Copper Electrodeposition on DiffusionBarrier Films- A literature review

by

Batric Pesic

209th ECS Meeting-Denver, COMay 07-12, 2006J1-Electrochemical Processing in ULSI and MEMS II Electrodeposition

University of IdahoDepartment of Materials Science and EngineeringMoscow, ID 83844-3024

ACKNOWLEDGMENT

This work was supported by Micron Technology Foundation under grant MF134

INTRODUCTION

Barrier MaterialsPhysical and Chemical Properties

Electrochemical Deposition Methods Electroless

- Soluble reducing agent- Insoluble reducing agent

Electrodeposition- Direct plating on a barrier film- Direct plating on a seed layer

Some chemistry

My research plans- Techniques- Plating systems

J.A. Cunningham, Solid State Technology, June 18, 2003

Copper Diffusion Barrier TypesAccording to: J.A. Cunningham, Solid State Technology June 18, 2003

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IDEAL DIFFUSION BARRIER REQUIREMENTS

1. Electronically conductive

2. Should not react with Cu, Si and dielectric materials

3. Should have an amorphous microstructure

C.E. Ramberg et al., Microelectronics Engineering 50 (2000) 357-368

C.E. Ramberg et al., Microelectronics Engineering 50 (2000) 357-368

C.E. Ramberg et al., Microelectronics Engineering 50 (2000) 357-368

C.E. Ramberg et al., Microelectronics Engineering 50 (2000) 357-368

No Si3N4

No Cu-Ta Stable and unstable Cu-Ti alloys

Si3N4 everywhere

C.E. Ramberg et al., Microelectronics Engineering 50 (2000) 357-368

What is better to use, crystalline or amorphous Ta-N?

The answer: not consistent

1. MATERIALS SELECTION ISSUE

The answer is almost clear: Ta, Ta-N

2. MICROSTRUCTURE ISSUE

Amorphous TaNx film is more appropriate to use thancrystalline TaN according to:C.-C. Chang, J.S. Chen, and W.-S. Hsu, Failure mechanism of amorphousand crystalline Ta-N films in the Cu/Ta-N/Ta/SiO2 structureJ. Electrochemical Society, 151 (11) G746-G750 (2004).

No Cu reaction productsWhen amorphous TaNx film at interlayer

W.-F. Wu, K.-L. Ou, C.-P. Chou, C.-C. WuEffects of nitrogen plasma treatment on TaDiffusion barriers in copper metallization,J. Electrochemical Society, 150 (2) G83-G89,(2003)

Crystalline structure of TaN outperforms amorphous TaN according to:

G.S. Chen and S.C. Huang, Intrinsic properties and barrier behaviors of thinFilms of sputter-deposited single-layered and alternatively layered tantallumNitrides (Ta2N/TaN), J. Electrochem. Soc., 148(8) G424-429 (2001)

Amorphous Ta2N:no Cu at 700 oC

Crystalline TaN:no Cu at 800 oC

Alternate Ta2N/TaN:Cu still present at 800 oC

Reason for amorphous film deterioration: crystallization grain growth of a-Ta2N.

Si Ta2N Cu Si TaN Cu Si Ta2N/TaN/Ta2N/TaN Cu

S. Tsukimoto, M. Moriyama, M. Murakami,Microstructure of amorphous tantalum nitridethin films, Thin Solid Films 460 (2004) 222-226

Amorphous films develop low density columnar boundaries as pathway forCu diffusion Crystalline TaN is more efficient

ELECTROMIGRATION Two interesting points:1. Electromigration and stress migration are caused by impurities (H, F, O) introduced during processing

T.C. Wang, J. Electrochem. Soc. 152(1) G45-G49 (2005)

2. Direction of current flow plays an important roleGan et al. Effect of current direction on the lifetime ofDifferent levels of Cu dual-damascene metallizationAppl. Phys. Letters, 79 (27) (2001) 4592-4594

RESISTIVITY

Resistivity = f(grain size)Grain size = f(stress)

Low stress copper can be deposited only on low stress substrate(seed layer)

TaN

Ta/TaNTaSiN

TaN

TaSiNTa/TaN TaSiN

Ta/TaN

Balakumar et al. Electrochemical and Solid-State Letters 7(4) G68-71 (2004)

T. Hara and K. NamikiElectrochemical and SolidState Letters, 7(5) C57-C60 (2004)

ADHESION

T. Hara and K. Sakata, Electrochemicaland Solid State Letters, 4(10) G77-G79 (2001)

T. Hara et al. Electrochemical and Solid State Letters, 7(2) G28-G30 (2004)

Adhesion = f(stress, orientation)

CHEMISTRY

Direct Electrodeposition Electroless Deposition

1. Main purpose to form a Cu seed layer Fill by electrodeposition

Catalyst required (Pd is the best)

2. Complete fill by electroless

a) by solution reductant b) by contact displacement

• Preferred approach

• Not developed yet

• Main problem: insulating oxide layer

Direct Electrodeposition

Ta

A. Radisic, G. Oskam, P.C. Searson, J. Electrochem Soc 151 (6) C369-C374 ((2004)S.B. Emery, J.L. Hubbley, D. Roy, J. Elecroanal Chem 568 (2004) 121-133

TaN

S. Kim and D.J. Duquette, Electrochem and Solid State Letters 9(2) C38-C40 (2006)Radisic, et al. J. Electrochem Soc 150 (5) C362-367 (2003)

