WO1999037655A1

WO1999037655A1 - Tantalum amide precursors for deposition of tantalum nitride on a substrate

Info

Publication number: WO1999037655A1
Application number: PCT/US1999/001277
Authority: WO
Inventors: Thomas H. Baum; Gautam Bhandari
Original assignee: Advanced Technology Materials, Inc.
Priority date: 1998-01-23
Filing date: 1999-01-21
Publication date: 1999-07-29
Also published as: KR20010040324A; GB0015192D0; GB2354762B; KR20080075561A; DE19982730T1; DE19982730C2; JP2002501075A; US6379748B1; GB2354762A; US6015917A; KR20070086743A; AU2332199A

Abstract

Tantalum and titanium source reagents are described, including tantalum amide and tantalum silicon nitride precursors for the deposition of tantalum nitride material on a substrate by processes such as chemical vapor deposition, assisted chemical vapor deposition, ion implantation, molecular beam epitaxy and rapid thermal processing. The precursors may be employed to form diffusion barrier layers on microelectronic device structures enabling the use of copper metallization and ferroelectric thin films in device construction.

Description

TANTALUM AMIDE PRECURSORS FOR DEPOSITION OF TANTALUM

NITRIDE ON A SUBSTRATE

DESCRIPTION

Field Of The Invention

The present invention relates to Ta and Ti precursors useful in the formation

of a Ta-based or Ti-based material on a substrate, and includes tantalum amide

precursors for formation of tantalum nitride on a substrate, and methods of use of

such precursors for forming TaN material, e.g., thin film layers of TaN, on a

substrate. The invention also contemplates single source compounds for the

formation of TaSiN or TiSiN material on a substrate.

Description of the Related Art

Copper is of great interest for use in metallization of VLSI microelectronic

devices because of its low resistivity, low contact resistance, and ability to enhance

device performance (relative to aluminum metallization) via reduction of RC time

delays thereby producing faster microelectronic devices. Copper CND processes

which are suitable for large-scale manufacturing and the conformal filling of high

aspect ratio inter-level vias in high density integrated circuits are extremely valuable

to the electronics industry, and are therefore being extensively investigated in the art. Although CND of Cu is gaining momentum in the semiconductor manufacturing

industry, several problems still inhibit the integration of copper metallurgy in such microelectronic device applications. In specific, CND of a suitable diffusion barrier

for the copper metallization must be available to ensure the long-term reliability of

the copper-based metallurgy in integrated circuits (ICs).

Ta and TaSiΝ have been demonstrated as a suitable metal diffusion barrier. A

CND process of TaΝ would obviously be advantageous and is currently the focus of

development efforts by semiconductor equipment manufacturers. The CND of TaΝ

is at present carried out using Ta(ΝMe2)s, ^a solid source precursor, as the source

reagent. However, Ta(NMe2)5 is a solid, and given the limited volatility of

Ta( Me2)5, new, robust and more volatile tantalum amide precursors are needed.

The films deposited from such sources must be conducting, conformal and of high

purity. It would be extremely advantageous to utilize a suitable liquid source reagent

as a tantalum amide precursor. For example, an alternative TaN precursor is

Ta(NEt₂)₅, which is reportedly a liquid. However, this source reagent is unstable to

elevated temperature conditions, readily decomposing to a tantalum imide species,

Ta(NEt)(NEt₂)3, upon heating, and thereby is an unsatisfactory candidate as a liquid

source reagent for TaN barrier layer formation.

TaSiN and TiSiN are also currently being investigated in the art as diffusion

barriers. A CND process for these ternary barrier layer materials would also be

advantageous and also is the focus of development efforts in the field. The CND of TaSiN is at present carried out using Ta(NMβ2)s as the Ta source and silane as the

silicon source. Further, TaCl₅ in combination with silane and ammonia has been

used to deposit TaSiN thin films. Apart from the hazards associated with handling a

pyrophoric gas such as silane, the dual source reactor configuration required with

such precursor species (TaCl₅, Ta(NMe2)s and silane) also increases the cost and

complexity of the semiconductor manufacturing operation.

Another approach to barrier layer formation entails the PND or CND

deposition of high purity Ta metal on the silicon substrate. The resulting Ta layer

will form TaSi_x at the silicon contact region (i.e., the Ta bottom surface), and

subsequent elevated temperature reaction of the Ta layer with a nitrogenous reactant

such as ΝH3 or N2 will induce nitridation of the Ta top-surface. Thus, a TaSiN

ternary diffusion barrier or a layered TaSi / TaN structure can be formed. This type

of ternary diffusion barrier has been reported in the art and provides excellent

contact resistance and diffusion barrier properties towards Cu metallization and

integration of ferroelectric thin films.

In all instances of the formation of a Ta-based diffusion barrier, an effective

CND approach to conformally coat inter-level (< 0.15 μm) vias and sidewalls is

critical, and the CVD source reagent must be storage-stable, of appropriate volatility

and vaporization characteristics, with good transport and deposition characteristics

to produce a high-purity, electronic quality thin film. There is a continuing and increasing need in the art for improved CVD

source reagents for forming Ta-based diffusion barrier layers on microelectronic

substrates, to facilitate copper metallization. Such CND source reagents are

desirably liquid in character, to facilitate their processibility using techniques such as

liquid delivery CVD, wherein the liquid source reagent is rapidly vaporized, e.g., by

flash vaporization on a heated element such as a grid, screen or porous metal body,

to produce a volatilized source reagent. The resulting source reagent vapor can then

be transported to the CND chamber and contacted with a substrate maintained at

appropriate elevated temperature, to effect the deposition on the substrate of the Ta- based material.

