U.S. patent application number 09/826946 was filed with the patent office on 2001-10-25 for method of manufacturing a barrier metal layer using atomic layer deposition.
Invention is credited to Choi, Gil-Heyun, Jeon, In-Sang, Kang, Sang-Bom, Lim, Hyun-Seok.
Application Number | 20010034123 09/826946 |
Document ID | / |
Family ID | 19665863 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010034123 |
Kind Code |
A1 |
Jeon, In-Sang ; et
al. |
October 25, 2001 |
Method of manufacturing a barrier metal layer using atomic layer
deposition
Abstract
A method of manufacturing a barrier metal layer uses atomic
layer deposition (ALD) as the mechanism for depositing the barrier
metal. The method includes supplying a first source gas onto the
entire surface of a semiconductor substrate in the form of a pulse,
and supplying a second source gas, which reacts with the first
source gas, onto the entire surface of the semiconductor substrate
in the form of a pulse. In a first embodiment, the pulses overlap
in time so that the second source gas reacts with part of the first
source gas physically adsorbed at the surface of the semiconductor
substrate to thereby form part of the barrier metal layer by
chemical vapor deposition whereas another part of the second source
gas reacts with the first source gas chemically adsorbed at the
surface of the semiconductor substrate to thereby form part of the
barrier metal layer by atomic layer deposition. Thus, the
deposition rate is greater than if the barrier metal layer were
only formed by ALD. In the second embodiment, an impurity-removing
gas is used to remove impurities in the barrier metal layer. Thus,
even if the gas supply scheme is set up to only use ALD in creating
the barrier metal layer, the deposition rate can be increased
without the usual accompanying increase in the impurity content of
the barrier metal layer.
Inventors: |
Jeon, In-Sang; (Suwon-city,
KR) ; Kang, Sang-Bom; (Seoul, KR) ; Lim,
Hyun-Seok; (Yongin-city, KR) ; Choi, Gil-Heyun;
(Sungnam-city, KR) |
Correspondence
Address: |
JONES VOLENTINE, L.L.C.
12200 Sunrise Valley Drive, Suite 150
Reston
VA
20191
US
|
Family ID: |
19665863 |
Appl. No.: |
09/826946 |
Filed: |
April 6, 2001 |
Current U.S.
Class: |
438/643 ;
257/E21.17; 257/E21.171; 257/E21.584 |
Current CPC
Class: |
H01L 21/7685 20130101;
H01L 21/28562 20130101; C23C 16/45531 20130101; H01L 21/76843
20130101; C23C 16/45527 20130101; H01L 21/28556 20130101 |
Class at
Publication: |
438/643 |
International
Class: |
H01L 021/4763 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 20, 2000 |
KR |
2000-20996 |
Claims
What is claimed is:
1. A method of manufacturing a barrier metal layer, comprising the
steps of: loading a semiconductor substrate into a processing
chamber; supplying a first source gas, containing a metal, onto the
entire surface of the semiconductor substrate in the form of a
pulse having a duration lasting from a point in time A.sub.1 to a
point in time A.sub.2, whereby the first source gas is chemically
and physically adsorbed at the surface; and supplying a second
source gas, that is reactive with the first source gas to form the
barrier metal, onto the entire surface of the semiconductor
substrate in the form of a pulse having a duration lasting from a
point in time A.sub.3 to a point in time A.sub.4, wherein said
point in time A.sub.3 is no earlier than said point in time A.sub.1
and no later than said point in time A.sub.2, whereby one portion
of the second source gas reacts with that part of the first source
gas physically adsorbed at the surface of the semiconductor
substrate to thereby form the barrier metal layer by chemical vapor
deposition whereas another part of the second source gas reacts
with that part of the first source gas chemically adsorbed at the
surface of the semiconductor substrate to thereby form the barrier
metal layer by atomic layer deposition.
2. The method of claim 1, wherein said point in time A.sub.4 is no
later in time than said point in time A.sub.2.
3. The method of claim 1, and further comprising supplying a purge
gas onto the entire surface of the semiconductor substrate
beginning at a point in time that is no later than said point in
time A.sub.1.
4. The method of claim 1, and further comprising supplying a purge
gas onto the entire surface of the semiconductor substrate
beginning at a point in time that is later than said point in time
A.sub.1 and no later than said point in time A.sub.3.
5. The method of claim 1, wherein the first source gas includes an
element of the halogen family and a refractory metal, and the
second source gas includes nitrogen.
