U.S. patent application number 11/494947 was filed with the patent office on 2006-11-30 for systems and methods for forming metal-containing layers using vapor deposition processes.
This patent application is currently assigned to Micron Technology, Inc.. Invention is credited to Dan B. Millward.
Application Number | 20060270223 11/494947 |
Document ID | / |
Family ID | 35800515 |
Filed Date | 2006-11-30 |
United States Patent
Application |
20060270223 |
Kind Code |
A1 |
Millward; Dan B. |
November 30, 2006 |
Systems and methods for forming metal-containing layers using vapor
deposition processes
Abstract
A method of forming (and an apparatus for forming) a metal
containing layer on a substrate, particularly a semiconductor
substrate or substrate assembly for use in manufacturing a
semiconductor or memory device structure, using one or more
homoleptic and/or heteroleptic precursor compounds that include,
for example, guanidinate, phosphoguanidinate, isoureate,
thioisoureate, and/or selenoisoureate ligands using a vapor
deposition process is provided.
Inventors: |
Millward; Dan B.; (Kuna,
ID) |
Correspondence
Address: |
MUETING, RAASCH & GEBHARDT, P.A.
P.O. BOX 581415
MINNEAPOLIS
MN
55458
US
|
Assignee: |
Micron Technology, Inc.
Boise
ID
|
Family ID: |
35800515 |
Appl. No.: |
11/494947 |
Filed: |
July 28, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10918308 |
Aug 13, 2004 |
|
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11494947 |
Jul 28, 2006 |
|
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Current U.S.
Class: |
438/681 ;
257/E21.171 |
Current CPC
Class: |
H01L 21/28562 20130101;
C23C 16/34 20130101; C23C 16/40 20130101; C23C 16/308 20130101 |
Class at
Publication: |
438/681 |
International
Class: |
H01L 21/44 20060101
H01L021/44 |
Claims
1-55. (canceled)
56. A vapor deposition apparatus comprising: a deposition chamber
having a substrate positioned therein; and at least one vessel
comprising at least one precursor compound of the formula (Formula
I): ##STR10## wherein: M is selected from the group consisting of a
Group 2 to Group 15 metal, a lanthanide, an actinide, and
combinations thereof; E is XR.sup.3 or YR.sup.3R.sup.4, wherein X
is O, S, or Se, and Y is N or P; each R.sup.1, R.sup.2, and R.sup.3
is independently an organic group; R.sup.4 is hydrogen or an
organic group; L is an anionic supporting ligand; n is the
oxidation state of M; and x is 0 to n-1.
57. The apparatus of claim 56 further comprising at least one
source of at least one reaction gas.
58. The apparatus of claim 56 further comprising at least one
source of an inert gas.
59. A precursor composition for use in a vapor deposition process
comprising at least one compound of the formula (Formula I):
##STR11## wherein: M is selected from the group consisting of a
Group 2 to Group 15 metal, a lanthanide, an actinide, and
combinations thereof; E is OR.sup.3; each R.sup.1, R.sup.2, and
R.sup.3 is independently an organic group; L is an anionic
supporting ligand; n is the oxidation state of M; and x is 0 to
n-1.
60. The precursor composition of claim 59 wherein the organic group
is selected from the group consisting of an alkyl group, an
aliphatic group, a cyclic group, and combinations thereof.
61. The precursor composition of claim 59 wherein L is selected
from the group consisting of halides, amides, alkoxides,
amidoxylates, amidinates, amidates, carboxylates, beta-diketonates,
beta-imineketones, beta-diketiminates, carbonylates, ketiminates,
and combinations thereof.
62. A precursor composition for use in a vapor deposition process
comprising at least one compound of the formula (Formula I):
##STR12## wherein: M is lanthanum; E is XR.sup.3 or
YR.sup.3R.sup.4, wherein X is O, S, or Se, and Y is N or P; each
R.sup.1, R.sup.2, and R.sup.3 is independently an organic group;
R.sup.4 is hydrogen or an organic group; L is an anionic supporting
ligand; n is the oxidation state of M; and x is 0 to n-1.
63. The precursor composition of claim 62 wherein the organic group
is selected from the group consisting of an alkyl group, an
aliphatic group, a cyclic group, and combinations thereof.
64. The precursor composition of claim 62 wherein L is selected
from the group consisting of halides, amides, alkoxides,
amidoxylates, amidinates, amidates, carboxylates, beta-diketonates,
beta-imineketones, beta-diketiminates, carbonylates, ketiminates,
and combinations thereof.
65. A precursor composition for use in a vapor deposition process
comprising at least one compound of the formula (Formula I):
##STR13## wherein: M is hafnium; E is XR.sup.3 or YR.sup.3R.sup.4,
wherein X is O, S, or Se, and Y is N or P; R.sup.1 and R.sup.2 are
isopropyl groups; R.sup.3 is an organic group; R.sup.4 is hydrogen
or an organic group; L is an anionic supporting ligand; n is the
oxidation state of M; and x is 0 to n-1.
66. The precursor composition of claim 65 wherein the organic group
is selected from the group consisting of an alkyl group, an
aliphatic group, a cyclic group, and combinations thereof.
67. The precursor composition of claim 65 wherein L is selected
from the group consisting of halides, amides, alkoxides,
amidoxylates, amidinates, amidates, carboxylates, beta-diketonates,
beta-imineketones, beta-diketiminates, carbonylates, ketiminates,
and combinations thereof.
Description
BACKGROUND OF THE INVENTION
[0001] In integrated circuit manufacturing, microelectronic devices
such as capacitors are the basic energy storage devices in random
access memory devices, such as dynamic random access memory (DRAM)
devices, static random access memory (SRAM) devices, and
ferroelectric memory (FERAM) devices. Capacitors typically consist
of two conductors, such as parallel metal or polysilicon plates,
which act as the electrodes (i.e., the storage node electrode and
the cell plate capacitor electrode), insulated from each other by a
layer of dielectric material.
[0002] The continuous shrinkage of microelectronic devices such as
capacitors and gates over the years has led to a situation where
the materials traditionally used in integrated circuit technology
are approaching their performance limits. Silicon (i.e., doped
polysilicon) has generally been the substrate of choice, and
silicon dioxide (SiO.sub.2) has frequently been used as the
dielectric material with silicon to construct microelectronic
devices. However, when the SiO.sub.2 layer is thinned to 1
nanometer (nm) (i.e., a thickness of only 4 or 5 molecules), as is
desired in the newest micro devices, the layer no longer
effectively performs as an insulator due to the tunneling current
running through it.
[0003] Thus, new high dielectric constant materials are needed to
extend device performance. Such materials need to demonstrate high
permittivity, barrier height to prevent tunneling, stability in
direct contact with silicon, and good interface quality and film
morphology. Furthermore, such materials must be compatible with the
gate material, electrodes, semiconductor processing temperatures,
and operating conditions.
[0004] Additionally, as integrated circuit (IC) dimensions shrink,
the ability to deposit conformal thin films with excellent step
coverage at low deposition temperatures is becoming increasingly
important. Thin films are used, for example, in and/or for MOSFET
gate dielectrics, DRAM capacitor dielectrics, adhesion promoting
layers, diffusion barrier layers, electrode layers, seed layers,
and/or for many other various functions. Low temperature processing
is desired, for example, to better control certain reactions and to
prevent degradation of previously deposited materials and their
interfaces.
[0005] High quality thin oxide films of metals, such as ZrO.sub.2,
Ta.sub.2O.sub.5, HfO.sub.2, Al.sub.2O.sub.3, Nb.sub.2O.sub.5, and
YSZ deposited on semiconductor wafers have recently gained interest
for use in memories (e.g., dynamic random access memory (DRAM)
devices, static random access memory (SRAM) devices, and
ferroelectric memory (FERAM) devices). These materials have high
dielectric constants and therefore are attractive as replacements
in memories for SiO.sub.2 where very thin layers are required.
