U.S. patent application number 13/905534 was filed with the patent office on 2014-12-04 for methods for making a semiconductor device with shaped source and drain recesses and related devices.
The applicant listed for this patent is International Business Machines Corporation, STMicroelectronics, Inc.. Invention is credited to Douglas LaTulipe, Nicolas Loubet, Alexander Reznicek.
Application Number | 20140353714 13/905534 |
Document ID | / |
Family ID | 51948320 |
Filed Date | 2014-12-04 |
United States Patent
Application |
20140353714 |
Kind Code |
A1 |
Loubet; Nicolas ; et
al. |
December 4, 2014 |
METHODS FOR MAKING A SEMICONDUCTOR DEVICE WITH SHAPED SOURCE AND
DRAIN RECESSES AND RELATED DEVICES
Abstract
A method for making a semiconductor device includes forming at
least one gate stack on a layer comprising a first semiconductor
material and etching source and drain recesses adjacent the at
least one gate stack. The method further includes shaping the
source and drain recesses to have a vertical side extending
upwardly from a bottom to an inclined extension adjacent the at
least one gate stack.
Inventors: |
Loubet; Nicolas;
(Guilderland, NY) ; LaTulipe; Douglas;
(Guilderland, NY) ; Reznicek; Alexander; (Troy,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
International Business Machines Corporation
STMicroelectronics, Inc. |
Armonk
Coppell |
NY
TX |
US
US |
|
|
Family ID: |
51948320 |
Appl. No.: |
13/905534 |
Filed: |
May 30, 2013 |
Current U.S.
Class: |
257/190 ;
438/300 |
Current CPC
Class: |
H01L 29/0847 20130101;
H01L 21/823425 20130101; H01L 29/7848 20130101; H01L 29/4958
20130101; H01L 29/41783 20130101; H01L 29/66628 20130101; H01L
27/092 20130101; H01L 29/66636 20130101; H01L 29/165 20130101 |
Class at
Publication: |
257/190 ;
438/300 |
International
Class: |
H01L 29/78 20060101
H01L029/78; H01L 29/66 20060101 H01L029/66 |
Claims
1. A method for making a semiconductor device comprising: forming
at least one gate stack on a layer comprising a first semiconductor
material; etching source and drain recesses adjacent the at least
one gate stack; and shaping the source and drain recesses to have a
vertical side extending upwardly from a bottom to an inclined
extension adjacent the at least one gate stack and forming lined
source and drain recesses by depositing and etching a second
semiconductor material.
2. The method according to claim 1 wherein the shaping comprises
cyclically depositing and etching the second semiconductor material
to form the lined source and drain recesses.
3. The method according to claim 2 further comprising filling the
lined source and drain recesses with the second semiconductor
material to define raised source and drain regions.
4. The method according to claim 3 wherein the cyclically
depositing and etching, and filling are performed in a same
processing chamber.
5. The method according to claim 3 wherein the first and second
semiconductor materials are different semiconductor materials so
that stress is imparted to a channel region under the at least one
gate stack.
6. The method according to claim 3 wherein the first semiconductor
material comprises silicon; and the second semiconductor material
comprises silicon and germanium.
7. The method according to claim 1 wherein the inclined extension
has a vertical dimension less than a vertical dimension of the
vertical side.
8. The method according to claim 1 wherein the inclined extension
has a vertical dimension less than half a vertical dimension of the
vertical side.
9. The method according to claim 1 wherein the bottom has a tapered
shape.
10. A method for making a semiconductor device comprising: forming
at least one gate stack on a layer comprising a first semiconductor
material; etching source and drain recesses adjacent the at least
one gate stack; and shaping the source and drain recesses to have a
vertical side extending upwardly from a bottom to an inclined
extension adjacent the at least one gate stack so that the inclined
extension has a vertical dimension less than a vertical dimension
of the vertical side, the shaping comprising cyclically depositing
and etching a second semiconductor material to form lined source
and drain recesses.