6. The method of claim 1, and further comprising supplying a purge
gas onto the entire surface of the semiconductor substrate for a
predetermined period of time after said point in time A.sub.4 to
discharge by-products of the reaction between the first and second
source gases.
7. The method of claim 6, wherein said steps of supplying the first
source gas in the form of a pulse, supplying the second source gas
in the form of a pulse, and supplying the purge gas for a
predetermined period of time are repeated at least once to increase
the thickness of the barrier metal layer.
8. The method of claim 1, wherein the reaction of the first and
second source gases produces an impurity trapped in the barrier
metal layer, and further comprising supplying a purge gas onto the
entire surface of the semiconductor substrate, and supplying an
impurity-removing gas, capable of reacting with the impurity, onto
the entire surface of the semiconductor substrate for a
predetermined period of time beginning after point in time A.sub.4
and while the purge gas is being supplied, in order to remove
impurities from the barrier metal layer.
9. The method of claim 8, wherein the impurity removing-gas is
NH.sub.3.
10. The method of claim 8, wherein said steps of supplying the
first source gas in the form of a pulse, supplying the second
source gas in the form of a pulse, and supplying the
impurity-removing gas are repeated at least once to increase the
thickness of the barrier metal layer.
11. The method of claim 11, wherein said point in time A.sub.1
coincides with said point in time A.sub.3, and said point in time
A.sub.2 coincides with said point in time A.sub.4.
12. A method of manufacturing a barrier metal layer, comprising the
steps of: loading a semiconductor substrate into a processing
chamber; supplying a first source gas, containing a metal, onto the
entire surface of the semiconductor substrate in the form of a
pulse having a duration lasting from a point in time B.sub.1 to a
point in time B.sub.2, whereby the first source gas is chemically
and physically adsorbed at the surface; supplying a second source
gas, that is reactive with the first source gas to form the barrier
metal, onto the entire surface of the semiconductor substrate in
the form of a pulse having a duration lasting from a point in time
B.sub.3 to a point in time B.sub.4, whereby part of the second
source gas reacts with that part of the first source gas chemically
adsorbed at the surface of the semiconductor substrate to thereby
form the barrier metal layer by atomic layer deposition; and
supplying an impurity-removing gas onto the entire surface of the
semiconductor substrate in the form of a pulse having a duration
lasting from a point in time B.sub.5, that is later than said point
in time B.sub.4, to a point in time B.sub.6 to thereby remove
impurities from the barrier metal layer.
13. The method of claim 12, wherein said point in time B.sub.3 is
later in time than said point in time B.sub.2, and further
comprising supplying a purge gas onto the entire surface of the
semiconductor substrate beginning at a point in time that is no
later than said point in time B.sub.1 to purge the substrate of the
first source gas physically adsorbed at the surface thereof before
the second source gas is supplied.
14. The method of claim 12, wherein said point in time B.sub.3 is
later in time than said point in time B.sub.2, and further
comprising supplying a purge gas onto the entire surface of the
semiconductor substrate beginning at a point in time that is later
than said point in time B.sub.1 and is no later than said point in
time B.sub.2 to purge the substrate of the first source gas
physically adsorbed at the surface thereof before the second source
gas is supplied.
15. The method of claim 12, wherein the first source gas includes
an element of the halogen family and a refractory metal, and the
second source gas includes nitrogen.
16. The method of claim 12, wherein said steps of supplying the
first source gas in the form of a pulse, supplying the second
source gas in the form of a pulse, and supplying the
impurity-removing gas in the form of a pulse are repeated at least
once to increase the thickness of the barrier metal layer.
17. The method of claim 12, wherein the impurity-removing gas is
NH.sub.3.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method of manufacturing
semiconductor devices. More particularly, the present invention
relates to a method of manufacturing a barrier metal layer using
atomic layer deposition.
[0003] 2. Description of the Related Art
[0004] In the manufacture of semiconductor devices, a barrier metal
layer (for example, a TiN layer, a TaN layer, a WN layer) may be
formed between adjacent material layers in order to prevent mutual
diffusion or a chemical reaction from occurring between the
adjacent material layers. For example, in the manufacture of a
semiconductor memory device having a capacitor over bit-line (COB)
structure, barrier metal layers are typically interposed between a
lower electrode of a capacitor and a contact plug, between a
dielectric layer of a capacitor and an upper electrode of the
capacitor, between a conductive line and an insulating layer, and
between a via contact and an insulating layer.
