DISCHARGING AN ACCESS DEVICE IN A MEMORY DEVICE

Systems, methods, and apparatus are provided for discharging an access device in a memory device. An example structure includes a memory device having a local sense line and a bleeder device coupled to the local sense line and a bleeder supply. The memory device can also include a sense line multiplexor coupled to the local sense line and a global sense line, and a sense amplifier coupled to the global sense line. The sense amplifier can be configured to sense and latch a voltage of the global sense line in response to the memory device receiving a command. The memory device can further include a plurality of access devices coupled to the local sense line, a plurality of capacitors coupled to the plurality of access devices, and a plate voltage supply, separate from the bleeder supply, coupled to the plurality of capacitors.

TECHNICAL FIELD

The present disclosure relates generally to memory devices, and more particularly, to discharging an access device in a memory device.

BACKGROUND

Memory is often implemented in electronic systems, such as computers, cell phones, hand-held devices, etc. There are many different types of memory, including volatile and non-volatile memory. Volatile memory may require power to maintain its data and may include random-access memory (RAM), dynamic random-access memory (DRAM), static random-access memory (SRAM), and synchronous dynamic random-access memory (SDRAM). Non-volatile memory may provide persistent data by retaining stored data when not powered and may include NAND flash memory, NOR flash memory, nitride read only memory (NROM), phase-change memory (e.g., phase-change random access memory), resistive memory (e.g., resistive random-access memory), cross-point memory, ferroelectric random-access memory (FeRAM), or the like.

As design rules shrink, less semiconductor space is available to fabricate memory, including DRAM arrays. A respective memory cell for DRAM may include an access device, e.g., transistor, having a first and a second source/drain regions separated by a channel region. A gate may oppose the channel region and be separated therefrom by a gate dielectric. An access line, such as a word line, is electrically connected to the gate of the DRAM cell. A DRAM cell can include a storage node, such as a capacitor cell, coupled by the access device to a shared sense line. The access device can be activated (e.g., to select the cell) by an access line coupled to the access transistor. The capacitor can store a charge corresponding to a data value of a respective cell (e.g., a logic “1” or “0”).

DETAILED DESCRIPTION

Embodiments of the present disclosure describe discharging an access device in a memory device. A memory device can include a bleeder device that can be coupled to a local sense line and a bleeder supply. A sense line multiplexor can be coupled to the local sense line and a global sense line. A sense amplifier can be coupled to the global sense line and can be configured to sense and latch a voltage of the global sense line in response to the memory device receiving a command. A plurality of access devices can be coupled to the local sense line. A plurality of capacitors can be coupled to the plurality of access devices. A bias voltage supply, which is separate from the bleeder supply, can be coupled to the plurality of capacitors.

A thin film transistor can be implemented in three-dimensional (3D) dynamic random access memory (DRAM) and emerging memory in order to increase memory array efficiency and to reduce die sizes. In previous approaches, since the architecture of 3D memory makes grounding the transistor very difficult, the body of the transistor can be floating (e.g., not grounded) once it is implemented into a 3D memory. For instance, implementation of a thin film transistor with a floating body can result in increased memory cell leakage and/or increased voltage threshold (Vt) variation.

In contrast, embodiments of the present disclosure can provide a means to discharge the floating body of the thin film transistor by implementing a variable pre-charge voltage level for a local sense line, activating and deactivating a global sense line multiplexor and a local sense line pre-charge device, such as a bleeder device, before the voltage threshold compensation duration and after a sense amplifier that is coupled to the global sense line is activated. The pre-charge voltage level of the local sense line can be controlled via the bleeder device and can be reduced from a current cell plate voltage to a lower voltage such as a ground voltage, a positive voltage that is less than 1 volt (V) and greater than 0V, or a negative voltage that is greater than −1V and less than 0V.

The current approach as described herein can provide a means to discharge a floating body of a transistor (e.g., a thin film transistor) during an off-state (e.g., an idle-state) of the transistor. The floating body of a transistor, such as a thin film transistor, can be discharged by maintaining the local sense line at a lower voltage and thereby can provide a path to discharge the floating body of the transistor through a p-n junction of the transistor. As used herein, the term “p-n junction” refers to the boundary between a p-type semiconductor material or intrinsic semiconductor material, and a n-type semiconductor material within the transistor. For example, maintaining the local sense line at a lower voltage reduces a barrier for storing holes in the floating body of the transistor which causes some holes to be released from the floating body. As used herein, the term “holes” refers to the absence of an electron from a full valence band. The movement of holes refers to a movement of electrons that leaves holes in the different locations where the electron moved from. This indicates a movement of electrons which indicates a movement of current.