These metal oxide layers are thermodynamically stable in the
presence of silicon, minimizing silicon oxidation upon thermal
annealing, and appear to be compatible with metal gate electrodes.
Additionally, Nb.sub.2O.sub.5, Nb.sub.2O.sub.5, La.sub.2O.sub.3,
and/or Pr.sub.2O.sub.3 doped/laminated Al.sub.2O.sub.3,
Ta.sub.2O.sub.5, and HfO.sub.2 films have been shown to be useful
for capacitor and gate dielectrics. Nb.sub.2O.sub.5
doping/laminating has been shown to decrease leakage and stabilize
crystalline phases.
[0006] Efforts have been made to investigate various deposition
processes to form layers, especially dielectric layers, based on
metal oxides and/or metal nitrides. Such deposition processes have
included vapor deposition, metal thermal oxidation, and high vacuum
sputtering. Vapor deposition processes, which include chemical
vapor deposition (CVD) and atomic layer deposition (ALD) are very
appealing, as they provide for excellent control of dielectric
uniformity and thickness on a substrate.
SUMMARY OF THE INVENTION
[0007] In view of the foregoing, and despite improvements in
semiconductor dielectric layers, there remains a need in the
semiconductor art a vapor deposition process utilizing sufficiently
volatile metal precursor compounds that can form a thin, high
quality oxide layers on a substrate, particularly on a
semiconductor substrate, using a vapor deposition process,
particularly chemical vapor deposition (CVD) process and/or an
atomic layer deposition (ALD) process.
[0008] Accordingly, the present invention is directed to methods
and precursor compositions useful for CVD and ALD processes. In one
aspect, the present invention is directed to: a method of forming a
metal-containing layer on a substrate, the method including:
providing a substrate; providing a precursor composition comprising
at least one compound of the formula (Formula I): ##STR1## wherein:
M is selected from the group of a Group 2 to Group 15 metal, a
lanthanide, an actinide, and combinations thereof; E is XR.sup.3 or
YR.sup.3R.sup.4, wherein X is O, S, or Se, and Y is N or P; each
R.sup.1, R.sup.2, and R.sup.3 is independently an organic group;
R.sup.4 is hydrogen or an organic group; L is an anionic supporting
ligand; n is the oxidation state of M; and x is 0 to n-1;
vaporizing the precursor composition; and contacting the vaporized
precursor composition to form a metal-containing layer on the
substrate using a vapor deposition process.
[0009] In a further aspect, the present invention is directed to a
method of manufacturing a semiconductor structure, the method
including: providing a semiconductor substrate or substrate
assembly; providing at least one precursor compound of the formula
(Formula I): ##STR2## wherein: M is selected from the group of a
Group 2 to Group 15 metal, a lanthanide, an actinide, and
combinations thereof; E is XR.sup.3 or YR.sup.3R.sup.4, wherein X
is O, S, or Se, and Y is N or P; each R.sup.1, R.sup.2, and R.sup.3
is independently an organic group; R.sup.4 is hydrogen or an
organic group; L is an anionic supporting ligand; n is the
oxidation state of M; and x is 0 to n-1; providing at least one
reaction gas; vaporizing the precursor compound of Formula I; and
contacting the vaporized precursor compound of Formula I and the
reaction gas with the substrate to form a metal-containing layer on
the semiconductor substrate or substrate assembly using a vapor
deposition process.
[0010] In yet another aspect, the present invention is directed to
a method of manufacturing a semiconductor structure, the method
including: providing a semiconductor substrate or substrate
assembly within a deposition chamber; providing a vapor comprising
at least one precursor compound of the formula (Formula I):
##STR3## wherein: M is selected from the group of a Group 2 to
Group 15 metal, a lanthanide, an actinide, and combinations
thereof; E is XR.sup.3 or YR.sup.3R.sup.4, wherein X is O, S, or
Se, and Y is N or P; each R.sup.1, R.sup.2, and R.sup.3 is
independently an organic group; R.sup.4 is hydrogen or an organic
group; L is an anionic supporting ligand; n is the oxidation state
of M; and x is 0 to n-1; directing the vapor including the at least
one precursor compound of Formula I to the semiconductor substrate
or substrate assembly and allowing the at least one compound to
chemisorb to at least one surface of the semiconductor substrate or
substrate assembly; providing at least one reaction gas; and
directing the at least one reaction gas to the semiconductor
substrate or substrate assembly with the chemisorbed species
thereon to form a metal-containing layer on at least one surface of
the semiconductor substrate or substrate assembly.
[0011] In still a further aspect, the present invention is directed
to a method of manufacturing a memory device structure, the method
including: providing a substrate having a first electrode thereon;
providing at least one precursor compound of the formula (Formula
I): ##STR4## wherein: M is selected from the group of a Group 2 to
Group 15 metal, a lanthanide, an actinide, and combinations
thereof; E is XR.sup.3 or YR.sup.3R.sup.4, wherein X is O, S, or
Se, and Y is N or P; each R.sup.1, R.sup.2, and R.sup.3 is
independently an organic group; R.sup.4 is hydrogen or an organic
group; L is an anionic supporting ligand; n is the oxidation state
of M; and x is 0 to n-1; vaporizing the at least one precursor
compound of Formula I; contacting the at least one vaporized
precursor compound of Formula I with the substrate to chemisorb the
compound on the first electrode of the substrate; providing at
least one reaction gas; contacting the at least one reaction gas
with the substrate with the chemisorbed compound thereon to form a
dielectric layer on the first electrode of the substrate; and
forming a second electrode on the dielectric layer.
[0012] The present invention additionally is directed to apparatus
useful for vapor deposition processes, preferably atomic layer
deposition processes, as described herein. To this end, the present
invention is further directed to a vapor deposition apparatus
including: a deposition chamber having a substrate positioned
therein; and at least one vessel including at least one precursor
compound of the formula (Formula I): ##STR5## wherein: M is
selected from the group of a Group 2 to Group 15 metal, a
lanthanide, an actinide, and combinations thereof; E is XR.sup.3 or
YR.sup.3R.sup.4, wherein X is O, S, or Se, and Y is N or P; each
R.sup.1, R.sup.2, and R.sup.3 is independently an organic group;
R.sup.4 is hydrogen or an organic group; L is an anionic supporting
ligand; n is the oxidation state of M; and x is 0 to n-1.
[0013] The present invention is additionally directed to certain
precursor compositions useful for vapor deposition processes and
disclosed herein. In one such embodiment, the present invention is
directed to a precursor composition for use in a vapor deposition
process including at least one compound of the formula (Formula I):
##STR6## wherein: M is selected from the group of a Group 2 to
Group 15 metal, a lanthanide, an actinide, and combinations
thereof; E is OR.sup.3; each R.sup.1, R.sup.2, and R.sup.3 is
independently an organic group; L is an anionic supporting ligand;
n is the oxidation state of M; and x is O to n-1.
[0014] In another embodiment, the present invention is directed to
a precursor composition for use in a vapor deposition process
including at least one compound of the formula (Formula I):
##STR7## wherein: M is lanthanum; E is XR.sup.3 or YR.sup.3R.sup.4,
wherein X is O, S, or Se, and Y is N or P; each R.sup.1, R.sup.2,
and R.sup.3 is independently an organic group; R.sup.4 is hydrogen
or an organic group; L is an anionic supporting ligand; n is the
oxidation state of M; and x is 0 to n-1.
[0015] In yet a further embodiment, the present invention is
directed to a precursor composition for use in a vapor deposition
process including at least one compound of the formula (Formula I):
##STR8## wherein: M is hafnium; E is XR.sup.3 or YR.sup.3R.sup.4,
wherein X is O, S, or Se, and Y is N or P; R.sup.1 and R.sup.2 are
isopropyl groups, R.sup.3 is an organic group; R.sup.4 is hydrogen
or an organic group; L is an anionic supporting ligand; n is the
oxidation state of M; and x is 0 to n-1.
