U.S. patent application number 11/706447 was filed with the patent office on 2007-06-28 for methods and apparatus for forming a high dielectric film and the dielectric film formed thereby.
This patent application is currently assigned to MICRON TECHNOLOGY, INC.. Invention is credited to Scott J. DeBoer, Randhir P.S. Thakur.
Application Number | 20070148990 11/706447 |
Document ID | / |
Family ID | 25197257 |
Filed Date | 2007-06-28 |
United States Patent
Application |
20070148990 |
Kind Code |
A1 |
DeBoer; Scott J. ; et
al. |
June 28, 2007 |
Methods and apparatus for forming a high dielectric film and the
dielectric film formed thereby
Abstract
A method of forming a high dielectric oxide film conventionally
formed using a post formation oxygen anneal to reduce the leakage
current of such film includes forming a high dielectric oxide film
on a surface. The high dielectric oxide film has a dielectric
constant greater than about 4 and includes a plurality of oxygen
vacancies present during the formation of the film. The high
dielectric oxide film is exposed during the formation thereof to an
amount of atomic oxygen sufficient for reducing the number of
oxygen vacancies and eliminating the post formation oxygen anneal
of the high dielectric oxide film. Further, the amount of atomic
oxygen used in the formation method may be controlled as a function
of the amount of oxygen incorporated into the high dielectric oxide
film during the formation thereof or be controlled as a function of
the concentration of atomic oxygen in a process chamber in which
the high dielectric oxide film is being formed. An apparatus for
forming the high dielectric oxide film is also described.
Inventors: |
DeBoer; Scott J.; (Boise,
ID) ; Thakur; Randhir P.S.; (Boise, ID) |
Correspondence
Address: |
MUETING, RAASCH & GEBHARDT, P.A.
P.O. BOX 581415
MINNEAPOLIS
MN
55458
US
|
Assignee: |
MICRON TECHNOLOGY, INC.
Boise
ID
|
Family ID: |
25197257 |
Appl. No.: |
11/706447 |
Filed: |
February 15, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
10213812 |
Aug 7, 2002 |
7192889 |
|
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11706447 |
Feb 15, 2007 |
|
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08807831 |
Feb 27, 1997 |
6461982 |
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10213812 |
Aug 7, 2002 |
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Current U.S.
Class: |
438/778 ;
257/E21.271; 257/E21.272; 257/E29.164; 257/E29.343; 438/240; 438/3;
438/785 |
Current CPC
Class: |
H01L 28/40 20130101;
H01L 29/516 20130101; H01L 21/31691 20130101; H01L 21/02274
20130101; C23C 16/52 20130101; H01L 21/02356 20130101; H01L 21/316
20130101; H01L 21/02183 20130101; C23C 16/40 20130101 |
Class at
Publication: |
438/778 ;
438/785; 438/003; 438/240 |
International
Class: |
H01L 21/31 20060101
H01L021/31 |
Claims
1-60. (canceled)
61. A method of forming a dielectric film in the fabrication of
semiconductor devices, the method comprising: providing atomic
oxygen in a process chamber for use in deposition of a high
dielectric oxide film on a surface, the high dielectric oxide film
having a dielectric constant greater than about 4; providing a
vaporized precursor in the process chamber with the atomic oxygen
for use during the deposition of the high dielectric oxide film;
depositing the high dielectric oxide film using the atomic oxygen
and the vaporized precursor provided in the process chamber;
detecting an amount of oxygen incorporated into the high dielectric
oxide film during the deposition thereof using spectroscopy; and
controlling the amount of atomic oxygen in the process chamber as a
function of the detected amount of atomic oxygen incorporated into
the high dielectric oxide film.
62. The method of claim 61, wherein detecting an amount of oxygen
incorporated into the high dielectric oxide film during the
deposition thereof using spectroscopy comprises using spectroscopic
ellipsometry to detect the amount of oxygen incorporated into the
high dielectric oxide film during the deposition of the high
dielectric oxide film.
63. The method of claim 61, wherein detecting an amount of oxygen
incorporated into the high dielectric oxide film during the
deposition thereof using spectroscopy comprises using Raman
spectroscopy to detect the amount of oxygen incorporated into the
high dielectric oxide film during the deposition of the high
dielectric oxide film.
