U.S. patent application number 09/942645 was filed with the patent office on 2002-02-28 for method of manufacturing a capacitor in a semiconductor device.
Invention is credited to Kim, Kyong Min, Kim, You Sung, Lim, Chan, Park, Chang Seo, Song, Han Sang.
Application Number | 20020025649 09/942645 |
Document ID | / |
Family ID | 19611393 |
Filed Date | 2002-02-28 |
United States Patent
Application |
20020025649 |
Kind Code |
A1 |
Song, Han Sang ; et
al. |
February 28, 2002 |
Method of manufacturing a capacitor in a semiconductor device
Abstract
The present invention relates to a method of manufacturing a
capacitor in a semiconductor device. It is designed to solve the
problem due to oxidization of the surface of the underlying
tungsten electrode during thermal process performed after
depositing Ta.sub.2O.sub.5 to form a dielectric film in a
Ta.sub.2O.sub.5 capacitor of a MIM (Metal Insulator Metal)
structure using tungsten (W) as an underlying electrode. Thus, the
present invention includes forming a good thin WO.sub.3 film by
processing the surface of the underlying tungsten electrode by low
oxidization process before forming a Ta.sub.2O.sub.5 dielectric
film and then performing deposition and thermal process of
Ta.sub.2O.sub.5 to form a Ta.sub.2O.sub.5 dielectric film. As a
good WO.sub.3 film is formed on the surface of the underlying
tungsten electrode before forming a Ta.sub.2O.sub.5 dielectric
film, the grain boundary of the tungsten film is filled with oxygen
atoms, thus preventing diffusion of oxygen atoms from the
Ta.sub.2O.sub.5 dielectric film during a subsequent thermal
process. Also, as a further oxidization of the surface of the
underlying tungsten electrode by the WO.sub.3 film could be
prevented, thereby improving the characteristic of the leak current
of the Ta.sub.2O.sub.5 capacitor.
Inventors: |
Song, Han Sang; (Yongin-Shi,
KR) ; Kim, You Sung; (Seoul, KR) ; Lim,
Chan; (Ichon-Shi, KR) ; Park, Chang Seo;
(Ichon-Shi, KR) ; Kim, Kyong Min; (Anyang-Shi,
KR) |
Correspondence
Address: |
PENNIE & EDMONDS LLP
1667 K STREET NW
SUITE 1000
WASHINGTON
DC
20006
|
Family ID: |
19611393 |
Appl. No.: |
09/942645 |
Filed: |
August 31, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09942645 |
Aug 31, 2001 |
|
|
|
09659508 |
Sep 11, 2000 |
|
|
|
Current U.S.
Class: |
438/397 ;
257/E21.008; 257/E21.01; 257/E21.011; 257/E21.274 |
Current CPC
Class: |
H01L 21/31604 20130101;
H01L 28/60 20130101; H01L 28/56 20130101; H01L 28/40 20130101 |
Class at
Publication: |
438/397 |
International
Class: |
H01L 021/20 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 14, 1999 |
KR |
99-39221 |
Claims
What is claimed is:
1. A semiconductor device having a capacitor comprising: a
substrate containing an underlying structure; a tungsten electrode
formed on the substrate; a WO.sub.3 film formed on the surface of
the tungsten; a dielectric film formed on the WO.sub.3 film; and a
upper electrode formed on the dielectric film, wherein, the
WO.sub.3 film prevents the diffusion of oxygen atoms from the
dielectric film into the tungsten film.
2. A capacitor comprising: a tungsten electrode supported by a
substrate; a WO.sub.3 film formed on the surface of the tungsten; a
dielectric film formed on the WO.sub.3 film; and a upper electrode
formed on the dielectric film, wherein, the WO.sub.3 film prevents
the diffusion of oxygen atoms from the dielectric film into the
tungsten film.
Description
RELATED APPLICATIONS
[0001] This is a Divisional of U.S. patent application Ser. No.
09/659,508, filed Sep. 11, 2000, now U.S. Pat. No. ______.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates generally to a method of manufacturing
a capacitor in a semiconductor device, and more particularly to, a
method of manufacturing a capacitor in a semiconductor device which
can prevent oxidization of the surface of an underlying electrode
to improve the characteristic of the leak current of a
Ta.sub.2O.sub.5 capacitor, upon a thermal treatment process
performed after Ta.sub.2O.sub.5 is deposited in order to form a
dielectric film, in a Ta.sub.2O.sub.5 capacitor of a MIM (Metal
Insulator Metal) structure using tungsten (W) as an underlying
electrode.
[0004] 2. Description of the Prior Art
[0005] Generally, when manufacturing a Ta.sub.2O.sub.5capacitor in
a memory device, if metal materials such as Tungsten are used as
underlying electrode materials, the work function of the metal
materials with poly-silicon is large. Thus, the thickness of the
effective oxide film Tox can be reduced and thus the leak current
in the thickness of the same effective oxide film can also be
reduced. Further, the value of .DELTA.C depending on the bias
voltage is small. As a Ta.sub.2O.sub.5 dielectric film lacks oxygen
in the film formed by Ta.sub.2O.sub.5 deposition process and also
contains impurities such as carbon or hydrogen etc., in order to
secure the dielectric characteristic of the Ta.sub.2O.sub.5
capacitor, oxygen must be flowed into it and a subsequent process
for removing impurities must be performed after the Ta.sub.2O.sub.5
deposition is completed.