[0005] However, as the integration density of semiconductor devices
increases, the topography of the surface on which a barrier metal
layer is to be deposited becomes more rugged. When a barrier metal
layer is formed on a rugged surface by a physical deposition
process such as sputtering, the step coverage of the barrier metal
layer is poor. Accordingly, a process providing excellent step
coverage must be used to form a barrier metal layer on a deposition
surface having a rugged topography. To this end, chemical vapor
deposition (CVD) has been proposed. Hereinafter, a barrier metal
layer formed by CVD will be referred to as a CVD barrier metal
layer.
[0006] In the process of manufacturing a CVD barrier metal layer, a
precursor including a halogen, such as Cl, is used as a typical
metal source gas. The manufacturing process of a CVD barrier metal
layer has an advantage in that the barrier metal is deposited
rapidly, and a drawback in that the halogen of the precursor fails
to fall out of the barrier metal layer and remains as an-impurity
within the barrier metal layer. The halogen remaining within the
barrier metal layer as described above may cause an adjacent
material layer (for example, an aluminum conductive line) to erode,
and may increase the resistivity of the barrier metal layer. Thus,
the amount of halogen remaining within the barrier metal layer must
be reduced so as to decrease the resistivity of the barrier metal
layer. In order to achieve this, the CVD barrier metal layer
manufacturing process must be performed at a high temperature.
[0007] For example, in a CVD barrier metal layer manufacturing
process using TiCl.sub.4 as a metal source gas, a deposition
temperature of at least 675.degree. C. is required to obtain a
resistivity of 200 .mu..OMEGA.-cm or less. However, when a barrier
metal layer is fabricated at a deposition temperature of
600.degree. C. or greater, the thermal budget of an underlayer
formed below the barrier metal layer is quite high, and secondary
problems such as the generation of thermal stress are created. For
instance, a CVD barrier metal layer must be formed over an Si
contact or a via contact at a deposition temperature of 500.degree.
C. or less if the Si contact or via contact are not to be unduly
thermally stressed. That is, the CVD barrier metal layer
manufacturing process must be performed at a low temperature. A
method of adding methylhydrazine (MH) to a metal source gas
TiCl.sub.4 can be used to facilitate the deposition of the barrier
metal at a low temperature. However, this technique has a drawback
in that the step coverage of the barrier metal layer is
compromised.
[0008] The above-described problem of thermal stress, prevailing in
the method of forming a CVD barrier metal layer manufacturing using
a metal source gas such as TiCl.sub.4 as a precursor, can be
overcome by using an organometallic precursor such as tetrakis
diethylamino Ti (TDEAT) or tetrakis dimethylamino Ti (TDMAT). That
is, this so-called MOCVD barrier metal layer manufacturing process
can be performed at a low temperature compared to the CVD barrier
metal layer manufacturing process. However, a MOCVD barrier metal
layer includes a large quantity of carbon impurities and therefore,
exhibits a high resistivity. Also, the MOCVD barrier metal layer
has worse step coverage than a barrier metal layer that is formed
using a metal source gas such as TiCl.sub.4 as a precursor.
[0009] Alternatively, the problems in the CVD barrier metal layer
manufacturing process posed by using a metal source gas such as
TiCl.sub.4 as a precursor can be overcome by a technique of
flushing the entire surface of a semiconductor substrate with an
impurity-removing gas after the barrier metal layer is formed.
However, the rate at which the impurity-removing gas must flow to
flush the surface of the semiconductor substrate is several tens to
several hundreds of times greater than that at which the reaction
gas flows into the reaction chamber. Accordingly, this technique
requires controlling the process conditions prevailing in the
reaction chamber, such as the pressure of the chamber and the like.
Effecting such a control takes time and thus, increases the total
time of the manufacturing process.
[0010] Also, a method of forming a barrier metal layer using an
atomic layer deposition (ALD) process has been used in an attempt
to overcome the problems posed by the use of Cl in the CVD barrier
metal layer manufacturing process. The conventional barrier metal
layer forming method using ALD has an advantage in that it can be
performed at a low temperature while minimizing the content of Cl
in the barrier metal layer. However, the mechanism by which the
barrier metal is deposited in ALD is chemical adsorption.
Therefore, the conventional barrier metal layer forming method
using ALD has a drawback in that the deposition rate is too slow
for use in manufacturing semiconductor devices. As a comparison,
the deposition rate of a typical CVD process used to form a TiN
layer is approximately several hundreds of .ANG./min. On the other
hand, the deposition rate at which a TiN layer can be formed using
the conventional ALD process is less than 100 .ANG./min, which is
very slow compared to when the CVD process is used.
