U.S. patent application number 16/004677 was filed with the patent office on 2019-12-12 for interfacial layer between fin and source/drain region.
The applicant listed for this patent is Taiwan Semiconductor Manufacturing Company, Ltd.. Invention is credited to Chih-Yun Chin, Tzu-Hsiang Hsu, Pei-Ren Jeng, Chien-Wei Lee, Yen-Ru Lee, Chii-Horng Li, Yan-Ting Lin, Davie Liu, Hsueh-Chang Sung, Roger Tai, Heng-Wen Ting.
Application Number | 20190378920 16/004677 |
Document ID | / |
Family ID | 68536163 |
Filed Date | 2019-12-12 |
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United States Patent
Application |
20190378920 |
Kind Code |
A1 |
Chin; Chih-Yun ; et
al. |
December 12, 2019 |
Interfacial Layer Between Fin and Source/Drain Region
Abstract
An embodiment is a semiconductor structure. The semiconductor
structure includes a substrate. A fin is on the substrate. The fin
includes silicon germanium. An interfacial layer is over the fin.
The interfacial layer has a thickness in a range from greater than
0 nm to about 4 nm. A source/drain region is over the interfacial
layer. The source/drain region includes silicon germanium.
Inventors: |
Chin; Chih-Yun; (Taichung
City, TW) ; Li; Chii-Horng; (Zhubei City, TW)
; Lee; Chien-Wei; (Kaohsiung City, TW) ; Sung;
Hsueh-Chang; (Zhubei City, TW) ; Ting; Heng-Wen;
(Pingtung County, TW) ; Tai; Roger; (Tainan City,
TW) ; Jeng; Pei-Ren; (Chu-Bei City, TW) ; Hsu;
Tzu-Hsiang; (Xinfeng Township, TW) ; Lee; Yen-Ru;
(Hsinchu City, TW) ; Lin; Yan-Ting; (Baoshan
Township, TW) ; Liu; Davie; (Tainan City,
TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Taiwan Semiconductor Manufacturing Company, Ltd. |
Hsinchu |
|
TW |
|
|
Family ID: |
68536163 |
Appl. No.: |
16/004677 |
Filed: |
June 11, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 29/66803 20130101;
H01L 29/785 20130101; H01L 29/165 20130101; H01L 21/823431
20130101; H01L 29/0847 20130101; H01L 29/66545 20130101; H01L
29/6681 20130101; H01L 29/66795 20130101; H01L 21/762 20130101 |
International
Class: |
H01L 29/78 20060101
H01L029/78; H01L 29/66 20060101 H01L029/66; H01L 29/08 20060101
H01L029/08; H01L 21/762 20060101 H01L021/762; H01L 21/8234 20060101
H01L021/8234; H01L 29/165 20060101 H01L029/165 |
Claims
1. A semiconductor structure comprising: a substrate; a fin on the
substrate, the fin comprising silicon germanium and having recessed
portions; an interfacial layer over the recessed portions of the
fin, the interfacial layer having a thickness in a range from about
1 nm to about 4 nm, wherein the interfacial layer encapsulates
impurities on a surface of the fin; and a source/drain region over
the interfacial layer, the source/drain region comprising silicon
germanium.
2. The semiconductor structure of claim 1, wherein the fin has a
germanium atomic percent content in a range from about 5% to about
40%.
3. The semiconductor structure of claim 1, wherein the source/drain
region comprises a germanium atomic percent content in a range from
about 25% to about 70%.
4. The semiconductor structure of claim 1, wherein the source/drain
region comprise a p-type dopant.
5. The semiconductor structure of claim 1, wherein the interfacial
layer has a surface roughness in a range from about 2 nm RMS or
less RMS.
6. (canceled)
7. The semiconductor structure of claim 1, wherein the interfacial
layer comprises silicon germanium.
8. The semiconductor structure of claim 7, wherein the interfacial
layer has a silicon atomic percent content in a range from about
90% to about 99.9%.
9. A method of manufacturing a semiconductor device, the method
comprising: forming a fin on a substrate; forming a gate structure
over the fin; forming a recess in the fin proximate the gate
structure; forming an interfacial layer in the recess, the
interfacial layer comprising silicon germanium, wherein the
interfacial layer has a silicon atomic percent content of about 90%
or more; and growing an epitaxial source/drain region over the
interfacial layer by epitaxial growth.
10. (canceled)
11. The method of claim 9, wherein the interfacial layer is formed
by providing a silicon precursor.
12. The method of claim 11, wherein the silicon precursor comprises
silane.
13. The method of claim 11, wherein silane volatilizes impurities
from a surface of the fin.
14. The method of claim 9, wherein the interfacial layer provides a
surface roughness less than about 2 nm RMS for the growing of the
epitaxial source/drain region.
15. The method of claim 9, wherein the interfacial layer
encapsulates impurities on a surface of the fin.
16. A semiconductor structure comprising: a substrate; a fin on the
substrate, wherein the fin comprises silicon germanium; a first
interfacial layer over a first portion of the fin, wherein the
first interfacial layer comprises silicon germanium; a second
interfacial layer over a second portion of the fin, wherein the
second interfacial layer comprises silicon germanium, wherein the
first interfacial layer and the second interfacial layer have a
height variation within 5 nm; a first source/drain region on the
first interfacial layer, wherein the first source/drain region
comprises silicon germanium, the silicon germanium of the first
interfacial layer having a higher silicon atomic percent content
than the silicon germanium of the fin and the silicon germanium of
the first source/drain region; and a second source/drain region on
the second interfacial layer, wherein the second source/drain
region comprises silicon germanium, the silicon germanium of the
second interfacial layer having a higher silicon atomic percent
content than the silicon germanium of the fin and the silicon
germanium of the second source/drain region.
