KR101109555B1

KR101109555B1 - Nonvolatile memory device and reading method thereof

Info

Publication number: KR101109555B1
Application number: KR1020100057153A
Authority: KR
Inventors: 신형순; 이승준
Original assignee: 이화여자대학교 산학협력단
Priority date: 2010-06-16
Filing date: 2010-06-16
Publication date: 2012-01-31
Also published as: WO2011159070A3; WO2011159070A2; KR20110137113A

Abstract

The present invention relates to a nonvolatile memory device. The nonvolatile memory device of the present invention includes a memory cell array including memory cells connected between first and second bit lines and a source line, and reference memory cells connected between first and second reference bit lines and a source line. And a read and write circuit connected to the first and second bit lines and the source line.

Description

Nonvolatile memory device and its reading method {NONVOLATILE MEMORY DEVICE AND READING METHOD THEREOF}

The present invention relates to a memory, and more particularly to a nonvolatile memory device and a read method thereof.

A semiconductor memory device is a memory device implemented using a semiconductor such as silicon (Si), germanium (Ge, Germanium), gallium arsenide (GaAs, gallium arsenide), or indium phospide (InP). to be. Semiconductor memory devices are classified into a volatile memory device and a nonvolatile memory device.

Volatile memory devices lose their stored data when their power supplies are interrupted. Volatile memory devices include static RAM (SRAM), dynamic RAM (DRAM), and synchronous DRAM (SDRAM). A nonvolatile memory device is a memory device that retains data that has been stored even when power is turned off. A nonvolatile memory device includes a ROM (Read Only Memory), a PROM (Programmable ROM), an EPROM (Electrically Programmable ROM), an EEPROM (Electrically Erasable and Programmable ROM), a flash memory device, a PRAM ), RRAM (Resistive RAM), and FRAM (Ferroelectric RAM).

In order to reduce the production cost of semiconductor memory devices, various methods have been studied. One of the methods of reducing the production cost of the semiconductor memory device is to reduce the line width. When the line width is reduced, the degree of integration of the semiconductor memory device is improved. Improved integration increases the number of semiconductor memory chips produced from one wafer. Therefore, the production cost of the semiconductor memory device is reduced.

Another method of reducing the production cost of a semiconductor memory device is to improve the degree of integration of the semiconductor memory device through a design change. For example, when the number of conductive lines in a semiconductor memory chip is reduced, the degree of integration of the semiconductor memory device is improved and the unit cost is reduced.

It is an object of the present invention to provide a nonvolatile memory device having an improved degree of integration and a read method thereof.

In an embodiment, a nonvolatile memory device may include a memory cell array including memory cells connected between first and second bit lines and a source line; A reference memory cell array including reference memory cells coupled between first and second reference bit lines and the source line; And read and write circuits connected to the first and second bit lines and the source line.

In example embodiments, the reference memory cell array may include a first reference memory cell connected between the first reference bit line and the source line; And a second reference memory cell connected between the second reference bit line and the source line.

In an embodiment, the first reference memory cell includes a first select transistor coupled to the source line, the second reference memory cell includes a second select transistor coupled to the source line, and the first and second The two select transistors are controlled in response to a common reference word line.

In exemplary embodiments, the first reference memory cell may further include a first resistor connected to the first select transistor and the first bit line, and the second reference memory cell may include the second select transistor and the second bit. And a second resistor coupled to the line.

In an embodiment, the first resistor and the second resistor have different resistance values.

In an embodiment, in a read operation, the read and write circuit provides a second current to a selected bit line of the first and second bit lines and a first current to the first and second reference bit lines. It is configured to provide.

In an embodiment, the amount of the first current is greater than the amount of the second current.

In an embodiment, in a read operation, the read and write circuit may be configured to include a selected memory connected to the selected bit line based on a first voltage induced by the first current and a second voltage induced by the second current. And determine the resistance state of the cell.

In an embodiment, in a read operation, the read and write circuit is configured to determine the selected memory cell as a high resistance state when the second voltage has a level higher than the first voltage.

In an embodiment, in a read operation, the read and write circuit is configured to determine the selected memory cell as a low resistance state when the second voltage has a level lower than the first voltage.

In an embodiment, when the selected memory cell is written to a low resistance state, the read and write circuit is configured to provide a write current to the selected bit line of the first and second bit lines.

In an embodiment, when the selected memory cell is written to a high resistance state, the read and write circuit is configured to provide a write current to the source line, and an unselected bit line of the first and second bit lines floats. do.

In example embodiments, the read and write circuit may include first and second upper transistors connected to the first and second reference bit lines; And first and second lower transistors connected to the first and second bit lines.

