U.S. patent application number 09/765531 was filed with the patent office on 2001-10-25 for method of forming metal nitride film by chemical vapor deposition and method of forming metal contact and capacitor of semiconductor device using the same.
Invention is credited to Choi, Gil-Heyun, Jeon, In-Sang, Kang, Sang-Bom, Lim, Hyun-Seok.
Application Number | 20010034097 09/765531 |
Document ID | / |
Family ID | 27349608 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010034097 |
Kind Code |
A1 |
Lim, Hyun-Seok ; et
al. |
October 25, 2001 |
Method of forming metal nitride film by chemical vapor deposition
and method of forming metal contact and capacitor of semiconductor
device using the same
Abstract
A method of forming a metal nitride film using chemical vapor
deposition (CVD), and a method of forming a metal contact and a
semiconductor capacitor of a semiconductor device using the same,
are provided. The method of forming a metal nitride film using
chemical vapor deposition (CVD) in which a metal source and a
nitrogen source are used as a precursor, includes the steps of
inserting a semiconductor substrate into a deposition chamber,
flowing the metal source into the deposition chamber, removing the
metal source remaining in the deposition chamber by cutting off the
inflow of the metal source and flowing a purge gas into the
deposition chamber, cutting off the purge gas and flowing the
nitrogen source into the deposition chamber to react with the metal
source adsorbed on the semiconductor substrate, and removing the
nitrogen source remaining in the deposition chamber by cutting off
the inflow of the nitrogen source and flowing the purge gas into
the deposition chamber. Accordingly, the metal nitride film having
low resistivity and a low content of Cl even with excellent step
coverage can be formed at a temperature of 500.degree. C. or lower,
and a semiconductor capacitor having excellent leakage current
characteristics can be manufactured. Also, a deposition speed,
approximately 20 A/cycle, is suitable for mass production.
Inventors: |
Lim, Hyun-Seok;
(Yongin-City, KR) ; Kang, Sang-Bom; (Seoul,
KR) ; Jeon, In-Sang; (Suwon-city, KR) ; Choi,
Gil-Heyun; (Sungnam-city, KR) |
Correspondence
Address: |
MARGER JOHNSON & MCCOLLOM PC
1030 SW MORRISON STREET
PORTLAND
OR
97205
US
|
Family ID: |
27349608 |
Appl. No.: |
09/765531 |
Filed: |
January 19, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
09765531 |
Jan 19, 2001 |
|
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|
09156724 |
Sep 18, 1998 |
|
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|
6197683 |
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Current U.S.
Class: |
438/253 ;
257/E21.019; 257/E21.171; 257/E21.578; 257/E21.584; 438/396;
438/653 |
Current CPC
Class: |
H01L 21/76843 20130101;
H01L 21/28562 20130101; H01L 21/76804 20130101; C23C 16/45553
20130101; C23C 16/34 20130101; H01L 28/91 20130101 |
Class at
Publication: |
438/253 ;
438/396; 438/653 |
International
Class: |
H01L 021/8242; H01L
021/20; H01L 021/44 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 1997 |
KR |
97-49746 |
Jul 22, 1998 |
KR |
98-29581 |
Claims
What is claimed is:
1. A method of forming a semiconductor capacitor by sequentially
forming a lower conductive layer, a dielectric film and an upper
conductive layer on the underlayer of a semiconductor substrate,
wherein the process for forming a lower conductive layer and/or an
upper conductive layer comprises the steps of: (a) inserting a
semiconductor substrate on which the underlayer on the dielectric
film is formed, into a deposition chamber; (b) admitting a metal
source into the deposition chamber (c) chemisorbing a first portion
of the metal source onto the substrate, and physisorbing a second
portion of the metal source onto the substrate; (d) purging the
metal source from the deposition chamber; (e) admitting a nitrogen
source into the deposition chamber; (f) chemisorbing a first
portion of the nitrogen source onto the substrate, and physisorbing
a second portion of the nitrogen source onto the substrate; (g)
reacting the chemisorbed and physisorbed metal source with the
chemisorbed and physisorbed nitrogen source to form a metal nitride
film on the substrate; and (h) purging the nitrogen source from the
deposition chamber.
2. The method as claimed in claim 1, wherein the metal source is
selected from the group consisting of TiCl.sub.4, TiCl.sub.3,
TiI.sub.4, TiBr.sub.2, TiF.sub.4, (C.sub.5H.sub.5).sub.2TiCl.sub.2,
((CH.sub.3).sub.5C.sub.5).sub.2TiCl.sub.2,
C.sub.5H.sub.5TiCl.sub.3, C.sub.9H.sub.10BCl.sub.3N.sub.6Ti,
C.sub.9H.sub.7TiCl.sub.3, (C.sub.5(CH.sub.3).sub.5)TiCl.sub.3,
TiCl.sub.4(NH.sub.3).sub.2, and
(CH.sub.3).sub.5C.sub.5Ti(CH.sub.3).sub.3, and the nitrogen source
is NH.sub.3.
3. The method as claimed in claim 2, wherein the deposition
temperature in the steps (b) through (h) is between 400.degree. C.
and 500.degree. C., and the pressure in the deposition chamber is 1
to 20 torr.
4. The method as claimed in claim 1, wherein TDEAT or TDMAT is used
as the metal source, and NH.sub.3 is used as the nitrogen
source.
5. The method as claimed in claim 4, wherein the deposition
temperature in the steps (b) through (h) is between 250.degree. C.
and 400.degree. C. and the pressure in the deposition chamber is
0.1 to 10 torr.
6. The method as claimed in claim 1, wherein a material selected
from the group consisting of TaBr.sub.5, TaCl.sub.5, TaF.sub.5,
TaI.sub.5, and(C.sub.5(CH.sub.3).sub.5)TaCl.sub.4 is used as the
metal source, and NH.sub.3 is used as the nitrogen source.
7. The method as claimed in claim 6, wherein the deposition
temperature in the steps (b) through (h) is between 400.degree. C.
and 500.degree. C., and the pressure in the deposition chamber is 1
to 20torr.
8. The method as claimed in claim 1, wherein the purge gas is Ar or
N.sub.2.
9. The method as claimed in claim 1, wherein 1-5 sccm of the metal
source flows into the deposition chamber for 1 to 10 seconds, 5-200
sccm of the nitrogen source flows thereinto for 1 to 10 seconds,
and 10-200 sccm of the purge gas flows thereinto for 1 to 10
seconds.
10. The method as claimed in claim 1, wherein an atmospheric gas,
which is at least one selected from the group consisting of Ar, He
and N.sub.2, is continuously flowed into the deposition chamber
during the steps (b) through (h), to maintain a constant pressure
in the deposition chamber.
11. The method as claimed in claim 1, wherein the thickness of the
lower and/or upper conductive layer is controlled by repeating the
steps (b) through (h).
