摘要 |
A method and apparatus for measuring a slurry distribution. A slurry solution is doped with a light absorbing dye having an absorptivity sensitive to a physical parameter such as acidity, temperature or pressure. The solution is delivered between a platen and substrate in a first physical state where it absorbs light. A laser beam is generated, transmitted through the slurry layer, reflected off of the substrate, and detected by a photodetector. The thickness of the slurry is measured from its absorptivity and the transmittance of the laser beam. A relative motion between the light source and substrate allows the slurry layer thickness to be measured as a function of distance from the center of the substrate. A final water rinse removes the slurry and brings any residual slurry to a/second physical state where it does not absorb light.
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