Patent ID: 7357694

Claim:
An optical concentration sensor for measuring a moving abrasive slurry associated with a singulation engine capable of cutting semiconductor substrates, the optical concentration sensor comprising: an inlet coupling configured to receive a moving slurry delivered from a slurry source; an outlet coupling configured to let out the moving slurry; a housing that defines a slurry passage therein, the slurry passage being configured to distribute the moving slurry from the inlet coupling to the outlet coupling, the housing including one or more windows that provide optical access to the slurry passage, the windows being formed from a light passing material that substantially withstands the moving abrasive slurry and does not contribute to contamination of the moving abrasive slurry; a light source configured to direct light into the slurry passage through the window, the light being configured to intersect the abrasive slurry moving through the slurry passage; and one or more light detectors configured to detect light traveling out of the slurry passage through one or more windows, the light detectors producing signals in accordance with the light intensity of the light traveling out of the slurry passage through the one or more windows, the light intensity varying in accordance with the concentration of the moving abrasive slurry.