[0016] Metal-organic complexes containing chelating ligands (e.g.,
two or more atoms on each ligand coordinate to the metal atom)
often show improved stability compared to metal-organic compounds
with unidentate ligands and may be useful in deposition processes,
provided such compounds have adequate volatility properties.
[0017] It has now been discovered that the use of homoleptic and
heteroleptic guanidinate, phosphoguanidinate, isoureate,
thioisoureate, and selenoisoureate compounds are useful as
precursor compositions for vapor deposition, preferably ALD
processes. Such compounds provide the potential advantage in, for
example, an ALD process in that the protonated ligand (e.g., formed
in situ after chemical adsorption to a surface) may be expected to
decompose to carbodiimide and amine (from guanidinate), to
phosphine (from phosphoguanidinate), to alcohol (from (isoureate),
to thiol (from thioisoureate), or to selenol (from
selenoisoureate). These fragments are believed to be more volatile
than the parent ligands and should, thus, leave less carbon
contamination in the films.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a perspective view of a vapor deposition coating
system suitable for use in the method of the present invention.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS
[0019] The present invention includes methods of forming a metal
containing layer, preferably a metal oxide layer or a metal nitride
layer, on a substrate. Further, such metal containing layer is
preferably formed on a semiconductor substrate or substrate
assembly in the manufacture of a semiconductor structure or another
memory device structure. Such layers are deposited or chemisorbed
onto a substrate and form, preferably, dielectric layers. The
methods of the present invention involve forming a layer on a
substrate by using one or more metal precursor compounds of the
formula (Formula I): ##STR9## wherein: M is a Group 2 to Group 15
metal, a lanthanide, an actinide, and combinations thereof; E is
XR.sup.3 or YR.sup.3R.sup.4, wherein X is O, S, or Se, preferably O
or S, and Y is N or P; each R.sup.1, R.sup.2, and R.sup.3 is
independently an organic group (as described in greater detail
below); R.sup.4 is hydrogen or an organic group; L is an anionic
supporting ligand; n is the oxidation state of M; and x is 0 to
n-1. Preferred ligands, L, include halides, amides, alkoxides,
amidoxylates, amidinates, amidates, carboxylates, beta-diketonates,
beta-imineketones, beta-diketiminates, carbonylates, ketiminates,
and combinations thereof.
[0020] As used herein, the term "organic group" is used for the
purpose of this invention to mean a hydrocarbon group that is
classified as an aliphatic group, cyclic group, or combination of
aliphatic and cyclic groups (e.g., alkaryl and aralkyl groups). In
the context of the present invention, suitable organic groups for
precursor compounds of this invention are those that do not
interfere with the formation of a metal oxide layer using vapor
deposition techniques. In the context of the present invention, the
term "aliphatic group" means a saturated or unsaturated linear or
branched hydrocarbon group. This term is used to encompass alkyl,
alkenyl, and alkynyl groups, for example. The term "alkyl group"
means a saturated linear or branched monovalent hydrocarbon group
including, for example, methyl, ethyl, n-propyl, isopropyl,
t-butyl, amyl, heptyl, and the like. The term "alkenyl group" means
an unsaturated, linear or branched monovalent hydrocarbon group
with one or more olefinically unsaturated groups (i.e.,
carbon-carbon double bonds), such as a vinyl group. The term
"alkynyl group" means an unsaturated, linear or branched monovalent
hydrocarbon group with one or more carbon-carbon triple bonds. The
term "cyclic group" means a closed ring hydrocarbon group that is
classified as an alicyclic group, aromatic group, or heterocyclic
group. The term "alicyclic group" means a cyclic hydrocarbon group
having properties resembling those of aliphatic groups. The term
"aromatic group" or "aryl group" means a mono- or polynuclear
aromatic hydrocarbon group. The term "heterocyclic group" means a
closed ring hydrocarbon in which one or more of the atoms in the
ring is an element other than carbon (e.g., nitrogen, oxygen,
sulfur, etc.). For example, certain preferred organic groups
include cyclic polyethers, polyamines, aromatic groups,
heterocyclic groups, etc.
[0021] As a means of simplifying the discussion and the recitation
of certain terminology used throughout this application, the terms
"group" and "moiety" are used to differentiate between chemical
species that allow for substitution or that may be substituted and
those that do not so allow for substitution or may not be so
substituted. Thus, when the term "group" is used to describe a
chemical substituent, the described chemical material includes the
unsubstituted group and that group with nonperoxidic O, N, S, Si,
or F atoms, for example, in the chain as well as carbonyl groups or
other conventional substituents. Where the term "moiety" is used to
describe a chemical compound or substituent, only an unsubstituted
chemical material is intended to be included. For example, the
phrase "alkyl group" is intended to include not only pure open
chain saturated hydrocarbon alkyl substituents, such as methyl,
ethyl, propyl, t-butyl, and the like, but also alkyl substituents
bearing further substituents known in the art, such as hydroxy,
alkoxy, alkylsulfonyl, halogen atoms, cyano, nitro, amino,
carboxyl, etc. Thus, "alkyl group" includes ether groups,
haloalkyls, nitroalkyls, carboxyalkyls, hydroxyalkyls, sulfoalkyls,
etc. On the other hand, the phrase "alkyl moiety" is limited to the
inclusion of only pure open chain saturated hydrocarbon alkyl
substituents, such as methyl, ethyl, propyl, t-butyl, and the
like.
[0022] The precursor compounds described herein may include a wide
variety of metals. As used herein, "metal" includes all metals of
the periodic table (including main group metals, transition metals,
lanthanides, actinides, and metalloid such as B, Al, Ge, Si, As,
Sb, Te, Po, At, etc.). For certain methods of the present
invention, preferably, each metal M is selected from the group of
metals of Groups 2-15, the lanthanides, the actinides of the
Periodic Chart, and combinations thereof. Preferably, for
metal-oxide layers, M is selected from the group of Groups 3-5,
Group 13. the lanthanides, and combinations thereof. More
preferably, M is selected from the group of Hf, Zr, Al, La, Pr, and
combinations thereof.
[0023] Additionally, E is (XR.sup.3) or (YR.sup.3R.sup.4), with X
being O, S, or Se, Y being N or P, and R.sup.1, R.sup.2, R.sup.3,
and R.sup.4 of Formula I being each independently an organic group,
and with R.sup.4 optionally being hydrogen. Preferably, each of the
organic groups of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 contain
1-10 carbon atoms, more preferably, 1-6 carbon atoms, and most
preferably, 1-4 carbon atoms. Preferred R groups include isopropyl
groups.
[0024] Additionally, each of the organic groups R.sup.1, R.sup.2,
R.sup.3, and R.sup.4 may optionally include one or more heteroatoms
(e.g., oxygen, nitrogen, fluorine, etc.), or functional groups
(e.g., carbonyl groups, hydroxycarbyl groups, aminocarbyl groups,
alcohols, fluorinated alcohols, etc.), provided that the
heteroatoms are not directly bonded to hydrogen. That is, included
within the scope of the compounds of Formula I are compounds
wherein at least one atom in the organic group has been replaced
with, for example, one of a carbonyl group, a hydroxycarbyl group,
an oxygen atom, a nitrogen atom, or an aminocarbyl group. Certain
preferred organic groups, R.sup.1, R.sup.2, R.sup.3, and R.sup.4,
of Formula I include (C1-C4) alkyl groups, which may be linear,
branched, or cyclic groups, as well as alkenyl groups (e.g., dienes
and trienes), or alkynyl groups. An example of a preferred
precursor compound of Formula I is:
La((iPrN).sub.2CNEt.sub.2).sub.3, wherein iPr is isopropyl and Et
is ethyl.