TiNS. Kim and D.J. Duquette, J. Electrochem Soc 153(6) C417-C421 (2006)J.J. Kim, S.-K. Y.S.Kim J. Electrochem Soc (151 (1) C97-C101 (2004) (Pd only; no Cu seed)L. Magagnin et al. Microelectronic Engineering 76(2004) 131-136L. Graham, C. Steinbruchel, D.J. Duquette, J. Electrochem Soc 149 (8) C390-C395 (2002)A. Radisic, et al. J. Electrochem Soc 148 (1) C41-C46 (2001)G. Oskam, P.M. Vereecken, P.C. Searson, J. Electrochem Soc 146(4) 1436-1441 (1999)

WC. Wang et al. Thin Solid Films 445 72-79 (2003)C. Wang et al. Electrochem and Solid-State Lett 5(9) C82-C84 (2002

CuSO4

HBF4

Citrate

EDTA

TaN Pt

Ta

Radisic, et al. J. Electrochem Soc 150 (5) C362-367 (2003)

A. Radisic, G. Oskam, P.C. SearsonJ. Electrochem Soc 151 (6) C369-C374 ((2004)

ROLE of OXIDE LAYER

CV of Cu2+ on Ta in 0.1M NaNO3+0.6mM Cu(NO3)2

S.B. Emery et al. J. Electroanalytical Chemistry 568 (2004) 121-133

• Two cross-over potentials• Cross-over potential function of vertex potential• No anodic current

Explanation for no anodic current:“…oxide species of Ta act to induce irreversiblelattice incorporation or alloying of the depositedCu…”

H.K. Chang et al. Influence of Ti oxide films on Cu nucleation during electrodepositionMaterials Science and Engineering A 409 (2005) 317-328

H.K. Chang et al. Influence of Ti oxide films on Cu nucleation during electrodepositionMaterials Science and Engineering A 409 (2005) 317-328

“Pipe tunneling” along a dislocation core mechanism for copper nucleation

IBM Research

1997 First working microprocessor using copper electroplating is fabricated

1998 P.C. Andricacos, C. Uzoh, J.O. Dukovic, J. Horkans, H. Deligianni Damascene copper electroplating for chip inteconnections

IBM Research, Vol 42 No 5 (1998) p. 567

- Introduced shape-induced concentration-field effects concept to describe additive distribution within micron size voids during electrodeposition

- New terminology: subconformal, conformal and superconformal (superfilling) modes of electrodeposition

2005 P.M. Vereecken, R.A. Binstead, H. Deligianni, P.C. Andriacacos The chemistry of additives in damascene plating, IBM J. Res.&Dev.

Vol. 49. No. 1 January 2005 2005 T.P. Moffat, D. Wheeler, M.D. Edelstein, D. Josell, Superconformal film growth: Mechanism and quantification, IBM J. Res.&Dev.

Vol. 49. No. 1 January 2005

SUPERCONFORMAL FILM GROWTH: Mechanism and quantificationT.P. Moffat, W. Wheeler, M.D. Edelstein, D. Josell, IBM J. Res. &Dev. Vol. 49 No. 1 (2005)

P.M. Vereecken, R.A. Binstead, H. Deligianni, P.C. Andriacacos, The chemistry of additives in damascene plating, IBM J. Res.&Dev. Vol. 49. No. 1 January 2005

Ic: Cu(H2O)62++ e = Cu(H2O)4

+

IIc: Cu(H2O)62+ + 2e = Cu0 + 6H2O

IIa: Cu0 + 6H2O = Cu(H2O)62+ + 2e

Ia: Cu(H2O)4+ + 2 H2O = Cu(H2O)6

2+ + e

Cu0 + Cu(H2O)62+ = 2Cu(H2O)4

+ + 2H2O

OTHER APPROACHES

Electrodeposition must be in kinetic control regime in order to ensure good quality copper. In order to increase the convection, i.e. to avoid diffusioncontrol, various new interesting studies are appearing:

• Effect of gravitational strength: M. Morisue et al. J. Electronal Chem 559 (2003) 155-163

• Centrifugal fields: A. Eftekhari, Microelectronic Engineering 69 (2003) 17-25

• Magnetic fields: M. Uhlemann et al. J Electrochem Soc 151 (9) C598-C603 (2004) M. Uhlemann et al. J Electrochem Soc 152 (12) C817-C826 (2005)

• Microwave effects: U.K. Sur et al. New J. Chem., 28, 1544-1549 (2004)

For fundamental studies, addition of scanning electrochemical microscopycan prove to become an invaluable mechanistic tool.

CONCLUSIONS

• Damascene copper plating is becoming a mature technology.

• Both, the technology development and the explanation of reaction mechanisms have already been provided by the IBM researchers.

Additional research only confirms what has already been postulated, i.e. at most adds some marginal knowledge.

• More research (chemistry) is needed in the area of direct copper plating on diffusion barriers to avoid a processing step for formation of a seed layer.

• More research is needed toward development of more efficient barriers.

• Among the experimental techniques SECM can contribute substantially to understand the phenomena within vias and trenches.

• By comparing the published literature with the technology status of chip manufacturers there is a feeling that the industry is “ahead of the curve” and that the published research only confirms what the industry already knows.