U.S. patent application number 14/848362 was filed with the patent office on 2015-12-31 for metal gate structure and manufacturing method thereof.
The applicant listed for this patent is United Microelectronics Corp.. Invention is credited to Tzyy-Ming Cheng, Chi-Mao Hsu, Hsin-Fu Huang, Chin-Fu Lin, Min-Chuan Tsai, Shih-Fang Tzou, Chun-Yuan Wu, Chan-Lon Yang.
Application Number | 20150380512 14/848362 |
Document ID | / |
Family ID | 46752803 |
Filed Date | 2015-12-31 |
United States Patent
Application |
20150380512 |
Kind Code |
A1 |
Yang; Chan-Lon ; et
al. |
December 31, 2015 |
METAL GATE STRUCTURE AND MANUFACTURING METHOD THEREOF
Abstract
A method for manufacturing a metal gate structure includes
providing a substrate having a high-K gate dielectric layer and a
bottom barrier layer sequentially formed thereon, forming a work
function metal layer on the substrate, and performing an anneal
treatment to the work function metal layer in-situ.
Inventors: |
Yang; Chan-Lon; (Taipei
City, TW) ; Hsu; Chi-Mao; (Tainan City, TW) ;
Wu; Chun-Yuan; (Yunlin County, TW) ; Cheng;
Tzyy-Ming; (Hsinchu City, TW) ; Tzou; Shih-Fang;
(Hsinchu County, TW) ; Lin; Chin-Fu; (Tainan City,
TW) ; Huang; Hsin-Fu; (Tainan City, TW) ;
Tsai; Min-Chuan; (New Taipei City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
United Microelectronics Corp. |
Hsin-Chu City |
|
TW |
|
|
Family ID: |
46752803 |
Appl. No.: |
14/848362 |
Filed: |
September 9, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13037383 |
Mar 1, 2011 |
9166020 |
|
|
14848362 |
|
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Current U.S.
Class: |
257/407 |
Current CPC
Class: |
H01L 29/42364 20130101;
H01L 29/6659 20130101; H01L 29/42376 20130101; H01L 29/66636
20130101; H01L 29/4966 20130101; H01L 29/165 20130101; H01L 29/665
20130101; H01L 29/517 20130101; H01L 29/7843 20130101; H01L 29/7833
20130101; H01L 29/66545 20130101; H01L 21/28088 20130101 |
International
Class: |
H01L 29/51 20060101
H01L029/51; H01L 29/423 20060101 H01L029/423; H01L 29/49 20060101
H01L029/49 |
Claims
1. A metal gate structure comprising: a high-K gate dielectric
layer; a bottom barrier layer formed on the high-K gate dielectric
layer; a titanium tri-aluminide (TiAl.sub.3) work function metal
layer formed on the bottom barrier layer; a top barrier layer
formed on the TiAl.sub.3 layer; and a low-resistance metal layer
formed on the top barrier layer.
2. The metal gate structure according to claim 1, wherein the
bottom barrier layer comprises titanium nitride (TiN).
3. The metal gate structure according to claim 1, wherein the
bottom barrier layer comprises titanium nitride or tantalum nitride
(TaN).
4. The metal gate structure according to claim 1, wherein the top
barrier layer comprises titanium nitride or titanium oxynitride
(TiON).
5. The metal gate structure according to claim 1, wherein the
high-K gate dielectric layer comprises materials selected from the
group consisting of hafnium oxide (HfO.sub.2), hafnium silicon
oxide (HfSiO.sub.4), hafnium silicon oxynitride (HfSiON), aluminum
oxide (Al.sub.2O.sub.3), lanthanum oxide (La.sub.2O.sub.3),
tantalum oxide (Ta.sub.2O.sub.5), yttrium oxide (Y.sub.2O.sub.3),
zirconium oxide (ZrO.sub.2), strontium titanate oxide
(SrTiO.sub.3), zirconium silicon oxide (ZrSiO.sub.4), and hafnium
zirconium oxide (HfZrO.sub.4).