[0006] This subsequent process is mainly thermally performed under
oxygen atmosphere at a higher temperature, thus securing the
dielectric characteristic of a Ta.sub.2O.sub.5 dielectric film.
However, if the temperature of the thermal process is too high or
the time of the thermal treatment is too long, upon thermal
treatment process, the surface of the underlying tungsten electrode
is oxidized to form a WO.sub.3 film. The WO.sub.3 film has the
dielectric constant of about 42, which is higher than that of
Ta.sub.2O.sub.5 dielectric film having about 25. However, when
creating the WO.sub.3 film, there is a possibility that oxygen
within the Ta.sub.2O.sub.5 dielectric film can be diffused into the
underlying tungsten electrode. Also, due to the difference of the
thermal expansion coefficient with the Ta.sub.2O.sub.5 dielectric
film, there is a problem that the characteristic of the leak
current of the Ta.sub.2O.sub.5 capacitor becomes degraded since a
phenomenon of film lifting of the film is generated.
SUMMARY OF THE INVENTION
[0007] It is therefore an object of the present invention to
provide a method of manufacturing a capacitor in a semiconductor
device which can prevent oxidization of the surface of an
underlying electrode to improve the characteristic of the leak
current of a Ta.sub.2O.sub.5 capacitor, upon a thermal treatment
process performed after Ta.sub.2O.sub.5 is deposited in order to
form a dielectric film, in a Ta.sub.2O.sub.5 capacitor of a MIM
(Metal Insulator Metal) structure using tungsten (W) as an
underlying electrode.
[0008] In order to accomplish the object, a method of manufacturing
a capacitor in a semiconductor device according to the present
invention is characterized in that it comprises the steps of
forming an underlying tungsten electrode on a substrate in which an
underlying structure is formed; forming a WO.sub.3 film on the
surface of the underlying tungsten electrode; forming a
Ta.sub.2O.sub.5 dielectric film on the WO.sub.3 film; and forming
an upper electrode on the Ta.sub.2O.sub.5 dielectric film.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The aforementioned aspects and other features of the present
invention will be explained in the following description, taken in
conjunction with the accompanying drawings, wherein:
[0010] FIGS. 1A through 1D are sectional views for illustrating a
method of manufacturing a capacitor in a semiconductor device
according to the present invention; and
[0011] FIG. 2 is a graph of I-V characteristic for showing the leak
current characteristic of a capacitor depending on a thermal
process under a low temperature oxygen atmosphere before a
Ta.sub.2O.sub.5 dielectric film is formed.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0012] The present invention will be described in detail by way of
a preferred embodiment with reference to accompanying drawings, in
which like reference numerals are used to identify the same or
similar parts.
[0013] FIGS. 1A through 1D are sectional views for illustrating a
method of manufacturing a capacitor in a semiconductor device
according to the present invention.
[0014] Referring now to FIG. 1A, a first doped poly-silicon layer 1
is formed on a substrate 10 in which an underlying structure is
formed. Then, a barrier metal layer 2 is formed on the first doped
poly-silicon layer 1.
[0015] In the above, the barrier metal layer 2 is formed of a Ti
film and a TiN film. The Ti film is formed by depositing Ti in 100
through 200 .ANG. thickness by means of sputtering method. The TiN
film is formed in 100 through 200 .ANG. thickness by means of metal
organic chemical vapor deposition (MOCVD) method using
Ti(N(CH.sub.3).sub.2).sub.4(TDMAT) as raw materials and using He
and Ar as carrier gases. At this time, the deposition conditions
include 200-300 sccm in the flow rate of raw materials; 100 through
300 sccm in the flow rate of He and Ar, respectively, being carrier
gases; 2-10 Torr in the pressure within the reactive furnace and
300-500.degree. C. in the temperature within the reactive furnace.
Thereafter, a plasma process is performed for about 20 through 50
seconds with the power of 500 through 1000 W.
[0016] Referring now to FIG. 1B, a tungsten film 3 is formed on the
barrier metal layer 2 to complete an underlying electrode.
[0017] In the above, the tungsten film 3 is formed by chemical
vapor deposition (CVD) method under the conditions that WF.sub.6is
used as raw materials, H.sub.2 is used as a reactive gas, the
pressure within the reactive furnace is maintained at 80-110 Torr,
and the temperature within the reactive furnace is maintained at
the temperature of 350-450.degree. C.
[0018] Referring to FIG. 1C, after removing a native oxide film in
which impurities created on the surface of the tungsten film 3 are
contained by means of cleaning process, a WO.sub.3 film 100 is
forcedly formed on the surface of the tungsten film 3. Then, a
Ta.sub.2O.sub.5 dielectric film 4 is formed on the WO.sub.3 film
100.
