公开(公告)号：CA996263A

公开(公告)日：1976-08-31

申请号：CA174375

申请日：1973-06-19

Applicant: IBM

Inventor： BENANTE JOSEPH F ,  DONOFRIO NICHOLAS M ,  LINTON RICHARD H

IPC: G11C11/412 ,  G01R31/27 ,  G01R31/28 ,  G11C29/00 ,  G11C29/50 ,  G11C29/56

Abstract: The electrical characteristics of a field effect transistor (FET) of a memory cell connected to a ZERO bit line and of an FET of the memory cell connected to a ONE bit line are determined through applying a substantially constant voltage to one of the ZERO and ONE bit lines while changing the voltage condition on the other of the bit lines. In one embodiment, the FET is a load device of the memory cell and has its source electrode connected to one of the bit lines and also to the drain electrode of another FET, which has its gate electrode connected to the other of the bit lines and functions as an active device of the cell. A substantially constant voltage is applied to the gate electrode through one of the bit lines to inactivate the FET which has its drain electrode connected to the source electrode of the FET having its electrical characteristics determined. The other of the bit lines is discharged for a predetermined period of time and then allowed to charge for another predetermined period of time. The measurement of this charged voltage will indicate whether the FET, which is the load device, is connected to the bit line and has the desired gain and whether the leakage current through the bit line is too high. In the other embodiment, a substantially constant voltage is applied to an FET which is the active device and has its drain electrode connected to one of the bit lines to have a substantially constant voltage applied thereto while its gate electrode is connected to the other of the bit lines to have two different voltages applied thereto. The difference in current flow through the active FET having the two different voltages applied to its gate electrode is employed to determine the threshold voltage of the FET.