Cell signal measurement for high-density DRAMs

Abstract

Important parameters for scaling high-density DRAMs are the cell signal of each memory cell and the signal level applied to the sense amplifier during sensing. Moreover, failing memory cells need to be 'characterized' before a physical failure analysis can be carried out in order to determine the root causes of likely problems. It is common practice to put small pads on the bit lines (BLs) and probe the bit-line signal with so-called pico-probes. This paper describes a new approach to measuring the cell signal using a normal test procedure without pico-probes. Measurements determine the cell signal, BL, word line (WL) and isolator coupling.