64. The method of claim 61, wherein controlling the amount of
atomic oxygen in the process chamber as a function of the detected
amount of atomic oxygen incorporated into the high dielectric oxide
film comprises generating a command based on the detected amount of
oxygen incorporated into the high dielectric oxide film for use in
control of a flow controller operable to increase or decrease the
atomic oxygen in the process chamber.
65. The method of claim 61, wherein providing atomic oxygen
comprises: providing at least one of O.sub.2, O.sub.3, NO, and
N.sub.2O; and generating an oxygen plasma remote from the process
chamber from the at least one of O.sub.2, O.sub.3, NO, and
N.sub.2O.
66. The method of claim 61, wherein providing atomic oxygen
comprises: providing at least one of O.sub.2, O.sub.3, NO, and
N.sub.2O; and generating an oxygen plasma in the process chamber
used for deposition of the high dielectric oxide film from the at
least one of O.sub.2, O.sub.3, NO, and N.sub.2O.
67. The method of claim 61, wherein the high dielectric oxide film
comprises at least one of Ta.sub.2O.sub.5,
Ba.sub.xSr.sub.1-xTiO.sub.3, Y.sub.2O.sub.3, TiO.sub.2, HfO.sub.2,
PZT, PLZT, and SBT.
68. The method of claim 61, wherein the high dielectric oxide film
comprises a Ta.sub.2O.sub.5 film.
69. The method of claim 68, wherein providing the vaporized
precursor in the process chamber comprises providing a vaporized
tantalum precursor in the process chamber with the atomic oxygen
for use during the deposition of the Ta.sub.2O.sub.5 film, wherein
providing the vaporized tantalum precursor comprises vaporization
of a carbon-free solid precursor.
Description
FIELD OF THE INVENTION
[0001] The present invention pertains to high dielectric constant
films. More particularly, the present invention relates to methods
and apparatus for forming high dielectric constant films utilizing
the incorporation of atomic oxygen during the formation of such
films.
BACKGROUND OF THE INVENTION
[0002] Various dielectric films have been formed in the past during
the fabrication of semiconductor devices. For example, films such
as silicon dioxide and silicon nitride have been used for
dielectric films in the formation of capacitors, such as for memory
devices, including dynamic random access memories and static random
access memories. Such films typically have small leakage currents
associated therewith.
[0003] With the shrinkage of minimum feature sizes of semiconductor
devices, the requirement of providing high capacitance with thinner
films is becoming apparent. As the dielectric constant of silicon
dioxide and silicon nitride are relatively low, the need for
utilizing higher dielectric constant films, such as tantalum
pentoxide (Ta.sub.2O.sub.5), strontium titanate oxide
(SrTiO.sub.3), and barium strontium titanate
(Ba.sub.xSr.sub.1-xTiO.sub.3) arises. Such high dielectric films
provide the ability to achieve a larger capacitance value in a
smaller area, i.e., with a thinner dielectric film.
[0004] However, conventional deposition processes for forming such
high dielectric constant films result in films having leakage
current levels that are unacceptable for semiconductor devices
being fabricated. As described in the article entitled, "Leakage
Current Mechanisms of Amorphous and Polycrystalline Ta.sub.2O.sub.5
Films Grown by Chemical Vapor Deposition," by Aoyama et al., J.
Electrochem. Soc., Vol. 143, No. 3, March 1996, various treatments
have been carried out after Ta.sub.2O.sub.5 film deposition to
reduce the leakage current thereof. For example, such treatments
described included dry O.sub.2 treatment, dry O.sub.3 treatment,
O.sub.2 treatment with utilization of ultraviolet exposure, O.sub.3
treatment with use of ultraviolet exposure, and N.sub.2O plasma
treatment. The results from the paper indicate that the presence of
impurities, such as carbon and hydrogen, remaining in the
Ta.sub.2O.sub.5 film leads to generally high leakage current and
that oxidation of such impurities results in the reduction of the
leakage current. However, post-deposition oxidation of such
impurities results in a fabrication step generally not applicable
to other dielectric films such as silicon dioxide and silicon
nitride. Such post-deposition oxidation of high dielectric films,
hereinafter referred to generally as post-deposition oxygen anneal,
in addition to reducing throughput of devices also increases the
thermal budget for fabrication of the devices.
