61−技術資料−●A Novel Ruthenium Precursor for MOCVD
without Seed Ruthenium Layer
Tosoh, Tokyo Research CenterTokyo Institute of Technology

Tetsuo Shibutami
Noriaki Oshima
Hiroshi Funakubofor Ru films deposition by MOCVD. In MOCVD

1．Introduction

process, the deposition characteristics and properties ofRuthenium is considered a most promising electrodematerial for high - dielectric capacitors such as
tantalum pentoxide (Ta 2O 5) and barium strontium
titanate [(Ba,Sr)TiO3] in Gbit-scale dynamic random

the Ru films deposited from Ru(DMPD)(EtCp) werecompared with those from conventional Ru(EtCp)2.

2．Experimental

access memories (DRAMs), because it has low

The molecular structure of Ru(DMPD)(EtCp) andresistivity, excellent chemical stability and good dryRu(EtCp)2 are shown in Fig.1(a) and 1(b), respectively.

etching property. Since Grean et al. 1 have reported on

Ru thin films were deposited on oxidized Si substrates

the preparation of Ru and RuO2 films by metalorganic

without seed Ru layer by MOCVD at the deposition

chemicalusing

temperature range from 260℃ to 500℃ using[Ru 3 (CO) 12 ],Ru(DMPD)(EtCp) and Ru(EtCp) 2 individually. Thevapor

triruthenium

deposition(MOCVD)

dodecacarbonylbis(cyclopentadienyl)ruthenium [Ru(Cp) 2Cpvapor of the precursor was generated by bubbling:cyclopentadienyl], and tri(acetylacetonate)ruthenium

method kept at 60℃ where vapor pressure of[Ru(C 5H 7O 2) 3] precursor, there have been several

Ru(DMPD)(EtCp) and Ru(EtCp)2 were the same andattempts to deposit Ru film by MOCVD using

showed approximately 5.3Pa.

precursors such as tri(dipivaloylmethanate)rutheniumtransferred to the cold wall type CVD reactor chamberThis vapor was[Ru(DPM) 3 DPM : dipivaloylmethanate] 2,3 , tri(octanedionate)ruthenium
octanedionate]

4,5[Ru(OD)3 OD :and bis(ethylcyclopentadienyl)

（a）

（b）

ruthenium [Ru(EtCp)2 EtCp : ethylcyclopentadienyl]6,7.
Among those precursors, Ru(EtCp) 2 has attracted
attention because it has high vapor pressure and is in aRu

liquid state with low viscosity (approximately 5cP) atRu

room temperature. However, there are several reports
for the disadvantage of Ru films deposited usingRu(EtCp)2 precursor in that it has long incubation timeat the initial stage of the growth.8,9In order to avoid

Fig.１

Molecular structures of（a）Ru（DMPD）（EtCp）
and（b）Ru（EtCp）2.

the long incubation time, there have been someattempts to deposit MOCVD-Ru film on a seed layer ofTable１ Experimental conditions for Ru film deposition
by MOCVD

sputter-deposited Ru8.
In the present study, the liquid precursor of (2.4dimethylpentadienyl)(ethylcyclopentadienyl)ruthenium[Ru(DMPD)(EtCp) DMPD:2.4-dimethylpentadienyl]with liquid state having low viscosity (approximately6cP) at room temperature, which was a new product welaunched as a novel precursor, was prepared and used
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Precursor
Temperature
Carrier gas flow rate
Pressure
Total flow rate
Dilute gas flow rate
Deposition temperature

Ru（DMPD）（EtCp）, Ru（EtCp）
260℃
100cm3/min
1.33kPa
600cm3/min
500cm3/min
260〜500℃

62TOSOH Research ＆ Technology Review Vol.47（2003）

by nitrogen carrier gas. Si wafer covered with 100nm-in Fig. 3(a) and 3(b) at a deposition temperature ofthick SiO2 was used as a substrate. The deposition

260−500℃ from Ru(DMPD)(EtCp) and Ru(EtCp)2,conditions of Ru thin films are summarized in Table 1.

respectively. In this case, the film was deposited for

The decomposition temperature of precursors were

60min. As shown in Fig. 3(a), the deposition rate of Ru

measured by differential scanning calorimetry (DSC).

films deposited from Ru(DMPD)(EtCp) was constant

The crystal structure was identified by X-ray diffraction

regardless deposition temperature above 325℃. This(XRD). The deposition amount was measured by the X-result indicates that deposition in this temperature

ray fluorescence (XRF). The resistivity of the Ru films

region dominated by mass-transport-limited process.

were measured using standard four-probes method.

