U.S. patent application number 11/309204 was filed with the patent office on 2007-05-17 for cmos and mos device.
Invention is credited to Pei-Yu Chou, Wen-Han Hung, Min-Chieh Yang.
Application Number | 20070111420 11/309204 |
Document ID | / |
Family ID | 38041439 |
Filed Date | 2007-05-17 |
United States Patent
Application |
20070111420 |
Kind Code |
A1 |
Chou; Pei-Yu ; et
al. |
May 17, 2007 |
CMOS AND MOS DEVICE
Abstract
A complementary metal-oxide-semiconductor (CMOS) device
comprising a substrate, a first type of metal-oxide-semiconductor
(MOS) transistor, a second type of MOS transistor, an etching stop
layer, a first stress layer and a second stress layer is provided.
The substrate has a first active region and a second active region.
The first active region is isolated from the second active region
through an isolation structure. The first type of MOS transistor is
disposed in the first active region of the substrate; the second
type of MOS transistor is disposed in the second active region of
the substrate. The etching stop layer covers conformably the first
type of MOS transistor, the second type of MOS transistor and the
isolation structure. The first stress layer is disposed on the
etching stop layer in the first active region and the second stress
layer is disposed on the etching stop layer in the second active
region.
Inventors: |
Chou; Pei-Yu; (Taipei
County, TW) ; Yang; Min-Chieh; (Kaohsiung City,
TW) ; Hung; Wen-Han; (Kaohsiung City, TW) |
Correspondence
Address: |
JIANQ CHYUN INTELLECTUAL PROPERTY OFFICE
7 FLOOR-1, NO. 100
ROOSEVELT ROAD, SECTION 2
TAIPEI
100
TW
|
Family ID: |
38041439 |
Appl. No.: |
11/309204 |
Filed: |
July 13, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11164274 |
Nov 16, 2005 |
|
|
|
11309204 |
Jul 13, 2006 |
|
|
|
Current U.S.
Class: |
438/199 ;
257/274; 257/E21.633; 257/E21.64; 257/E29.266 |
Current CPC
Class: |
H01L 29/7843 20130101;
H01L 29/7833 20130101; H01L 21/823864 20130101; H01L 21/823807
20130101 |
Class at
Publication: |
438/199 ;
257/274 |
International
Class: |
H01L 21/8238 20060101
H01L021/8238; H01L 29/80 20060101 H01L029/80 |
Claims
1. A complementary metal-oxide-semiconductor (CMOS) device,
comprising: a substrate having a first active region and a second
active region, wherein the first active region and the second
active region are isolated from each other through an isolation
structure; a first type of metal-oxide-semiconductor (MOS)
transistor disposed in the first active region of the substrate; a
second type of MOS transistor disposed in the second active region
of the substrate; a etching stop layer covering conformably the
first type of MOS transistor, the second type of MOS transistor and
the isolation structure; a first stress layer disposed on the
etching stop layer in the first active region; and a second stress
layer disposed on the etching stop layer in the second active
region.
2. The CMOS device of claim 1, wherein the material constituting
the first etching stop layer and the second etching stop layer
comprise silicon oxide, silicon oxynitride, silicon carbide,
silicon carbonate or silicon-carbon nitride.
3. The CMOS device of claim 1, wherein each of the first etching
stop layer and the second etching stop layer has a thickness
between 50 .ANG..about.200 .ANG..
4. The CMOS device of claim 1, wherein the material constituting
the first stress layer and the second stress layer comprise silicon
nitride.
5. The CMOS device of claim 1, wherein the first type of MOS
transistor is an N-type MOS (NMOS) transistor and the second type
of MOS transistor is a P-type MOS (PMOS) transistor, then the first
stress layer is a tensile stress layer and the second stress layer
is a compressive stress layer.
6. The CMOS device of claim 1, wherein the first type of MOS
transistor is a P-type MOS (PMOS) transistor and the second type of
MOS transistor is an N-type MOS (NMOS) transistor, then the first
stress layer is a compressive stress layer and the second stress
layer is a tensile stress layer.