[0005] Therefore, there is a need in the art for high dielectric
oxide film formation methods and apparatus for forming high
dielectric films, reducing throughput of devices by eliminating
steps in the deposition process. The present invention provides
such methods and apparatus for overcoming the problems as described
above and other problems that will be readily apparent to one
skilled in the art from the description of the present invention
below.
SUMMARY OF THE INVENTION
[0006] A method of forming a high dielectric oxide film
conventionally formed using a post-formation oxygen anneal to
reduce the leakage current of such film is described. The method in
accordance with the present invention includes forming a high
dielectric oxide film on a surface. The high dielectric oxide film
has a dielectric constant greater than about 4. The high dielectric
oxide film includes a plurality of oxygen vacancies as the film is
formed. The high dielectric oxide film is exposed to an amount of
atomic oxygen during formation thereof sufficient for reducing the
number of oxygen vacancies and eliminating the post-formation
oxygen anneal of the formed high dielectric oxide film.
[0007] In one embodiment of the method, the amount of atomic oxygen
to which the high dielectric oxide film is exposed during formation
thereof is controlled as a function of the amount of oxygen
incorporated into the high dielectric oxide film. In another
embodiment of the method, the amount of atomic oxygen is controlled
as a function of the concentration of atomic oxygen in a process
chamber used for formation of the high dielectric oxide film.
[0008] In other embodiments of the method, the atomic oxygen is
provided by at least one of O.sub.3, NO, and N.sub.2O. Further, the
atomic oxygen may be provided by generation of a plasma from at
least one of O.sub.3, NO, N.sub.2O, or O.sub.2. Ionized atomic
oxygen generated by the plasma may be attracted to the surface for
incorporation in the high dielectric oxide film by biasing the
surface. Further, the plasma may be generated remotely of the
surface upon which the high dielectric film is formed or in
proximity to the surface.
[0009] In other embodiments of the method, the high dielectric film
may include Ta.sub.2O.sub.5, Ba.sub.xSr.sub.1-xTiO.sub.3,
Y.sub.2O.sub.3, TiO.sub.2, HfO.sub.2, PZT, PLZT, or SBT. Further,
the atomic oxygen utilized for exposing the high dielectric oxide
film may be exposed to a heat source.
[0010] In another method of forming a dielectric film in the
fabrication of semiconductor devices, an amount of atomic oxygen
for use in the formation of the film on a surface is provided. The
high dielectric oxide film has a dielectric constant greater than
about 4. A vaporized precursor is also provided for use in the
formation of the film. The high dielectric oxide film is then
formed using the atomic oxygen and the vaporized precursor. The
amount of atomic oxygen is controlled as a function of the amount
of atomic oxygen necessary to reduce the leakage current levels to
below a predetermined level.
[0011] In another method of forming a dielectric film in the
fabrication of semiconductor devices, atomic oxygen is provided for
use in the formation of a Ta.sub.2O.sub.5 film on a surface. A
vaporized tantalum precursor is also provided for forming the film.
The Ta.sub.2O.sub.5 film is formed using the atomic oxygen and the
vaporized tantalum precursor while simultaneously performing an in
situ oxygen anneal of the film. In one embodiment of this method,
the precursor is a carbon-free solid precursor.
[0012] An apparatus for forming a high dielectric oxide film in
accordance with the present invention is also described. The
apparatus includes a controllable atomic oxygen source and a
vaporized precursor source. A deposition chamber for receiving the
atomic oxygen from the atomic oxygen source and vaporized precursor
from the vaporized precursor source is utilized for locating a
structure therein for deposition of the high dielectric oxide film
on a surface thereof. The high dielectric oxide film has a
dielectric constant greater than about 4. The apparatus further
includes a detection mechanism for detecting a characteristic of
the deposition of the high dielectric oxide film on the surface of
the structure. The controllable atomic oxygen source is controlled
as a function of the detected characteristic.
