A 0.18 μm 4Mb toggling MRAM

Device implications of spin-transfer torques

“…In addition, large semiconductor companies such as IBM, Freescale, Sony, and Hitachi have efforts in this area. To understand the appeal of ST-MRAM, it is useful to look at the toggle MRAM technology that recently has been commercialized by Freescale [24]. In the earliest forms of MRAM the bit state is programmed to a ''1'' or ''0'' by aligning the magnetization of the free layer either antiparallel or parallel to the top magnetic layer of the reference.…”

Interlayer exchange coupling dependence of thermal stability parameters in synthetic antiferromagnetic free layers

“…We have proposed an element structure for reducing the switching field and for permitting a low L/W in nanometerscale devices with synthetic antiferromagnetic (Syn-AF) free layers [5] pulse sequence enable the use of Syn-AF free layers [5][6][7] in Toggle MRAMs [8], which allows adequate write switching and disturb margins for reliable write operation in MRAMs. Moreover, an MRAM structure using currentinduced switching and local field assistance was demonstrated [9] by using the Syn-AF free layers, and this shows the potential application for universal memory of MRAMs.…”

Switching and reliability issues of magnetic tunnel junctions for high-density memory device

“…Conventional MRAM combines a magnetoresistive MTJ with a single-pass transistor for bit selection for a read operation and, for a write operation, an array of magnetic memory cells is located at the intersection of two perpendicular write lines, as shown in Fig. 1 [6]. To read a single bit, the transistor is turned on, bias voltage is applied to the bit, and the memory state is determined by measuring the amount of current that flows through the MTJ.…”

“…Because of the problems in the conventional write scheme, a number of new writing methods, such as toggle switching [6], thermal-assisted switching [9,10], spin-transfer torque switching [11,12], and local-field switching [13], have been proposed. In Section 2, the principles and possible capabilities of the new writing schemes will be presented and discussed.…”