System and method for automated positioning of a substrate in a processing chamber

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 1.
Overview of The System Assembly Although the following description describes the invention in terms of a semiconductor wafer, this is for illustration purposes only and other substrates or objects to be transferred to a preselected location can be substituted therefor, as will be known to one skilled in the art.
FIG.
1 of the accompanying drawing is a diagrammatic representation of a multi-chamber, semiconductor wafer processing system including a wafer robot centerfinding and calibration system and method in accordance with the present invention.
The system shown generally at i includes a transfer chamber 2 having at least two integrally attached wafer receiving chambers 3a (e.
g.
, a loadlock chamber) and 3b (e.
g.
, a wafer processing chamber) having centrally located, optimal position points 65a and 65b respectively.
During processing, the wafer should be centered over these positions 65a and 65b.
A wafer transfer means such as the R-theta robot 4 having a wafer support blade 4a, is shown with a semiconductor wafer 5 in transfer position thereon.
A photoelectric sensor array preferably including four sensors connected to a sensor electronics assembly 8 (shown separated by way of example from sensor array 6 for the convenience of component illustration) and having a power supply 9, the assembly 8 being connected to a sensor interface card 11 receivingly engaged within a processing means 12.
The processing means also includes a robot motor control interface card 13 connected to a robot motor interface (terminal) board 15 having connected to it a motor driver 16a connected to a first robot motor 17a (FIG.
2), and a second motor driver 16b connected to a second robot motor 17b (FIG.
2).
The terminal board 15 is also connected to robot motor encoders 18a and 18b.
Processing means 12 also includes a digital input/output card 19 which is connected to a robot "home" sensor 19a (not shown).
Sensor array 6 is preferably positioned between a pair of chambers 3a and 3b such that the centerfinding method of this invention, more fully described hereinbelow, can be performed during normal wafer transfer operation