6. The metal gate structure according to claim 1, wherein the
low-resistance metal layer comprises aluminum (Al).
7. The metal gate structure according to claim 1, wherein
cross-sectional views of the high-K gate dielectric layer, the
bottom barrier layer, the TiAl.sub.3 layer, and the top barrier
layer comprise a U-shape.
8. The metal gate structure according to claim 1, wherein
cross-sectional views of the TiAl.sub.3 layer and the top barrier
layer comprise a U-shape.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a division of U.S. application Ser. No.
13/037,383 filed on Mar. 1, 2011, and incorporated herein by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a metal gate structure and a
manufacturing method thereof, and more particularly, to an n-type
metal gate structure and a manufacturing method thereof.
[0004] 2. Description of the Prior Art
[0005] With a trend towards scaling down size of the semiconductor
device, conventional methods, which are used to achieve
optimization, such as reducing thickness of the gate dielectric
layer, for example the thickness of silicon dioxide layer, have
faced problems such as leakage current due to tunneling effect. In
order to keep progression to next generation, high-K materials are
used to replace the conventional silicon oxide to be the gate
dielectric layer because it decreases physical limit thickness
effectively, reduces leakage current, and obtains equivalent
capacitor in an identical equivalent oxide thickness (EOT).
[0006] On the other hand, the conventional polysilicon gate also
has faced problems such as inferior performance due to boron
penetration and unavoidable depletion effect which increases
equivalent thickness of the gate dielectric layer, reduces gate
capacitance, and worsens a driving force of the devices. Thus work
function metals are developed to replace the conventional
polysilicon gate to be the control electrode that competent to the
high-K gate dielectric layer.
[0007] However, there is always a continuing need in the
semiconductor processing art to develop semiconductor device
renders superior performance and reliability even though the
conventional silicon dioxide or silicon oxynitride gate dielectric
layer is replaced by the high-K gate dielectric layer and the
conventional polysilicon gate is replaced by the metal gate.
SUMMARY OF THE INVENTION
[0008] According to an aspect of the present invention, there is
provided a metal gate structure. The metal gate structure includes
a high-K gate dielectric layer, a bottom barrier layer formed on
the high-K gate dielectric layer, a titanium tri-aluminide
(TiAl.sub.3) work function metal layer formed on the bottom barrier
layer, a top barrier layer formed on the TiAl.sub.3 work function
metal layer, and a low-resistance metal layer formed on the top
barrier layer.
[0009] According to another aspect of the present invention, there
is provided a method for manufacturing a metal gate structure. The
method includes providing a substrate having a high-K gate
dielectric layer and a bottom barrier layer sequentially formed
thereon, forming a work function metal layer on the substrate, and
performing an anneal treatment to the work function metal layer
in-situ.
[0010] According to the metal gate structure and the method for
manufacturing a metal gate structure provided by the present
invention, the anneal treatment is in-situ performed to induce a
phase transformation of the work function metal layer to form a
TiAl.sub.3 work function metal layer and simultaneously to improve
Al diffusion and thus the work function of the metal gate structure
is tuned to an ideal value: 3.9-4.3 eV. In other word, the method
for manufacturing a metal gate structure is performed to provide a
metal gate structure having superior reliability.
[0011] These and other objectives of the present invention will no
doubt become obvious to those of ordinary skill in the art after
reading the following detailed description of the preferred
embodiment that is illustrated in the various figures and
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIGS. 1-7 are schematic drawings illustrating a method for
manufacturing a metal gate structure provided by a first preferred
embodiment of the present invention; wherein FIG. 4 is a schematic
drawing illustrating a modification to the first preferred
embodiment.
[0013] FIGS. 8-10 are schematic drawings illustrating a method for
manufacturing a metal gate structure provided by a second preferred
embodiment of the present invention.
DETAILED DESCRIPTION
[0014] Please refer to FIGS. 1-7, which are schematic drawings
illustrating a method for manufacturing a metal gate structure
provided by a first preferred embodiment of the present invention.