17. The semiconductor structure of claim 16, wherein the first
interfacial layer and the second interfacial layer each have a
thickness in a range from about 1 nm to about 4 nm.
18. The semiconductor structure of claim 16, wherein the first
interfacial layer and the second interfacial layer each have a
silicon atomic percent content in a range from about 90% to about
99.9%.
19. The semiconductor structure of claim 16, wherein the fin has a
germanium atomic percent content in a range from about 5% to about
40%.
20. The semiconductor structure of claim 16, wherein the first
source/drain region and the second source/drain region have a
height variation of less than about 10 nm.
21. The semiconductor structure of claim 1, wherein the interfacial
layer comprises silicon germanium, the interfacial layer having a
higher silicon atomic percent content than the source/drain region
and the fin.
22. The method of claim 9, wherein the interfacial layer comprises
silicon germanium, the interfacial layer having a higher silicon
atomic percent content than the epitaxial source/drain region and
the fin.
Description
BACKGROUND
[0001] As the semiconductor industry has progressed into nanometer
technology process nodes in pursuit of higher device density,
higher performance, and lower costs, challenges from both
fabrication and design issues have resulted in the development of
three-dimensional designs, such as a Fin Field Effect Transistor
(FinFET). FinFET devices typically include semiconductor fins with
high aspect ratios and in which channel and source/drain regions
are formed. A gate is formed over and along the sides of the fin
structure (e.g., wrapping) utilizing the advantage of the increased
surface area of the channel to produce faster, more reliable, and
better-controlled semiconductor transistor devices. However, with
the decreasing in scale, new challenges are presented.
BRIEF DESCRIPTION OF THE DRAWINGS
[0002] Aspects of the present disclosure are best understood from
the following detailed description when read with the accompanying
figures. It is noted that, in accordance with the standard practice
in the industry, various features are not drawn to scale. In fact,
the dimensions of the various features may be arbitrarily increased
or reduced for clarity of discussion.
[0003] FIG. 1 is a flow diagram illustrating a method of
manufacturing a semiconductor device, such as a FinFET structure,
in accordance with some embodiments.
[0004] FIGS. 2A-2C, 3A-3C, 4A-4B, 5A-5B, 6A-6B, 7A-7B, and 8A-8B
illustrate various views of respective intermediate structures of a
semiconductor device at intermediate stages of manufacturing the
semiconductor device, in accordance with some embodiments.
[0005] FIGS. 6C-6D are graphs of the atomic percent content of
germanium of a fin, an interfacial layer, and a source/drain
region, in accordance with some embodiments.
DETAILED DESCRIPTION
[0006] The following disclosure provides many different
embodiments, or examples, for implementing different features of
the provided subject matter. Specific examples of components and
arrangements are described below to simplify the present
disclosure. These are, of course, merely examples and are not
intended to be limiting. For example, the formation of a first
feature over or on a second feature in the description that follows
may include embodiments in which the first and second features are
formed in direct contact, and may also include embodiments in which
additional features may be formed between the first and second
features, such that the first and second features may not be in
direct contact. In addition, the present disclosure may repeat
reference numerals and/or letters in the various examples. This
repetition is for the purpose of simplicity and clarity and does
not in itself dictate a relationship between the various
embodiments and/or configurations discussed.
[0007] Further, spatially relative terms, such as "beneath,"
"below," "lower," "above," "upper" and the like, may be used herein
for ease of description to describe one element or feature's
relationship to another element(s) or feature(s) as illustrated in
the figures. 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 figures. The apparatus
may be otherwise oriented (rotated 90 degrees or at other
orientations) and the spatially relative descriptors used herein
may likewise be interpreted accordingly.
[0008] Embodiments disclosed herein relate generally to forming an
interfacial layer between an epitaxial source/drain region and a
fin of a FinFET device. For example, the fin may have a recess
formed therein, and the interfacial layer may be formed along
surfaces of the recess before the epitaxial source/drain region is
formed on the interfacial layer. In certain embodiments, the
interfacial layer may suppress the effects of surface impurities
formed during the manufacturing stages of a FinFET device. In
certain embodiments, the interfacial layer may enhance uniform
growth of the epitaxial source/drain region in the recess of a fin
of a FinFET device.
[0009] The fins may be patterned by any suitable method. For
example, the fins may be patterned using one or more
photolithography processes, including double-patterning or
multi-patterning processes. Generally, double-patterning or
multi-patterning processes combine photolithography and
self-aligned processes, allowing patterns to be created that have,
for example, pitches smaller than what is otherwise obtainable
using a single, direct photolithography process. For example, in
one embodiment, a sacrificial layer is formed over a substrate and
patterned using a photolithography process. Spacers are formed
alongside the patterned sacrificial layer using a self-aligned
process. The sacrificial layer is then removed, and the remaining
spacers may then be used to pattern the fins.
