U.S. patent application number 12/729973 was filed with the patent office on 2010-07-08 for method of forming metal oxide and apparatus for performing the same.
Invention is credited to Dae-Youn Kim, Weon-Hong Kim, Young-Hoon Kim, Jung-Min Park, Min-Woo Song, Sun-Mi Song, Seok-Jun Won, Yong-Min Yoo.
Application Number | 20100170441 12/729973 |
Document ID | / |
Family ID | 39151831 |
Filed Date | 2010-07-08 |
United States Patent
Application |
20100170441 |
Kind Code |
A1 |
Won; Seok-Jun ; et
al. |
July 8, 2010 |
Method of Forming Metal Oxide and Apparatus for Performing the
Same
Abstract
In a method and an apparatus for forming metal oxide on a
substrate, a source gas including metal precursor flows along a
surface of the substrate to form a metal precursor layer on the
substrate. An oxidizing gas including ozone flows along a surface
of the metal precursor layer to oxidize the metal precursor layer
so that the metal oxide is formed on the substrate. A radio
frequency power is applied to the oxidizing gas flowing along the
surface of the metal precursor layer to accelerate a reaction
between the metal precursor layer and the oxidizing gas.
Acceleration of the oxidation reaction may improve electrical
characteristics and uniformity of the metal oxide.
Inventors: |
Won; Seok-Jun; (Seoul,
KR) ; Yoo; Yong-Min; (Yuseong-gu, KR) ; Song;
Min-Woo; (Suwon-si, KR) ; Kim; Dae-Youn;
(Daedeok-gu, KR) ; Kim; Young-Hoon; (Daedeok-gu,
KR) ; Kim; Weon-Hong; (Suwon-si, KR) ; Park;
Jung-Min; (Ansan-si, KR) ; Song; Sun-Mi;
(Yuseong-gu, KR) |
Correspondence
Address: |
F. CHAU & ASSOCIATES, LLC
130 WOODBURY ROAD
WOODBURY
NY
11797
US
|
Family ID: |
39151831 |
Appl. No.: |
12/729973 |
Filed: |
March 23, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11775111 |
Jul 9, 2007 |
7708969 |
|
|
12729973 |
|
|
|
|
Current U.S.
Class: |
118/723I ;
257/E21.482 |
Current CPC
Class: |
C01G 27/02 20130101;
C01G 23/047 20130101; C01G 35/00 20130101; C01P 2006/40 20130101;
C01G 25/02 20130101 |
Class at
Publication: |
118/723.I ;
257/E21.482 |
International
Class: |
H01L 21/46 20060101
H01L021/46 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 10, 2006 |
KR |
2006-64250 |
Claims
1. Apparatus for forming metal oxide comprising: a substrate stage
having a support region for supporting a substrate and a peripheral
region surrounding the support region; a chamber disposed on the
peripheral region to define a space in which the substrate is
placed, the chamber having a gas inlet port for supplying a source
gas including metal precursor to allow the source gas to flow along
a surface of a substrate so that a metal precursor layer is formed
on the substrate and supplying an oxidizing gas including ozone to
allow the oxidizing gas to flow along a surface of the metal
precursor layer to oxidize the metal precursor layer so that metal
oxide is formed on the substrate; and a radio frequency power
source connected to the chamber for applying a radio frequency
power to the oxidizing gas flowing along the surface of the metal
precursor layer to accelerate a reaction between the metal
precursor layer and the oxidizing gas.
2. The apparatus of claim 1, further comprising: a first gas supply
section for supplying the source gas onto the substrate; and a
second gas supply section for supplying the oxidizing gas onto the
metal precursor layer.
3. The apparatus of claim 2, wherein the second gas supply section
comprises an ozone generator.
4. The apparatus of claim 3, wherein a concentration of the ozone
in the oxidizing gas is in a range of about 100 g/m.sup.3 to about
1000 g/m.sup.3.
5. The apparatus of claim 2, further comprising a third gas supply
section for supplying an oxygen gas onto the metal precursor layer
before supplying the oxidizing gas.
6. The apparatus of claim 2, further comprising a fourth gas supply
section for supplying a purge gas onto the metal precursor layer
and the metal oxide.
7. The apparatus of claim 1, wherein the chamber comprising: a
cover disposed on the peripheral region of the stage; and a radio
frequency electrode connected to the cover to face the substrate
supported by the stage.
8. The apparatus of claim 7, wherein the cover comprising: a
ceiling portion disposed over the stage; and a protruding portion
extending downwardly from the ceiling portion and disposed on the
peripheral region of the stage, wherein the protruding portion is
ring-shaped.
9. The apparatus of claim 8, wherein the radio frequency electrode
is disposed on a lower surface of the ceiling portion and is
disk-shaped.
10. The apparatus of claim 9, wherein the gas inlet port is defined
by an inner surface of the protruding portion and an outer surface
of the radio frequency electrode, and the radio frequency electrode
has channels connected to the gas inlet port for supplying the
source gas and the oxidizing gas.
11. The apparatus of claim 10, wherein each of the channels widens
towards the outer surface of the radio frequency electrode.
12. The apparatus of claim 9, wherein the chamber has an outlet
port disposed opposite the gas inlet port.
13. The apparatus of claim 1, further comprising an exhauster
connected to the chamber for exhausting the source gas, the
oxidizing gas and by-products of the reaction.
14. The apparatus of claim 1, further comprising a driving section
for rotating the stage.