Description
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 09/156,724, filed Sep. 18, 1998, entitled
METHOD OF FORMING METAL NITRIDE FILM CHEMICAL VAPOR DEPOSITION AND
METHOD OF FORMING METAL CONTACT OF SEMICONDUCTOR DEVICE USING THE
SAMEMETHOD OF FORMING METAL NITRIDE FILM CHEMICAL VAPOR DEPOSITION
AND METHOD OF FORMING METAL CONTACT OF SEMICONDUCTOR DEVICE USING
THE SAME.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method of fabricating
semiconductor devices, and more particularly, to a method of
forming a metal nitride film by chemical vapor deposition (CVD)
where a metal source and a nitrogen source are used as a precursor,
and a method of forming a metal contact and a capacitor of a
semiconductor device using the above method.
[0004] 2. Description of the Related Art
[0005] A barrier metal layer, which prevents mutual diffusion or
chemical reaction between different materials, is indispensable to
stabilize the contact interfaces of semiconductor devices. In
general, a metal nitride such as TiN, TaN or WN has been widely
used as the barrier metal layer of semiconductor devices. Here, TiN
is a representative example among the above metal nitrides.
[0006] However, when the metal nitride film such as TiN is
fabricated by sputtering, its application to highly integrated
semiconductor devices is not appropriate, due to low step coverage.
For an example, FIGS. 9A and 9B show the cross-section of a via
contact for connection between metal wiring. FIGS. 9A and 9B show a
simple via contact and an anchor via contact, respectively. The
formation processes thereof are as follows. A first metal layer
composed of aluminum (Al) is formed on a semiconductor substrate
20. A TiN film 40 is formed as a capping film on the resultant
structure by sputtering, and then an interlayer insulative film 50
or 51 is deposited. A contact hole is formed by etching the
interlayer insulative film 50 or 51 on the first metal layer 30. In
FIG. 9B, the step of forming an anchor A by wet etching is added.
After Ti as an adhesive layer and TiN 60 or 61 as a barrier metal
layer is deposited, a tungsten (W) plug 70 or 71 is formed to fill
the contact hole, by CVD. Thereafter, tungsten at the upper portion
is removed by chemical mechanical polishing or etch-back, and then
a second metal layer is deposited on the resultant structure,
thereby completing the connection between metal wiring. However,
this last step is not shown.
[0007] Here, in a conventional method, the TiN film 60 or 61, being
the barrier metal layer, is deposited by sputtering, with inferior
step coverage. Here, the thickness of a TiN film on the bottom,
comer and anchor A of the contact hole is reduced, with an increase
in the aspect ratio of the via. Accordingly, at a thin portion, Ti
or Al combines with fluorine remaining in tungsten source gas
WF.sub.6 during tungsten deposition being a subsequent process, and
thus an insulative film X is formed of TiF.sub.x or ALF.sub.x,
leading to a contact failure.
[0008] When the contact failure is avoided by increasing the
deposition time to increase the thickness of the TiN film 60 or 61,
the thickness of the TiN film increases only at the upper portion
of the contact hole, and the upper portion of the contact hole is
narrowed or blocked. Thus, voids are likely to be generated upon
subsequent tungsten deposition. A process with improved step
coverage is required to apply TiN to a contact with a high aspect
ratio. Accordingly, a process for fabricating a metal nitride film
using CVD (hereinafter called a CVD-metal nitride film) has been
developed as a next generation process.
[0009] A general process for forming a CVD-metal nitride film uses
a metal source containing chlorine (Cl), e.g., a precursor such as
titanium chloride TiCl.sub.4. The CVD-metal nitride film using
TiCl.sub.4 as the precursor has a high step coverage of 95% or
higher and is quickly deposited, but Cl remains in the metal
nitride film as impurities. The Cl remaining as impurities in the
metal nitride film causes corrosion of metal wiring such as Al and
increases resistivity. Thus, the Cl content in the metal nitride
film must be reduced and the resistivity must be lowered, by
deposition at high temperature. That is, in the CVD-metal nitride
film process using the metal source such as TiCl.sub.4, a
deposition temperature of at least 675.degree. C. is required to
obtain resistivity of 200 .mu..OMEGA.-cm or less. However, a
deposition temperature of 600.degree. C. or more exceeds thermal
budget and thermal stress limits which an underlayer can withstand.
In particular, when the metal nitride film is deposited on an Si
contact or a via contact with an Al underlayer, a deposition
temperature of 480.degree. C. or lower is required, so that a high
temperature CVD-metal nitride film process cannot be used.
[0010] A low temperature deposition CVD-metal nitride film process
is possible, by adding MH (methylhydrazine, (CH.sub.3)HNNH.sub.2)
to the metal source such as TiCl.sub.4, but this method has a
defect in that step coverage is decreased to 70% or lower.
[0011] Another method capable of low temperature deposition is to
form a MOCVD-metal nitride film using a metalorganic precursor such
as TDEAT (tetrakis diethylamino Ti,
Ti(N(CH.sub.2CH.sub.3).sub.2).sub.4), or TDMAT (tetrakis
dimethylamino Ti, Ti(N(CH.sub.3).sub.2).sub.4). The MOCVD-metal
nitride film has no problems due to Cl and can be deposited at low
temperature. However, the MOCVD-metal nitride film contains a lot
of carbon (C) as impurities, giving high resistivity, and has
inferior step coverage of 70% or less.
[0012] A method of forming a metal nitride film using atomic layer
epitaxy (ALE) has been tried as an alternative to deposition, in
order to overcome the problems due to Cl. However, the ALE grows
the metal nitride film in units of an atomic layer using only
chemical absorption, and the deposition speed (0.25 A/cycle or
less) is too slow to apply the ALE to mass production.
[0013] A TiN film is also used as the electrode of a semiconductor
capacitor. In particular, the TiN film is usually used in a
capacitor which uses tantalum oxide (Ta.sub.2O.sub.5) as a
dielectric film. Semiconductor capacitors, which use the TiN film
as an electrode, also have the above-described problems.
[0014] That is, in order for a semiconductor capacitor to have a
high capacitance per unit area of a semiconductor substrate, its
electrode is designed three-dimensionally, as in cylindrical
capacitors. Hence, the shape of the semiconductor capacitor is so
complicated that it is critical to guarantee step coverage of
deposited materials as its electrode. Accordingly, a TiN electrode
formed by CVD using a Cl-containing metal source having an
excellent step coverage as a precursor has been used as the
electrode of a capacitor. However, as described above, the CVDed
TiN film provokes corrosion of metal wiring and gives high
resistivity, due to a high concentration of Cl, resulting in a
degradation in the leakage current characteristics of a
capacitor.
SUMMARY OF THE INVENTION
[0015] To solve the above problems, an objective of the present
invention is to provide a method of forming a metal nitride film,
which gives excellent step coverage even at a high deposition speed
and a low temperature, low impurity concentration, and low
resistivity.
