Analysis of flow between a wafer and pad during CMP processes |
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Authors: | C Rogers J Coppeta L Racz A Philipossian F B Kaufman D Bramono |
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Affiliation: | (1) Department of Mechanical Engineering, Tufts University, Medford, MA;(2) Intel Corporation, Santa Clara, CA;(3) Cabot Corporation, Aurora, IL |
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Abstract: | In this paper, we summarize the development of a numerical model for the chemical mechanical planarization (CMP) process and
experimentally investigate the effects of pad conditioning on slurry transport and mixing. A simplified two-dimensional numerical
model of slurry flow beneath a stationary wafer was developed to determine the pressure and shear stress beneath a wafer.
The initial results indicate that in the hydrodynamic regime a positive upward pressure is exerted on the wafer. We also examined
three cases to study pad effects on slurry transport; polishing with an Embossed Politex pad, an unconditioned IC1000 pad,
and a conditioned IC1000 pad. Cab-O-Sperse SC1 slurry was used in a 1:1.5 dilution with water. Mixing data show that conditioning
has a negligible effect on the rate of slurry entrainment and mixing; however, conditioning has a large effect on the thickness
of the slurry layer between the wafer and pad. Conditioning was found to increase the slurry thickness by a factor of two.
In addition the gradients in slurry age beneath the wafer were compared among the three cases. The IC1000 pads supported a
gradient in the inner third of the wafer only, while the Embossed Politex pad showed a linear gradient across the wafer implying
it retains pockets of unmixed slurry in the embossed topography. |
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Keywords: | Chemical mechanical planarization (CMP) chemical mechanical polishing CMP numerical simulation dual emission laser induced fluorescence |
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