[0025] The terms "substrate," "semiconductor substrate," or
"substrate assembly" as used herein refer to either a substrate or
a semiconductor substrate, such as a base semiconductor layer or a
semiconductor substrate having one or more layers, structures, or
regions formed thereon. A base semiconductor layer is typically the
lowest layer of silicon material on a wafer or a silicon layer
deposited on another material, such as silicon on sapphire. When
reference is made to a substrate assembly, various process steps
may have been previously used to form or define regions, junctions,
various structures or features, and openings such as transistors,
active areas, diffusions, implanted regions, vias, contact
openings, high aspect ratio openings, capacitor plates, barriers
for capacitors, etc.
[0026] "Layer," as used herein, refers to any layer that can be
formed on a substrate from one or more precursors and/or reactants
according to the deposition process described herein. The term
"layer" is meant to include layers specific to the semiconductor
industry, such as, but clearly not limited to, a barrier layer,
dielectric layer, and conductive layer. The term "layer" is
synonymous with the term "film" frequently used in the
semiconductor industry. The term "layer" is also meant to include
layers found in technology outside of semiconductor technology,
such as coatings on glass. For example, such layers can be formed
directly on fibers, wires, etc., which are substrates other than
semiconductor substrates. Further, the layers can be formed
directly on the lowest semiconductor surface of the substrate, or
they can be formed on any of a variety of layers (e.g., surfaces)
as in, for example, a patterned wafer.
[0027] "Dielectric layer" as used herein refers to a layer (or
film) having a high dielectric constant containing primarily, for
example, silicon oxides, zirconium oxides, aluminum oxides,
tantalum oxides, titanium oxides, niobium oxides, hafnium oxides,
an oxide of a lanthanide, or combinations thereof.
[0028] The terms "deposition process" and "vapor deposition
process" as used herein refer to a process in which a
metal-containing layer is formed on one or more surfaces of a
substrate (e.g., a doped polysilicon wafer) from vaporized
precursor compound(s). Specifically, one or more precursor
compounds are vaporized and directed to and/or contacted with one
or more surfaces of a heated substrate (e.g., semiconductor
substrate or substrate assembly) placed in a deposition chamber.
These precursor compounds form (e.g., by reacting or decomposing) a
non-volatile, thin, uniform, metal-containing layer on the
surface(s) of the substrate. For the purposes of this invention,
the term "vapor deposition process" is meant to include both
chemical vapor deposition processes (including pulsed chemical
vapor deposition processes) and atomic layer deposition
processes.
[0029] "Chemical vapor deposition" (CVD) as used herein refers to a
vapor deposition process wherein the desired layer is deposited on
the substrate from vaporized metal precursor compounds (and any
reaction gases used) within a deposition chamber with no effort
made to separate the reaction components. In contrast to a "simple"
CVD process that involves the substantial simultaneous use of the
precursor compounds and any reaction gases. "pulsed" CVD
alternately pulses these materials into the deposition chamber, but
does not rigorously avoid intermixing of the precursor and reaction
gas streams, as is typically done in atomic layer deposition or ALD
(discussed in greater detail below).
[0030] The term "atomic layer deposition" (ALD) as used herein
refers to a vapor deposition process in which deposition cycles,
preferably a plurality of consecutive deposition cycles, are
conducted in a process chamber (i.e., a deposition chamber).
Typically, during each cycle the precursor is chemisorbed to a
deposition surface (e.g., a substrate assembly surface or a
previously deposited underlying surface such as material from a
previous ALD cycle). Thereafter, if necessary, a reactant may
subsequently be introduced into the process chamber for use in
converting the chemisorbed precursor to the desired material on the
deposition surface. Further, purging steps may also be utilized
during each cycle to remove excess precursor from the process
chamber and/or remove excess reactant and/or reaction byproducts
from the process chamber after conversion of the chemisorbed
precursor. Further, the term "atomic layer deposition," as used
herein, is also meant to include processes designated by related
terms such as, "chemical vapor atomic layer deposition", "atomic
layer epitaxy" (ALE) (see U.S. Pat. No. 5,256,244 to Ackerman).
molecular beam epitaxy (MBE), gas source MBE, or organometallic
MBE, and chemical beam epitaxy when performed with alternating
pulses of precursor compound(s), reactive gas, and purge (e.g.,
inert carrier) gas.
[0031] As compared to the one cycle chemical vapor deposition (CVD)
process, the longer duration multi-cycle ALD process allows for
improved control of layer thickness by self-limiting layer growth
and minimizing detrimental gas phase reactions by separation of the
reaction components.
[0032] "Precursor," and "precursor compound" as used herein, refers
to a compound usable for forming, either alone or with other
precursor compounds (or reactants), a layer on a substrate assembly
in a deposition process. In one embodiment according to the present
invention, the precursor includes a metal component and one or more
guanidinate, phosphoguanidinate, isoureate, thioisoureate, and/or
selenoisoureate ligands. Further, one skilled in the art will
recognize that the precursor will depend on the content of a layer
which is ultimately to be formed using a vapor deposition process.
The preferred precursor compounds of the present invention are
preferably liquid at the vaporization temperature and, more
preferably, are preferably liquid at room temperature.
[0033] The term "chemisorption" as used herein refers to the
chemical adsorption of vaporized reactive precursor compounds on
the surface of a substrate. The adsorbed species are typically
irreversibly bound to the substrate surface as a result of
relatively strong binding forces characterized by high adsorption
energies (e.g., >30 kcal/mol), comparable in strength to
ordinary chemical bonds. The chemisorbed species typically form a
mononolayer on the substrate surface. (See "The Condensed Chemical
Dictionary", 10th edition, revised by G. G. Hawley, published by
Van Nostrand Reinhold Co., New York, 225 (1981)). The technique of
ALD is based on the principle of the formation of a saturated
monolayer of reactive precursor molecules by chemisorption. In ALD
one or more appropriate precursor compounds or reaction gases are
alternately introduced (e.g., pulsed) into a deposition chamber and
chemisorbed onto the surfaces of a substrate. Each sequential
introduction of a reactive compound (e.g., one or more precursor
compounds and one or more reaction gases) is typically separated by
an inert carrier gas purge. Each precursor compound co-reaction
adds a new atomic layer to previously deposited layers to form a
cumulative solid layer. The cycle is repeated, typically for
several hundred times, to gradually form the desired layer
thickness. It should be understood that ALD can alternately utilize
one precursor compound, which is chemisorbed, and one reaction gas,
which reacts with the chemisorbed species.
[0034] Practically, chemisorption might not occur on all portions
of the deposition surface (e.g., previously deposited ALD
material). Nevertheless, such imperfect monolayer is still
considered a monolayer in the context of the present invention. In
many applications, merely a substantially saturated monolayer may
be suitable. A substantially saturated monolayer is one that will
still yield a deposited monolayer or less of material exhibiting
the desired quality and/or properties.
[0035] "Reactant," as used herein, may include another precursor or
reactant gas useable according to the present invention in an ALD
cycle. For example, to prepare a metal oxide layer, a reactant gas
may include an oxidizing gas such as oxygen, water vapor, ozone,
alcohol vapor, nitrogen oxide, sulfur oxide, hydrogen peroxide, and
the like. To prepare a metal-nitride layer, a reactant gas may
include, for example, ammonia or amines (preferably primary
amines). To prepare a pure metal layer, a reactant gas may include
hydrogen, diborane or silane. However, such reactants may include
any reactant(s) suitable for use in converting the chemisorbed
species present on the deposition surface as part of an ALD cycle
(e.g., provide a reducing atmosphere). As one skilled in the art
will recognize, such reactants will depend upon the layer
ultimately formed from the vapor deposition process.