[0013] Further, in accordance with the present invention, a high
dielectric oxide film is provided. The high dielectric oxide film
includes one of Ta.sub.2O.sub.5, Ba.sub.xSr.sub.1-xTiO.sub.3,
Y.sub.2O.sub.3, TiO.sub.2, HfO.sub.2, PZT, PLZT, and SBT. The
dielectric film is formed by depositing the high dielectric oxide
film on a surface while exposing the high dielectric oxide film
during formation thereof to a concentration of atomic oxygen
sufficient for reducing oxygen vacancies therein and sufficient to
eliminate a post-formation oxygen anneal of the high dielectric
oxide film. In one embodiment of the high dielectric oxide film,
the film is deposited on an electrode of a capacitor in a
semiconductor memory device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a general illustration of a portion of a device
structure including a high dielectric oxide film formed in
accordance with the present invention.
[0015] FIG. 2 is a block illustration of an apparatus for use in
depositing high dielectric oxide films in accordance with the
present invention.
[0016] FIG. 3 is a block illustration of an alternate configuration
of the apparatus of FIG. 2 in accordance with the present
invention.
[0017] FIG. 4 is a block illustration of an alternate configuration
of the apparatus of FIG. 2 in accordance with the present
invention.
[0018] FIG. 5 is an alternate configuration of the apparatus as
shown in FIG. 2, further including a detection and control
mechanism in accordance with the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0019] The present invention shall be described with reference to
FIGS. 1 and 2. Thereafter, additional embodiments of the present
invention shall be further described with reference to FIGS.
3-5.
[0020] FIG. 1 is an illustration of a portion 10 of a device
structure, such as a portion of a capacitor, gate dielectric, or
other device structure, which includes a high dielectric film 14.
For example, the device structure may be a portion of a memory
device, such as a dynamic random access memory. As shown in FIG. 1,
the portion 10 includes a layer or film 12 of the device structure
10 having a surface 16. The layer or film 12 can be any material
utilized in the fabrication of semiconductor devices. For example,
if the device structure is a random access memory and the portion
10 is part of a capacitor, the layer 12 is an electrode. Such an
electrode may be either a smooth or a rugged electrode and,
further, the electrode may be of any conducting material, such as a
metal, a semiconductor, a semi-metal, or any combination thereof,
i.e., a stack containing one or more such electrode materials. For
example, Ta.sub.2O.sub.5 deposition using a TaF.sub.5 precursor may
be formed on polysilicon, crystalline silicon, hemispherical grain
polysilicon, germanium, or silicon-germanium, WSi.sub.x, or TiN.
Such electrodes may be treated by rapid thermal anneal in an oxygen
and/or nitrogen atmosphere. After formation of the high dielectric
film, a top electrode is formed as part of the capacitor as known
to one skilled in the art. Further, for example, if the portion 10
of the device structure is representative of a gate region, the
layer or film 12 may be representative of a semiconductor
substrate, such as silicon. Semiconductor substrate refers to the
base semiconductor layer, e.g., the lowest layer of silicon
material on a wafer or a silicon layer deposited on another
material such as silicon on sapphire. The term "semiconductor
substrate assembly" refers to a part of a device structure
including a semiconductor substrate having one or more layers,
films or structures formed thereon.
[0021] The portion 10 of the device structure further includes a
high dielectric oxide film 14 formed on surface 16 of the layer or
film 12 in accordance with the present invention. The high
dielectric oxide film 14 may include any film having a dielectric
constant (e) greater than about 4. For example, the high dielectric
oxide film 14 may be Ta.sub.2O.sub.5, Ba.sub.xSr.sub.1-xTiO.sub.3,
SrTiO.sub.3, Y.sub.2O.sub.3, TiO.sub.2, HfO.sub.2, PZT (lead
zirconate titanate), PLZT (lanthanum-doped lead zirconate
titanate), SBT (strontium bismuth titanate), BST (barium strontium
titanate), or any other high dielectric oxide film formed with a
low oxygen content such that oxygen vacancies therein are present
when such films are formed utilizing conventional formation
methods. For example, such conventional formation methods include
high dielectric formation methods using O.sub.2 as a source gas and
many of which require post-deposition anneals in an oxygen ambient
in order to eliminate or reduce these vacancies. Such oxygen
vacancies using current deposition methods result in higher than
normal leakage current levels for such high dielectric oxide films.
For example, such oxygen vacancies are a result of the impurities
carbon and hydrogen remaining in the film after deposition
thereof.
