Some advanced technologies require tight specifications around thickness and total thickness variation without compromising other critical tolerances such as surface finish, subsurface damage and contamination


Achieving next generation accuracy and thickness control requirements is extremely difficult using conventional manufacturing processes


Proposed solution

MRF can be used to target a desired thickness and meet tight total thickness variation specifications for: 

  • SOI wafers
  • Coatings
  • MEMS applications




Correct thickness uniformity of top Si layer


SOI (Silicon-on-Insulator) Wafer

  • Size: 200 mm Φ
  • Material: Silicon


The MRF System Configuration

  • Rotational polishing mode
  • 150 mm wheel
  • Large spot to minimize cycle time
  • D20 MRF fluid
  • Low roughness




Measuring Thickness


  • Measure thickness of top Si coating layer
  • Wafer flatness does not have to be perfect
  • Measurement is extremely accurate and repeatablemrfApp4 fig3





Thin film 200mm SOI Wafer

  • PV < 2 nm achieved!
  • Shows MRF capable of polishing to metrology limit


mrfApp4 fig4







  • Total thickness variation of <2nm was achieved
  • MRF routinely polishes glass and crystalline materials to a surface roughness of <5Å RMS
  • MRF uses sheering forces to removal material so no subsurface damage is introduced