[0010] The foregoing broadly outlines some aspects of embodiments
described herein. Some embodiments described herein are described
in the context of Fin Field Effect Transistors (FinFETs). Some
embodiments are described herein in the context of a replacement
gate process. Implementations of some aspects may be used in other
processes and/or in other devices. For example, other example
processes can include a gate-first process, and other example
devices include Horizontal Gate All Around (HGAA) FETs, Vertical
Gate All Around (VGAA) FETs, nanowire channel FETs, and other
devices. Some variations of the example methods and structures are
described. A person having ordinary skill in the art will readily
understand other modifications that may be made that are
contemplated within the scope of other embodiments. Although method
embodiments may be described in a particular order, various other
method embodiments may be performed in any logical order and may
include fewer or more steps than what is described herein.
[0011] FIG. 1 is a flow diagram illustrating a method 10 of
manufacturing a semiconductor device, such as a FinFET structure,
in accordance with some embodiments. The method 10 is described in
reference to FIGS. 2A-B to FIGS. 8A-B. FIGS. 2A-B through 8A-B are
cross-sectional views and a perspective view of respective
intermediate semiconductor structures 30 at intermediate stages in
an example process of forming a semiconductor device in accordance
with some embodiments.
[0012] FIGS. 2A and 2B illustrate a semiconductor substrate 60, in
accordance with some embodiments. The semiconductor substrate 60
may be or include a bulk semiconductor substrate, a
semiconductor-on-insulator (SOI) substrate, or the like, which may
be doped (e.g., with a p-type or an n-type dopant) or undoped. In
some embodiments, the semiconductor material of the semiconductor
substrate 60 may include an elemental semiconductor including
silicon (Si) or germanium (Ge); a compound semiconductor; an alloy
semiconductor; or a combination thereof.
[0013] In the embodiments shown in FIGS. 2A and 2B, the
semiconductor substrate 60 may be a silicon wafer having an area
implanted or doped with an n-type dopant to form an n-well 62.
Other areas of the semiconductor substrate 60 may have other areas
implanted or doped with a p-type dopant to form a p-well (not
shown). In certain embodiments, a p-type FinFET device or a p-type
metal-oxide semiconductor device (PMOS) is formed over the n-well
62. A concentration of the n-type dopant in the n-well 62 can be in
a range from about 5.times.10.sup.16 cm.sup.-3 to about
1.times.10.sup.19 cm.sup.-3. In certain embodiments, an epitaxial
layer 64 may be deposited by epitaxial growth over the n-well 62.
In certain embodiments, the epitaxial layer 64 is a SiGe
(Si.sub.xGe.sub.1-x) layer having a germanium atomic percent
content in a range from about 5% to about 40%. In other
embodiments, the epitaxial layer 64 is a SiGe (Si.sub.xGe.sub.1-x)
layer having a germanium atomic percent content in a range from
about 40% to about 80%. The epitaxial layer 64 may also comprise a
gradient layer with a content of an element (e.g., germanium) that
varies along the depth of the epitaxial layer 64. Deposition
methods for depositing the epitaxial layer 64 include chemical
vapor deposition (CVD), low pressure CVD (LPCVD), atomic layer CVD
(ALCVD), ultrahigh vacuum CVD (UHVCVD), reduced pressure CVD
(RPCVD), vapor-phase epitaxy (VPE), molecular beam epitaxy (MBE),
any other suitable deposition processes, or any combination
thereof.
[0014] As shown in FIGS. 3A through 3C and at operation 12 of the
method 10, fins 74 are formed in the epitaxial layer 64 and the
semiconductor substrate 60, such as n-well 62. The fins 74 can be
formed by etching trenches through the epitaxial layer 64 into the
semiconductor substrate 60, such as into the n-well 62, using
appropriate photolithography and etching processes, for example.
Isolation regions 78 are formed, each in a corresponding trench.
The isolation regions 78 may include or be an insulating material
such as an oxide (such as silicon oxide), a nitride, the like, or a
combination thereof. The insulating material may be deposited by
any acceptable deposition process and recessed using an acceptable
etch process to form the isolation regions 78. The fins 74 protrude
from between neighboring isolation regions 78, which may, at least
in part, thereby delineate the fins 74 as active areas on the
semiconductor substrate 60.
[0015] In some embodiments, instead of forming the fins 74 from the
epitaxial layer 64, the fins 74 can be formed by etching the
trenches into the semiconductor substrate 60, similar to what was
described previously. Hence, the fins 74 can be the same material
as the semiconductor substrate. In certain embodiments, the
semiconductor substrate 60 is a silicon wafer, and the fins 74 are
also silicon. Fins 74 are generally depicted in some of the
subsequent figures, which can include or omit the epitaxial layer
64.
[0016] A person having ordinary skill in the art will readily
understand that the process described above is just an example of
how fins 74 may be formed. In other embodiments, a dielectric layer
can be formed over a top surface of the semiconductor substrate 60;
trenches can be etched through the dielectric layer; epitaxial
structures (e.g., homoepitaxial or heteroepitaxial structures) can
be epitaxially grown in the trenches; and the dielectric layer can
be recessed such that the epitaxial structures protrude from the
dielectric layer to form fins. Fins formed by these processes can
have a general structure similar to what is shown in the
figures.
[0017] As shown in FIGS. 3A through 3C and at operation 14 of the
method 10, dummy gate structures 85 are formed over the fins 74.