It therefore is an object of the present invention to provide useful precursor

compositions for the formation of Ta-based material and Ti-based material on

substrates.

It is another object of the invention to provide a method of forming a Ta-

based material, such as TaΝ or TaSiΝ, or a Ti-based material, such as TiΝ or TiSiΝ,

on a substrate, using such precursor compositions.

Other objects and advantages of the present invention will be more fully

apparent from the ensuing disclosure and appended claims.

SUMMARY OF THE INVENTION The present invention relates generally to tantalum and titanium source

reagents for the formation of Ta-based and Ti-based materials on a substrate by

techniques such as chemical vapor deposition, and in particular and preferred

practice of the invention, liquid delivery chemical vapor deposition.

As used herein, the term "liquid delivery" when referred to chemical vapor

deposition or other thin film or coating process refers to the fact that the precursor or

source reagent composition for the material to be deposited on a substrate is

vaporized from a liquid form to produce a corresponding precursor vapor which then

is transported to the locus of deposition, to form the material film or coating on the substrate structure. The liquid phase which is vaporized to form the precursor vapor

may comprise a liquid-phase source reagent per se, or the source reagent may be

dissolved in or mixed with a liquid to facilitate such vaporization to place the source

reagent in the vapor phase for the deposition operation.

As used herein, the term "perfluoroalkyl" is intended to be broadly construed

to include groups containing alkyl moieties which are partially or fully substituted in

fluorine atoms, and thus perfluoroalkyl includes for example a trifluoroalkyl

substituent whose alkyl moiety is Cι.C₄ alkyl, such as trifluoromethyl. In one compositional aspect, the present invention relates to a precursor

composition comprising at least one tantalum and/or titanium species selected from

the group consisting of:

(i) tethered amine tantalum complexes of the formula:

R!

NR4R5

NR4R₅

wherein:

X is 2 or 3; each of Rι-R₅ is independently selected from the group consisting of H, Ci-

C₄ alkyl, aryl (e.g, phenyl), Ci.C₆ perfluoroalkyl (e.g., a trifluoroalkyl substituent

whose alkyl moiety is C].C₄ alkyl, such as trifluoromethyl), and trimethylsilyl;

(ii) β-diimines of the formula:

TaG_xQ₅._x wherein:

G is a β-diimino ligand;

each Q is selected from the group consisting of H, Cι-C₆ alkyl, aryl and .C_o perfluoroalkyl; and

x is an integer from 1 to 4 inclusive;

(iii) tantalum diamide complexes of the formula

Ta(N(R₁)(CH₂)_xN(R₂))_y(NR₃R₄)₅._2y

wherein:

x is 1 or 2;

y is 1 or 2; each of R_!-R- is independently selected from the group consisting of H, -

C₄ alkyl, aryl, perfluoroalkyl, and trimethylsilyl;

(iv) tantalum amide compounds of the formula

Ta(NRR')₅ wherein each R and R' is independently selected from the group consisting of

H, d.C₄ alkyl, phenyl, perfluoroalkyl, and trimethylsilyl, subject to the proviso that

in each NRR' group, R • R';

(v) β-ketoimines of the formula Rb

Ra Re

Rd. / Rd R2

wherein each of R], R₂, R_a, R_b, R_c and R_d is independently selected from H,

aryl, Cι-C₆ alkyl, and Cι-C₆ perfluoroalkyl; and

(v) tantalum cyclopentadienyl compounds of the formula:

wherein each R is independently selected from the group consisting of H,

methyl, ethyl, isopropyl, t-butyl, trimethylsilyl;

(vii) Ta(NRιR₂)χ(NR₃R4)5-χ / Ti(NR₁R₂)_x(NR₃R4)4-x

or Ta(NRι)(NR₂R₃)3 where each of Ri, R₂, R₃ and R₄ are independently selected from the group

consisting of H, Ci-Cg alkyl (e.g., Me, Et, 'Bu, 'Pr, etc.), aryl (e.g., phenyl), Cι-C₈

perfluoroalkyl (e.g., CF3 or a fluoroalkyl whose alkyl moiety is Cι-C₄, such as

trifluoromethyl), or a silicon-containing group such as silane (SiH3), alkylsilane,

(e.g., SiMe₃, Si(Et)₃, Si(iPr)₃, SiCBu)₃, perfluoroalkylsilyl (e.g., Si(CF₃)₃),

triarylsilane (e.g,, Si(Ph)3), or alkylsilylsilane (e.g., Si(SiMe3)_x(Me)3__x);

(viii) Ta(SiRιR₂R3)χ(NR₄R5)5-χ Ti(SiR₁R₂R₃)_x(NR₄R5)4-x

where R1.5 can any be combination of H, Me, Et, 'Bu, Ph, 'Pr, CF3, SiH₃, SiMe3,

Si(CF₃)₃, Si(Et)₃, Si(ⁱPr)₃, Si(^tβu)₃, Si(Ph)₃, and Si(SiMe₃)_x(Me)₃._x; and

(ix) (Cpn)Ta(SiRιR₂R3)x(NR₄R₅)4-x / (Cpn)2Ti(SiRιR2R₃)(NR₄R5)

where R1.5 can any be combination of H, Me, Et, ^lBu, Ph, 'Pr, CF₃, SiH₃, SiMe₃,

Si(CF₃)₃, Si(Et)₃, Si(ⁱPr)₃, Si(<Bu)₃, Si(Ph)₃, Si(SiMe₃)_x(Me)₃._x and Cp" is

C5H_xMe₍5__x) (where x = 0-5).