It is noticeable that the preferred embodiment is performed with
the gate-last process. As shown in FIG. 1, a substrate 100 such as
a silicon substrate, a silicon-containing substrate, or a
silicon-on-insulator (SOI) substrate is provided, and a plurality
of shallow trench isolations (STIs) 102 is formed in the substrate
100 for providing electrical isolation. Then, at least a
semiconductor device 110 is formed on the substrate 100. The
semiconductor device 110 includes a gate structure 120, and the
gate structure 120 includes a gate dielectric layer, a titanium
nitride (TiN) layer 124, a dummy gate 128 such as a polysilicon
layer, and a patterned hard mask (not shown). The abovementioned
layers are upwardly and sequentially formed on the substrate 100.
The TiN layer 124 serves as an etch stop layer and a bottom barrier
layer. Furthermore, the gate structure 120 also includes an
interfacial layer (not shown) formed prior to the gate dielectric
layer. It is noteworthy that the preferred embodiment is integrated
with the high-K first process, accordingly the gate dielectric
layer includes a high-K gate dielectric layer 122, which includes
materials selected from the group consisting of hafnium oxide
(HfO.sub.2), hafnium silicon oxide (HfSiO.sub.4), hafnium silicon
oxynitride (HfSiON), aluminum oxide (Al.sub.2O.sub.3), lanthanum
oxide (La.sub.2O.sub.3), tantalum oxide (Ta.sub.2O.sub.5), yttrium
oxide (Y.sub.2O.sub.3), zirconium oxide (ZrO.sub.2), strontium
titanate oxide (SrTiO.sub.3), zirconium silicon oxide
(ZrSiO.sub.4), and hafnium zirconium oxide (HfZrO.sub.4).
[0015] Please still refer to FIG. 1. The semiconductor device 110
further includes light doped drains (LDDs) 112. Since the
semiconductor device 110 provided by the preferred embodiment is an
n-type semiconductor device, the LDDs 112 are an n-type LDDs. The
semiconductor device 110 further includes a spacer 114 formed on
sidewalls of the gate structure 120, and the spacer 114 is
preferably a multi-layered structure. The semiconductor device 110
further includes an n-type source/drain 116 and silicides 118 for
reducing resistance formed on the source/drain 116. Additionally,
selective epitaxial growth (SEG) method can be utilized to form the
source/drain 116 in the preferred embodiment. As mentioned above,
since the semiconductor device 110 is an n-type semiconductor
device, epitaxial silicon layers with silicon carbide (SiC) can be
used to form the n-type source/drain 116. Furthermore, there are a
contact etch stop layer (CESL) 130 and an inter-layer dielectric
(ILD) layer 132 sequentially formed on the semiconductor device 110
and the substrate 100. Since steps for forming the gate structure
120, the LDDs 112, the spacer 114, the source/drain 116, the
silicides 118, the CESL 130 and the ILD layer 132 are well-known to
those skilled in the art, those details are omitted herein in the
interests of brevity.
[0016] Please refer to FIG. 1 and FIG. 2. Next, a planarization
process is performed to remove a portion of the ILD layer 132, a
portion of the CESL 130, and the patterned hard mask. Consequently
the top of the dummy gate 128 is exposed. Then, an etching process
is performed to remove the dummy gate 128 to form a gate trench
108. As mentioned above, the TiN layer 124 serves as an etch stop
layer, therefore the TiN layer 124 is exposed in the gate trench
108 after removing the dummy gate 128 as shown in FIG. 2.
Accordingly, the high-K gate dielectric layer 122 is protected from
the etching process by the TiN layer 124.
[0017] Please refer to FIG. 3. After forming the gate trench 108, a
tantalum nitride (TaN) layer 126 and a titanium aluminide (TiAl)
layer 140 are sequentially formed on the substrate 100 and in the
gate trench 108. Please note that the TaN layer 126 and the TiN
layer 124 both serve as the bottom barrier layer while the TiAl
layer 140 serves as a work function metal layer. In the preferred
embodiment, the TiAl layer 140 is a single-layered structure.
