1. Role of Glycine in Chemical Mechanical Planarization (CMP) of Copper
SFR Workshop
May 24, 2001
Serdar Aksu, Fiona M. Doyle
Berkeley, CA
2001 GOAL: to delineate specific roles of a range of complexing agents and oxidizers in copper CMP by 12/30/2001.
5/24/2001

2. Objective and Methods
In copper CMP, electrochemical and mechanical mechanisms are not well understood.
Develop a foundation for understanding the behavior of slurries with complexing agents using glycine as a model reagent
Comparison of Cu electrochemical behavior in aqueous solutions with and without glycine in terms of
Potential-pH diagrams
Polarization experiments
Comparison of in-situ Cu electrochemical behavior during polishing by slurries/solutions with or without glycine
In-situ polarization experiments
In-situ monitoring of open circuit potential (EOC)
5/24/2001

3. TYPICAL METAL (Cu, W, Al etc.) CMP SLURRY CHEMICALS
Planarization Mechanism in Metal CMP by Kaufman’s Tungsten CMP Model
1- Removal of Passivating
Film by Mechanical Action
at Protruding Areas
2- Wet Etch of Unprotected
Metal by Chemical Action.
Passivating Film Reforms
3- Planarization by Repetitive
Cycles of (1) and (2)
Metal
Passivating
Film
TYPICAL METAL (Cu, W, Al etc.) CMP SLURRY CHEMICALS
INHIBITORS: Benzotriazole (BTA)
OXIDIZERS: H2O2, KIO3, Fe(NO3)3
COMPLEXING AGENTS: NH3,
EDTA, Glycine, Ethylene Diamine
PASSIVATION
DISSOLUTION
5/24/2001

4. Experimental Techniques
Rotating Disk
Electrode
In-situ Electrochemical
Experiments
Rotator Frame
w=200 rpm
Rotating Cu
Disk electrode
Luggin Probe &
Reference Electrode
Fritted Glass
Gas bubbler
P=27.6 kPa
Magnetic
Stirrer
Pt Counter Electrodes
Copper
Working
Electrode
Solution / Slurry pool
(Chemicals / Alumina abrasive Particles w/ Average Size ~ 120 nm
from EKC Tech.)
Suba 500 Polish Pad (Rodel Corp)
5/24/2001

5. Copper Electrochemical Behavior
No Glycine
CuT=10-5
RDE 200 rpm
pH=4
pH=9
pH=12
CuT=10-5 ; LT=10-2
10-2 M Glycine
5/24/2001

6. Polishing w/ pad and 5 % Al2O3
In-situ Polarization Diagrams
No Glycine
10-2 M Glycine
pH=9
No abrasion
Polishing w/ pad only
Polishing w/ pad and 5 % Al2O3
No Glycine
10-2 M Glycine
pH=12
5/24/2001

7. In-situ Open Circuit Potential Measurements
Without Glycine
With 10-2 M Glycine
5/24/2001

8. Conclusions
Polarization results well correlated with potential-pH diagrams
No significant changes in in-situ polarization for active behavior
Mechanical components significantly affected in-situ polarization
for active-passive behavior
Kaufman’s tungsten CMP model is also valid for Cu CMP
Glycine (complexing agents) may enhance the polishing efficiency
5/24/2001

9. Future Goals
Investigation of Cu electrochemical behavior in ethylenediamine (En) and ethylenediaminetetraacetic acid (EDTA)
Studying Cu polishing behavior in EDTA
Delineating the synergy effect between chemical (electrochemical) and mechanical contributions
Exploration of the role of chemical oxidizers, especially H2O2
5/24/2001