In one aspect, the present invention relates to tantalum amide precursors for

formation of tantalum nitride on a substrate, and to methods of forming TaN

material on a substrate from such precursors, wherein the precursor composition

comprises at least one tantalum species selected from the group consisting of: (i) tethered amine tantalum complexes of the formula:

Ri

NR4R5

wherein:

X is 2 or 3;

each of RrR₅ is independently selected from the group consisting of H, C\-

C₄ alkyl, aryl (e.g, phenyl), C].C₆ perfluoroalkyl (e.g., a trifluoroalkyl substituent

whose alkyl moiety is Cj.C₄ alkyl, such as trifluoromethyl), and trimethylsilyl;

(ii) β-diimines of the formula:

TaG_xQ₅._x wherein:

G is a β-diimino ligand;

each Q is selected from the group consisting of H, Cι-C₆ alkyl, aryl and CμC₆

perfluoroalkyl; and

10 x is an integer from 1 to 4 inclusive;

(iii) tantalum diamide complexes of the formula

Ta(N(R₁)(CH₂)_xN(R₂))_y(NR₃R₄)₅._2y wherein:

x is 1 or 2;

y is 1 or 2;

each of R]-R-₄ is independently selected from the group consisting of H, Ci-

C₄ alkyl, aryl, perfluoroalkyl, and trimethylsilyl;

(iv) tantalum amide compounds of the formula

H, CμC₄ alkyl, phenyl, perfluoroalkyl, and trimethylsilyl, subject to the proviso that

in each NRR' group, R . R';

(v) β-ketoimines of the formula

11

wherein each of Ri, R₂, R_a, R_b, R_c and Rd is independently selected from H,

aryl, Cι-C₆ alkyl, and Cι-C perfluoroalkyl; and

(vi) tantalum cyclopentadienyl compounds of the formula

wherein each R is independently selected from the group consisting of H,

methyl, ethyl, isopropyl, t-butyl, trimethylsilyl.

In another aspect, the present invention relates to a tantalum amide precursor

composition for forming a tantalum nitride material on a substrate, including at least

one tantalum amide species selected from the above-described selection group, and a

solvent for such tantalum amide species. The solvent may be selected from the

group consisting of C₆-C₁₀ alkanes, C₆-C₁₀ aromatics, and compatible mixtures

12 thereof. Illustrative alkane species include hexane, heptane, octane, nonane and

decane. Preferred alkane solvent species include C₈ and Cio alkanes. Preferred

aromatic solvent species include toluene and xylene. In the most preferred approach,

no solvent is required to deliver the liquid source reagents.

In another aspect, the invention relates to a method of forming a tantalum

nitride material on a substrate from a precursor composition therefor, including the

steps of vaporizing the precursor composition to form a precursor vapor and

contacting the precursor vapor with a substrate under deposition conditions to

deposit on the substrate the tantalum nitride material, wherein the tantalum nitride

precursor composition comprises at least one tantalum amide species selected from

the above-described selection group of tantalum compounds and complexes, in a

solvent for the tantalum amide species.

The tantalum nitride precursor composition thus may be provided as a liquid

composition, which is delivered to a vaporizer to effect vaporization and formation

of the tantalum nitride precursor vapor, with the vapor being transported to a

deposition zone containing the substrate for the formation of the tantalum nitride

material on the substrate. The formation of tantalum nitride material on the substrate

may be carried out by a deposition process such as chemical vapor deposition,

assisted chemical vapor deposition, ion implantation, molecular beam epitaxy and

rapid thermal processing.

13 Other aspects and features of the invention will be more fully apparent from

the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a Thermal Gravimetric Analysis (TGA) plot comparing the

volatility of Ta(NMeEt)₅ with Ta(NEt)(NEt₂)₃ and Ta(NMe)₅.

Figure 2 is an STA plot of Ta(NMeEt)₅.

Figure 3 is a 1H and ¹³C NMR plot for Ta(NMeEt)₅ showing five equivalent

amide groups.

DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED

EMBODIMENTS THEREOF

The present invention is based on the discovery of highly advantageous Ta

and Ti source reagents, including Ta source reagents useful for forming Ta-based

barrier layers on substrates such as microelectronic device structures for applications

such as copper metallization of semiconductor device structures.

14 The Ta source reagents of the invention include TaN source reagents including Ta amides, as well as single source precursors that are advantageous for

the deposition of TaSiN and TiSiN in which silicon is incorporated at the molecular

level into the precursor.

In the provision of Ta amide precursors for the formation of TaN barrier

layers, useful precursors include tantalum amide precursor compositions comprising

at least one tantalum amide species selected from the group consisting of:

(i) tethered amine tantalum complexes of the formula:

Ri

NR4R5

wherein:

X is 2 or 3;

15 each of Rι-R₅ is independently selected from the group consisting of H, Cj-

C₄ alkyl, aryl (e.g, phenyl), Cι.C₆ perfluoroalkyl (e.g., a trifluoroalkyl substituent

whose alkyl moiety is Cι_C₄ alkyl, such as trifluoromethyl), and trimethylsilyl;

(ii) β-diimines of the formula:

TaG_xQ₅._x

wherein:

G is a β-diimino ligand;

each Q is selected from the group consisting of H, Cι-C₆ alkyl, aryl and Cι_C

perfluoroalkyl; and

x is an integer from 1 to 4 inclusive;

(iii) tantalum diamide complexes of the formula

Ta(N(R (CH₂)_xN(R₂))_y(NR₃R₄)₅._2y

wherein:

x is 1 or 2;

y is 1 or 2; each of RrR-₄ is independently selected from the group consisting of H, Ci-

