Self-calibration system for robot mechanisms

• US 5,535,306 A
• Filed: 02/14/1995
• Issued: 07/09/1996
• Est. Priority Date: 01/28/1993
• Status: Expired due to Term

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Stevens, Craig L.
• Primary Examiner(s): Downs, Robert W.
• Application Number:
  US08/389,090
• Time in Patent Office: 511 Days
• Field of Search: 395/89, 395/94, 395/93
• US Class Current: 700/254
• CPC Class Codes: B25J 9/1692 Calibration of manipulator
• CPC Class Codes: G05B 2219/36404 Adapt teached position as function of deviation 3-D, 2-D position workpiece
• CPC Class Codes: G05B 2219/45026 Circuit board, pcb
• CPC Class Codes: G05B 2219/50019 Zero, null offset
• CPC Class Codes: G05B 2219/50024 Go to reference, switches and dog to decelerate and to detect origin

Abstract

A method and apparatus for calibrating a robot for differences between the actual and predicted positions of a robot chamber with respect to the robot, and for differences between the actual and predicted positions of a processing chamber with respect to the robot. A substrate support on the robot is first moved angularly across a fixed sensor in the robot chamber, to detect the actual position of the sensor in terms of angle, and second is moved radially out across the fixed sensor to detect actual position in terms of radius with respect to a center of rotation. The difference, if any, between the actual and predicted positions of the sensor is used to calibrate a home position of the robot. A similar technique is used to calibrate the robot for any discrepancy between the actual and predicted positions of a processing chamber adjoining the robot chamber.

Claims

1. A method for automatically calibrating a robot capable of movement in two position axes and installed in a robot chamber, comprising the steps of:

moving a robot component to a position adjacent to a fixed sensor in the robot chamber;

moving the robot component along a selected position axis and across the fixed sensor;

detecting when at least one feature of the robot component trips the fixed sensor, and recording a robot position in the selected position axis along which the robot was moved across the fixed sensor;

computing the difference between the robot position recorded in the immediately preceding recording step and a predicted robot position at which the fixed sensor should be tripped;

applying the difference value computed in the immediately prior computing step to calibrate the robot in the selected position axis; and

repeating all of the foregoing steps for another selected position axis of the robot.

2. A method as defined in claim 1, and further comprising the steps of:

picking up a workpiece from a selected processing chamber adjoining the robot chamber;

moving the workpiece across the fixed sensor along each position axis in turn;

detecting at least one feature of the workpiece as the workpiece is moved across the fixed sensor along each position axis;

computing the difference, for each position axis, between the position of the workpiece detected in the immediately preceding detecting step and a predicted position of the workpiece; and

applying the differences obtained from the immediately prior computing step, to adjust a predicted position of the selected processing chamber.

3. A method for automatically calibrating a robot capable of movement in two axes and installed in a robot chamber, the robot being capable of moving a substrate support angularly and radially with respect to an axis, the method comprising the steps of:

moving the robot to an angular position such that the substrate support is positioned adjacent to a fixed sensor in the robot chamber;

moving the substrate support angularly across the fixed sensor;

detecting when at least one edge of the substrate support trips the fixed sensor, and recording an angular position of the robot;

computing the difference between the angular position of the robot recorded in the immediately preceding recording step and a predicted robot angular position at which the fixed sensor should be tripped;

applying the difference value computed in the prior immediately computing step to calibrate the robot in angular position;

moving the substrate support such that a front edge of the substrate support is adjacent to the fixed sensor;

moving the substrate support radially out across the fixed sensor;

detecting when at least one feature of the front edge of the substrate support trips the fixed sensor and recording a radial position of the robot;

computing the difference between the radial position of the robot recorded in the immediately preceding recording step and a predicted robot radial position at which the fixed sensor should be tripped; and

applying the difference value computed in the immediately prior computing step to calibrate the robot in radial position.

4. A method as defined in claim 3, wherein:

the step of detecting when at least one edge of the substrate support trips the fixed sensor, when moving the substrate support angularly across the fixed sensor, includes detecting when each of two opposite side edges of the substrate support trips the fixed sensor, determining angular positions corresponding to detection of tripping the fixed sensor by the two opposite side edges of the substrate support, and averaging the two angular positions.