The dummy gate structures 85 are over and extend laterally
perpendicularly to the fins 74. Each dummy gate structure 85
comprises a dielectric layer 80, a dummy gate layer 82, and a mask
84. The dielectric layer 80, dummy gate layer 82, and mask 84 for
the dummy gate structures 85 may be formed by sequentially forming
respective layers, such as by appropriate deposition processes, and
then patterning those layers into the dummy gate structures 85,
such as by appropriate photolithography and etching processes. For
example, the dielectric layer 80 may include or be silicon oxide,
silicon nitride, the like, or multilayers thereof. The dummy gate
layer 82 may include or be silicon (e.g., polysilicon) or another
material. The mask 84 may include or be silicon nitride, silicon
oxynitride, silicon carbon nitride, the like, or a combination
thereof.
[0018] FIG. 3C illustrates the intermediate structure in a
three-dimensional view after the dummy gate structures 85 are
formed. Fins 74 are formed on the semiconductor substrate 60, and
the fins 74 each protrude above and from between neighboring
isolation regions 78. In each dummy gate structure 85, the
dielectric layer 80 is along sidewalls and over top surfaces of the
fins 74; the dummy gate layer 82 is over the dielectric layer 80;
and the mask 84 is over the dummy gate layer 82. Source/drain
regions 54a-f are disposed in respective regions of the fins 74 on
various opposing sides of a respective dummy gate structure 85.
[0019] FIG. 3C further illustrates reference cross-sections that
are used in figures. Cross-section A-A is in a plane along, e.g.,
channels in a fin 74 between opposing source/drain regions 54a-c.
Cross-section B-B is in a plane perpendicular to cross-section A-A
and is across source/drain region 54a and source/drain region 54d
in neighboring fins 74. Figures ending with an "A" designation
illustrate cross-sectional views at various instances of processing
corresponding to cross-section A-A, and figures ending with a "B"
designation illustrate cross-sectional views at various instances
of processing corresponding to cross-section B-B. In some figures,
some reference numbers of components or features illustrated
therein may be omitted to avoid obscuring other components or
features; this is for ease of depicting the figures.
[0020] In some embodiments, after forming the dummy gate structures
85, lightly doped drain (LDD) regions (not specifically
illustrated) may be formed in the fins 74. For example, dopants may
be implanted into the fins 74 using the dummy gate structures 85 as
masks. Example dopants for the LDD regions can include or be, for
example, boron for a p-type device and phosphorus or arsenic for an
n-type device, although other dopants may be used. The LDD regions
may have a dopant concentration in a range from about 10.sup.15
cm.sup.-3 to about 10.sup.17 cm.sup.-3.
[0021] As shown in FIGS. 4A and 4B, gate spacers 86 are formed
along sidewalls of the dummy gate structures 85 (e.g., sidewalls of
the dielectric layer 80, the dummy gate layer 82, and the mask 84)
and over the fins 74. The gate spacers 86 may be formed by
conformally depositing one or more layers for the gate spacers 86,
such as by an appropriate deposition process, and aniostropically
etching, such as by an appropriate etching process, the one or more
layers to form the gate spacers 86. The gate spacers 86 may include
or be silicon nitride, silicon oxynitride, silicon carbon nitride,
the like, multi-layers thereof, or a combination thereof.
[0022] As shown further in FIGS. 4A and 4B and at operation 16 of
the method 10, recesses 90 are formed in the fins 74. As
illustrated, the recesses 90 are formed in the fins 74 on opposing
sides of the dummy gate structures 85. The recesses 90 can be
formed by an etch process. The etch process can be isotropic or
anisotropic, or, further, may be selective with respect to one or
more crystalline planes of the semiconductor substrate 60 and/or
the epitaxial layer 64. Hence, the recesses 90 can have various
cross-sectional profiles based on the etch process implemented. The
etch process may be a dry etch, such as a plasma etch using a
processing gas, including but not limited to, tetrafluoromethane
(CF.sub.4), chlorine gas (Cl.sub.2), nitrogen trifluoride
(NF.sub.3), sulfur hexafluoride (SF.sub.6).
[0023] As shown in FIGS. 5A and 5B and at operation 18 of the
method 10, interfacial layers 92 are formed over surfaces of the
respective recesses 90 in the fins 74. The interfacial layer 92 may
include or be silicon germanium (Si.sub.xGe.sub.1-x where x can be
between approximately 0 and 1). In certain embodiments, interfacial
layer 92 comprises SiGe with a Si atomic percent content of about
90% or more (e.g., in a range from about 90% to about 99.9%) and a
Ge atomic percent content of about 10% or less (e.g., in a range
from about 0.1% to about 10%). In certain embodiments, the
interfacial layer 92 is deposited to a thickness 92T in a range
from about 1 nm to about 10 nm. In certain embodiment, the
interfacial layer 92 is deposited to a thickness 92T in a range
from about 1 nm to about 4 nm. In certain embodiments, a first
interfacial layer 92A is formed over a first portion (e.g., in a
first recess 90A) of the fin 74; and a second interfacial layer 92B
is formed over a second portion (e.g., in a second recess 90B) of
the fin 74. The first interfacial layer 92A and the second
interfacial layer 92B are formed to a height 92H. The term height
92H of the interfacial layer 92 is defined as the lowest point of
the top surface of the interfacial layer 92 in the recess 90 of the
fin 74. In certain embodiments, the variation of the height 92H of
the first interfacial layer 92A and the height 92H of the second
interfacial layer 92B is about 5 nm or less, such as in a range
from greater than 0 nm to about 5 nm.
