‘‘L-Cell’L-Cell’

A Novel Device for Plating A Novel Device for Plating Process DiagnosticsProcess Diagnostics

L-Chem, Inc.Shaker Heights, OH 44120

www.L-Chem.com 

Introducing a novel, multi-purpose Introducing a novel, multi-purpose device that provides:device that provides:

• Process parametersProcess parameters

• Process diagnosticsProcess diagnostics

• Fully automatedFully automated

• No expertise required

• Fast (2 min./test)

OUTLINEOUTLINE• Rationalle and needRationalle and need• Current tecnology and its Current tecnology and its defficienciesdefficiencies• The L-Cell - principles and The L-Cell - principles and descriptiondescription• ExamplesExamples• ConclusionsConclusions

Issues in PlatingIssues in Plating

Predictive DesignPredictive Design

Meeting Specs., OptimizationMeeting Specs., Optimization

Process Control and Process Control and MaintenanceMaintenance

Environmental and Health

New Materials

L-L-CellCell

FUTURE:FUTURE:

Available ToolsAvailable Tools Predictive DesignPredictive Design

OptimizationOptimization

Process ControlProcess Control

}} Computer Aided Design Computer Aided Design Software -Software - ‘Cell-Design’‘Cell-Design’

o Hull-CellHull-Cell

o Electroanalytical Electroanalytical Techniques-Techniques-

Polarization studiesPolarization studies

Conductivity Conductivity

Titration (reactant Titration (reactant conc.)conc.)

PAST:PAST:

Limitations of CAD SoftwareLimitations of CAD Software

OUTPUT

INPUT

Numerical‘Solver’

Cell configuration• Cell• Anodes• Racks and Shields

Operating Conditions• current or voltage

(DC or Periodic)• temperature• flow

Process Properties• Electrode polarization• Electrolyte conductivity• Diffusivity

• Current distribution• Deposit thickness distribution• Potential distribution• Overpotential (polarization)• Parasitic reaction rates• Alloy composition• Part’s evolving shape• Deposit texture

Often Often MissingMissing

• Strong dependence on trace additivesStrong dependence on trace additives• Proprietary formulationsProprietary formulations• Lack of fundamental mechanistic understandingLack of fundamental mechanistic understanding• Laboratory experiments often do not duplicate process Laboratory experiments often do not duplicate process conditionsconditions• Flow dependenceFlow dependence• Cost:Cost:

• Potentiostat ~ $ 20,000 - 40,000Potentiostat ~ $ 20,000 - 40,000• Rotating disk electrode ~ $ 10,000Rotating disk electrode ~ $ 10,000• PhD investigator ~ $ 100K/yrPhD investigator ~ $ 100K/yr

Issues with Obtaining Process Data Issues with Obtaining Process Data using Conventional Approachusing Conventional Approach

i

V

Limitations of the Hull-CellLimitations of the Hull-Cell

• Qualitative

• Current distribution is inherently inaccurate – varies with material

• No quantitative data

++-

The L-Cell Provides:The L-Cell Provides: Comprehensive electrochemical process parameters

• Polarization curves

• Kinetics parameters

• Conductivity

Process diagnostics:

• Indication of process variation due to

additives consumption

contamination

Tool for process adjustment using a small (50 ml) volume

Sample plated at a number of different and precisely known current densities for visual and analytical off-line testing

• Composition of alloy – partial currents

• Thickness measurements – current efficiency as f(i)

Fully automated, fast (2 min.) experiment designed for non-experts

Equipment is relatively inexpensive

THE L-Cell – Principle of Operation THE L-Cell – Principle of Operation • Multi-electrode cartridge and a cell that allows a separate current feed to each segment

• Electronics to provide a different and precisely measured current density to each segment

