3−報文−A Novel Iridium Precursor for MOCVD
Kazuhisa KAWANO
Mayumi TAKAMORI
Ken−ichi TADA
Tetsu YAMAKAWA
Noriaki OHSHIMA
Soichi WATARI
Hironori FUJISAWA
Masaru SHIMIZU

A novel liquid iridium precursor (1,3-cyclohexadiene)(ethylcyclopentadienyl)iridium, Ir(EtCp)(CHD), wassynthesized and its physical properties examined. Ir (EtCp) (CHD) showed physical properties suitable for metalorganic chemical vapor deposition (MOCVD). It exhibited enough vapor pressure (0.1 Torr/75℃), excellent
volatility, and adequate decomposition temperature. The characteristics of Ir films depositedby MOCVD

method using Ir(EtCp)(CHD) and a conventional Ir precursor (1,5-cyclooctadiene) (ethylcyclopentadienyl)
iridium Ir(EtCp)(COD) were compared. The Ir films grown using Ir(EtCp)(CHD) showed shorter incubation
time and higher nucleation density than those from Ir(EtCp)(COD) at initial growth stage of deposition.

tetramethyl-3,5-heptanedionate)iridium(I)1．Introduction

Ir(thd)(COD), [7,8] and Ir(EtCp)(COD) [9]. Among

Iridium (Ir), ruthenium (Ru), platinum (Pt) and their

these, Ir(EtCp)(COD) was intensively investigatedoxides have been investigated as the capacitor

because it is a liquid at room temperature, having

electrodes of next generation memory devices

higher vapor pressure than other solid precursors

including ferroelectric random access memories

described above. Liquid precursors are of great(FeRAMs). Among these noble metals, Ir and IrO2 areadvantage in MOCVD from the viewpoint of material

especially attractive as materials for the FeRAMs

delivery. Ir(EtCp)(COD) has a rigid structure and iselectrodes, because they are excellent barriers tovery stable under MOCVD conditions. When theoxygen diffusion and effective for improvement of thegrowth conditions were optimized, the Ir films of good

fatigue loss of PZT capacitors. For the realization of

step coverage and/or conformality were deposited.

three-demensional memory devices, more attentions beHowever, it was difficult so far to deposit iridium oxidecome to be paid to the MOCVD method.

thin film by MOCVD using Ir(EtCp)(COD) .

There have been several reports on the Ir and IrO2
films by MOCVD using (1,5-cyclooctadiene)

2．Experimental(cyclopentadienyl)iridium(I) Ir(Cp)(COD), [1] (1,5-Molecular structures of Ir(EtCp)(CHD) andcyclooctadiene) (methylcyclopentadienyl)iridium(I)

Ir(EtCp)(COD) are shown in Fig.１ (a) and (b)Ir(MeCp)(COD), [1-3] tris(acetylacetonato)iridium

respectively. Ir(EtCp)(COD) was commercially(III) Ir(acac) 3, [4-7] (1,5-cyclooctadiene)(2,2,6,6-available. A novel iridium precursor, Ir(EtCp)(CHD),

（ 3 ）

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TOSOH Research ＆ Technology Review Vol.48（2004）

iridium(I) Ir(EtCp)(CHD) −n-BuLi solution (1.58 M（a）

73.2 ml, 114 mmol) in n-hexane was added dropwise to（b）
Ir

a freshly prepared ethylcyclopentadiene (EtCpH)

Ir

monomer (13.2 ml, 114 mmol) in tetrahydrofuran(THF, 600 ml) at −78℃ during the course of 45min.
Fig.１

Molecular structures of (a) Ir(EtCp)(CHD)
and (b) Ir(EtCp)(COD).

After the addition was complete, the reaction mixture
was allowed to warm to room temperature (r.t.). Thewas prepared by a similar synthetic route (Fig.２) as

resulting EtCpLi solution in THF was added slowly to a

described in the previous paper [11].

mixture of chlorobis(1,3-cyclohexadiene) iridium (42.3g, 109 mmol) and THF (300 ml) at −78 ℃ during 2 h.