SUMMARY OF THE INVENTION
[0011] A first object of the present invention is to provide a
method of manufacturing a barrier metal layer that makes use of
atomic layer deposition (ALD) but in which the deposition rate is
not too slow.
[0012] A second object of the present invention is to provide a
method of manufacturing a barrier metal layer using ALD, and by
which the deposition rate at which the ALD occurs can be increased
without an accompanying increase in the amount of impurities being
left in the barrier metal layer.
[0013] To achieve the first above object, the present invention
provides a method of manufacturing a barrier metal layer including:
(a) supplying a first source gas onto the entire surface of a
semiconductor substrate in the form of a pulse having a duration
lasting from a point in time A.sub.1 to a point in time A.sub.2,
and (b) supplying a second source gas, which reacts with the first
source gas, onto the entire surface of the semiconductor substrate
in the form of a pulse having a duration lasting from a point in
time A.sub.3 to a point in time A.sub.4, wherein A.sub.3 is at
least as early in time as A.sub.1 and no later in time than
A.sub.2. Preferably, point in time A.sub.4 is no earlier than point
in time A.sub.2. Moreover, the points in time the pulse of the
first source gas begins and ends can be the same as those at which
the pulse of the second source gas begins and ends. That is, point
in time A.sub.1 can coincide with point in time A.sub.3, and point
in time A.sub.2 can coincide with point in time A.sub.4.
[0014] A purge gas can be used to discharge by-products of the
reaction between the first and second source gases. The purge gas
is supplied onto the entire surface of the semiconductor substrate
beginning at a point in time that is earlier than or that coincides
with point in time A.sub.1. Alternatively, the purge gas can be
supplied onto the entire surface of the semiconductor substrate
beginning at a point in time that is later than point in time
A.sub.1 and is no later than point in time A.sub.3.
[0015] An impurity-removing gas can be additionally used to free
any impurities that have managed to become trapped within the
barrier metal layer. In this case, the method includes a step (c)
of supplying an impurity-removing gas onto the entire surface of
the semiconductor substrate for a predetermined period of time,
after point in time A.sub.4 and while the purge gas is still being
supplied.
[0016] The gas supply scheme comprising the steps (a), (b) and (c)
constitutes a cycle of operation, and the cycle can be repeated at
least once to increase the thickness of the barrier metal layer a
desired amount.
[0017] The first source gas can include a gas of the halogen
element family and a refractory metallic element, and the second
source gas can include nitrogen. The purge gas can be an inert gas
such as argon. The impurity removing gas can be NH.sub.3.
[0018] To achieve the second object, the present invention provides
a method of manufacturing a barrier metal layer, including: (a)
supplying a first source gas onto the entire surface of a
semiconductor substrate in the form of a pulse having a duration
lasting from a point in time B.sub.1 to a point in time B.sub.2,
(b) supplying a second source gas, which reacts with the first
source gas, onto the entire surface of the semiconductor substrate
in the form of a pulse having a duration lasting from a point in
time B.sub.3 to a point in time B.sub.4, whereby a barrier metal
layer is formed, and (c) supplying an impurity-removing gas onto
the entire surface of the semiconductor substrate in the form of a
pulse having a duration lasting from a point in time B.sub.5 to a
point in time B.sub.6 to remove impurities from the barrier metal
layer, wherein B.sub.3 is later in time than B.sub.2, and B.sub.5
is later in time than B.sub.4.
[0019] A purge gas can also be supplied onto the entire surface of
the semiconductor substrate, beginning at a point in time that is
earlier than or coincides with point in time B.sub.1, or that is
later than B.sub.1 and no later than point in time B.sub.2, to
remove all of the first source gas that is physically adsorbed at
the surface of the semiconductor substrate before the second source
gas is supplied and/or to discharge by-products of the reaction
between the first and second source gases.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The above and other objects, features and advantages of the
present invention will become more apparent from the following
detailed description of the preferred embodiments thereof made with
reference to the attached drawings, of which:
[0021] FIG. 1 is a timing diagram of the gas supply scheme of a
first embodiment of a method of fabricating a barrier metal layer
using atomic layer deposition (ALD) according to the present
invention;
[0022] FIG. 2 is a timing diagram of an alternative gas supply
scheme of the first embodiment of a method of fabricating a barrier
metal layer using atomic layer deposition (ALD) according to the
present invention; and
[0023] FIG. 3 is a timing diagram of the gas supply scheme of a
second embodiment of a method of fabricating a barrier metal layer
using atomic layer deposition (ALD) according to the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] The preferred embodiments of the present invention will now
be described in detail with reference to the attached drawings.
