Semiconductor wafer position shift measurement and correction

An apparatus for positioning a substrate, comprising:

• an end effector configured to transport the substrate along a path;
• at least one reference mark;
• at least one camera positioned to capture two images, each image including at least one reference mark and a different portion of an edge of the substrate;
• and
• a processor configured to calculate a difference in position of the substrate relative to an ideal substrate position, the processor receiving input from the at least one camera.

An apparatus for positioning a substrate, comprising:

• an end effector configured to transport the substrate along a path;
• at least two reference marks fixed with respect to the end effector;
• at least one camera positioned to capture two images, each image including one of the reference marks and a different portion of an edge of the substrate;
• and
• a processor configured to calculate a position of the substrate relative to the reference marks, the processor receiving input from the at least one camera.

A method of accurately positioning a substrate within a semiconductor processing apparatus, the method comprising:

• moving a substrate along a path with the robot;
• capturing a first image of a first portion of an edge of the substrate and a first reference mark;
• capturing a second image of a second portion of the edge of the substrate and a second reference mark;
• measuring a distance from the respective reference mark to the edge of the substrate for each of the first and second images;
• and
• calculating a positional drift of the substrate with respect to an ideally positioned substrate using the measured distances.

A system for calculating substrate drift upon an end effector, comprising:

• a robot supporting and moving the end effector, the robot configured to move the end effector and a supported substrate along a translational path including a first position and a second position;
• a reference mark;
• a camera fixed with respect to the reference mark, the camera positioned to capture a first image with the substrate in the first position and a second image with the substrate in a second position, each of the first and second images including a reference mark that is fixed with respect to the camera and a different portions of an edge of the substrate;
• and
• a processor configured to calculate a position of the substrate relative to the reference mark, the processor receiving input form the camera and the robot.