Please refer to FIG. 4, which is a schematic drawing illustrating a
modification to the first preferred embodiment. According to the
modification, the work function metal layer 140 is a bi-layered
structure, and the bi-layered structure includes a Ti/Al bi-layered
structure as shown in FIG. 4.
[0018] Please refer to FIG. 3 and FIG. 4. It is noteworthy that
during forming the work function metal layer, that is the TiAl
layer 140 or the Ti/Al bi-layered structure 140, the work function
metal layer 140 is formed in a vacuum environment. After forming
the TiAl layer 140, an anneal treatment 150 is in-situ performed to
the work function metal layer 140 without removing the vacuum
environment. In other words, the step of forming the work function
metal layer 140 and the step of performing the anneal treatment 150
are in-situ performed in a vacuum environment. In the preferred
embodiment, the anneal treatment 150 is performed at a temperature
between 400.degree. C. and 460.degree. C., and in a duration
between 2 minutes and 10 minutes. The anneal treatment 150 includes
a rapid thermal process (RTP), a Laser-spike annealing, or a
furnace, but not limited to this. In addition, the anneal treatment
150 further includes introducing inert gas such as argon (Ar).
However, the anneal treatment 150 is performed without introducing
any oxygen-containing gas.
[0019] Please refer to FIG. 5. It is noteworthy that the anneal
treatment 150 is performed to the work function metal layer 140 to
induce a phase transformation from the TiAl layer 140 to a titanium
tri-aluminide (TiAl.sub.3) layer 140a. When the anneal treatment
150 are not in-situ performed or not performed in this timing, such
as phase transformation would not happen. More important, during
the phase transformation from the TiAl work function metal layer
140 to the TiAl.sub.3 work function metal layer 140a, aluminum (Al)
in the aforementioned layer diffuses to the interface between the
TiN layer 124 and the high-K gate dielectric layer 122 and finally
arrives at the surface of the high-K gate dielectric layer 122.
Simultaneously, work function of the gate structure is tuned.
Accordingly, by in-situ performing the anneal treatment 150, Al
diffusion is improved, and work function of the n-type gate is
tuned to an ideal value: 3.9-4.3 eV. Furthermore, since the anneal
treatment 150 is performed without removing the vacuum environment,
the TiAl layer 140 is avoided from contacting the air, and thus is
prevented from forming oxide or nitride that seriously deteriorates
the performance.
[0020] Please refer to FIGS. 5-6. After performing the anneal
treatment 150 to form the TiAl.sub.3 work function metal layer
140a, a top barrier layer 142 such as a TiN layer is in-situ formed
on the TiAl.sub.3 work function metal layer 140a. Then, the vacuum
environment is removed. Additionally, a titanium oxynitride (TiON)
layer serving as the top barrier layer 142 can be formed after
removing the vacuum environment. After forming the top barrier
layer 142, a low-resistance metal layer 144 filling the gate trench
108 is formed on the substrate 100 and the top barrier layer 142 as
shown in FIG. 6. The low-resistance metal layer 144 can be an Al
layer, but not limited to this.
[0021] Please refer to FIG. 7. Then, a planarization process such
as a chemical mechanical polish (CMP) process is performed to
remove unnecessary low-resistance metal layer 144, top barrier
layer 142, TiAl.sub.3 work function metal layer 140a, and TaN layer
126. Consequently, a metal gate structure 120a is obtained. As
shown in FIG. 7, cross-sectional views of the TaN layer 126, the
TiAl.sub.3 work function metal layer 140a, and the top barrier
layer 142 of the metal gate structure 120a respectively include a
U-shape according to the preferred embodiment. In addition, the ILD
layer 132 and the CESL 130 can be selectively removed and
sequentially reformed with a tensile stress on the substrate 100
for improving performance of the semiconductor device 110 in the
preferred embodiment. Besides, the above-mentioned silicides 118
can be formed after the ILD layer 132 and the CESL 130 is
selectively removed so as not to be damaged by the high temperature
of forming the metal gate.
