Journal of Applied Electrochemistry

, Volume 44, Issue 8, pp 945–952 | Cite as

A shielded rotating disk setup with improved current distribution

Research Article
Part of the following topical collections:
  1. Electrodeposition

Abstract

In contrast to wafer-scale experiments that can employ a sophisticated and well-optimized plating tool, coupon-scale studies of electrodeposition can be hindered by poor current distribution. The impact on primary current distribution and mass transfer of an insulating shield that can readily be used in a rotating disk setup is presented. Numerical simulations were employed to design an insulating shield assuming mass-transfer resistances were negligible. Several designs were fabricated and characterized using copper electrodeposition as the electrochemical reaction. Numerical and experimental results are consistent, and the shield is a convenient and effective way to achieve more uniform current distribution. However, the shield disturbs the uniform mass-transfer rates to the substrate surface that are achieved with a rotating disk. Rates are characterized experimentally, and design tradeoffs are discussed.

Keywords

Electrodeposition Current distribution Uniformity Shield Electroplating 

List of symbols

rs

Outer radius of the shield in unit mm

rho

Inner radius of the shield in unit mm

ro

Radius of the working electrode in unit mm

i

Local current density in unit mA/cm2

κ

Electrolyte conductivity in unit S/m

\( \phi \)

Electrical field in the electrolyte

N

Normal unit vector

ic

Applied current density in unit mA/cm2

Ac

Surface area of the working electrode in unit cm2

Aa

Surface area of the counter electrode in unit cm2

Z

Axial coordinate

io

Exchange current density in unit mA/cm2

αc

Cathodic charge transfer coefficient

F

Faraday constant, 96,485 C/mol

V

Potential on the working electrode in unit V

T

Temperature in unit K

R

Gas constant, 8.314 J/(K mol)

Wa

Wagner number

H

Distance between the anode and the cathode in unit mm

λavg

Linear average of thickness profile of copper deposit in unit nm

N

Number of data points of each thickness profile

λi

Thickness of the copper deposit at ith data point in unit nm

S

Standard deviation of normalized thickness

iavg

Linear average of current–density profile

R

Radial position away from the center in unit mm

K

Slope of Levich plot

N

Number of electrons exchanged in reduction reaction in measuring Levich plots

D

Diffusion coefficient in unit cm2/s

ω

Rotation speed of RDE in unit rpm

ν

Kinematic viscosity in unit cm2/s

c

Bulk concentration of the Fe(III) complex, 1 mM

iL

Limiting current density in unit mA/cm2

t

Thickness of the shield in unit mm

Notes

Acknowledgments

The authors are very grateful to Atotech Inc. for their financial support. We also thank Qian Zhang for her experimental contributions to this study.

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Copyright information

© Springer Science+Business Media Dordrecht 2014

Authors and Affiliations

  1. 1.Department of Chemical EngineeringColumbia UniversityNew YorkUSA

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