Static information storage and retrieval – Systems using particular element – Magnetic thin film
Reexamination Certificate
2001-03-27
2003-02-18
Ho, Hoai (Department: 2818)
Static information storage and retrieval
Systems using particular element
Magnetic thin film
C365S063000, C365S158000, C257S108000
Reexamination Certificate
active
06522579
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to the fabrication of semiconductor devices, and more particularly to magnetic random access memory (MRAM) devices.
BACKGROUND OF THE INVENTION
Semiconductors are used for integrated circuits for electronic applications, including radios, televisions, cell phones, and personal computing devices, as examples. One type of semiconductor device is a semiconductor storage device, such as a dynamic random access memory (DRAM) and flash memory, which use an electron charge to store information.
A more recent development in memory devices involves spin electronics, which combines semiconductor technology and magnetics. The spin of an electron, rather than the charge, is used to indicate the presence of a “1” or “0”. One such spin electronic device is a magnetic random-access memory (MRAM), which includes conductive lines positioned perpendicular to one another in different metal layers, the conductive lines sandwiching a magnetic stack. The place where the conductive lines intersect is called a cross-point. A current flowing through one of the conductive lines generates a magnetic field around the conductive line and orients the magnetic polarity into a certain direction along the wire or conductive line. A current flowing through the other conductive line induces the magnetic field and can partially turn the magnetic polarity, also. Digital information, represented as a “0” or “1”, is storable in the alignment of magnetic moments. The resistance of the magnetic component depends on the moment's alignment. The stored state is read from the element by detecting the component's resistive state. A memory cell may be constructed by placing the conductive lines and crosspoints in a matrix structure having rows and columns.
An advantage of MRAMs compared to traditional semiconductor memory devices such as DRAMs is that MRAMs are non-volatile. For example, a personal computer (PC) utilizing MRAMs would not have a long “boot-up” time as with conventional PCs that utilize DRAMs. Also, an MRAM does not need to be powered up and has the capability of “remembering” the stored data.
A disadvantage of current MRAM designs is that a large amount of current is required to switch the cells, e.g. the amount of current that must be passed through the bitlines and wordlines is high. Therefore, a large amount of power is used.
What is needed in the art is an MRAM design that requires less current and power to switch the resistive state or logic state of the memory cells.
SUMMARY OF THE INVENTION
The present invention achieves technical advantages as a non-orthogonal MRAM device requiring less current and power than prior art MRAMs to change the logic state of the memory cells. Bitlines and wordlines are formed non-orthogonal to one another, that is, at an angle other than 90 degrees, preferably ranging from slightly more than 0 to less than 90 degrees.
Disclosed is a semiconductor memory device comprising at least one first conductive line, at least one memory storage cell disposed over the first conductive line, and at least one second conductive line disposed over the first conductive line. The second conductive line is positioned non-orthogonal relative to the first conductive line, and the memory storage cell has material properties based on an asteroid-shaped curve.
Also disclosed is an MRAM device, comprising a plurality of first conductive lines, a plurality of second conductive lines disposed over the first conductive lines and positioned at an angle other than 90 degrees with respect to the first conductive lines, and a plurality of memory storage cells disposed between and adjacent to the first and second conductive lines.
Further disclosed is a method of manufacturing a semiconductor memory device, comprising forming at least one first conductive line, forming at least one memory storage cell disposed over the first conductive line, and forming at least one second conductive line over the memory storage cell non-orthogonal relative to the first conductive line. The memory storage cell has material properties based on an asteroid-shaped curve.
Also disclosed is a method of programming an MRAM device, comprising sending a first current through the first conductive lines, wherein the first current creates a first electromagnetic field around the first conductive lines, and sending a second current through the second conductive lines, wherein the second current creates a second electromagnetic field around the second conductive lines, wherein the second field is different than the first field.
A memory storage cell used in embodiments of the present invention may comprise a magnetic stack that includes a tunnel junction. The tunnel junction may comprise a rectangular or non-rectangular parallelogram shape, or a trapezoidal shape.
Advantages of the invention include reducing the amount of current required in a wordline and/or bitline to switch the charge stored in the memory cell. Reducing the current results in a power savings for the memory device. Damage and reduced life of memory devices, due to electromigration is also alleviated by the use of lower current on wordlines and bitlines.
REFERENCES:
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patent: 5716719 (1998-02-01), Saito et al.
patent: 5747997 (1998-05-01), Dahlberg et al.
patent: 6005800 (1999-12-01), Koch et al.
patent: 6104633 (2000-08-01), Abraham et al.
patent: 6178131 (2001-01-01), Ishikawa et al.
Ho Hoai
Infineon - Technologies AG
Slater & Matsil L.L.P.
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