[0022] According to the method for manufacturing a metal gate
structure provided by the first preferred embodiment, which is
integrated with the high-K first process, the anneal treatment 150
is in-situ performed to induce the phase transformation from the
TiAl work function metal layer 140 to the TiAl.sub.3 work function
metal layer 140a, and simultaneously to improve Al diffusion.
Accordingly, work function of the metal gate is tuned to the ideal
value: 3.9-4.3 eV. In other words, according to the method provided
by the first preferred embodiment, a metal gate structure 120a
having ideal work function is obtained.
[0023] Please refer to FIGS. 8-10, which are schematic drawings
illustrating a method for manufacturing a metal gate structure
provided by a second preferred embodiment of the present invention.
It is noticeable that the preferred embodiment is also performed
with the gate-last process. Additionally, material choices for
elements the same in both of the first and second preferred
embodiment are omitted herein in the interest of brevity.
[0024] As shown in FIG. 8, a substrate 200 having a plurality of
STI 202 formed therein is provided. The STIs 202 are formed to
provide electrical isolation. Next, at least a semiconductor device
210 is formed on the substrate 200. The semiconductor device 210
includes a gate structure (not shown), and the gate structure
includes a gate dielectric layer (not shown), a dummy gate (not
shown) and a patterned hard mask (not shown). The abovementioned
layers are upwardly and sequentially formed on the substrate 200.
Furthermore, the gate structure also includes an interfacial layer
(not shown) formed prior to the gate dielectric layer. It is
noteworthy that the preferred embodiment is integrated with the
high-K last process, therefore the gate dielectric layer is
preferably a conventional SiO layer.
[0025] The semiconductor device 210 further includes LDDs 212.
Since the semiconductor device 210 provided by the preferred
embodiment is an n-type semiconductor device, the LDDs 212 are
n-type LDDs. The semiconductor device 210 further includes a spacer
214 formed on sidewalls of the gate structure, and the spacer 214
is preferably a multi-layered structure. The semiconductor device
210 further includes an n-type source/drain 216 and silicides 218
for reducing resistance formed on the source/drain 216. As
mentioned above, the SEG method can be utilized to form a SiC
n-type source/drain 216 according to the preferred embodiment.
Furthermore, there are a CESL 230 and an ILD layer 232 sequentially
formed on the semiconductor device 210 and the substrate 200. Since
steps for forming the gate structure, the LDDs 212, the spacer 214,
the source/drain 216, the silicides 218, the CESL 230 and the ILD
layer 232 are well-known to those skilled in the art, those details
are omitted herein in the interests of brevity.
[0026] Please refer to FIG. 8 again. Next, a planarization process
is performed to remove a portion of the ILD layer 232, a portion of
the CESL 230, and the patterned hard mask. Consequently the top of
the dummy gate is exposed. Then, an etching process is performed to
remove the dummy gate and the gate dielectric layer to form a gate
trench 208. As mentioned above, since the preferred embodiment is
integrated with the high-K last process, the gate dielectric layer
and the dummy gate are both removed. Accordingly, the substrate 200
or the interfacial layer is exposed in the bottom of the gate
trench 208.
[0027] Please still refer to FIG. 8. Then, a high-K gate dielectric
layer 222, a TiN layer 224 serving as a bottom barrier layer are
sequentially formed on the substrate 200 and in the gate trench
208. Additionally, a TaN layer (not shown) can be selectively
formed on the TiN layer 224 if required. After forming the TiN
layer 224, a TiAl layer 240 serving as a work function metal layer
is formed on the substrate 200 and in the gate trench 208. In the
preferred embodiment, the TiAl layer 240 is a single-layered
structure. However, the work function metal layer 240 can be a
Ti/Al bi-layered structure according to the preferred
embodiment.
[0028] As mentioned above, during forming the work function metal
layer, that is the TiAl layer 240 or the Ti/Al bi-layered structure
240, the work function metal layer 240 is formed in a vacuum
environment. According to the preferred embodiment, an anneal
treatment 250 is in-situ performed to the work function metal layer
240 after forming the TiAl layer 240 without removing the vacuum
environment. In other words, the step of forming the work function
metal layer 240 and the step of performing the anneal treatment 250
are in-situ performed in a vacuum environment. In the second
preferred embodiment, the anneal treatment 250 is performed at a
temperature and in a duration the same with those described in the
first preferred embodiment, therefore those details are omitted for
the sake of simplicity.