In some embodiments, setting a sense line voltage of 0.1 V can allow current to be discharged through the p-n junction coupled to the sense line and setting a storage node (e.g., capacitor) to 0 V can allow current to be discharged through the p-n junction coupled to a storage node (e.g., capacitor). In some embodiments, the floating body of the transistor can discharge the current through the p-n junction coupled to the sense line but not the p-n junction coupled to the storage node. In other embodiments, the floating body of the transistor can discharge the current through the p-n junction coupled to the storage node but not the p-n junction coupled to the sense line. In other embodiments, the floating body can be discharged from both the p-n junction coupled to the sense line and the p-n junction coupled to the storage node. Discharging the floating body of the transistor during a given state (e.g., an off-state) of a transistor in accordance with embodiments of this disclosure can result in a reduction of channel leakage in the transistor and/or less Vt variation of the transistor.

FIG.1is a block diagram of an apparatus in accordance with a number of embodiments of the present disclosure.FIG.1illustrates a circuit diagram showing a cell array of a three dimensional (3D) semiconductor memory device according to embodiments of the present disclosure.FIG.1illustrates a cell array may have a plurality of sub cell arrays101-1,101-2, . . . ,101-N. The plurality of sub cell arrays101-1,101-2, . . . ,101-N may be arranged along a second direction (D2)105. Each of the sub cell arrays, e.g., sub cell array101-2, may include a plurality of access lines107-1,107-2, . . . ,107-Q (which also may be referred to a word lines). Also, each of the sub cell arrays, e.g., sub cell array101-2, may include a plurality of shared sense lines103-1,103-2, . . . ,103-Q (which also may be referred to as bit lines, data lines, or digit lines). InFIG.1, the access lines107-1,107-2, . . . ,107-Q are illustrated extending in a first direction (D1)109and the shared sense lines103-1,103-2, . . . ,103-Q are illustrated extending in a third direction (D3)111. According to embodiments, the first direction (D1)109and the second direction (D2)105may be considered in a horizontal (“X-Y”) plane. The third direction (D3)111may be considered in a vertical (“Z”) plane. Hence, according to embodiments described herein, the shared sense lines103-1,103-2, . . . ,103-Q are extending in a vertical direction, e.g., third direction (D3)111.

A memory cell, e.g.,110, may include an access device, e.g., access transistor, and a storage node located at an intersection of each access line107-1,107-2, . . . ,107-Q and each shared sense line103-1,103-2, . . . ,103-Q. Memory cells may be written to, or read from, using the access lines107-1,107-2, . . . ,107-Q and shared sense lines103-1,103-2, . . . ,103-Q. The access lines107-1,107-2, . . . ,107-Q may conductively interconnect memory cells along horizontal rows of each sub cell array101-1,101-2, . . . ,101-N, and the sense lines103-1,103-2, . . . ,103-Q may conductively interconnect memory cells along vertical columns of each sub cell array101-1,101-2, . . . ,101-N. One memory cell, e.g.,110, may be located between one access line, e.g.,107-2, and one shared sense line, e.g.,103-2. Each memory cell may be uniquely addressed through a combination of an access line107-1,107-2, . . . ,107-Q and a shared sense line103-1,103-2, . . . ,103-Q.

The access lines107-1,107-2, . . . ,107-Q may be or include conducting patterns (e.g., metal lines) disposed on and spaced apart from a substrate. The access lines107-1,107-2, . . . ,107-Q may extend in a first direction (D1)109. The access lines107-1,107-2, . . . ,107-Q in one sub cell array, e.g.,101-2, may be spaced apart from each other in a vertical direction, e.g., in a third direction (D3)111.

The shared sense lines103-1,103-2, . . . ,103-Q may be or include conductive patterns (e.g., metal lines) extending in a vertical direction with respect to the substrate, e.g., in a third direction (D3)111. The shared sense lines in one sub cell array, e.g.,101-2, may be spaced apart from each other in the first direction (D1)109.

A gate of a memory cell, e.g., memory cell110, may be connected to an access line, e.g.,107-2, and a first conductive node, e.g., a first source/drain region of an access device, e.g., transistor, of the memory cell110may be connected to a shared sense line, e.g.,103-2. Each of the memory cells, e.g., memory cell110, may be connected to a storage node, e.g., capacitor. A second conductive node, e.g., a second source/drain region of the access device, e.g., transistor, of the memory cell110may be connected to the storage node, e.g., capacitor. While first and second source/drain region references are used herein to denote two separate and distinct source/drain regions, it is not intended that the source/drain region referred to as the “first” and/or “second” source/drain regions have some unique meaning. It is intended only that one of the source/drain regions is connected to shared sense line, e.g.,103-2, and the other may be connected to a storage node.

FIG.2illustrates a perspective view showing a three dimensional (3D) semiconductor memory device, e.g., a portion of a sub cell array101-2shown inFIG.1as a vertically oriented stack of memory cells in an array, according to some embodiments of the present disclosure.FIG.2illustrates a perspective view showing unit cell, e.g., memory cell110shown inFIG.1, of the 3D semiconductor memory device shown inFIG.2.