15. Apparatus for forming metal oxide comprising: a chamber to
define a space in which a substrate is placed, the chamber having a
gas inlet port for supplying a source gas including metal precursor
to allow the source gas to flow along a surface of the substrate so
that a metal precursor layer is formed on the substrate and
supplying an oxidizing gas including ozone to allow the oxidizing
gas to flow along a surface of the metal precursor layer to oxidize
the metal precursor layer so that metal oxide is formed on the
substrate; a radio frequency power source connected to the chamber
for applying a radio frequency power to the oxidizing gas flowing
along the surface of the metal precursor layer to accelerate a
reaction between the metal precursor layer and the oxidizing gas;
and an exhauster connected to the chamber for exhausting the source
gas, the oxidizing gas and by-products of the reaction.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 11/775,111, filed on Jul. 9, 2007, which in turn claims
priority under 35 USC .sctn.119 from Korean Patent Application No.
2006-64250, filed on Jul. 10, 2006, the contents of both of which
are herein incorporated by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present disclosure is directed to a method of forming
metal oxide and an apparatus for performing the same. More
particularly, the present disclosure is directed to a method of
forming metal oxide on a semiconductor substrate such as a silicon
wafer using a plasma-enhanced atomic layer deposition (PEALD) and
an apparatus for performing the method.
[0004] 2. Description of the Related Art
[0005] Semiconductor memory devices have been more highly
integrated and operated at higher speeds by significantly reducing
the size of memory cells in the devices. A reduced memory cell size
has correspondingly decreased the area available for forming
transistors and capacitors. Accordingly, lengths of transistor gate
electrodes have been decreased.
[0006] Decreased length of the transistor gate electrode causes a
corresponding decrease in a thickness of a gate insulating layer
beneath the gate electrode. When the gate insulating layer is
formed from silicon oxide (SiO.sub.2) and has a thickness of less
than about 20 .ANG., the operation of the transistor may be
degraded by an increase in leakage current due to electron
tunneling, infiltration of impurities in the gate electrode, and/or
decrease in threshold voltage.
[0007] Capacitor capacitance in the memory cell decreases as the
memory cell decreases in size. Reduction of the cell capacitance
may cause the operation of the memory cell to be degraded by
deterioration of data readability in the memory cell and/or
increase in a soft error rate. As a result, the memory device may
not properly operate at a relatively low voltage due to the
reduction in the cell capacitance.
[0008] To improve the cell capacitance of the semiconductor memory
device having a small cell region, it is known to form a dielectric
layer having a very thin thickness. It is also known to form a
lower electrode having a cylindrical shape or a fin shape so as to
increase an effective area of the capacitors. In a dynamic random
access memory (DRAM) device having a storage capacity of more than
about 1 gigabyte, however, the above-mentioned approaches cannot be
employed for manufacturing the DRAM device because these approaches
do not enable a sufficiently high cell capacitance for the DRAM
device to be obtained.
[0009] To address the above-mentioned challenges, it is known to
form a dielectric layer using metal oxide having a high dielectric
constant that is greater than that of silicon nitride. The metal
oxide may be formed by an atomic layer deposition (ALD), a PEALD,
and the like.
[0010] Particularly, metal oxide may be formed on a semiconductor
substrate by a lateral flow type PEALD process. The metal oxide
formed by the lateral flow type PEALD process may have improved
electrical characteristics in general.
[0011] However, in the case where cylindrical lower electrodes
having a high aspect ratio are formed on a semiconductor substrate
and a metal oxide layer is then formed on the cylindrical lower
electrodes by the lateral flow type PEALD process, the metal oxide
layer may have poorer electrical characteristics in comparison with
a metal oxide layer formed by a conventional ALD process.
SUMMARY OF THE INVENTION
[0012] Exemplary embodiments of the present invention provide
methods of forming metal oxide having improved electrical
characteristics.
[0013] Exemplary embodiments of the present invention also provide
apparatuses for forming metal oxide having improved electrical
characteristics.
[0014] In accordance with an aspect of the present invention, a
source gas including metal precursor may be supplied onto a
substrate to allow the source gas to flow along a surface of the
substrate so that a metal precursor layer is formed on the
substrate. An oxidizing gas including ozone may be supplied onto
the metal precursor layer to allow the oxidizing gas to flow along
a surface of the metal precursor layer so that the metal precursor
layer may be oxidized. Metal oxide may be formed on the substrate.
A radio frequency (RF) power may be applied to the oxidizing gas
flowing along the surface of the metal precursor layer, so that an
oxidation reaction between the metal precursor layer and the
oxidizing gas may be accelerated.
[0015] In some exemplary embodiments of the present invention,
examples of metal that may be used for the metal precursor may
include zirconium (Zr), hafnium (Hf), aluminum (Al), tantalum (Ta),
titanium (Ti), lanthanum (La), strontium (Sr), barium (Ba),
praseodymium (Pr), lead (Pb), etc. These can be used alone or in a
combination thereof.
[0016] In some exemplary embodiments of the present invention, a
concentration of the ozone in the oxidizing gas may be in a range
of about 100 g/m.sup.3 to about 1000 g/m.sup.3. Particularly, a
concentration of the ozone in the oxidizing gas may be in a range
of about 100 g/m.sup.3 to about 500 g/m.sup.3. For example, a
concentration of the ozone in the oxidizing gas may be about 200
g/m.sup.3.
[0017] In some exemplary embodiments of the present invention, the
supply of the oxidizing gas and the application of the RF power may
be performed substantially simultaneously.
[0018] In some exemplary embodiments of the present invention, an
oxygen gas may be supplied onto the substrate before supplying the
oxidizing gas. The oxygen gas may be supplied for about 0.1 to
about 3 seconds.
[0019] In some exemplary embodiments of the present invention, an
interior of a process chamber in which the substrate is placed may
be purged by a purge gas after forming the metal precursor layer,
and the interior of the process chamber may be purged by a purge
gas after forming the metal oxide.
[0020] In some exemplary embodiments of the present invention, the
source gas and the oxidizing gas may flow from a first edge portion
of the substrate towards a second edge portion opposite to the
first edge portion of the substrate.
