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  Magnetic random access memory, magnetic random access memory manufacturing method, and magnetic random access memory write methodUSPTO Application #: 20070224707Title: Magnetic random access memory, magnetic random access memory manufacturing method, and magnetic random access memory write method Abstract: A magnetic random access memory includes first and second write wirings, the second write wiring having first and second crossing angles formed by crossing the first write wiring, a first magnetoresistive element having a first axis of easy magnetization directed to a side of the first crossing angle and having a first recording layer including first and second ferromagnetic layers and a first nonmagnetic layer, and a second magnetoresistive element being electrically connected to the first magnetoresistive element, having a second axis of easy magnetization directed to a side of the second crossing angle, and having a second recording layer including third and fourth ferromagnetic layers and a second nonmagnetic layer, wherein in a write operation, magnetizations in the first and second recording layers execute a toggle operation by using the first and second write wirings. (end of abstract) Agent: Oblon, Spivak, Mcclelland, Maier & Neustadt, P.C. - Alexandria, VA, US Inventor: Keiji Hosotani USPTO Applicaton #: 20070224707 - Class: 438003000 (USPTO) Related Patent Categories: Semiconductor Device Manufacturing: Process, Having Magnetic Or Ferroelectric Component The Patent Description & Claims data below is from USPTO Patent Application 20070224707. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a Division of and claims the benefit of priority under 35 USC .sctn.120 from U.S. Ser. No. 11/200,105, filed Aug. 10, 2005, and claims the benefit of priority under 35 U.S.C. .sctn.119 from Japanese patent Application No. 2005-100972, filed Mar. 31, 2005, the entire contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a magnetic random access memory (MRAM) using a magnetoresistive effect, magnetic random access memory manufacturing method, and magnetic random access memory write method. [0004] 2. Description of the Related Art [0005] Magnetic random access memories (MRAMs) using a tunneling magnetoresistive (TMR) effect have been proposed recently as information storage elements (e.g., Roy Scheuerlein et al., "A 10 ns Read and Write Non-Volatile Memory Array Using a Magnetic Tunnel Junction and FET Switch in each Cell", ISSCC 2000 Technical Digest, p. 128). [0006] A memory cell of a magnetic random access memory comprises an upper write wiring, lower write wiring, and magnetic tunnel junction (MTJ) element provided between the upper and lower write wirings. The MTJ element has a fixed layer, recording layer, and tunnel barrier layer sandwiched between the fixed layer and the recording layer. [0007] In a so-called toggle cell, the direction of axis of easy magnetization of the MTJ element tilts 45.degree. with respect to the running direction of the upper or lower write wiring. The recording layer of the MTJ element has a three-layer structure of ferromagnetic layer/nonmagnetic layer/ferromagnetic layer. The two ferromagnetic layers are anti-ferromagnetically coupled through the nonmagnetic layer. [0008] In a write operation of such a toggle cell, first, current is sequentially supplied to the upper and lower write wirings. Then, supply of the currents is stopped in the same order as that of its start. With this process, magnetization reversal occurs regardless of the initial magnetization state. Hence, before the write, data of the MTJ element is read out to determine the current cell state. After that, the write operation is started as needed. [0009] The resistance state of the MTJ element changes between "1" and "0" depending on whether the magnetization direction of the fixed layer and that of the ferromagnetic layer of the recording layer located on the fixed layer side is parallel or anti-parallel. The read operation can be executed by extracting the resistance state. [0010] The toggle cell is hardly affected by a variation in magnetization reversal threshold value of each MTJ element in principle and can advantageously be used for increasing the scale of magnetic random access memories. However, it is not yet the standard technique of magnetic random access memories because of problems such as the large write current and low write speed. BRIEF SUMMARY OF THE INVENTION [0011] According to a first aspect of the present invention, there is provided a magnetic random access memory comprising a first write wiring which runs in a first direction, a second write wiring which runs in a second direction different from the first direction and has a first crossing angle and second crossing angle formed by crossing the first write wiring, the first crossing angle and second crossing angle being located on both sides of the first write wiring serving as a boundary, a first magnetoresistive element which is arranged at an intersection of the first write wiring and the second write wiring between the first write wiring and the second write wiring, has a first axis of easy magnetization directed to a side of the first crossing angle, and has a first fixed layer, a first recording layer, and a first tunnel barrier layer sandwiched between the first fixed layer and the first recording layer, the first recording layer including a first ferromagnetic layer located on a side of the first fixed layer, a second ferromagnetic layer, and a first nonmagnetic layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, and a second magnetoresistive element which is arranged at