[0025] <First Embodiment>
[0026] In the first embodiment of a method of fabricating a barrier
metal layer according to the present invention, first, a
semiconductor substrate is loaded into a processing chamber of an
ALD apparatus. The semiconductor substrate may have a feature
having a predetermined aspect ratio. The feature may be a word
line, a conductive line such as a bit line, a contact plug, a via
contact, a capacitor upper electrode, or the like. After the
semiconductor substrate is loaded into the processing chamber,
first and second source gases and a purge gas are supplied to the
chamber according to the scheme shown in FIG. 1 to form a barrier
metal layer on a prescribed feature of the semiconductor
substrate.
[0027] The barrier metal layer is typically formed of a binary or
larger compound including a refractory metal and nitrogen. TiN is
representative of the material of the barrier metal layer.
Therefore, the first embodiment will be described in connection
with the formation of a Ti-containing layer as a barrier metal
layer.
[0028] Referring now to FIG. 1, while a purge gas is continuously
directed onto the entire surface of the semiconductor substrate, a
first source gas is pulsed onto the surface of a semiconductor
substrate for a duration lasting from a point in time A.sub.1 to a
point in time A.sub.2. The pulse of the first source gas is
chemically and physically adsorbed by the entire surface of the
semiconductor substrate according to the surface topology thereof.
However, some of the first source gas that has been physically
adsorbed is then removed by the purge gas because the purge gas is
being directed onto the entire surface of the semiconductor
substrate while the first source gas is being physically adsorbed.
The purge gas and the source gas entrained therein are discharged
to the outside of the processing chamber.
[0029] Note, FIG. 1 shows that the continuous supplying of the
purge gas is initiated at point in time A.sub.1. However, the
continuous supplying of the purge gas can be initiated before point
in time A.sub.1, or at a point in time A.sub.3 that is as early as
point in time A, but no later than point in time A.sub.2. Also, the
purge gas is an inert gas, such as argon.
[0030] On the other hand, a gas comprising a refractory metal (in
this case, Ti) is used as the first source gas. For example,
TiCI.sub.4 is used as the first source gas. However, other source
gases containing the barrier metal and capable of reacting with a
second source gas can be used. For instance, considering the
present example of a Ti-containing barrier metal layer, a
metallo-organic gas such as tetrakis diethyl amino titanium (TDEAT)
or tetrakis dimethyl amino titanium (TDMAT) can be used as the
first source gas.
[0031] Next, a pulse of the second source gas is directed onto the
surface of the semiconductor substrate for a duration lasting from
point in time A.sub.3 to a point in time A.sub.4, and while the
purge gas continues to be supplied onto the entire surface of the
semiconductor substrate. Note, at point in time A.sub.3 some of the
first source gas is still being supplied and thus, not all of the
first source gas physically adsorbed at the surface of the
semiconductor substrate has been removed at this time by the purge
gas. A.sub.4 is a point in time that occurs no earlier than point
in time A.sub.2 but occurs some time after point in time A.sub.3.
Thus, the points in time under which the scheme of the gas supply
is established are related as follows:
(A.sub.1.ltoreq.A.sub.3.ltoreq.A.sub.- 2, A.sub.2.ltoreq.A.sub.4,
A.sub.1.noteq.A.sub.2, and A.sub.3.noteq.A.sub.4). Under this
scheme, point in time A.sub.1 can coincide with point in time
A.sub.3, and point in time A.sub.2 can coincide with point in time
A.sub.4, in which case the first and second source gases would be
pulsed beginning at the same time and continuing for the same
duration.
[0032] In any case, the pulsing of the second source gas is
initiated before or at the same time the pulsing of the first
source gas terminates. The pulse of the second source gas
terminates after or at the same time the pulsing of the first
source gas terminates. After the pulse of the second source gas
terminates, only the purge gas is supplied along the entire surface
of the semiconductor substrate for a duration lasting from point in
time A.sub.4 to a point in time A.sub.5, thereby discharging
by-products of the reaction of the first and second source
gases.