In example embodiments, the read and write circuit may include a power supply circuit configured to supply a power voltage to the first and second lower transistors when the selected memory cell is written to a low resistance state; And a ground supply circuit configured to supply a ground voltage to the source line when the selected memory cell is written to a low resistance state.

In an embodiment, when the selected memory cell is written to the high resistance state, the power supply circuit is configured to supply a power voltage to the source line, and when the selected memory cell is written to the high resistance state, the ground The supply circuit is configured to supply a ground voltage to the first and second lower transistors.

In example embodiments, the read and write circuit may include a first current source configured to supply a first current to the first and second upper transistors in a read operation; A second current source configured to supply a second current to the first and second bottom transistors in a read operation; And an amplifier configured to sense a difference between the first voltage induced by the first current and the second voltage induced by the second current.

In an embodiment, the first and second upper transistors are turned on together in a read operation and turned off together in a memory cell write operation.

In example embodiments, when a selected reference memory cell of the first and second reference memory cells is written, the selected upper transistor of the first and second upper transistors is turned on and the other upper transistor is turned on. Is off.

In example embodiments, the first and second reference memory cells and the first and second memory cells each include a spin torque transfer magnetoresistive element.

According to an embodiment of the present disclosure, a method of reading a nonvolatile memory device may include: grounding a source line; Supplying a first current to an electrical path connected to the source line through two reference bit lines and two reference memory cells respectively corresponding to the two reference bit lines; Supplying a second current to an electrical path connected to the source line through a bit line and a selected memory cell; And determining a logic state of the selected memory cell based on voltages induced by the first and second currents, respectively.

According to the present invention, reference memory cells connected to two reference bit lines share one source line. Reference memory cells connected to two reference bit lines share one reference word line. Thus, a nonvolatile memory device having an improved degree of integration and a read method thereof are provided.

1 is a block diagram illustrating a nonvolatile memory device in accordance with an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a memory cell array, a reference cell array, and read and write circuits of FIG. 1.
3 is a circuit diagram illustrating a first access unit of FIG. 2.
4 is a diagram illustrating an embodiment of a memory cell of FIG. 3.
FIG. 5 is a circuit diagram illustrating the first reference access unit of FIG. 2.
6 is a circuit diagram illustrating a first read and write unit of FIG. 2.
FIG. 7 is a circuit diagram illustrating a current path of a first access unit and a first read and write unit when a selected memory cell is written in a low resistance state. FIG.
8 is a circuit diagram showing a current path of a first access unit and a first read and write unit when the selected memory cell is written in a high resistance state.
9 and 10 are circuit diagrams showing current paths of a first access unit, a first reference access unit, and a first read and write unit when a selected memory cell is read.
FIG. 11 is a circuit diagram illustrating an equivalent circuit of the first access unit, the first reference access unit, and the first read and write unit shown in FIGS. 9 and 10.
12 is a circuit diagram showing a current path of a first reference access unit and a first read and write unit when reference memory cells in high and low resistance states are written.
13 is a flowchart illustrating a reading method of a nonvolatile memory device according to an embodiment of the present invention.
FIG. 14 is a block diagram illustrating a memory system including the nonvolatile memory device of FIG. 1.
FIG. 15 is a block diagram illustrating an application example of the memory system of FIG. 14.
FIG. 16 is a block diagram illustrating a computing system including the memory system described with reference to FIG. 15.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. . Identical components will be referred to using the same reference numerals. Similar components will be referred to using similar reference numerals.

1 is a block diagram illustrating a nonvolatile memory device 100 according to an embodiment of the present invention. Referring to FIG. 1, the nonvolatile memory device 100 includes a memory cell array 110, a reference cell array 120, a read and write circuit 130, and a peripheral circuit 140.

The memory cell array 110 is connected to the read and write circuit 130 through the bit lines BL and the source lines SL and to the peripheral circuit 140 through the word lines WL. The memory cell array 110 includes a plurality of memory cells connected to bit lines BL, source lines SL, and word lines WL.

Memory cells of the memory cell array 110 may be selected and unselected through the word lines WL. The memory cells may be written into one of a plurality of logic states by a signal, for example, a voltage or a current, transmitted through the bit lines BL and the source lines SL.

In exemplary embodiments, memory cells may store data in the form of a resistance value. For example, memory cells having a first resistance value will correspond to the first logic state. Memory cells having a second resistance value will correspond to the second logic state. That is, the memory cells may be variable resistance memory cells.

The reference cell array 120 is connected to the read and write circuit 130 through the reference bit lines RBL and the reference source lines RSL, and to the peripheral circuit 140 through the reference word line RWL. do. The reference cell array 120 includes a plurality of reference memory cells connected to the reference bit lines RBL, the reference source lines RSL, and the reference word line RWL.