the intersection of the first write wiring and the second write wiring between the first write wiring and the second write wiring and electrically connected to the first magnetoresistive element, has a second axis of easy magnetization directed to a side of the second crossing angle, and has a second fixed layer, a second recording layer, and a second tunnel barrier layer sandwiched between the second fixed layer and the second recording layer, the second recording layer including a third ferromagnetic layer located on a side of the second fixed layer, a fourth ferromagnetic layer, and a second nonmagnetic layer sandwiched between the third ferromagnetic layer and the fourth ferromagnetic layer, wherein in a write operation, magnetizations in the first recording layer and second recording layer execute a toggle operation by using the first write wiring and second write wiring. [0012] According to a second aspect of the present invention, there is provided a magnetic random access memory comprising a first write wiring which runs in a first direction, a second write wiring which runs in a second direction different from the first direction and has a first crossing angle and second crossing angle formed by crossing the first write wiring, the first crossing angle and second crossing angle being located on both sides of the first write wiring serving as a boundary, a first magnetoresistive element which is arranged at an intersection of the first write wiring and the second write wiring between the first write wiring and the second write wiring, has a first axis of easy magnetization directed to a side of the first crossing angle, and has a first fixed layer, a first recording layer, and a first tunnel barrier layer sandwiched between the first fixed layer and the first recording layer, the first recording layer including a first ferromagnetic layer located on a side of the first fixed layer, a second ferromagnetic layer, and a first nonmagnetic layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, and a second magnetoresistive element which is arranged at the intersection of the first write wiring and the second write wiring between the first write wiring and the second write wiring and electrically connected to the first magnetoresistive element, has a second axis of easy magnetization directed to a side of the second crossing angle, and has a second fixed layer, a second recording layer, and a second tunnel barrier layer sandwiched between the second fixed layer and the second recording layer. [0013] According to a third aspect of the present invention, there is provided a write method of a magnetic random access memory which includes a first write wiring which runs in a first direction, a second write wiring which runs in a second direction different from the first direction and has a first crossing angle and second crossing angle formed by crossing the first write wiring, the first crossing angle and second crossing angle being located on both sides of the first write wiring serving as a boundary, a first magnetoresistive element which is arranged at an intersection of the first write wiring and the second write wiring between the first write wiring and the second write wiring, has a first axis of easy magnetization directed to a side of the first crossing angle, and has a first fixed layer, a first recording layer, and a first tunnel barrier layer sandwiched between the first fixed layer and the first recording layer, the first recording layer including a first ferromagnetic layer located on a side of the first fixed layer, a second ferromagnetic layer, and a first nonmagnetic layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, and a second magnetoresistive element which is arranged at the intersection of the first write wiring and the second write wiring between the first write wiring and the second write wiring and electrically connected to the first magnetoresistive element, has a second axis of easy magnetization directed to a side of the second crossing angle, and has a second fixed layer, a second recording layer, and a second tunnel barrier layer sandwiched between the second fixed layer and the second recording layer, the second recording layer including a third ferromagnetic layer located on a side of the second fixed layer, a fourth ferromagnetic layer, and a second nonmagnetic layer sandwiched between the third ferromagnetic layer and the fourth ferromagnetic layer, the write method writing binary information in the first magnetoresistive element and second magnetoresistive element by supplying a first write current to the first write wiring and a second write current to the second write wiring, comprising starting supplying one current of one of the first write current and second write current earlier than the other current of the other of the first write current and second write current supplying the other current in addition to the one current, reducing a current value of the one current to not more than a write threshold value earlier than the other current, and reducing a current value of the other current to not more than the write threshold value, wherein an order of starting or ending supply of the first write current and second write current and directions in which the first write current and second write current are supplied are changed to selectively cause one of the first magnetoresistive element and second magnetoresistive element to execute a toggle operation. [0014] According to a fourth aspect of the present invention, there is provided a write method of a magnetic random access memory which includes a first write wiring which runs in a first direction, a second write wiring