[0033] A gas including a non-metallic element (N) of the barrier
metal layer (TiN) is used as the second source gas. For example,
NH.sub.3 is used as the second source gas. However, other gases
which react with the first source gas and contain nitrogen, such as
N.sub.2, can be used as the second source gas.
[0034] Now, in ALD, that part of the first source gas that has been
chemically adsorbed reacts with the second source gas. However,
from point in time A.sub.3 to point in time A.sub.4, i.e. the
duration of the pulse of the second source gas, the mechanism by
which the barrier metal (TiN) is deposited no longer consists of
ALD because the first source gas physically adsorbed at the surface
of the semiconductor substrate has not been completely removed by
the purge gas. Accordingly, the second source gas reacts with not
only that part of the first source gas that has been chemically
adsorbed at the surface of the semiconductor substrate but also
that part of the first source gas that has been physically
adsorbed. Thus, although ALD results from the reaction between that
part of the first source gas chemically adsorbed at the surface of
the semiconductor substrate and the second source gas, CVD results
from the reaction between that part of the first source gas
physically adsorbed and the second source gas. Consequently, the
ALD that takes place provides a 100% step coverage and the CVD that
takes place provides a high deposition rate.
[0035] Moreover, as was described above, a large amount of
impurities (Cl) are present in a barrier metal layer (TiN) when the
barrier metal layer is formed by CVD. However, in the present
invention, impurity-containing gases HCI and TiCI.sub.x generated
as by-products are discharged from the processing chamber by
flushing the entire surface of the semiconductor substrate with an
inert gas while the first and second source gases react with each
other (A.sub.3-A.sub.4) and for a predetermined period of time
(that is, for a duration of A.sub.4-A.sub.5) after the pulse of the
second source gas terminates. Consequently, impurities (Ci) are
prevented from being entrapped within the deposited material. That
is, even though the present invention employs the deposition
mechanism of CVD, namely a process in which a high temperature is
required to suppress the level of impurities in the barrier metal
layer, the method of the present invention can be performed at a
low temperature (for example, 450 to 500.degree. C.) without
producing a high level of impurities in the barrier metal layer
because the present invention also employs ALD. Thus, the present
invention also suppresses thermal stress and thereby decreases the
thermal budget of the layer (underlayer) beneath the barrier metal
layer.
[0036] In the first embodiment, the duration of A.sub.1 to A.sub.5
is a cycle T.sub.1, and a barrier metal layer can be formed to a
desired thickness by repeating the cycle T.sub.1 a predetermined
number of times. Also, the method can also comprise a step of
pulsing an impurity-removing gas to further ensure that impurities
(Cl) are prevented from being trapped within the barrier metal
layer (TiN). The thickness of the TiN layer formed after one cycle
is established by the process recipe under which the first and
second source gases, and the purge gas (and impurity-removing gas)
are supplied into the processing chamber.
[0037] As shown in FIG. 2, the impurity-removing gas can be
supplied for a duration beginning at point in time A.sub.6 and
ending at point in time A.sub.7, while the purge gas is being
directed onto the surface of a semiconductor substrate and after
the pulse of the second source gas terminates. The
impurity-removing gas reacts with impurities trapped in the barrier
metal layer during the reaction of the first and second source
gases, and frees the impurities from the barrier metal layer. For
example, the impurity-removing gas reduces the impurities to their
constituent elements. Also, the impurity-removing gas can easily
diffuse into the metal barrier layer and thereby react with the
impurities because the thickness of the barrier metal layer formed
during the time period from A.sub.1 to A.sub.4 is very thin (about
10 to 20 .ANG.). Accordingly, in contrast with the conventional
technique of flushing the barrier metal layer with an
impurity-removing gas after the barrier metal layer has been
completed, the technique of the present invention in which
impurity-removing gas is supplied after one of a plurality of
cycles can remove impurities (Cl) from the barrier metal layer
using only a tiny flow of the impurity-removing gas.
[0038] NH.sub.3 can be used as the impurity-removing gas. In this
case, the processing apparatus does not need a separate gas supply
line dedicated to the impurity-removing gas because the
impurity-removing gas and the second source gas are the same.
Rather, another pulse of the second source gas can be supplied from
the time period A.sub.6-A.sub.7 (see reference character I). On the
other hand, gases other than NH.sub.3 can be used as the
impurity-removing gas. In these cases, a separate gas supply line
dedicated to the impurity-removing gas is required.