• Automated data acquisition and analysis

Plated cartridge with segmented electrodes Cross-section

The L-Cell: Table-top design The L-Cell: Table-top design

The multi-pin connector The multi-pin connector

The L-Cell: Table-top designThe L-Cell: Table-top design

The L-Cell: Table-top designThe L-Cell: Table-top design

Watts Nickel Testing

Design of the L-CellDesign of the L-Cell ‘Cell-Design’ Modeling

Current distribution – different between segments but uniform on each segment

Potential distribution:

Reference electrode

Top View (cross-section): Anode: oxygen evolution

Segmented cathode (plated cartridge)

THE L-Cell – Analytical Approach THE L-Cell – Analytical Approach Unknowns:

Voltage balancesVoltage balances

Cathodic polarization curve: iK =f (A)

Cathodic overpotentials (i0, C, A)

Conductivity

Measure:Segmental current densities

Voltages (including reference electrodes)

Conductivity

Across the cell Overpotentials

Data analysisData analysisButler-Volmer fit kinetics parameters (i0, C, A)

0

FF CA

a aRT RTKi i e e

DATA ANALYSISDATA ANALYSIS

0

FF CA

ERT RT

B

Ci i e e

C

a C

Butler-Volmer:

(pure kinetics, No transport limitations)

Mass transport included:

Here, i0 is measured at CB and:

CB

CE

= CBCE

DATA ANALYSISDATA ANALYSIS

0

FC

E RT

B

Ci i e

C

1E

B L

C i

C i

Tafel approximation:

Equivalent mass transport boundary layer thickness

BL

C

nFDCi

0 1

FC

RT

L

ii i e

i

DATA ANALYSISDATA ANALYSIS

0

1

FC

RTK

L

ii i e

il

ik = Equivalent pure ‘kinetics‘ current derived from the measured current density, i

0 1

FC

RT

L

ii i e

i

The L-Cell System The L-Cell System

DATA AQUISITION DATA AQUISITION

0.18

1.25 1.0929.018.114.28.35.0

22. 6

3.02

Cu deposition

Copper sulfate

0.5 M

pH=2

Polarization curve

Kinetics Parameters

Cu deposition

Copper sulfate

0.5 M

pH=2

100 ppm PEG

Cu deposition

Copper sulfate

0.5 M

pH=2

Compare with:

100 ppm PEG

Pure Cu

w/PEG

Comparing two tests

w/PEG

Specification of acceptable deviation

0

20

40

60

80

100

-0.21-0.16-0.11-0.06

Overpotential, [V]

Curr

ent de

nsi

ty [m

A/c

m2]

Copper deposition from copper sulfate Copper deposition from copper sulfate No additives; pH=2No additives; pH=2

0.0

0.5

1.0

1.5

2.0

2.5

-0.4-0.3-0.2-0.10

Overpotential, [V]

No PEG

100 ppm PEG

Lo

g i

[m

A/c

m2 ]

Copper deposition from copper sulfate Copper deposition from copper sulfate pH=2pH=2

0

20

40

60

-1-0.9-0.8-0.7-0.6-0.5-0.4

Overpotential, η [V]

C

urr

en

t d

en

sit

y [m

A/c

m2 ]

Nickel Deposition from a standard Nickel Deposition from a standard Nickel Watts ElectrolyteNickel Watts Electrolyte

0

0.4

0.8

1.2

1.6

2

-1-0.9-0.8-0.7-0.6-0.5-0.4

Overpotential, η [V]

L

og

{ i K

[mA

/cm

2] }

Nickel Deposition from a standard Nickel Deposition from a standard Nickel Watts ElectrolyteNickel Watts Electrolyte

Wagner Number Wagner Number

Throwing Power Throwing Power

The L-Cell Provides:The L-Cell Provides:

• Process properties: Polarization, Kinetics, Conductivity– Use ‘regular production’ solution– By-pass specialized testing – no special expertise needed– No need to scan v-i, or apply transients – use steady-state data– Fast (2 min.), completely automated

• Produces deposit samples plated at different current densities

• Process diagnostics tool

Summary -Summary -