[0022] The high dielectric oxide film 14 formed in accordance with
the present invention eliminates the oxygen vacancies during the
formation of the high dielectric oxide film 14. In other words, the
film 14 undergoes an in situ oxygen anneal simultaneously with the
formation of the film. Atomic oxygen is utilized during formation
of the high dielectric oxide film to fill the oxygen vacancies as
the film is formed. Such elimination of the oxygen vacancies
produces a high dielectric oxide film which is more stoichiometric
and impurity-free and therefore has lower leakage current levels.
Excess atomic oxygen is incorporated into the high dielectric oxide
film during formation thereof through the use of atomic oxygen
containing sources such as O.sub.3, N.sub.2O, NO, as well as atomic
oxygen provided in other manners as described below. The atomic
oxygen is incorporated into the film in a concentration sufficient
to eliminate the need for post-formation oxygen anneals, as
typically required in conventional deposition of such high
dielectric oxide films. By eliminating or reducing the need for
post-formation oxygen anneals through the use of an in situ oxygen
anneal in accordance with the present invention, throughput is
increased and a reduced thermal budget is achieved.
[0023] In addition, the high dielectric oxide film 14 may be part
of a stack of other dielectric films, i.e., a stack of one or more
of Ta.sub.2O.sub.5, TiO.sub.2, or Si.sub.3N.sub.4. In such a
configuration, an anneal of all the layers may still be necessary
to reduce the leakage current depending upon the films utilized in
such a stack.
[0024] Although the present invention is particularly described
with respect to the formation of a Ta.sub.2O.sub.5 high dielectric
oxide film, other high dielectric constant oxide films have similar
leakage current level problems. The present invention is therefore
beneficial not only for the Ta.sub.2O.sub.5 film, but for any other
such high dielectric oxide film having oxygen vacancies or low
oxygen content when formed in conventional manners. Therefore, the
present invention is not limited to the Ta.sub.2O.sub.5 film but is
limited only in accordance with the present invention as described
in the accompanying claims.
[0025] The method of forming the high dielectric oxide film 14 in
accordance with the present invention shall be described with
reference to the apparatus 20 shown in FIG. 2. Apparatus 20
includes process chamber 22 and a device structure 15 located
therein on device structure holder 17. The process chamber 22
further includes vacuum pump 24 for evacuating the chamber and a
heat source 26, such as an ultraviolet (UV) or microwave radiation
source directed into the process chamber 22 for use in providing
atomic oxygen using ozone, i.e., for example. UV ozone treatment.
The process chamber 22 may be any conventional chamber utilized for
the formation of films in the fabrication of semiconductor devices.
For example, the process chamber 22 is representative of various
CVD process chambers including, but not limited to, hot wall or
cold wall reactors, atmospheric or reduced pressure reactors, as
well as plasma enhanced reactors. Therefore, the present invention
contemplates deposition of the films in accordance with the present
invention utilizing low pressure CVD (LPCVD), physical vapor
deposition (PVD), plasma enhanced CVD (PECVD), and reduced thermal
CVD (RTCVD). Further, the present invention may be applicable or
used with other sputtering processes for forming high dielectric
oxide films.
[0026] Apparatus 20 for depositing the high dielectric oxide film
14 further includes controllable atomic oxygen source 27 and
controllable vaporized precursor source 29. Controllable atomic
oxygen source 27 includes atomic oxygen source 28 and a mass flow
controller 32. The mass flow controller 32 may be any commercially
available flow controller utilized for controlling a gas flow. The
mass flow controller 32 controls the flow of atomic oxygen from
atomic oxygen source 28 via gas line 40 into the process chamber
22. Atomic oxygen source 28 may include any atomic oxygen
containing source, such as O.sub.3, N.sub.2O, NO, or any
combination thereof.
[0027] The controllable vaporized precursor source 29, at least in
the embodiment shown in FIG. 2, includes carrier gas source 30,
mass flow controller 34, and precursor source 36. The mass flow
controller 34, which may be any flow controller for controlling gas
flow, is utilized to control the flow of an inert gas such as, for
example, Ar, N.sub.2, He, H.sub.2, N.sub.2O, NO, provided from
carrier gas source 30. The carrier gas utilized is used to generate
and/or move vaporized precursor from precursor source 36 through
gas line 42 into the process chamber 22.