2.1

Preparation

After addition, the solution was allowed to warm to r.t.

Iridium(III) chloride hydrate was purchased fromand stirred for additional 1 h. n-Hexane (1.8 L) was

Furuya metal Co., Ltd. 1,3-Cyclohexadiene andadded to the mixture and precipitated inorganic salt

ethylcyclopentadiene dimer were purchased fromwas filtered off. The filtrate was concentrated in vacuo

Aldrich Chemical Co., Inc. n -BuLi in hexane wasand the residue distilled yield yellow oil (36.9 g, 93％).

bought from Kanto Kagaku. Tetrahydrofuran was1

purified by distillation from sodium / benzophenone

2H, Cp-H＿), 4.97-4.95 (m, 2H, -CH=CH＿-CH＿=CH-), 4.89 (t,under argon. All other solvents were deoxidized by

J=2.0 Hz, 2H, Cp-H＿), 3.54-3.49 (m, 2H, -CH＿=CH-CH=CH＿-),bubbling argon before use. Nuclear magnetic

2.24 (q, J=7.5 Hz, 2H, CH＿2-CH3), 1.74-1.68 (m, 2H, =CH-resonance (NMR) spectra were measured with a Varian

CH＿2-CH＿2-CH-), 1.54-1.48 (m, 2H, =CH-CH＿2-CH＿2-CH=),

VXR-500s spectrometer. Mass spectra were obtained

1.01 (t, J=7.5 Hz, 3H, -CH2-CH＿3). 13C-NMR (C6D6, δfrom gas chromatography/electron impact mass/ppm) : 100.46 (s, -CH2-C＿H3), 75.59 (s, -C＿H2-CH3), 75.08

spectrometry (GC/EI-MS), using a Hewlett Packard(s, =CH-C＿H2-C＿H2-CH=), 65.94 (s, -C＿H=CH-CH=C＿H-),

G1800A GCD System.

44.11 (s, -CH=C＿H-C＿H=CH-), 28.45 (s, Cp＿-H), 21.47 (s,Chlorobis(1,3-cyclopentadiene) iridium(I) IrCl

H-NMR (500 MHz, C6D6, δ/ppm) : 4.97 (t, J=2.0 Hz,Cp＿-H), 15.62 (s, Cp＿-Et). EI/MS (50 eV, 25 ℃) : m/z(CHD)2−A mixture of iridium (III) chloride hydrate(193Ir) 362 M+.

(48 g, 132 mmol), 1,3-cyclohexadiene (100 ml, 1056

2.2

Measurement of physical propertiesmmol), 2-propanol (900 ml) and H 2O (600 ml) was

Viscosity was measured by use of a rotational

heated with stirring at 73℃ (reflux) for 6 h under argon

viscosimeter. Vapor pressure was determined with our(Ar) atmosphere. The mixture was cooled to 0℃ and aoriginal handmade equipment. Volatility of Ir

resulting white precipitate was filtered under Ar,

precursors was estimated by thermal gravimetry

washed with methanol and hexane and dried underanalysis (TG) and decomposition temperature washigh vacuum to yield a white powder (42.5 g, 83％).

measured using a differential scanning calorimeter

1H-NMR (500 MHz, C6D6, δ/ppm) : 4.30-4.15 (m, 2H,(DSC).

-CH=CH＿-CH＿=CH-),3.35-3.20 (m, 2H, -CH＿=CH-CH=CH＿-),

2.3

MOCVD

Ir thin films were deposited on SiO2/Si substrates by

2.60-2.45 (m, 2H, =CH-CH＿2-CH＿2-CH=), 1.70-1.50 (m, 2H,=CH-CH＿2-CH＿2-CH=).