C alkyl, aryl, perfluoroalkyl, and trimethylsilyl;

(iv) tantalum amide compounds of the formula

16 Ta(NRR')₅

wherein each R and R' is independently selected from the group consisting of

H, Ci_C alkyl, phenyl, perfluoroalkyl, and trimethylsilyl, subject to the proviso that

in each NRR' group, R • R';

(v) β-ketoimines of the formula

Ro

wherein each of Rj, R₂, R_a, R_b, R_c and Ra is independently selected from H, aryl, Ci-

C₆ alkyl, and Cι-C perfluoroalkyl; and

(vi) tantalum cyclopentadienyl compounds of the formula

17 wherein each R is independently selected from the group consisting of H,

methyl, ethyl, isopropyl, t-butyl, trimethylsilyl.

For the growth of TaN barrier layers it is desirable that the precursors be free

of oxygen so that the formation of tantalum oxide is avoided. Tantalum amides,

which have preexisting Ta-N bonds, are therefore attractive precursors. However,

homoleptic tantalum amides such as Ta(NMe2)s suffer from reduced volatility, due

to the bridging of multiple metal centers through the -NMe2 group, analogous to that

observed for Ta(OEt)5.

The present invention enhances the volatility of tantalum amides by limiting the degree of intermolecular interactions. To thwart such interactions the use of

tethered amine ligands may be employed. For instance, substitution of one of the -

NMe2 groups with -N(CH₃)(CH2CH2)-NMe2 gives the tantalum amide composition

of formula I below, a monomer, with a stable five-membered metallacycle structure.

A variety of tethered ligands may be similarly employed. Ligand species of the

general formula RιN(CH2)_xNR2R₃ where Ri, R2, R₃ can be independently chosen

from H, Me, Et, ^lBu, Ph, 'Pr, CF₃ or SiMe₃ groups, appropriately selected to

maximize volatility, are preferred. X can be 2 or 3 so that stable 5 or 6 membered

chelating rings result.

18 R4R5

Ri

/

N, NR4R5

7 ^ I7 ^ R₄R₅ R₂ R3 NR₄R₅

The use of β-diimmines offers alternative precursor compositions that

maximize volatility and minimize detrimental exchange reactions. For instance,

Ta(nacnac)(NMe2)₄ (directly analogous to Ta(OiPr)5(thd)) is illustrative of

precursors of such type that may be usefully employed for the deposition of TaN

diffusion barriers. In complexes of the formula Ta(RιN-C(R2)-CH-C(R₃)-

N(R4))_X(NR5R6)5__X, formula (II) below, R - R(, can each be independently selected

from substituent species such as H, Me, Et, ^lBu, Ph, 'Pr, SiMe₃, and CF₃.

NR₅R₆

NR₅R₆

II

Alternatively, the TaN precursor may utilize diamide ligands such as

N(Rι)(CH2)_xN(R2) to form mixed ligand complexes such as those of the formula

19 Ta(N(Rι)(CH₂)_xN(R₂))_x(NR₃R₄)5-2_X, formula (III) below, in which each of R^

can be independently selected from substituents such as H, Me, Et, 'Bu, Ph, 'Pr,

SiMe3, and CF3 groups.

NR₃R₄

Pi

_N / — τ N—

R₂

III

In a simple form, unsymmetrical amides can be employed to thwart

intermolecular interactions and disrupt crystal packing forces. Thus, a suitable

precursor could be Ta(NRR')s where R and R' can be any combination of H, Me, Et,

^lBu, Ph, 'Pr, SiMe3, CF3_, Ph, Cy but R^» R'. As used herein, the term Ph denotes

phenyl, and Cy denotes cycloalkyl.

The aforementioned precursors of the present invention provide Ta source

reagents that have beneficial volatility characteristics for applications such as

chemical vapor deposition, and are easily and economically synthesized. The Ta

source reagents of the invention utilized molecular geometries that are controlled by

subtle steric effects.

20 As an example of such subtle steric effects, Ta(NMe₂)s reportedly possesses

a square pyramidal structure and therefore possess a vacant coordination site useful

for coordination to other metal centers via a bridging -NMe2 group, analogous to

that observed for Ta(OEt)5. Ta(NMe2)s therefore is a solid and suffers from reduced

volatility. Increasing the steric bulk of the ligand by replacement of the -NMe2 by -

NE-2 results in a trigonal bipyramidal compound, Ta(NEt₂)s, due to the increased

steric bulk of the ethyl group compared to the methyl groups in Ta(NMβ2)5. Since

trigonal bipyramidal compounds have no free coordination site Ta(NEt2)s is a liquid

but it is unstable to heat.

In order to enhance the volatility of the complex by altering the geometry

around the metal center to trigonal bipyramidal, without adding undue steric bulk,

Ta(NMeEt)₅ was synthesized. Ta(NMeEt)s is:

(i) a liquid.

(ii) more volatile than Ta(NMe₂)s or Ta(NEt)(NEt₂)3 (see Fig. 1).

(iii) stable to heat up to its boiling temperature (see Fig. 2).

These properties make Ta(NMeEt)5 a highly desirable precursor for CVD

that is superior to the prior art, as shown in Figure 1, which is a thermal gravimetric

analysis (TGA) plot comparing the volatility of Ta(NMeEt)5 vs. Ta(NEt)(NEt₂)3 and

Ta(NMe)₅.

21 Figure 2 shows an STA plot of Ta(NMeEt)5. Note there is no event in the

differential scanning calorimetry (DSC) curve prior to boiling, indicating stability to

decomposition.