As shown inFIG.2, a substrate200may have formed thereon one of the plurality of sub cell arrays, e.g.,101-2, described in connection withFIG.1. For example, the substrate200may be or include a silicon substrate, a germanium substrate, or a silicon-germanium substrate, etc. Embodiments, however, are not limited to these examples.

As shown in the example embodiment ofFIG.2, the substrate200may have fabricated thereon a vertically oriented stack of memory cells, e.g., memory cell110inFIG.1, extending in a vertical direction, e.g., third direction (D3)111. According to some embodiments, the vertically oriented stack of memory cells may be fabricated such that each memory cell, e.g., memory cell110inFIG.1, is formed on plurality of vertical levels, e.g., a first level (L-1), a second level (L-2), and a Pth level (L-P). The repeating, vertical levels, L-1, L-2, and L-P, may be arranged, e.g., “stacked”, in a vertical direction, e.g., third direction (D3)111shown inFIG.1. Each of the repeating, vertical levels, L-1, L-2, and L-P may include a plurality of discrete components, e.g., regions, of the horizontally oriented access devices, e.g., transistors, and storage nodes, e.g., capacitors, including access line107-1,107-2, . . . ,107-Q connections and shared sense line103-1,103-2, . . . ,103-Q connections. The plurality of discrete components of the horizontally oriented access devices230, e.g., transistors, may be formed in a plurality of iterations of vertically, repeating layers within each level, and may extend horizontally in the second direction (D2)205, analogous to second direction (D2)105shown inFIG.1.

The plurality of discrete components of the horizontally oriented access devices230, e.g., transistors, may include a first source/drain region221and a second source/drain region223separated by a channel region225, extending laterally in the second direction (D2)205, and formed in a body of the access devices. In some embodiments, the channel region225may include silicon, germanium, silicon-germanium, and/or indium gallium zinc oxide (IGZO). In some embodiments, the first and the second source/drain regions,221and223, can include an n-type dopant region formed in a p-type doped body of the access device to form an n-type conductivity transistor. In some embodiments, the first and the second source/drain regions,221and223, may include a p-type dopant formed within an n-type doped body or undoped intrinsic body to the access device to form a p-type conductivity transistor. By way of example, and not by way of limitation, the n-type dopant may include Phosphorous (P) atoms and the p-type dopant may include atoms of Boron (B) formed in an oppositely doped body region of polysilicon semiconductor material. Embodiments, however, are not limited to these examples.

The storage node227, e.g., capacitor, may be connected to one respective end of the access device. As shown inFIG.2, the storage node227, e.g., capacitor, may be connected to the second source/drain region223of the access device. The storage node may be or include memory elements capable of storing data. Each of the storage nodes may be a memory element using one of a capacitor, a magnetic tunnel junction pattern, and/or a variable resistance body which includes a phase change material, etc. Embodiments, however, are not limited to these examples. In some embodiments, the storage node associated with each access device of a unit cell, e.g., memory cell110inFIG.1, may similarly extend in the second direction (D2)205, analogous to second direction (D2)105shown inFIG.1.

As shown inFIG.2a plurality of horizontally oriented access lines207-1,207-2, . . . ,207-Q extend in the first direction (D1)209, analogous to the first direction (D1)109inFIG.1. The plurality of horizontally oriented access lines207-1,207-2, . . . ,207-Q may be analogous to the access lines107-1,107-2, . . . ,107-Q shown inFIG.1. The plurality of horizontally oriented access lines207-1,207-2, . . . ,207-Q may be arranged, e.g., “stacked”, along the third direction (D3)211. The plurality of horizontally oriented access lines207-1,207-2, . . . ,207-Q may include a conductive material. For example, the conductive material may include one or more of a doped semiconductor, e.g., doped silicon, doped germanium, etc., a conductive metal nitride, e.g., titanium nitride, tantalum nitride, etc., a metal, e.g., tungsten (W), titanium (Ti), tantalum (Ta), ruthenium (Ru), cobalt (Co), molybdenum (Mo), etc., and/or a metal-semiconductor compound, e.g., tungsten silicide, cobalt silicide, titanium silicide, etc. Embodiments, however, are not limited to these examples.

Among each of the vertical levels, (L-1)213-1, (L-2)213-2, and (L-P)213-P, the horizontally oriented memory cells, e.g., memory cell110inFIG.1, may be spaced apart from one another horizontally in the first direction (D1)209. However, as described in more detail below in connection withFIG.4et. seq., the plurality of discrete components to the horizontally oriented access devices230, e.g., first source/drain region221and second source/drain region223separated by a channel region225, extending laterally in the second direction (D2)205, and the plurality of horizontally oriented access lines207-1,207-2, . . . ,207-Q extending laterally in the first direction (D1)209, may be formed within different vertical layers within each level. For example, the plurality of horizontally oriented access lines207-1,207-2, . . . ,207-Q, extending in the first direction (D1)209, may be formed on a top surface opposing and electrically coupled to the channel regions225, separated therefrom by a gate dielectric204, and orthogonal to horizontally oriented access devices230, e.g., transistors, extending in laterally in the second direction (D2)205. In some embodiments, the plurality of horizontally oriented access lines207-1,207-2, . . . ,207-Q, extending in the first direction (D1)209are formed in a higher vertical layer, farther from the substrate200, within a level, e.g., within level (L-1), than a layer in which the discrete components, e.g., first source/drain region221and second source/drain region223separated by a channel region225, of the horizontally oriented access device are formed.

