U.S. patent application number 15/403285 was filed with the patent office on 2018-07-12 for stress induction in 3d device channel using elastic relaxation of high stress material.
The applicant listed for this patent is INTERNATIONAL BUSINESS MACHINES CORPORATION. Invention is credited to Kangguo Cheng, Nicolas J. Loubet, Xin Miao, Alexander Reznicek.
Application Number | 20180197992 15/403285 |
Document ID | / |
Family ID | 62750324 |
Filed Date | 2018-07-12 |
United States Patent
Application |
20180197992 |
Kind Code |
A1 |
Cheng; Kangguo ; et
al. |
July 12, 2018 |
STRESS INDUCTION IN 3D DEVICE CHANNEL USING ELASTIC RELAXATION OF
HIGH STRESS MATERIAL
Abstract
A method for inducing stress in a device channel includes
forming a stress adjustment layer on a substrate, the stress
adjustment layer including an as deposited stress due to crystal
lattice differences with the substrate. A device channel layer is
formed on the stress adjustment layer. Cuts are etched through the
device channel layer and the stress adjustment layer to release the
stress adjustment layer to induce stress in the device channel
layer. Source/drain regions are formed adjacent to the device
channel layer.
Inventors: |
Cheng; Kangguo;
(Schenectady, NY) ; Loubet; Nicolas J.;
(Guilderland, NY) ; Miao; Xin; (Guilderland,
NY) ; Reznicek; Alexander; (Troy, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTERNATIONAL BUSINESS MACHINES CORPORATION |
Armonk |
NY |
US |
|
|
Family ID: |
62750324 |
Appl. No.: |
15/403285 |
Filed: |
January 11, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 29/0847 20130101;
H01L 29/66795 20130101; B82Y 10/00 20130101; H01L 29/7849 20130101;
H01L 29/0665 20130101; H01L 29/7848 20130101; H01L 29/66439
20130101; H01L 29/785 20130101; H01L 29/775 20130101; H01L 21/30604
20130101; H01L 29/0673 20130101; H01L 29/1054 20130101 |
International
Class: |
H01L 29/78 20060101
H01L029/78; H01L 29/06 20060101 H01L029/06; H01L 21/306 20060101
H01L021/306; H01L 29/66 20060101 H01L029/66 |
Claims
1. A method for inducing stress in a device channel, comprising:
forming a stress adjustment layer, formed from a material including
silicon phosphide (Si.sub.3P.sub.4), on a substrate, the stress
adjustment layer including an as deposited stress due to crystal
lattice differences with the substrate; forming a device channel
layer on the stress adjustment layer; etching cuts though the
device channel layer and the stress adjustment layer to release the
stress adjustment layer to induce stress in the device channel
layer and form a fin such that the stress adjustment layer extends
through the fin from the device channel layer to the substrate; and
forming source/drain regions adjacent to the device channel
layer.
2. The method as recited in claim 1, wherein the stress adjustment
layer includes a tensile stress to form a compressive stress in the
device channel layer.
3. (canceled)
4. The method as recited in claim 1, wherein the device channel
layer includes a material selected from the group consisting of
silicon (Si) and silicon germanium (SiGe).
5. The method as recited in claim 1, wherein forming the
source/drain regions adjacent to the device channel layer includes
forming stressed source/drain regions to externally provide
additional stress to the device channel layer.
6. The method as recited in claim 1, wherein the device channel
layer includes a fin.
7. The method as recited in claim 1, wherein the device channel
layer includes layers in a nanosheet.
8. A method for inducing stress in a device channel, comprising:
forming a stress adjustment layer, formed from a material including
silicon phosphide (Si.sub.3P.sub.4), on a substrate, the stress
adjustment layer including an as deposited stress due to crystal
lattice differences with the substrate; forming a device channel
layer on the stress adjustment layer; forming fins in the device
channel layer on the stress adjustment layer such that the stress
adjustment layer extends through the fin from the device channel
layer to the substrate; forming gate structures transversely over
the fins; etching cuts though the device channel layer and the
stress adjustment layer on sides of the gate structures to release
the stress adjustment layer to induce stress in the device channel
layer; and forming source/drain regions adjacent to the device
channel layer.
9. The method as recited in claim 8, wherein the stress adjustment
layer includes a tensile stress to form a compressive stress in the
device channel layer.
10. (canceled)
11. The method as recited in claim 8, wherein the device channel
layer includes a material selected from the group consisting of
silicon (Si) and silicon germanium (SiGe).
