Sandisk Technologies Inc.

Juan Pablo Saenz

Christopher John Petti

Tanmay Kumar

Ming-Che Wu

Deepak Kamalanathan

Bijesh Rajamohanan

Ashot Melik-Martirosian

Guangle Zhou

Michael Grobis

Dimitri Houssameddine

Abhijit Bandyopadhyay

Perumal Ratnam

Srikanth Ranganathan

Michael Nicolas Albert Tran

Mohsen Purahmad

James W Reiner

Alvaro Padilla

Sebastian J M Wicklein

Gerrit Jan Hemink

Deniz Bozdag

Mark Lin

Emmanuelle Merced-Grafals

An apparatus is provided that includes a memory cell having a reversible resistance-switching memory element coupled in series with a selector element. The selector element has a first resistance. The resistance-switching memory element is configured to reversibly switch between a second resistance and a third resistance. The memory cell may be selectively configured as either a re-writeable memory cell or a one-time programmable memory cell. The memory cell functions as a one-time programmable memory cell regardless of whether the resistance-switching memory element has the second resistance, the third resistance, or is electrically shorted.

One-time programmable memory devices and methods

In a memory array with a cross-point structure, at each cross-point junction a programmable resistive memory element, such as an MRAM memory cell, is connected in series with a threshold switching selector, such as an ovonic threshold switch. The threshold switching selector switches to a conducting state when a voltage above a threshold voltage is applied. When powered down for extended periods, the threshold voltage can drift upward. If the drift is excessive, this can make the memory cell difficult to access and can disturb stored data values when accessed. Techniques are presented to determine whether excessive voltage threshold drift may have occurred, including a read based test and a time based test. Techniques are also presented for initializing a cross-point array, for both first fire and cold start, by using voltage levels shifted from half-select voltage levels used in a standard memory access.

First fire and cold start in memories with threshold switching selectors

A memory device is provided that includes a memory controller coupled to a memory array. The memory controller is adapted to perform a closed loop training interval and perform an open loop programming interval. The closed loop training interval determines a corresponding first state successful voltage and a corresponding second state successful voltage for a first group of memory cells each including a barrier modulated switching structure. The open loop programming interval programs a second group of memory cells each including a barrier modulated switching structure to a first state and a second state using the corresponding first state successful voltage and the corresponding second state successful voltage, respectively.

Methods and apparatus for programming barrier modulated memory cells

After programming a set of resistive memory cells in a resistive memory device, the programmed states and the functionality of each resistive memory cell in the programmed set can be verified by a primary determination method and a secondary determination method. The primary determination method employs the step of determining whether a measured electrical current at a preset read voltage for the selected resistive memory cell is within electrical current specification for the selected resistive state. If the selected cell fails the primary determination method, the second determination method is performed, which includes determining whether a measured threshold voltage for the selected resistive memory cell is within threshold voltage specification for the selected resistive state. If the selected cell fails both methods, the selected cell is identified as a non-functional resistive memory cell. Otherwise, the selected cell is identified as an operational cell.

Write verification and resistive state determination based on cell turn-on characteristics for resistive random access memory

Technology is described for identifying non-volatile memory cells having data that should be refreshed. The technology could be used to identify which groups of memory cells that store cold data should have a data refresh. In one aspect, a non-volatile storage device has at least one monitor memory cell associated with a group of data memory cells. The non-volatile storage device may use different programming techniques to program the data and monitor memory cells. In one aspect, the programming technique used for the monitor memory cell is less stable with respect to state than the technique used to program the associated data memory cells. The state of the monitor memory cell may change in a predictable manner, such that the state of the monitor cell may be sensed periodically to determine whether the associated data memory cells should be refreshed.

Apparatus and method for identifying memory cells for data refresh based on monitor cell in a resistive memory device

A method is provided that includes forming a word line above a substrate, the word line disposed in a first direction, forming a bit line above the substrate, the bit line disposed in a second direction perpendicular to the first direction, forming a nonvolatile memory material between the word line and the bit line, the nonvolatile memory material including a semiconductor material layer and conductive oxide material layer, forming a first barrier material layer between the word line and the nonvolatile memory material, forming a second barrier material layer between the bit line and the nonvolatile memory material, and forming a memory cell including the nonvolatile memory material at an intersection of the bit line and the word line.

Methods and apparatus for three-dimensional nonvolatile memory

A method is provided that includes forming a word line above a substrate, the word line disposed in a first direction, forming a bit line above the substrate, the bit line disposed in a second direction perpendicular to the first direction, forming a nonvolatile memory material between the word line and the bit line, and forming a memory cell including the nonvolatile memory material at an intersection of the bit line and the word line. The word line includes a first portion and a second portion including an electrically conductive carbon-containing material. The nonvolatile memory material includes a semiconductor material layer and a conductive oxide material layer, with the semiconductor material layer disposed adjacent the second portion of the word line.

