Apparatus and method for optical calibration of wafer placement by a robot

A method of processing a workpiece, comprising:

• providing a reactor chamber body having an open top and a workpiece support inside said reactor chamber body;
• placing a first lid on said open top, setting chamber pressure in said reactor chamber body to a selected level, and robotically placing a workpiece on said workpiece support;
• capturing, through said first lid, respective images of portions an edge of said workpiece and an edge of a reference feature in said reactor chamber body in respective fields of view spaced at periodic locations relative to a circumference of said workpiece support and determining a non-concentricity between said workpiece and said reference feature;
• if said non-concentricity exceeds a predetermined threshold, determining from said respective images a correction vector representing a change in location of said workpiece corresponding to a decrease in non-concentricity between said workpiece and said reference feature, and robotically shifting said workpiece in accordance with said correction vector, and then repeating said capturing, determining and shifting;
• and
• if said non-concentricity is less than the predetermined threshold, storing a present location of the workpiece, replacing said first lid with a second lid comprising process features, establishing process conditions in said reactor chamber body, and robotically placing each one of a succession of workpieces on said workpiece support at said present location.

An assembly for calibrating robotic placement of a workpiece having a workpiece edge onto a workpiece support surface having a support edge, said assembly comprising:

• a reactor chamber body having a top opening and containing said workpiece support surface;
• a lid removably installable on said reactor chamber body and comprising top and bottom surfaces, said bottom surface comprising a sealing shoulder receivable on said top opening, and plural viewing ports extending through said lid along a direction transverse to said top and bottom surfaces;
• plural cameras mounted on said lid along respective axes, and having respective fields of view through respective ones of said plural viewing ports, said respective fields of view coinciding with respective intersections of said support edge and respective ones of said axes;
• and
• a processor coupled to receive from said cameras images of said support edge and of said workpiece edge, corresponding to workpiece edge-to-support edge distances along respective ones of said axes.