Browse Prior Art Database

Sensing of Carrier Supported Wafers

IP.com Disclosure Number: IPCOM000090737D
Original Publication Date: 1969-Jun-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Sedlak, JW: AUTHOR

Abstract

The system detects the presence of wafer 1 on support or conveyor 2 having approximately the same optical characteristics of reflectivity. The necessary physical parameters of the system are calculated from the equation D = T/sin alpha or T = D sin alpha where phi is the angle of incidence, alpha equals 90 degrees - phi, T is the wafer thickness, and D equals separation of the light beams.

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Sensing of Carrier Supported Wafers

The system detects the presence of wafer 1 on support or conveyor 2 having approximately the same optical characteristics of reflectivity. The necessary physical parameters of the system are calculated from the equation D = T/sin alpha or T = D sin alpha where phi is the angle of incidence, alpha equals 90 degrees - phi, T is the wafer thickness, and D equals separation of the light beams.

The system includes collimated light source 4 projected at an angle to wafer surface 5 from which it is reflected to photocell sensor 3. Positioned in front of sensor 3 is divergent lens 6 which permits light beam 7 reflected from surface 5 to pass through to sensor 3 via the lens 6 axis. In the absence of a wafer, the light is reflected off support 2 as beam 8 and passes off-axis through lens 6 which causes beam 8 to diverge and miss sensor 3.

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