Simulation Of Radiation On Phase Change Memory Cell

Phase change random access memory(PRAM) seems to be one of the most promising candidate in next-generation memories due to its improved performances: long retention time, low power consumption and radiation hardness. PRAM will be widely used in aerospace. PRAM employs the phase change of chalcogenide materials to realize data storage. because of this special data storge, PRAM is supposed to be tolerant to ionizin g radiation effects. so it is of great significance to simulate the irradiation performance of PRAM.The process of proton irradiation is the energy loss process of proton because of the unceasing collision with electrons and nucleus. The loss energy would heat the phase-change materials and cause the temperature rise of PRAM cell. Studying the irradiation hardness of PRAM is just studying the PRAM cell`s temperature rise causing by proton energy loss.Monte Carlo method is used to track proton trajectory in PRAM cell. Record all location of the proton collision and energy loss. Solving electric and heat conduction equation by the finite element method, simulating the phase change process by classical nucleation/growth theory, simulation system of anti-radiation performance on PRAM cell is worked out in MATLAB and is used to study the PRAM performance of irradiation hardness.The simulation results show:The trajectory of proton varies with the initial energy in PRAM cell, the trajectory of proton with low energy is more zigzag when compared with proton with high energy due to strong elastic collision in low energy, it would be more straight to those that have a higher initial energy; the stopping power is not purely increases as the initial energy of the proton increases, but as the initial energy of the proton increases along with the increase after the first decrease, and the stopping power is greatest in the initial proton energy 2 MeV; the proton with initial energy of 85 Ke V can arrive the GST, and the proton with initial energy of 500 KeV can penetrate the PRAM cell; the single event has no effect on static PRAM cell but has a little effect on dynamic PRAM cell, during the operation pulse, the incident time is earlier,the influence of proton is bigger on the resistance of PRAM cell, but all the influence is less than 3.7%, the incident proton accelerates the operation of PRAM cell; under the effect of total dose irradiation, When the dose less than 12 Mrad(SiO2),there are no changes in PRAM cell, and when the dose less than 18 Mrad(SiO2),PRAM can save the data properly,but with the dose more than 18 Mrad(SiO2),the resistance of PRAM cell begins to change, PRAM can not save data properly; the electrode of PRAM cell reinforce the performance of radiation hardness, under the environment of low energy, the stopping power of copper electrode is stronger than others, but in high energy environment, the stopping of platinum electrode is stronger. Results demonstrate that PRAM has excellent ability of radiation hardness to proton.