[0021] In some exemplary embodiments of the present invention, the
interior of the process chamber may be maintained at a pressure in
a range of about 0.1 to about 10 Torr, and the substrate may be
maintained at a temperature in a range of room temperature to about
450.degree. C.
[0022] In some exemplary embodiments of the present invention,
after forming the metal oxide, the substrate may be rotated by a
predetermined angle, and then the supply of the source gas and the
oxidizing gas, and the application of the RF power may be
repeatedly performed.
[0023] In some exemplary embodiments of the present invention, the
substrate may be continuously rotated, and the supply of the source
gas and the oxidizing gas, and the application of the RF power may
be repeatedly performed while rotating the substrate.
[0024] In accordance with another aspect of the present invention,
an apparatus for forming metal oxide may include a substrate stage,
a chamber and a RF power source. The substrate stage may have a
support region for supporting a substrate and a peripheral region
surrounding the support region. The chamber may be disposed on the
peripheral region of the stage to define a space in which the
substrate is placed. The space may be defined by the support region
of the stage and inner surfaces of the chamber. The chamber may
have a gas inlet port for supplying a source gas including metal
precursor to allow the source gas to flow along a surface of the
substrate so that a metal precursor layer is formed on the
substrate. The gas inlet port may also supply an oxidizing gas
including ozone to allow the oxidizing gas to flow along a surface
of the metal precursor layer so that the metal precursor layer is
oxidized. The metal oxide may be formed on the substrate by
oxidizing the metal precursor layer. The RF power source may be
connected to the chamber for applying a RF power to the oxidizing
gas flowing along the surface of the metal precursor layer so that
an oxidation reaction between the metal precursor layer and the
oxidizing gas may be accelerated.
[0025] In some exemplary embodiments of the present invention, the
apparatus may further include a first gas supply section connected
to the chamber for supplying the source gas onto the substrate and
a second gas supply section connected to the chamber for supplying
the oxidizing gas onto the metal precursor layer. Example of the
second gas supply section may include an ozone generator.
[0026] In some exemplary embodiments of the present invention, the
apparatus may further include a third gas supply section for
supplying a purge gas onto the metal precursor layer and the metal
oxide, and a fourth gas supply section for supplying an oxygen gas
onto the metal precursor layer before supplying the oxidizing
gas.
[0027] In some exemplary embodiments of the present invention, the
chamber may include a cover disposed on the peripheral region of
the stage and a RF electrode connected to the cover to face the
substrate supported by the stage. Also, the RF electrode is
connected to the RF power source.
[0028] In some exemplary embodiments of the present invention, the
cover may include a ceiling portion disposed over the stage and a
protruding portion extending downwardly from an edge of the ceiling
portion and disposed on the peripheral region of the stage. The
protruding portion may be ring-shaped, and the RF electrode may be
disk-shaped and be disposed on a lower surface of the ceiling
portion.
[0029] In some exemplary embodiments of the present invention, the
gas inlet port may be defined by an inner surface of the protruding
portion and an outer surface of the RF electrode. The RF electrode
may have channels connected to the gas inlet port for supplying the
source gas and the oxidizing gas. Each of the channels may widen
towards the outer surface of the radio frequency electrode.
[0030] In some exemplary embodiments of the present invention, the
chamber may have an outlet port disposed opposite the gas inlet
port. An exhauster may be connected to the outlet port for
exhausting the source gas, the oxidizing gas and by-products of the
oxidation reaction.
[0031] In some exemplary embodiments of the present invention, the
apparatus may further include a driving section for rotating the
stage so as to rotate the substrate supported by the stage.
[0032] In accordance with the exemplary embodiments of the present
invention, the oxidation reaction between the metal precursor layer
formed on the substrate and the oxidizing gas may be accelerated by
applying the RF power. The acceleration of the oxidation reaction
may improve electrical characteristics and uniformity of the metal
oxide on the substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] Exemplary embodiments of the present invention will become
readily apparent along with the following detailed description when
considered in conjunction with the accompanying drawings.
[0034] FIG. 1 is a schematic view illustrating an apparatus for
forming metal oxide in accordance with an exemplary embodiment of
the present invention.
[0035] FIG. 2 is an enlarged cross-sectional view illustrating a
gas inlet port in FIG. 1.
[0036] FIG. 3 is an enlarged cross-sectional view illustrating an
outlet port in FIG. 1.
[0037] FIG. 4 is a schematic view illustrating a gas supply section
in FIG. 1.
[0038] FIG. 5 is an enlarged cross-sectional view illustrating a RF
electrode in FIG. 1.
[0039] FIG. 6 is a plan view illustrating the RF electrode in FIG.
1.
[0040] FIG. 7 is a flow chart illustrating a method of forming
metal oxide on a substrate using the apparatus in FIG. 1.
[0041] FIGS. 8 and 9 are graphs showing leakage current
characteristics of metal oxide layers formed by a conventional
method of forming metal oxide.
[0042] FIG. 10 is a graph showing leakage current characteristics
of a metal oxide layer formed by a method of forming metal oxide in
accordance with an exemplary embodiment of the present
invention.
[0043] FIG. 11 is a graph showing leakage current characteristics
of hafnium oxide layers formed by a conventional method of forming
metal oxide and a hafnium oxide layer formed by a method of forming
metal oxide in accordance with an exemplary embodiment of the
present invention.
[0044] FIG. 12 is a graph showing leakage current characteristics
of hafnium oxide layers formed by methods of forming metal oxide in
accordance with exemplary embodiments of the present invention.