12. The method as recited in claim 8, wherein forming the
source/drain regions adjacent to the device channel layer includes
forming stressed source/drain regions to externally provide
additional stress to the device channel layer.
13. The method as recited in claim 8, wherein the device channel
layer includes a multi-layered nanosheet including alternating
layers of channel layers and stress adjustment layers.
14. The method as recited in claim 13, further comprising forming a
protection layer along sidewalls of the fins before forming the
source/drain regions.
15. The method as recited in claim 13, further comprising:
recessing the alternating stress adjustment layers and the stress
adjustment layer; and depositing a dielectric material in the
recesses to protect sidewalls of the fins before forming the
source/drain regions.
16. The method as recited in claim 13, further comprising: removing
the alternating stress adjustment layers and the stress adjustment
layer to form a void and to expose the alternating channel layers
such that the alternating channel layers are clamped between the
source/drain regions to maintain stress; and forming gate material
to fill the void.
17. A semiconductor device having compressive stress in a device
channel, comprising: a stress adjustment layer, formed from a
material including silicon phosphide (Si.sub.3P.sub.4), formed on a
substrate; a device channel layer formed on the stress adjustment
layer, the device channel layer including a compressive stress
induced by stress relaxation of the stress adjustment layer, which
includes tensile stress from an as deposited stress provided from
crystal lattice differences with the substrate and the stress
adjustment layer and the device channel layer forming a fin such
that the stress adjustment layer extends through the fin from the
device channel layer to the substrate; and source/drain regions
formed adjacent to the device channel layer.
18. The device as recited in claim 17, wherein the device channel
layer includes a material selected from the group consisting of
silicon (Si) and silicon germanium (SiGe).
19. The device as recited in claim 17, wherein the source/drain
regions externally provide additional stress to the device channel
layer.
20. The method as recited in claim 17, wherein the device channel
layer includes a fin or layers in a nanosheet.
Description
BACKGROUND
Technical Field
[0001] The present invention generally relates to semiconductor
devices, and more particularly to substrates and methods for
fabrication that yield a compressive strain employed for formation
of semiconductor devices.
Description of the Related Art
[0002] As the device density increases, greater challenges for use
of traditional external stressors in channel materials exist. A
relaxed SiGe buffer can be used to induce tensile stress in silicon
but no clear equivalent solution for compressive stress exists.
SiGe layers can be very defective if above a critical thickness,
implanted or subjected to a high thermal budget.
[0003] Strained silicon and strained silicon-on-insulator (SOI) can
provide enhanced properties for semiconductor devices. For example,
p-type field effect transistors (PFETs) have improved performance
when formed with a compressive strain channel, and n-type field
effect transistors (NFETs) have improved performance when formed
with a tensile strain channel. Tensile strain devices are easily
formed using, e.g., relaxed SiGe buffer layers or SiGe
condensation. Compressively strained silicon is much more difficult
to achieve.
SUMMARY
[0004] In accordance with an embodiment of the present invention, a
method for inducing stress in a device channel includes forming a
stress adjustment layer on a substrate, the stress adjustment layer
including an as deposited stress due to crystal lattice differences
with the substrate. A device channel layer is formed on the stress
adjustment layer. Cuts are etched through the device channel layer
and the stress adjustment layer to release the stress adjustment
layer to induce stress in the device channel layer. Source/drain
regions are formed adjacent to the device channel layer.
[0005] Another method for inducing stress in a device channel
includes forming a stress adjustment layer on a substrate, the
stress adjustment layer including an as deposited stress due to
crystal lattice differences with the substrate; forming a device
channel layer on the stress adjustment layer; forming fins in the
device channel layer on the stress adjustment layer; forming gate
structures transversely over the fins; etching cuts though the
device channel layer and the stress adjustment layer on sides of
the gate structures to release the stress adjustment layer to
induce stress in the device channel layer; and forming source/drain
regions adjacent to the device channel layer.
[0006] A semiconductor device having compressive stress in a device
channel includes a stress adjustment layer formed on a substrate. A
device channel layer is formed on the stress adjustment layer. The
device channel layer includes a compressive stress induced by
stress relaxation of the stress adjustment layer, which includes
tensile stress from an as deposited stress provided from crystal
lattice differences with the substrate. Source/drain regions are
formed adjacent to the device channel layer.