7. A metal-oxide-semiconductor (MOS) device, comprising: a
substrate; a conductive type MOS transistor disposed on the
substrate; a etching stop layer covering conformably the conductive
type MOS transistor; and a stress layer disposed on the etching
stop layer.
8. The MOS device of claim 7, wherein the material constituting the
etching stop layer comprises silicon oxide, silicon oxynitride,
silicon carbide, silicon carbonate or silicon-carbon nitride.
9. The MOS device of claim 7, wherein the etching stop layer has a
thickness between 50 .ANG..about.200 .ANG..
10. The MOS device of claim 7, wherein the material constituting
the stress layer comprises silicon nitride.
11. The MOS device of claim 7, wherein the conductive MOS
transistor is an N-type MOS (NMOS) transistor and the stress layer
is a tensile stress layer.
12. The MOS device of claim 7, wherein the conductive MOS
transistor is a P-type MOS (PMOS) transistor and the stress layer
is a compressive stress layer.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a divisional application of application Ser. No.
11/164,274, filed on Nov. 16, 2005, which is now pending. The
entirety of the above-mentioned patent application is hereby
incorporated by reference herein and made a part of this
specification.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a semiconductor device and
fabricating method thereof. More particularly, the present
invention relates to a complementary metal-oxide-semiconductor
(CMOS) device and a metal-oxide-semiconductor (MOS) device and
their fabricating methods therefore.
[0004] 2. Description of the Related Art
[0005] In the development of integrated circuit devices, higher
operating speed and a lower power consumption is often achieved by
reducing the size of each device. However, further reduction in the
dimension of each device is subjected to factors including the
bottleneck in the fabricating technique and the expense in the
production. Consequently, other types of techniques different from
the technique of miniaturizing devices have been developed to
improve the driving current of devices. With this background,
somebody has proposed the utilization of the stress in the channel
region of a transistor to combat the limits in device
miniaturization. The method uses stress to change the pitch of
silicon crystal grid so that the mobility of electrons and holes is
increased and lead to a higher device performance.
[0006] One of the conventional method of utilizing stress to
increase device performance includes using the stress in a silicon
nitride layer that serves as a contact etching stop layer to
influence the driving current of the device. Although the driving
current in the n-channel region will increase when the tensile
stress of the silicon nitride layer is increased, the driving
current in the p-channel region will drop. Conversely, although the
driving current in the p-channel will increase when the compressive
stress of the silicon nitride layer is increased, the driving
current of the n-channel region will drop. In other words, the
method of using the stress in a silicon nitride layer to improve
the performance of the transistor can be used only for increasing
the driving current of a N-type metal-oxide-semiconductor (NMOS)
transistor or the driving current of a P-type
metal-oxide-semiconductor (PMOS) transistor. There is no way to
increase the driving current of both the NMOS transistor and the
PMOS transistor at the same time.
[0007] To increase the driving current of NMOS transistor and PMOS
transistor simultaneously, a method for forming a semiconductor
device with the following steps is proposed. First, an NMOS
transistor and a PMOS transistor are formed on a substrate such
that a shallow trench isolation (STI) structure is also formed
between the two transistors. Hence, the NMOS transistor and the
PMOS transistor are electrically isolated. Thereafter, a silicon
nitride layer with tensile stress is deposited to cover up the
entire substrate. After that, a patterned photoresist layer is
formed over the silicon nitride layer with tensile stress to expose
the silicon nitride layer above the PMOS transistor. Using the
patterned photoresist layer as a mask, an ion implant process is
performed to remove the exposed silicon nitride layer while
retaining the silicon nitride layer on the NMOS transistor. Then,
the patterned photoresist layer is removed. Afterwards, using a
similar method, another silicon nitride layer with compressive
stress is deposited over the entire substrate. Then, the silicon
nitride layer above the NMOS transistor is removed while retaining
the silicon nitride layer with compressive stress over the PMOS
transistor. Consequently, a silicon nitride layer with tensile
stress is formed over the NMOS transistor while another silicon
nitride layer with compressive stress is formed over the PMOS
transistor. In other words, the driving current of both the NMOS
transistor and the PMOS transistor is increased simultaneously.