[0045] FIG. 13 is a graph showing leakage current characteristics
of a zirconium oxide layer formed by a method of forming metal
oxide in accordance with an exemplary embodiment of the present
invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0046] Embodiments of the invention now will be described more
fully hereinafter with reference to the accompanying drawings, in
which exemplary embodiments of the invention are shown. This
invention may, however, be embodied in many different forms and
should not be construed as limited to the embodiments set forth
herein. Like reference numerals refer to like elements throughout.
It will be understood that when an element is referred to as being
"on" another element, it can be directly on the other element or
intervening elements may be present.
[0047] FIG. 1 is a schematic view illustrating an apparatus for
forming metal oxide in accordance with an exemplary embodiment of
the present invention.
[0048] Referring to FIG. 1, an apparatus for forming metal oxide
100 may be used for forming metal oxide having a high dielectric
constant on a semiconductor substrate 10 such as a silicon wafer.
Particularly, the apparatus may be used for forming metal oxide
such as hafnium oxide (HfO), zirconium oxide (ZrO), aluminum oxide
(AlO), tantalum oxide (TaO), titanium oxide (TiO), lanthanum oxide
(LaO), strontium oxide (SrO), barium oxide (BaO), praseodymium
oxide (PrO), lead oxide (PbO), etc, on the semiconductor substrate
10. A layer including the metal oxide may be used as a gate
insulating layer of a transistor, a dielectric layer of a
capacitor, and the like.
[0049] The semiconductor substrate 10 may be supported by a
substrate stage 200. The stage 200 may have a support region 210
for supporting the semiconductor substrate 100 and a peripheral
region 220 surrounding the support region 210. An upper surface of
the peripheral region 220 may be disposed higher than an upper
surface of the support region 210. For example, the upper surface
of the peripheral region 220 may have a height substantially the
same as that of an upper surface of the semiconductor substrate 10
placed on the support region 210.
[0050] A heater 230 may be disposed in the stage 200 to heat the
semiconductor substrate 10 to a predetermined process temperature.
For example, the metal oxide may be formed at a temperature in a
range of room temperature to about 450.degree. C. Alternatively, a
heating block for heating the semiconductor substrate 10 may be
coupled to a lower portion of the stage 200.
[0051] A process chamber 300 may be disposed on the peripheral
region 220 to define a space in which the semiconductor substrate
10 is placed. The process chamber 300 may include a cover 310 and a
RF electrode 350.
[0052] The cover 310 may include a ceiling portion 320 and a
protruding portion 330. The ceiling portion 320 may be disk-shaped
and disposed over the stage 200. The protruding portion 330 may
extend downwardly from an edge of the ceiling portion 320 and may
have a ring shape. Further, the protruding portion 330 is disposed
on the peripheral region 220 of the stage 200. The RF electrode 350
may be disposed on a lower surface of the ceiling portion 320 to
face the semiconductor substrate 10 placed on the support region
210 of the stage 200. For example, the RF electrode 350 may be
coupled to the lower surface of the ceiling portion 320 by a
plurality of fasteners.
[0053] FIG. 2 is an enlarged cross-sectional view illustrating a
gas inlet port, and FIG. 3 is an enlarged cross-sectional view
illustrating an outlet port.
[0054] Referring to FIGS. 2 and 3, the process chamber 300 may have
a gas inlet port 302, which supplies a source gas including metal
precursor and an oxidizing gas including ozone, and an outlet port
304, which exhausts the gases and by-produces of an oxidation
reaction using the oxidizing gas.
[0055] The gas inlet port 302 may be adjacent to a first edge
portion of the semiconductor substrate 10, and the outlet port 304
may be adjacent to a second edge portion opposite to the first edge
portion of the semiconductor substrate 10.
[0056] The gas inlet port 302 may be defined by a first inner
surface 332 of the protruding portion 330 and a first outer surface
352 of the RF electrode 350. The outlet port 304 may be defined by
a second inner surface 334 of the protruding portion 330 and a
second outer surface 354 of the RF electrode 350. The first and
second inner surfaces 332 and 334 of the protruding portion 330 may
be disposed to face with each other, and the first and second outer
surfaces 352 and 354 may be disposed on opposite sides of the RF
electrodes 350.
[0057] The source gas may flow along the upper surface of the
semiconductor substrate 10 from the gas inlet port 302 towards the
outlet port 304. Thus, a metal precursor layer may be formed on the
semiconductor substrate 10. The oxidizing gas may flow along an
upper surface of the metal precursor layer from the gas inlet port
302 towards the outlet port 304, to thereby oxidize the metal
precursor layer. Thus, metal oxide may be formed on the
semiconductor substrate 10 by an oxidation reaction between the
metal precursor layer and the oxidizing gas, thereby forming a
metal oxide layer on the semiconductor substrate 10. That is, the
source gas and the oxidizing gas may be supplied from the first
edge portion towards the second edge portion of the semiconductor
substrate 10.
[0058] Referring again to FIG. 1, a gas supply section 400 for
supplying the source gas and the oxidizing gas may be connected to
the ceiling portion 320 of the process chamber 300 by gas supply
pipes. The source gas, the oxidizing gas and by-products formed
while forming the metal oxide may be exhausted by an exhauster 500
that is connected to the ceiling port 320 of the process chamber
300 by an exhaust pipe.
[0059] FIG. 4 is a schematic view illustrating the gas supply
section 400.
[0060] Referring to FIG. 4, the gas supply section 400 may include
a first gas supply section 410 for supplying the source gas and a
second gas supply section 420 for supplying the oxidizing gas.
[0061] Examples of the first gas supply section 410 may include a
liquid delivery system (LDS), a bubbler including a bubbling
container, and the like.
