Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – With rotor
Patent
1986-05-19
1987-09-08
Karlsen, Ernest F.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
With rotor
324158D, 361212, G01R 3126, H05F 300
Patent
active
046926950
ABSTRACT:
A conductivity-type sensor, typically for use in a wafer sorting system, for detecting the conductivity-type of semiconductor wafers. In measuring conductivity, a two-contact probe is applied to the semiconductor wafer and any static charge which may have been accumulated on the wafer is initially discharged at an accelerated rate. The charge state is measured and an acceptable level of discharge requires repeated indications of discharge below a predetermined level. Discharging and charge measurement is repeated a predetermined number of times as necessary to accomplish discharging or the wafer identified as defective. The conductivity-type of the discharged wafer is read from the rectified polarity of an oscillating signal applied to the contacts. A valid indication of conductivity-type requires two consecutive readings of the same conductivity-type. The consecutive readings can be either the first reading of a new wafer identical with the reading of a previous wafer or two consecutive identical readings on the same wafer. Each reading, to be considered an acceptable reading of conductivity-type requires five consecutive, identical conductivity measurements over a predetermined time interval. Failure of such criteria produces a wafer defect indication.
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Kiethley Instruments catalog; Kiethley Instruments, 3868 Carnegie Ave., Cleveland, Ohio; 1955; pp. 1-12.
ADE Corporation
Karlsen Ernest F.
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