[0007] These and other features and advantages will become apparent
from the following detailed description of illustrative embodiments
thereof, which is to be read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The following description will provide details of preferred
embodiments with reference to the following figures wherein:
[0009] FIG. 1 is a cross-sectional view taken parallel to fins to
be formed showing a device channel layer and a stress adjustment
layer formed on a substrate in accordance with an embodiment of the
present invention;
[0010] FIG. 2 is a cross-sectional view taken perpendicular to fins
to be formed showing a device channel layer and a stress adjustment
layer formed on a substrate in accordance with an embodiment of the
present invention;
[0011] FIG. 3 is a cross-sectional view taken parallel to fins
showing the device channel layer and the stress adjustment layer
formed on the substrate in accordance with an embodiment of the
present invention;
[0012] FIG. 4 is a cross-sectional view taken perpendicular to fins
showing the fins etched into the device channel layer and the
stress adjustment layer in accordance with an embodiment of the
present invention;
[0013] FIG. 5 is a cross-sectional view taken parallel to fins
showing dummy gate structures formed over the fins in accordance
with an embodiment of the present invention;
[0014] FIG. 6 is a schematic top view showing section lines for
parallel and perpendicular fin views in accordance with an
embodiment of the present invention;
[0015] FIG. 7 is a cross-sectional view taken parallel to fins
showing cuts through the fins to release stress in the stress
adjustment layer and induce stress in the device channel layer in
accordance with an embodiment of the present invention;
[0016] FIG. 8 is a cross-sectional view of FIG. 7 taken
perpendicular to the fins in accordance with an embodiment of the
present invention;
[0017] FIG. 9 is a cross-sectional view taken parallel to fins
showing source and drain regions formed in accordance with an
embodiment of the present invention;
[0018] FIG. 10 is a cross-sectional view of FIG. 9 taken
perpendicular to the fins showing source and drain regions formed
in accordance with an embodiment of the present invention;
[0019] FIG. 11 is a cross-sectional view taken parallel to fins to
be formed showing device channel layers and stress adjustment
layers of a nanosheet structure formed on a substrate in accordance
with an embodiment of the present invention;
[0020] FIG. 12 is a cross-sectional view taken perpendicular to
fins to be formed showing device channel layers and stress
adjustment layers of the nanosheet structure formed on the
substrate in accordance with an embodiment of the present
invention;
[0021] FIG. 13 is a cross-sectional view taken parallel to fins
showing the device channel layers and the stress adjustment layers
of the nanosheet structure formed on the substrate in accordance
with an embodiment of the present invention;
[0022] FIG. 14 is a cross-sectional view taken perpendicular to
fins showing the fins etched through the device channel layers and
the stress adjustment layers of the nanosheet structure in
accordance with an embodiment of the present invention;
[0023] FIG. 15 is a cross-sectional view taken parallel to fins
showing dummy gate structures formed over the fins in accordance
with an embodiment of the present invention;
[0024] FIG. 16 is a cross-sectional view taken parallel to fins
showing cuts through the fins to release stress in the stress
adjustment layers and induce stress in the device channel layers in
accordance with an embodiment of the present invention;
[0025] FIG. 17 is a cross-sectional view of FIG. 16 taken
perpendicular to the fins in accordance with an embodiment of the
present invention;
[0026] FIG. 18 is a cross-sectional view taken parallel to fins
showing source and drain regions formed over a protection layer in
accordance with an embodiment of the present invention;
[0027] FIG. 19 is a cross-sectional view of FIG. 18 taken
perpendicular to the fins showing source and drain regions formed
in accordance with an embodiment of the present invention;
[0028] FIG. 20 is a cross-sectional view taken parallel to fins
showing etch back of stress adjustment layers and formation of
dielectric material for protection in accordance with another
embodiment of the present invention;
[0029] FIG. 21 is a cross-sectional view of FIG. 18 taken parallel
to the fins showing source and drain regions formed in accordance
with an embodiment of the present invention;
[0030] FIG. 22 is a cross-sectional view taken parallel to fins
showing a dielectric fill formed and dummy gate materials exposed
by planarization in accordance with an embodiment of the present
invention;
[0031] FIG. 23 is a cross-sectional view of FIG. 22 taken
perpendicular to the fins showing the dielectric fill formed in
accordance with an embodiment of the present invention;
[0032] FIG. 24 is a cross-sectional view taken parallel to fins
showing the dummy gate and the stress adjustment layers selectively
removed to expose the device channel layers in accordance with an
embodiment of the present invention;
[0033] FIG. 25 is a cross-sectional view of FIG. 24 taken
perpendicular to the fins showing the dielectric fill formed in
accordance with an embodiment of the present invention;
[0034] FIG. 26 is a cross-sectional view taken parallel to fins
showing a gate stack formed in a void in accordance with an
embodiment of the present invention; and
[0035] FIG. 27 is a cross-sectional view of FIG. 26 taken
perpendicular to the fins showing the dielectric fill formed in
accordance with an embodiment of the present invention.
