Current%20Model

1
Current Model
Model is 2D. FIDAP equates force and moment on
the wafer surface and rotates the wafer into
equilibrium.
2
Comparison with Experimental Results

• Model predictions compared with fluid film
  thickness and pitch angle results from Lu et al
  (2001)
• Results on same order
• Film thickness differs by constant of about 20 ?m
  - difference due to DELIF technique?
• Angle of attack is on same order as
  experimentally measured value

42
Tufts University Dept. of Mechanical
Engineering MS Thesis Defense Oct 17, 2002
3
Adding Material Removal

• A method to determine removal rate must be
  determined.
• Possible models include
• Modified Prestons law
• Surface stress model
• Abrasive and chemical wear model
• Arbitrary user-defined model

4
RR Models

• A modified Preston model is probably best.
• Should provide flexibility for various problem
  types.
• Easiest way to obtain removal rate on global
  scale.
• Current research on Preston coefficients for CMP
  exists to some degree.
• Options could become limited depending on the
  method used in FIDAP to implement removal rate of
  the wafer.

5
Current Work Computer Set-up

• Current version of FIDAP (8.7) is not compatible
  with the existing models created in the earlier
  version FIDAP (8.52), although it should be.
• Converting model databases and subroutines this
  month.
• Currently trying to working with FIDAP technical
  support to remedy FORTRAN compiler issues on new
  university UNIX server.

6
Project Priorities Material Removal or Pad
Deformation?

• Should we pursue pad deformation modeling in lieu
  of removal rate?
• If pad deformation experimental envelope and
  simulations should be coordinated

7
Initial Strategies for Pad Deformation Model

• Two existing FIDAP approaches
• Model pad as a flexible thin film
  elasticity(vein wall example) boundary
  condition to fluid problem
• Rigid body movement full model of pad
• First approach is more compatible with previous
  modeling efforts
• Currently running simpler test cases with
  standard FIDAP model while compiler problem is
  upgraded