Figure 3 shows an ^lH and ¹³C NMR plot of Ta(NMeEt)5 showing five

equivalent amide groups.

In the Ta amide precursors of the invention, the Ta substituents preferably

include substituents having slightly increased steric size than -NMe₂. Such Ta amide precursors include compounds of the general formula Ta(NRιR2)s, wherein

R_l and R2 are independently selected from substituents such as -H, -Me, -Et, -

CH₂CH(Me)-, -CF₃, -*Bu, -'Pr, and SiMe₃.

In the broad practice of the present invention, other compounds of the

general formula Ta(NRιR2)₃(NR2R₃)2 can also be optimized for volatility and

stability. In such precursor compositions, the steric size of -NR1R2 > -NR2R₃ so

that the more bulky -NR1R2 group occupies the axial position and the -NR2R₃ group

occupies the more sterically crowded equatorial position. In these compositions, Rι_

₄ can be selected from any combination of -H, -Me, -Et, -CH₂CH(Me)-, -CF₃₍ -'Bu, -

'Pr, and -SiMe₃.

22 The deposition of Ta metal in accordance with the process of the present

invention may be carried out with a wide variety of precursor materials of the types

disclosed herein. In some cases, it may be detrimental to have an oxygen containing

ligand present in the molecule which could ultimately result in Ta2θ3 formation. In

such instances, the use of β-ketoimine or β-diimine ligands, such as those described

below, enables highly efficient chemical vapor deposition of TaN and Ta metal.

In compound I, Ri, R2, R3 and R₄ may be alike or different and are

independently selected from substituents such as H, aryl, Ci - C6 alkyl, and Ci - Cg

perfluoroakyl. In a specific embodiment, R₃ will most likely be H, aryl, Ci - C

alkyl, or Ci - C perfluoroalkyl. Alternatively, Ri or R₂ may be identical to R3. R_a,

R , and R_c may be alike or different and are independently selected from the group

consisting of H, aryl, Ci - C(, alkyl, or C_\ - C(, perfluoroalkyl.

23 Rb Ra. Re

II

In compound II, Ry and R2 may have the same restrictions as discussed above for

compound I. R_a> R^ and R_Cι may be equal or different and can be H, aryl,

perfluoroaryl, Ci - Cg alkyl, or Ci - Cξ, perfluoroalkyl.

Various trimethyl tantalum bis(β-diketonate) complexes may be employed as

useful Ta precursors in the broad practice of the invention. For example,

Me₃Ta(acac)2 has a melting point of 83°C, Me₃Ta(tfac)2 has a melting point of 107

°C and Me₃Ta(hfac)2 has a melting point of 109 °C. The volatility generally

increases in the same order with increasing fluorine substitution. These types of

materials are potentially usefully employed for Ta film growth in the presence of

hydrogen, forming gas or other reducing species. They may also be usefully

employed for oxide formation, as for example in CVD of SrBi₂Ta2θ9.

A third class of materials that is potentially usefully employed for the

deposition of Ta metal or TaN films has a hydride precursor structure, as depicted in

compound III below. Such compositions have not previously been used for Ta or

TaN film growth.

24 R-

Ta— H

III Bis (cyclopentadienyl) tantalum (V) trihydride

The structure of this Ta precursor may be altered to enhance thermal stability,

volatility or physical properties and to achieve the desired film properties, namely

high purity and low resistivity. Potential substituents where R on the

cyclopentadienyl moiety is varied include R=H, Me, Et, i-Pr, t-Bu, TMSi, etc. in

which the substituent is selected to modify the precursor properties. This general

class of materials is well-suited for Ta film growth especially in the presence of H2

or forming gas.

In use, the precursors of the invention may be employed in a neat liquid

form, or alternatively they may be utilized in solution or suspension form, in which

the precursor is mixed, blended or suspended in a compatible liquid solvent such as a solvent composition of the type disclosed in U.S. Application Serial No.

08/414,504 filed March 31, 1995, in the names of Robin A. Gardiner, Peter S.

Kirlin, Thomas H. Baum, Douglas Gordon, Timothy E. Glassman, Sofia Pombrik,

and Brian A. Vaartstra, the disclosure of which is hereby incorporated herein by

reference in its entirety.

25 The solvent may for example be selected from the group consisting of C -Cιo

alkanes, C₆-Cιo aromatics, and compatible mixtures thereof. Illustrative alkane

species include hexane, heptane, octane, nonane and decane. Preferred alkane

solvent species include C₈ and Cio alkanes. Preferred aromatic solvent species

include toluene and xylene.

The present invention also contemplates various single source precursors for the formation of TaSiN and TiSiN layers on substrates. Two general variant

approaches can be used for the provision of single source precursors that are

advantageous for the deposition of TaSiN and TiSiN. These approaches are:

(1) use of silyl amides as precursors; and (2) provision of direct metal-silicon bonds in the precursors.