MOCVD at temperatures 250 and 350 ℃ using(1,3-cyclohexadiene)(ethylcyclopentadienyl)

Ir(EtCp)(CHD) and Ir(EtCp)(COD). These precursors−Ir

IrCl3 ・n H2O

i PrOH, H2O

Fig.２ClIr
THF

Sythesis of Ir(EtCp)(CHD).

（ 4 ）

＋Li

東ソー研究・技術報告 第48巻（2004）

5

were supplied by bubbling method using Ar as a carrier

Physical properties of two precursors are summarizedgas. During the deposition, Ir(EtCp)(CHD) andin Table 2.

Ir(EtCp)(COD) were kept at 70 and 100 ℃ ,Ir(EtCp)(CHD) melts at 15℃ and is a pale yellow

respectively, where the vapor pressures of precursors

liquid of low viscosity (ca.35 cP) at room temperature .

were around 0.1 Torr. Oxygen was used as a co-Furthermore, it has higher vapor pressure (0.1 Torr/75

reactant gas. The precursor was transferred to a cold℃) than Ir(EtCp)(COD) (0.1 Torr/105 ℃). From thewall type MOCVD reactor chamber by Ar carrier gas.

view point of precursor delivery liquid phase at room

The deposition conditions of Ir thin films aretemperature provides great advantage as the MOCVD

summarized in Table 1. The nucleation and surface

precursor .

roughness of deposited films were observed by atomic
force microscopy (AFM). Thickness of deposited films
0.0

was measured with a Dektak profilometer.

Experimental conditions for Ir film deposition
by MOCVDTG［％］

Table１Ir(EtCp)(CHD) Ir(EtCp)(COD)

Conditions

250 ℃, 350 ℃
Deposition temperature
4 TorrReactor pressure
Carrier gas flow rate (Ar) 100 cm3/min
Reacting gas flow rate (O2) 25 cm3/min
Purge gas flow rate (Ar) 50 cm3/min
Precursor temperature
70 ℃
Substrate
SiO2/Si(100)Deposition time
5-40 min

250 ℃, 350 ℃
4 Torr200 cm3/min
50 cm3/min
30 cm3/min
100 ℃
SiO2/Si(100)
1-60 mina）−50.0ｂ）

IrIr−100.0
100.0

Fig.３

200.0
300.0
Temp［℃］

400.0

TG curves of a)Ir(EtCp)(CHD) and b) Ir(EtCP)(COD)
under Ar atmosphere (heating rate , 10℃/min).

Fig.3 shows the TG curves as a function of3．Results and Discussion

temperature. Ir(EtCp)(CHD) is more volatile thanA novel iridium precursor, Ir(EtCp)(CHD) wasIr(EtCp)(COD). Molecular weight of Ir(EtCp)(CHD)

synthesized successfully from iridium chloride via(Mw 365.5) is about 28 a.m.u. smaller than that of113C-NMRIr(EtCp)(COD) (Mw 393.5). These precursors have noWithout the ethyl group onpolar group in molecule, which means that the volatility

cyclopentadienyl ligand, the main product from theof these compounds simply depends on their molecularsecond stage was Ir(Cp)(CHD)2 (data not shown). Theweight.

IrCl(CHD)2 and characterized by H-NMR,
and GC/EI-MS.

bulkiness of ethyl group prevented coordinaton by two
CHD ligands. Ir(EtCp)(COD) has a rigid structure andis too stable to deposit Ir films by MOCVD.
Ir(EtCp)(CHD) has some extent of strain in thethe complexes. We expected the descrease ofdecomposition temperatures due to molecular strain.

a)

4.000
DSC［mW］

molecule in agreement with our strategy in designing

3.000b)Table ２

Physical properties of two precursors

Property

Ir(EtCp)(CHD) Ir(EtCp)(COD)

Molecular weight
Melting point (℃)
Viscosity (cP)
Vapor pressure

365.5
15350.1 Torr/75 ℃

2.000
100.0393.5
14200.1 Torr/105 ℃

200.0

300.0

400.0Temp［℃］

Fig.４（ 5 ）DSC curves of a)Ir(EtCp)(CHD) andb)Ir(EtCp)(COD) under N2 atmosphere(heating rate , 10℃/min).