[0008] Although the aforesaid method can increase the driving
current of both the NMOS transistor and the PMOS transistor, a few
problems that may affect the driving current and performance of the
transistors are not tackled. For example, in areas where the pitch
between devices is small, the silicon nitride layer at different
stress levels may merge together and doubling the thickness of the
silicon nitride layer there. Therefore, the silicon nitride layer
needs to be over-etched in an etching operation in order to ensure
the silicon nitride layer not covered by the photoresist is
completely removed. However, this extended etching may damage the
film layers and elements such as the spacers and silicone dioxide
layer and nickel-silicide of STI structure in the no-transistor
region underneath the silicon nitride layer. Ultimately, there will
be some adverse effects on the performance of the device.
SUMMARY OF THE INVENTION
[0009] Accordingly, at least one objective of the present invention
is to provide a method of forming a complementary
metal-oxide-semiconductor (CMOS) device that can prevent possible
damages to film layers and increase the performance of the
device.
[0010] At least another objective of the present invention is to
provide a complementary metal-oxide-semiconductor (CMOS) device
that can avoid the problem of having damages in the film layers and
provide a higher device performance.
[0011] At least another objective of the present invention is to
provide a method of forming a metal-oxide-semiconductor (MOS)
device that can prevent possible damages to film layers and
increase the performance of the device.
[0012] At least another objective of the present invention is to
provide a metal-oxide-semiconductor (MOS) device that can avoid the
problem of having damages in the film layers and provide a higher
device performance.
[0013] To achieve these and other advantages and in accordance with
the purpose of the invention, as embodied and broadly described
herein, the invention provides a method of forming a complementary
metal-oxide-semiconductor (CMOS) device comprising the following
steps. First, a substrate is provided. The substrate has a first
active region and a second active region. The first active region
is isolated from the second active region through an isolation
structure. Then, a first type of metal-oxide-semiconductor (MOS)
transistor and a second type of MOS transistor are formed on the
first active region and the second active region of the substrate
respectively. Thereafter, a first etching stop layer is formed on
the substrate to cover conformably the first type of MOS
transistor, the second type of MOS transistor and the isolation
structure. Then, a first stress layer and a second etching stop
layer are formed in sequence over the first etching stop layer.
After that, a first photoresist layer is formed on the second
etching stop layer in the first active region. Using the first
photoresist layer as a mask, a portion of the second etching stop
layer and a portion of the first stress layer is removed to expose
the first etching stop layer. Thereafter, the first photoresist
layer is removed. A second stress layer is formed over the
substrate to cover the first etching stop layer and the second
etching stop layer. Then, a second photoresist layer is formed on
the second stress layer in the second active region. Using the
second photoresist layer as a mask, a portion of the second stress
layer is removed to expose the second etching stop layer.
Afterwards, the second photoresist layer and the second etching
stop layer are removed.
[0014] According to the embodiment of the present invention, a
curing process may be carried out after forming the first stress
layer. And a curing process may be carried out after forming the
second stress layer.
[0015] According to the embodiment of the present invention, the
first etching stop layer is fabricated using silicon oxide, silicon
oxynitride, silicon carbide, silicon carbonate or silicon-carbon
nitride and has a thickness between about 50 .ANG..about.200 .ANG.,
for example. Similarly, the second etching stop layer is fabricated
using silicon oxide, silicon oxynitride, silicon carbide, silicon
carbonate or silicon-carbon nitride and has a thickness between
about 50 .ANG..about.200 .ANG., for example.
[0016] According to the embodiment of the present invention, the
first stress layer is fabricated using silicon nitride, for
example. Similarly, the second stress layer is fabricated using
silicon nitride, for example.
[0017] According to the embodiment of the present invention, if the
first type of MOS transistor is an N-type metal-oxide-semiconductor
(NMOS) transistor and the second type of MOS transistor is a P-type
metal-oxide-semiconductor (PMOS) transistor, then the first stress
layer is a tensile stress layer and the second stress layer is a
compressive stress layer. On the other hand, if the first type of
MOS transistor is a P-type metal-oxide-semiconductor (NMOS)
transistor and the second type of MOS transistor is an N-type
metal-oxide-semiconductor (PMOS) transistor, then the first stress
layer is a compressive stress layer and the second stress layer is
a tensile stress layer.
