Angular orientation and alignment from the wafer notch
The wafer seats on a rotary table; its notch is located in the backlit outer contour. The notch angle is compared with the reference and the table corrects wafer orientation.
Notch coordinates and angular error are sent to motion control; the table corrects wafer orientation. The remeasured angle determines release for subsequent handling.
- 01 Seat
- 02 Acquire
- 03 Locate angle
- 04 Correct
- 05 Verify
The wafer seats on the central chuck.
- Notch angle
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- Angular error
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Scenes are illustrative simulations; they are not customer references or performance guarantees.
Need
The wafer perimeter is largely circular; its small notch can be confused with a reflection or carrier edge. Without an angular reference, subsequent handling uses the wrong orientation.
Solution approach
The overhead camera images the wafer perimeter outside the central chuck as a backlit silhouette. An inward departure from the circle identifies the notch; its direction from the centre is compared with the reference and an angular correction is sent to the rotary table.
Process steps
- 01
Seat
The wafer seats on the central chuck.
- 02
Acquire
The backlight reveals the outer contour.
- 03
Locate angle
The notch direction is compared with the reference.
- 04
Correct
The table removes the measured angular error.
- 05
Verify
The corrected orientation is checked again.
Related applications
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