Reading Contrast of Phase-Change Electrical Probe Memory in Multiple Bit Array

Reading contrast of phase-change electrical probe memory is investigated using a newly developed electrical switching model that accurately mimics the threshold switching of the phase-change media. Multiple bit array in either crystalline or amorphous phase is introduced into the model to take into account the influence of the readout cross-talk arising from inter-bit and inter-track interferences. Based on this configuration, the reading contrast is calculated by properly tailoring the electrical and geometrical properties of the capping, phase-change, and bottom layers as well as varying the length of the bit and track pitch. We found that the reading contrast can be significantly enhanced using an ultra-thin phase-change layer sandwiched by an ultra-thin capping layer with an intermediate electrical conductivity, and a relatively thick bottom layer with ultra-high electrical conductivity, as well as maintaining the length of the bit and track pitches similar to the size of the electrical probe. An optimized media stack that is also experimentally achievable from the state-of-the-art film deposition technologies is proposed, enabling a reading contrast of 0.85 for crystalline bit array and of 0.68 for amorphous bit array, close to those induced from isolated bit configuration immune to readout cross-talk. In order to thoroughly eliminate the adverse effect caused by readout cross-talk, the concept of patterned probe phase-change memory is introduced and its practicality for further alleviating the reading contrast is briefly discussed.