PURPOSE: To detect the presence of a defective cell by analyzing current-voltage characteristic by using a test equipment which is the same as a memory array to be evaluated, except when each cell is connected in parallel. ;CONSTITUTION: In a test equipment 10, to which access can be performed from the outside by single pads 15, 18, and 21, an electric stress is applied to the gate oxide layers of EPROM, EEPROM, and flash EEPROM memories, so that electrons can be extracted from the floating gate region of a deflective cell, and a threshold characteristic of the cell are changed, while the charge of a non-defective cell remains without being charged. Then, a voltage lower than the threshold is applied, and drain currents related to the presence of at least one defective cell in an equipment passing through the cell are measured. The measurement and analysis of the current-voltage characteristic are conducted for deciding the number of defective cells. Gate currents can be measured indirectly through the measurement of the drain and source currents of the cells, and the detection of the defective cells can be attained.;COPYRIGHT: (C)1995,JPO
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