Metal silylamides represent the most direct and cost-effective method for the

introduction of silicon into the product film formed by the precursor. Examples

include the clean formation of Bii2SiO20 upon heating Bi(NSiMe₃)₃ in oxygen. For

the deposition of TaSiN and TiSiN suitable precursors include those of the general

formula:

Ta(NRιR₂)_x(NR₃R₄)₅-x / Ti(NRιR₂)χ(NR₃R₄)4-χ

26 or

Ta(NRι)(NR₂R₃)₃

where each of Ri, R₂, R₃ and R₄ are independently selected from the group

consisting of H, Cι-C₈ alkyl (e.g., Me, Et, ^lBu, 'Pr, etc.), aryl (e.g., phenyl), Cι-C₈

perfluoroalkyl (e.g., CF3 or a fluoroalkyl whose alkyl moiety is Cι-C , such as

(e.g., SiMe₃, Si(Et)₃, Si('Pr)₃, Si(^lBu)₃, perfluoroalkylsilyl (e.g., Si(CF₃)₃),

triarylsilane (e.g,, Si(Ph)3), or alkylsilylsilane (e.g., Si(SiMe3)_x(Me)3__x). The

number of silicon-containing R groups can be used as an independent variable to

control the amount of silicon in the film. For precursors of the type

Ta(NRι)(NR2R3)3 the location of the R group (i.e., imide vs. amide) will also

determine the incorporation efficiency of silicon into the film.

Precursors containing preexisting metal to silicon bonds are potentially highly

effective for the deposition of TaSiN/TiSiN. Useful precursors have the general

formula:

Ta(SiRιR₂R3)χ(NR₄R5)5-x / Ti(SiR₁R₂R3)χ(NR₄R5)4-x

where R₁.5 can any be combination of H, Me, Et, ^lBu, Ph, 'Pr, CF3, SiH3, SiMe3,

Si(CF₃)₃, Si(Ef)3, Si('Pr)₃, SiCBu)₃, Si(Ph)₃, Si(SiMe₃)_x(Me)₃__x. Two illustrative

27 titanium amides with metal to silicon bonds are Ti(Si(SiMe3)3)(NMe₂)3 and

Ti(Si(SiMe₃)3)(NEt₂)3.

Another class of useful precursors are complexes where one of the amide or silyl

groups has been replaced by a cyclopentadiene or substituted cyclopentadiene.

These precursors have the general formula;

(Cpn)Ta(SiRιR₂R3)χ(NR₄R5)4-x / (Cpn)₂Ti(SiRιR₂R3)(NR4R5)

where, once again, R₁.5 can any be combination of H, Me, Et, ^£Bu, Ph, 'Pr, CF3,

SiH₃, SiMe₃, Si(CF₃)₃, Si(Et)₃, Si(Ψr)₃, Si(^tβu)₃, Si(Ph)₃, Si(SiMe₃)_x(Me)₃._x and

Cpⁿ is C5H_xMe₍5__x) (where x = 0-5). Cyclopentadienyl complexes of Ta and Ti

containing direct metal to silicon bonds have not heretofore been used or considered

for formation of TaN, TiN, TaSiN or TiSiN films.

For liquid delivery CVD of Ta- or Ti-based films or coatings on a substrate,

the corresponding source reagent may be provided as a liquid starting material which

then is vaporized to form the precursor vapor for the chemical vapor deposition

process.

The vaporization may be carried out by injection of the liquid in fine jet, mist

or droplet form into a hot zone at an appropriate temperature for vaporization of the

source reagent liquid. Such injection may be carried out with a nebulization or

atomization apparatus of conventional character, producing a dispersion of finely

28 divided liquid particles, e.g., sub-micron to millimeter diameter scale. The dispersed

liquid particles may be directed at a substrate at a sufficiently high temperature to

decompose the source reagent and produce a coating of the Ta- or Ti-based material product on the substrate.

Alternatively, the liquid may be dispensed from a suitable supply vessel of

same, onto a heated element, such as a screen, grid or other porous or foraminous

structure, which is heated to a sufficiently high temperature to cause the liquid to

flash volatilize into the vapor phase, as for example in the manner described in U.S.

Patent 5,204,314 to Peter S. Kirlin, et al. and U.S. Patent 5,711,816 to Peter S.

Kirlin, et al., the disclosures of which hereby are incorporated herein by reference in

their entirety.

Regardless of the manner of volatilization of the source reagent, the vapor

thereof is flowed to contact the substrate on which the Ta-based or Ti-based material

is to be deposited, at appropriate deposition conditions therefor, which may be

readily determined within the skill of the art, by the expedient of varying the process

conditions (temperature, pressure, flow rate, etc.) and assessing the character and

suitability of the resulting deposited material.

As an alternative to the use of the source reagent in a neat liquid form, the

source reagent may be dissolved or mixed into a compatible solvent medium which does not preclude the efficacy of the resulting composition for CVD usage. For

29 example, the source reagent may be utilized in a solvent composition of the type

disclosed in the aforementioned U.S. Application Serial No. 08/414,504 filed March

31, 1995, in the names of Robin A. Gardiner, et al. The resulting solution or

suspension of the source reagent and solvent medium may then be injected,

dispersed, flash vaporized, or otherwise volatilized in any suitable manner, as for

example by the techniques described above in connection with the use of the neat

liquid source reagent.

Industrial Applicability

The present invention provides tantalum and titanium precursors useful for forming

corresponding tantalum-containing and titanium-containing films on substrates. The tantalum precursors include tantalum amides, which may be used to form tantalum

nitride films. The invention also provides single source precursor compounds for

forming TaSiN and TiSiN on a substrate. The invention therefore provides metal

nitride films useful as diffusion barrier layers in microelectronic device structures.