[0062] Examples of metal that may be used for the source gas may
include zirconium (Zr), hafnium (Hf), aluminum (Al), tantalum (Ta),
titanium (Ti), lanthanum (La), strontium (Sr), Barium (Ba),
praseodymium (Pr), lead (Pb), and the like. These can be used alone
or in a combination thereof. The source gas may be supplied along
with a carrier gas into the process chamber 300. Example of the
carrier gas may include an inert gas such as argon (Ar).
[0063] The second gas supply section 420 may include an ozone
generator. The ozone generator may generate ozone using an oxygen
gas. That is, the oxidizing gas may be a gas mixture of ozone and
oxygen, and a concentration of ozone in the oxidizing gas may be in
range of about 100 to about 1000 g/m.sup.3. Particularly, a
concentration of ozone in the oxidizing gas may be in a range of
about 100 to about 500 g/m.sup.3. For example, a concentration of
ozone in the oxidizing gas may be about 200 g/m.sup.3.
[0064] The gas supply section 400 may further include a third gas
supply section 430 for supplying an inert gas used as a purge gas.
The inert gas may be used for adjusting an internal pressure of the
process chamber 300. For example, an interior of the process
chamber 300 may be primarily purged by a purge gas after forming
the metal precursor layer, and may be secondarily purged by a purge
gas after forming the metal oxide. An internal pressure of the
process chamber 300 may be maintained at a pressure in a range of
about 0.1 to about 10 Torr, and an inert gas may be supplied into
the process chamber 300 along with the source and/or the oxidizing
gas to adjust the internal pressure of the process chamber 300.
[0065] The gas supply section 400 may further include a fourth gas
supply section 440 for supplying an oxygen gas into the pressure
chamber 300 after primarily purging the interior of the process
chamber. The fourth gas supply section 440 is provided to form an
oxygen atmosphere in the process chamber 300 before oxidizing the
metal precursor layer using the oxidizing gas. Alternatively, the
oxygen gas may be supplied by the second gas supply section 420
instead of the fourth gas supply section 440.
[0066] The first, second, third and fourth gas supply sections 410,
420, 430 and 440 may be connected to the process chamber 300 by a
plurality of pipes. A first main pipe 450 and a second main pipe
452 may be connected to the process chamber 300. A first divergent
pipe 460 may diverge from the first main pipe 450, and the first
gas supply section 410 may be connected to the first main pipe 450
by the first divergent pipe 460. A second divergent pipe 462 may
diverge from the second main pipe 452, and the second gas supply
section 420 may be connected to the second main pipe 452 by the
second divergent pipe 462. A third divergent pipe 470 and a fourth
divergent pipe 472 may diverge from the first and second main pipes
450 and 452, respectively. The third gas supply section 430 may be
connected to the first and second main pipes 450 and 452 by the
third and fourth divergent pipes 470 and 472, respectively. A
fourth gas supply section 440 may be connected to the second main
pipe 452 by a connecting pipe 480.
[0067] Mass flow controllers 475 and valves 476 may be disposed in
the first, second, third and fourth divergent pipes 460, 462, 470
and 472 and the connecting pipe 480 to adjust flow rates of the
source gas, the oxidizing gas, the purge gas, the pressure
adjusting gas and the oxygen gas. To avoid unduly cluttering the
figure, only those mass flow controllers and valves on first pipe
460 are indicated.
[0068] The configuration including the pipes, the mass flow
controllers and the valves may be varied. Thus, the spirit and
scope of the present invention may be not limited by the connecting
relations between the pipes, the mass flow controller and the
valves.
[0069] Referring again to FIG. 1, the process chamber 300 and the
stage 200 may be received in an outer chamber 600. A first driving
section 700 for rotating the stage 200 and a second driving section
800 for vertically moving the stage 200 may be disposed beneath the
outer chamber 600.
[0070] The first driving section 700 may rotate the stage 200 in a
stepwise manner. That is, the first driving section 700 may rotate
the stage 200 by a predetermined angle to improve thickness
uniformity of the metal oxide layer while forming the metal oxide
layer. For example, the first driving section 700 may rotate the
stage 200 by a predetermined angle, for example, approximately
60.degree., 90.degree., 180.degree., etc, posterior to the
formation of the metal precursor layer, the primarily purging step,
the oxidation of the metal precursor layer and the secondarily
purging step. Then, the steps for forming metal oxide may be
repeatedly performed. That is, the steps for forming metal oxide
and the rotation of the stage 200 may be repeatedly performed
several times, thereby improving thickness uniformity of the metal
oxide layer.
[0071] In accordance with another example embodiment, the
semiconductor substrate 10 may be continuously rotated. The steps
for forming the metal oxide may be repeatedly performed while
continuously rotating the semiconductor substrate 10.
[0072] Further, the first driving section 700 may only rotate the
support region 210 of the stage 200 while repeatedly performing the
steps for forming the metal oxide.
[0073] The second driving section 800 may move the stage 200 in a
vertical direction to load or unload the semiconductor substrate
10.
[0074] Although not shown in figures, a plurality of lift pins may
be disposed in the outer chamber 600. Particularly, the lift pins
may be movably disposed in the vertical direction through the stage
200 to load or unload the semiconductor substrate 10. A gate valve
(not shown) may be disposed in a side wall of the outer chamber 600
to transfer the semiconductor substrate 10.
[0075] The exhauster 500 may be connected to the process chamber
300 to exhaust the source gas, the oxidizing gas and the
by-products formed while forming the metal oxide.
[0076] The exhauster 500 may include a high vacuum pump and a
roughing pump. The interior of the process chamber 300 may be
maintained at a pressure in a range of about 0.1 to about 10 Torr
by the exhauster 500 while forming the metal oxide.
[0077] FIG. 5 is an enlarged cross-sectional view illustrating the
RF electrode 350, and FIG. 6 is a plan view illustrating the RF
electrode 350.