[0036] "Inert gas," or "non-reactive gas." as used herein, is any
gas that is generally unreactive with the components it comes in
contact with. For example, inert gases are typically selected from
a group including nitrogen, argon, helium, neon, krypton, xenon,
any other non-reactive gas, and mixtures thereof. Such inert gases
are generally used in one or more purging processes described
according to the present invention.
[0037] "Purging," according to the present invention, may involve a
variety of techniques including, but not limited to, contacting the
substrate and/or monolayer(s) formed according to the present
invention with a carrier gas (e.g., an inert gas), and/or lowering
pressure to below the deposition pressure to reduce the
concentration of a species contacting the substrate assembly
surface and/or chemisorbed species. Purging may also include
contacting the substrate assembly surface and/or monolayer(s)
formed thereon with any substance that allows chemisorption
byproducts to desorb and reduces the concentration of a species
preparatory to introducing another species. A suitable amount of
purging can be determined experimentally, as known to those skilled
in the art. Purging time may successively be reduced to a purge
time that yields desirable results, such as an increase in film
growth rate.
[0038] The layers or films formed may be in the form of
metal-containing films, such as reduced metals, metal silicates,
metal oxides, metal nitrides, etc, as well as combinations thereof.
For example, a metal oxide layer may include a single metal, or the
metal oxide layer may include two or more different metals (i.e.,
it is a mixed metal oxide) or a metal oxide layer may optionally be
doped with other metals.
[0039] If the metal oxide layer includes two or more different
metals, the metal oxide layer can be in the form of alloys, solid
solutions, or nanolaminates. Preferably, these have dielectric
properties. The metal oxide layer (particularly if it is a
dielectric layer) preferably includes one or more of HfO.sub.2,
ZrO.sub.2, Al.sub.2O.sub.3, La.sub.2O.sub.3, and Pr.sub.2O.sub.3.
Surprisingly, the metal oxide layer formed according to the present
invention is essentially free of carbon. In addition, preferably
the reduced metal layers formed by the systems and methods of the
present invention are essentially free of carbon, hydrogen,
halides, oxygen, phosphorus, sulfur, nitrogen, or compounds
thereof. Additionally, preferably metal-oxide layers formed by the
systems and methods of the present invention are essentially free
of carbon, hydrogen, halides, phosphorus, sulfur, nitrogen or
compounds thereof, and preferably metal-nitride layers formed by
the systems and methods of the present invention are essentially
free of carbon, hydrogen, halides, oxygen, phosphorus, sulfur, or
compounds thereof. As used herein. "essentially free" is defined to
mean that the metal-containing layer may include a small amount of
the above impurities. For example, for metal-oxide layers,
"essentially free" means that the above impurities are present in
an amount of less than about 1 percent (%) by weight, such that
they have a minor effect on the chemical, mechanical, or electrical
properties of the film. Pure metal layers and metal-nitride layers,
may tolerate a higher impurity content. For these layers,
"essentially free" means that the above impurities are present in
an amount of less than about 20% by weight.
[0040] In addition to the precursor compositions of Formula I, the
present invention includes methods and apparatus in which a metal
containing precursor compound different that the precursor compound
of Formula I may be used. Such precursors may be
deposited/chemisorbed, for example in an ALD process discussed more
fully below, substantially simultaneously with or sequentially to
the precursor compounds of Formula I.
[0041] Various precursor compounds can be used in various
combinations, optionally with one or more organic solvents
(particularly for CVD processes), to form a precursor composition.
The precursor compounds may be liquids or solids at room
temperature (preferably, they are liquids at the vaporization
temperature). Typically, they are liquids sufficiently volatile to
be employed using known vapor deposition techniques. However, as
solids they may also be sufficiently volatile that they can be
vaporized or sublimed from the solid state using known vapor
deposition techniques. If they are less volatile solids, they are
preferably sufficiently soluble in an organic solvent or have
melting points below their decomposition temperatures such that
they can be used in flash vaporization, bubbling, microdroplet
formation techniques, etc.
[0042] Herein, vaporized precursor compounds may be used either
alone or optionally with vaporized molecules of other precursor
compounds or optionally with vaporized solvent molecules, if used.
As used herein, "liquid" refers to a solution or a neat liquid (a
liquid at room temperature or a solid at room temperature that
melts at an elevated temperature). As used herein, "solution" does
not require complete solubility of the solid but may allow for some
undissolved solid, as long as there is a sufficient amount of the
solid delivered by the organic solvent into the vapor phase for
chemical vapor deposition processing. If solvent dilution is used
in deposition, the total molar concentration of solvent vapor
generated may also be considered as a inert carrier gas.
[0043] Solvents that are suitable for certain embodiments of the
present invention may be one or more of the following: aliphatic
hydrocarbons or unsaturated hydrocarbons (C3-C20, and preferably
C5-C10, cyclic, branched, or linear), aromatic hydrocarbons
(C5-C20, and preferably C5-C10), halogenated hydrocarbons,
silylated hydrocarbons such as alkylsilanes, alkylsilicates,
ethers, polyethers, thioethers, esters, lactones, nitriles,
silicone oils, or compounds containing combinations of any of the
above or mixtures of one or more of the above. The compounds are
also generally compatible with each other, so that mixtures of
variable quantities of the precursor compounds will not interact to
significantly change their physical properties.
[0044] The precursor compounds of the present invention can,
optionally, be vaporized and deposited/chemisorbed substantially
simultaneously with, and in the presence of, one or more reaction
gases. Alternatively, the metal containing layers may be formed by
alternately introducing the precursor compound and the reaction
gas(es) during each deposition cycle. Such reaction gases may
typically include oxygen, water vapor, ozone, nitrogen oxides,
sulfur oxides, hydrogen, hydrogen sulfide, hydrogen selenide,
hydrogen telluride, hydrogen peroxide, ammonia, organic amine,
silane, disilane and higher silanes, diborane, plasma, air,
borazene (nitrogen source), carbon monoxide (reductant), alcohols,
and any combination of these gases, noting that certain reaction
gases may be more appropriate for certain metal-containing layers.
For example, oxygen sources for the deposition of metal-oxide
layers, nitrogen sources for deposition of metal-nitride layers,
and reductants for deposition of reduced metal layers. Preferable
optional reaction gases for metal-oxide layers include oxygen and
ozone.
[0045] Suitable substrate materials of the present invention
include conductive materials, semiconductive materials, conductive
metal-nitrides, conductive metals, etc. The substrate on which the
metal containing layer is formed is preferably a semiconductor
substrate or substrate assembly. Any suitable semiconductor
material is contemplated, such as for example, borophosphosilicate
glass (BPSG), silicon such as, e.g., conductively doped
polysilicon, monocrystalline silicon, etc. (for this invention,
appropriate forms of silicon are simply referred to as "silicon"),
for example in the form of a silicon wafer, tetraethylorthosilicate
(TEOS) oxide, spin on glass (i.e., a thin layer of SiO.sub.2,
optionally doped, deposited by a spin on process), TiN, TaN, W, Ru,
Al, Cu, noble metals, etc. A substrate assembly may also contain a
layer that includes platinum, iridium, rhodium, ruthenium,
ruthenium oxide, titanium nitride, tantalum nitride,
tantalum-silicon-nitride, silicon dioxide, aluminum, gallium
arsenide, glass, etc., and other existing or to-be-developed
materials used in semiconductor constructions, such as dynamic
random access memory (DRAM) devices, static random access memory
(SRAM) devices, and ferroelectric memory (FERAM) devices, for
example.
[0046] For substrates including semiconductor substrates or
substrate assemblies, the layers can be formed directly on the
lowest semiconductor surface of the substrate, or they can be
formed on any of a variety of the layers (i.e., surfaces) as in a
patterned wafer, for example.