30

Claims

THE CLAIMS

1. A source reagent composition comprising at least one tantalum and/or titanium species selected from the group consisting of:

(i) tethered amine tantalum complexes of the formula:

Ri

_N NR4R5

NR4R5

(CH₂)_X Ta

NR4R5

N NR4R5

R2 R3

wherein:

x is 2 or 3;

each of R╬╣-R₅ is independently selected from the group consisting of H, Cj- C₄ alkyl, aryl, C╬╣.C₆ perfluoroalkyl and trimethylsilyl;

(ii) ╬▓-diimines of the formula:

31 TaG_xQ₅._x

wherein:

G is a ╬▓-diimino ligand;

each Q is selected from the group consisting of H, C╬╣-C alkyl, aryl and C╬╣_C₆ perfluoroalkyl; and

x is an integer from 1 to 4 inclusive;

(iii) tantalum diamide complexes of the formula

Ta(N(R,)(CH₂)_xN(R₂))_y(NR₃R₄)₅._2y wherein:

x is 1 or 2;

y is 1 or 2;

each of R╬╣-R₄ is independently selected from the group consisting of H, Ci-

C₄ alkyl, aryl, perfluoroalkyl, and trimethylsilyl;

(iv) tantalum amide compounds of the formula

Ta(NRR')s wherein each R and R' is independently selected from the group consisting of

H, Ci_C₄ alkyl, phenyl, perfluoroalkyl, and trimethylsilyl, subject to the proviso that

in each NRR' group, R ΓÇó R';

32 (v) ╬▓-ketoimines of the formula

Rb

Ra Re

Rd Rd

Ta-

^ΓûáN. ^ΓÇó R₂

Ri / \

O O

Ri

R2

wherein each of Ri, R₂, R_a, Rb, Re and Rd is independently selected from H,

aryl, C╬╣-C₆ alkyl, and C╬╣-C₆ perfluoroalkyl; and

(vi) tantalum cyclopentadienyl compounds of the formula:

wherein each R is independently selected from the group consisting of H,

methyl, ethyl, isopropyl, t-butyl, and trimethylsilyl;

(vii) Ta(NR₁R₂)_x(NR₃R₄)₅._x / Ti(NR╬╣R₂)_x(NR₃R₄)₄._x

where each of Ri, R , R₃ and R are independently selected from the group

consisting of H, C╬╣-C₈ alkyl, aryl, C]-C₈ perfluoroalkyl or a silicon-containing group

33 selected from the group consisting of silane, alkylsilane, perfluoroalkylsilyl,

triarylsilane and alkylsilylsilane;

(viii) Ta(NR╬╣ )(NR₂R₃)₃

where each of Rj, R₂, and R₃ are independently selected from the group consisting of H, Ci-Cg alkyl, aryl, C╬╣-C₈ perfluoroalkyl or a silicon-containing group selected

from the group consisting of silane, alkylsilane, perfluoroalkylsilyl, triarylsilane and

alkylsilylsilane;

(ix) Ta(SiR╬╣R₂R₃)_x(NR₄R5)5-╧ç / Ti(SiR╬╣R₂R₃)╧ç(NR₄R5)4-_x

where each of R₁.5 is independently selected from the group consisting of H, Me, Et,

^lBu, Ph, 'Pr, CF₃, SiH₃, SiMe₃, Si(CF₃)₃, Si(Et)₃, Si('Pr)₃, Si(^lBu)₃, Si(Ph)₃, and

Si(SiMe₃)_x(Me)₃._x; and

(x) (Cpn)Ta(SiR╬╣R₂R₃)_x(NR₄R5) -╧ç / (Cpn)₂Ti(SiR╬╣R₂R₃)(NR₄R₅)

where each of R1.5 is independently selected from the group consisting of H, Me, Et,

┬½Bu, Ph, ⁱPr, CF₃, SiH₃, SiMe₃, Si(CF₃)₃, Si(Et)₃, Si('Pr)₃, Si('Bu)₃, Si(Ph)₃,

Si(SiMe₃)_x(Me)₃._x and Cpⁿ is C5H_xMe₍5__x) (where x = 0-5).

2. A source reagent composition according to claim 1, further

comprising a solvent for said tantalum and/or titanium species.

34

3. A source reagent composition according to claim 2, wherein said

solvent is selected from the group consisting of C₆-C╬╣₀ alkanes, C₆-C╬╣₀ aromatics,

and compatible mixtures thereof.

4. A source reagent composition according to claim 2, wherein said

solvent is selected from the group consisting of hexane, heptane, octane, nonane,

decane, toluene and xylene.

5. A method of forming Ta or Ti material on a substrate from a

precursor, comprising vaporizing said precursor to form a precursor vapor, and

contacting the precursor vapor with the substrate to form said Ta or Ti material

thereon, wherein the precursor comprises at least one tantalum and/or titanium

species selected from the group consisting of:

(i) tethered amine tantalum complexes of the formula:

35 Rt

NR4R5

(CH₂)_X Ta

N f fR₄R₅ NR4R5

R- R,

wherein:

x is 2 or 3;

each of R╬╣-R₅ is independently selected from the group consisting of H, Ci- C₄ alkyl, aryl, C╬╣_C₆ perfluoroalkyl and trimethylsilyl;

(ii) ╬▓-diimines of the formula:

TaG_xQ₅.

wherein:

G is a ╬▓-diimino ligand;

each Q is selected from the group consisting of H, C╬╣-C₆ alkyl, aryl and C╬╣_C₆

perfluoroalkyl; and

x is an integer from 1 to 4 inclusive;

(iii) tantalum diamide complexes of the formula

36 Ta(N(R,)(CH₂)_xN(R₂))_y(NR₃R₄)₅._2y wherein:

x is 1 or 2;

y is 1 or 2;

each of R╬╣-R₄ is independently selected from the group consisting of H, -

C₄ alkyl, aryl, perfluoroalkyl, and trimethylsilyl;

(iv) tantalum amide compounds of the formula Ta(NRR')₅

wherein each R and R' is independently selected from the group consisting of

in each NRR' group, R ΓÇó R';

