of the first relief pattern, covers horizontal
top surfaces of the second layer, but leaves top surfaces of the
first layer uncovered. There can initially be an overburden that is
removed, or a bottom-up fill can be used. A second etch operation
is executed that removes the first layer and anisotropically etches
uncovered portions of the second layer and the third layer. The
fill material can be removed from the substrate and then a pattern
defined by remaining portions of the third layer is transferred
into a fourth layer and a fifth layer. The fourth layer is
positioned below the third layer, the fifth layer is positioned
below the fourth layer, resulting in the fourth layer and the fifth
layer forming bi-layer mandrels having a second pitch that has a
second line-to-space ratio of 1:3 in that bi-layer mandrels have a
second cross-sectional line width of one unit while spaces defined
between bi-layer mandrels have a second cross-sectional space width
of three units. The fifth layer can be selected as a material
resistant to chemical-mechanical planarization.
[0045] Sidewall spacers can be formed on the bi-layer mandrels. A
second fill material is deposited on the substrate that at least
partially fills spaces defined between the sidewall spacers on the
bi-layer mandrels. The second fill material is greater in height as
compared to the fifth layer. The substrate is planarized by
removing the fourth layer and removing material from the sidewall
spacers and the second fill material down to a top surface of the
fifth layer such that a multi-line layer is formed having a planar
surface at the top surface of the fifth layer. Sidewall spacers can
be removed from the multi-line layer. Remaining lines on the
multi-line layer have a third line-to-space ratio of 1:1 in that
each remaining line is one unit wide while each remaining space is
one unit wide. An additional etch mask can be formed on the
multi-line layer defining openings that uncover segments of all
lines of the multi-line layer. Uncovered portions of at least one
material can be etched from the multi-line layer. A sixth layer
positioned under the multi-line layer can be etched with the
multi-line layer and the etch mask used as a combined etch
mask.
[0046] Another embodiment includes a method of patterning a
substrate. A substrate is received having a first relief pattern
formed on a stack of underlying layers. This substrate can be
received in a semiconductor processing tool, such as an etch
chamber. It can be received after forming and patterning layers
using various semiconductor manufacturing tools such as
coater-developer, furnace, scanner, plasma-based etch, and
deposition tools. The first relief pattern includes linear
structures having at least two layers of material. The two layers
of material include a first layer positioned on a second layer. The
linear structures have a first pitch that has a line-to-space ratio
of 5:3 in that lines have a cross-sectional line width of five
units while spaces have a cross-sectional space width of three
units
[0047] A first etch operation is executed that is isotropic and
uses chemistry that selectively etches the first layer without
etching the second layer and without etching the stack of
underlying layers. The isotropic etch operation results in the
first layer being at least laterally etched from an initial width
of lines to a resulting width of lines, the resulting width of
lines being less than the initial width of lines. A resulting width
of lines of the first layer is equal to three fifths of an initial
width of lines of the first layer.
[0048] A fill material is deposited on the substrate that fills
spaces between structures of the first relief pattern and covers
horizontal top surfaces of the second layer, but leaves top
surfaces of the first layer. A second etch operation is executed
that removes the first layer and anisotropically etches uncovered
portions of the second layer. The fill material is removed from the
substrate and then a pattern defined by remaining portions of the
second layer is transferred into a third layer. The third layer is
positioned below the second layer, resulting in the third layer
forming mandrels for sidewall spacers. Sidewall spacers can be
formed on the mandrels, and then the mandrels can be removed from
the substrate.
[0049] Note that various materials can be used for a given layer.
Example materials can include photoresist, silicon-containing
anti-reflective coating, SiON, amorphous carbon, silicon nitride,
silicon oxide, hardmask materials, and metal-containing materials,
such as titanium nitride. Also note that many variations of
techniques are contemplated herein. For example, the initial relief
pattern can have two layers instead of three. The top layer is then
slimmed to define a width to remove from the underlying mandrel. In
other words, to define a trench to form within a line to increase
pitch density.
[0050] Accordingly, techniques herein provide desirable pitch
spacing and square spacer profiles to improve LER and LWR.
[0051] 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.
[0052] 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. Labels such as "first," "second," et cetera, may be
used to distinguish elements and processes. Note that these are
merely labels and do not convey position, order, sequence, and so
forth unless explicitly indicated or apparent from dependency.
[0053] "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.
[0054] 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.
* * * * *