[0019] In the above, the cleaning process is performed using 50:1
HF for 30 through 50 seconds. The WO.sub.3 film 100 is formed in
thickness of 10-30 .ANG. by oxidizing the tungsten film 3 by means
of Rapid Thermal Anneal (RTA), plasma process or UV/O.sub.3 process
etc. under a low temperature oxygen atmosphere. The WO.sub.3 film
100 formed thus is good in the quality of the film and also fills
the grain boundary of the tungsten film 3 with oxygen atoms. The
rapid thermal process is performed under the atmospheres of O.sub.2
or N.sub.2O at the temperature of 450-550.degree. C. for 5-20
seconds. The plasma process is performed under the atmospheres of
O.sub.2 or N.sub.2O at the temperature of 300-550.degree. C. for
30-120 seconds by the power of 200-500 W. The UV/O.sub.3 process is
performed at the temperature of 300-550.degree. C. for 2-5 minutes
at the strength of 15-30 mW/cm.sup.2.
[0020] The Ta.sub.2O.sub.5 dielectric film 4 is deposited with use
Ta.sub.2O.sub.5 under the conditions that Ta(C.sub.2H.sub.5O).sub.5
is used as raw materials, N.sub.2 gas and O.sub.2 gas is used as a
carrier gas and an oxidizer, respectively, the flow rate of the
N.sub.2gas is maintained at 350-450 sccm, the flow rate of the
O.sub.2 gas is maintained at 20-50 sccm, the pressure within the
reactive furnace is maintained at 0.1-0.6 Torr, and the temperature
within the reactive furnace is maintained at 350-450.degree. C.
Then, in order to prevent oxidization of the tungsten film 3 being
an underlying electrode while obtaining a dielectric
characteristic, the Ta.sub.2O.sub.5 dielectric film 4 is
experienced by a rapid thermal process by mixing inactive gases
such as N.sub.2, Ar, He etc. in N.sub.2O gas or O.sub.2 gas at the
temperature of 550-700.degree. C. for 20-60 seconds, or by a plasma
annealing process under oxygen atmosphere using O.sub.2 gas or
N.sub.2O gas by which a plasma power of 10-100 W is applied at the
temperature of less 350.degree. C.
[0021] Referring to FIG. 1D, a TiN film 5 and a second doped
poly-silicon layer 6 are sequentially formed on the Ta.sub.2O.sub.5
dielectric film 4, thus completing an upper electrode of a
capacitor. By means of a series of these processes, a
Ta.sub.2O.sub.5 capacitor of a MIM structure is manufactured.
[0022] In the above, the TiN film 5 is formed in thickness of
200-500 .ANG. by means of chemical vapor deposition (CVD) method
under the conditions that TiCl.sub.4 is used as raw materials,
NH.sub.3 gas is used as a reactive gas, the temperature within the
reactive furnace is maintained at 300-500.degree. C. and the
pressure within the reactive furnace is maintained at 0.1-2 Torr.
The second poly-silicon layer 6 is formed in thickness of 800-1200
.ANG.. The TiN film 5 functions to reduce the work function with
the second poly-silicon layer 6 and the Ta.sub.2O.sub.5 dielectric
film 4.
[0023] FIG. 2 is a graph of I-V characteristic for illustrating the
leak current characteristic of a capacitor when comparing the
method according to the present invention by which O.sub.2-RTA is
performed at the temperature of 500.degree. C. under the atmosphere
of oxygen with the conventional method in which no process is
performed before a Ta.sub.2O.sub.5 dielectric film is formed.
[0024] In order to compare the leak current characteristic, the
Ta.sub.2O.sub.5 dielectric films in the present invention and the
conventional method are formed identically. As shown in FIG. 2, the
thickness of the effective oxide film Tox is almost same in both
cases of the conventional method and the present invention.
However, it could be seen that the leak current in the present
invention has been greatly improved. In other words, the leak
current at LV in the conventional method shows 4.32E-5 (A/cm.sup.2)
while that in the present invention shows 2.58E-8 (A/cm.sup.2).
Also, it could be seen that the leak current in the present
invention is greatly improved even in the negative voltage.
[0025] As can be understood from the above description with the
present invention, the present invention forms a good WO.sub.3 film
on the surface of the underlying tungsten electrode before forming
a Ta.sub.2O.sub.5 dielectric film in a Ta.sub.2O.sub.5 capacitor
using tungsten as an underlying electrode. As the grain boundary of
the tungsten film is filled with oxygen atoms, diffusion of oxygen
atoms from the Ta.sub.2O.sub.5 dielectric film can be prevented
during a subsequent thermal process. Thus, the intrinsic
characteristic of the Ta.sub.2O.sub.5 dielectric film can be
intact. Also, a further oxidization of the surface of the
underlying tungsten electrode by the WO.sub.3 film could be
prevented, thereby improving the characteristic of the leak current
of the Ta.sub.2O.sub.5 capacitor.
[0026] The present invention has been described with reference to a
particular embodiment in connection with a particular application.
Those having ordinary skill in the art and access to the teachings
of the present invention will recognize additional modifications
and applications within the scope thereof.
[0027] It is therefore intended by the appended claims to cover any
and all such applications, modifications, and embodiments within
the scope of the present invention.
* * * * *