[0029] As mentioned above, the anneal treatment 250 is performed to
the work function metal layer 240 to induce a phase transformation
from the TiAl layer 240 to a TiAl.sub.3 layer 240a. More important,
during the phase transformation from the TiAl work function metal
layer 240 to the TiAl.sub.3 work function metal layer 240a, Al in
the aforementioned layer diffuses to the interface between the TiN
layer 224 and the high-K gate dielectric layer 222 and finally
arrives at the surface of the high-K gate dielectric layer 222.
Simultaneously, work function of the gate structure is tuned.
Accordingly, by in-situ performing the anneal treatment 250, Al
diffusion is improved, and work function of the n-type metal gate
is tuned to the ideal value: 3.9-4.3 eV. Furthermore, since the
anneal treatment 250 is performed without removing the vacuum
environment, the TiAl layer 240 is avoided from contacting the air,
and thus is prevented from forming oxide or nitride that
deteriorates the performance.
[0030] Please refer to FIG. 9. After performing the anneal
treatment 250 to form the TiAl.sub.3 work function metal layer
240a, a top barrier layer 242 such as a TiN layer is in-situ formed
on the TiAl.sub.3 work function metal layer 240a. Then, the vacuum
environment is removed. Additionally, a TiON layer serving as the
top barrier layer 242 can be formed after removing the vacuum
environment. After forming the top barrier layer 242, a
low-resistance metal layer 244 filling the gate trench 208 is
formed on the substrate 200 and the top barrier layer 242 as shown
in FIG. 9. The low-resistance metal layer 244 can be an Al layer,
but not limited to this.
[0031] Please refer to FIG. 10. Then, a planarization process such
as a CMP process is performed to remove unnecessary low-resistance
metal layer 244, top barrier layer 242, TiAl.sub.3 work function
metal layer 240a, bottom barrier layer 224, and high-K gate
dielectric layer 222. Consequently, a metal gate structure 220a is
obtained. As shown in FIG. 10, cross-sectional views of the high-K
gate dielectric layer 222, the bottom barrier layer 224, the
TiAl.sub.3 work function metal layer 240a, and the top barrier
layer 242 of the metal gate structure 220a respectively include a
U-shape according to the preferred embodiment. Similarly, the ILD
layer 232 and the CESL 230 can be selectively removed and
sequentially reformed on the substrate 200 for improving
performance of the semiconductor device 210 in the preferred
embodiment.
[0032] According to the method for manufacturing a metal gate
structure provided by the second preferred embodiment, which is
integrated with the high-K last process, the anneal treatment 250
is in-situ performed to induce the phase transformation from the
TiAl work function metal layer 240 to the TiAl.sub.3 work function
metal layer 240a and simultaneously improves Al diffusion.
Accordingly, work function of the metal gate is tuned to an ideal
value: 3.9-4.3 eV. In other words, according to the method provided
by the second preferred embodiment, a metal gate structure 220a
having ideal work function is obtained.
[0033] Accordingly, the present invention provides a method for
manufacturing metal gate structure performed with the gate-last
process and can be integrated alternatively with high-K first or
high-K last process. More important, the provided method utilizes
the in-situ performed anneal treatment to induce the phase
transformation of the work function metal layer from the TiAl work
function metal layer to the TiAl.sub.3 work function metal layer.
Simultaneously, Al diffusion is improved and thus the work function
of the metal gate is tuned to the ideal value: 3.9-4.3 eV. In other
word, the method for manufacturing a metal gate structure is
performed to provide an n-type metal gate structure having superior
reliability.
[0034] Those skilled in the art will readily observe that numerous
modifications and alterations of the device and method may be made
while retaining the teachings of the invention. Accordingly, the
above disclosure should be construed as limited only by the metes
and bounds of the appended claims.
* * * * *