Caprice Gray MRS Spring Meeting San Francisco, CA March 30, 2005 Quantitative In-Situ Measurement of Asperity Compression Under the Wafer During Polishing Caprice Gray MRS Spring Meeting San Francisco, CA March 30, 2005

Overview Introduction Experimental Setup Polisher Dual Emission Laser Induced Fluorescence Pad Compression Experiments and Results Static Compression Dynamic Compression Conclusion

Introduction DELIF is used to collect grayscale images that represent properties under the wafer during polishing pH, temperature, fluid layer thickness Previous thickness measurement time averaged low spatial resolution New DELIF Setup Laser enables instantaneous imaging Larger distance between lens and CCD – 4 mm/pixel In these experiments we use fluid thickness measurements to infer what is happening to pad asperities during polishing

Polishing Setup Motor Platen RotoPol-31 Wafer Force Table Steel Table

DELIF

= Why Examine 2 Emissions? Slurry Ratio Pad Division of 2 images cancels variations in image source intensity

Experiments Pads: flat Fruedenberg FX9 Static: flat glass wafer Global vs. Local topography Static: flat glass wafer Dynamic: etched glass wafer

Static Pad Compression 2 Images were taken in a single section of the pad. 0 kPa 70 kPa 17 total sections were imaged and analyzed.

Histogram Analysis The asperity size distribution is the same shape as the fluid layer thickness distribution. When force is applied to the wafer, the distribution changes both shape and location. Standard deviation comparison → pad compression Peak location → fluid layer thickness. Compression factor: e

Static Compression Results

Dynamic Pad Compression Two wafers were etched and contain square wells 14.5 mm deep 27 mm deep Asperities can expand under these wells. Histograms from regions 1 and 2 are compared Run Conditions: Pad/wafer rotation: 30 RPM Continuous conditioning Slurry flow: 50 cc/min Force applied to wafer: 10 kPa

Dynamic Results (7mm)

Conclusions DELIF can be used to measure slurry film thickness with asperity scale resolution. Over the 6 mm2 regions imaged, Different amounts of fluid can be displaced due to the same applied global forces. Pad topography deformation can be inferred from fluid layer thickness measurements. During a static application of force, local pad compression is roughly linearly related to the amount of fluid displaced by the compression In the dynamic case, asperity expansion into 27 mm deep wells was greater than expansion into 14.5 mm deep wells.

Acknowledgements Tufts Intel Corporation Cabot Microelectronics Professor Chris Rogers Professor Vincent P. Manno Dan Apone TUFTL Intel Corporation Chris Barns Mansour Moinpour Cabot Microelectronics Sriram Anjur University of Arizona Ara Philipossian