chemical- mechanical planarization · rotary polishing tool slurry pad diamond conditioner...
TRANSCRIPT
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?
Camera System
• 12-bit high resolution CCD768 x 512 pixel array
• Optically split & filtered
• Spatially aligned (50 mm/pixel resolution) & orthogonal
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
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
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
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)
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