As shown in the example embodiment ofFIG.2, the shared sense lines,203-1,203-2, . . . ,203-Q, extend in a vertical direction with respect to the substrate200, e.g., in a third direction (D3)211. Further, as shown inFIG.2, the shared sense lines,203-1,203-2, . . . ,203-Q, in one sub cell array, e.g., sub cell array101-2inFIG.1, may be spaced apart from each other in the first direction (D1)209. The shared sense lines,203-1,203-2, . . . ,203-Q, may be provided, extending vertically relative to the substrate200in the third direction (D3)211in vertical alignment with source/drain regions to serve as first source/drain regions221or, as shown, be vertically adjacent first source/drain regions221for each of the horizontally oriented access devices230, e.g., transistors, extending laterally in the second direction (D2)205, but adjacent to each other on a level213, e.g., first level (L-1)213-1, in the first direction (D1)209. Each of the shared sense lines,203-1,203-2, . . . ,203-Q, may vertically extend, in the third direction (D3), adjacent first source/drain regions221of respective ones of the plurality of horizontally oriented access devices230, e.g., transistors, that are vertically stacked. In some embodiments, the plurality of shared vertically oriented sense lines203-1,203-2, . . . ,203-Q, extending in the third direction (D3)211, may be connected to side surfaces of the first source/drain regions221directly and/or through additional contacts including metal silicides.

For example, and as shown in more detail inFIG.2, a first one of the shared vertically extending sense lines, e.g.,203-1, may be adjacent a first source/drain region221of a first one of the horizontally oriented access devices230, e.g., transistors, in the first level (L-1)213-1, a first source/drain region221of a first one of the horizontally oriented access devices230, e.g., transistors, in the second level (L-2)213-2, and a first source/drain region221a first one of the horizontally oriented access devices230, e.g., transistors, in the Pth level (L-P)213-P, etc. Similarly, a second one of the shared vertically extending sense lines, e.g.,203-2, may be adjacent a first source/drain region221of a second one of the horizontally oriented access devices230, e.g., transistors, in the first level (L-1)213-1, spaced apart from the first one of horizontally oriented access devices230, e.g., transistors, in the first level (L-1)213-1in the first direction (D1)209. And the second one of the shared vertically extending sense lines, e.g.,203-2, may be adjacent a first source/drain region221of a second one of the horizontally oriented access devices230, e.g., transistors, in the second level (L-2)213-2, and a first source/drain region221of a second one of the horizontally oriented access devices230, e.g., transistors, in the Pth level (L-P)213-P, etc. Embodiments are not limited to a particular number of levels.

The shared vertically extending sense lines,203-1,203-2, . . . ,203-Q, may include a conductive material, such as, for example, one of a doped semiconductor material, a conductive metal nitride, metal, and/or a metal-semiconductor compound. The shared sense lines,203-1,203-2, . . . ,203-Q, may correspond to shared sense lines (DL) described in connection withFIG.1.

FIG.3Aillustrates in more detail a unit cell, e.g., memory cell110inFIG.1, of the vertically stacked array of memory cells, e.g., within a sub cell array101-2inFIG.1, according to some embodiments of the present disclosure. As shown inFIG.3A, the first and the second source/drain regions,321and323, may be impurity doped regions to the laterally oriented access devices330, e.g., transistors. The first and the second source/drain regions,321and323, may be analogous to the first and the second source/drain regions221and223shown inFIG.2. The first and the second source/drain regions,321and323, may be formed from n-type or p-type dopants. Embodiments are not so limited.

For example, for an n-type conductivity transistor construction the body region of the horizontally oriented access devices330, e.g., transistors, may be formed of a low doped p-type (p−) semiconductor material or intrinsic undoped semiconductor material. In one embodiment, the body region and the channel region325separating the first and the second source/drain regions,321and323, may include a low doped, p-type (e.g., low dopant concentration (p−)) polysilicon material consisting of boron (B) atoms as an impurity dopant to the polycrystalline silicon. The first and the second source/drain regions,321and323, may also comprise a metal, and/or metal composite materials containing ruthenium (Ru), molybdenum (Mo), nickel (Ni), titanium (Ti), copper (Cu), a highly doped degenerate semiconductor material, and/or at least one of indium oxide (In2O3), or indium tin oxide (In2-xSnxO3), formed using an atomic layer deposition process, etc. Embodiments, however, are not limited to these examples. As used herein, a degenerate semiconductor material is intended to mean a semiconductor material, such as polysilicon, containing a high level of doping with significant interaction between dopants, e.g., phosphorus (P), boron (B), etc. Non-degenerate semiconductors, by contrast, contain moderate levels of doping, where the dopant atoms are well separated from each other in the semiconductor host lattice with negligible interaction.

