Apparatus for automatically measuring the resistivity of semiconductor boules by using the method of four probes

An automated measurement system for measuring resistivity of semiconductor boules according to a four probe methodology, comprising

• a four point probe with a home position, said probe configured with 3 axis linear motion capability and at least 1 axis rotation capability, said linear motion capability and said rotation capability connected to a power source and controlled by a computer processor, said four point probe connected to a current source and a current sensor according to said four probe methodology, and further connected to and controlled by said computer processor for departing from and returning to said home position,
• a boule support grid for supporting a boule with a first face end and a second face end in a horizontal orientation with said first face near said home position, and with said first face and the underside surface centerline and said second face exposed for access by and within reach of said four point probe,
• at least one boule surface sensor on said four point probe for detecting proximity of said four point probe to a surface of said boule,
• said computer processor having program steps for directing a boule locating sequence by said four point probe and said sensor from said home position to said first face and to said underside surface centerline and to said second face, and for deriving boule diameter and boule length there from,
• said computer processor having program steps for testing a selected point on said boule with said four point probe and calculating a set current according to said four probe methodology,
• said computer processor having program steps for conducting radial resistivity measurements with said four point probe of at least one said face of said boule, and
• said computer processor having program steps for conducting axial resistivity measurements with said four point probe of said underside surface centerline of said boule.
• said system further comprising a frame with spaced apart parallel boule support rails, said boule support grid comprising fore and aft end boule supports attached to each said boule support rail so as to form a four point support grid, said fore end boule supports located proximate said home position,
• said system further comprising a probe carriage to which said probe is attached, said probe carriage having said 3 axis linear motion capability, said 3 axis linear motion comprising lengthwise of said frame motion as X axis, crosswise of said frame motion as Y axis and vertical motion as Z axis motion, said four point probe being mounted by a probe shaft on a Z axis adjustable support post on said probe carriage, said frame further comprising at least one X axis carriage rail upon which said probe carriage travels, said probe carriage having at least one Y axis rail upon which said four point probe travels, said rotational capability centered on said probe shaft, said system further configured with stepper motors connected to said computer processor for rotating and moving said four point probe and moving said probe carriage.
• said system being substantially enclosed and having a cover closable over a said boule on said support grid.