6TOSOH Research ＆ Technology Review Vol.48（2004）

Fig.４ displays the DSC curves as a function ofFig.５ illustrates the nucleation density at initialtemperature. The exothermic peaks indicate thegrowth stage. Using Ir(EtCp)(CHD), there formed

decomposition temperatures of the precursors. The

many nuclei on the substrate even after 5minresult shows that the starting temperature ofdeposition as expected. Using Ir(EtCp)(COD),

decomposition of Ir(EtCp)(CHD) (ca.300 ℃) is 70 ℃

however, there were scarcely observed nuclei

lower than that of Ir(EtCp)(COD) ( ca .370 ℃) asformation even after 20min deposition. Ir films ofexpected. In our previous study [10], a novel Ru

smaller grain and smoother surface were obtained fromprecursor (2,4-dimethylpentadienyl) (ethylcyclo-Ir(EtCp)(CHD) as compared with Ir(EtCp)(COD). Thepentadienyl) ruthenium Ru(DMPD)(EtCp) began tofilm thicknesses for c) and f) in Fig.5 were 32 nm anddecompose at 270 ℃, while the conventional precursor

25 nm, respectively. The RMS values for c) and f) inbis(ethylcyclopentadienyl) ruthenium Ru(EtCp) 2

Fig.5 were estimated 1.2 nm and 6.6 nm, respectively.

started to decompose at 350 ℃. The decomposition

The roughness is better in c) than that in f), though thetemperature of Ru(DMPD)(EtCp) was 70 ℃ lower thanfilm in c) is thicker than in f). Fine morphology could

that of Ru(EtCp) 2 . Because of such difference inbe realized by carefully controlling the decomposition

decomposition temperature, films deposited fromtemperature of precursors.

Ru(DMPD)(EtCp) showed excellent step coverage andhigh nucleation density at initial growth stage ofFig. 6 shows the deposition time dependence of film

deposition. Thus, we expected that Ir(EtCp)(CHD)

thickness. When Ir(EtCp)(CHD) was used as thewould show excellent depositing characteristics similar

precursor, the Ir films showed little incubation timeto the Ru precursor.

even at low temperature (250 ℃) and the film thickness
increased in proportion to the deposition time. Incontrast, with obvious incubation time was observeda)Ir(EtCp)(CHD),5minb)Ir(EtCp)(CHD),10minc)Ir(EtCp)(CHD),20mind)Ir(EtCp)(COD),20mine)Ir(EtCp)(COD),30minf)Ir(EtCp)(COD),35min
500nm

Fig.５

AFM images of the surface of Ir films deposited from Ir(EtCp)(CHD) (a〜c) andIr(EtCp)(COD) (d〜f) at 250℃ within the time indicated.

（ 6 ）東ソー研究・技術報告 第48巻（2004）

250250350℃
250℃

1501000204060

0204060

Deposition time［min］Deposition time［min］(a) Ir(EtCp)(CHD)(b) Ir(EtCp)(COD)

Deposition time dependence of film thickness for (a) Ir(EtCp)(CHD) and (b) Ir(EtCp)(COD).
Films were deposited on SiO2 at 250 ℃(□ and ■) and 350 ℃ (● and ○). Denotations □ / ○and ■ / ● indicate non-continuous films and continuous films, respectively.

Ir(EtCp)(COD) as shown in Fig.5 (b). For both(4) N,V.Gelfond, F.V.Tuzikov, I.K.Igumenov, Thin SolidFilms, 227, 144 (1993).

precursors, no incubarion time was observed at hightemperature (350 ℃), but the films deposited from(5)R.Vergas, T.Goto, W.Zhang, T.Hirai, Appl.Phys.Lett.,
65, 1094 (1994).

Ir(EtCp)(COD) were not continuous.

