41−技術資料−●Development of a Novel Bismuth Precursor for
MOCVDTokyo research center, TOSOH Corporation

Taishi Furukawa
Noriaki Oshima
Department of Innovative and Engineered Materials, Tokyo Institute of Technology
Hiroshi Funakubo

１．Introduction

２．Experiment

Bismuth layer−structured ferroelectrics (BLSF) have

The molecular structure of BiMe2(Me2NCH2Ph) is

been investigated as the capacitor materials of next

shown in Fig.1 and is synthesized from bismuth

generation memory devices including ferroelectric

halides, methylating agents and arylating agents.

random access memories (FeRAMs) 1)−3). BLSF are
attractive materials for FeRAMs because they show

2.1

excellent fatigue endurance.

Preparation

Diethylether was purified by distillation from sodium

For the realization of highly integrated devices, more

/ benzophenone under argon. All other solvents wereattentions come to be paid to metalorganic chemical

deoxidized by bubbling argon before use. Nuclear

vapor deposition (MOCVD). MOCVD is indispensable

magnetic resonance (NMR) spectra were measured

technique for three−dimensional structure memory

with a Varian VXR−500s spectrometer. Mass spectra

devices because of its good step coverage and highwere determined on mass spectrometry (MS) using angrowth rate.

Applied Biosystems QTRAP at TOSOH Analysis andThere have been several reports on BLSF films

Research Center.

preparation by MOCVD using several bismuth

Dimethyl(2 −(N,N −dimethylaminomethylphenyl)

precursors, for example BiMe3, triarylbismuth [BiPh3bismuth − Methylmagnesiumbromide solution (0.6M

tand Bi(o−Tol)3] and trialkoxidebismuth [Bi(O Bu)3 and25ml, 15.0mmol) in diethylether was added dropwise toBi(mmp) 3]. Among these bismuth precursors, onlya suspension of dicholo(2−(N,N−dimethylaminomethylBiMe 3 is a liquid at room temperature. Liquid−phenyl)bismuth (3.30g, 8.0mmol), prepared fromprecursors are of great advantage for MOCVD process

bismuth chloride and 2−(N,N−dimethylaminomethyl−from the viewpoint of the material delivery system.

phenyl)lithium, and diethylether at −78℃ under argon.

However, BiMe3 is explosive. It is not safe to handle

After the addition was complete, the reaction mixture

BiMe3, especially under mass production process at thewas allowed to warm to room temperature (R.T.) andfactories.

stirred for 20h. After the reaction, the reaction mixture

On the other hand triarylbismuth and trialkoxidebi−

was quenched with aqueous NH4Cl, and extracted withsmuth are under great disadvantage to MOCVD fromdiethylether. The extract was concentrated in vacuo

the viewpoint of the source delivery system because

and distillation of the residue gave light yellow oil

they are solid and don t have high vapor pressure.

(1.42g, 48％).
1In this work, a development of a novel liquid bismuth

H−NMR (500 MHz, CDCl3, δ/ppm): 7.95 (d, J=7.0

precursor for MOCVD is developed that can be use

Hz, 1H, ArH), 7.22 (m, 2H, ArH), 7.15 (d,J=7.0 Hz, 1H,safety and has high vapor pressure.

ArH), 3.45 (s, 2H, CH2),2.17 (s, 6H, NMe), 1.06 (s, 6H,Me). 13C−NMR (CDCl3, δ/ppm): 177.53 (s, C), 144.53(s, C), 137.07 (s, CH), 128.60 (s, CH), 128.57 (s, CH),
126.90 (s, CH), 67.66 (s, CH2), 44.80 (s, CH3), 3.08 (s,（ 41 ）

42TOSOH Research ＆ Technology Review Vol.50（2006）

CH3). MS: m/z = 374 (M++H). Elemental analysis: Ctemperature provides great advantage as MOCVD(35.6％), H (5.0％), N (3.7％), Bi (53.5％). C11H18BiNprecursor.
The flash point of BiMe2(Me2NCH2Ph) is 148℃ andrequires C (35.4％), H (4.9％), N (3.8％), Bi (56.0％).

it is a nonexplosive compound. The gradually oxidative
2.2

Measurement of physical properties

decomposition of BiMe 2 (Me 2 NCH 2 Ph) occurs in

Viscosity was measured by use of a rotational

contact with O 2 gas, while the reactivity ofviscometer. Vapor pressure was measured directly

BiMe2(Me2NCH2Ph) with H2O is hardly observed. In

under high reduced pressure in a closed system usingcase of mixing BiMe2(Me2NCH2Ph) and popular otheran absolute capacitance manometer. Volatility of Bi

metal precursor, that is Sr(C11H19O2)3, La(C11H19O2)3,precursors was estimated by thermo−gravimetry

Sr[Ta(OC 2 H 5 ) 2 (OC 2 H 4 OCH 3 )] 2 ,iTa(OC 2 H 5 ) 5 ,ianalysis (TG) and decomposition temperature wasTi(O C 3 H 7 ) 4 or Ti(O C 3 H 7 ) 2 (C 11 H 19 O 2 ) 2 directly ormeasured using a differential scanning calorimeter

dissolved in benzene at R.T., no chemical change in the(DSC).

mixture was observed. As films preparation by
MOCVD, BiMe2(Me2NCH2Ph) can be use safety and2.3

Films preparation by MOCVD

without its decomposition by such as popular precursor

Bi 4 Ti 3 O 12 were prepared by MOCVD using

listed above.