[0039] When the impurity-removing gas is NH.sub.3, the
impurity-removing gas diffuses into the barrier metal layer that
was formed during the time period of from A.sub.1 to A.sub.4 and
reacts with impurities (Cl) within the layer according to the
following chemical equation, and frees the impurities (Cl) from the
barrier metal layer in the form of gas (HCI).
[0040] [Chemical Equation]
TiNxCly(S)+NH.sub.3(g).fwdarw.TiN(s)+HCl(g)
[0041] <Second Embodiment>
[0042] Next, a second embodiment of a method of forming a barrier
metal layer will be described. Like the first embodiment, the
second embodiment of the present invention can also reduce the
amount of impurities remaining in a barrier metal layer to a
greater extent than the conventional ALD method without seriously
compromising the deposition rate. For the sake of convenience, the
second embodiment will also be described as applied to the forming
of a TiN barrier metal layer.
[0043] Referring to FIG. 3, in the second embodiment of the present
invention, first, a semiconductor substrate is loaded into a
processing chamber of an ALD apparatus. Next, a first source gas is
supplied in the form of a pulse, beginning at a point in time
B.sub.1 and terminating at a point in time B.sub.2, while a purge
gas is being continuously supplied onto the entire surface of the
semiconductor substrate. The first source gas is chemically and
physically adsorbed at the surface of the semiconductor substrate
according to the topology of the surface.
[0044] FIG. 3 shows that the flow of purge gas is initiated at the
point in time B.sub.1. However, the flow of the purge gas can be
initiated prior to the point in time B.sub.1, or from any point in
time as early as B.sub.1 and no later than B.sub.2. Then, the
physically-adsorbed part of the first source gas is removed by the
purge gas from the point in time B.sub.2 to a point in time
B.sub.3. Thereafter, the second source gas is supplied in the form
of a pulse beginning from the point in time B.sub.3 and terminating
at the point in time B.sub.4 while the purge gas continuous to be
supplied onto the entire surface of the semiconductor substrate.
Then, from the point in time B.sub.4 to a point in time B.sub.5
only the purge gas is supplied, whereby by-products generated by
the reaction of the first and second source gases are discharged
from the chamber. Then, the impurity-removing gas is supplied in
the form of a pulse beginning from the point in time B.sub.5 and
terminating at a point in time B.sub.6 while the purge gas
continuous to be supplied onto the entire surface of the
semiconductor substrate. Note, the first and second source gases
and the impurity-removing gas can be the same as those used in the
first embodiment.
[0045] Also, similar to the first embodiment, the impurity-removing
gas and the second source gas can be of the same type, whereby the
processing apparatus does not require a separate gas supply line
dedicated to the impurity-removing gas. That is, another pulse of
the second source gas can be supplied during the time period of
B.sub.5-B.sub.6 (see reference character II). On the other hand,
when gases other than NH.sub.3 are used as the impurity-removing
gas, a separate gas supply line dedicated to the impurity-removing
gas is required.
[0046] In this embodiment, impurities formed during the period of
time from B.sub.1 to B.sub.4 are removed from the barrier metal
layer by the impurity-removing gas. Thereafter, from the point in
time B.sub.6 to a point in time B.sub.7, the purge gas discharges
by-products of the reaction between the impurity-removing gas and
the impurities.
[0047] The time period of B.sub.1 to B.sub.7 represents a cycle
T.sub.2, and the barrier metal layer can be formed to a desired
thickness by repeating the cycle T.sub.2. In the second embodiment,
the impurity-removing gas is supplied after the supply of the
second source gas is terminated, so that fewer impurities remain
within the barrier metal layer than when the prior art method is
used.
[0048] Consideration of the content of impurities within the
barrier metal layer aside, the deposition rate of the barrier metal
in ALD can be typically controlled by adjusting the process recipe
under which the first and second source gases are supplied. That
is, the deposition rate of the barrier metal can be increased by
controlling the supply of the first and second source gases.
However, increasing the deposition rate of the barrier metal in
this way is normally accompanied by a corresponding increase in the
amount of impurities within the barrier metal layer. That is, there
is a limit to ALD in changing the process recipe to increase the
deposition rate of the barrier metal. However, in the second
embodiment of the present invention, the use of the
impurity-removing gas allows the process recipe under which the
first and second source gases are supplied to be adjusted for
increasing the deposition rate of the barrier metal without giving
rise to a corresponding increase in the amount of impurities
remaining within the barrier metal layer. In other words, the
second embodiment provides a significant degree of freedom in
adjusting the process recipe under which the first and second
source gases are supplied.