DETAILED DESCRIPTION
[0036] In accordance with aspects of the present invention, methods
and structures are provided to form compressively strained
structures. In some embodiments, one or more semiconductor layers
or fin structures are rendered compressive. In one example,
compressive properties can be applied to a semiconductor layer when
a compound is inserted into a lattice of the semiconductor material
to alter a lattice constant of the semiconductor material. The
compound can include a material that is a crystalline compound and
is preferably chemically bound with the material of the lattice.
The compound can thus form a semiconductor crystal within a
semiconductor matrix and affect the lattice constant of the overall
layer.
[0037] In one embodiment, a tensily strained layer can be formed on
a substrate to induce tension in an adjacent layer (e.g., device
channel). The tensily strained layer may include Si.sub.3P.sub.4 on
Si or SiC on Si, although other material combinations may be
employed. The tensily strained layer is layered on the adjacent
layer. The adjacent layer and the tensily strained layer are etched
to elastically release the tensily strained layer to induce a
compressive strain into the adjacent layer. The etched tensily
strained layer and the adjacent layer can form a fin or form a
channel region for another type of the field effect transistor
(FET) device.
[0038] It is to be understood that aspects of the present invention
will be described in terms of a given illustrative architecture;
however, other architectures, structures, substrate materials and
process features and steps can be varied within the scope of
aspects of the present invention.
[0039] It will also be understood that when an element such as a
layer, region or substrate is referred to as being "on" or "over"
another element, it can be directly on the other element or
intervening elements can also be present. In contrast, when an
element is referred to as being "directly on" or "directly over"
another element, there are no intervening elements present. It will
also be understood that when an element is referred to as being
"connected" or "coupled" to another element, it can be directly
connected or coupled to the other element or intervening elements
can be present. In contrast, when an element is referred to as
being "directly connected" or "directly coupled" to another
element, there are no intervening elements present.
[0040] The present embodiments can include a design for an
integrated circuit chip, which can be created in a graphical
computer programming language, and stored in a computer storage
medium (such as a disk, tape, physical hard drive, or virtual hard
drive such as in a storage access network). If the designer does
not fabricate chips or the photolithographic masks used to
fabricate chips, the designer can transmit the resulting design by
physical means (e.g., by providing a copy of the storage medium
storing the design) or electronically (e.g., through the Internet)
to such entities, directly or indirectly. The stored design is then
converted into the appropriate format (e.g., GDSII) for the
fabrication of photolithographic masks, which typically include
multiple copies of the chip design in question that are to be
formed on a wafer. The photolithographic masks are utilized to
define areas of the wafer (and/or the layers thereon) to be etched
or otherwise processed.
[0041] Methods as described herein can be used in the fabrication
of integrated circuit chips. The resulting integrated circuit chips
can be distributed by the fabricator in raw wafer form (that is, as
a single wafer that has multiple unpackaged chips), as a bare die,
or in a packaged form. In the latter case, the chip is mounted in a
single chip package (such as a plastic carrier, with leads that are
affixed to a motherboard or other higher level carrier) or in a
multichip package (such as a ceramic carrier that has either or
both surface interconnections or buried interconnections). In any
case, the chip is then integrated with other chips, discrete
circuit elements, and/or other signal processing devices as part of
either (a) an intermediate product, such as a motherboard, or (b)
an end product. The end product can be any product that includes
integrated circuit chips, ranging from toys and other low-end
applications to advanced computer products having a display, a
keyboard or other input device, and a central processor.
[0042] It should also be understood that material compounds will be
described in terms of listed elements. These compounds include
different proportions of the elements within the compound. In
addition, other elements can be included in the compound and still
function in accordance with the present principles. The compounds
with additional elements will be referred to herein as alloys.
[0043] Reference in the specification to "one embodiment" or "an
embodiment", as well as other variations thereof, means that a
particular feature, structure, characteristic, and so forth
described in connection with the embodiment is included in at least
one embodiment. Thus, the appearances of the phrase "in one
embodiment" or "in an embodiment", as well any other variations,
appearing in various places throughout the specification are not
necessarily all referring to the same embodiment.