[0047] Substrates other than semiconductor substrates or substrate
assemblies can also be used in methods of the present invention.
Any substrate that may advantageously form a metal containing layer
thereon, such as a metal oxide layer, may be used, such substrates
including, for example, fibers, wires, etc.
[0048] A preferred deposition process for the present invention is
a vapor deposition process. Vapor deposition processes are
generally favored in the semiconductor industry due to the process
capability to quickly provide highly conformal layers even within
deep contacts and other openings.
[0049] The precursor compounds can be vaporized in the presence of
an inert carrier gas if desired. Additionally, an inert carrier gas
can be used in purging steps in an ALD process (discussed below).
The inert carrier gas is typically one or more of nitrogen, helium,
argon, etc. In the context of the present invention, an inert
carrier gas is one that does not interfere with the formation of
the metal-containing layer. Whether done in the presence of a inert
carrier gas or not, the vaporization is preferably done in the
absence of oxygen to avoid oxygen contamination of the layer (e.g.,
oxidation of silicon to form silicon dioxide or oxidation of
precursor in the vapor phase prior to entry into the deposition
chamber).
[0050] Chemical vapor deposition (CVD) and atomic layer deposition
(ALD) are two vapor deposition processes often employed to form
thin, continuous, uniform, metal-containing (preferably dielectric)
layers onto semiconductor substrates. Using either vapor deposition
process, typically one or more precursor compounds are vaporized in
a deposition chamber and optionally combined with one or more
reaction gases and directed to and/or contacted with the substrate
to form a metal-containing layer on the substrate. It will be
readily apparent to one skilled in the art that the vapor
deposition process may be enhanced by employing various related
techniques such as plasma assistance, photo assistance, laser
assistance, as well as other techniques.
[0051] Chemical vapor deposition (CVD) has been extensively used
for the preparation of metal-containing layers, such as dielectric
layers, in semiconductor processing because of its ability to
provide highly conformal and high quality dielectric layers at
relatively fast processing times. Typically, the desired precursor
compounds are vaporized and then introduced into a deposition
chamber containing a heated substrate with optional reaction gases
and/or inert carrier gases in a single deposition cycle. In a
typical CVD process, vaporized precursors are contacted with
reaction gas(es) at the substrate surface to form a layer (e.g.,
dielectric layer). The single deposition cycle is allowed to
continue until the desired thickness of the layer is achieved.
[0052] Typical CVD processes generally employ precursor compounds
in vaporization chambers that are separated from the process
chamber wherein the deposition surface or wafer is located. For
example, liquid precursor compounds are typically placed in
bubblers and heated to a temperature at which they vaporize, and
the vaporized liquid precursor compound is then transported by an
inert carrier gas passing over the bubbler or through the liquid
precursor compound. The vapors are then swept through a gas line to
the deposition chamber for depositing a layer on substrate
surface(s) therein. Many techniques have been developed to
precisely control this process. For example, the amount of
precursor material transported to the deposition chamber can be
precisely controlled by the temperature of the reservoir containing
the precursor compound and by the flow of an inert carrier gas
bubbled through or passed over the reservoir.
[0053] A typical CVD process may be carried out in a chemical vapor
deposition reactor, such as a deposition chamber available under
the trade designation of 7000 from Genus, Inc. (Sunnyvale, Calif.),
a deposition chamber available under the trade designation of 5000
from Applied Materials, Inc. (Santa Clara, Calif.), or a deposition
chamber available under the trade designation of Prism from
Novelus, Inc. (San Jose, Calif.). However, any deposition chamber
suitable for performing CVD may be used.
[0054] Several modifications of the CVD process and chambers are
possible, for example, using atmospheric pressure chemical vapor
deposition, low pressure chemical vapor deposition (LPCVD), plasma
enhanced chemical vapor deposition (PECVD), hot wall or cold wall
reactors or any other chemical vapor deposition technique.
Furthermore, pulsed CVD can be used, which is similar to ALD
(discussed in greater detail below) but does not rigorously avoid
intermixing of precursor and reactant gas streams. Also, for pulsed
CVD, the deposition thickness is dependent on the exposure time, as
opposed to ALD, which is self-limiting (discussed in more detail
below).
[0055] Alternatively, and preferably, the vapor deposition process
employed in the methods of the present invention is a multi-cycle
atomic layer deposition (ALD) process. Such a process is
advantageous, in particular advantageous over a CVD process, in
that in provides for improved control of atomic-level thickness and
uniformity to the deposited layer (e.g., dielectric layer) by
providing a plurality of deposition cycles. Further, ALD processes
typically expose the metal precursor compounds to lower
volatilization and reaction temperatures, which tends to decrease
degradation of the precursor as compared to, for example, typical
CVD processes.
[0056] Generally in an ALD process, each reactant is pulsed
sequentially onto a suitable substrate, typically at deposition
temperatures of at least about 25.degree. C., preferably at least
about 150.degree. C., and more preferably at least about
200.degree. C. Typical deposition temperatures are no greater than
about 400.degree. C., preferably no greater than about 150.degree.
C., and even more preferably no greater than about 250.degree. C.
These temperatures are generally lower than those presently used in
CVD processes, which typically include deposition temperatures at
the substrate surface of at least about 150.degree. C., preferably
at least about 200.degree. C., and more preferably at least about
250.degree. C. Typical deposition temperatures are no greater than
about 600.degree. C., preferably no greater than about 500.degree.
C., and even more preferably no greater than about 400.degree. C.
Under such conditions the film growth is typically self-limiting
(i.e., when the reactive sites on a surface are used up in an ALD
process, the deposition generally stops), insuring not only
excellent conformality but also good large area uniformity plus
simple and accurate thickness control. Due to alternate dosing of
the precursor compounds and/or reaction gases, detrimental
vapor-phase reactions are inherently eliminated, in contrast to the
CVD process that is carried out by continuous coreaction of the
precursors and/or reaction gases. (See Vehkamaki et al, "Growth of
SrTiO.sub.3 and BaTIO.sub.3 Thin Films by Atomic Layer Deposition,"
Electrochemical and Solid-State Letters. 2(10):504-506 (1999)).
[0057] A typical ALD process includes exposing an initial substrate
to a first chemical species A (e.g., a metal precursor compound
such as that of Formula I) to accomplish chemisorption of the
species onto the substrate. Species A can react either with the
substrate surface of with Species B (described below) but not with
itself. Typically in chemisorption, one or more of the ligands of
Species A is displaced by reactive groups on the substrate surface.
Theoretically, the chemisorption forms a monolayer that is
uniformly one atom or molecule thick on the entire exposed initial
substrate, the monolayer being composed of Species A, less any
displaced ligands. In other words, a saturated monolayer is
substantially formed on the substrate surface. Practically,
chemisorption may not occur on all portions of the substrate.
Nevertheless, such a partial monolayer is still understood to be a
monolayer in the context of the present invention. In many
applications, merely a substantially saturated monolayer may be
suitable. A substantially saturated monolayer is one that will
still yield a deposited layer exhibiting the quality and/or
properties desired for such layer.
[0058] The first species (e.g., substantially all non-chemisorbed
molecules of Species A) as well as displaced ligands are purged
from over the substrate and a second chemical species, Species B
(e.g., a different precursor compound or reactant gas) is provided
to react with the monolayer of Species A. Species B typically
displaces the remaining ligands from the Species A monolayer and
thereby is chemisorbed and forms a second monolayer. This second
monolayer displays a surface which is reactive only to Species A.
Non-chemisorbed Species B, as well as displaced ligands and other
byproducts of the reaction are then purged and the steps are
repeated with exposure of the Species B monolayer to vaporized
Species A. Optionally, the second species can react with the first
species, but not chemisorb additional material thereto. That is,
the second species can cleave some portion of the chemisorbed first
species, altering such monolayer without forming another monolayer
thereon, but leaving reactive sites available for formation of
subsequent monolayers. In other ALD processes, a third species or
more may be successively chemisorbed (or reacted) and purged just
as described for the first and second species, with the
understanding that each introduced species reacts with the
monolayer produced immediately prior to its introduction.