[0049] A case in which the first and second embodiments of the
present invention are applied to the manufacture of a binary
barrier metal layer (TiN) will now be described in detail. However,
the present invention is not limited to the manufacture of a TiN
binary metal layer. Rather, the present invention is also
applicable to the manufacture of other binary barrier metal layers
such as a TaN layer, a WN layer, an AIN layer, a CrN layer and a BN
layer. The type of first and second source gases and
impurity-removing gas to be used when manufacturing barrier metal
layers other than the TiN barrier layer will be readily apparent to
those of ordinary skill in the art.
[0050] For example, when the barrier metal layer is formed of AIN,
an AlClx gas can be used as the first source gas, and NH.sub.3 can
be used as the second source gas and as the impurity-removing
gas.
[0051] Also, the present invention is not applicable only to the
manufacture of binary barrier metal layers, but can also be applied
to the manufacture of barrier metal layers formed of larger
compounds. For example, the present invention can also be applied
to the manufacture of a TiBN layer, a TaBN layer, a TiAIN layer, a
TaAIN layer, a TiSiN layer, a TaSiN layer, a TiCN layer, a WBN
layer, and the like.
[0052] For example, when the barrier metal layer is formed of TIAIN
using the first embodiment of the present invention, a first source
gas (for example, TiCI.sub.4), a second source gas (for example,
trimethyl aluminum (TMA)) and a third source gas (for example,
NH.sub.3) can be supplied according to the following schemes. Note,
in these schemes, the duration of the pulse of the first source gas
is from a point in time C.sub.1 to a point in time C.sub.2, the
duration of the pulse of the second source gas is from a point in
time C.sub.3 to a point in time C.sub.4, and the duration of the
pulse of the third source gas is from a point in time C.sub.5 to a
point in time C.sub.6.
[0053] [First Scheme]
[0054] C.sub.1.ltoreq.C.sub.3.ltoreq.C.sub.2and
C.sub.1.ltoreq.C.sub.5.lto- req.C.sub.2
[0055] [Second Scheme]
[0056] C.sub.1.ltoreq.C.sub.3.ltoreq.C.sub.2 and
C.sub.3.ltoreq.C.sub.5.lt- oreq.C.sub.4
[0057] After the first through third source gases are supplied
according to any one of the above schemes, the purge gas is
directed onto the entire surface of the semiconductor substrate for
a predetermined period of time, thereby completing the cycle. The
cycle is repeated a predetermined number of times to form a barrier
metal layer (TIAIN) having a desired thickness.
[0058] The barrier metal layer of TiAIN can also be formed using
the second embodiment of the present invention, under the schemes
set forth above. In this case, the deposition mechanism includes
CVD along with ALD. Thus, the second embodiment will also exhibit a
higher deposition rate than the prior art. Also, the purge gas is
continuously supplied onto the entire surface of the semiconductor
substrate while the source gases are being supplied. Thus, the
amount of impurities remaining within the barrier metal layer are
minimal even though the process is carried at a temperature as low
as that used to carry out the conventional ALD process.
Furthermore, in the second embodiment, an impurity-removing gas can
be supplied in the form of a pulse after the first through third
source gases are suppled, as in the first embodiment, thereby
reducing the amount of impurities within the barrier metal
layer.
[0059] According to one aspect of the present invention, the
barrier metal layer is formed by ALD and CVD, so that the
deposition rate of the barrier metal is greater than if the barrier
metal layer were formed only through ALD. Also, a purge gas is
continuously supplied onto the entire surface of the semiconductor
substrate during the manufacture of the barrier metal layer, so
that the amount of impurities remaining within the barrier metal
layer is minimized despite the fact that the method is carried out
at a low temperature suitable for ALD.
[0060] According to another aspect of the present invention, the
barrier metal layer is formed only through ALD. However, an
impurity-removing gas is supplied during the process to free
impurities that have been trapped in the barrier metal layer.
Therefore, the process recipe for the source gases has a high
degree of freedom, can be changed to a great extent to increase the
deposition rate of the barrier metal. Therefore, even though the
barrier metal layer is formed only through ALD, the barrier metal
can be deposited at higher and higher rates without corresponding
increases in the impurity content of the barrier metal layer.
[0061] Although the present invention has been described with
reference to the preferred embodiments thereof, various
modifications thereof will be apparent to those of ordinary skill
in the art. All such modifications are seen to be within the true
spirit and scope of the invention as defined by the appended
claims.
* * * * *