11. The method according to claim 10 further comprising filling the
lined source and drain recesses with the second semiconductor
material to define raised source and drain regions.
12. The method according to claim 11 wherein the cyclically
depositing and etching, and filling are performed in a same
processing chamber.
13. The method according to claim 11 wherein the first and second
semiconductor materials are different semiconductor materials so
that stress is imparted to a channel region under the at least one
gate stack.
14. The method according to claim 11 wherein the first
semiconductor material comprises silicon; and the second
semiconductor material comprises silicon and germanium.
15. The method according to claim 10 wherein the inclined extension
has a vertical dimension less than half a vertical dimension of the
vertical side.
16. The method according to claim 10 wherein the bottom has a
tapered shaped.
17-23. (canceled)
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the field of electronic
devices, and more particularly, to semiconductor devices and
related methods.
BACKGROUND OF THE INVENTION
[0002] Semiconductor devices, such as semiconductor integrated
circuit (IC's), include numerous semiconductor device structures.
Examples are insulated-gate transistors, such as Complementary
Metal Oxide Semiconductor (CMOS) transistors, which include both
P-channel and N-channel MOS transistors. MOS-type transistors may
be formed by gate stack deposition and patterning followed by
spacer deposition and etching to form a transistor circuit having a
raised source/drain structure. Active source and drain recesses are
formed that may be "sigma" shaped recesses because of their
similarity to the Greek letter "sigma" (.SIGMA.). This
configuration may impart maximum compressive stress. Other recess
configurations are "box" shaped with straight walls for lower
off-state leakage. There are a number of recognized fabrication
processes for building these transistors and they share a common
fabrication step of selectively depositing semiconductor material
above the source and drain regions to form raised source and drain
structures using selective epitaxial deposition.
[0003] Epitaxial deposition is often used to control the electrical
properties of the source and drain regions of insulated-gate
transistors. It is possible to control the dopant levels present
within single crystal regions by introducing dopants into the
epitaxial silicon layers. For example, it is possible to introduce
germanium (Ge) or carbon (C) atoms in order to introduce mechanical
stress into the epitaxial layers and increase the mobility of
charge carriers in the source and drain regions.
[0004] The epitaxial layer may be formed as a silicon germanium
(SiGe) layer in proximity to the gate channel. The active source
and drain shapes are often formed to impart greater compressive
stress due to the epitaxial SiGe proximity, but as a result, there
may be greater off-state leakage, which is detrimental to
transistor function. It is desirable if the source and drain
regions may be formed for greater stress while maintaining a lower
off-state leakage.
SUMMARY OF THE INVENTION
[0005] A method of making a semiconductor device may include
forming at least one gate stack on a layer comprising a first
semiconductor material and etching source and drain recesses
adjacent the at least one gate stack. The method may further
include shaping the source and drain recesses to have a vertical
side extending upwardly from a bottom to an inclined extension
adjacent the at least one gate stack. The shaping may further
include cyclically depositing and etching a second semiconductor
material to form lined source and drain recesses. The method may
further include filling the lined source and drain recesses with a
second semiconductor material to define raised source and drain
regions.
[0006] The cyclically depositing and etching and filling may be
performed in the same processing chamber. The first and second
semiconductor materials may be different semiconductor materials so
that a stress is imparted to a channel region under the at least
one gate stack. The first semiconductor material may comprise
silicon, and the second semiconductor material may comprise silicon
and germanium. The inclined extension may have a vertical dimension
less than a vertical dimension of the vertical side. The inclined
extension may have a vertical dimension less than a half vertical
dimension of the vertical side. The bottom may be tapered.
[0007] A semiconductor device comprising a layer of first
semiconductor material and at least one gate stack on the layer of
the first semiconductor material. Source and drain regions of a
second semiconductor material are adjacent the at least one gate
stack. Each source and drain region has a bottom, a vertical side
extending upwardly from the bottom, and an inclined extension
extending from the vertical side adjacent the at least one gate
stack.