[0024] The interfacial layer 92 may be formed in the recesses 90 by
epitaxially growing a material in the recesses 90, such as by
LPCVD, RPCVD, metal-organic CVD (MOCVD), MBE, liquid phase epitaxy
(LPE), VPE, selective epitaxial growth (SEG), the like, or a
combination thereof.
[0025] One example of a growth process for a SiGe interfacial layer
includes performing an epitaxial growth process at a temperature in
a range from about 500.degree. C. to about 800.degree. C. The
epitaxial growth process may be performed at a pressure in a range
from about 1 Torr to about 100 Torr. Processing gases may include
HCl, SiH.sub.4 (silane), SiH.sub.2Cl.sub.2 (dichlorosilane),
GeH.sub.4 (germane), H.sub.2, or N.sub.2, carrier gas, other
silicon precursors, other germanium precursors, other etching
gases, other carrier gases, and combinations thereof.
[0026] In certain embodiments, the interfacial layer 92 may help to
suppress the effects of surface impurities formed over or in the
fin 74 during various stages of manufacturing the semiconductor
structure 30. The interfacial layer 92 can help to cover impurities
and can help prevent impurities from entering underlying layers or
from diffusing out of underlying layers. For example, the
impurities may be chlorine, oxygen, carbon, fluorine, and/or
silicon species resulting and remaining from the etch process at
operation 16 in the formation of recesses 90 of the fins 74. For
example, the halogen impurities may come from the etching gases
used in a dry etch process, such as CF.sub.4, Cl.sub.2, NF.sub.3,
SF.sub.6 etching gas. The silicon impurities may come from the
silicon from the epitaxial layer 64 comprising SiGe or comprising
Si. The oxygen impurities may come from partial etching of the
isolation region 78 comprising silicon oxide. The carbon impurities
may come from carbon residual materials remaining from photoresist
or other layers of the semiconductor structure 30.
[0027] Not wishing to be bound by any theory unless specifically
set forth in the claims, the interfacial layer 92 comprising a high
amount of silicon, such as a Si atomic percent content of about 90%
or more (e.g., in a range from about 90% to about 99.9%), may help
to suppress the effects of surface impurities and reduce roughness.
In certain aspects, the high amount of a silicon precursor, such as
silane (SiH.sub.4), during the formation of the interfacial layer
92 may help to volatilize or to remove the impurities. In certain
aspects, the high amount of a silicon precursor, such as silane
(SiH.sub.4), during the formation of the interfacial layer 92 may
help cover or encapsulate the impurities within the interfacial
layer 92. The interfacial layer 92 may help to act as a getter so
that impurities reside in the interfacial layer 92 rather than in
the source/drain region. Impurities in the source/drain region may
disrupt the epitaxial growth and causes non-uniform growth of the
source/drain region. If the thickness of the interfacial layer 92
is less than 1 nm, surface impurities may still remain on the fin
74 or may not be fully covered by the interfacial layer 92. If the
thickness of the interfacial layer 92 is greater than 5 nm, the
growth of epitaxial layers thereover to form the source/drain
regions may lead to undesirable lattice dislocations in the
epitaxial source/drain regions formed thereover. Lattice
dislocations in the epitaxial source regions may result in an
undesirable lower strain transfer to the channel of strain channel
devices and may lower device performance.
[0028] In certain embodiments, the interfacial layer 92 may help to
lower the surface roughness of the recesses 90 of the fin 74. The
surface roughness of the recesses 90 of the fin 74 may be over
about 2.5 nm RMS. In certain embodiments, the interfacial layer 92
has a surface roughness of about 2 nm RMS or less, such as in a
range from about 0.1 nm RMS to about 2 nm RMS. In certain
embodiments, a smooth interfacial layer 92 may help to provide
uniform epitaxial growth of an epitaxial source/drain region
thereover. In certain embodiments, a smooth interfacial layer 92
may help to provide reduced crystal dislocations in an epitaxially
grown source/drain region resulting in increased conductivity of
the epitaxial source/drain region and/or increased adhesion of the
epitaxial source/drain region. In certain embodiments, a smooth
interfacial layer 92 may help to provide reduced crystal
dislocations in an epitaxial source/drain region resulting in
increased strain characteristics of the channel formed by the fin
74 below the dummy gate structures 85. For example, an epitaxial
source/drain region, such as a silicon germanium source/drain
region, may induce strain in the channel to increase the
semiconductor device performance. In certain embodiments, a smooth
interfacial layer 92 may help to provide uniform lateral and
uniform vertical growth of an epitaxial source/drain region so that
the shape of the epitaxial source/drain region may be controlled.
In certain embodiments, a smooth interfacial layer 92 may help to
provide uniform growth of an epitaxial source/drain region to a
uniform size and shape. A uniform size and shape of an epitaxial
source/drain region helps to provide consistent formation of many
contacts to the respective epitaxial source/drain regions.
