Defective Behaviour of an 8T SRAM Cell with Open Defects

The defective behaviour of an 8T SRAM cell with open defects is analyzed. Full and resistive open defects have been considered in the electrical characterization of the defective cell. Due to the similarity between the classical 6T SRAM cell and the 8T cell, only defects affecting the read port transistors have been considered. In the work, it is shown how an open in a defective cell may influence the correct operation of a victim cell sharing the same read circuitry. Also, it is shown that the sequence of bits written on the defective cell prior to a read action can mask the presence of the defect. Different orders of critical resistance have been found depending on the location of the open defect. A 45nm technology has been used for the illustrative example presented in the work.