[0016] Another objective of the present invention is to provide a
method of forming a metal contact having a barrier metal layer
which has excellent step coverage even at a high deposition speed
and a low temperature, low impurity concentration, and low
resistivity, by applying the metal nitride film formation method to
a metal contact of a semiconductor device.
[0017] Still another objective of the present invention is to
provide a method of forming a capacitor which gives excellent step
coverage, low impurity concentration and low resistivity, using the
metal nitride film formation method.
[0018] Accordingly, to achieve the first objective, there is
provided a method of forming a metal nitride film using chemical
vapor deposition (CVD) in which a metal source and a nitrogen
source are used as a precursor. In this method, first, a
semiconductor substrate is introduced into a deposition chamber,
and the metal source flows into the deposition chamber. After a
predetermine time, the flow of the metal is stopped, and a purge
gas is introduced into the deposition chamber. After a
predetermined time, the purge gas is cut off and the nitrogen
source gas flows into the deposition chamber to react with the
metal source adsorbed on the semiconductor substrate. Again, after
a predetermined time, the nitrogen source gas remaining in the
deposition chamber is removed by cutting off the inflow of the
nitrogen source gas and flowing the purge gas into the deposition
chamber. Thus, the metal nitride film is formed on the
semiconductor substrate.
[0019] In the metal nitride film formation method of the present
invention, a gas inflow cycle of a sequence of the metal source,
the purge gas, the nitrogen source, and the purge gas, can be
repeated until a metal nitride film having a desired thickness is
obtained.
[0020] Here, a titanium nitride film TiN can be formed by using
TiCl.sub.4 (titanium chloride), TiCl.sub.3 (titanium chloride),
TiI.sub.4 (titanium iodide), TiBr.sub.2 (titanium bromide),
TiF.sub.4 (titanium fluoride), (C.sub.5H.sub.5).sub.2 TiCl.sub.2
(bis(cyclopentadienyl)titanium dichloride),
((CH.sub.3).sub.5C.sub.5).sub.2TiCl.sub.2
(bis(pentamethylcyclopentadienyl) titanium dichloride),
C.sub.5H.sub.5TiCl.sub.3 (cyclopentadienyltitanium trichloride),
C.sub.9H.sub.10BCl.sub.3N.sub.6Ti (hydrotris (1-pyrazolylborato)
trichloro titanium), C.sub.9H.sub.7TiCl.sub.3 (indenyltitanium
trichloride), (C.sub.5(CH.sub.3).sub.5)TiCl.sub.3
(pentamethylcyclopentad- ienyltitanium trichloride), TiCl.sub.4
(NH.sub.3).sub.2 (tetrachlorodiaminotitanium),
(CH.sub.3).sub.5C.sub.5 Ti(CH.sub.3).sub.3
(trimethylpentamethylcyclopentadienyltitanium), TDEAT or TDMAT as
the metal source, and using NH.sub.3 as the nitrogen source.
Alternatively, the tantalum nitride film TaN can be formed using a
material selected from the group consisting of TaBr.sub.5 (tantalum
bromide), TaCl.sub.5 (tantalum chloride), TaF.sub.5 (tantalum
fluoride), TaI.sub.5 (Tantalum iodide),
and(C.sub.5(CH.sub.3).sub.5)TaCl.sub.4 (pentamethylcyclopentadie-
nyltantalum tetrachloride), as the metal source, and using NH.sub.3
as the nitrogen source.
[0021] Also, it is preferable that the purge gas is an inert gas
such as Ar or N.sub.2.
[0022] Preferably, 1-5 sccm of the metal source flows into the
deposition chamber for 1 to 10 seconds, 5-200 sccm of the nitrogen
source flows thereinto for 1 to 10 seconds, and 10-200 sccm of the
purge gas flows thereinto for 1 to 10 seconds.
[0023] Also, an atmospheric gas such as Ar, He and N.sub.2 can be
continuously flowed into the deposition chamber, to maintain a
constant pressure in the deposition chamber.
[0024] Meanwhile, when the TiN film is formed using TDEAT or TDMAT
as the metal source, it is preferable to maintain the pressure in
the deposition chamber to be 0.1-10 torr and the deposition
temperature to be between 250.degree. C. and 400.degree. C. When
materials other than TDEAT and TDMAT are used as the metal source,
the pressure in the deposition chamber is maintained to be 1 to 20
torr and the deposition temperature is maintained to be between
400.degree. C. and 500.degree. C.
[0025] To achieve the second objective, there is provided a method
of forming a metal contact of a semiconductor device, wherein a
first metal layer, an interlayer insulative film, a contact hole, a
barrier metal layer, a metal plug, and a second metal layer are
sequentially formed on a semiconductor substrate. A process for
forming the barrier metal layer is as follows. A metal source flows
into the semiconductor substrate having the interlayer insulative
film in which the contact hole exposing the first metal layer is
formed. The metal source is adsorbed to the resultant structure.
After a while, the metal source remaining in the deposition chamber
is removed by cutting off the inflow of the metal source and
flowing a purge gas into the deposition chamber. After a
predetermined time, the purge gas is cut off, and a nitrogen source
flows into the deposition chamber. The nitrogen source reacts with
the metal source adsorbed on the semiconductor substrate, to thus
form a metal nitride film, being the barrier metal layer, on the
exposed first metal layer and the contact hole. Again, after a
while, the nitrogen source remaining in the deposition chamber is
removed by cutting off the inflow of the nitrogen source and
flowing the purge gas into the deposition chamber.
[0026] The barrier metal layer formation process can be repeated
until a barrier metal layer having a desired thickness is
obtained.
[0027] Here, a titanium nitride film TiN as the barrier metal layer
is formed by using a material selected from the group consisting of
TiCl.sub.4, TiCl.sub.3, TiI.sub.4, TiBr.sub.2, TiF.sub.4,
(C.sub.5H.sub.5).sub.2TiCl.sub.2,
((CH.sub.3).sub.5C.sub.5).sub.2TiCl.sub- .2, CsH.sub.5TiCl.sub.3,
C.sub.9H.sub.10BCl.sub.3N.sub.6Ti, C.sub.9H.sub.7TiCl.sub.3,
(C.sub.5(CH.sub.3).sub.5)TiCl.sub.3, TiCl.sub.4(NH.sub.3).sub.2,
(CH.sub.3).sub.5C.sub.5Ti(CH.sub.3).sub.3, TDEAT and TDMAT as the
metal source, and using NH.sub.3 as the nitrogen source.
Alternatively, the tantalum nitride film TaN as the barrier metal
layer is formed using a material selected from the group consisting
of TaBr.sub.5, TaCl.sub.5, TaF.sub.5, TaI.sub.5, and
(C.sub.5(CH.sub.3).sub.- 5)TaCl.sub.4 as the metal source, and NH3
as the nitrogen source.
[0028] Also, it is preferable that the purge gas is an inert gas
such as Ar or N.sub.2.