[0029] As shown in FIGS. 6A and 6B and at operation 20 of the
method 10, an epitaxial source/drain region 94 is formed over the
interfacial layer 92. The epitaxial source/drain region 94 may
include or be silicon germanium (Si.sub.xGe.sub.1-x, where x can be
in a range from 0 to 1), silicon carbide, silicon phosphorus,
silicon carbon phosphorus, germanium, a III-V compound
semiconductor, a II-VI compound semiconductor, or the like.
[0030] In certain embodiments, the epitaxial source/drain region 94
comprise SiGe, the interfacial layer 92 comprises SiGe, and the fin
74 (e.g., epitaxial layer 64) comprises SiGe. In certain
embodiments, the epitaxial source/drain region 94 comprises SiGe
with an atomic percent content of germanium of about 25% or more
(e.g., in a range from about 25% to about 70%); the interfacial
layer 92 comprises SiGe with an atomic percent content of silicon
of about 90% or more (e.g., in a range from about 90% to about
99.9%); and the fin 74 (e.g., epitaxial layer 64) comprises SiGe
with an atomic percent content of germanium of about 5% or more
(e.g., in a range from about 5% to about 40%). In certain
embodiments, the SiGe source/drain 94 has a germanium atomic
percent content of about 20% or more greater than the germanium
atomic percent content of the SiGe fin 74.
[0031] In some examples, the epitaxial source/drain regions 94 may
also be doped, such as by in situ doping during epitaxial growth
and/or by implanting dopants into the epitaxial source/drain region
94 after epitaxial growth. Example dopants for the epitaxial
source/drain region 94 can include or be, for example, boron for a
p-type device and phosphorus or arsenic for an n-type device,
although other dopants may be used. The epitaxial source/drain
region 94 (or other source/drain region) may have a dopant
concentration in a range from about 10.sup.19 cm.sup.-3 to about
10.sup.21 cm.sup.-3. A source/drain region may be delineated by
doping (e.g., by implantation and/or in situ during epitaxial
growth, if appropriate) and/or by epitaxial growth, if appropriate,
which may further delineate the active area in which the
source/drain region is delineated.
[0032] In certain embodiments, the epitaxial source/drain region 94
may comprise multiple layers. In certain examples, the epitaxial
source/drain region 94 comprises a first layer (L1), a second layer
(L2), and a third layer (L3). In certain embodiments, the epitaxial
source/drain region comprises a first layer of SiGe, a second layer
of SiGe, and a third layer of SiGe, in which each of the layers
have a different germanium atomic percent content and/or a
different dopant concentration. In certain embodiments, the
epitaxial source/drain region 94 comprises a first layer of SiGe, a
second layer of SiGe, and a third layer of a capping material. The
capping material may be or comprise Si or other suitable materials.
In certain embodiments, the capping material can help protect the
underlying SiGe from environmental effects, such as oxidation and
humidity. The capping layer may also be used to form better ohmic
contact with a metal used to make electrical contact with the
epitaxial source/drain region 94. In certain embodiments, the
capping material can help to protect the underlying SiGe from
outgassing germanium.
[0033] Although the epitaxial source/drain region 94 is illustrated
as three layers, the epitaxial source/drain region 94 is not
limited to such layers. In other embodiments, the epitaxial
source/drain region 94 may comprise one layer, two layers, or more
layers. In other embodiments, the epitaxial source/drain region 94
may comprise additional layers (e.g., additional intermediate
layer(s), additional outer layer(s)).
[0034] As shown in FIG. 6B, two epitaxial source/drain regions 94
are formed as a merged source/drain region. In other embodiments,
the epitaxial source/drain region 94 may be formed as an unmerged
doped source/drain region. The growth of the epitaxial source/drain
region 94 may be other shapes depending on the bottom surface of
the recess 90 and/or depending on a lateral and a vertical growth
of the epitaxial growth of the epitaxial source/drain region 94
over the interfacial layer 92.
[0035] The epitaxial source/drain region 94 may be formed over the
interfacial layer 92 by epitaxially growing a material in the
recesses 90, such as by LPCVD, RPCVD, MOCVD, MBE, LPE, VPE, SEG,
the like, or a combination thereof. As illustrated in FIGS. 6A and
6B, due to blocking by the isolation regions 78, the epitaxial
source/drain region 94 is first grown vertically in the recess 90,
during which time the epitaxial source/drain region 94 may not grow
horizontally. After the recess 90 is fully filled, the epitaxial
source/drain region 94 may grow both vertically and horizontally to
form facets, which may correspond to crystalline planes of the
semiconductor substrate 60. In some examples, different materials
are used for epitaxial source/drain regions for p-type devices and
n-type devices. Appropriate masking during the recessing or
epitaxial growth may permit different materials to be used in
different devices.
[0036] In certain embodiments, the interfacial layers 92A and 92B
may be formed to a height 92H with a variation of about 5 nm or
less. The height 92H with a variation of about 5 nm or less helps
epitaxially growth of the source/drain regions 94A and 94B over the
interfacial layer 92 to a height 94H having a variation in a range
from about 0 nm to about 10 nm. For example, the height 94H of a
first source/drain region 94A formed over the first interfacial
layer 92A and the height 94H of a second source/drain region 94B
formed over the second interfacial layer 92B are substantially
uniform. The term height 94H of the source/drain region 94 is
defined as the highest point of the top surface of the source/drain
94.