In this example, the first and the second source/drain regions,321and323, may include a high dopant concentration, n-type conductivity impurity (e.g., high dopant (n+)) doped in the first and the second source/drain regions,321and323. In some embodiments, the high dopant, n-type conductivity first and second drain regions321and323may include a high concentration of phosphorus (P) atoms deposited therein. Embodiments, however, are not limited to this example. In other embodiments, the horizontally oriented access devices330, e.g., transistors, may be of a p-type conductivity construction in which case the impurity, e.g., dopant, conductivity types could be reversed.

The gate dielectric material304may include, for example, a high-k dielectric material, a silicon oxide material, a silicon nitride material, a silicon oxynitride material, etc., or a combination thereof. Embodiments are not so limited. For example, in high-k dielectric material examples the gate dielectric material304may include one or more of hafnium oxide, hafnium silicon oxide, lanthanum oxide, zirconium oxide, zirconium silicon oxide, tantalum oxide, titanium oxide, barium strontium titanium oxide, barium titanium oxide, strontium titanium oxide, lithium oxide, aluminum oxide, lead scandium tantalum oxide, lead zinc niobite, etc.

As shown in the example embodiment ofFIG.3A, a shared sense line, e.g.,303, analogous to the shared sense lines203-1,203-2, . . . ,203-Q inFIG.2and103-1,103-2, . . . ,103-Q inFIG.1, may be vertically extending in the third direction (D3)311adjacent the first source/drain region321in the body to the horizontally oriented access devices330, e.g., transistors horizontally conducting between the first and the second source/drain regions321and323along the second direction (D2)305.

FIG.3Billustrates a unit cell, e.g., memory cell110inFIG.1, of the vertically stacked array of memory cells, e.g., within a sub cell array101-2inFIG.1having a dual gate horizontal access device structure. As shown inFIG.3B, the first and the second source/drain regions,321and323, may be impurity doped regions to the horizontally oriented access devices330, e.g., transistors. The first and the second source/drain regions,321and323, may be analogous to the first and the second source/drain regions221and223shown inFIG.2and the first and the second source/drain regions321and323shown inFIG.3A. The first and the second source/drain regions321and323may be separated by a channel region325formed in a body of semiconductor material, e.g., body region, of the horizontally oriented access devices330, e.g., transistors. The first and the second source/drain regions,321and323, may be formed from n-type or p-type dopants. Embodiments are not so limited.

As shown in the example embodiment ofFIG.3B, a shared sense line, e.g.,303, analogous to the shared sense lines203-1,203-2, . . . ,203-Q inFIGS.2and103-1,103-2, . . . ,103-Q inFIG.1, may be vertically extending in the third direction (D3)311adjacent the first source/drain region321in the body to the horizontally oriented access devices330, e.g., transistors horizontally conducting between the first and the second source/drain regions321and323along the second direction (D2)305.

FIG.3Bshows an example embodiment having a dual gate structure wherein the horizontally oriented access devices330are formed with the conductive gate material having a top portion above the channel region325and a bottom portion below the channel region325of the semiconductor material. In one embodiment, the horizontally oriented access devices330may be formed as gate all around (GAA) horizontal access devices with the conductive gate material fully around every surface of the channel region325formed in the body of the semiconductor material.

FIG.4is a cross-sectional view of an array of memory cells in accordance with a number of embodiments of the present disclosure.FIG.4includes a sub cell array401, which can include one or more local sense lines (digit lines)428-1, . . . ,428-N (individually or collectively referred to as local sense lines428), one or more bleeder devices424-1, . . . ,424-N (individually or collectively referred to as bleeder devices424), one or more bleeder supplies432, one or more sense line multiplexors426-1,426-2, . . . ,426-N (individually or collectively referred to as sense line multiplexors426), one or more global sense line434, and one or more sense amplifiers (sense amps)438.

Further,FIG.4includes one or more plurality of capacitors412-1,412-2,412-3,412-4, . . . ,412-N (individually or collectively referred to as capacitors412) coupled to one or more plate region420-1,420-2, . . . ,420-N (individually or collectively referred to as plate regions420), a bias voltage supply436, e.g. a plate, and one or more plurality of access devices416-1,416-2,416-3,416-(N−1), . . . ,416-N (individually or collectively referred to as access devices416). In some embodiments, a plate region420can be coupled to a first side of a capacitor412and an access device416can be coupled to a second side of the capacitor412that is opposite of the first side of the capacitor412. Each coupling of a capacitor412and an access device416can form a memory cell (e.g., memory cell110inFIG.1). Each memory cell can be coupled to a local sense line428.