[0044] It is to be appreciated that the use of any of the following
"/", "and/or", and "at least one of", for example, in the cases of
"A/B", "A and/or B" and "at least one of A and B", is intended to
encompass the selection of the first listed option (A) only, or the
selection of the second listed option (B) only, or the selection of
both options (A and B). As a further example, in the cases of "A,
B, and/or C" and "at least one of A, B, and C", such phrasing is
intended to encompass the selection of the first listed option (A)
only, or the selection of the second listed option (B) only, or the
selection of the third listed option (C) only, or the selection of
the first and the second listed options (A and B) only, or the
selection of the first and third listed options (A and C) only, or
the selection of the second and third listed options (B and C)
only, or the selection of all three options (A and B and C). This
can be extended, as readily apparent by one of ordinary skill in
this and related arts, for as many items listed.
[0045] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
example embodiments. As used herein, the singular forms "a," "an"
and "the" are intended to include the plural forms as well, unless
the context clearly indicates otherwise. It will be further
understood that the terms "comprises," "comprising," "includes"
and/or "including," when used herein, specify the presence of
stated features, integers, steps, operations, elements and/or
components, but do not preclude the presence or addition of one or
more other features, integers, steps, operations, elements,
components and/or groups thereof.
[0046] Spatially relative terms, such as "beneath," "below,"
"lower," "above," "upper," and the like, can be used herein for
ease of description to describe one element's or feature's
relationship to another element(s) or feature(s) as illustrated in
the FIGS. It will be understood that the spatially relative terms
are intended to encompass different orientations of the device in
use or operation in addition to the orientation depicted in the
FIGS. For example, if the device in the FIGS. is turned over,
elements described as "below" or "beneath" other elements or
features would then be oriented "above" the other elements or
features. Thus, the term "below" can encompass both an orientation
of above and below. The device can be otherwise oriented (rotated
90 degrees or at other orientations), and the spatially relative
descriptors used herein can be interpreted accordingly. In
addition, it will also be understood that when a layer is referred
to as being "between" two layers, it can be the only layer between
the two layers, or one or more intervening layers can also be
present.
[0047] It will be understood that, although the terms first,
second, etc. can be used herein to describe various elements, these
elements should not be limited by these terms. These terms are only
used to distinguish one element from another element. Thus, a first
element discussed below could be termed a second element without
departing from the scope of the present concept.
[0048] Referring now to the drawings in which like numerals
represent the same or similar elements and initially to FIGS. 1 and
2, a substrate system 10 is illustratively depicted in
cross-section where the cross-section is taken parallel (\\) to the
fins that will be formed. FIG. 2 shows the substrate system 10
illustratively depicted in cross-section where the cross-section is
taken perpendicular (.perp.) to the fins that will be formed.
[0049] The substrate system 10 includes a substrate 12 and a strain
adjustment layer 14. The strain adjustment layer 14 is formed on
the substrate 12 and includes an as deposited material that
includes a different out of plane lattice parameter than the
substrate 12. In particularly useful embodiments, the strain
adjustment layer 14 includes a tensile stress/strain to induce a
compressive strain in an adjacent or nearly adjacent device channel
layer 16 as will be described. However, it should be understood
that the present embodiments can apply to compressive materials to
induce tensile stress/strains.
[0050] In one embodiment, the substrate 12 can include a
silicon-based material, and, in particular, monocrystalline silicon
(Si). The substrate 12 is not limited to monocrystalline forms of
Si as other materials and multi-layers thereof may be employed.
[0051] Strain adjustment layer 14 is preferably formed on the
substrate 12 by epitaxial growth. In one embodiment, strain
adjustment layer 14 includes silicon phosphide (Si.sub.3P.sub.4) or
silicon carbide (SiC). The strain adjustment layer 14 can be formed
without relaxation. In one embodiment, the Si.sub.3P.sub.4 can be
employed and include a thickness of about 50 nm or more while
maintaining its tensile properties. Pseudocubic Si.sub.3P.sub.4 is
a semiconductor with narrow bandgap material that has a much
smaller lattice (a) than silicon (a.sub.Si3P4=4.961 angstroms
versus a.sub.Si=5.431 angstroms). Si.sub.3P.sub.4 can be grown by
epitaxy at low temperatures (e.g., less than about 700 degrees C.).
A very high stress can be achieved as a blanket deposited layer 14
(e.g., greater than 1.6 GPa can be achieved).