[0018] The present invention also provides a complementary
metal-oxide-semiconductor (CMOS) device. The CMOS device comprises
a substrate, a first type of metal-oxide-semiconductor (MOS)
device, a second type of MOS device, an etching stop layer, a first
stress layer and a second stress layer. The substrate has a first
active region and a second active region. The first active region
and the second active region are isolated from each other through
an isolation structure. The first type of MOS transistor is
disposed in the first active region of the substrate and the second
type of MOS transistor is disposed in the second active region of
the substrate. The etching stop layer is covered conformably the
first type of MOS transistor, the second type of MOS transistor and
the isolation structure. The first stress layer is disposed above
the etching stop layer in the first active region and the second
stress layer is disposed above the etching stop layer in the second
active region.
[0019] According to the embodiment of the present invention, the
etching stop layer is fabricated using silicon oxide, silicon
oxynitride, silicon carbide, silicon carbonate or silicon-carbon
nitride and has a thickness between about 50 .ANG..about.200 .ANG.,
for example.
[0020] According to the embodiment of the present invention, the
first stress layer is fabricated using silicon nitride, for
example. Similarly, the second stress layer is fabricated using
silicon nitride, for example.
[0021] According to the embodiment of the present invention, if the
first type of MOS transistor is an N-type metal-oxide-semiconductor
(NMOS) transistor and the second type of MOS transistor is a P-type
metal-oxide-semiconductor (PMOS) transistor, then the first stress
layer is a tensile stress layer and the second stress layer is a
compressive stress layer. On the other hand, if the first type of
MOS transistor is a P-type metal-oxide-semiconductor (NMOS)
transistor and the second type of MOS transistor is an N-type
metal-oxide-semiconductor (PMOS) transistor, then the first stress
layer is a compressive stress layer and the second stress layer is
a tensile stress layer.
[0022] The present invention also provides a method of forming a
metal-oxide-semiconductor (MOS) device. The method includes the
following steps. First, a conductive type MOS transistor is formed
on a substrate. Then, a etching stop layer is formed over the
substrate to cover conformably the conductive type MOS transistor.
Thereafter, a stress layer is formed over the etching stop
layer.
[0023] According to the embodiment of the present invention, a
curing process may be carried out after forming the stress
layer.
[0024] According to the embodiment of the present invention, the
etching stop layer is fabricated using silicon oxide, silicon
oxynitride, silicon carbide, silicon carbonate or silicon-carbon
nitride and has a thickness between about 50 .ANG..about.200 .ANG.,
for example.
[0025] According to the embodiment of the present invention, the
stress layer is fabricated using silicon nitride, for example.
Furthermore, if the conductive type MOS transistor is an N-type MOS
transistor (NMOS), then the stress layer is a tensile stress layer.
On the other hand, if the conductive type MOS transistor is a
P-type MOS transistor (PMOS), then the stress layer is a
compressive stress layer.
[0026] The present invention also provides a
metal-oxide-semiconductor (MOS) transistor. The MOS transistor
comprises a conductive type MOS transistor, an etching stop layer
and a stress layer. The conductive MOS transistor is disposed on a
substrate. The etching stop layer is covered conformably the
conductive type MOS transistor. Furthermore, the stress layer is
disposed on the etching stop layer.
[0027] According to the embodiment of the present invention, the
etching stop layer is fabricated using silicon oxide, silicon
oxynitride, silicon carbide, silicon carbonate or silicon-carbon
nitride and has a thickness between about 50 .ANG..about.200 .ANG.,
for example.
[0028] According to the embodiment of the present invention, the
stress layer is fabricated using silicon nitride, for example.
Furthermore, if the conductive type MOS transistor is an N-type MOS
transistor (NMOS), then the stress layer is a tensile stress layer.
On the other hand, if the conductive type MOS transistor is a
P-type MOS transistor (PMOS), then the stress layer is a
compressive stress layer.
