WAFER CENTER FINDING WITH A KALMAN FILTER
A number of wafer center finding methods and systems are disclosed herein that improve upon existing techniques used in semiconductor manufacturing.
1 . A device comprising:
a robotic arm for handling a wafer, the robotic arm including one or more encoders that provide encoder data identifying a position of one or more components of the robotic arm; and
a processor adapted to apply an extended Kalman Filter to the encoder data to estimate a position of the wafer.
2 . The device of claim 1 wherein the position includes a wafer center.
3 . The device of claim 1 wherein the position includes a wafer radius.
4 . The device of claim 1 wherein the position is determined with reference to an end effector of the robotic arm.
5 . The device of claim 1 wherein the position is determined with reference to a center axis of the robotic arm.
6 . The device of claim 1 wherein the processor recalculates the position each time new encoder data is received.
7 . The device of claim 6 wherein new encoder data is received at substantially 2 kHz.
8 . The device of claim 1 wherein the processor is adapted to update one or more equations of the Kalman Filter using transition data from one or more sensors that detect the presence of a wafer at one or more predetermined locations within a robotic wafer handler.
9 . A method comprising:
disposing a plurality of sensors within an interior of a wafer handling device, each one of the plurality of sensors capable of detecting a transition between presence and absence of a wafer at a predetermined location within the interior;
handling a wafer with a robotic arm, the robotic arm including one or more encoders that provide encoder data identifying a position of one or more components of the robotic arm; and
applying the encoder data to an extended Kalman Filter to provide an estimated position of the wafer.
10 . The method of claim 9 further comprising:
detecting a transition at one of the plurality of sensor to provide an actual position of the wafer;
determining an error between the actual position and the estimated position; and
updating one or more variables for the extended Kalman Filter based upon the error.
11 . The method of claim 10 wherein applying the encoder data includes calculating a wafer position every 0.5 milliseconds.
12 . The method of claim 9 wherein the estimated position of the wafer includes a center of the wafer.
13 . The method of claim 9 wherein the estimated position of the wafer includes a radius of the wafer.
14 . The method of claim 9 wherein the estimated position of the wafer is determined with reference to an end effector of the robotic arm.
15 . The method of claim 9 wherein the estimated position is determined with reference to a center axis of the robotic arm.
16 . The method of claim 9 wherein the plurality of sensors includes four sensors.
17 . The method of claim 9 wherein applying encoder data includes recalculating the estimated position each time encoder data is received.
18 . The method of claim 9 wherein handling a wafer includes moving the wafer between two openings to the wafer handling device.
19 . The method of claim 9 wherein handling a wafer includes moving the wafer between a load lock and a process module.
20 . The method of claim 9 wherein handling a wafer includes moving the wafer between a first process module and a second process module.