On the other hand, the deposition rate was decrease

The concentration of carbon impurity in the Ru films

with deposition temperature decrease below 300℃.

were analyzed by secondary ion massspectroscopy

This phenomenon indicates that the deposition rate is(SIMS). The surface morphology was investigated bycontrolled by a reaction-limited process with activation

scanning electron microscopy (SEM).

energy (Ea) of approximately 1.4eV. As shown in Fig.
3(b), the deposition rate of the film deposited from

3．Results and Discussion

Ru(EtCp) 2 was much more unstable than that ofFig. 2 shows the DSC curves as a function oftemperature. The exothermic peak of Ru(DMPD)

Ru(DMPD)(EtCp). Therefore, Ea for Ru(EtCp)2 could
not be estimated.

(EtCp) was started about 80℃ lower than that fromFig.4 shows cross-sectional and surface SEM imageRu(EtCp)2. This result indicates that the decompositionof the Ru films deposited at 350℃ for 60min. As showntemperature of Ru(DMPD)(EtCp) was lower than thatin Fig. 4(a) and 4(c), the grain size and the columnof Ru(EtCp)2.

width of Ru films deposited from Ru(DMPD)(EtCp)

The Arrhenius plot of the deposition rate are shown

were much smaller than that from Ru(EtCp) 2. The
average grain size of Ru films deposited fromRu(DMPD)(EtCp) and Ru(EtCp)2 were approximately

30DSC［mW］

2550nm and 150 nm, respectively.

Ru（EtCp）
220

Fig. 5(a) and 5(b) show X-ray diffraction (XRD)

15patterns of the same films as shown in Fig. 3 deposited

10Ru（DMPD）（EtCp）

5

at0

deposition

temperaturesfrom

Ru(DMPD)(EtCp) and Ru(EtCp)2, respectively. All−50100

200

300

400

500

Tempereture［℃］

Fig.２

Deposition temperature［℃］
500 400
300
1（a）

0.1
Ea＝1.4eV

0.01
1.20 1.40

1.60 1.80 2.00

1000/T
［K−1］

Fig.３

diffraction peaks could be assigned to be pure Ru phasefor both films deposited from Ru(DMPD)(EtCp) and

The DSC curves of Ru（DMPD）（EtCp）andRu（EtCp）2 under N2 atmosphere at a heating
rate 10℃/min.

Deposition rate［mg/（cm2.h）］

Deposition rate［mg/（cm2.h）］variousRu(EtCp)2 .

Deposition temperature［℃］
500 400
300
1（b）

0.1

0.01
1.20 1.40

1.60 1.80 2.00

1000/T［K−1］

Arrhenius plot of the deposition rate of Ru films
using（a）Ru（DMPD）（EtCp）and（b）Ru（EtCp）2.
Deposition time was 60 min.

Fig.４

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Cross-sectional and surface SEM images of the Ru
films deposited at 350℃ for 60min from（a）（b）
Ru（DMPD）（EtCp）and（c）（d）Ru（EtCp）2.

500℃
400℃

63

deposited from Ru(EtCp)2, while clear deposition wasRu（101）

Ru（002）
SiRu
（100）

（b）
Intensity［a.u.］Si

Intensity［a.u.］（a）Ru（101）

Ru（100）
Ru（002）

東ソー研究・技術報告 第47巻（2003）

observed from Ru(DMPD)(EtCp). This phenomenon
indicates that the deposition process from Ru(EtCp)2
has longer incubation time than that from500℃Ru(DMPD)(EtCp). This is in good agreement with the400℃

previous reports by Matsui et al. 8 and Kadoshima et

300℃

300℃260℃260℃

al . 9 . The grain size of Ru films deposited fromRu(DMPD)(EtCp) were much smaller than that from

2030

4050

2030

2θFig.５

4050

Ru(EtCp) 2 . The small grain size of the Ru film

2θdeposited from Ru(DMPD)(EtCp) is considered to be
due to high nuclear density. This phenomenon

XRD patterns of Ru thin films deposited atvarious temperatures from（a）Ru（DMPD）（EtCp）and（b）Ru（EtCp）2 for 60 min

indicates that the density of the film deposited fromRu(DMPD)(EtCp) is higher than that from Ru(EtCp)2.