In exemplary embodiments, the reference memory cells of the reference cell array 120 may be configured identically to the memory cells of the memory cell array 110. That is, like the memory cells, the reference memory cells may be variable resistance memory cells.

The read and write circuit 130 is connected to the memory cell array 110 through the bit lines BL and the source lines SL. The read and write circuit 130 is configured to write data to the memory cells of the memory cell array 110 through the bit lines BL and the source lines SL. For example, the read and write circuit 130 may supply a signal, for example, a voltage or a current, to the bit lines BL and the source lines SL, thereby providing a resistance of the selected memory cell of the memory cell array 110. Will change the value.

The read and write circuit 130 is configured to read data stored in the selected memory cell of the memory cell array 110 through the bit lines BL and the source lines SL. In exemplary embodiments, the read and write circuit 130 is configured to read data stored in the memory cells using the reference memory cells of the reference cell array 120. For example, the read and write circuit 130 may compare the selected memory cell of the memory cell array 110 with the reference memory cell in the high resistance state and the reference memory cell in the low resistance state of the reference cell array 120. According to the comparison result, the read and write circuit 130 may determine data stored in the selected memory cell.

The read and write circuit 130 operates under the control of the peripheral circuit 140. The read and write circuit 130 writes the reference write signal WRR, the low resistance write signal WRL, the low resistance write inversion signal / WRL, the high resistance write signal WRH, and the high resistance write from the peripheral circuit 140. It is configured to receive the inversion signal / WRH, the read signal RD, the upper control signals WRT, and the lower control signals WRB. In response to the signals received from the peripheral circuit 140, the read and write circuit 130 is configured to perform read and write operations. The read and write circuit 130 is configured to transfer the data DOUT read from the selected memory cell of the memory cell array 110 to the peripheral circuit 140.

The peripheral circuit 140 is configured to select and deselect memory cells of the memory cell array 110 through word lines WL. The peripheral circuit 140 is configured to select and deselect reference memory cells of the reference cell array 120 through the reference word line RWL. The peripheral circuit 140 controls the read and write circuit 130 to perform read and write operations. The peripheral circuit 140 is configured to receive the data DOUT read from the read and write circuit 130.

For example, the peripheral circuit 140 may include an address decoder configured to decode an address received from an external device, a word line driver configured to drive word lines WL, and a reference configured to drive a reference word line RWL. It may include components such as word line drivers, data buffers, and the like.

2 is a block diagram illustrating the memory cell array 110, the reference cell array 120, and the read and write circuit 130 of FIG. 1.

Referring to FIG. 2, the memory cell array 110 includes first through nth access units 111 through 11n. The reference cell array 120 includes first to nth reference access units 121-12n. The read and write circuit 130 includes first to nth read and write units 131 to 13n.

The first to nth access units 111 to 11n correspond to the first to nth read and write units 131 to 13n, respectively. Each access unit is connected to a corresponding read and write unit through bit lines BL and source lines SL. Each access unit includes a plurality of memory cells.

The first to nth access units 111-11n may be configured to share the word lines WL. For example, memory cells located in the same row among the memory cells of the first through nth access units 111 through 11n may be connected to a common word line. That is, the word lines WL may extend along the row direction of the memory cells from the first access unit 111 to the nth access unit 11n.

The first to nth reference access units 121 to 12n are connected to the first to nth read and write units 131 to 13n, respectively. Each reference access unit is connected to corresponding read and write units via reference bit lines RBL and reference source lines RSL.

The first through nth reference access units 121-12n may be configured to share the reference word line RWL. For example, the reference memory cells of the first to nth reference access units 121 to 12n may be connected to a common reference word line RWL. That is, the reference word line RWL may extend along the row direction of the reference memory cells from the first reference access unit 121 to the nth reference access unit 12n.

The first to nth read and write units 131 to 13n may include a reference write signal WRR, a low resistance write signal WRL, a low resistance write inversion signal / WRL, and a high resistance write from the peripheral circuit 140. And receive the signal WRH, the high resistance write inversion signal / WRH, the read signal RD, the upper control signals WRT, and the lower control signals WRB, respectively. The first to nth read and write units 131 to 13n are configured to output the read data DOUT, respectively. That is, each read and write unit is configured to perform read and write operations in response to control of the peripheral circuit 140.

3 is a circuit diagram illustrating the first access unit 111 of FIG. 2. Referring to FIG. 3, the first access unit 111 may include first to fourth bit lines BL1 to BL4, first and second source lines SL1 and SL2, and first to kth word lines. WL1 to WLk, and a plurality of memory cells MC.

