1. 11/8/2000 1 Chemical Aspects of CMP SFR Workshop November 8, 2000 Tanuja Gopal and Prof. Jan Talbot UC San Diego La Jolla, CA 2001 GOAL: Build integrated CMP model for basic mechanical and chemical elements. Add CMP bench-scale experiment in Senior Chemical Engineering Lab (CENG 176 A&B) Winter & Spring 2001.

2. 11/8/2000 2 Role of Chemistry Chemical and electrochemical reactions between material (metal, glass) and constituents of the slurry (oxidizers, complexing agents, pH) –Dissolution and passivation Solubility Adsorption of dissolved species on the abrasive particles Colloidal effects Change of mechanical properties by diffusion & reaction of surface

3. 11/8/2000 3 Mass Transfer Processes (a) movement of solvent into the surface layer under load imposed by abrasive particle (b) surface dissolution under load (c) adsorption of dissolution products onto abrasive particle surface (d) re-adsorption of dissolution products (e) surface dissolution without a load Ref. L. M. Cook, J. Non-Crystalline Solids, 120, 152 (1990).

4. 11/8/2000 4 Generic Chemical Reactions Dissolution: M (s) + A  > M (aq) + B M (s) + A  > M n+ + ne - + B Oxidation: M (s) + O  >   M-oxide (s) Oxide dissolution: M-oxide (s) + A  > M (aq) + B M-oxide (s) + A  > M n+ + ne - + B Complexation (to enhance solubility)

5. 11/8/2000 5 Colloidal Effects Surface charge (zeta potential or isoelectric point, IEP, the pH where the surface charge is neutral) of polished surface and abrasive particle is important (Malik et al.)

6. 11/8/2000 6 Colloidal effects Maximum polishing rates for glass observed compound IEP ~ solution pH > surface IEP (Cook, 1990) Polishing rate dependent upon colloidal particle - W in KIO 3 slurries (Stein et al., J. Electrochem. Soc. 1999 )

7. 11/8/2000 7 Experimental Program Electrochemical/chemical experiments with rotating disk electrode with and without abrasion Measurement of zeta potential of abrasives as function of pH (IEP) and solution chemistry The goal is to model: Electrochemical/chemical dissolution and surface passivation Colloidal effects (adsorption of dissolved surface to particles or re- adsorption) Solubility changes / Change of mechanical properties (hardness, stress)

8. 11/8/2000 8 Synergistic Effects Material removal rate, MRR MRR = k chem (RR mech ) o + k mech (RR chem ) o (RR mech ) o = mechanical wear = K e PV (RR chem ) o = chem. dissolution = k r exp(-E/RT)  C i n K e affected by surface chemical modification C i affected by mass transport (i.e., V) Ref.: Y. Gokis & R. Kistler, ECS Meeting Abstract 496, Phoenix, Oct. 2000.

9. 11/8/2000 9 Selective chemical slurries: –control reaction chemistry –control colloidal properties of abrasives and removed material –enhance solubility of removed material Material wear properties (eg, hardness) Chemically active pads Second year Goal: Integrate initial chemical models into basic CMP model. Validate predicted pattern development, by 9/30/2002. Third year Goal: Develop comprehensive chemical and mechanical model. Perform experimental and metrological validation (with Dornfeld and Spanos) by 9/30/2003. Potential Results for Chemical MP Modeling