[0008] The source and drain regions may comprise raised source and
drain regions. The first semiconductor material layer may comprise
a channel region under the at least one gate stack. The first and
second semiconductor materials may be different semiconductor
materials so that stress is imparted to the channel region. The
first semiconductor material may comprise silicon, and the second
semiconductor material may comprise silicon and germanium. The
inclined extension may have a vertical dimension less than a
vertical dimension of the vertical side. In another example, the
inclined extension may have a vertical dimension less than half a
vertical dimension of the vertical side. The bottom wall may have a
tapered shape in another example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Other features and advantages of the present invention will
become apparent from the detailed description of the invention
which follows, when considered in light of the accompanying
drawings in which:
[0010] FIG. 1 is an image of a cross-sectional view of a prior art
semiconductor device showing source and drain "sigma" shaped
regions and a silicon germanium (Site) epitaxial layer adjacent the
source and drain regions.
[0011] FIG. 2 is a cross-sectional view of the semiconductor device
in accordance with a non-limiting example of the present invention
and showing a first processing step of shallow trench isolation
(STI) in a layer of first semiconductor material such as a silicon
substrate to define a transistor active region.
[0012] FIG. 3 is a cross-sectional view showing a second processing
step of forming at least one gate stack on the layer of first
semiconductor material.
[0013] FIG. 4 is a cross-sectional view showing a third processing
step of silicon nitride (SiN) deposition and reactive ion etching
(RIE).
[0014] FIG. 5 is a cross-sectional view showing a fourth processing
step of etching source and drain recesses adjacent the at least one
gate stack.
[0015] FIG. 6 is a cross-sectional view showing a fifth processing
step of shaping source and drain recesses and filling with a second
semiconductor material to form the semiconductor device in
accordance with a non-limiting example of the present
invention.
[0016] FIG. 7 is an image of a cross-sectional view of the
semiconductor device shown in FIG. 6 in accordance with a
non-limiting example of the present invention.
[0017] FIG. 8 is an enlarged image of a cross-sectional view of the
semiconductor device shown in FIG. 7 in accordance with a
non-limiting example of the present invention.
[0018] FIG. 9 is a flowchart illustrating a method for making the
semiconductor device in accordance with a non-limiting example.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0019] Different embodiments will now be described more fully
hereinafter with reference to the accompanying drawings, in which
preferred embodiments are shown. Many different forms can be set
forth and described embodiments should not be construed as limited
to the embodiments set forth herein. Rather, these embodiments are
provided so that this disclosure will be thorough and complete, and
will fully convey the scope to those skilled in the art.
[0020] FIG. 1 is an image of a cross-sectional view of a prior art
semiconductor device illustrated generally at 10 having a gate
stack 12 and showing "sigma" shaped source and drain regions in
recesses 14. The silicon germanium (SiGe) epitaxial layer 16 is
adjacent the source and drain recesses 14. The "sigma" shaped term
is defined by those skilled in the art to refer to the "sigma"
shape of the Greek letter sigma (.SIGMA.) defined on the side of
the source and drain recesses 14. This configuration imparts
greater stress into the channel 20 due to the epitaxial SiGe
proximity to the gate channel. The sigma shape of the source and
drain recesses 14 imparts greater stress as compared to a straight
or "box" shape of other prior art devices. A drawback of the sigma
configuration, however, is its greater off-state leakage.
[0021] Conventional semiconductor processing techniques are used to
form this prior art semiconductor device 10 illustrated in FIG. 1,
including initial shallow trench isolation to define an active
transistor device region within the silicon substrate. The gate
stack 12 is deposited and patterned such as using a nitride spacer
followed by spacer deposition and etching using semiconductor
processing techniques known to those skilled in the art. The active
source and drain recesses 14 are etched to form the "sigma" shape
source and drain recess shapes, followed by cleaning, prebaking and
depositing a silicon germanium (SiGe) or epitaxial silicon carbon
(SiC) epitaxial layer. Final spacer and silicide formation is
accomplished followed by back-end processing as known to those
skilled in the art.