A method of operating a resistive memory device includes providing a resistive memory device including an array of resistive memory cells, where each of the resistive memory cells includes a resistive memory material having at least two different resistive states, performing a first mode read operation on a group of resistive memory cells within the array, determining a bit error rate for data generated by the first mode read operation, determining whether the determined bit error rate is below a predetermined limit, and performing a second mode read operation on the group of resistive memory cells within the array based on a threshold voltage if the determined bit error rate is above the predetermined limit.

ReRAM read state verification based on cell turn-on characteristics

Systems and methods for providing a Barrier Modulated Cell (BMC) structure with reduced shifting in stored memory cell resistance levels over time are described. The BMC structure may comprise a reversible resistance-switching memory element within a memory array comprising a first conductive metal oxide (e.g., titanium oxide) in series with an alternating stack of one or more layers of an amorphous low bandgap material (e.g., germanium) with one or more layers of a second conductive metal oxide (e.g., aluminum oxide). The BMC structure may include a barrier layer comprising a first conductive metal oxide, such as titanium oxide or strontium titanate, in series with a germanium stack that includes a layer of amorphous germanium or amorphous silicon germanium paired with a second conductive metal oxide. The second conductive metal oxide (e.g., aluminum oxide) may be different from the first conductive metal oxide (e.g., titanium oxide).

Germanium-based barrier modulated cell

A method is provided that includes forming a word line above a substrate, forming a bit line above the substrate, forming a nonvolatile memory material between the word line and the bit line, the nonvolatile memory material including a semiconductor material layer and a conductive oxide material layer, forming a barrier material layer between the semiconductor material layer and the conductive oxide material layer, and forming a memory cell including the nonvolatile memory material at an intersection of the bit line and the word line. The word line is disposed in a first direction, the bit line is disposed in a second direction perpendicular to the first direction. The barrier material layer has an ionic conductivity of greater than about 0.1 Siemens/cm @ 1000&#xb0; C.

A matrix rail structure is formed over a substrate. The matrix rail structure includes a pair of lengthwise sidewalls that extend along a first horizontal direction and comprises, or is at least partially subsequently replaced with, a set of at least one gate electrode rail extending along the first horizontal direction and straight-sidewalled gate dielectrics. A pair of vertical semiconductor channel strips and a pair of laterally-undulating gate dielectrics can be formed on sidewalls of the matrix rail structure for each vertical field effect transistor. At least one laterally-undulating gate electrode extending along the first horizontal direction is formed on the laterally-undulating gate dielectrics. Bottom active regions and top active regions are formed at end portions of the vertical semiconductor channel strips. The vertical field effect transistors can be formed as a two-dimensional array, and may be employed as access transistors for a three-dimensional memory device.

Multi-gate vertical field effect transistor with channel strips laterally confined by gate dielectric layers, and method of making thereof

A method is provided that includes providing a memory device including a first word line, a vertical bit line, a non-volatile memory material disposed between the first word line and the vertical bit line, and a memory cell disposed between the first word line and the vertical bit line. The first word line has a first height. The method further includes forming one or more conductive filaments in the memory cell. The one or more conductive filaments are substantially confined to a filament region having a second height less than the first height and disposed substantially about a vertical center of the memory cell.

Filament confinement in reversible resistance-switching memory elements

A memory cell is provided that includes a vertically-oriented adjustable resistance material layer, a control terminal disposed adjacent the vertically-oriented adjustable resistance material layer and coupled to a word line, and a reversible resistance-switching element disposed on the vertically-oriented adjustable resistance material layer. The control terminal is configured to adjust a resistance of the vertically-oriented adjustable resistance material layer.

Memory cells including vertically oriented adjustable resistance structures

A method is provided that includes forming a vertical bit line disposed in a first direction above a substrate, forming a multi-layer word line disposed in a second direction above the substrate, the second direction perpendicular to the first direction, and forming a memory cell including a nonvolatile memory material at an intersection of the vertical bit line and the multi-layer word line. The multi-layer word line includes a first conductive material layer and a second conductive material layer disposed above the first conductive material layer. The memory cell includes a working cell area encompassed by an intersection of the first conductive material layer and the nonvolatile memory material.

Controlling memory cell size in three dimensional nonvolatile memory

A memory cell is provided that includes a vertically-oriented adjustable resistance structure including a control terminal coupled to a word line, and a reversible resistance-switching element coupled in series with and disposed above or below the vertically-oriented adjustable resistance structure.

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Menlo Park, CA, United States of America

Juan Pablo Saenz