[0078] Referring to FIGS. 2, 3, 5 and 6, the ceiling portion 320 of
the cover 310 may have a first connecting port 322 connected to the
first main pipe 450 for supplying the source gas, a second
connecting port 324 connected to the second main pipe 452 for
supplying the oxidizing gas and a third connecting port 326 for
communication with the exhauster 500.
[0079] A first channel 360 may be provided in an upper surface
portion of the RF electrode 350. The first channel 360 may be in
communication with the first connecting port 322 and may widen
towards the first outer surface 352 of the RF electrode 350. A
second channel 362 may be provided under the first channel 360 in
the RF electrode 350. The second channel 362 may be in
communication with the second connecting port 324 through a fourth
connecting port 364 that is formed in the RF electrode 350, and may
widen towards the first outer surface 352 of the RF electrode 350.
Further, a third channel 366 may be provided in the upper surface
portion of the RF electrode 350. The third channel 366 may be in
communication with the third connecting port 326 and may widen
towards the second outer surface 354 of the RF electrode 350. Each
of the first, second and third channels 360, 362 and 366 may be
fan-shaped as shown in FIG. 6.
[0080] As described above, because the first and second channels
360 and 362 widen towards the first outer surface 352 of the RF
electrode 350, the source gas and the oxidizing gas may be
uniformly supplied along the surface of the semiconductor substrate
10 and the surface of the metal precursor layer.
[0081] Referring again to FIG. 1, the RF electrode 350 may be
connected to a RF power source 900 to apply a RF power to the
oxidizing gas flowing along the surface of the metal precursor
layer. The RF power may be applied to accelerate the oxidation
reaction between the metal precursor layer and the oxidizing gas.
In case the RF power is applied to the oxidizing gas, the
concentration of ozone in the oxidizing gas may be increased, and a
concentration of oxygen radical in the oxidizing gas may be also
increased. As a result, the oxidation reaction between the metal
precursor layer and the oxidizing gas may be accelerated.
[0082] FIG. 7 is a flow chart illustrating a method of forming
metal oxide on the semiconductor substrate 10 using the apparatus
100 as shown in FIG. 1.
[0083] Referring to FIG. 7, in step S100, the semiconductor
substrate 10 such as a silicon wafer may be placed on the stage
200. Particularly, the semiconductor substrate 10 may be
transferred into an interior of the outer chamber 600 through the
gate valve of the outer chamber 600 and may be then loaded on the
stage 200 by the lift pins. Then, the second driving section 800
moves the stage 200 upwards so as to place the semiconductor
substrate 10 in the process chamber 300.
[0084] Patterns having electrical characteristics may be formed on
the semiconductor substrate 10. For example, active patterns that
are electrically isolated by the field oxide layer may be formed on
the surface of the semiconductor substrate 10. Further, the
semiconductor substrate 10 may have conductive structures that
serve as lower electrodes of capacitors and have a cylindrical
shape.
[0085] In step S200, a source gas including metal precursor may be
supplied into the process chamber 300 to form a metal precursor
layer on the semiconductor substrate 10. Here, the source gas may
be supplied to flow along the surface of the semiconductor
substrate 10 from the first gas supply section 410 through the
first channel 360 and the gas inlet port 302. Examples of metal
that may be used for the metal precursor may include zirconium
(Zr), hafnium (Hf), aluminum (Al), tantalum (Ta), titanium (Ti),
lanthanum (La), strontium (Sr), Barium (Ba), praseodymium (Pr),
lead (Pb), and the like. Examples of a source gas including
zirconium (Zr) may include tetrakis ethyl methyl amino zirconium
(TEMAZ; Zr[N(CH.sub.3)(C.sub.2H.sub.5)].sub.4), zirconium
tert-butoxide (Zr[OC(CH.sub.3).sub.3].sub.4), which may also be
referred to as Zr(O.sup.tBu).sub.4 or zirconium butyl oxide, and
the like. These may be used alone or in a combination thereof.
Examples of a source gas including hafnium (Hf) may include
tetrakis dimethyl amino hafnium (TDMAH; Hf[N(CH3)2]4), tetrakis
ethyl methyl amino hafnium (TEMAH; Hf[N(C2H5)CH3]4), tetrakis
diethyl amino hafnium (TDEAH; Hf[N(C2H5)2]4), hafnium tert-butoxide
(Hf[OC(CH.sub.3).sub.3].sub.4), Hf[OC(CH3)2CH2OCH3]4, and the like.
These may be used alone or in a combination thereof.
[0086] The source gas may be formed by forming a liquid metal
precursor into an aerosol mist using an atomizer and then
vaporizing the aerosol mist using a vaporizer. Alternatively, the
source gas may be formed by bubbling of a carrier gas into a liquid
metal precursor.
[0087] The metal precursor layer may be formed while the source gas
flows along the surface of the semiconductor substrate 10. The
metal precursor layer may be an atomic layer chemisorbed on the
surface of the semiconductor substrate 10. Further, the metal
precursor may be physisorbed on the chemisorbed metal precursor
layer, so that a second layer including the physisorbed metal
precursor may be formed.
[0088] In step S300, a purge gas may be supplied into the interior
of the process chamber 300. The purge gas may be supplied from the
third gas supply section 430 into the process chamber 300 through
the first and second channels 360 and 362 and the gas inlet port
302. The second layer may be removed from the chemisorbed metal
precursor layer by the supply of the purge gas and vacuum
evacuation of process chamber 300. Further, the source gas
remaining in the process chamber 300 may be also removed from the
process chamber 300 along with the purge gas by the vacuum
evacuation.
[0089] In step S400, an oxidizing gas including ozone may be
supplied into the process chamber 300 to oxidize the metal
precursor layer. The oxidizing gas may be supplied to flow along a
surface of the metal precursor layer from the second gas supply
section 420 through the second channel 362 and the gas inlet port
302.