(6) Y.M.Sun, J.P.Endle, K.Smith, S.Whaley, R.Mahaffy,

4．Conclusion

J.G.Ekerdt, J.M.White, R.L.Hance, Thin Solid Films,
346, 100 (1999).

In this work, we have synthesized a novel Ir
precursor Ir(EtCp)(CHD) for MOCVD and its physical(7) T.Gerfin, W.J.Halg, F.Atamny, K.Dahmen, Thin

Solid Films, 241, 352 (1993).

properties examined. This compound showed excellent
volatility and adequate decomposition temperature. Thefilms

10000thin

1505050Ir

350℃
250℃

200
Thickness［nm］

Thickness［nm］

200

Fig.６7depositedbyMOCVD(8) C. Xu, F.Dimeo Jr., T.H.Baum, M.Russel,

Mat.Res.Soc.Symp. Proc., 541, 129 (1999).

usingIr(EtCp)(CHD) did not show remarkable incubation(9)M.Shimizu,

K.Kita,H.Fujisawa,

H.Niu,

time, while the Ir films from Ir(EtCp)(COD) showed

Mat.Res.Soc.Symp.Proc., 655, CC1.10 (2001).

long incubation time at 250 ℃. At initial growth stage,(10) T.Shibutami, K.Kawano, N.Oshima, S.Yokoyama,

higher nucleation density was observed withH.Funakubo, Mat.Res.Soc.Symp.Proc., 748, U12.7

Ir(EtCp)(CHD) as compared with Ir(EtCp)(COD). Fine

(2003)

morphology of deposited films could be achieved using(11) J.Evans, B.F.G.Johnson, J.Lewis, J.Chem.Soc.,

Ir(EtCp)(CHD). The phenomena observed with the Ir
precursors were the same as those of the Ru precursors
reported before. Thus, we have successfully controlled
the deposition characteristics of Ir films by modifying
the chemical structure of the precursor.

5．References(1) J.B.Hoke, E.W.Stern, H.M.Murry, J.Mater. Chem.,
1, 551 (1991).
(2) S.K.Dey, J.Goswami, C.-G.Wang, P.Majhi,

Jpn.J.Appl.Phys., 38, L1052 (1999).
(3)Y.M.Sun, X.M.Yan, N.Mettlach, J.P.Endle,
P.D.Kirch, J.G.Ekerdt, S.Madhukar, R.L.Hance,
L.M.White, J.Vac.Sci.Technol., A18, 10 (2000).
（ 7 ）Dalton Trans., 2668 (1972).

8TOSOH Research ＆ Technology Review Vol.48（2004）

著者

氏名 河 野 和 久
Kazuhisa KAWANO

著

者

著

氏名 高 森 真由美

氏名 多 田 賢 一
Ken−ichi TADA

Mayumi TAKAMORI入社 平成 7 年 4 月 1 日

入社 平成11年 4 月 1 日

所属 相模中央化学研究所

所属 相模中央化学研究所

機能性材料グループ

機能性材料グループ（兼）
東京研究所副主任研究員

者

所属 相模中央化学研究所

著者

氏名 山 川哲

Tetsu YAMAKAWA
所属 相模中央化学研究所

機能性材料グループ

触媒化学グループ（兼）副主任研究員

機能性材料グループ
主任研究員

副主任研究員著者

氏名 大 島 憲 昭
Noriaki OHSHIMA入社 昭和61年 4 月 1 日
所属 東京研究所
新材料・無機分野

著者

氏名 亘 理 総 一

著

氏名 藤 沢 浩 訓Soichi WATARI所属 姫路工業大学

者

Hironori FUJISAWA
所属 姫路工業大学

著者

氏名 清 水勝

Masaru SHIMIZU
所属 姫路工業大学

工業研究科

工業研究科

工業研究科

電気系工学専攻

電気系工学専攻

電気系工学専攻

助手

助教授（兼）相模中央化学研究所
機能性材料グループ
主席研究員（ 8 ）