CMP Modeling Current Status Goal is to develop

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CMP Modeling – Current Status • Goal is to develop a comprehensive CMP model

CMP Modeling – Current Status • Goal is to develop a comprehensive CMP model that complements experimental program • Begin with hydrodynamic slurry flow model and eventually include pad deformation, polishing, etc. • Bramono (MS with L. Racz) - rigid, flat wafer • Scarfo (MS with V. Manno) - curved wafer • Taylor (MS now) – RR or Pad Deformation Tufts University – Dept. of Mechanical Engineering – MS Thesis Defense –Oct 17, 2002 30

Current Hydrodynamic Slurry Flow Model • 2 -D model of gap between pad and

Current Hydrodynamic Slurry Flow Model • 2 -D model of gap between pad and wafer • Slurry film thickness and angle of attack adjust to satisfy hydrodynamic boundary conditions based on lubrication theory • Calculates slurry film pressure on wafer surface • Slurry is modeled as one phase with one set of properties • Assumes both pad and wafer to be rigid and smooth Tufts University – Dept. of Mechanical Engineering – MS Thesis Defense –Oct 17, 2002 31

Model Theory • To calculate correct slurry film thickness, need to satisfy following condition:

Model Theory • To calculate correct slurry film thickness, need to satisfy following condition: –Slurry must support applied down force – Zero moment is required about gimbal point • Full Navier-Stokes and energy equations were solved using FIDAP version 8. 52 Tufts University – Dept. of Mechanical Engineering – MS Thesis Defense –Oct 17, 2002 33

Chemical Mechanical Planarization (CMP) • Model 2 D cross section to reduce computational time

Chemical Mechanical Planarization (CMP) • Model 2 D cross section to reduce computational time • A user-defined subroutine written to specify new wafer surface position • FIDAP calculates solution for velocities and pressure in fluid region Tufts University – Dept. of Mechanical Engineering – MS Thesis Defense –Oct 17, 2002 34

Summary (Modeling) • Hydrodynamic slurry flow model predicts fluid film thickness and pitch angle

Summary (Modeling) • Hydrodynamic slurry flow model predicts fluid film thickness and pitch angle to satisfy a force and moment balance • Addition of wafer bow significantly increases FFT • Degree of wafer curvature affects pitch angle • Viscous heating results in max temperature change of. 25 °C (increases with higher downforce) • Increases in viscosity significantly increase FFT and pitch angle • Results compare well with experimental measurements (on same order) Tufts University – Dept. of Mechanical Engineering – MS Thesis Defense –Oct 17, 2002 43