[0029] The flow amounts and flow times of the metal source,
nitrogen source, and purge gas flowing into a deposition chamber
are within the same ranges as in the above-mentioned method of
forming the metal nitride film.
[0030] Also, in order to maintain a constant pressure within the
deposition chamber while forming a barrier metal layer, the
pressure within the deposition chamber is kept at about 0.1 to 10
torr when TDEAT or TDMAT is used as the metal source, and about 1
to 20 torr when materials other than TDEAT and TDMAT are used as
the metal source. The constant pressure is maintained using an
atmospheric gas such as Ar, He, or N.sub.2.
[0031] It is preferable that a deposition temperature upon the
formation of the barrier metal layer is about between 250.degree.
C. and 400.degree. C. when TDEAT or TDMAT is used as the metal
source, and between 400.degree. C. and 500.degree. C. when
materials other than TDEAT and TDMAT are used as the metal
source.
[0032] To achieve the third objective, there is provided a method
of forming a semiconductor capacitor, wherein a lower conductive
layer, a dielectric film and an upper conductive layer are
sequentially formed on the underlayer of a semiconductor substrate.
In a process for forming the lower and/or upper conductive layer, a
semiconductor substrate on which an underlayer or a dielectric film
is formed is introduced into a deposition chamber, and a metal
source flows into the deposition chamber. The metal source is
chemically and physically adsorbed onto the substrate. After a
predetermined period of time, the metal source is purged from the
deposition chamber. After a predetermined period of time, a
nitrogen source flows into the deposition chamber, and is
chemically and physically adsorbed onto the substrate. The adsorbed
metal source and nitrogen source are reacted to form a metal
nitride film on the substrate. After another predetermined period
of time, the nitrogen source is purged from the deposition
chamber.
[0033] The step of forming a metal nitride film can be repeated
until a lower and/or upper conductive layer having a desired
thickness is obtained.
[0034] Here, when Ti is used, the metal source used to form the
lower and/or upper conductive layer is selected from the group
consisting of TiCl.sub.4, TiCl.sub.3, TiI.sub.4, TiBr.sub.2,
TiF.sub.4, (C.sub.5H.sub.5).sub.2TiCl.sub.2,
((CH.sub.3).sub.5C.sub.5).sub.2TiCI.sub- .2,
C.sub.5H.sub.5TiCl.sub.3, C.sub.9H.sub.10BCl.sub.3N.sub.6Ti,
C.sub.9H.sub.7TiCl.sub.3, (C.sub.5(CH.sub.3).sub.5)TiCl.sub.3,
TiCl.sub.4(NH.sub.3).sub.2,
(CH.sub.3).sub.5C.sub.5Ti(CH.sub.3).sub.3, TDEAT and TDMAT. When Ta
is used, the metal source is selected from the group consisting of
TaBr.sub.5, TaCl.sub.5, TaF.sub.5, Tal.sub.5, and
(C.sub.5(CH.sub.3).sub.5)TaCl.sub.4. The nitrogen source is
NH.sub.3.
[0035] Also, it is preferable that the purge gas is an inert gas
such as Ar or N.sub.2.
[0036] The flow amounts and inflow times of a metal source, a
nitrogen source and a purge gas flowing into the deposition chamber
are within the same ranges as those in the metal nitride film
formation method according to the present invention.
[0037] Also, in order to maintain a constant pressure within the
deposition chamber while forming a lower and/or upper conductive
layer, the pressure within the deposition chamber is maintained to
be about 0.1-10 torr when TDEAT or TDMAT is used as a metal source,
and the pressure within the deposition chamber is maintained to be
about 1-20 torr when materials other than TDEAT and TDMAT are used
as the metal source. The constant pressure is maintained by the use
of an atmospheric gas such as Ar, He or N.sub.2.
[0038] Preferably, when TDEAT or TDMAT is used as the metal source,
the deposition temperature in each of the steps for forming a lower
conductive layer and/or an upper conductive layer is between
250.degree. C. and 500.degree. C. Also, preferably, when other
materials are used as the metal source, the deposition temperature
in each of the steps for forming a lower conductive layer and/or an
upper conductive layer is between 400.degree. C. and 500.degree.
C.
[0039] According to the present invention, a metal nitride film
having low resistivity of 200.mu..OMEGA.-cm or less and a low
content of Cl can be obtained even with excellent step coverage.
Also, a CVD-metal nitride film can be formed at a temperature of
500.degree. C. or less even at a deposition speed of about 20
A/cycle, so that the deposition speed of the present invention is
higher than that of a metal nitride film formation method using ALE
having a growth speed of 0.25 A/cycle. A capacitor, in which a
metal nitride film formed by the method according to the present
invention is used as a lower and/or upper conductive layer, has
excellent step coverage and excellent leakage current
characteristics.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] The above objectives and advantages of the present invention
will become more apparent by describing in detail a preferred
embodiment thereof with reference to the attached drawings in
which:
[0041] FIG. 1 shows a deposition chamber of a chemical vapor
deposition (CVD) apparatus for depositing a metal nitride film on a
semiconductor substrate, according to the present invention;
[0042] FIG. 2 shows gas inflow timings for depositing a metal
nitride film on a semiconductor substrate, according to the present
invention;
[0043] FIG. 3 is a graph of the results of Rutherford back
scattering (RBS) of a metal nitride film deposited according to the
present invention;
[0044] FIG. 4 is a graph illustrating the resistivity and
deposition speed of a metal nitride film with respect to flow
amount of NH3, when the metal nitride film is deposited according
to the present invention;
[0045] FIG. 5 is a graph illustrating the resistivity and
deposition speed of a metal nitride film with respect to pressure
in a deposition chamber, when the metal nitride film is deposited
according to the present invention;
[0046] FIG. 6 is a graph illustrating the deposited thickness of a
metal nitride film versus the number of cycles when the metal
nitride film is deposited according to the present invention;
[0047] FIG. 7 is a graph illustrating the deposition speed of a
metal nitride film versus the number of cycles when the metal
nitride film is deposited according to the present invention;
[0048] FIG. 8 is a graph illustrating the resistivity of a metal
nitride film versus deposition temperature when the metal nitride
film is deposited according to the present invention;
[0049] FIGS. 9A and 9B are cross-sections of a via contact formed
by a conventional method;
[0050] FIGS. 10A through 10F are cross-sectional views illustrating
an example of a process for forming a via contact using the metal
nitride film formation method of the present invention;
[0051] FIGS. 11A through 11F are cross-sectional views illustrating
another example of a process for forming a via contact using the
metal nitride film formation method of the present invention;
[0052] FIG. 12 is a graph illustrating the relationship between via
resistivity and via width when a barrier metal layer is formed
according to the present invention and the prior art;
[0053] FIG. 13 is a graph illustrating via resistivity
distributions when barrier metal layers are formed according to the
present invention and the prior art;
[0054] FIGS. 14A through 14D are cross-sectional views illustrating
a process for forming a semiconductor capacitor using a metal
nitride film formation method according to the present
invention;
[0055] FIGS. 15A and 15B are graphs showing the X-ray phonon
spectroscopy (XPS) results of metal nitride films formed by a
conventional method and a method according to the present
invention, respectively; and
[0056] FIG. 16 is a graph showing the leakage current
characteristics of capacitors formed by a conventional method and a
method according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0057] Referring to FIG. 1, a plurality of gas lines 114a and 114b
for introducing reaction gases into a deposition chamber 100 are
installed into the deposition chamber 100. Here, the number of gas
lines depends on the number of metal sources and nitrogen sources,
i.e., the number of reaction gases, flowed into the deposition
chamber 100. In an embodiment of the present invention, two gas
lines 114a and 114b are installed.
