Browse Prior Art Database

Automatic Wafer Contamination Measurement System

IP.com Disclosure Number: IPCOM000076758D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Hannan, J: AUTHOR [+4]

Abstract

Particulate contamination on semiconductor wafers is automatically sensed during integrated circuit manufacture with an optical system employing polarized light.

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Automatic Wafer Contamination Measurement System

Particulate contamination on semiconductor wafers is automatically sensed during integrated circuit manufacture with an optical system employing polarized light.

The sensing unit 1 is put into the manufacturing line at any desired point by including a self-centering air track section 2. The unit has a wafer sensor 12. Light source 3 comprises a tungsten lamp 4 whose output is kept constant by a closed-loop control 5 incorporating a photosensor and SCR lamp driver. Collimated light is directed onto the wafer surface by mirror and filter assembly 6, including polarizer 7. A TV camera 8 is placed to monitor the surface of wafer 9. Camera 8 is equipped with optic assembly 10 including polarizer 11. Polarizer 11 is positioned in a manner to cancel the partially polarized light being reflected from the surface of wafer 9, and in a position 90 degrees out of orientation with polarizer 7. This provides a dark area that represents the planar surface of wafer 9, with the nonplanar dirt particles standing out as bright spots on a black field. The light spots, which represent the particulate contamination, are picked up by camera 8. The camera output is electromatically monitored by signal translator and control 14. The signals generated by the bright spots during a complete sweep of the wafer surface are sorted out by amplitude or duration, to indicate the size of the dirt particles. The particles are counted or summed to ind...