[0037] FIG. 6C is a graph 200 of the atomic percent content of
germanium across the fin 74, the interfacial layer 92, the
source/drain region 94, and back through the interfacial layer 92,
and the fin 74 in a direction 98 (as shown in FIG. 6A), in
accordance with some embodiments. The germanium atomic percent
content of the interfacial layer 92 is lower than the germanium
atomic percent content of the fin 74 and the source/drain region 94
adjacent to the interfacial layer 92. The germanium atomic percent
content of the source/drain region 94 is higher than the fin 74
adjoined by the interfacial layer 92.
[0038] FIG. 6D is a graph 300 of the atomic percent content of
germanium through the third layer L3, the second layer L2, and the
first layer L1 of the source/drain region 94, through the
interfacial layer 92, and into fin 74 in a direction 99 (as shown
in FIG. 6A), in accordance to some embodiments. The germanium
atomic percent content of the interfacial layer 92 is lower than
the germanium atomic percent content of the first layer L1 of the
source/drain region 94 and the fin 74 adjacent to the interfacial
layer 92. The germanium atomic percent content of the first layer
L1 of the source/drain region 94 is higher than the fin 74 adjoined
by the interfacial layer 92. The germanium atomic percent content
of the third layer L3 of the source/drain region 94 is lower than
the second layer L2 of the source/drain region 94 but higher than
the first layer L1 of the source/drain region 94.
[0039] FIGS. 7A and 7B illustrate the formation of a contact etch
stop layer (CESL) 96 and a first interlayer dielectric (ILD) 100
over the CESL 96. Generally, an etch stop layer can provide a
mechanism to stop an etch process when forming, e.g., contacts or
vias. An etch stop layer may be formed of a dielectric material
having a different etch selectivity from adjacent layers or
components. The CESL 96 is deposited, such as by an appropriate
deposition process, on surfaces of the epitaxial source/drain
regions 94, sidewalls and top surfaces of the gate spacers 86, top
surfaces of the mask 84, and top surfaces of the isolation regions
78. The CESL 96 may comprise or be silicon nitride, silicon carbon
nitride, silicon carbon oxide, carbon nitride, the like, or a
combination thereof. The first ILD 100 may comprise or be silicon
dioxide, a low-k dielectric material (e.g., a material having a
dielectric constant lower than silicon dioxide), silicon
oxynitride, phosphosilicate glass (PSG), borosilicate glass (BSG),
borophosphosilicate glass (BPSG), undoped silicate glass (USG),
fluorinated silicate glass (FSG), organosilicate glasses (OS G),
SiO.sub.xC.sub.y, Spin-On-Glass, Spin-On-Polymers, silicon carbon
material, a compound thereof, a composite thereof, the like, or a
combination thereof. The first ILD 100 may be planarized after
being deposited, such as by a CMP, which may remove the masks 84
from the dummy gate structures 85 and expose the dummy gate layers
82.
[0040] FIGS. 8A and 8B illustrate an intermediate structure after
replacing the dummy gate structures 85 with respective replacement
gate structures, forming a second ILD 130, and forming contacts
146A, 146B, 146C. The dummy gate structures 85 are removed, such as
by an appropriate etching process, to form trenches. The trenches
are filled with respective replacement gate structures. The
replacement gate structures each include a conformal gate
dielectric layer 112, an optional metal liner layer 114, and a
conductive gate fill 116. The conformal gate dielectric layer 112,
optional metal liner layer 114, and conductive gate fill 116 can be
deposited by appropriate deposition techniques.
[0041] The gate dielectric layer 112 is formed conformally in the
trench, such as along sidewall and top surfaces of the fin 74 and
along sidewalls of the gate spacers 86. The gate dielectric layer
112 may be a silicon oxide, silicon nitride, a high-k dielectric
material, or multilayers thereof. A high-k dielectric material,
such as a dielectric having a k value greater than about 7.0, may
include or be a metal oxide or a silicate of Hf, Al, Zr, La, Mg,
Ti, Y, Sc, Lu, Gd, Sr, Dy, Ca, Sm, or a combination thereof.
[0042] One or a plurality of metal liner layers 114 can be formed
conformally over the gate dielectric layer 112. The metal liner
layers 114 can include a capping layer, a barrier layer, and/or a
work function tuning layer. A capping layer and a barrier layer can
be used to prevent impurities from diffusing into or away from
underlying layers. The capping layer and/or barrier layer may
include tantalum nitride, titanium nitride, the like, or
combinations thereof. A work function tuning layer can be chosen to
tune the work function value so that a desired threshold voltage Vt
is achieved in the transistor that is formed. Examples of a work
function tuning layer include TaAl, TaN, TaAlC, TaC, TaCN, TaSiN,
Ti, TiN, TiAlN, Ag, Mn, Zr, Ru, Mo, Al, WN, ZrSi.sub.2, MoSi.sub.2,
TaSi.sub.2, NiSi.sub.2, other suitable work function materials, or
a combination thereof.
[0043] A conductive gate fill 116 is formed over the optional metal
liner layer 114 (if implemented) and/or the gate dielectric layer
112 and fills the trench. The conductive gate fill 116 may comprise
a metal-containing material such as tungsten (W), cobalt (Co),
ruthenium (Ru), aluminum (Al), titanium nitride (TiN), tantalum
nitride (TaN), tantalum carbon (TaC), titanium aluminum nitride
(AlTiN), titanium aluminum carbon (AlTiC), titanium aluminum oxide
(AlTiO), a combination thereof, multi-layers thereof, and other
suitable conductive materials.