[0028] Although the controlled vaporized precursor source 29 is
shown to include carrier gas source 30, mass flow controller 34,
and precursor source 36, the controllable vaporized precursor
source 29 may be of any configuration suitable for providing one or
more vaporized precursors for formation of the desired high
dielectric oxide film into process chamber 22. For example, the
controlled vaporized precursor source 29 may include a liquid
source or a solid source vaporized in any particular manner
including, but in no manner limited to, solid sublimation, bubbler
delivery, flash vaporization of solid particles or
microdroplets.
[0029] For example, solid precursors utilized may include
TaF.sub.5, TaCl.sub.5, or other tantalum halides for depositing
Ta.sub.2O.sub.5. Other nonorganic solid precursors are also
available for forming BST, PZT, PLZT, etc. Liquid precursors
utilized may include Ta(OC.sub.2H.sub.5).sub.5 or any other
organometallic liquids containing tantalum for forming
Ta.sub.2O.sub.5. However, any vaporized precursor suitable for use
in forming the desired high dielectric film 14 in process chamber
22 may be utilized.
[0030] In accordance with the present invention, the controllable
atomic oxygen source 27 provides an excess of atomic oxygen during
formation of the high dielectric oxide film typically having oxygen
vacancies and higher leakage current levels. As such, the high
dielectric oxide film 14 is then formed with oxygen vacancies being
filled as the high dielectric oxide film 14 is formed. The
concentration or amount of atomic oxygen necessary in the process
chamber 22 depends upon the type of high dielectric film 14 being
formed.
[0031] One skilled in the art will recognize that the deposition
process may be performed in either single wafer or batch type
systems. Further, it should be apparent that the deposition process
may be clustered with an in situ preclean and/or a post deposition
conditioning chamber, i.e., for example, ultraviolet ozone
conditioning, O.sub.3 plasma conditioning, dry oxidation in
O.sub.2, O.sub.3, N.sub.2O, or NO conditioning.
[0032] As one illustrative embodiment of the present invention, the
apparatus 20 may be similar to the cold wall type LPCVD apparatus
as described in the article entitled, "Leakage Current Mechanisms
of Amorphous and Polycrystalline Ta.sub.2O.sub.5 Films Grown by
Chemical Vapor Deposition," by Aoyama et al., J. Electrochem. Soc.,
Vol. 143, No. 3, March 1996 which is incorporated in its entirety
herein by reference thereto. The controllable atomic oxygen source
27 may include any of the oxygen containing species described above
or any combination thereof. The controllable vaporized precursor
source 29 may, for example, in the deposition of a Ta.sub.2O.sub.5
film include a liquid precursor source 36 of
Ta(OC.sub.2H.sub.5).sub.5 with the mass flow controller 34
controlling an argon carrier gas for bubbling through the liquid
precursor source 36 providing a vaporized precursor or reactant gas
for deposition of Ta.sub.2O.sub.5 utilizing the process chamber 22.
For example, argon gas is introduced into the
Ta(OC.sub.2H.sub.5).sub.5 liquid maintained at about 160.degree. C.
The atomic oxygen and the Ta(OC.sub.2H.sub.5).sub.5 with argon
carrier are then introduced simultaneously into the reaction
chamber through gas lines which are heated to 180.degree. C. In the
cold wall chamber, the substrate is heated to, for example,
400.degree. C. and the film formed may be amorphous, crystalline,
or polycrystalline depending upon other parameters of the
deposition apparatus. For example, temperature and pressure changes
may produce an amorphous film as opposed to a partially crystalline
or crystalline film. The present invention is in no manner limited
to any particular structural configuration for the film, such as
amorphous or polycrystalline, but is limited only in accordance
with the present claims. Further, various pressures, temperatures,
and other deposition process parameters may be utilized to generate
the desired film in accordance with the present invention and the
present invention is not limited to any particular process
parameters.
[0033] Ta.sub.2O.sub.5 films are typically deposited by LPCVD or
PECVD using an organometallic precursor such as the
Ta(OC.sub.2H.sub.5).sub.5 which has a fairly low vapor pressure of
about 200 mTorr at 85.degree. C. The LPCVD process leads to
extremely good step coverage and makes the process viable for
memory cell dielectric formation. However, during this process a
large amount of carbon is incorporated into the dielectric film.