Each memory cell MC includes a selection transistor ST and a variable resistance element VR. The variable resistance element VR is connected to the bit line BL and the selection transistor ST. The selection transistor ST is connected to the source line SL.

In an exemplary embodiment, the variable resistance element VR may be configured to store data in the form of a resistance value. The resistance value of the variable resistance element VR may be changed by a signal transmitted through the bit line BL and the source line SL, for example, a voltage or a current.

The selection transistor ST is connected between the variable resistance element VR and the source line SL and operates in response to the corresponding word line WL. That is, the selection transistor ST is turned on and off in accordance with the voltage level of the word line WL. Select transistors ST located in the same row are connected to a common word line WL. Thus, the memory cells MC in a row unit are selected and deselected by the word line voltage.

As shown in FIG. 3, memory cells MC located in the same column are connected to a common bit line BL. For example, the memory cells MC located in the first column are connected to the first bit line BL1, and the memory cells MC located in the second column are connected to the second bit line BL2 and are located in the third column. The memory cells MC are connected to the third bit line BL3, and the memory cells MC located in the fourth column are connected to the fourth bit line BL4.

Memory cells MC connected to two bit lines are configured to share one source line. In exemplary embodiments, the memory cells MC connected to the first and second bit lines BL1 and BL2 share the first source line SL1, and the third and fourth bit lines BL3 and BL4. Memory cells MC connected to are configured to share the second source line SL2. That is, the memory cells MC are connected between the first and second bit lines BL1 and BL2 and the first source line SL2, and the third and fourth bit lines BL3 and BL4 and the first and second bit lines BL3 and BL4. Memory cells MC are connected between the two source lines SL2.

Since the source line SL is shared by the two bit lines BL, the number of the source lines SL is reduced in comparison with a conventional nonvolatile memory device. Thus, the degree of integration of the nonvolatile memory device 100 is improved.

4 is a diagram illustrating an embodiment of a memory cell MC of FIG. 3. Referring to FIG. 4, the variable resistance element VR and the selection transistor ST are connected between the bit line BL and the source line SL.

The variable resistance device VR includes a pinned magnetization layer PL, a free magnetization layer FL, and an intermediate layer S. The pinned magnetization layer PL includes a ferroelectric material. The pinned magnetization layer PL has a fixed magnetization direction. For example, the magnetization direction of the pinned magnetization layer PL is indicated by an arrow.

The free magnetization layer FL includes a ferroelectric material. The free magnetization layer FL has a magnetization direction that changes according to a bias condition. For example, the magnetization direction of the free magnetization layer FL is indicated by an arrow.

The intermediate layer S acts as a tunnel barrier. In exemplary embodiments, the intermediate layer S may be composed of crystallized magnesium oxide (MgO).

When the magnetization directions of the fixed magnetization layer PL and the free magnetization layer FL coincide, the variable resistance element VR may correspond to a low resistance state. When the magnetization directions of the fixed magnetization layer PL and the free magnetization layer are different, the variable resistance element VR will correspond to a high resistance state.

In exemplary embodiments, the variable resistance element VR may be a spin torque transfer magnetoresistive element.

When the write current flows from the bit line BL to the source line SL, the variable resistance element VR will be written in a low resistance state. When the write current flows from the source line SL to the bit line BL, the variable resistance element VR will be written in a high resistance state.

For example, the first access unit 111 of the first to nth access units 111 to 11n has been described with reference to FIGS. 3 and 4. However, the second to nth access units 112-11n may also be configured like the first access unit 111.

FIG. 5 is a circuit diagram illustrating the first reference access unit 121 of FIG. 2. Referring to FIG. 5, the first reference access unit 121 may include first to fourth reference bit lines RBL1 to RBL4, first and second reference source lines RSL1 and RSL2, and a reference word line RWL. And reference memory cells RMC.

The reference memory cells RMC include a selection transistor ST and a resistor. The reference memory cells RMC are configured to include one of the high resistance element RH and the low resistance element RL.

The reference memory cells RMC are commonly connected to the reference word line RWL. That is, the selection transistors ST of the reference memory cells RMC are controlled by the common reference word line RWL.

One reference memory cell RMC is connected to each reference bit line RBL. Two reference bit lines RBL correspond to one reference source line RSL. That is, two reference memory cells RMC are connected to one reference source line RSL. Two reference memory cells RMC connected to one reference source line RSL include a high resistance element RH and a low resistance element RL, respectively.

In exemplary embodiments, each reference memory cell RMC may have the same structure as the memory cell MC. That is, the high resistance element RH of the reference memory cell RMC may be the magnetoresistive element VR written in the high resistance state. The low resistance element RL of the reference memory cell RMC may be a magnetoresistive element VR written in a low resistance state.