Each global sense line434can be coupled to a respective sense amp438. Further, each global sense line434can be coupled to one or more local sense lines428. In some embodiments, each local sense line428can be coupled to a global sense line434via a sense line multiplexor426. In some embodiments, a driver (not pictured) can be coupled to the global sense line434. The driver can be configured to drive current to a local sense line428via the global sense line434to select a memory cell (e.g., memory cell110ofFIG.1) of a stack of memory cells coupled to the local sense line428.

In some embodiments, each plate region420can be coupled to the plate bias voltage supply436. In some embodiments, the plate bias voltage supply436can be configured to drive a voltage of the plate region420to the same value as the voltage of the plate bias voltage supply436. In some embodiments, the voltage of the bias voltage supply plate436can be chosen to minimize leakage from a capacitor412of a memory cell.

In some embodiments, each local sense line428can be coupled to a first end of a respective bleeder device424and the bleeder supply432can be coupled to a second end of each bleeder device424. In some embodiments, the bleeder supply432and the plate bias voltage supply436are separate voltage supplies, in other embodiments, the bleeder supply432and the plate bias voltage supply436can be the same voltage supply. In some embodiments, the bleeder device424can be configured to drive a voltage of a local sense line428coupled to the bleeder device424to the same value as the voltage (bleeder supply voltage) of the bleeder supply432. In some embodiments, a magnitude of the bleeder supply432voltage can be a magnitude of voltage of a local sense line428that decreases leakage current in an access device416of the memory cell coupled to the local sense line428when the memory cell is in an idle state. In some embodiments, the bleeder supply432voltage can be selected to decrease the leakage current of an access device416of a memory cell when the memory cell is in a low (e.g., zero) state. In some embodiments, the magnitude of the voltage of the local sense line428that decreases the leakage current of the access device416can be 100 millivolts (mV). In some embodiments, the voltage of the bleeder supply432can be different than the voltage of the plate bias voltage supply436. In some embodiments, the bleeder supply432can be connected to an edge of a sub cell array401of memory cells. In some embodiments, a magnitude of the voltage of the bias voltage supply436and a magnitude of the voltage of the bleeder supply432can be selected to reduce the leakage current of an access device416. In a non-limiting example, magnitudes of the voltages of the bleeder supply and the plate bias voltage supply can be selected to reduce the leakage current of a access device416when the memory cell is in a low data state For example, the bias voltage supply436can be a plate with a voltage of 0.5 V, and the bleeder device424can be a multiplexor connected to a bleeder supply432, that is separate from the plate bias voltage supply436, at the edge of the array with a voltage of 100 mV.

The memory device can be configured such that a magnitude of the voltage of the global sense line434is different than the magnitude of the voltage of the local sense line428when the sense line multiplexor426is deactivated (e.g., turned off). In some embodiments, the sense amp438can sense the voltage of the global sense line434and latch the sensed voltage of the global sense line434at 0 volts (V) or 1 V when the sense line multiplexor426is activated. The sense line multiplexor426can then be deactivated and the voltage of the local sense line428can then be driven to the voltage of the bleeder supply432by the activation of the bleeder device424while the voltage of the global sense line434remains unchanged. Therefore, when the local sense line428is idle (e.g., the sense line multiplexor is turned off and the bleeder device is turned on), the global sense line434and local sense line428can have different voltages. The different voltages can result from the global sense line434and the local sense line428being biased separately by the sense amplifier438and the bleeder supply432, respectively.

The memory device can be configured such that a voltage of the bleeder supply432is equal to (substantially equal to) a value that reduces leakage current in an access device416when the local sense line428is in an idle state. In some embodiments, the bleeder supply432voltage can be selected to minimize leakage current of an access device416in a low voltage state or a high voltage state when the local sense line428to which the access device416is coupled is in an idle state. The body of the access device416can be discharged when the local sense line428is in an idle state. Embodiments are not so limited.

In some embodiments, the memory device can be configured such that the memory device includes a circuit to detect a temperature of the capacitor412or other component of the memory device. The memory device can further be configured such that the bleeder supply voltage changes based on the detected temperature of the capacitor412. For example, a circuit, such as a bandgap temperature sensor, can be used to detect a temperature of the memory device and the voltage of the bleeder supply432can be changed to minimize the voltage leakage of the access device416(e.g., transistor) at the detected temperature.

In some embodiments, the memory device can be configured such that the voltage of the bleeder supply432can change based on characteristics of the access device416, in order to minimize leakage current. The characteristics of the access device416can include, but are not limited to, materials used to form the access device416, dimensions of the access device416, deposition techniques used to form the access device416, or any combination thereof. The bleeder supply432can be configured to operate at a bleeder supply voltage. The bleeder supply voltage can be selected to reduce the leakage current in an access device416and can vary based on a type of silicon, process requirements, a function of temperature, or other characteristics of the access device416.