[0058] The two gas lines 114a and 114b have one end connected to a
supply source (not shown) for a metal source and to a supply source
(not shown) for a nitrogen source, respectively. When a TiN film is
deposited on a semiconductor substrate 104, TiCl.sub.4 is used as
the metal source and NH.sub.3 is used as the nitrogen source.
Meanwhile, the other ends of the gas lines 114a and 114b are
connected to a shower head 110 isolated by a predetermined distance
(D of FIG. 1) from the semiconductor substrate 104 seated in the
deposition chamber 100. Accordingly, the reaction gases from the
gas supply sources (not shown) enter the deposition chamber 100 via
the gas lines 114a and 11 4b and the shower head 110 connected to
the ends of the gas lines 114a and 114b. The reaction gases react
with each other in the deposition chamber, and the resultant forms
a film on the semiconductor substrate 104.
[0059] It is preferable that the shower head 110 is a multi-port
shower head which allows the reaction gases to enter the deposition
chamber 100 in an unmixed state. In this embodiment, a two-port
shower head is used. Also, it is preferable that the gas lines 114a
and 114b are provided with purge gas supply lines 114c and 114d to
supply to the deposition chamber 100 a purge gas for exhausting
residual gases after reaction. Valves 112 are installed on the
respective gas supply lines. According to the on/off state of the
valves 112, the purge gases or reaction gases may enter into the
deposition chamber 100 or be cut off. It is preferable that the
valves 112, such as pneumatic valves, are controlled by a
programmed control unit to be periodically turned on or off.
Reference numeral 102 is a heater for heating the semiconductor
substrate 104.
[0060] A method of depositing a metal nitride such as TiN on a
semiconductor substrate seated in the deposition chamber of a CVD
apparatus having such a configuration, according to the present
invention, will now be described in detail referring to FIGS. 1 and
2.
[0061] First, the semiconductor substrate 104 is introduced into
the deposition chamber 100. The semiconductor substrate 104 may
have devices such as transistors formed on its surface (see FIG.
1).
[0062] A metal source such as TiCl.sub.4 flows into the deposition
chamber 100 for the time of tS via the metal source supply line
114a. Alternatively, the metal source can be mixed with a carrier
gas such as Ar or N.sub.2 to provide a smooth gas flow into the
deposition chamber 100. At this time, valves other than the valve
of the gas supply line 114a for supplying a metal source are in off
state. Accordingly, only the metal source such as TiCl.sub.4 flows
into the deposition chamber 100. At this time, a part of the
entering metal source is chemically and physically adsorbed on the
surface of the substrate 104, and the residual remains in the
deposition chamber 100. As described above, only one type of gas
enters the deposition chamber 100 for a predetermined time, instead
of simultaneously flowing reaction gases into the deposition
chamber 100. This is called gas pulsing (see FIG. 2).
[0063] When inflow of the metal source into the deposition chamber
100 is completed, the valve of the gas supply line 114a for
introducing the metal source is closed, and then the valve of the
purge gas supply line 114c is opened to introduce the purge gas
such as Ar or N.sub.2 into the deposition chamber 100 for the time
of tp, thereby exhausting TiCl.sub.4 gases from the shower head 110
and the deposition chamber 100 (in the purge gas pulsing step of
FIG. 2). At this time, the flow of the purge gas and the pressure
of the deposition chamber are appropriately controlled to prevent
the metal source chemically and physically adsorbed into the
semiconductor substrate from being separated and exhausted, thereby
exhausting only the source gas remaining within the deposition
chamber.
[0064] Then, the valve of the purge gas supply line 114c is closed,
and the valve of the nitrogen gas source supply line 114b is opened
to introduce a nitrogen gas such as NH3 into the deposition chamber
100 for a time tr. The nitrogen gas reacts with the metal source
such as TiCl.sub.4 chemically and physically adsorbed into the
substrate 104, thus forming the metal nitride such as TiN on the
semiconductor substrate 104. That is, because of the purge gas
pulsing step before the nitrogen source such as NH.sub.3 enters
into the deposition chamber 100, the metal source such as
TiCl.sub.4 remaining in the deposition chamber 100 is exhausted via
the pump (see FIG. 1). Accordingly, the nitrogen source such as
NH.sub.3 does not react with the metal source such as TiCl.sub.4
within the deposition chamber 100, except for on the semiconductor
substrate 104. Thus, the metal nitride is formed on only the
semiconductor substrate 104 into which TiCl.sub.4 and NH.sub.3 are
adsorbed (in the NH3 pulsing step of FIG. 2).
[0065] At this time, the carrier gas such as Ar or N.sub.2 can be
mixed with the nitrogen gas such as NH3 for a smooth gas flow into
the deposition chamber 100.
[0066] In a conventional method of forming a metal nitride film
using ALE, only the chemically-adsorbed source remains, after
purging the source physically adsorbed on the substrate. On the
other hand, in the metal nitride film formation method of the
present invention, the sources both physically and chemically
adsorbed on the substrate remain and react. This is the fundamental
difference between the prior art and the present invention.
[0067] Next, the residual nitrogen source remaining within the
deposition chamber 100 after the reaction with the metal source is
exhausted by another purge gas pulsing step (in the purge gas
pulsing step of FIG. 2).
[0068] Meanwhile, while the pressure in the deposition chamber 100
is controlled during the above-described steps, it is preferable
that an atmospheric gas such as Ar or N.sub.2 is continuously
supplied into the deposition chamber 100.
[0069] As described above, in the method of forming a metal nitride
film using gas pulsing, according to the present invention, the
metal nitride film such as TiN having a predetermined thickness is
deposited through a cycle having a sequence of the TiCl.sub.4
pulsing step, the purge gas pulsing step, the NH.sub.3 pulsing
step, and the purge gas pulsing step. Here, a deposition speed is
about 20 A/cycle, and when this cycle is repeated, the thickness of
a thin film is proportionally increased, so that a thin film having
a desired thickness can be deposited on the semiconductor substrate
100. Here, the thickness of the metal nitride film deposited for
one cycle is determined by the flow amounts of the metal source and
nitrogen source entering the deposition chamber 100, the gas
pulsing times, the flow amount of the purge gas, and the purge
time.