[0044] Portions of the layers for the conductive gate fill 116, the
optional metal liner layer 114, and the gate dielectric layer 112
above the top surfaces of the first ILD 100, the CESL 96, and the
gate spacers 86 are removed, such as by a planarization process,
like a CMP process.
[0045] The second ILD 130 is formed over the first ILD 100, the
replacement gate structures, the gate spacers 86, and the CESL 96.
Although not illustrated, in some examples, an etch stop layer may
be deposited over the first ILD 100, etc., and the second ILD 130
may be deposited over the ESL. The second ILD 130 may comprise or
be silicon dioxide, a low-k dielectric material, silicon
oxynitride, PSG, BSG, BPSG, USG, FSG, OSG, SiO.sub.xC.sub.y,
Spin-On-Glass, Spin-On-Polymers, silicon carbon material, a
compound thereof, a composite thereof, the like, or a combination
thereof. The second ILD 130 may be deposited by any acceptable
deposition technique.
[0046] Openings through the second ILD 130, the first ILD 100, and
the CESL 96 to the epitaxial source/drain regions 94 are formed to
expose at least portions of the epitaxial source/drain regions 94,
such as by using appropriate photolithography and one or more etch
processes. Contacts 146 are formed in the openings to the epitaxial
source/drain regions 94. The contacts 146 may include a fill metal,
such as tungsten, aluminum, cobalt, ruthenium, copper, or other
suitable metals. The contacts 146 may further include silicide on
the respective epitaxial source/drain regions 94 and a barrier
and/or adhesion layer between the fill metal and sidewalls of the
openings.
[0047] It is understood that the semiconductor devices and methods
of manufacture may also include additional layers, such as
photoresist layers, mask layers, diffusion barrier layers, capping
layers, silicide areas, etch stop layers, dielectric layers,
adhesion layers, and the other suitable layers. It is understood
that the substrate may include a plurality of features (doped
regions or wells, fins, source/drain regions, isolation regions,
shallow trench isolation (STI) feature, gate structures,
interconnect lines, vias, and other suitable features) formed in,
on, and/or over the substrate. The plurality of layers and/or
features is used in the fabrication of semiconductor devices and
integrated circuits. The substrate may also include additional
materials formed in, on, and/or over the substrate in the
operations of the methods and in the figures as described herein.
The semiconductor devices and methods may also include additional
manufacturing processes including photoresist coating (e.g.,
spin-on coating), soft baking, mask aligning, exposure,
post-exposure baking, developing the photoresist, rinsing, drying,
hard baking, inspection, etching, planarization, chemical
mechanical polishing (CMP), wet clean, ashing, and/or other
applicable processes. While the source/drain regions discussed
herein are fabricated using recessed fins, source/drain regions may
be fabricated by forming source/drain regions over non-recessed
fins.
[0048] In certain embodiments, a p-type FinFET in a FinFET device
is formed over an n-well and/or with p-type/p-doped epitaxial
source/drain regions. It is understood that the p-type FinFET
devices may also be integrated with the formation of n-type FinFET
devices.
[0049] Embodiments disclosed herein relate generally to forming an
interfacial layer, such as an interfacial layer comprising SiGe
along surfaces of a recess in a fin between an epitaxial
source/drain region and the fin of a FinFET device. In certain
embodiments, the interfacial layer may suppress the effects of
surface impurities formed during the manufacturing stages of a
FinFET device. In certain embodiments, the interfacial layer may
enhance uniform growth of the epitaxial source/drain region in the
respective recesses of a fin of a FinFET device. In certain
embodiments, the epitaxial source/drain region comprises p-doped
SiGe to induce strain in a channel defined by a gate structure over
the fin.
[0050] An embodiment is a semiconductor structure. The
semiconductor structure includes a substrate. A fin is on the
substrate. The fin includes silicon germanium. An interfacial layer
is over the fin. The interfacial layer has a thickness in a range
from about 1 nm to about 4 nm. A source/drain region is over the
interfacial layer. The source/drain region includes silicon
germanium.
[0051] An embodiment is a method of manufacturing a semiconductor
device. The method includes forming a fin on a substrate. A gate
structure is formed over the fin. A recess is formed in the fin
proximate the gate structure. An interfacial layer is formed in the
recess. The interfacial layer includes silicon germanium. A
source/drain region is formed over the interfacial layer by
epitaxial growth.
[0052] An embodiment is another semiconductor structure. The
semiconductor structure includes a substrate. A fin is on the
substrate. A first interfacial layer is over a first portion of the
fin. A second interfacial layer is over a second portion of the
fin. The first interfacial layer and the second interfacial layer
have a height variation within 5 nm. A first source/drain region is
on the first interfacial layer. A second source/drain region is on
the second interfacial layer.
[0053] The foregoing outlines features of several embodiments so
that those skilled in the art may better understand the aspects of
the present disclosure. Those skilled in the art should appreciate
that they may readily use the present disclosure as a basis for
designing or modifying other processes and structures for carrying
out the same purposes and/or achieving the same advantages of the
embodiments introduced herein. Those skilled in the art should also
realize that such equivalent constructions do not depart from the
spirit and scope of the present disclosure, and that they may make
various changes, substitutions, and alterations herein without
departing from the spirit and scope of the present disclosure.
* * * * *