BiMe 2(Me 2NCH 2Ph), Ti(O iC 3H 7) 4 and O 2 gas. Filmcomposition was calculated and decided by X−rayTable１Physical properties of BiMe2(Me2NCH2Ph)

fluorescence spectroscopy (XRF), which was calibrated
with standard film samples. Constituent phases andvapor pressureorientation of the films were characterized by X−ray

decomposition temprature

230℃

diffraction (XRD) using CuKα radiation. Filmmelting point−49℃

flash point

148℃

thickness was measured by field−emission scanningelectron microscopy (FE−SEM).

0.1 Torr/55℃

viscosity

7cP

reactivity with H2Oless reactive

reactivity with O2

gradually reactive

Fig.2 shows the TG curves as a function ofMeBitemperature. BiMe2(Me2NCH2Ph) is more volatile thanNBiPh 3

Mebecause

molecularweightofBiMe2(Me2NCH2Ph)(Mw373.3) is smaller than that ofFig.１

Molecular structure of BiMe2(Me2NCH2Ph)

BiPh3(Mw440.3).

0３．Results and Discussion

synthesized successfully from bismuth chloride as
starting compound and characterized by 1H−NMR and(b)TG［℃］

A novel bismuth precursor, BiMe2(Me2NCH2Ph) was−50(a)13C−NMR.
Physical properties of BiMe2(Me2NCH2Ph) is shownin Table 1. BiMe2(Me2NCH2Ph) melts at −49℃ and is a−10050

light yellow liquid of low viscosity (ca.7 cP) at ambient

point of precursor delivery, liquid phase at room（ 42 ）

150

200

250300350

400

Temperature［℃］

temperature .Furthermore, it has high vapor pressure(0.1Torr/55℃) as MOCVD precursor. From the view

100Fig.２

TG curves of (a) BiMe2(Me2NCH2Ph) and (b)BiPh3 under Ar atmosphere (heating rate 10℃/min)東ソー研究・技術報告 第50巻（2006）

43Fig.3 shows the TG curves and the DSC curves as aH24

H26

function of temperature. The exothermic peaks indicateH25the decomposition temperatures of the precursors. TheH21C19

result shows that the starting temperature ofC20
H20decomposition of BiMe2(Me 2NCH 2Ph) is 230℃ andIn

otherwords,

H22C17vaporized

C5without thermal decomposition.

H110.0Bil

C6−40

6.0

−60

4.0

−80

2.0

−100
50

100

150

200

250

300

350

H6C10C14Fig.４

H13C11C12H18C16H19C8 H8 H15 C13H5H14H9DSC［mW］

TG［℃］

8.0

H16
N1 C15H7H12C7−20H23C1H10C4C9 H11C2C3H2C22H4H3BiMe 2 (Me 2 NCH 2 Ph) can be supplied by MOCVD

0C21

C18

BiMe2(Me2NCH2Ph) can be vaporized before thermal
decomposition.

C23

H17

A drawing of X-ray structure of single crystal ofBi(m-Tol)2(Me2NCH2Ph)

0.0
400

assumedthatBIT(0016)

BIT(0014)
BIT(117)

BIT(0018)

isBIT(0012)it

BIT(0010)

BIT(004)

In respect with molecular structure ofBiMe 2 (Me 2 NCH 2 Ph),

BIT(008)

TG curve and DSC curve of BiMe2(Me2NCH2Ph)
under inert gas atmosphere (heating rate 10℃/min)

Intensity

Fig.３

BIT(006)

Temperature［℃］

BiMe 2 (Me 2 NCH 2 Ph) has the intramolecular Bi−Ncoodinate bond by the results of X−ray structure
analysisofsimilarstructures,

102030Bi(m−40502θTol) 2 (Me 2 NCH 2 Ph), to BiMe 2 (Me 2 NCH 2 Ph). Fig.4

Fig.５

shows the result of X−ray structure analysis of Bi(m−Tol)2(Me2NCH2Ph) and the Bi−N length of it is 2.94Å.

XRD θ- 2θ scans of the BIT films prpared byi
MOCVD from BiMe2(Me2NCH2Ph)-Ti(O C3H7)4-O2systems

The intramolecular Bi− N coodinate bond ofBiMe2(Me2NCH2Ph) prevent BiMe2(Me2NCH2Ph) fromdecomposition.
Other bismuth−contained oxide films, for example

disproportionation of ligands and explosive

SrBi2Ta2O94), Bi2ZnXNb1−XO75) and BiFeO36), can be also

decomposition.
Fig.5 shows the XRD θ−2 θ scans of the as−deposited BIT(Bi4Ti3O12) film with 150nm in thickness

prepared by MOCVD using BiMe2(Me2NCH2Ph) as astarting bismuth precursor.

prepared on (111)Pt/Si substrate at 500℃ by MOCVD
using BiMe2(Me2NCH2Ph), Ti(OiC3H7)4 and O2 gas asstarting materials. (00l) and (117) diffraction peaks of４．Conclusion

BIT phase were detected together with that of Pt phase.

In this work, we have synthesized a novel Bi

N atom did not be found from the BIT film by XPS

precursor BiMe2(Me 2NCH 2Ph) for MOCVD and its

analysis. In other words, the N atoms that are thephysical properties were examined. This compound isincluded element in BiMe 2 (Me 2 NCH 2 Ph) did notnonexplosive, liquid at ambient temperature andlargely incorporated into the films during its

showed excellent volatility and adequate decomposition（ 43 ）44

TOSOH Research ＆ Technology Review Vol.50（2006）

temperature. As the MOCVD source for films

３）T. Takenaka and K. Sakata, J. Appl. Phys., 19, 31

preparation, BLSF and other bismuth−contained oxide
films

canbe

prepared

by

MOCVD

using（1980）.
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Funakubo, Jpn. J. Appl. Phys., 45, L138（2006）.

BiMe2(Me2NCH2Ph).

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１）C. A. Araujo, J. D. Cuchiaro, L. D. McMillan, M. C.

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