Automatic calibration system for wafer transfer robot

A method for automatically calibrating the positioning of a wafer handling robot wand to a desired location within an enclosure forming a process station and having elongated opening, said robot having an articulated arm that is movable in the vertical (Z), angular (.theta.), and radial (R) directions and is connected to a controller having memory and logic sections, said robot wand being rotatable at the end of said arm and having a first sensor at one end thereof and said process station having a second sensor within the opening of said enclosure, said method including the steps of:

• 1--providing said controller memory with dimensional characteristics of said wand and said process station;
• 2--programming said controller to cause said robot to move in a series of sequential movements;
• 3--rotating said wand 180.degree. so that said first sensor faces said opening of said process station;
• 4--causing said robot to move in the Z direction to determine one edge of said station opening and providing its measurement as a rough Z (Z.sub.rough) calibration to said controller;
• -- returning said robot wand to a preset normal position;
• 6--moving the robot to an initial calibration position within said opening using said second sensor within said enclosure;
• 7--moving the wand in first one angular (theta) direction and then in the opposite angular direction within said enclosure to determine the desired .theta..sub.cal position for the wand;
• 8--moving the wand to the initial calibration position based on R.sub.non, .theta..sub.cal and Z.sub.rough ;
• 9--moving the wand in the negative R direction until said second sensor is activated;
• 10'defining the Rcal distance by combining the R sensed position with the stored enclosure dimensions;
• 11--moving the wand to the initial calibration position with its sensor spaced from the enclosure opening based on R.sub.cal, .theta..sub.cal and Z.sub.rough ;
• 12--moving the robot wand in the negative Z direction;
• 13--measuring the Z position when the wand sensor passes a horizontal inner edge of the opening;
• 14--defining the Z.sub.cal position by adding dimensional values of the wand and enclosure.
• 15--returning the wand to its normal position;
• 16--moving the wand into the station opening to the position defined by Z.sub.cal, .theta..sub.cal and R.sub.cal.

A method for automatically calibrating the positioning of a wafer handling robot wand to a desired location within an enclosure forming a process station and having an elongated opening, said robot having an articulated arm that is movable in the vertical (Z), angular (.theta.), and radial (R) directions and is connected to a controller having memory and logic sections, said process station enclosure having a first sensor that provides a horizontal beam across mid opening and a second sensor that provides a vertical beam across said opening at its mid-point, said method comprising the steps of:

• 1--moving the robot arm manually to a rough Z and R position with said wand extending through said opening;
• 2--moving the wand in an angular direction to a first position and then in the opposite direction relative to said second sensor to record .theta., and .theta..sub.2 positions to determine the desired .theta..sub.cal position for the wand;
• 3--moving the wand in a negative R direction to activate said second sensor;
• -- defining the R.sub.cal distance by combing the R sensed position with the enclosure dimensions;
• 5--moving the wand in the negative Z direction to engage the horizontal beam of the first sensor to provide a signal to the controller;
• 6--using the signal from the first sensor and stored dimensional values of the wand and the enclosure to determine Z.sub.cal position for the wand;
• and
• 7--moving the wand into the enclosure opening to the position defined by Z.sub.cal, .theta..sub.cal and R.sub.cal.