As shown in FIG. 5, reference memory cells RMC connected to two reference bit lines RBL are configured to share one reference source line RSL. Thus, the degree of integration of the nonvolatile memory device 100 is improved. In addition, in the conventional nonvolatile memory device 100, at least two reference word lines are provided, whereas in the reference access unit 121 according to an embodiment of the present invention, the reference memory cells RMC may include one reference word line. RWL) in common. Thus, the degree of integration of the nonvolatile memory device 100 is improved. In a conventional nonvolatile memory device, a reference memory cell having a high resistance element and a reference memory cell having a low resistance element are connected to one reference bit line, whereas in the reference access unit 121 according to the embodiment of the present invention, One bit line is connected to one of a reference memory cell RMC having a high resistance element RH and a reference memory cell having a low resistance element RL. Thus, the degree of integration of the nonvolatile memory device 100 is improved.

For example, the first reference access unit 121 of the first to nth reference access units 121 to 12n has been described with reference to FIG. 5. However, the second to nth reference access units 122 to 12n may also have the same structure as the first reference access unit 121.

FIG. 6 is a circuit diagram illustrating the first read and write unit 131 of FIG. 2. Referring to FIG. 6, the first read and write unit 131 may include a power supply circuit PSC, a ground supply circuit GSC, first to fourth upper transistors TT1 to TT4, and first to fourth lower portions. Transistors TB1 to TB4, fifth to seventh transistors T5 to T7, first and second current sources CS1 and CS2, and an amplifier SA are included.

The first to fourth lower transistors TB1 to TB4 are connected to the first to fourth bit lines BL1 to BL4 of the first access unit 111 of the memory cell array 110. The first to fourth lower transistors TB1 to TB4 are connected to the fifth and seventh transistors T5 and T7. The first to fourth lower transistors TB1 to TB4 are connected to the power supply circuit PSC and the ground supply circuit GSC. The first to fourth lower transistors TB1 to TB4 operate in response to the first to fourth lower control signals WRB1 to WRB4.

The first to fourth upper transistors TT1 to TT4 are connected to the first to fourth reference bit lines RBL1 to RBL4 of the first access unit 121 of the reference cell array 120, respectively. The first to fourth upper transistors TT1 to TT4 are connected to the fifth and sixth transistors T5 and T6. The first to fourth upper transistors TT1 to TT4 are connected to a power supply circuit PSC and a ground supply circuit GSC. The first to fourth upper transistors TT1 to TT4 operate in response to the first to fourth upper control signals WRT1 to WRT4.

The power supply circuit PSC is connected to the fifth transistor T5, the first to fourth lower transistors TB1 to TB4, and the source line SL and the reference source line RSL. The power supply circuit PSC is configured to supply the power supply voltage Vcc in response to the low resistance write inversion signal / WRL and the high resistance write inversion signal / WRH. The power supply circuit PSC operates in response to the low resistance write inversion signal / WRL and operates in response to the first transistor T1 connected to the power supply voltage Vcc and the high resistance write inversion signal / WRH. The second transistor T2 is connected to the power supply voltage Vcc.

The ground supply circuit GSC is connected to the fifth transistor T5, the first to fourth lower transistors TB1 to TB4, and the source line SL and the reference source line RSL. The ground supply circuit GSC is configured to supply the ground voltage Vss in response to the low resistance write signal WRL, the high resistance write signal WRH, and the read signal RD. The ground supply circuit GSC operates in response to the low resistance write signal WRL and the read signal RD, and responds to the third transistor T3 connected to the ground voltage Vss and the high resistance write signal WRH. It operates and includes a fourth transistor T4 connected to the ground voltage Vss.

The first reference source line RSL1 and the first source line SL1 are connected to each other, and the second reference source line RSL2 and the second source line SL2 are connected to each other. That is, the source lines SL or RSL are shared in the memory cell array 110 and the reference cell array 120.

The fifth transistor includes the power supply circuit PSC, the ground supply circuit GSC, and the first to fourth lower transistors TB1 to TB4 in response to the reference write signal WRR. Electrical connection to the TT1-TT4.

The sixth transistor T6 connects the reference node RN and the first current source CS1 of the amplifier SA to the first to fourth upper transistors TT1 to TT4 and the fifth in response to the read signal RD. It is electrically connected to the transistor T5.

The seventh transistor T7 connects the cell node CN and the second current source CS2 of the amplifier SA to the first to fourth lower transistors TB1 to TB4 and the fifth in response to the read signal RD. It is electrically connected to the transistor T5.

