Electrical characterization of contact level PVC (Passive Voltage Contrast) test using a nanoprober

PVC (Passive Voltage Contrast) fault isolation method by using a SEM (Scanning Electron Microscope) has been widely used for isolating the defective mc (metal contact) in the CMOS logic SRAM bit cell array. The low power (LP) processed sram cells are easy to charging under PVC test and it helps isolating defective contacts in the cell. However, some device such as a high speed (HS) sram cell is hard to charging in PVC test by unknown reason. It makes difficulties for isolating defective contacts in the sram cell array. In this paper, our group analyzed the electrical current of each contact in sram cell using a nanoprobing technique and correlated it with PVC charged contact images, respectively. Also, the difference of PVC charging status between LP and HS SRAM are characterized electrically by using a nanoprober. The nanoprobing result indicates that a slight increasing a leakage current of about 10pA can abruptly change the charging brightness from dark to grey. Finally, we can found some clues for making grey contacts of HS SRAM using not only a nanoprobing but also a HRTEM (High Resolution Transmission Electron Microscope) image.