[0052] The strain adjustment layer 14 is deposited on the substrate
12 with a smaller out of plane lattice parameter to eventually
result in the inducement of a compressive stress/strain in the
device channel layer 16. The device channel layer 16 is epitaxially
grown on the strain adjustment layer 14, and can include the same
material or a different material than the substrate 12. In one
embodiment, the device channel layer 16 includes silicon (Si),
silicon germanium (SiGe) or other crystalline materials.
[0053] A hard mask 18 is formed on the device channel layer 16. The
hard mask 18 may include a nitride, such as, e.g., SiN, although
other materials or multilayers may be employed.
[0054] Referring to FIGS. 3 and 4, the cross-section of FIG. 3 is
taken parallel (\\) to a fin 20, and the cross-section of FIG. 4 is
taken perpendicular (.perp.) to the fins 20 that will be formed.
Fins 20 are formed by patterning an etch mask (not shown) over the
hard mask 18. The etch mask can include a photoresist or employ
other patterning techniques, e.g., spacer image transfer, or the
like. A reactive ion etch (RIE) or other etch process is performed
to etch the device channel layer 16, the strain adjustment layer 14
and to etch slightly into the substrate 12. The hard mask 18 can be
selectively removed during or after the etch process.
[0055] In FIG. 4, a dielectric layer 25 can be employed as a
shallow trench isolation region between the fins 20. The dielectric
layer 25 can be formed by blanket deposition of a dielectric (e.g.,
SiOx) everywhere on the wafer, planarization and recessing the
dielectric 25 between the fins 20.
[0056] Referring to FIG. 5, dummy gate structures 22 are formed
over the fins 20. The dummy gate structures 22 include a dummy gate
oxide 23, a dummy gate 24, a gate cap 26 and a dielectric layer 28.
The dummy gate oxide 23 can include a thermal or deposited oxide
formed on the device channel layer 16. The dummy gate 24 can
include polysilicon or amorphous silicon. The gate cap 26 can
include silicon nitride, and the dielectric layer 28 can include
silicon oxide. Other materials and multiple layers may also be
employed. After the deposition of the dummy gate materials, a
patterning process is employed to form the gate structures 22 by
etching the dummy gate materials. The dummy gate structures 22 are
formed perpendicularly to the fins 20.
[0057] Referring to FIG. 6, a schematic top view shows section
lines for parallel to fins (\\ Fins) and perpendicular to fins
(.perp. Fins) are shown for illustrative purposes. Gate structures
22, 46 are depicted transversely to the fins 22, 46.
[0058] Referring to FIGS. 7 and 8, a conformal spacer layer
deposition is performed followed by a RIE process to form spacers
30. The spacers 30 can include silicon nitride or low K materials
(e.g., SiBCN, SiOCN, SiON) although other suitable spacer materials
can be employed. Using the dummy gate structures 22 and spacers 30
as an etch mask, an anisotropic etch process (e.g., RIE) is
employed to cut the fins 20. The etch process etches through the
device channel layer 16, the strain adjustment layer 14 and stops
within the substrate 12 to ensure that the strain adjustment layer
14 is completely cut through. The strain adjustment layer 14 then
begins to relax in the direction of arrows 32. This begins to
induce stress/strain to the device channel layer 16 in contact with
the strain adjustment layer 14. The remaining portions of the
device channel layer 16 form a channel for a finFET device and are
under compressive strain. The use of the compressive strain channel
provides a benefit for p-type FET devices. In FIG. 8, the fin cut
removes portions of the fins 20 down to the substrate and leaves
trenches 36 through the dielectric layer 25.
[0059] Referring to FIGS. 9 and 10, source/drain (S/D) regions 38
are formed. The S/D regions 38 can be epitaxially grown. In one
useful embodiment, the S/D regions 38 can include materials that
provide additional compressive stress (shown by arrows 35) in the
channel region (adjacent layer 16). In one embodiment, the S/D
regions 38 can include, e.g., boron doped silicon or SiGe:B to
provide an additional external stressor.
[0060] Referring to FIGS. 11 and 12, a stacked nanosheet system 40
is illustratively depicted in cross-section in FIG. 11 where the
cross-section is taken parallel (\\) to the fins that will be
formed. FIG. 12 shows the stacked nanosheet system 40
illustratively depicted in cross-section where the cross-section is
taken perpendicular (.perp.) to the fins that will be formed.