[0022] As noted before, the "sigma" shaped source and drain
recesses 14 impart greater stress compared to a "box" shaped source
and drain recesses because of the SiGe epitaxial proximity to the
channel 20 and greater off-state leakage. In prior art processing
techniques, the source and drain recesses 14 could be formed
ex-situ by wet processing, and there was typically a requirement
for a dedicated preclean and high temperature prebake before any
SiGe epitaxial deposition. There was also an enhanced risk of
silicon migration during the prebake and shape modification.
[0023] These disadvantages are overcome by the semiconductor device
and methods in accordance with a non-limiting example as explained
below with reference to FIGS. 2-9.
[0024] FIGS. 2-6 are cross-sectional views showing different stages
in the formation of this semiconductor device as shown generally at
30 in FIG. 6 and as shown in the images as cross-sectional views in
FIGS. 7 and 8. The semiconductor device 30 includes source and
drain recess shapes that enhances stress boosting. This recess
shape is a mix between the "sigma" shape as shown in FIG. 1 for
maximum stress, and a "box" or straight shape for lower off-state
leakage. Source and drain recess etching and SiGe epitaxial
deposition may be performed in a same processing chamber, for
example, an epitaxial reactor, as the same process step. There is
thus no requirement for an in-situ high temperature prebake for the
epitaxial deposition. Extension regions at the source and drain
recesses may be engineered by the epitaxial deposition for
optimized short channel effects and low device leakage. An example
final product that can be formed by this process is a 20 nanometer
(nm) CMOS semiconductor device. The SiGe epitaxial deposition may
use an in-situ boron doped (ISBD) SiGe process with the Ge
composition ranging from about 35% to about 60% in one non-limiting
example.
[0025] The process steps shown in FIGS. 5-6 may be performed in a
single chamber, such as an epitaxy reactor for clean surface
processing while shaping the epitaxial layer. FIG. 2 illustrates a
substrate 32 formed from a first semiconductor material, such as
silicon, and the shallow trench isolation 34 to define an active
transistor region 36. The shallow trench isolation (STI) 34 is also
referred to as box isolation for integrated circuits and reduces
electrical leakage and is used for CMOS manufacturing.
[0026] FIG. 3 illustrates the gate stack deposition and patterning
in which at least one gate stack 40 is formed on the layer of first
semiconductor material 32 and defines a gate channel region 41. In
this example of FIG. 3, two gate stacks 40 are illustrated, but it
should be understood that an "n" number of gate stacks may be
formed. Each gate stack 40 includes an upper silicon nitride (SiN)
layer 42 applied over a polysilicon layer 44, which had been
applied over a metallic layer 46 having a desired metallic work
function and over an oxide layer 48 that is formed on the silicon
substrate 32 as the first semiconductor material.
[0027] FIG. 4 illustrates further silicon nitride (SiN) deposition
and reactive ion etching (RIE). A layer of SiN material 50 is
applied at the sides of each gate stack 40 to protect the gate
stack during subsequent etching and shaping of source and drain
recesses as explained below.
[0028] Wafer processing for shape creation may occur in the same
processing chamber as the epitaxial reactor. The wafer is loaded
and the epitaxial reactor is set for depth and an etch temperature
processing between 650.degree. to 800.degree. C., in one
non-limiting example, and at a pressure from 5 TORR to about 500
TORR. Deposition occurs with Si, SiGe, SiC and other precursors:
Silicon Dichlorosilane SiH2Cl2 (as the Silicon precursor), Germane
(GeH4), and Carbon Methylsilane (CH3--SiH3). Doping may occur with
Boron Diborane (B2H6), Phosphorous Phosphine (PH3), and Arsenic
Arsine (ASH3).