[0070] Hereinafter, experimental examples of forming a TiN film
according to the present invention will be described.
[0071] <First Experimental Example>
[0072] A TiN film is deposited by the cycles comprising the gas
pulsing steps, under the following reaction conditions, on the
semiconductor substrate 104 which is maintained at a temperature of
500.degree. C. or lower by the heater 102 of FIG. 1.
[0073] Deposition Conditions
[0074] object material: TiN
[0075] atmospheric gas: Ar
[0076] pressure in deposition chamber: 1-20Torr
[0077] metal source, nitrogen source: TiCl.sub.4, NH.sub.3
[0078] flow amount of TiCl.sub.4, pulsing time (t.sub.s) of
TiCl.sub.4:1-5 sccm, 5 sec
[0079] flow amount of NH.sub.3, pulsing time (t.sub.r) of NH.sub.3:
5-30 sccm, 5 sec
[0080] purge gas, flow amount of purge gas, purge time (t.sub.p):
Ar, 10-100 sccm, 10 sec
[0081] carrier gas, flow amount of carrier gas: Ar, 10-100 sccm
[0082] time (t.sub.t) for one cycle: 30 sec
[0083] FIG. 3 shows the results of checking the state of the TiN
thin film deposited on the semiconductor substrate 104 under the
aforementioned conditions using an RBS method. In FIG. 3, a
horizontal axis indicates channels in a multi-channel analyzer
(MCA), and a vertical axis indicates the standardized yields of
elements detected by the MCA. Here, the relationship between each
channel and energy is given by equation, E[eV]=4.05'
channel+59.4.
[0084] The TiN film deposited on the semiconductor substrate 104
under the aforementioned conditions has a unique gold color, and
has a perfect composition of Ti:N=1:1 as shown in FIG. 3. Cl is
0.3% or less of the total elements contained in the TiN thin film,
which is the detection limit by RBS, as shown in FIG. 3. Also, the
resistivity of the TiN film deposited on the semiconductor
substrate 104 under the above conditions was measured as a low
value of about 130 .mu..OMEGA.-cm. Meanwhile, according to several
experiments, it was verified that the thickness of the TiN thin
film deposited for each cycle must be 20 A or less to provide such
an excellent thin film property.
[0085] FIGS. 4 and 5 show the resistivity and deposition speed of
the TiN film deposited according to the present invention, at
various flow amounts of the nitrogen source NH.sub.3 and pressures
in the deposition chamber, respectively. As shown in FIGS. 4 and 5,
the deposition speed increases with an increase in the flow amount
of NH.sub.3 and the pressure in the deposition chamber, and thus
the resistivity also increases. Accordingly, it is preferable that
the conditions for deposition are set in consideration of the
thickness and the deposition speed and resistivity of the metal
nitride film required according to places to apply the metal
nitride film.
[0086] <Second Experimental Example>
[0087] A deposition speed for each cycle, the thickness and
deposition speed of a TiN film deposited according to an increase
in the number of cycles, and resistivity according to a change in
deposition temperature, are measured under four deposition
conditions as shown in the following Table 1. Here, the metal
source is TiCl.sub.4, the nitrogen source is NH.sub.3, and the
purge gas is Ar.
1TABLE 1 amount amount amount and amount amount of deposition and
time and time time of and time atmospheric conditions of metal
source of purge gas nitrogen source of purge gas pressure gas TiN
00 5 sccm, 40 sccm, 150 sccm, 40 sccm, 3 torr 50 sccm 5 sec 5 sec 5
sec 5 sec TiN 01 3 sccm, 150 sccm, 30 sccm, 150 sccm, 2 torr 30
sccm 3 sec 3 sec 3 sec 3 sec TiN 02 3 sccm, 150 sccm, 50 sccm, 150
sccm, 3 torr 30 sccm 2 sec 2 sec 2 sec 2 sec TiN 03 3 sccm, 150
sccm, 100 sccm, 150 sccm, 3 torr 30 sccm 2 sec 2 sec 2 sec 2
sec
[0088] Deposition speeds per cycle under the above deposition
conditions are as follows:
[0089] TiN 00:20 A/cycle (60 A/min, since one cycle is 20
seconds)
[0090] TiN 01:2 A/cycle (10 A/min, since one cycle is 12
seconds)
[0091] TiN 02:3.5 A/cycle (26.3 A/min, since one cycle is 8
seconds)
[0092] TiN 03:6 A/cycle (45 A/min, since one cycle is 8
seconds).
[0093] FIGS. 6 and 7 show the deposition thickness and deposition
speed, respectively, according to an increase in the number of
cycles. Here, a deposition temperature is 500.degree. C. As can be
seen from FIGS. 6 and 7, the deposition speed increases slowly with
an increase in the number of cycles, and the deposition thickness
increases in proportion to the number of cycles. Thus, the
thickness of the TiN film to be deposited can be controlled by
adjusting the number of cycles under consistent deposition
conditions.
[0094] FIG. 8 is a graph showing resistivity of the TiN film with
respect to deposition temperature according to the four deposition
conditions described above. It can be seen from FIG. 8 that the
resistivity decreases with an increase in the deposition
temperature. Particularly, it can be seen that the resistivity
sharply decreases under the deposition condition (TiN 00) in which
the deposition speed is high. Also, we can recognize that
resistivity of 200.mu..OMEGA.-cm or less is obtained at about
500.degree. C. under all the four deposition conditions.
[0095] An example of applying the metal nitride film formation
method of the present invention to a via contact will now be
described in detail, referring to FIGS. 10A through 11F.
[0096] First, a first metal layer 210 such as Al is formed on a
semiconductor substrate 200, and a TiN film 220 is deposited as a
capping film on the resultant structure, as shown in FIG. 10A. The
TiN film 220 can be deposited by sputtering. Then, an interlayer
insulative film 230 is deposited, and a portion on which a via is
to be formed is etched, thereby forming the structure of FIG. 10B.
A thin Ti film (not shown) is formed on the resultant structure to
improve attachment strength of the TiN film, before the TiN film,
being a barrier metal layer, is deposited. This Ti film can also be
formed by sputtering.
[0097] Next, the TiN film 240, being a barrier metal layer, is
deposited by the metal nitride film formation method of the present
invention, thus forming the structure of FIG. 10C. That is, as
described above, a metal source, a purge gas, and a nitrogen source
flow into the deposition apparatus of FIG. 1 in the sequence of the
metal source, the purge gas, the nitrogen source, and the purge
gas. This is repeated until a desired thickness is obtained. Here,
the metal source is TiCl.sub.4 and the nitrogen source is NH.sub.3.
