Papers by Keyword: MRAM

Abstract: A Magnetic Random Access Memory (MRAM) device was successfully embedded into TowerJazz’s 130nm CMOS platform. The fabricated devices are stand-alone 4Mbit and 1Mbit MRAM memories and Multi-MLU magnetic sensors. This paper will describe the process development challenges in adapting a standard 130nm Cu BEOL to incorporate the magnetic cell element, and the device sensitivities to processing.The main process challenges to be discussed are 1) formation of shallow damascene Cu contacts to the lower electrode; 2) patterning of the 150nm magnetic cell both lithography and etching of the magnetic stack; 3) planarization of the topography from the magnetic cell; 4) formation of dual damascene VIA’s to both the magnetic cell upper electrode and to the CMOS. Some electrical yield results of the stand-alone MRAM memory and magnetic sensors will be presented. This project was a collaborative effort between TowerJazz and Crocus Technology

Abstract: We have developed a numerical model for investigating a motion of magnetic moments in ferromagnetic materials with spin transfer torque (STT). The model can be used to provide a basic understanding of the switching dynamics and can be used as a tool to design and develop magnetic random access memories (MRAM). The relevant equation used in this work was the Landau-Lifshitz-Gilbert (LLG) equation with the additional STT term. The equation was used to describe the dynamical behavior of a magnetization which is exposed to an applied spin current and an effective field. The effects of thermal fluctuations on the motion of magnetic moments were excluded. The model was implemented in MATLABTM using a finite difference method (FDM). The program was verified with two-spin system and standard problems. Simulation results were also compared with those obtained from OOMMF.

Abstract: This work reports on advances in MRAM cells aiming at sub-nanosecond switching and for sub-20nm technology nodes. Ultrafast precessional spin-transfer switching in elliptical magnetic tunnel junction nanopillars is possible to obtain in samples integrating a perpendicular polarizer and a tunnel junction with in-plane magnetized electrodes. We show that spin transfer torque (STT) switching in less than 500ps can be achieved in these structures with corresponding write energy less than 100fJ. For high density integration and possibly sub-20nm diameter cells the use of a thermally assisted concept for perpendicular anisotropy cells, where the intrinsic heating is used to simultaneously achieve high thermal stability and low current switching.

Abstract: The term "Multiferroic" is coined for a material possessing at least two ferroic orders in the same or composite phase (ferromagnetic, ferroelectric, ferroelastic); if the first two ferroic orders are linearly coupled together it is known as a magnetoelectric (ME) multiferroic. Two kinds of ME multiferroic memory devices are under extensive research based on the philosophy of "switching of polarization by magnetic fields and magnetization by electric fields." Successful switching of ferroic orders will provide an extra degree of freedom to create more logic states. The "switching of polarization by magnetic fields" is useful for magnetic field sensors and for memory elements if, for example, polarization switching is via a very small magnetic field from a coil underneath an integrated circuit. The electric control of magnetization is suitable for nondestructive low-power, high-density magnetically read and electrically written memory elements. If the system possesses additional features, such as propagating magnon (spin wave) excitations at room temperature, additional functional applications may be possible. Magnon-based logic (magnonic) systems have been initiated by various scientists, and prototype devices show potential for future complementary metal oxide semiconductor (CMOS) technology. Discovery of high polarization, magnetization, piezoelectric, spin waves (magnon), magneto-electric, photovoltaic, exchange bias coupling, etc. make bismuth ferrite, BiFeO₃, one of the widely investigated materials in this decade. Basic multiferroic features of well known room temperature single phase BiFeO₃ in bulk and thin films have been discussed. Functional magnetoelectric (ME) properties of some lead-based solid solution perovskite multiferroics are presented and these systems also have a bright future. The prospects and the limitations of the ME-based random access memory (MERAM) are explained in the context of recent discoveries and state of the art research.

Abstract: In this study is the use of the generator excitation system design parameters for distributed fieldbus technology and real-time data display module record, will transfer to the field bus data processing and real-time storage of a design. Generator current and terminal voltage and other electrical parameters by the CAN bus pass, when a failure occurs, the fault current and other electrical parameters display, and store it to MRAM or FRAM memory, and also through the external communications port to be transferred to PC and other networks. System uses magnetic resistance random access memory, ferroelectric memory extends the storage capacity, so that fault recording function can be achieved; application PIT and RTC, the timing accuracy of a millisecond, improve the recording wave function

Abstract: To commute between the different resistance states of a magnetic tunnel junction (TJ) one can use a thermally-induced pinned layer switching mechanism. When a sufficiently high electrical current flows through the insulating barrier, local temperatures inside the tunnel junction can increase above the blocking temperature of the antiferromagnetic layer used to pin the magnetization of the adjacent ferromagnet. Then, it is possible to switch the magnetization of the pinned layer with a small magnetic field H and thus revert the magnetic state of the TJ. Here we demonstrate thermally-induced pinned layer switching in thin magnetic tunnel junctions. We further present numerical results that suggest that heating is small when one takes into consideration the uniform current density flowing through the tunnel junction and that one must conclude that nanoconstrictions concentrate most of the current, increasing local current densities and temperature. Simulation of heating and cooling times demonstrates that current-induced pinned layer switching is a competitive mechanism for actual technological applications.