Hewlett-packard Development Company, L.P.

Hewlett-packard Company

Samsung Electronics Co., Ltd.

James Robert Eaton

Frederick A Perner

Lung T Tran

Joseph Ku

Kenneth Kay Smith

Ping Mei

Kenneth James Eldredge

Michael C Fischer

Ken Eldredge

Andrew L Van Brocklin

Philip John Kuekes

Peter James Fricke

Laurence G Walker

Charles G Sodini

A method for making magnetic random access memories (MRAM) isolates each and every memory cell in an MRAM array during operation until selected. Some embodiments use series connected diodes for such electrical isolation. Only a selected one of the memory cells will then conduct current between respective ones of the bit and word lines. A better, more uniform distribution of read and data-write data access currents results to all the memory cells. In another embodiment, this improvement is used to increase the number of rows and columns to support a larger data array. In a further embodiment, such improvement is used to increase operating margins and reduce necessary data-write voltages and currents.

Increased magnetic memory array sizes and operating margins

The invention includes an apparatus and method of selecting memory cells within a memory array. The method includes receiving a memory cell address. A column address and a row address are generated from the memory cell address. Row select lines or column select lines are pre-charged. A self-timed charging circuit is initiated to provide an adequate amount of time to charge a selected row, and to initiate elimination of static current flowing to unselected rows after a self-timed delay. The other of the row select lines or the column select lines are then pre-charged. Memory cells are selected based upon the column address and the row address. One of two states of the memory cells can be based upon sensing threshold voltages of sense lines that correspond with the selected memory cells.

Self-timed memory device providing adequate charging time for selected heaviest loading row

A memory device includes a memory array of thin film transistor (TFT) memory cells. The memory cells include a floating gate separated from a gate electrode portion of a gate line by an insulator. The gate electrode portion includes a diffusive conductor that diffuses through the insulator under the application of a write voltage. The diffusive conductor forms a conductive path through the insulator that couples the gate line to the floating gate, changing the gate capacitance and therefore the state of the memory cell. The states of the memory cells are detectable as the differing current values for the memory cells. The memory cells are three terminal devices, and read currents do not pass through the conductive paths in the memory cells during read operations. This renders the memory cells robust, because read currents will not interfere with the storage mechanism in the memory cells. The memory array can be fabricated using multiple steps using the same mask. The use of a single mask for multiple steps reduces the time and cost involved in fabricating the memory array.

Thin film transistor memory device

Method for precharging word and bit lines for selecting memory cells within a memory array

A magnetic random access memory (MRAM) includes an array of magnetic memory cells arranged on a cross-point grid. Spurious voltages that build up on the stray wiring capacitance of unselected bit and word select lines are limited and discharged by diodes. The control of such spurious voltages improves device operating margins and allows the construction of larger arrays.

Magnetic memory device

A four-conductor MRAM device comprising an array of memory cells, each of the memory cells including a first magnetic layer, a dielectric, and a second magnetic layer; a plurality of local column sense lines wherein one is electrically connected to the first magnetic layer of the array of memory cells; a plurality of local row sense lines wherein one of the local row sense lines is electrically connected to the second magnetic layer of the array of memory cells; a plurality of global column write lines parallel to the plurality of local column sense lines; a plurality of global row write lines parallel to the plurality of local row sense lines; and wherein the plurality of local column sense lines and the plurality of local row sense lines are connected to read data from the array of memory cells and the plurality of global column write lines and the plurality of global row write lines are connected to write data to the array of memory cells.

System for and method of four-conductor magnetic random access memory cell and decoding scheme

A control circuit for writing to and reading from MRAMs comprising a row decoder; a first read/write row driver connected to the row decoder; a plurality of global row write conductors connected to the first read/write row driver; a plurality of row taps connected to each of the global row write conductors; and a second read/write row driver connected to the global row write conductors.