One end of the first current source CS1 is connected to the sixth transistor T6 and the reference node RN of the amplifier SA. The other end of the first current source CS1 is connected to the power supply voltage Vcc. The first current source CS1 is configured to supply the first current 2I to the reference node RN of the sixth transistor T6 and the amplifier SA.

One end of the second current source CS2 is connected to the cell node CN of the seventh transistor T7 and the amplifier SA. The other end of the second current source CS2 is connected to the power supply voltage Vcc. The second current source CS2 is configured to supply the second current I to the cell node CN of the seventh transistor T7 and the amplifier SA. By way of example, the amount of the first current is greater than the amount of the second current. For example, the amount of the first current 2I will be twice the amount of the second current I.

The amplifier SA is configured to compare the voltage of the reference node RN with the voltage of the cell node CN. The amplifier SA is configured to output the comparison result as the read data DOUT.

FIG. 7 is a circuit diagram illustrating a current path of the first access unit 111 and the first read and write unit 131 when the selected memory cell MC is written in the low resistance state. For example, it is assumed that the memory cell MC connected to the first bit line BL1 is selected. The selection transistor ST of the selected memory cell MC may be turned on under the control of the word line WL.

Table 1 shows the bias conditions of the control signals when the selected memory cell MC is written to the low resistance state.

WRT1 WRT2 WRT3 WRT4 WRB1 WRB2 WRB3 WRB4 low low low low high low low low WRL / WRL WRH / WRH RD WRR high low low high low low

7 and 8 and Table 1, during the write operation, the first to fourth upper control signals WRT1 to WRT4 are controlled to be logic low. That is, the first to fourth upper transistors TT1 to TT4 are turned off.

The control signal WRB1 corresponding to the selected memory cell MC among the first to fourth lower control signals WRB1 to WRB4 is controlled to be logic high, and the remaining control signals WRB2 to WRB4 are controlled to be logic low. do. That is, the lower transistor TB1 connected to the bit line BL1 corresponding to the selected memory cell MC is turned on, and the remaining lower transistors TB2 to TB4 are turned off. For example, when the memory cell MC connected to the first bit line BL1 is written, the first lower control signal WRB1 may be controlled to be logic high. That is, the first lower transistor TB1 connected to the first bit line BL1 may be turned on.

In the low resistance write operation, the low resistance write signal WRL is controlled at logic high and the high resistance write signal WRH is controlled at logic low. Thus, the low resistance write inversion signal / WRL is controlled to logic low and the high resistance write inversion signal / WRH is controlled to logic high. That is, the first transistor T1 of the power supply circuit PSC is turned on and the second transistor T2 is turned off. The third transistor T3 of the ground supply circuit GSC is turned on and the fourth transistor T4 is turned off.

In the write operation, the read signal RD and the reference write signal WRR are controlled to be logic low.

In response to the bias conditions described in Table 1, the first read and write unit 131 forms a current path that is connected to the selected memory cell MC. The current path formed by the first read and write unit 131 is shown in FIG. 7.

As illustrated in FIG. 7, the power supply circuit PSC may include a first lower transistor TB1, a first bit line BL1, a variable resistance element VR, a select transistor ST, and a first source line. It is transmitted to the ground supply circuit GSC through SL1). That is, the power supply circuit PSC supplies the power supply voltage Vcc to the first bit line BL1, and the ground supply circuit GSC supplies the ground voltage Vss to the first source line SL1. Can be understood. Since current flows from the first bit line BL1 to the first source line SL1 through the variable resistance element VR, the variable resistance element VR of the selected memory cell MC will be written in a low resistance state. .

For example, the first bit line BL1 has been described as being selected. However, even when one of the second to fourth bit lines BL2 to BL4 is selected, the selected memory cell MC will be written in a low resistance state as described with reference to FIGS. 6 and 7.

For example, when the second bit line BL2 is selected, the power supply circuit PSC supplies the power supply voltage Vcc to the second bit line BL2 and the ground supply circuit GSC supplies the first source line. The ground voltage Vss will be supplied to SL1. That is, the current will flow from the second bit line BL2 to the first source line SL1 through the selected memory cell MC.

8 is a circuit diagram illustrating a current path of the first access unit 111 and the first read and write unit 131 when the selected memory cell MC is written in the high resistance state. For example, it is assumed that the memory cell MC connected to the first bit line BL1 is selected. The selection transistor ST of the selected memory cell MC may be turned on under the control of the word line.

Table 2 shows the bias conditions of the control signals when the selected memory cell MC is written to the high resistance state.