[0029] In the present invention, an etching stop layer is formed
between the stress layer and the transistor. Hence, the problem of
damaging the spacers and silicone dioxide layer and nickel-silicide
of STI structure in the no-transistor region as in a conventional
method can be avoided. Furthermore, the presence of the etching
stop layer in the present invention will not affect the properties
of the stress layer and hence degrade the stress layer.
[0030] It is to be understood that both the foregoing general
description and the following detailed description are exemplary,
and are intended to provide further explanation of the invention as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The accompanying drawings are included to provide a further
understanding of the invention, and are incorporated in and
constitute a part of this specification. The drawings illustrate
embodiments of the invention and, together with the description,
serve to explain the principles of the invention.
[0032] FIGS. 1A through 1C are schematic cross-sectional views
showing the steps for forming a MOS device according to one
embodiment of the present invention.
[0033] FIGS. 2A through 2G are schematic cross-sectional views
showing the steps for forming a CMOS device according to one
embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] Reference will now be made in detail to the present
preferred embodiments of the invention, examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers are used in the drawings and the description
to refer to the same or like parts.
[0035] FIGS. 1A through 1C are schematic cross-sectional views
showing the steps for forming a MOS device according to one
embodiment of the present invention. First, referring to FIG. 1A, a
conductive type metal-oxide-semiconductor (MOS) transistor 102 is
formed on a substrate 100. In the present embodiment, the
conductive type MOS transistor 102 is an N-type MOS transistor, for
example. The conductive type MOS transistor 102 comprises a gate
dielectric layer 104, a gate 106, a pair of source/drain regions
108 and a pair of spacers 110. In one embodiment, a metal silicide
layer (not shown) may also be formed on the gate 106 and the
source/drain regions 108 to lower the resistance. The metal
silicide layer is fabricated using nickel silicide, tungsten
silicide or cobalt silicide, for example. Since the elements of the
conductive type MOS transistor 102, the materials constituting the
elements and the method of fabricating the conductive type MOS
transistor 102 should be familiar to those knowledgeable in this
field, a detailed description is omitted.
[0036] Referring to FIG. 1B, an etching stop layer 112 is formed
over the substrate 100 to cover conformably the conductive type MOS
transistor 102. The etching stop layer 112 has a thickness smaller
than 500 .ANG., preferably between 50 .ANG..about.200 .ANG.. The
etching stop layer 112 is fabricated using silicon oxide, silicon
oxynitride, silicon carbide, silicon carbonate or silicon-carbon
nitride, for example. The etching stop layer 112 is formed, for
example, by performing a chemical vapor deposition process or other
suitable process.
[0037] Referring to FIG. 1C, a stress layer 114 is formed over the
etching stop layer 112. The stress layer 114 is a silicon nitride
layer having a thickness between 600 .ANG..about.1500 .ANG., for
example. Because the conductive type MOS transistor 102 in the
present embodiment is an NMOS transistor, the stress layer 114 is a
tensile stress layer.
[0038] In one embodiment, a curing process may be carried out after
forming the stress layer 114 for increasing the tensile stress in
the stress layer 114. The aforesaid curing process is an
ultraviolet curing process, for example.
[0039] Obviously, subsequent processes of forming interconnects can
be carried out after forming the stress layer 114. The interconnect
fabrication process includes, for example, forming a dielectric
layer (not shown) over the stress layer 114 and forming a contact
opening (not shown) in the dielectric layer, the stress layer 114
and the etching stop layer 112. Thereafter, a conductive layer (not
shown) is formed in the contact opening to serve as a contact so
that corresponding devices are electrically connected together.
[0040] Obviously, the conductive type MOS transistor 102 in the
foregoing embodiment is illustrated using a NMOS transistor. In
another embodiment, the conductive type MOS transistor 102 can be a
PMOS transistor. In that case, the stress layer 114 is a
compressive stress layer.
[0041] In the aforementioned embodiment, the formation of a stress
layer on the conductive type MOS transistor can affect the driving
current of the device and improve the performance of the device. In
addition, the etching stop layer between the conductive type MOS
transistor and the stress layer can be fabricated using a material
having an etching selectivity ratio different from the silicon
nitride layer, for example. Hence, the etching stop layer can
prevent possible damage to the spacers and silicone dioxide layer
and nickel-silicide of STI structure in the no-transistor
region.