5. A method as defined in claim 3, wherein:

the step of detecting when at least one feature of the front edge of the substrate support trips the fixed sensor includes detecting when each of two leading tips of the front edge trips the fixed sensor, determining angular positions corresponding to detection of tripping of the fixed sensor by the two leading tips of the front edge, and averaging the two radial positions.

6. A method as defined in claim 3, and further comprising the steps of:

picking up a substrate from a selected processing chamber adjoining the robot chamber;

moving the substrate across the fixed sensor in a radial direction;

detecting at least one edge of the substrate as the substrate is moved radially across the fixed sensor and thereby deriving a detected radial position of the substrate;

computing the difference between the detected radial position of the substrate and a predicted radial position of the substrate;

applying the difference obtained from the immediately prior computing step, to adjust a predicted radial position of the selected processing chamber;

moving the substrate angularly across the fixed sensor;

detecting at least one edge of the substrate as the substrate is moved angularly across the fixed sensor and thereby deriving a detected angular position of the substrate;

computing the difference between the detected angular position of the substrate and a predicted angular position of the substrate; and

applying the difference obtained from the immediately prior computing step, to adjust a predicted angular position of the selected processing chamber.

7. A method as defined in claim 6, wherein:

the step of detecting at least one edge of the substrate as the substrate is moved angularly across the fixed sensor includes detecting each of two opposite side edges, determining angular positions corresponding to tripping of the fixed sensor by the two opposite side edges, and averaging the two angular positions.

8. Apparatus for automatically calibrating a robot capable of movement in two axes and installed in a robot chamber, comprising:

a robot mechanism installed in a robot chamber and including a movable workpiece support and means for moving the workpiece support in at least two dimensions;

a sensor fixed to the robot chamber in a known position;

means for moving the workpiece support to a position adjacent to the sensor;

means for next moving the workpiece support along a first position axis and across the sensor;

means for detecting when at least one feature of the workpiece support trips the sensor, and recording a robot position in the first position axis;

means for computing the difference between the robot position in the first position axis recorded in the immediately preceding means for detecting and recording, and a predicted robot first-axis position at which the sensor should be tripped;

means for applying the difference value computed in the means for computing, to calibrate the robot in the first position axis;

means for next moving the workpiece support along a second position axis and across the sensor;

means for detecting when at least one feature of the workpiece support trips the sensor, and recording a robot position in the second position axis;

means for computing the difference between the robot position in the second position axis recorded in the immediately preceding means for detecting and recording, and a predicted robot second-axis position at which the sensor should be tripped; and

means for applying the difference value computed in the immediately preceding means for computing, to calibrate the robot in the second position axis.

9. Apparatus as defined in claim 8, and further comprising:

means for picking up a workpiece from a selected processing chamber adjoining the robot chamber;

means for moving the workpiece across the sensor along each position axis in turn;

means for detecting at least one feature of the workpiece as the workpiece is moved across the sensor along each position axis;

means for computing the difference, for each position axis, between the position of the workpiece detected by the means for detecting at least one feature of the workpiece and a predicted position of the workpiece; and

means for applying the differences obtained from the means for computing the difference between the position of the workpiece and the predicted position of the workpiece, to adjust a predicted position of the selected processing chamber.

10. Apparatus for automatically calibrating a robot capable of movement in two axes and installed in a robot chamber, the apparatus comprising:

means for moving a substrate support in the robot to a selected angular position and a selected radial position with respect to a fixed axis;

a sensor fixed in the robot chamber, and capable of detecting the presence of the edge of an object moved across the sensor; and

calibration control means, including;

means for moving the substrate support to an angular position adjacent to the sensor;

means for moving the substrate support angularly across the sensor;

means for detecting when at least one edge of the substrate support trips the sensor, and recording an angular position of the robot;

means for computing the difference between the angular position of the robot recorded in the immediately preceding means for detecting and recording, and a predicted robot angular position at which the sensor should be tripped, and applying this difference value to calibrate the robot in angular position;

means for moving the substrate support such that a front edge of the substrate support is adjacent to the sensor;

means for moving the substrate support radially out across the sensor;

means for detecting when at least one feature of the front edge of the substrate support trips the sensor and recording a radial position of the robot; and

means for computing the difference between the radial position of the robot recorded in the immediately preceding means for detecting and recording, and a predicted robot radial position at which the sensor should be tripped, and applying this difference value to calibrate the robot in radial position.