WRT1 WRT2 WRT3 WRT4 WRB1 WRB2 WRB3 WRB4 low low low low high low low low WRL / WRL WRH / WRH RD WRR low high high low low low

6, 8, and 2, an operation of writing the selected memory cell MC in a high resistance state will be described.

Compared with the bias conditions of Table 1, the bias of the high resistance write signal (WRH), high resistance write inversion signal (/ WRH), low resistance write signal (WRL), and low resistance write inversion signal (/ WRL) in Table 2 The conditions are described differently. The high resistance write signal (WRH), the high resistance write inversion signal (/ WRH), the low resistance write signal (WRL), and the low resistance write inversion signal (/ WRL) are the power supply circuit (PSC) and the ground supply circuit (GSC). Are the signals provided to Thus, as compared with the low resistance write operation, the operations of the power supply circuit PSC and the ground supply circuit GSC during the high resistance write operation will be changed.

In the high resistance write operation, the low resistance write signal WRL is controlled to a logic low and the high resistance write signal WRH is controlled to a logic high. Thus, the low resistance write inversion signal / WRL is controlled at logic high and the high resistance write inversion signal / WRH is controlled at logic low.

In response to the bias conditions described in Table 2, the first read and write unit 131 forms a current path that is connected to the selected memory cell MC. The current path formed by the first read and write unit 131 is shown in FIG. 8.

It will be understood that the power supply circuit PSC supplies the power supply voltage Vcc to the first source line SL1, and the ground supply circuit GSC supplies the ground voltage Vss to the first bit line BL1. Can be. Since the current flows from the first source line SL1 to the first bit line BL1 through the variable resistance element VR, the variable resistance element VR is written in a high resistance state.

As described with reference to the low resistance write operation, the first bit line BL1 is not limited to being selected. For example, when the second bit line BL2 is selected, the power supply circuit PSC supplies the power supply voltage Vcc to the first source line SL1 and the ground supply circuit GSC supplies the second bit line. The ground voltage Vss will be supplied to BL2. That is, current may flow from the first source line SL1 to the second bit line BL2 through the selected memory cell MC.

9 and 10 are circuit diagrams showing current paths of the first access unit 111, the first reference access unit 121, and the first read and write unit 131 when the selected memory cell MC is read. to be. For example, it is assumed that the memory cell MC of the first bit line BL1 is selected. The selection transistor ST of the selected memory cell MC will be turned on. In a read operation, in response to the reference word line RWL, the selection transistors ST of the reference memory cells RMC may be turned on.

Table 3 shows the bias conditions of the control signals when the selected memory cell MC is read.

WRT1 WRT2 WRT3 WRT4 WRB1 WRB2 WRB3 WRB4 high high low low high low low low WRL / WRL WRH / WRH RD WRR low high low high high low

6, 9, 10, and 3, the operation of reading the selected memory cell MC will be described.

In the read operation, the upper transistors TT1 and TT2 connected to the reference bit lines RBL1 and RBL2 of the first reference access unit 121 corresponding to the selected source line SL1 of the first access unit 111. Is turned on. That is, the first and second upper control signals WRT1 and WRT2 are controlled at logic high.

In a read operation, the read signal RD is controlled to be logic high.

In response to the bias conditions described in Table 3, the first read and write unit 131 forms a current path that is connected to the selected memory cell MC. Since the lower transistor TB1 and the upper transistors TT1 and TT2 corresponding to the selected memory cell MC are turned on, the first access unit 111 and the first reference access unit 121 may read the first read and the second. The writing unit 131 is connected together.

The current path between the first reference access unit 121 and the first read and write unit 131 is shown in FIG. 9.

In response to the read signal RD, the sixth transistor T6 is turned on. That is, the first current source CS1 supplies the first current 2I to the first and second upper transistors TT1 and TT2. The first current 2I is supplied to the reference memory cell RMC having the variable resistance element RH in the high resistance state and the reference memory cell RMC having the variable resistance element RL in the low resistance state.

In response to the read signal RD, the third transistor T3 of the ground supply circuit GSC supplies the ground voltage Vss to the selected reference source line RSL1. That is, the first current 2I is supplied to the variable resistance elements RL and RH in the low and high resistance states connected in parallel to the ground node provided by the ground supply circuit GSC.

The current path between the first access unit 111 and the first read and write unit 131 is shown in FIG. 10.

In response to the read signal RD, the seventh transistor T7 is turned on. That is, the second current source CS2 supplies the second current I to the first lower transistor TB1. The second current I is supplied to the variable resistance element VR of the selected memory cell MC.

In response to the read signal RD, the third transistor T3 of the ground supply circuit GSC supplies the ground voltage Vss to the selected source line SL1. That is, the variable resistance element VR of the selected memory cell MC is connected to the ground node provided by the ground supply circuit GSC.