At block542, the method540can include providing, by a bleeder connector (e.g., bleeder supply432ofFIG.4), a bleeder supply voltage to a bleeder device (e.g., bleeder device424ofFIG.4). In some embodiments, the bleeder supply voltage can be selected to minimize a leakage current of an access device when the memory cell is in a low voltage state or a high voltage state. As stated previously, the bleeder supply can have a voltage of 100 millivolts to minimize the leakage current of a memory cell in a low voltage state or a high voltage state. In some embodiments, the bleeder device can include a multiplexor connecting a local sense line (e.g., local sense line428ofFIG.4) to the bleeder supply.

At block544, the method540can include driving, by the bleeder device, a voltage of a local sense line (e.g., local sense line428ofFIG.4) coupled to the bleeder device to a same value as the bleeder supply voltage. In some embodiments, the bleeder device can drive the bleeder supply voltage to a value that minimizes leakage in an access device when the memory cell is in a low voltage state or a high voltage state. For example, the bleeder device can drive the voltage of the local sense line to a voltage of equal to or substantially equal to100mV. In some embodiments, the bleeder device can drive the voltage of the local sense line to the same value as the bleeder supply voltage before a sense amplifier is activated.

At block546, the method540can include activating a sense line multiplexor (e.g., sense line multiplexor426ofFIG.4) coupled to the local sense line (e.g., local sense line428ofFIG.4) and the global sense line (e.g., global sense line434ofFIG.4). In some embodiments, the bleeder device (e.g., bleeder device424ofFIG.4) can be deactivated before the sense line multiplexor is activated (e.g., turned on).

At block548, the method540can include driving, by the global sense line, the voltage of the local sense line (e.g., local sense line428ofFIG.4) to (or substantially to) a voltage of the global sense line. In some embodiments, the sense amp can sense a difference in voltage of the global sense line after the global sense line applies voltage to the local sense line. Further, in some embodiments the voltage of the global sense line may have been latched by a sense amp at a magnitude of 0 V or 1 V.

At operation550, the method540can include opening a row of memory cells (e.g., memory cells110ofFIG.1) coupled to the local sense line (e.g., local sense line428). In some embodiments, the memory cells can be opened as a result of the memory cells receiving an activate command from a host. The row of memory cells can remain open while data is stored in the sense amp and until the data is written to the open row or sensed by the sense amp. In some embodiments, the capacitor opening the memory cells may dump the charge of the capacitor of the memory device onto the local sense line, and the global sense line when the sense line multiplexor is activated. A voltage of the local sense line can be less than the bias supply voltage when memory cells coupled to the local sense line are not being accessed and the voltage of the local sense line can be greater than or equal to the bias supply voltage when the memory cell is being accessed (e.g., a memory operation is being performed on the memory cell).

At block552, the method540can include sensing, by a sense amplifier (e.g., sense amplifier438ofFIG.4), the voltage of the global sense line (e.g., global sense line434ofFIG.4). In some embodiments, the sensed voltage of the global sense line is the change in the voltage of the global sense line after the access line goes high. In some embodiments, the sense amplifier can compare the sensed voltage of the global sense line to a reference voltage of a reference global sense line.

At block554, the method540can include latching, by the sense amp, the voltage of the global sense line, wherein latching the voltage of the global sense line changes the voltage of the global sense line to either 0 V or 1 V. In some embodiments, the latched voltage is based on the sensed voltage of the global sense line, the change in sensed voltage of the global sense line, or the comparison of the sensed voltage of the global sense line to a sensed voltage of a reference global sense line.

At block556, the method540can include deactivating the sense line multiplexor, wherein deactivating the sense line multiplexor lowers the voltage of the local sense line. In some embodiments, the voltage of the local sense line can be lowered to the bleeder supply (e.g., bleeder supply432ofFIG.4) voltage via the activation of the bleeder device (e.g., bleeder device424ofFIG.4). For example, the voltage of the local sense line can be lowered to 100 mV in response to sense line multiplexor being deactivated. The voltage of the global sense line after the sense line multiplexor is deactivated can be determined based on an amount of the change in the voltage of the global sense line from a first time prior to the global sense line applying the voltage to the local sense and a second time after the global sense line applies the voltage to the local sense line.

FIG.6is a block diagram of an apparatus in the form of a computing system690including a memory device693in accordance with a number of embodiments of the present disclosure. As used herein, a memory device693, a memory array699, and/or a host (e.g., controller)692, for example, might also be separately considered an “apparatus.” According to embodiments, the memory device693may comprise at least one memory array699having an access device for vertical three-dimensional (3D) memory, as has been described herein.