(v) ╬▓-ketoimines of the formula

Rb

Ra. .Re

Rd- / ^Rd

37 wherein each of Rj, R₂, R_a, R_b, R_c and R is independently selected from H. aryl, C╬╣-C₆ alkyl, and C╬╣-C₆ perfluoroalkyl; and

(vi) tantalum cyclopentadienyl compounds of the formula

wherein each R is independently selected from the group consisting of H,

methyl, ethyl, isopropyl, t-butyl, and trimethylsilyl;

(vii) Ta(NR₁R₂)_x(NR₃R₄)₅-╧ç / Ti(NR₁R₂)_x(NR₃R₄)₄. X

where each of Ri, R , R₃ and R₄ are independently selected from the group

consisting of H, C╬╣-C₈ alkyl, aryl, C╬╣-C₈ perfluoroalkyl or a silicon-containing group

selected from the group consisting of silane, alkylsilane, perfluoroalkylsilyl.

triarylsilane and alkylsilylsilane;

(viii) Ta(NR╬╣)(NR₂R₃)₃

where each of Ri, R₂, and R₃ are independently selected from the group consisting of

H, C╬╣-C₈ alkyl, aryl, C╬╣-C₈ perfluoroalkyl or a silicon-containing group selected

alkylsilylsilane;

38 (ix) Ta(SiR╬╣R₂R₃)_x(NR₄R₅)5-╧ç / Ti(SiR₁R₂R₃)_x(NR₄R₅)₄__x

^tBu, Ph, 'Pr, CF₃, SiH₃, SiMe₃, Si(CF₃)₃, Si(Et)₃, Si('Pr)₃, Si('Bu)₃, Si(Ph)₃, and

Si(SiMe₃)_x(Me)₃__x; and

(x) (Cpn)Ta(SiR╬╣R₂R3)x(NR₄R₅)4-x / (Cpn)₂Ti(SiR╬╣R2R3)(NR₄R5)

^tBu, Ph, iPr, CF₃, SiH₃, SiMe₃, Si(CF₃)₃, Si(Et)₃, Si(╬ªr)₃, SiOBu)₃, Si(Ph)₃,

Si(SiMe3)_x(Me)₃._x and Cpⁿ is CsH_xMe₍5._x) (where x = 0-5).

6. A method according to claim 5, wherein said material formed on the

substrate is TaN, and the precursor is selected from the group consisting of:

(i) tethered amine tantalum complexes of the formula:

39 Ri

N NR4R₅

NR4R5

(CH₂)_X Ta

NR₄R

N NR₄R₅

R- R,

wherein:

X is 2 or 3;

each of R╬╣-R₅ is independently selected from the group consisting of H, Ci-

C₄ alkyl, aryl, C╬╣_C₆ perfluoroalkyl, and trimethylsilyl;

(ii) ╬▓-diimines of the formula:

TaG_xQ₅._x

wherein:

G is a ╬▓-diimino ligand;

each Q is selected from the group consisting of H, C╬╣-C₆ alkyl, aryl and C╬╣.C₆

perfluoroalkyl; and

x is an integer from 1 to 4 inclusive;

(iii) tantalum diamide complexes of the formula

40 Ta(N(R,)(CH₂)_xN(R₂))_y(NR₃R₄)₅._2y

wherein:

x is 1 or 2;

y is 1 or 2;

each of R╬╣-R-₄ is independently selected from the group consisting of H, Ci-

C₄ alkyl, aryl, perfluoroalkyl, and trimethylsilyl;

(iv) tantalum amide compounds of the formula

Ta(NRR')₅

wherein each R and R' is independently selected from the group consisting of

H, C].C₄ alkyl, phenyl, perfluoroalkyl, and trimethylsilyl, subject to the proviso that in each NRR' group, R ΓÇó R';

(v) ╬▓-ketoimines of the formula

Rd R₂

41 wherein each of Rj, R₂, R_a, R_b, R_c and R_d is independently selected from H,

aryl, C╬╣-C₆ alkyl, and C╬╣-C perfluoroalkyl; and

(vi) tantalum cyclopentadienyl compounds of the formula

wherein each R is independently selected from the group consisting of H,

methyl, ethyl, isopropyl, t-butyl, trimethylsilyl.

7. A method according to claim 5, further comprising a solvent for said

precursor.

8. A method according to claim 7, wherein said solvent is selected from

the group consisting of C₆-C╬╣o alkanes, C₆-C╬╣o aromatics, and compatible mixtures

thereof.

9. A method according to claim 7, wherein said solvent is selected from

the group consisting of hexane, heptane, octane, nonane, decane, toluene and xylene.

10. A method according to claim 5, comprising liquid delivery chemical

vapor deposition of said precursor.

42

11. A method according to claim 5, comprising deposition of Ta and/or

Ti on said substrate by a technique selected from the group consisting of chemical

vapor deposition, assisted chemical vapor deposition, ion implantation, molecular

beam epitaxy and rapid thermal processing.

12. A method according to claim 5, wherein the substrate comprises a

microelectronic device structure.

13. A method according to claim 12, wherein TaN or TaSiN is deposited

on said substrate, and the substrate thereafter is metallized with copper or integrated

with a ferroelectric thin film.

14. A method according to claim 12, wherein TaN is deposited on said

substrate, and the substrate thereafter is metallized with copper or integrated with a

ferroelectric thin film.

15. A method according to claim 5, comprising liquid delivery chemical

vapor deposition of said precursor to form TaN on the substrate, and thereafter

metallizing the substrate with copper or integrating the substrate with a ferroelectric

thin film.

43