[0042] In the following, a MOS device fabricated using the
aforementioned method is described. Referring to FIG. 1C, a
metal-oxide-semiconductor (MOS) device comprising a conductive type
MOS transistor 102, an etching stop layer 112 and a stress layer
114 is provided. The conductive type MOS transistor 102 is disposed
on a substrate 100. The etching stop layer 112 is covered
conformably the conductive type MOS transistor 102. The etching
stop layer 112 has a thickness smaller than 500 .ANG., and
preferably between 50 .ANG..about.200 .ANG.. The etching stop layer
112 is fabricated using silicon oxide, silicon oxynitride, silicon
carbide, silicon carbonate or silicon-carbon nitride, for example.
Furthermore, the stress layer 114 is disposed on the etching stop
layer 112 and has a thickness between 600 .ANG..about.1500 .ANG.,
for example. If the conductive type MOS transistor 102 is an N-type
MOS (an NMOS) transistor, then the stress layer 114 is a tensile
stress layer. On the other hand, if the conductive type MOS
transistor 102 is a P-type MOS (a PMOS) transistor, then the stress
layer 114 is a compressive stress layer.
[0043] Aside from the aforementioned embodiment, the present
invention can also be implemented in another configuration. FIGS.
2A through 2G are schematic cross-sectional views showing the steps
for forming a CMOS device according to one embodiment of the
present invention. First, referring to FIG. 2A, a substrate 200 is
provided. The substrate 200 has a active region 202 and a active
region 204. The active regions 202 and 204 are isolated from each
other through an isolation structure 206. The isolation structure
206 can be a shallow trench isolation (STI) structure or other
suitable types of isolation structures, for example.
[0044] Referring to FIG. 2B, a first type of MOS transistor 208 and
a second type of MOS transistor 210 are formed in the first active
region 202 and the second active region 204 of the substrate 200
respectively. In the present embodiment, the first type of MOS
transistor 208 and the second type of MOS transistor 210 are NMOS
transistor and PMOS transistor respectively. The first type MOS
transistor 208 comprises a gate dielectric layer 208a, a gate 208b,
a pair of source/drain region 208c and a pair of spacers 208d. The
second type MOS transistor 210 comprises a gate dielectric layer
210a, a gate 210b, a pair of source/drain region 210c and a pair of
spacers 210d. In one embodiment, a metal silicide layer (not shown)
can be formed on the gate 208b and the source/drain regions 208c
and the gate 210b and the source/drain regions 210c to lower the
resistance there. The metal silicide layer is fabricated using
nickel silicide, tungsten silicide or cobalt silicide, for example.
Since the various elements and materials constituting the
aforementioned first type of MOS transistor 208 and second type of
MOS transistor 210 and method of fabricating the same should be
familiar to those persons knowledgeable in this technological
field, a detailed description is omitted.
[0045] Referring to FIG. 2C, a etching stop layer 212 is formed
over the substrate 200 to cover conformably the first type of MOS
transistor 208, the second type of MOS transistor 210 and the
isolation structure 206. The etching stop layer 212 has a
thickness, for example, smaller than 500 .ANG., and preferably
between 50 .ANG..about.200 .ANG.. The etching stop layer 212 is
fabricated using silicon oxide, silicon oxynitride, silicon
carbide, silicon carbonate or silicon-carbon nitride, for example.
The etching stop layer 212 is formed, for example, by performing a
chemical vapor deposition process or other suitable process.
[0046] Thereafter, a stress layer 214 and an etching stop layer 216
are formed in sequence over the etching stop layer 212. In the
present embodiment, the stress layer 214 is fabricated using
silicon nitride, for example. The stress layer 214 serves as a
tensile stress layer and has a thickness between about 600
.ANG..about.1500 .ANG.. In addition, the etching stop layer 216 has
a thickness, for example, smaller than 500 .ANG., and preferably
between 50 .ANG..about.200 .ANG.. The etching stop layer 216 is
fabricated using silicon oxide, silicon oxynitride, silicon
carbide, silicon carbonate or silicon-carbon nitride, for example.