The amounts of the metal source, the nitrogen source and the purge
gas are 1 to 5 sccm, 5 to 200 sccm, and 10 to 200 sccm,
respectively, and the inflow times thereof are about 1 to 10
seconds. A deposition temperature is 480.degree. C. or lower, and
the pressure in the deposition chamber is between 1 torr and 20
torr. If necessary, an atmospheric gas such as Ar, He, or N.sub.2,
and a carrier gas of Ar, N.sub.2, etc., can be used. These
deposition conditions are appropriately controlled considering the
deposition apparatus, the deposition speed, the thickness of the
TiN film deposited, and the resistivity of the TiN film.
[0098] A metal plug 250 such as W is formed by a typical method, in
FIG. 10D, and a metal deposited on the upper surface of an
interlayer insulative film 230 is removed by chemical mechanical
polishing or etch back, in FIG. 10E. Then, when a second metal
layer 260 is formed on the resultant structure as shown in FIG.
10F, interconnection between metal layers is accomplished.
[0099] FIGS. 11A through 11F are cross-sectional views illustrating
a process for forming an anchor via contact, which is fundamentally
the same as the process of FIGS. 10A through 10F except that an
anchor A is formed on the lower portion of a contact hole to lower
resistance by increasing a contact area as shown in FIG. 11B. The
anchor A is formed by wet etching the interlayer insulative film
335 after forming the contact hole as shown in FIG. 11A. The other
steps are the same as those of FIGS. 10A through 10F, so they will
not be described again.
[0100] As described above, when the metal nitride film formation
method of the present invention is applied to the via contact, a
barrier metal layer having an excellent step coverage can be
obtained at low temperature. Thus, a contact failure X such as TiFx
or AlFx shown in FIGS. 9A and 9B can be prevented.
[0101] <Third Experimental Example>
[0102] A Ti film is deposited to a thickness of 100A on contact
holes of various different widths, by sputtering. Then, as a
barrier metal layer, a TiN film according to the present invention,
and a collimated TiN film formed by sputtering by a conventional
method, are deposited to different thicknesses, and a plug is
formed of CVD-W. The third experiment measures via resistance in
this case. Here, the deposition conditions of the TiN film
according to the present invention are equal to the deposition
conditions of TiN 00 of the aforementioned second experiment, with
a deposition temperature of 450.degree. C.
[0103] Via widths: 0.24 .mu.m, 0.32 .mu.m, 0.39 .mu.m (via depth:
0.9 .mu.m) Thickness of TiN film: 100 A, 200 A, 400 A, 600 A (these
are deposited by the method of the present invention), 700 A
(collimated TiN film)
[0104] As the results of measurement, resistivity generally
decreases with an increase in via width as shown in FIG. 12, and
resistivity decreases with decreasing the thickness of the TiN film
of the present invention. The 100 A-thick TiN film according to the
present invention has a similar resistance to the collimated TiN
film. In particular, when the via width is 0.39 .mu.m, the above
five TiN films have similar via resistances. Meanwhile, in the
second experiment and as shown in FIG. 8, the TiN films of the
present invention were formed at a high deposition speed per cycle
(20 A/cycle) and with large resistivity (300 .mu..OMEGA.-cm at
450.degree. C.). Accordingly, if the TiN films of the present
invention are formed at a lower deposition speed and with smaller
resistivity, their via resistances can be significantly
improved.
[0105] FIG. 13 is a graph showing the distribution of the via
resistance of each TiN film when the via width is 0.39 .mu.m. From
the graph of FIG. 13, we can recognize that the collimated TiN film
and the TiN films according to the present invention are evenly
distributed, without a big difference, around 1.0 .OMEGA..
[0106] Up to now, the present invention has been described by
taking as an example the method wherein the TiN film is formed as a
metal nitride film by using TiCl.sub.4 and NH.sub.3 as a precursor.
However, the present invention can be applied to a TiN film using
TiCl.sub.3, TiI.sub.4, TiBr.sub.2, TiF.sub.4,
(C.sub.5H.sub.5).sub.2TiCl.sub.2,
((CH.sub.3).sub.5C.sub.5).sub.2TiCl.sub.2,
C.sub.5H.sub.5TiCl.sub.3, C.sub.9H.sub.10BCl.sub.3N.sub.6Ti,
C.sub.9H.sub.7TiCl.sub.3, (C.sub.5(CH.sub.3).sub.5)TiCl.sub.3,
TiCl.sub.4(NH.sub.3).sub.2,
(CH.sub.3).sub.5C.sub.5Ti(CH.sub.3).sub.3, TDEAT or TDMAT instead
of TiCl.sub.4 as the precursor, and also to other metal nitride
films such as TaN firm using TaBr.sub.5, TaCl.sub.5, TaF.sub.5,
TaI5, or (C.sub.5(CH.sub.3).sub.5)TaCl.sub.4 as precursors, and
further to almost any material layers deposited using CVD.
[0107] However, when the TiN film is formed using TDEAT or TDMAT as
the precursor, it is preferable that a deposition temperature is
between 250.degree. C. and 400.degree. C. and a pressure is about
0.1 to 10 torr, in contrast with the cases using the other
materials as the precursor. Since the above precursors for forming
the TaN film are all solid, a solid bubbler must be used to form a
source gas.
[0108] An example of forming a semiconductor capacitor by applying
the metal nitride formation method according to the present
invention to a capacitor electrode will now be described in detail
with reference to FIGS. 14 through 16.
[0109] A semiconductor capacitor is formed by sequentially stacking
a lower conductive layer, a dielectric film and an upper conductive
layer. The process for forming a lower and/or upper conductive
layer to form a semiconductor capacitor according to the present
invention adopts the metal nitride film formation method according
to the present invention described above. That is, as described
above, a metal source, a purge gas, and a nitrogen source flow into
the deposition apparatus of FIG. 1 in the sequence of the metal
source, the purge gas, the nitrogen source, and the purge gas. This
is repeated until a desired thickness is obtained. Here, the metal
source is TiCl.sub.4 and the nitrogen source is NH.sub.3. The
amounts of the metal source, the nitrogen source and the purge gas
are 1 to 5 sccm, 5 to 200 sccm, and 10 to 200 sccm, respectively,
and the inflow times thereof are about 1 to 10 seconds. A
deposition temperature is 480.degree. C. or lower, and the pressure
in the deposition chamber is between 1 torr and 20 torr. If
necessary, an atmospheric gas such as Ar, He, or N.sub.2, and a
carrier gas of Ar, N.sub.2, etc., can be used. These deposition
conditions are appropriately controlled considering the deposition
apparatus, the deposition speed, the thickness of the TiN film
deposited, and the resistivity of the TiN film.
[0110] Up to now, the present invention has been described by
taking as an example the method wherein the TiN film is formed as a
metal nitride film by using TiCl.sub.4 and NH.sub.3 as a precursor.