The carbon comes from the precursor and results in higher leakage
currents for the films conventionally deposited. In situ
incorporation of atomic oxygen during the formation of the
dielectric film as described above reduces the leakage current.
However, to further provide additional advantage by lowering the
carbon level and still providing excellent step coverage, the
combination of a solid carbon-free or nonorganic precursor, with in
situ incorporation of atomic oxygen, is utilized as described
below.
[0034] For example, in the deposition of Ta.sub.2O.sub.5, a LPCVD
process can be performed utilizing a solid carbon-free precursor
such as TaF.sub.5, TaCl.sub.5, or other tantalum halides along with
atomic oxygen incorporation as described herein. The LPCVD process
may be performed at a deposition pressure of about 25 mTorr to
about 10 Torr and at a temperature of about 250.degree. C. to about
700.degree. C. The solid precursor can be vaporized and provided to
the deposition chamber in various manners, such as for example,
heating a TaF.sub.5 solid source to greater than about 70.degree.
C. and then transferring the vaporized precursor to the deposition
chamber using a carrier gas such as, for example, Ar, N.sub.2, He,
H.sub.2, N.sub.2O, or NO. The atomic oxygen, or oxygen source, can
then be provided using O.sub.3, N.sub.2O, NO, O.sub.2 or any
combination thereof and in any manner described herein.
[0035] FIG. 3 is an alternate configuration of an apparatus 50 for
forming the high dielectric oxide film 14 in accordance with the
present invention. The apparatus 50 includes substantially the same
elements or components as the apparatus 20 described with reference
to FIG. 2. However, the controlled atomic oxygen source 27 is
replaced with controlled atomic oxygen source 51. The controlled
atomic oxygen source 51 includes an oxygen source 52, a mass flow
controller 54, and an oxygen plasma generator 56. In this
particular configuration, the atomic oxygen is provided to the
process chamber from the oxygen plasma generator 56. The oxygen
plasma generator 56 functions as an atomic oxygen source by
generating a plasma from the oxygen containing source 52. The
oxygen plasma generator 56 may be remote from the process chamber
22 as shown in FIG. 3, or may be such as to provide a plasma in
proximity to the device structure 15, i.e., in the process chamber
with the wafer.
[0036] Oxygen source 52 may include O.sub.3, N.sub.2O, NO, O.sub.2
or any combination thereof. The oxygen containing source 52 is
provided to the oxygen plasma generator 56 by any commercially
available mass flow controller 54. For example, an oxygen plasma
may be generated utilizing an O.sub.2 source provided to a 13.56
MHz RF generator at a pressure of 0.3 torr, a temperature of
400.degree. C., and an RF power of 0.35 W/cm.sup.2. It should be
readily apparent that the parameters for the oxygen plasma
generator are dependent upon the oxygen containing source utilized
and the amount of atomic oxygen to be delivered to the process
chamber. Various pressures, temperatures, power levels and
generators may be utilized to generate the oxygen plasma and the
present invention is not limited to any particular configuration
for generating the oxygen plasma.
[0037] Also shown in FIG. 3 is a power source 59 for biasing the
device structure 15 on device structure holder 17. With bias
applied to the device structure 15, ionized atomic oxygen generated
by the plasma generator 56 is attracted thereto and oxygen
vacancies in the high dielectric oxide film 14 are filled more
quickly by the ionized atomic oxygen provided in the process
chamber 22. For example, but in no manner limited to the present
invention, the power source may be .+-.50 volts DC.
[0038] It would be readily apparent to one skilled in the art that
a combination of a plasma source 51 such as shown in FIG. 3 and an
atomic oxygen source 29 such as shown in FIG. 2 may be used in
combination to provide the necessary atomic oxygen in the process
chamber 22.
[0039] Another alternate configuration of an apparatus 60 for
forming the high dielectric oxide film 14 shall be described with
reference to FIG. 4. FIG. 4 is substantially equivalent to the
apparatus 20 as shown in FIG. 2. However, the apparatus 60 further
includes a premixer unit 64 such that the vaporized precursor and
the atomic oxygen provided by the controlled atomic oxygen source
27 and the controlled vaporized precursor source 29 are premixed in
the premixer unit 64 prior to transfer into the process chamber 22.