[0061] A stacked nanosheet 42 is formed or provided on the strain
adjustment layer 14, which is formed on the substrate 12. The
strain adjustment layer 14 is formed on the substrate 12 and
includes an "as deposited" material that includes a different out
of plane lattice parameter than the substrate 12. In particularly
useful embodiments, the strain adjustment layer 14 includes a
tensile stress/strain to induce a compressive strain in the
nanosheet 42, as will be described. However, it should be
understood that the present embodiments can apply to compressive
material to induce tensile stress/strain as well.
[0062] In one embodiment, the substrate 12 can include a
silicon-based material, and, in particular, monocrystalline silicon
(Si). The substrate 12 is not limited to monocrystalline forms of
Si as other materials and multi-layers thereof may be employed. In
one embodiment, the stacked nanosheet 42 can include stacked
nanowires instead of a sheet.
[0063] Strain adjustment layer 14 is preferably formed on the
substrate 12 by epitaxial growth. In one embodiment, strain
adjustment layer 14 includes Si.sub.3P.sub.4 or SiC. The strain
adjustment layer 14 can be formed without relaxation. In one
embodiment, the Si.sub.3P.sub.4 can be employed and include a
thickness of about 50 nm or more while maintaining its tensile
properties. The strain adjustment layer 14 is deposited on the
substrate 12 with a smaller out of plane lattice parameter to
eventually result in the inducement of a compressive stress/strain
in the device channel layer 16. The nanosheet 42 is epitaxially
grown and provided on the strain adjustment layer 14. The nanosheet
42 includes alternating layers 16, 17 of monocrystalline materials.
Layers 16 can include the same material or a different material
than the substrate 12. Layers 16 will eventually form a compressed
device channel. In one embodiment, the layers 16 include silicon
(Si), silicon germanium (SiGe) or other crystalline materials.
Layers 17 of the nanosheet 42 may include the same material as the
strain adjustment layer 14 (e.g., Si.sub.3P.sub.4, SiC). A hard
mask 18 is formed on the nanosheet 42. The hard mask 18 may include
a nitride, such as, e.g., SiN, although other materials or
multilayers may be employed.
[0064] Referring to FIGS. 13 and 14, the cross-section of FIG. 13
is taken parallel (\\) to a fin 44, and the cross-section of FIG.
14 is taken perpendicular (.perp.) to the fins 44 that will be
formed. Fins 44 are formed by patterning an etch mask (not shown)
over the hard mask 18. The etch mask can include a photoresist or
employ other patterning techniques, e.g., spacer image transfer, or
the like. A RIE or other etch process is performed to etch the
nanosheet 42, to etch the strain adjustment layer 14 and to etch
slightly into the substrate 12. The hard mask 18 can be selectively
removed during or after the etch process.
[0065] In FIG. 14, a dielectric layer 55 can be employed as a
shallow trench isolation region between the fins 44. The dielectric
layer 55 can be formed by blanket deposition of a dielectric (e.g.,
SiOx) everywhere on the wafer, planarization and recess between the
fins 20.
[0066] Referring to FIG. 15, dummy gate structures 46 are formed
over the fins 44. The dummy gate structures 46 include a dummy gate
oxide 23, a dummy gate 48, a gate cap 50 and a dielectric layer 52.
The dummy gate oxide 23 can include a thermal oxide formed on a top
most layer of the nanosheet 42. The dummy gate 48 can include
polysilicon or amorphous silicon. The gate cap 50 can include
silicon nitride, and the dielectric layer 52 can include silicon
oxide. Other materials and multiple layers may also be employed.
After the deposition of the dummy gate materials, a patterning
process is employed to form the gate structures 46 by etching the
dummy gate materials. The dummy gate structures 46 are formed
perpendicularly to the fins 44.
[0067] Referring to FIGS. 16 and 17, a conformal spacer layer
deposition is performed followed by a RIE process to form spacers
56. The spacers 56 can include silicon nitride, although other
suitable spacer materials can be employed. Using the dummy gate
structures 46 and spacers 56 as an etch mask, an anisotropic etch
process (e.g., RIE) is employed to cut the fins 44. The etch
process etches through the nanosheet 42, the strain adjustment
layer 14 and stops within the substrate 12 to ensure that the
strain adjustment layer 14 is completely cut through. The strain
adjustment layer 14 and layers 17 then begin to relax in the
direction of arrows 58. This begins to induce stress/strain to the
layers 16 in contact with the strain adjustment layer 14 and layers
17. The remaining portions of the layers 16 form a channel for a
finFET device and are under compressive strain. The use of the
compressive strain channel provides a benefit for p-type FET
devices.
