| 摘要 |
PURPOSE:To automatically rank semiconductor integrated circuits by providing a memory for storing data of parametric items in a wafer test, calculating data distributed state from the data stored in the memory in n rank, and selecting the data. CONSTITUTION:The measurement of parametric items for chips is executed for all good chips of many chips contained in a wafer 1, and obtained data are temporarily stored in a data memory 3. A testing unit 2 contains a calculator, and reads out the data stored in the memory 3 at a wafer unit after the measurements of all good chips contained in the same wafer 1 are finished to collect irregularity distribution designated by the data. The calculator further contains a comparator which registers in advance the data of the irregularity distribution to become a reference value for ranking the wafers in n ranks to compare the irregularity distribution collected in the comparator with the registered reference value. A signal for deciding the rank is applied to the wafer 1 to be selected on the basis of the compared result.
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