System for and method of accessing a four-conductor magnetic random access memory

The invention includes a logic gate. The logic gate includes a charge holding device. A charging circuit selectively provides a predetermined charge for the charge holding device. A logic gate output is a function of charge on the charge holding device. The logic gate further includes a plurality of inputs. The plurality of inputs are electrically connected to the charge holding device so that the charge of the charge holding device is modified if any of the plurality of inputs is a first voltage potential. The invention also includes an address decoder. The address decoder includes a charge holding device. A charging circuit selectively provides a predetermined charge for the charge holding device. An address decoder output is a function of charge on the charge holding device. The address decoder further includes a plurality of address lines. The plurality of address lines are electrically connected to the charge holding device so that the charge of the charge holding device is modified if any of the plurality of address lines is a first voltage potential.

Low power logic gate

An electrically addressable data storage unit has a matrix of rows and columns of data storage arrays on a single substrate. Each array is a matrix of coplanar data storage diode cells connected by row lines and column lines for recording, addressing and reading of data. Address lines and power lines of each array are connected to the array so that only the data storage diode cells of a selected data storage cell are enabled, thereby eliminating undesirable power dissipation in all other arrays of the array. A controller enables the row and column address lines to selectively address a diode cell in a selected array.

Address structure and methods for multiple arrays of data storage memory

A nano-scale flash memory comprises: (a) source and drain regions in a plurality of approximately parallel first wires, the first wires comprising a semiconductor material, the source and drain regions separated by a channel region; (b) gate electrodes in a plurality of approximately parallel second wires, the second wires comprising either a semiconductor material or a metal, the second wires crossing the first wires at a non-zero angle over the channel regions, to form an array of nanoscale transistors; and (c) a hot electron trap region at each intersection of the first wires with the second wires. Additionally, crossed-wire transistors are provided that can either form a configurable transistor or a switch memory bit that is capable of being set by application of a voltage. The crossed-wire transistors can be formed in a crossbar array.

Molecular wire crossbar flash memory

A method of and apparatus for connecting the sense current line in a cross-point memory array greatly reduces the effect of reverse leakage from unaddressed row or column lines. Separate sense line segments are coupled to separate stripes of row or column lines. Each sense line segment is connected to a sense diode, and each sense diode is connected to a sense bus. Each sense diode provides the current path for sensing on a selected row or column line, while allowing the leakage of only one diode per sense line segment for the unaddressed row or column lines. This arrangement results in wider margins for sensing the state of data cells in a cross-point memory array and simpler circuitry design for the memory array.

Diode decoupled sensing method and apparatus

A sense amplifier is provided for reading data in a multiple-state memory cell of a resistive memory array in response to a read voltage applied across the sensed memory cell, including a differential amplifier having first and second input nodes. A sense circuit determines the current in the memory cell with the read voltage applied thereto and applies a sense current representative of the memory cell current to the first input node of the differential amplifier. A reference circuit has first and second resistive elements for applying a reference current to the second input node of the differential amplifier to provide a reference value against which to compare the sense current to determine the state of the memory cell. The first resistive element has a resistance representative of a first state of the memory cell, and the second resistive element has a resistance representative of a second state of the memory cell. A voltage source for applying the read voltage across the first and second resistive elements to generate a reference current by averaging the currents through the first and second resistive elements. A first translator transistor applies the sense current to the first node of the differential amplifier. A second translator transistor applies the reference current to the second node of the differential amplifier. A comparator circuit is used to compare the signals at the first and second input nodes of the differential amplifier to provide an output indicative of the state of the sensed memory cell.

High density memory sense amplifier

Each memory cell of an x-y addressable semiconductor memory includes a charge storage element serially connected with an I-O (bit) line through a pair of CCD-type transfer gates. One gate is responsive to x-addressing and the other gate to y-addressing. When an x-y address is selected only the charge storage element of the one selected memory cell communicates with the bit line.

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Palo Alto, CA, United States of America

James Robert Eaton