The etching stop layer 216 is formed, for example, by performing a
chemical vapor deposition process or other suitable process. In one
embodiment, a curing process may be carried out after forming the
stress layer 214 so that the tensile stress in the stress layer 214
is further increased. The aforesaid curing process can be an
ultraviolet curing process, for example.
[0047] In the embodiment of the present invention, the etching stop
layers 212 and 216 can be fabricated using the same material or
different materials. Furthermore, the thickness of the etching stop
layers 212 and 216 can be the same or can be different. There are
no particular limitations in the present invention.
[0048] Referring to FIG. 2D, a photoresist layer 218 is formed on
the etching stop layer 216 in the active region 202. Then, using
the photoresist layer 218 as a mask, a portion of the etching stop
layer 216 and a portion of the stress layer 214 are removed to
expose the etching stop layer 212. The method of removing the
etching stop layer 216 and the stress layer 214 includes performing
an etching process, for example.
[0049] Referring to FIG. 2E, the photoresist layer 218 is removed.
Then, another stress layer 220 is formed over the substrate 200 to
cover the etching stop layer 212 and the etching stop layer 216. In
the present embodiment, the stress layer 220 is a silicon nitride
layer, for example. The stress layer 220 is a compressive stress
layer having a thickness between about 600 .ANG..about.1500 .ANG.,
for example.
[0050] Referring to FIG. 2F, a photoresist layer 222 is formed on
the stress layer 220 in the active region 204. Then, using the
photoresist layer 222 as a mask, a portion of the stress layer 220
is removed to expose the etching stop layer 216. The method of
removing the stress layer 216 includes performing an etching
operation, for example. In one embodiment, a curing process may be
carried out after forming the stress layer 220. The aforesaid
curing process can be an ultraviolet curing process, for
example.
[0051] Referring to FIG. 2G, the photoresist layer 222 is removed.
Then, the etching stop layer 216 is removed. The method of removing
the etching stop layer 216 includes performing a wet cleaning
process, for example.
[0052] Obviously, subsequent processes for forming interconnects
can be performed after forming the stress layers 214 and 220. In
the process of fabricating interconnects, a dielectric layer (not
shown) is formed over the substrate 200 to cover the stress layers
214 and 220. Then, a contact opening (not shown) is formed in the
dielectric layer, the stress layers 214 and 220, and the etching
stop layer 212. Thereafter, a conductive layer (not shown) is
formed inside the contact opening to serve as a contact for
electrically connecting corresponding devices together.
[0053] In one embodiment, after removing the photoresist layer 222,
the step of removing the etching stop layer 216 can't be performed
and subsequent processes for forming interconnects can be
performed. In the step of forming a contact opening of
interconnects, a etching process is performed simultaneously on the
etching stop layer 216 while a dielectric layer covered the stress
layers 214 and 220 is etched.
[0054] In the following, a complementary metal-oxide-semiconductor
(CMOS) device fabricated using the aforesaid method is described.
As shown in FIG. 2G, the CMOS device comprises a substrate 200, a
first type of MOS transistor 208, a second type of MOS transistor
210, an etching stop layer 212, a first stress layer 214 and a
second stress layer 220. The substrate 200 has a active region 202
and a active region 204. The first active region 202 and the second
active region 204 are isolated from each other through an isolation
structure 206. The first type of MOS transistor 208 is disposed in
the first active region 202 of the substrate 200 and the second
type of MOS transistor 210 is disposed in the second active region
204 of the substrate 200. The etching stop layer 212 is covered
conformably the first type of MOS transistor 208, the second type
of MOS transistor 210 and the isolation structure 206. The etching
stop layer 212 has a thickness smaller than 500 .ANG., and
preferably between 50 .ANG.200 .ANG., for example. The etching stop
layer 212 is fabricated using silicon oxide, silicon oxynitride,
silicon carbide, silicon carbonate or silicon-carbon nitride, for
example. Furthermore, the stress layer 214 is disposed on the
etching stop layer 214 in the first active region 202 and the
stress layer 220 is disposed on the etching stop layer 214 in the
second active region 204. The stress layers 214 and 220 are
fabricated using silicon nitride, for example. The stress layer 214
is a tensile stress layer while the stress layer 220 is a
compressive stress layer. Furthermore, the stress layers 214 and
220 have a thickness between about 600 .ANG..about.1500 .ANG., for
example.