[0090] In step S500, a RF power may be applied to accelerate an
oxidation reaction between the metal precursor layer and the
oxidizing gas. The RF power may be applied to the oxidizing gas
flowing along the surface of the metal precursor layer by the RF
electrode 350, which is connected to the RF power source 900. A
concentration of oxygen radical in the oxidizing gas may be
increased by applying the RF power, and the oxidation reaction
between the metal precursor layer and the oxidizing gas may be then
accelerated.
[0091] As a result, a metal oxide layer having improved electrical
characteristics may be formed on the semiconductor substrate 10.
Particularly, in case cylindrical lower electrodes having a high
aspect ratio are formed on a semiconductor substrate, the method of
forming metal oxide in accordance with the embodiments of the
present invention may be desirably employed.
[0092] Though sequentially performed in FIG. 7, the steps S400 and
S500 may be performed at the same time.
[0093] Further, step S350 may be performed prior to step S400. In
step S350, an oxygen gas may be supplied into the process chamber
300 to remove the purge gas from the process chamber 300 and to
form an oxygen atmosphere in the process chamber 300. For example,
the oxygen gas may be supplied from the fourth gas supply section
440 through the second channel 362 and the gas inlet port 302 for
about 0.1 to about 3 seconds.
[0094] In step S600, a purge gas may be supplied into the process
chamber 300. The purge gas may be supplied from the third gas
supply section 430 through the first and second channels 360 and
362 and the gas inlet port 302 into the process chamber 300. The
oxidizing gas and by-products remaining in the process chamber may
be removed along with the purge gas from the process chamber 300
through the outlet port 304 and the third channel 366.
[0095] While performing the steps S200 through S600, the
semiconductor substrate 10 may be heated to a predetermined process
temperature by the heater 230. For example, the semiconductor
substrate 10 may be maintained at a process temperature in a range
of room temperature to about 450.degree. C. Further, the interior
of the process chamber 300 may be maintained at a pressure in a
range of about 0.1 to about 10 Torr while performing the steps S200
through S600. For example, the interior of the process chamber 300
may be maintained at a pressure of about 3 Torr by a pressure
adjusting gas supplied from the third gas supply section 430 and
the operation of exhauster 500.
[0096] In step S700, the semiconductor substrate 10 may be rotated
by a predetermined angle. For example, the semiconductor substrate
10 may be rotated by the first driving section 700 by about
60.degree., 90.degree., 180.degree., etc.
[0097] In step S800, the steps S200 through S600 may be repeatedly
performed. The steps S700 and S800 may be repeatedly performed to
form a metal oxide layer having a desired thickness on the
semiconductor substrate 10. As a result, a metal oxide layer having
improved electrical characteristics and thickness uniformity may be
formed on the semiconductor substrate 10.
[0098] In accordance with another example embodiment of the present
invention, the semiconductor substrate 10 may be continuously
rotated while repeatedly performing the steps S200 through S600 at
a predetermined speed.
[0099] Experiments were performed to inspect electrical
characteristics of metal oxide layers formed by conventional
methods of forming metal oxide and methods of forming metal oxide
in accordance with example embodiments of the present
invention.
Comparative Example 1
[0100] A first hafnium oxide layer was formed on a semiconductor
substrate having cylindrical lower electrodes by a conventional
PEALD process using oxygen plasma. Particularly, a process
temperature was maintained at about 300.degree. C., and a pressure
in a process chamber was maintained at about 3 Torr while forming
the first hafnium oxide layer. Leakage currents through the first
hafnium oxide layer were measured at a left portion, a central
portion and a right portion of the semiconductor substrate.
Measured results were shown in FIG. 8.
Comparative Example 2
[0101] A second hafnium oxide layer was formed on a semiconductor
substrate having cylindrical lower electrodes by a convention ALD
process using an oxidizing gas including ozone. Particularly, a
process temperature was maintained at about 300.degree. C., and a
pressure in a process chamber was maintained at about 3 Torr while
forming the second hafnium oxide layer. Leakage currents through
the second hafnium oxide layer were measured at a left portion, a
central portion and a right portion of the semiconductor substrate.
Measured results were shown in FIG. 9.
[0102] An equivalent oxide thickness (EOT) of a central portion of
the first hafnium oxide layer was approximately 20.1 .ANG.. EOTs of
a left portion and a right portion of the first hafnium oxide layer
were approximately 19.1 .ANG. and approximately 19.6 .ANG.,
respectively.
[0103] An EOT of a central portion of the second hafnium oxide
layer was approximately 29.8 .ANG.. EOTs of a left portion and a
right portion of the second hafnium oxide layer were approximately
28.7 .ANG. and approximately 28.6 .ANG., respectively.
[0104] Referring to FIGS. 8 and 9, leakage current characteristics
of the first hafnium oxide layer were poor in comparison with those
of the second hafnium oxide layer. However, distribution of leakage
current of the second hafnium oxide layer was poor in comparison
with that of the first hafnium oxide layer.
Example 1
[0105] A third hafnium oxide layer was formed on a semiconductor
substrate having cylindrical lower electrodes by a method of
forming metal oxide in accordance with an embodiment of the present
invention.
[0106] An oxidizing gas having an ozone concentration of
approximately 200 g/m.sup.3 was used for forming the third hafnium
oxide layer, and a RF power of approximately 250 W was applied by
the RF electrode 350. Further, a temperature of the semiconductor
substrate was maintained at approximately 300.degree. C., and a
pressure in the process chamber 300 was maintained at approximately
3 Torr.
[0107] Leakage currents through the third hafnium oxide layer were
measured at a left portion, a central portion and a right portion
of the semiconductor substrate. Measured results were shown in FIG.
10.