Optionally, the second species (or third or subsequent) can include
at least one reaction gas if desired.
[0059] Thus, the use of ALD provides the ability to improve the
control of thickness and uniformity of metal containing layers on a
substrate. For example, depositing thin layers of precursor
compound in a plurality of cycles provides a more accurate control
of ultimate film thickness. This is particularly advantageous when
the precursor compound is directed to the substrate and allowed to
chemisorb thereon, preferably further including at least one
reaction gas that reacts with the chemisorbed species on the
substrate, and even more preferably wherein this cycle is repeated
at least once.
[0060] Purging of excess vapor of each species following
deposition/chemisorption onto a substrate may involve a variety of
techniques including, but not limited to, contacting the substrate
and/or monolayer with an inert carrier gas and/or lowering pressure
to below the deposition pressure to reduce the concentration of a
species contacting the substrate and/or chemisorbed species.
Examples of carrier gases, as discussed above, may include N.sub.2,
Ar, He, etc. Additionally, purging may instead include contacting
the substrate and/or monolayer with any substance that allows
chemisorption by-products to desorb and reduces the concentration
of a contacting species preparatory to introducing another species.
The contacting species may be reduced to some suitable
concentration or partial pressure known to those skilled in the art
based on the specifications for the product of a particular
deposition process.
[0061] ALD is often described as a self-limiting process, in that a
finite number of sites exist on a substrate to which the first
species may form chemical bonds. The second species might only bond
to the first species and thus may also be self-limiting. Once all
of the finite number of sites on a substrate are bonded with a
first species, the first species will not bond to other of the
first species already bonded with the substrate. However, process
conditions can be varied in ALD to promote such bonding and render
ALD not self-limiting, e.g., more like pulsed CVD. Accordingly, ALD
may also encompass a species forming other than one monolayer at a
time by stacking of a species, forming a layer more than one atom
or molecule thick.
[0062] The described method indicates the "substantial absence" of
the second precursor (i.e., second species) during chemisorption of
the first precursor since insignificant amounts of the second
precursor might be present. According to the knowledge and the
preferences of those with ordinary skill in the art, a
determination can be made as to the tolerable amount of second
precursor and process conditions selected to achieve the
substantial absence of the second precursor.
[0063] Thus, during the ALD process, numerous consecutive
deposition cycles are conducted in the deposition chamber, each
cycle depositing a very thin metal-containing layer (usually less
than one monolayer such that the growth rate on average is from
about 0.2 to about 3.0 Angstroms per cycle), until a layer of the
desired thickness is built up on the substrate of interest. The
layer deposition is accomplished by alternately introducing (i.e.,
by pulsing) precursor compound(s) into the deposition chamber
containing a substrate, chemisorbing the precursor compound(s) as a
monolayer onto the substrate surfaces, purging the deposition
chamber, then introducing to the chemisorbed precursor compound(s)
precursor compound(s) that may be the same as the first precursor
compound(s) or may be other precursor compound(s) in a plurality of
deposition cycles until the desired thickness of the
metal-containing layer is achieved. Preferred thicknesses of the
metal containing layers of the present invention are at least about
1 angstrom (.ANG.), more preferably at least about 5 .ANG., and
more preferably at least about 10 .ANG.. Additionally, preferred
film thicknesses are typically no greater than about 500 .ANG.,
more preferably no greater than about 200 .ANG., and more
preferably no greater than about 100 .ANG..
[0064] The pulse duration of precursor compound(s) and inert
carrier gas(es) is generally of a duration sufficient to saturate
the substrate surface. Typically, the pulse duration is at least
about 0.1, preferably at least about 0.2 second, and more
preferably at least about 0.5 second. Preferred pulse durations are
generally no greater than about 5 seconds, and preferably no
greater than about 3 seconds.
[0065] In comparison to the predominantly thermally driven CVD, ALD
is predominantly chemically driven. Thus, ALD may advantageously be
conducted at much lower temperatures than CVD. During the ALD
process, the substrate temperature may be maintained at a
temperature sufficiently low to maintain intact bonds between the
chemisorbed precursor compound(s) and the underlying substrate
surface and to prevent decomposition of the precursor compound(s).
The temperature, on the other hand, must be sufficiently high to
avoid condensation of the precursor compounds(s). Typically the
substrate temperature is kept within the range of about 25.degree.
C. to about 400.degree. C. (preferably about 150.degree. C. to
about 300.degree. C., and more preferably about 200.degree. C. to
about 250.degree. C.), which, as discussed above, is generally
lower than temperatures presently used in typical CVD processes.
Thus, the first species or precursor compound is chemisorbed at
this temperature. Surface reaction of the second species or
precursor compound can occur at substantially the same temperature
as chemisorption of the first precursor or, optionally but less
preferably, at a substantially different temperature. Clearly, some
small variation in temperature, as judged by those of ordinary
skill, can occur but still be considered substantially the same
temperature by providing a reaction rate statistically the same as
would occur at the temperature of the first precursor
chemisorption. Alternatively, chemisorption and subsequent
reactions could instead occur at substantially exactly the same
temperature.
[0066] For a typical vapor deposition process, the pressure inside
the deposition chamber is at least about 10.sup.-6 torr, preferably
at least about 10.sup.-5 torr, and more preferably at least about
10 torr. Further, deposition pressures are typically no greater
than about 10 torr, preferably no greater than about 1 torr, and
more preferably no greater than about 10.sup.-1 torr. Typically,
the deposition chamber is purged with an inert carrier gas after
the vaporized precursor compound(s) have been introduced into the
chamber and/or reacted for each cycle. The inert carrier gas/gases
can also be introduced with the vaporized precursor
compound/compounds during each cycle.
[0067] The reactivity of a precursor compound can significantly
influence the process parameters in ALD. Under typical CVD process
conditions, a highly reactive compound may react in the gas phase
generating particulates, depositing prematurely on undesired
surfaces, producing poor films, and/or yielding poor step coverage
or otherwise yielding non-uniform deposition. For at least such
reason, a highly reactive compound might be considered not suitable
for CVD. However, some compounds not suitable for CVD are superior
ALD precursors. For example, if the first precursor is gas phase
reactive with the second precursor, such a combination of compounds
might not be suitable for CVD, although they could be used in ALD.
In the CVD context, concern might also exist regarding sticking
coefficients and surface mobility, as known to those skilled in the
art, when using highly gas-phase reactive precursors, however,
little or no such concern would exist in the ALD context.
[0068] After layer formation on the substrate, an annealing process
may be optionally performed in situ in the deposition chamber in a
nitrogen atmosphere or oxidizing atmosphere. Preferably, the
annealing temperature is at least about 400.degree. C., more
preferably at least about 600.degree. C. The annealing temperature
is preferably no greater than about 1000.degree. C., more
preferably no greater than about 750.degree. C., and even more
preferably no greater than about 700.degree. C.
[0069] The annealing operation is preferably performed for a time
period of at least about 0.5 minute, more preferably for a time
period of at least about 1 minute. Additionally, the annealing
operation is preferably performed for a time period of no greater
than about 60 minutes, and more preferably for a time period of no
greater than about 10 minutes.
[0070] One skilled in the art will recognize that such temperatures
and time periods may vary. For example, furnace anneals and rapid
thermal annealing may be used, and further, such anneals may be
performed in one or more annealing steps.