[0055] In another embodiment, the first type of MOS transistor 208
is a PMOS transistor and the second type of MOS transistor 210 is
an NMOS transistor. In this case, the stress layer 214 is a
compressive stress layer and the stress layer 220 is a tensile
stress layer.
[0056] It should be noted that a tensile stress layer is formed on
an NMOS transistor and a compressive stress layer is formed on a
PMOS transistor to affect the driving current of the device and
increase the performance of the CMOS device at the same time. In
addition, the etching stop layer in the embodiment can prevent
possible damage to the spacers and silicone dioxide layer and
nickel-silicide of STI structure in the no-transistor region so
that the reliability of the process is improved.
[0057] In particular, the etching stop layer in the embodiment of
the present invention protects the spacers and silicone dioxide
layer and nickel-silicide of STI structure in the no-transistor
region against possible damage without causing any adverse effect
on the stress-related properties of the stress layer. The effect of
the etching stop layer on the stress layer can be determined from a
few tests. The results of the tests are listed in Table 1 below.
TABLE-US-00001 TABLE 1 Ion gain Ion gain (%) Experiment #1 1 0
Experiment #2 1.0968 9.68 Experiment #3 1.1019 10.19 Experiment #4
1.0968 9.86
[0058] In Table 1, four different wafers are tested. In experiment
#1, a tensile stress layer is formed on a substrate with devices
thereon and an electrical test is performed thereafter. In
experiment #2, a curing process is carried out after forming the
stress layer and an electrical test is performed thereafter. In
experiment #3, an etching stop layer with a thickness of about 100
.ANG. and a tensile stress layer are formed in sequence over a
substrate with devices thereon. The substrate is cured and then an
electrical test is performed. In experiment #4, an etching stop
layer with a thickness of about 150 .ANG. and a tensile stress
layer are formed in sequence over a substrate with devices thereon.
The substrate is cured and then an electrical test is performed. In
all the aforesaid experiments #1.about.4, the tensile stress layer
has a thickness of about 1000 .ANG..
[0059] According to Table 1, the electrical test value, the ion
gain, obtained in experiment #1 is used as a reference. The
resulting electrical test values (ion gains) in experiment
#2.about.4 are 1.0968 (9.68%), 1.1019 (10.19%) and 1.0968(9.68%)
respectively. The foregoing results show that the electrical test
values obtained from the experiment #3, 4 and the experiment #2 are
very similar. In other words, the etching stop layer in the present
invention has very little effect on the stress-related properties
of the tensile stress layer and the degradation of the tensile
stress layer is minimal.
[0060] Although the tests in Table 1 is performed to determine the
effects on a tensile stress layer, the etching stop layer of the
present invention similarly will not affect the stress-related
properties of a compressive stress layer leading to a degradation
of the compressive stress layer.
[0061] In summary, major advantages of the present invention
includes at least:
[0062] 1. The stress layer on the MOS transistor can affect the
driving current of the device and improve device performance.
Additionally, the present invention can increase the performance
the NMOS device and the PMOS device at the same time.
[0063] 2. The etching stop layer can avoid the problem of having
any damage to the spacers and silicone dioxide layer and
nickel-silicide of STI structure in the no-transistor region.
[0064] 3. The etching stop layer formed between the MOS transistor
and the stress layer in the present invention is able to protect
the spacers and silicone dioxide layer and nickel-silicide of STI
structure in the no-transistor region against possible damage
without causing change in stress-related properties such as
releasing the stress in the stress layer. In other words, the
degradation of the stress layer is minimal.
[0065] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
present invention without departing from the scope or spirit of the
invention. In view of the foregoing, it is intended that the
present invention cover modifications and variations of this
invention provided they fall within the scope of the following
claims and their equivalents.
* * * * *