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Surface Treatment Solutions for Low-k Dielectrics

Surface Treatment Solutions for Low-k Dielectrics. Peng Zhang, Brenda Ross, Bridget Horvath, John A. Marsella, Gary Johnson Air Products and Chemicals Daniel Koos, Frank Huang, Marie Mitchel Novellus Systems. Outline. Surface Treatment Solutions in Post-CMP Cleans for Low- k Dielectrics

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Surface Treatment Solutions for Low-k Dielectrics

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  1. Surface Treatment Solutions for Low-k Dielectrics Peng Zhang, Brenda Ross, Bridget Horvath, John A. Marsella, Gary Johnson Air Products and Chemicals Daniel Koos, Frank Huang, Marie Mitchel Novellus Systems

  2. Outline • Surface Treatment Solutions in Post-CMP Cleans for Low-k Dielectrics • Contact Angle Studies • ATR-FTIR Results • Foam Data • Defect Performance • Conclusions

  3. Surfactants in Semiconductor Cleaning Process • Hydrophobic substrate surfaces • Organic materials, low-k • Smaller features

  4. Post-CMP Cleans Challenge for Hydrophobic Low-k Dielectrics • Hydrophobic surface are seen to de-wet during transfer from the polisher to the cleaner. • Additional de-wetting can occur during the rinse / dry process. • De-wetting leads to increase particle counts and associated water marks.

  5. Water Marks on Patterned Wafer

  6. Surface Conditioners in Post-CMP Cleans Reduce defects by wetting the surface in the wafer transfer and rinse/dry process • Have Superior wetting under dynamic conditions • Can be easily removed from substrate surface • Low foaming

  7. Wetting on Low-k dielectric Film Lowest Contact Angle on Low-k Surface

  8. Surface Conditioner A Wetting on Low-k Surface 45 degrees set as acceptable contact angle to wet wafer.

  9. Removal of Surface Conditioner (Low-k Dielectric Surface) Contact Angle of Water

  10. ATR FTIR Technique on Si Crystal Solution flow IR Beam Solution flow Flow Cell

  11. Adsorption Density Calculation A/N = bulk contribution + surface contribution = e Cs de + e (2de/dp) G • A: Absorbance of surfactant molecules • N: number of internal reflections • e: molecular absorptivity • Cs: bulk concentration • de:effective depth • dp: penetration depth of the evanescent wave • G: adsorption density of surfactant (moles/cm2)

  12. Molar Absorptivity of Surfactant ArT = e C P • ArT= Integrated absorbance of a transmission spectrum in the range of 3000-2800 cm-1 • C= Concentration of surfactant solution [M] • P= Transmission cell path length

  13. Surfactant Absorption

  14. Surfactant Adsorption Density Surface Conditioner A Surface Conditioner E

  15. Surface Desorption

  16. Foam Generation Test foam glass frit Mass Flow Controller N2 Supply

  17. Foam Dissipation Test Foam Height ~ ~

  18. Defect Results Film Comparison SC A Cu 3.5 0.87 USG* 2.6 0.85 Coral™ “A” 0.91 0.15 Post-CMP Clean Performance(Surface Conditioner A) Processing Polish Transfer Clean Rinse/Dry Polish Plus Clean Defect Results 2% Solutions  Normalized (Result / Baseline) *Un-doped Silicon Glass “Coral” is a trade mark of Novellus Systems, Inc.

  19. Conclusions • Surface conditioners can be used effectively to wet hydrophobic low-k surface. • They can also be easily removed from the hydrophobic surface without impact on the bulk film properties. • Superior defect performance was obtained in post-CMP cleans.

  20. Acknowledgement • University of Arizona A. Marcia Almanza-Workman, Srini Raghavan

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