In such a manner, the atomic oxygen may be more evenly distributed
in the vaporized precursor such that a more efficient filling of
the oxygen vacancies typically contained in the high dielectric
oxide film 14 are filled. It should be readily apparent that the
premixer 64 may also be utilized with the atomic oxygen provided
from the oxygen plasma generator 56 in the alternate configuration
shown in FIG. 3.
[0040] FIG. 5 shows the apparatus 20 for forming the high
dielectric oxide film 14 in accordance with the present invention
and, in addition, a block illustration of a detection and control
apparatus 90 for maintaining a desired atomic oxygen concentration
in the processing chamber 22. The detection and control apparatus
90 includes a detection device 92 and a controller 94.
[0041] The controller 94 may be any controller apparatus, such as a
processing unit and software associated therewith, or a control
logic circuit for generating a command output to the controlled
atomic oxygen source 27 for controlling the concentration of atomic
oxygen in processing chamber 22. The command output to the
controlled atomic oxygen source 27 is generated by the controller
94 in response to a signal generated by detection device 92 based
on a characteristic of the formation process of the high dielectric
oxide film 14. The controller 94 is in no manner limited to any
processor, any particular logic or software, or any particular
configuration but is limited only as defined in the accompanying
claims.
[0042] Detection device 92 may be any apparatus for sensing a
parameter of a high dielectric film formation process
characteristic of the filling of oxygen vacancies within the high
dielectric oxide film 14 being formed. For example, detection
device 92 may be for detecting the concentration of atomic oxygen
in the processing chamber 22. Further, for example, the detection
device 92 may be for detecting the amount of oxygen incorporated in
the high dielectric oxide film 14, and thus representative of the
number of vacancies within the film filled so as to reduce the
leakage current of the film 14.
[0043] The detection and control apparatus 90, for example, may be
any apparatus for performing ellipsometry utilizing a light source
directed at the surface of the device structure 15 and a detector
for detecting the reflected light therefrom. The reflected light is
utilized to determine the amount of oxygen incorporated in the high
dielectric oxide film being formed. As a function of the detected
reflective light, the controller 94 with the appropriate
spectroscopic software can determine the oxygen content and
generate a command for control of, for example, the mass flow
controller 32 in order to increase or decrease the atomic oxygen in
the processing chamber 22.
[0044] Further, for example, the detection and control apparatus 90
may include an apparatus for performing Raman spectroscopy which
may be utilized to determine the amount of oxygen incorporated in
the high dielectric oxide film 14 and further utilized to determine
the structure of the film, i.e., whether the film is amorphous or
crystalline. With use of the detected scattered light and the
appropriate Raman spectroscopy software, a command signal may be
generated to control the atomic oxygen as previously described or,
further, may be utilized to control any other parameter of the
apparatus 20 such that the structure of the film is controlled as
oxygen vacancies in the film are filled.
[0045] In a further example, the concentration of the atomic oxygen
in the processing chamber may be detected as opposed to the oxygen
in the high dielectric oxide film 14. For example, a commercially
available residual gas analyzer may be utilized. Such an analyzer
typically includes a light source for generating light for
impingement on the materials in the process chamber 22. A detector
of the analyzer may then detect the scattered light and provide an
output signal which can be analyzed by the appropriate
spectroscopic software to determine oxygen concentration in the
processing chamber 22. The controlled atomic oxygen source 27 may
then be controlled as a function of the amount of atomic oxygen
detected in the processing chamber 22.
[0046] It would be readily apparent to one skilled in the art that
detection and control apparatus 90 may include any of the devices
described above or a combination thereof. Further, other
spectroscopic detection devices or gas analysis devices typically
utilized for detecting concentrations and structures in films and
in sample containers may be utilized in conjunction with the
present invention. The present invention is not limited to those
listed herein, but is limited only as described in the accompanying
claims.
[0047] Although the present invention has been described with
particular reference to various embodiments thereof, variations and
modifications of the present invention can be made within a
contemplated scope of the following claims, as is readily known to
one skilled in the art.
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