In this example, system690can include a host692coupled to memory device693via an interface694. The computing system690can be a personal laptop computer, a desktop computer, a digital camera, a mobile telephone, a memory card reader, or an Internet-of-Things (IoT) enabled device, among various other types of systems. A host device or host692can include a number of processing resources (e.g., one or more processors, microprocessors, or some other type of controlling circuitry) capable of accessing memory device693. The system690can include separate integrated circuits, or both the host692and the memory device693can be on the same integrated circuit. For example, the host692may be a system controller of a memory system comprising multiple memory devices693, with the control circuitry (e.g., system controller)695providing access to the respective memory devices693by another processing resource such as a central processing unit (CPU).

In the example shown inFIG.6, the host692can be responsible for executing an operating system (OS) and/or various applications (e.g., processes) that can be loaded thereto (e.g., from memory device693via system controller695). The OS and/or various applications can be loaded from the memory device693by providing access commands from the host692to the memory device693to access the data comprising the OS and/or the various applications. The host692can also access data utilized by the OS and/or various applications by sending access commands to the memory device693to retrieve said data utilized in the execution of the OS and/or the various applications.

For clarity, the system690has been simplified to focus on features with particular relevance to the present disclosure. The memory array699can be a DRAM array, SRAM array, STT RAM array, PCRAM array, TRAM array, RRAM array, NAND flash array, and/or NOR flash array, comprising at least one access device for three dimension (3D) memory. For example, the memory array699can be an unshielded DL 4F2 array such as a 3D-DRAM memory array. The array699can comprise memory cells arranged in rows coupled by access lines and columns coupled by sense lines. Although a single array699is shown inFIG.6, embodiments are not so limited. For instance, memory device693may include a number of arrays699(e.g., a number of banks of DRAM cells).

The memory device693can include address circuitry696to latch address signals provided over an interface694. The interface can include, for example, a physical interface employing a suitable protocol (e.g., a data bus, an address bus, and a command bus, or a combined data/address/command bus). Such protocol may be custom or proprietary, or the interface694may employ a standardized protocol, such as Peripheral Component Interconnect Express (PCIe), Gen-Z, CCIX, or the like. Address signals are received and decoded by a row decoder698and a column decoder682to access the memory array699. Data can be read from memory array699by sensing voltage and/or current changes on the sense lines using sensing circuitry681. The sensing circuitry681can comprise, for example, sense amplifiers that can read and latch a page (e.g., row) of data from the memory array699. The I/O circuitry697can be used for bi-directional data communication with the host692over the interface694. The read/write circuitry683can be used to write data to the memory array699or read data from the memory array699. As an example, the circuitry683can comprise various drivers, latch circuitry, etc.

Control circuitry695can decode signals provided by the host692. The signals can be commands provided by the host692. These signals can include chip enable signals, write enable signals, and address latch signals that are used to control operations performed on the memory array699, including data read operations, data write operations, and data erase operations. In various embodiments, the control circuitry695can be responsible for executing instructions from the host692. The control circuitry695can comprise a state machine, a sequencer, registers691, and/or some other type of control circuitry, which may be implemented in the form of hardware, firmware, or software, or any combination of the three. In some examples, the host692can be a controller external to the memory device693. For example, the host692can be a memory controller which can be coupled to a processing resource of a computing device.

The term semiconductor can refer to, for example, a material, a wafer, or a substrate, and includes any base semiconductor structure. “Semiconductor” is to be understood as including silicon-on-sapphire (SOS) technology, silicon-on-insulator (SOI) technology, thin-film-transistor (TFT) technology, doped and undoped semiconductors, epitaxial silicon supported by a base semiconductor structure, as well as other semiconductor structures. Furthermore, when reference is made to a semiconductor in the preceding description, previous process steps may have been utilized to form regions/junctions in the base semiconductor structure, and the term semiconductor can include the underlying materials containing such regions/junctions.

As used herein, “a number of” or a “quantity of” something can refer to one or more of such things. For example, a number of or a quantity of memory cells can refer to one or more memory cells. A “plurality” of something intends two or more. As used herein, multiple acts being performed concurrently refers to acts overlapping, at least in part, over a particular time period. As used herein, the term “coupled” may include electrically coupled, directly coupled, and/or directly connected with no intervening elements (e.g., by direct physical contact), indirectly coupled and/or connected with intervening elements, or wirelessly coupled. The term coupled may further include two or more elements that co-operate or interact with each other (e.g., as in a cause and effect relationship). An element coupled between two elements can be between the two elements and coupled to each of the two elements.

It should be recognized the term vertical accounts for variations from “exactly” vertical due to routine manufacturing, measuring, and/or assembly variations and that one of ordinary skill in the art would know what is meant by the term “perpendicular.” For example, the vertical can correspond to the z-direction. As used herein, when a particular element is “adjacent to” another element, the particular element can cover the other element, can be over the other element or lateral to the other element and/or can be in direct physical contact with the other element. Lateral to may refer to the horizontal direction (e.g., the y-direction or the x-direction) that may be perpendicular to the z-direction, for example.