Chris RogersVincent Manno

Chemical-Mechanical

Planarization

Chemical-Mechanical Planarization

Surface Planarity

Metal Lines

Oxide/ILD Oxide/ILD

Metal Lines

Oxide/ILD

Metal Lines

Oxide/ILD

Metal Lines

-Non planarized surface -Smoothed surface

-Local Planarity -Global Planarity

Wafer Scale

IC Die

Silicon Wafer

• Dies per wafer is increasing• Wafer non-uniformity leads to losses

Rotary Polishing Tool

Slurry

Pad

Diamond conditioner

Polishing platen

Wafer

Wafer carrier

• Abrasive Slurry• Polymeric Pad• Constant Linear

Velocity

Lubrication Regimes

Lower Surface

Hydrodynamic Lubrication

Partial Lubrication

Upper Surface

Boundary Lubrication

Goal

• Measure between pad and wafer during polish

• Look at

• Mean Residence Time

• Gap thickness

• Temperature

Dual Emission Laser Induced Fluorescence-DELIF

Rat

io

Passive Scalar

I1f

I2f

Excitation Color Separation Image Ratio Scalar

Issues

• Systematic Errors

• I. Dyes have similar emission spectrum

• II. Dye 1 absorbs emission from Dye 2

• III. Emission is a function of the scalar

• Photo-bleaching

• Photo-degradation on the pads

• Mean Residence Time (pH)

• Dual Emitters (Coumarin and DHPN)

• Gap Thickness

• One Emitter, one Absorber (Coumarin+Calcien)

• Temperature

• Dual Emitters (Brilliant Sulfaflavin and DHPN)

What have we measured?

1:2 Polishing Platform

Camera System

• 12-bit high resolution CCD768 x 512 pixel array

• Optically split & filtered

• Spatially aligned (50 mm/pixel resolution) & orthogonal

• Load Cell

• Single component

Friction System

DELIF Example

Measurement Location

• Measure• MRT• Temperature• Thickness• Friction

Measuring MRT

MRT Measurements

Vol

umet

ric

% N

ew S

lurr

y

100

0

100

0

Vol

umet

ric

% N

ew S

lurr

y

Text

Short Pulse

Long Pulse

Measuring Gap Thickness

Slurry

Pad

Diamond conditioner

Polishing platen

Wafer

Wafer carrier

Thickness Calibration

Microscope Slides

Top View Side View

Steel Shim Stock

Region ofInterest

• Absolute vs relative calibration

• Asperities in pad• wet vs dry calibration

slides

Thickness data

Friction data

Convex Wafer (3:2 slurry)Polishing Pad

Polishing PadConcave Wafer (3:2 slurry)

Wafer Stick-Slip

• Intense fluctuations in friction force

• Predominantly present with concave wafers

• Higher frequencies do not shift with pad speed ~> 10 Hz

• Power of higher frequencies reflect intense fluctuations

Change in Stick-Slip with rpm

120 rpm

40 rpm

Effect of Pad Topography

Flat

Grooved

Temperature Measurement

Temperature: Wafer PressureTe

mpe

ratu

re (°

C)

Applied Wafer Pressure (kPa)

40

20

30

10 4530

Concave Bow

Convex Wafer

Convex Bow

Concave Wafer

Tem

pera

ture

(°C

)

Relative Linear Velocity (m/s)

40

20

30

0.1 1.00.5

Concave BowConvex Wafer

Convex Bow

Concave Wafer

Temperature: Rotation Rate

Temperature / FrictionFr

ictio

n Fo

rce

per

Uni

t Are

a (k

Pa)

45

0

30

10 40Applied Wafer Pressure (kPa)

Convex

Concave

0 1Relative Linear Velocity (m/s)

All Together

Slurry Concentration

In an instant

Grooves and Steps

Instantaneous Thickness

“Super Slow” Rotation

Wafer Rotation

Platen Rotation(µm

)

(sec)

Conclusions

• Able to see between pad and wafer during polish

• Measure• MRT• Gap thickness• Friction• Temperature

• Wafer convexity important• Pad and slurry concentrations important• Conditioner important

• Correlate friction with phenomena (end point detection for manufacturing floor)

• Measure pad deformation

• Hand-held DELIF “nose”

• Copper polish

Future