Effect of slurry composition on the chemical mechanical polishing of thin diamond films

Abstract

Nanocrystalline diamond (NCD) thin films grown by chemical vapour deposition have an intrinsic surface roughness, which hinders the development and performance of the films’ various applications. Traditional methods of diamond polishing are not effective on NCD thin films. Films either shatter due to the combination of wafer bow and high mechanical pressures or produce uneven surfaces, which has led to the adaptation of the chemical mechanical polishing (CMP) technique for NCD films. This process is poorly understood and in need of optimisation. To compare the effect of slurry composition and pH upon polishing rates, a series of NCD thin films have been polished for three hours using a Logitech Ltd. Tribo CMP System in conjunction with a polyester/polyurethane polishing cloth and six different slurries. The reduction in surface roughness was measured hourly using an atomic force microscope. The final surface chemistry was examined using X-ray photoelectron spectroscopy and a scanning electron microscope. It was found that of all the various properties of the slurries, including pH and composition, the particle size was the determining factor for the polishing rate. The smaller particles polishing at a greater rate than the larger ones.

Keywords:

• Chemical mechanical polishing
• nanocrystalline diamond
• surface roughness
• chemical vapour deposition

Classification:

• 40 Optical, magnetic and electronic device materials
• 301 Chemical syntheses / processing
• 212 Surface and interfaces
• 303 Mechanical / Physical processing
• 306 Thin film / Coatings

Acknowledgements

The authors wish to acknowledge the financial support of the European Research Council (ERC) Consolidator Grant for the development of ‘Superconducting Diamond Quantum Nano-Electro-Mechanical Systems’, Project ID: 647471.

Notes

No potential conflict of interest was reported by the authors.