[0108] An EOT of a central portion of the third hafnium oxide layer
was approximately 19.5 .ANG.. EOTs of a left portion and a right
portion of the third hafnium oxide layer were approximately 20.1
.ANG. and approximately 19.5 .ANG., respectively.
[0109] Referring to FIG. 10, it is understood that the EOTs of the
third hafnium oxide layer are similar to those of the first hafnium
oxide layer, and leakage current characteristics of the third
hafnium oxide layer are improved in comparison with those of the
first hafnium oxide layer.
[0110] It is difficult to directly compare the third hafnium oxide
layer with the second hafnium oxide layer, because the EOTs of the
second hafnium oxide layer are thicker than those of the third
hafnium oxide layer. However, it is understood that distribution of
leakage current of the third hafnium oxide layer is improved in
comparison with that of the second hafnium oxide layer as shown in
FIG. 10.
[0111] To directly compare the first, second and third hafnium
oxide layers, variations of leakage current according to variations
of electrical field (applied voltage/EOT) were measured. Measured
results were shown in FIG. 11.
[0112] Referring to FIG. 11, it is understood that the leakage
current characteristics of the third hafnium oxide layer are
improved in comparison with those of the second hafnium oxide
layer.
Example 2
[0113] A fourth hafnium oxide layer was formed on a semiconductor
substrate having cylindrical lower electrodes by a method of
forming metal oxide in accordance with an embodiment of the present
invention.
[0114] A RF power of approximately 100 W was applied by the RF
electrode 350, and an oxidizing gas including ozone was supplied at
a flow rate of approximately 100 sccm. Further, a temperature of
the semiconductor substrate was maintained at approximately
300.degree. C., and a pressure in the process chamber 300 was
maintained at approximately 3 Torr.
Example 3
[0115] A fifth hafnium oxide layer was formed on a semiconductor
substrate having cylindrical lower electrodes by a method of
forming metal oxide in accordance with still another embodiment of
the present invention.
[0116] A RF power of approximately 100 W was applied by the RF
electrode 350, and an oxidizing gas including ozone was supplied at
a flow rate of approximately 500 sccm. Further, a temperature of
the semiconductor substrate was maintained at approximately
300.degree. C., and a pressure in the process chamber 300 was
maintained at approximately 3 Torr.
Example 4
[0117] A sixth hafnium oxide layer was formed on a semiconductor
substrate having cylindrical lower electrodes by a method of
forming metal oxide in accordance with still another embodiment of
the present invention.
[0118] A RF power of approximately 250 W was applied by the RF
electrode 350, and an oxidizing gas including ozone was supplied at
a flow rate of approximately 100 sccm. Further, a temperature of
the semiconductor substrate was maintained at approximately
300.degree. C., and a pressure in the process chamber 300 was
maintained at approximately 3 Torr.
Example 5
[0119] A seventh hafnium oxide layer was formed on a semiconductor
substrate having cylindrical lower electrodes by a method of
forming metal oxide in accordance with still another embodiment of
the present invention.
[0120] A RF power of approximately 250 W was applied by the RF
electrode 350, and an oxidizing gas including ozone was supplied at
a flow rate of approximately 500 sccm. Further, a temperature of
the semiconductor substrate was maintained at approximately
300.degree. C., and a pressure in the process chamber 300 was
maintained at approximately 3 Torr.
[0121] Leakage currents through the fourth, fifth, sixth and
seventh hafnium oxide layers were measured, and measured results
were shown in FIG. 12.
[0122] EOTs of the fourth, fifth, sixth and seventh hafnium oxide
layers were approximately 17.5 .ANG., approximately 16.0 .ANG.,
approximately 15.2 .ANG., approximately 15.9 .ANG., respectively.
As shown in FIG. 12, it is understood that leakage current
characteristics are improved as both the applied RF power and the
flow rate of the oxidizing gas are increased.
[0123] As a result, it is understood that a metal oxide layer
having desired leakage current characteristics may be formed by
adjusting the RF power in a range of about 100 to about 300 W and
adjusting the flow rate in a range of about 100 to about 1000
sccm.
Example 6
[0124] A zirconium oxide layer was formed on a semiconductor
substrate having cylindrical lower electrodes which is formed in
accordance with a design rule of about 70 nm by a method of forming
metal oxide in accordance with another embodiment of the present
invention.
[0125] A RF power of approximately 250 W was applied by the RF
electrode 350, and an oxidizing gas including ozone was supplied at
a flow rate of approximately 500 sccm while forming the zirconium
oxide layer. Further, a temperature of the semiconductor substrate
was maintained at approximately 300.degree. C., and a pressure in
the process chamber 300 was maintained at approximately 3 Torr.
[0126] Leakage currents through the zirconium oxide layer were
measured at a central portion, a left portion and a right portion
of the semiconductor substrate, and measured results were shown in
FIG. 13.
[0127] EOTs at the central, left and right portions of the
zirconium oxide layer were approximately 8.4 .ANG., approximately
8.4 .ANG. and approximately 7.9 .ANG., respectively. As shown in
FIG. 13, it is understood that leakage current characteristics and
distribution of leakage current are improved when the applied
voltage is in a range of about .+-.1V.
[0128] In accordance with exemplary embodiments of the present
invention, an oxidation reaction between a metal precursor layer on
a semiconductor substrate and an oxidizing gas may be accelerated
by applying a RF power to the oxidizing gas. As a result, a metal
oxide layer formed by the accelerated oxidation reaction may have
improved electrical characteristics and thickness uniformity.
[0129] Although exemplary embodiments of the present invention have
been described, it is understood that other embodiments of the
present invention should not be limited to these exemplary
embodiments but various changes and modifications can be made by
those skilled in the art within the spirit and scope as hereinafter
claimed.
* * * * *