However, TiCl.sub.3, TiI.sub.4, TiBr.sub.2, TiF.sub.4,
(C.sub.5H.sub.5).sub.2TiCl.sub.2,
((CH.sub.3).sub.5C.sub.5).sub.2TiCl.sub.2,
C.sub.5H.sub.5TiCl.sub.3, C.sub.9H.sub.10BCl.sub.3N.sub.6Ti,
C.sub.9H.sub.7TiCl.sub.3, (C.sub.5(CH.sub.3).sub.5)TiCl.sub.3,
TiCl.sub.4(NH.sub.3).sub.2,
(CH.sub.3).sub.5C.sub.5Ti(CH.sub.3).sub.3, TDEAT or TDMAT can be
used as the precursor. In case that a TaN film is formed as a metal
nitride film, TaBr.sub.5, TaCl.sub.5, TaF.sub.5, TaI.sub.5, or
(C.sub.5(CH.sub.3).sub.5- )TaCl.sub.4 can be used as
precursors.
[0111] When the TiN film is formed using TDEAT or TDMAT as the
precursor, it is preferable that a deposition temperature is
between 250.degree. C. and 400.degree. C. and a pressure is about
0.1 to 10 torr. Since the above precursors for forming the TaN film
are all solid, a solid bubbler must be used to form a source
gas.
[0112] <Fourth Experimental Example>
[0113] FIGS. 14A through 14D are cross-sectional views illustrating
a process for forming a semiconductor capacitor having a
cylindrical electrode structure for measuring step coverage and
leakage current characteristics. Referring to FIG. 14A, an
SiO.sub.2 sacrificial oxide film 440 is formed on a semiconductor
substrate 400 on which a predetermined contact 420 and an etch stop
film 430 are formed. The contact 420 electrically connects the
active region of the semiconductor substrate to the electrode of a
capacitor via the interlayer dielectric film 410.
[0114] Referring to FIG. 14B, cylindrical holes 447 are formed by
dry etching the sacrificial oxide film 440, and then a lower
conductive layer 450 is formed by chemical vapor depositing
polysilicon. Continuously, as shown in FIG. 14C, a lower electrode
455 is formed by node separating the lower conductive layer 450,
and then the sacrificial oxide film 440 of FIG. 14B remaining
between the lower electrodes 455 is removed. Next, as shown in FIG.
14D, a dielectric film 460 is formed by chemical vapor depositing
Ta.sub.2O.sub.5 on the semiconductor substrate on which the lower
electrode has been formed, and an upper conductive layer is formed
on the dielectric film at about 480.degree. C. using TiCl.sub.4
nitrogen precursor and an NH.sub.3 nitrogen source by the metal
nitride film formation method according to the present invention.
Thereafter, a polysilicon film is formed on the upper conductive
layer, thereby forming the structure of a capacitor according to
the present invention. A conventional capacitor is formed by the
same method as the above-described method by which the capacitor
according to the present invention is formed, except that an upper
conductive layer is formed by chemical vapor depositing a TiN film
at about 620.degree. C. using TiCl.sub.4 and NH.sub.3 as a source
gas. Here, 10 sccm of TiCl.sub.4 and 50 sccm of NH.sub.3 are used
when TiN is chemical vapor deposited.
[0115] As to the capacitor formed by a method according to the
present invention (expressed as SLD-TiN) and the capacitor having a
chemically vapor deposited (CVDed) TiN upper conductive layer
(expressed as CVD-TiN), the step coverage of an upper conductive
layer and the leakage current characteristics are measured and
shown in Table 2 and FIG. 16, respectively.
2TABLE 2 Classification Lower thickness Upper thickness Step
coverage CVD-TiN 35A 156A 22.6% SLD-TiN 188A 208A 90.1%
[0116] In Table 2, the upper and lower thicknesses denote the
thicknesses of an upper conductive layer at portions pointed by
reference characters t.sub.1 and t.sub.2 shown in FIG. 14D,
respectively. As can be seen from Table 2, the step coverage of the
capacitor according to the present invention is significantly
higher than that of the capacitor having a CVD'ed TiN upper
conductive layer. The CVD technique can also improve step coverage
by increasing the flow ratio of TiCl.sub.4/H.sub.3, but has a
drawback in that the leakage current characteristics is degraded
due to an increase in the concentration of Cl remaining within a
film.
[0117] In FIG. 16, the leakage current value of the capacitor
according to the present invention (SLD-TiN) is lower than that of
the capacitor having a CVDed upper conductive layer (CVD-TiN) in
most of an applied voltage section. In particular, around .+-.1.2
V, which is the basis of the leakage current characteristics of a
capacitor, the leakage current value of the capacitor according to
the present invention is only about 1/3 or {fraction (1/15)} times
that of the capacitor having a CVDed upper conductive layer.
[0118] FIGS. 15A and 15B show the content of Cl contained in a
conductive layer formed by a method according to the present
invention and the content of Cl contained in a CVDed conductive
layer, respectively. The measurement of the Cl content is achieved
by performing XPS with respect to a TiN film formed by the metal
nitride film formation method according to the present invention
and a CVDed TiN film which are separately formed on SiO.sub.2
substrates. In the graphs of FIGS. 15A and 15B, the left portion
corresponds to a TiN film region, and the right portion, where
etching is further progressed, corresponds to an SiO.sub.2
substrate region. As shown in FIGS. 15A and 15B, the Cl content of
the TiN film formed by a method according to the present invention
is a maximum of 0.4 atomic % in the TiN film region, but the Cl
content of the TiN film formed by CVD is a maximum of 3.9 atomic %
in the TiN film region. Preferably, the Cl content in a general
capacitor is maintained below 1%. Thus, it can be seen that the TiN
film formed by a method according to the present invention has a Cl
content that is suitable for the conductive layer of a
semiconductor capacitor.
[0119] According to the metal nitride film fonnation method of the
present invention as described above, a metal nitride film has low
resistivity of 200 .mu..OMEGA.-cm or less even with excellent step
coverage and contains only a small amount of Cl. Also, the metal
nitride film can be formed at a temperature of 500.degree. C. or
lower, and also a deposition speed, approximately 20 A/cycle, is
considerably higher than that in the metal nitride film formation
method using ALE with a growth speed of 0.25 A/cycle.
[0120] Accordingly, as opposed to when a metal nitride film is
deposited at a temperature of 650.degree. C. or higher in a
conventional method, corrosion of metal wiring and high resistivity
due to impurities (Cl) remaining in the metal nitride film can be
solved, so that the present invention is applicable to a via
contact which has a high aspect ratio and requires a low
temperature. Also, since the present invention has a higher
deposition speed than the metal nitride film formation method using
ALE, it is suitable for mass production.
[0121] Also, the metal nitride film formation method according to
the present invention can be used to form the electrode of a
semiconductor capacitor having a three-dimensional electrode
structure, leading to the formation of a semiconductor capacitor
having a very low content of Cl and excellent leakage current
characteristics.
* * * * *