Apparatus for aligning substrates for loading and unloading using a robot mechanism
First Claim
1. A method for aligning a robot arm with a workpiece having a straight edge, the method comprising:
- positioning the robot arm adjacent to a predicted workpiece location;
moving the robot arm toward the workpiece in a direction predicted to be perpendicular to a straight front edge of the workpiece;
sensing the location of the straight front edge with at least two sensors installed on the robot arm, wherein each of the at least two sensors will provide a different location solution if the straight front edge is not perpendicular to the direction of robot arm movement toward the workpiece;
calculating, from the location solutions provided by the at least two sensors, an angular correction needed to be applied to the robot arm such that it will approach the front edge of the workpiece perpendicularly; and
calculating from the angular correction a corresponding linear correction needed to be applied to the robot arm, because of the angular correction, to ensure that the robot arm will approach the workpiece at a desired relative location.
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Abstract
A technique for automatically compensating for differences in orientation of a workpiece, such as a rectangular substrate, a substrate cassette, a loadlock for accessing a vacuum chamber, and a substrate support on a robot mechanism. Sensors on the substrate support detect the position of a front edge of a substrate, a cassette or a loadlock, and measurements taken at the time the sensors are tripped by the edge are used to compute linear, angular and radial position corrections. More specifically, in moving a substrate from a cassette to the loadlock, the substrate support compensates for the orientation of the cassette, compensates for the orientation of the substrate within the cassette, and withdraws the substrate without contact with the cassette walls, and without the need for moving edge guides to orient the substrate. Before placing the substrate in the loadlock, the mechanism translates the substrate past a fixed sensor to determine the substrate position on the substrate support, and makes appropriate corrections to predicted linear and radial positions of the loadlock. The procedure for removing a substrate from the loadlock and placing it in a cassette employs a similar set of steps.
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Citations
22 Claims
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1. A method for aligning a robot arm with a workpiece having a straight edge, the method comprising:
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positioning the robot arm adjacent to a predicted workpiece location; moving the robot arm toward the workpiece in a direction predicted to be perpendicular to a straight front edge of the workpiece; sensing the location of the straight front edge with at least two sensors installed on the robot arm, wherein each of the at least two sensors will provide a different location solution if the straight front edge is not perpendicular to the direction of robot arm movement toward the workpiece; calculating, from the location solutions provided by the at least two sensors, an angular correction needed to be applied to the robot arm such that it will approach the front edge of the workpiece perpendicularly; and calculating from the angular correction a corresponding linear correction needed to be applied to the robot arm, because of the angular correction, to ensure that the robot arm will approach the workpiece at a desired relative location. - View Dependent Claims (2, 3)
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4. A method for picking up a workpiece having a generally rectangular shape from a workpiece container, wherein the precise orientation of the container, and of the workpiece within the container, are unknown, the method comprising the steps of:
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positioning a workpiece support of a robot arm in a location adjacent to a predicted workpiece container location; detecting a front edge of the container with at least two sensors mounted on the workpiece support; applying angular and linear corrections to the workpiece support to align it with the detected position of the container; moving the workpiece support into the container and beneath a workpiece to be picked up; detecting a front edge of the workpiece within the container; applying angular and linear corrections to the workpiece support to align it with the detected position of the workpiece; picking up the workpiece; applying angular and linear corrections to the workpiece support to move the workpiece into alignment with the container; and withdrawing the workpiece from the container. - View Dependent Claims (5, 6, 7, 8, 9)
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10. A method for moving generally rectangular workpiece from a first container to a second container, using a substrate support capable of angular and radial motion about an axis, which is movable linearly, wherein the precise orientation of the containers, and of the workpiece within the first container, are unknown, the method comprising the steps of:
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determining the orientation of the first container, by moving a workpiece support to a predicted linear position adjacent to the container, orienting the workpiece support at a predicted angular position, and advancing the workpiece support radially to detect an edge of the container; correcting the predicted linear and angular positions of the first container; performing the foregoing steps for the second container; moving the workpiece support to the corrected position of the first container and advancing the support radially toward a workpiece in the container; detecting any orientation error of the workpiece in the first container and adjusting the linear and angular positions of the workpiece support to compensate for the orientation error; picking up the workpiece with the workpiece support; re-adjusting, if necessary, the angular and linear positions of the workpiece support to conform with the orientation of the first container; withdrawing the workpiece and workpiece support from the first container without contact with the container; moving the workpiece support to the corrected linear and angular position of the second container; advancing the workpiece support radially into the second container; and placing the workpiece in the second container. - View Dependent Claims (11, 12, 13)
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14. Apparatus for aligning a robot arm with a workpiece having a straight edge, the apparatus comprising:
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means for positioning the robot arm linearly adjacent to a predicted workpiece location; means for moving the robot arm toward the workpiece in a direction predicted to be perpendicular to a straight front edge of the workpiece; at least two sensors installed on the robot arm, for sensing the location of the front edge of the workpiece as the robot arm is moved toward the workpiece, wherein each of the at least two sensors will provide a different location solution if the straight front edge is not perpendicular to the direction of robot arm movement toward the workpiece; means for calculating, from the location solutions provided by the at least two sensors, an angular correction needed to be applied to the robot arm such that it will approach the front edge of the workpiece perpendicularly; and means for calculating from the angular correction a corresponding linear correction needed to be applied to the robot arm, because of the angular correction, to ensure that the robot arm will approach the workpiece at a desired relative location. - View Dependent Claims (15, 16)
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17. Apparatus for picking up a workpiece having a generally rectangular shape from a workpiece container, wherein the precise orientation of the container, and of the workpiece within the container, are unknown, the apparatus comprising:
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means for positioning a workpiece support of a robot arm in a location adjacent to a predicted workpiece container location; edge detection means, including at least two sensors mounted on the workpiece support, for detecting a front edge of the container; means for applying angular and linear corrections to the workpiece support to align it with the detected position of the container; means for moving the workpiece support into the container and beneath a workpiece to be picked up, wherein the sensors detect a front edge of the workpiece within the container; means for applying angular and linear corrections to the workpiece support to align it with the detected position of the workpiece and permit picking up the workpiece in alignment with the workpiece support; and means for applying angular and linear corrections to the workpiece support to move the workpiece into alignment with the container, whereby the workpiece may be withdrawn from the container without unwanted contact. - View Dependent Claims (18, 19, 20, 21, 22)
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Specification