Design of n(+)-base width of two-terminal-electrode vertical thyristor for cross-point memory cell without selector

Abstract

The n(+)-base width of a two-terminal vertical thyristor fabricated with n(++)(top-emitter)-p(+)(base)-n(+)(base)-p(++)(bottom-emitter) epitaxial Si layers was designed to produce a cross-point memory cell without a selector. Both the latch-up and latch-down voltages increased linearly with the n(+)-base width, but the voltage increase slope of the latch-up was 2.6 times higher than that of the latch-down, and the memory window increased linearly with the n(+)-base width. There was an optimal n(+)-base width that satisfied cross-point memory cell operation; i.e. similar to 180 nm, determined by confirming that the memory window principally determined the condition of operation as a cross-point memory cell (i.e. one half of the latch-up voltage being less than the latch-down voltage and a sufficient voltage difference existing between the latch-up and latch-down voltages). The vertical thyristor designed with the optimal n(+)-base width produced write/erase endurance cycles of similar to 10(9) by sustaining a memory margin (I-on/I-off) of 10(2), and the cross-point memory cell array size of 1024 K sustained a sensing margin of 99 %, which is comparable with that of current dynamic random-access memory (DRAM). In addition, in the cross-point memory cell array, a 1/2 bias scheme (i.e. a memory array size of 1024 K for 0.02 W of power consumption) resulted in lower power consumption than a 1 / 3 <i bias scheme (i.e. a memory array size of 256 K for 0.02 W of power consumption).