which runs in a second direction different from the first direction and has a first crossing angle and second crossing angle formed by crossing the first write wiring, the first crossing angle and second crossing angle being located on both sides of the first write wiring serving as a boundary, a first magnetoresistive element which is arranged at an intersection of the first write wiring and the second write wiring between the first write wiring and the second write wiring, has a first axis of easy magnetization directed to a side of the first crossing angle, and has a first fixed layer, a first recording layer, and a first tunnel barrier layer sandwiched between the first fixed layer and the first recording layer, the first recording layer including a first ferromagnetic layer located on a side of the first fixed layer, a second ferromagnetic layer, and a first nonmagnetic layer sandwiched between the first ferromagnetic layer and the second ferromagnetic layer, and a second magnetoresistive element which is arranged at the intersection of the first write wiring and the second write wiring between the first write wiring and the second write wiring and electrically connected to the first magnetoresistive element, has a second axis of easy magnetization directed to a side of the second crossing angle, and has a second fixed layer, a second recording layer, and a second tunnel barrier layer sandwiched between the second fixed layer and the second recording layer, the write method writing binary information in the first magnetoresistive element and second magnetoresistive element by supplying a first write current to the first write wiring and a second write current to the second write wiring, comprising starting supplying one current of one of the first write current and second write current earlier than the other current of the other of the first write current and second write current, supplying the other current in addition to the one current, reducing a current value of the one current to not more than a write threshold value earlier than the other current, and reducing a current value of the other current to not more than the write threshold value, wherein an order of starting or ending supply of the first write current and second write current and directions in which the first write current and second write current are supplied are changed to selectively independently execute a first operation and second operation, the first operation is causing or not causing the first magnetoresistive element to execute a toggle operation, and the second operation is reversing magnetization in the second recording layer of the second magnetoresistive element. [0015] According to a fifth aspect of the present invention, there is provided a magnetic random access memory manufacturing method comprising forming a first write wiring, forming a first electrode above the first write wiring, forming a first material layer on the first electrode, processing the first material layer to form a first magnetoresistive element having a first axis of easy magnetization directed in a first direction, forming a interlayer around the first magnetoresistive element, forming a second electrode on the first magnetoresistive element, forming a second material layer on the second electrode, processing the second material layer to form a second magnetoresistive element having a second axis of easy magnetization directed in a second direction different from the first direction, and forming a second write wiring above the second magnetoresistive element. [0016] According to a sixth aspect of the present invention, there is provided a magnetic random access memory manufacturing method comprising forming a first write wiring, forming a first electrode above the first write wiring, forming a first material layer, a contact layer, and a second material layer sequentially on the first electrode, processing the first material layer, the contact layer, and the second material layer at once to form a first magnetoresistive element, a contact, and a second magnetoresistive element, and forming a second write wiring above the second magnetoresistive element. [0017] According to a seventh aspect of the present invention, there is provided a magnetic random access memory manufacturing method comprising forming a first write wiring and a first magnetoresistive element above a first substrate, forming a contact connected to the first magnetoresistive element, forming a second write wiring and a second magnetoresistive element above a second substrate different from the first substrate, and bonding the first substrate and second substrate to electrically connect the first magnetoresistive element and second magnetoresistive element through the contact. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING [0018] FIG. 1A is a plan view showing a magnetic random access memory according to the first embodiment of the present invention; [0019] FIG. 1B is a sectional view of the magnetic random access memory taken along a line IB-IB in FIG. 1A; [0020] FIG. 2 is an explanatory view of the cycles of Write Method Example 1 of the first MTJ element according to the first embodiment of the present invention; Continue reading... Full patent description for Magnetic random access memory, magnetic random access memory manufacturing method, and magnetic random access memory write method Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Magnetic random access memory, magnetic random access memory manufacturing method, and magnetic random access memory write method patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. 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