[0029] FIG. 5 shows anisotropic source and drain recess formation
by etching source and drain recesses 52 adjacent the gate stacks
40. Etching may occur with Reactive Ion Beam (RIE).
[0030] To shape the source and drain recesses 52 to have a vertical
side 54 extending upwardly from a bottom 56 to an inclined
extension 58 adjacent the gate stack 40 such as shown in the
semiconductor device and final processing in FIG. 6., a second
semiconductor material is cyclically deposited and etched as an
epitaxial silicon germanium material and preferably a silicon
germanium boron Si(Ge)B material 60 in one example to form lined
source and drain recesses 52. The process for source and drain
recess shaping using cyclical deposition/etch is as follows: (1)
wafer loading; (2) set wafer at dep/etch temperature:
650<T<800, pressure 5 Torr-500 Torr deposition with Si, SiGe,
SiC, and precursors: Silicon dichlorosilane SiH2Cl2 (silicon
precursor), germanium germane (GeH4), carbon methylsilane
(CH3--SiH3) and Doping: Boron diborane (B2H6), Phosphorus Phosphine
(PH3), Arsenic arsine (AsH3); and (3) followed by etching with HCl
at a typical flow of 100 sccm to 20 slm. Steps (2) and (3) are
repeated "n" times until the final shape is created.
[0031] These source and drain recesses 52 that are lined with the
Si(Ge)B material 60 are filled with a second semiconductor material
as an epitaxial layer SiGe fill 62 and define raised source and
drain regions 64 as best illustrated in FIGS. 7 and 8.
[0032] As noted before, the cyclical depositing, etching and
filling are advantageously performed in a same processing chamber,
such as an epitaxy reactor. The first and second semiconductor
materials may be different semiconductor materials so that stress
is imparted to the channel region 41 under the gate stacks 40. The
first semiconductor material as noted before is formed as silicon,
and the second semiconductor material as noted before is formed as
silicon and germanium (SiGe) with Si(Ge)B being used for the
material 60 lining the source and drain recesses 52. As best shown
in FIG. 6, the inclined extension 58 in an example has a vertical
dimension less than a vertical dimension of the vertical side 54,
and in another example, the inclined extension has a vertical
dimension less than a half a vertical dimension of the vertical
side. The bottom 56 has a tapered shape as best shown in the
cross-sectional image of FIG. 7.
[0033] The epitaxially deposited layer is typically silicon
germanium with the germanium content ranging from about 25% to
about 60% to impart compressive stress. The same range of pressures
may be applied in the same processing chamber as an epitaxy reactor
with the pressures ranging from about 5 TORR to about 500 TORR and
the temperature ranging from about 500.degree. C. to about
800.degree. C. Deposition may occur with Si, SiGe precursors as
noted before and doping may occur with the same dopants as noted
before.
[0034] FIG. 7 is a sectional view of an image of the semiconductor
device 30 of FIG. 6.
[0035] FIG. 8 is an enlarged sectional view showing an image of a
portion of the semiconductor device shown in FIG. 7 and showing
greater details of a 2.5 nm intrinsic silicon liner for the source
and drain recesses 52. In this example, the Germanium content is
about 35% for the in-situ boron doped (ISBD) process.
[0036] FIG. 9 is a high level flowchart illustrating a method for
making the semiconductor device as shown in FIGS. 6-8 in accordance
with a non-limiting example. The process starts at block 100 and
the gate stacks are formed on the silicon semiconductor material
(block 102). The source and drain recesses are etched adjacent the
at least one gate stack (block 104). Lined source and drain regions
are formed by cyclically depositing and etching "n" times a second
semiconductor material as silicon and germanium (block 106). The
lined source and drain recesses are filled to define raised source
and drain regions (block 108). The process ends (block 110).
[0037] Many modifications and other embodiments of the invention
will come to the mind of one skilled in the art having the benefit
of the teachings presented in the foregoing descriptions and the
associated drawings. Therefore, it is understood that the invention
is not to be limited to the specific embodiments disclosed, and
that modifications and embodiments are intended to be included
within the scope of the appended claims.
* * * * *