[0071] As stated above, the use of the complexes and methods of
forming films of the present invention are beneficial for a wide
variety of thin film applications in semiconductor structures,
particularly those using high dielectric materials. For example,
such applications include gate dielectrics and capacitors such as
planar cells, trench cells (e.g., double sidewall trench
capacitors), stacked cells (e.g., crown, V-cell, delta cell,
multi-fingered, or cylindrical container stacked capacitors), as
well as field effect transistor devices.
[0072] A system that can be used to perform vapor deposition
processes (chemical vapor deposition or atomic layer deposition) of
the present invention is shown in FIG. 1. The system includes an
enclosed vapor deposition chamber 10, in which a vacuum may be
created using turbo pump 12 and backing pump 14. One or more
substrates 16 (e.g., semiconductor substrates or substrate
assemblies) are positioned in chamber 10. A constant nominal
temperature is established for substrate 16, which can vary
depending on the process used. Substrate 16 may be heated, for
example, by an electrical resistance heater 18 on which substrate
16 is mounted. Other known methods of heating the substrate may
also be utilized.
[0073] In this process, precursor compound(s) (such as the
precursor compound of Formula I) 60 and/or 61 are stored in vessels
62. The precursor compound(s) are vaporized and separately fed
along lines 64 and 66 to the deposition chamber 10 using, for
example, an inert carrier gas 68. A reaction gas 70 may be supplied
along line 72 as needed. Also, a purge gas 74, which is often the
same as the inert carrier gas 68, may be supplied along line 76 as
needed. As shown, a series of valves 80-85 are opened and closed as
required.
[0074] The following examples are offered to further illustrate
various specific embodiments and techniques of the present
invention. It should be understood, however, that many variations
and modifications understood by those of ordinary skill in the art
may be made while remaining within the scope of the present
invention. Therefore, the scope of the invention is not intended to
be limited by the following example. Unless specified otherwise,
all percentages shown in the examples are percentages by
weight.
EXAMPLES
Example 1
Synthesis and Characterization of a Homoleptic Precursor Compound
of Formula I, Where M=La, n=3, x=0,
R.sup.1=R.sup.2=CH(CH.sub.3).sub.2, E=N(CH.sub.2CH.sub.3).sub.2
[0075] In a dry box, a Schlenk flask was charged with 1.187 grams
(g) lithium diethylamide and approximately 100 milliliters (mL)
tetrahydrofuran (THF). The flask was placed under a vacuum and 2.35
mL of N,N'-diisopropylcarbodiimide was added via syringe through a
rubber septum. The solution was stirred for approximately 3 hours
(h).
[0076] A second Schlenk flask was charged in the dry box with 4.044
g LaI.sub.3(thf).sub.4 and approximately 100 mL THF and the flask
was placed under a vacuum. Lithium guanidinate solution was added
slowly to the LaI.sub.3 slurry over a period of approximately 3
hours then was stirred overnight under an argon atmosphere.
Volatiles were stripped off in vacuo and the resulting oily amber
solid was triturated with 2.times.5 mL pentane to partially remove
coordinated THF. Volatiles were stripped off after each trituration
and the solid became less oily. Also, a white solid was partially
separated from the amber material. Crude solid (6.558 g) was
collected under an argon atmosphere and charged into a sublimation
vessel. Heating to 110.degree. C. at 40 milliTorr (mTorr) produced
an off-white crystalline solid sublimate. Under these conditions,
1.510 g of material was recovered (41% yield). Characterization
data: ICP (elemental analysis)--% La found (calculated) 19.5
(18.9); TOF-MS-parent peak not seen, but the highest mass peak
(201) consistent with ligand ion mass (199) and fragment peaks
match expected fragmentation pattern of ligand; .sup.1H NMR (C6D6)
.delta.3.64 (septet, J=6.3 Hz, 6H, N--CH(CH.sub.3).sub.2), 2.97 (b,
12H, N--CH.sub.2-CH.sub.3), 1.39 (b, 36H, N--CH(CH.sub.3).sub.2),
0.98 (t, J=7 Hz, 18H, N--CH.sub.2-CH.sub.3); IR--moderate
absorption at 1620 cm.sup.-1, consistent with C.dbd.N stretching
mode.
Example 2
Synthesis and Characterization of a Heteroleptic Precursor Compound
of Formula 1, Where M=Hf, n=4, x=2,
R.sup.1=R.sup.2=CH(CH.sub.3).sub.2. E=N(CH.sub.3).sub.2,
L=N(CH.sub.3).sub.2
[0077] In a dry box, a Schlenk flask was charged with 50 mL pentane
and 7.7 mL 46% hafnium tetrakis(dimethylamide) in pentane. This
flask was adapted to a vacuum/argon manifold and 3.1 mL of
N,N'-diisopropylcarbodiimide was added dropwise at room temperature
through argon overpressure. A mild exotherm and refluxing pentane
was observed.
[0078] The reaction solution was stirred for four hours, then
volatiles were removed in vacuo, affording 5.3 g of an off-white
solid. The crude material was sublimed twice to afford a total
yield of 3.74 g of analytically pure title compound (61% yield).
The material was a white, crystalline solid.
[0079] Characterization data: ICP %Hf found (calculated) 29.8
(29.4); TOF-MS largest mass peak 569 amu, consistent with mass of
parent compound less a dimethylamide ligand, other peaks consistent
with other expected fragmentation products; .sup.1H NMR (C6D6)
.delta.3.75(b, 4H, NCH(CH.sub.3).sub.2), 3.39 (s, 12H,
HfN(CH.sub.3).sub.2), 2.52 (s, 12H. CN(CH.sub.3).sub.2), 1.28 (b,
24H, NCH(CH.sub.3).sub.2).
Example 3
Synthesis and Characterization of a Heteroleptic Precursor Compound
of Formula I, Where M=Hf, n=4, x=2,
R.sup.1=R.sup.2=CH(CH.sub.3).sub.2, E=OCH.sub.3,
L=N(CH.sub.3).sub.2
[0080] In a dry box, a Schlenk flask was charged with 200 mL
pentane and 10.2 g 52% hafnium tetrakis(dimethylamide) in pentane.
This flask was adapted to a vacuum/argon manifold and 5.5 mL of
O-methyl-N,N'-diisopropylisourea was added dropwise at room
temperature through argon overpressure. Bubbling was observed,
indicating the metathetical formation of volatile
dimethylamine.
[0081] After 16 hours, the volatiles were removed in vacuo,
affording a white paste. This crude product was sublimed at
105.degree. C. and 50 mTorr to afford a white solid sublimate (1.05
g, 12% yield). Characterization data: ICP %Hf found (calculated)
31.5 (30.7).
Example 4
Deposition of a Precursor Composition of Formula I by Atomic Layer
Deposition
[0082] The precursor from example 2 was used in a CVD process to
prepare a metal-containing layer on a bare silicon wafer substrate.
The precursor bubbler was heated to 140.degree. C., and bubbler
line to 180.degree. C. Helium carrier gas at 39 sccm was passed
over the bubbler and into the deposition chamber where the wafer
was sitting on a chuck heated to 315.degree. C. A stream of ozone
(11% by weight in molecular oxygen) at 25 sccm was simultaneously
introduced into the chamber. Both precursor and ozone were
introduced for a period of three minutes. Upon removing the
substrate from the chamber, a film was visually observed to have
formed. X-ray diffraction (XRD) analysis showed peaks at 31, 35.5,
and 51.5 degrees, indicating the formation of a
hafnium-oxide-nitride film.
[0083] The complete disclosures of the patents, patent documents,
and publications cited herein are incorporated by reference in
their entirety as if each were individually incorporated. Various
modifications and alterations to this invention will become
apparent to those skilled in the art without departing from the
scope and spirit of this invention. It should be understood that
this invention is not intended to be unduly limited by the
illustrative embodiments and examples set forth herein and that
such examples and embodiments are presented by way of example only
with the scope of the invention intended to be limited only by the
claims set forth herein as follows.
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