[0068] In one embodiment, a thin protective liner 54 is deposited
in contact with sidewalls of the fins 44 and over exposed surfaces
of the substrate 12. The thin protective liner 54 can include a
crystalline semiconductor material such as, e.g., silicon (Si). The
thin protective liner 54 may be omitted in favor of other
protective measures as will be described. The thin protective liner
54 prevents lateral etching into the fins 44 during the formation
of the nanosheets and final metal gate in the subsequent steps. In
FIG. 17, the fin cut removes portions of the fins 44 down to the
substrate 12 and leaves trenches 60 through the dielectric layer
55.
[0069] Referring to FIGS. 18 and 19, source/drain (S/D) regions 62
are formed. The S/D regions 62 can be epitaxially grown on the
substrate 12 and the protection layer 54. In one useful embodiment,
the S/D regions 62 can include a material that provides additional
compressive stress in the channel region 16. In one embodiment, the
S/D regions 62 can include, e.g., boron doped silicon or SiGe:B to
provide an additional external stressor.
[0070] Referring to FIG. 20, in another embodiment, instead of
forming the thin protective liner 54 and before forming S/D regions
62, a selective etch process is performed to etchback (recess)
lateral portions of the layers 17 and layer 14 of the fins 44. The
selective etch can include a wet or dry etch. Then, a dielectric
material 64 is deposited to provide gate isolation from the S/D
regions 62 to be formed by filling in the recessed regions. A RIE
or wet etch process is performed to remove the remaining dielectric
material 64 and leave behind dielectric material 64. The dielectric
material 64 prevents lateral etching into the fins 44 during the
formation of the nanosheets and final metal gate in the subsequent
steps. The dielectric material 64 can include a low dielectric
constant material (e.g., equal to or less than the dielectric
constant of silicon oxide) to provide preferred capacitance
characteristics between the gate and S/D regions.
[0071] Referring to FIG. 21, the S/D regions 62 can be epitaxially
grown. In one useful embodiment, the S/D regions 62 can include a
material that provides additional compressive stress in the channel
region (layers 16). In one embodiment, the S/D regions 62 can
include, e.g., boron doped silicon or SiGe:B to provide an
additional external stressor.
[0072] Referring to FIGS. 22 and 23, while the embodiments of
either FIG. 18 or FIG. 21 can be employed, additional processing
will be described in terms of the embodiments of FIG. 21. Such
processing is applicable to either embodiment.
[0073] A dielectric fill 66 is deposited over device to fill in
spaces between the gate structures 46. The dielectric fill 66 can
include a form of oxide, e.g., a silicon oxide, although any
suitable dielectric material can be employed. A planarization
process, such as, e.g., a chemical mechanical polish (CMP), is
performed to expose the dummy gate 48.
[0074] Referring to FIGS. 24 and 25, the dummy gate 48 and the
strain adjustment layers 14 and 17 are removed to form a void 70
and expose layers 16. The layers 16 extend between the S/D regions
62. The layers 16 are in effect clamped between the S/D regions 62.
There is little or no relaxation of the compressive stress in the
channel region (layers 16) as the channel region (layers 16) is
clamped by the S/D region epitaxy on both sides.
[0075] Referring to FIGS. 26 and 27, the layers 16 form a device
channel between S/D regions 62. The layers 16 have a gate
dielectric (not shown) formed thereon and the voids 70 are filled
with a conductive material 72 to form a gate electrode. The
conductive material 72 can include a metal (e.g., tungsten,
titanium, tantalum, ruthenium, zirconium, cobalt, copper, aluminum,
lead, platinum, tin, silver, gold), a conducting metallic compound
material (e.g., tantalum nitride, titanium nitride, tungsten
silicide, tungsten nitride, ruthenium oxide, cobalt silicide,
nickel silicide), carbon nanotube, conductive carbon, graphene, or
any suitable combination of these materials. The conductive
material may further comprise dopants that are incorporated during
or after deposition. Processing continues with the formation of
additional components and structures to complete the device, e.g.,
contacts, metal lines, etc.
[0076] Having described preferred embodiments for stress induction
in 3D device channels using elastic relaxation of high stress
material (which are intended to be illustrative and not limiting),
it is noted that modifications and variations can be made by
persons skilled in the art in light of the above teachings. It is
therefore to be understood that changes may be made in the
particular embodiments disclosed which are within the scope of the
invention as outlined by the appended claims. Having thus described
aspects of the invention, with the details and particularity
required by the patent laws, what is claimed and desired protected
by Letters Patent is set forth in the appended claims.
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