Fig. 6 shows the variation of the resistivity of thesame films as shown in Fig. 3. The resistivity of Ru

1.E＋22

films deposited from Ru(DMPD)(EtCp) and Ru(EtCp)2Concentration［atoms/cc］

was high when the deposition temperature was 260℃.
However, it decreased with the increase of deposition
temperature and was under 20μΩcm above 350℃.
The amount of carbon ions in the Ru films wasanalyzed by SIMS. Fig. 7 shows the dependence ofaverage concentration of carbon on deposition

1.E＋21

1.E＋201.E＋19temperature. Carbon concentration decreased asdeposition temperature increased for the films
deposited from both precursors.

1.E＋18The carbon

200

concentration was 3 x 1020 atomic/cc for both films

400600Temperature［℃］

above 400℃.
Fig. 8 shows SEM images of the first stage of theFig.７

Arerage concentration of carbon（determined bySIMS）in Ru films deposited from（●）Ru（DMPD）（EtCp）and（○）Ru（EtCp）2.

Fig.８

SEM images of the surface of Ru films deposited
at 350℃ from（a）（b）Ru（DMPD）（EtCp）and（c）（d）Ru（EtCp）2 for（a）（c）5min,（b）（d）20min.

films deposition at 350℃ from Ru(DMPD)(EtCp) andRu(EtCp)2. As shown in Fig. 8(d), the deposition washardly observed for 5min deposition when the film was

Resistivity［μΩcm］

50403020100250300

350400450500550

Deposition temperature
［℃］

Fig.６

The resistivity of Ru films deposited from（●）Ru（DMPD）（EtCp）and（○）Ru（EtCp）2.

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300

Deposition amount［mg/cm2］

TOSOH Research ＆ Technology Review Vol.47（2003）

Deposition amount［mg/cm2］

64Ru（DMPD）（EtCp）
Ru（EtCp）2200（a）

1000050

100

60

Ru（DMPD）（EtCp）
Ru（EtCp）240（b）

2000

Deposition time
［min］

50100

Deposition time［min］

Fig.10 Deposition time dependency of the deposition
amount of Ru films deposited at（a）350℃ and（b）275℃

Fig.９

SEM images of the surfrace of Ru films deposited
at 275℃ from（a）（b）Ru（DMPD）（EtCp）and（c）（d）
Ru（EtCp）
2 for（a）（c）25min,（b）（d）35min.

deposited from Ru(DMPD)(EtCp) precursor wasdenser than that from Ru(EtCp)2 precursor. Moreover,the deposition process from Ru(DMPD)(EtCp) hadFig. 9 shows SEM images of the first stage of themuch shorter incubation time than that from Ru(EtCp)2

films deposition at 275℃ from Ru(DMPD)(EtCp) andwhen the films were deposited at 275 and 350℃. ThisRu(EtCp)2. As shown in Fig. 8(c) and Fig. 9(c), theshows that Ru(DMPD)(EtCp) is the novel precursor for

incubation time of Ru films deposited at 275℃ fromMOCVD-Ru film that have dense structure and shorterRu(EtCp) 2 was much longer than that deposited atincubation time. The difference of deposition process

350℃. While the clear deposition was observed atfor Ru(DMPD)(EtCp) and Ru(EtCp)2 is considered to275℃ from Ru(DMPD)(EtCp).

be due to difference of decomposition property of thoseFig. 10 shows relationship between the deposition
amount of the films and the deposition time for thefilms deposited at 350℃ and 275℃ .

For bothprecursor.

References

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Schnoes, and D. Brasen, J. Electrochem. Soc., 132,Ru(DMPD)(EtCp). Furthermore, the incubation time2677(1985).

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4．Conclusions

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temperature of 260−500℃ together using conventional

Shimamoto, and S. Kimura, Electrochem. Solid-Ru(EtCp)2. The films consisted of Ru single phase forState Lett., 4,C9(2001).

the entire deposition temperature range regardless of

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