Examination of some key CMP input parameters on slurry fluid mechanics

PI: Chris Rogers

Researchers: Jonathan CoppetaChris Duska

Jeremy Javidi Samuel Brodsky

Corporate Sponsors: Cabot Corporation (Frank Kaufman)Intel Corporation (Ara Philipossian)VEECO Corporation

Numerical Simulations

Fluid Thickness

Thermal Gradients

Mixing Measurements

Polishing Data

ResultsYear 3Integration

Research Strategy

Friction Data Fd

Polishing Platform

100 RPMStruers RotoPol-31

Drill Press

Weighted Traverse

Two Aligned 12 BitCamera

Three Way Solenoid Valve

Tagged Slurry

Slurry

Conditioning System

Design of Experiment

43 RunsVariables

-Pad Manufacturer (Cabot, Rodel, Freudenberg)-Pad Groove Depth (0-40 mils)-Wafer Down Force (2-6 psi)-Platen Speed (30-90 rpm)-Slurry Flow Rate (20-50 ml/min)

Constants-Groove Style (X-Y Grooving, 0.025” width)-Head Speed (60 rpm)-Head Position (3/4” wafer to platen edge)-Injection Location (pad center)-Conditioning (163 Micron diamond grit)

Design of Experiment

Slurry Transport

Interrogation Region

Wafer

Post

Examining;-Mean slurry age-Residence time-Slurry Gradients

(flat pads)-Drag on wafer-fluid thickness measurements

Pad

Repeatability

Flat Pad

Grooved PadManufacturer: CabotSlurry Flow Rate: 35 cc/minWafer Down Force: 4 psiPlaten Speed: 60 rpmX-Y Groove Depth: 20 mils

Time (sec)

Per

cen

t N

ew S

lurr

y

Repeatability

Flat Pad

Grooved Pad Manufacturer: RodelSlurry Flow Rate: 35 cc/minWafer Down Force: 4 psiPlaten Speed: 60 rpmX-Y Groove Depth: 20 mils

Time (sec)

Per

cen

t N

ew S

lurr

y

Slurry Flow Rate

Flat Pad

Grooved PadManufacturer: RodelSlurry Flow Rate: x cc/minWafer Down Force: 4 psiPlaten Speed: 60 rpmX-Y Groove Depth: 20 mils

Time (sec)

Per

cen

t N

ew S

lurr

y

In Situ Conditioning

Time (sec)

Per

cen

t N

ew S

lurr

yOscillation Period

Platen Speed

Manufacturer: FreudenbergSlurry Flow Rate: 35 cc/minWafer Down Force: 4 psiPlaten Speed: x rpmX-Y Groove Depth: 20 mils

Flat Pad

Grooved Pad

Time (sec)

Per

cen

t N

ew S

lurr

y

Static Case

Pad deformation: (4 psi, 0 rpm)

Image of a single pad Thickness profile as determined by ratiometric technique

Pad Profile

Rodel Pad

-80

-70

-60

-50

-40

-30

-20

-10

0r/3

< edge center >

Prof

ile (m

icro

ns) 2 psi

4 psi

6 psi

wafer profile

Radial Profile (static cases)

Static Fluid Thickness Measurements

wafer

PAD

Trapped slurryTrapped slurry

Asperity?Asperity?Surface tension?Surface tension?

Static Fluid Thickness Measurements

Friction Measurements

Friction Measurements

Cabot Pad6 psi down force35 cc/min30 rpm platen speed20 mils x-y groove depth

Friction Data~0.5 Hz Sine Wave

Time (sec)

Coe

ffic

ien

t of

Fri

ctio

n

Friction Measurements

Down Force (psi)

Fri

ctio

n F

orce

(lb

s)

Stribeck CurveC

oeff

icie

nt

of F

rict

i on

Sommerfield Number: (Viscosity*Linear Speed)/Pressure

Flow Regime

Stribeck Curve

Polishing Rates for Crown Glass

Polishing of Crown Glass

0

1000

2000

3000

4000

5000

0 0.2 0.4 0.6 0.8 1

% of Radius

Po

lish

ing

Ra

te

(A/m

in)

3.0” Diameter wafer

Polishing Rate vs Radius

0200400600800

100012001400

0 0.2 0.4 0.6 0.8 1

% of radius

Po

lish

ing

Ra

te (

A/m

in)

Polishing Rates for BK7

3.5” Diameter wafer

Conclusion

-Functional scaled down polishing platform•Polishing data•Slurry mixing measurements•Slurry film thickness measurements•Friction measurements

-Beginning of DOE analysis•Slurry mixing rates depend on:

Platen speedFlow rateIn situ conditioning

Future Directions

-Optimize Struers Polishing performance

-New DOE study on pad material properties

-Scale results to an industrial polisher

-Verify data on an IPEC 372 polisher

-Correlate fluid mechanics to polishing performance

http:\\www.tuftl.tufts.edu

Visit our web site at