The first access unit 111, the first reference access unit 121, and the first read and write unit 131 illustrated in FIGS. 9 and 10 may be equivalently represented by the circuit illustrated in FIG. 11. .

The voltage of the reference node RN of the amplifier SA is derived as shown in Equation (1).

The voltage of the cell node CN of the amplifier SA is derived as in Equation 2.

The amplifier SA is configured to compare the voltage of the cell node CN with the voltage of the reference node RN. The comparison result is output as read data DOUT.

When the voltage of the reference node RN described in Equation 1 is subtracted from the voltage of the cell node CN described in Equation 2, Equation 3 is derived.

The variable resistance element VR has a high resistance value RH or a low resistance value RL. When the variable resistance element VR has a high resistance value RH, Equation 3 is derived as in Equation 4.

Equation 4 has a positive value. That is, when the variable resistance element VR has a high resistance value RH, the voltage level of the cell node CN is higher than the voltage level of the reference node RN.

When the variable resistance element VR has a low resistance RL value, Equation 3 is derived as in Equation 5.

Equation 5 has a negative value. That is, when the variable resistance element VR has a low resistance RL value, the voltage level of the cell node CN is lower than the voltage level of the reference node RN.

Therefore, when the variable resistance element VR has a high resistance value RH, the amplifier SA outputs a logic high as read data. When the variable resistance element VR has a low resistance RL value, the amplifier SA outputs a logic low as read data.

FIG. 12 is a circuit diagram illustrating a current path of the first reference access unit 121 and the first read and write unit 131 when the reference memory cells RMC in the high and low resistance states are written. For example, it is assumed that reference memory cells RMC connected to the first reference source line RSL1 are selected. The selection transistor ST of the selected reference memory cells RMC may be turned on under the control of the reference word line RWL.

Table 4 shows the bias conditions of the control signals when the selected reference memory cell RMC is written.

WRT1 WRT2 WRT3 WRT4 WRB1 WRB2 WRB3 WRB4 low / high high / low low low low low low low WRL / WRL WRH / WRH RD WRR high / low low / high low / high high / low low high

12 and 4, in the write operation, the first to fourth lower control signals WRB1 to WRB4 are controlled to be logic low. That is, the first to fourth lower transistors TB1 to TB4 are turned off.

The selected control signal of the first and second upper control signals WRT1 and WRT2 corresponding to the selected first reference source line SL1 is controlled to be logic high, and the unselected control signal is controlled to be logic low.

When the selected reference memory cell RMC is written to the low resistance state RL, the low resistance write signal WRL is logic high, the low resistance write inversion signal / WRL is logic low, and the high resistance write signal WRH will be controlled at logic low and the low resistance write inversion signal (/ WRH) will be controlled at logic high.

When the selected reference memory cell RMC is written to the high resistance state RH, the low resistance write signal WRL is logic low, the low resistance write inversion signal / WRL is logic high, and the high resistance write signal WRH will be controlled at logic high and the low resistance write inversion signal (/ WRH) will be controlled at logic low.

FIG. 13 is a flowchart illustrating a read method of a nonvolatile memory device 100 according to an exemplary embodiment of the inventive concept. 9, 10, and 13, in step S110, the source line SL is grounded. For example, the ground supply circuit GSC will supply the ground voltage VSS to the selected source line SL.

In operation S120, the first current 2I is supplied to a path connected to the reference source line RSL through two reference bit lines RBL and two reference memory cells RMC. For example, the first current source CS1 will supply the first current 2I.

In operation S130, the second current I is supplied to a path connected to the source line SL through the bit line BL and the selected memory cell MC. For example, the second current source CS2 will supply the second current I.

In step S140, the first and second voltages induced by the first and second currents 2I and I, respectively, are compared. For example, the amplifier SA will compare the voltage of the reference node RN induced by the first current 2I with the voltage of the cell node CN induced by the second current I.

In step S150, the first voltage (eg, the voltage of the reference node RN) and the second voltage (eg, the voltage of the cell node CN) are compared. If the second voltage (for example, the voltage of the cell node CN) is greater than the first voltage (for example, the voltage of the reference node RN), the selected memory cell MC is in the high resistance state (S160). RH). For example, the amplifier SA will output a logic high as data read.

If the second voltage (eg, the voltage of the cell node CN) is smaller than the first voltage (eg, the voltage of the reference node RN), the selected memory cell is determined to be in the low resistance state in step S170. . For example, amplifier SA will output a logic low as read data.

As described above, in the nonvolatile memory device 100 according to an embodiment of the present invention, two bit lines BL and two reference bit lines RBL are provided with one source line SL and a reference source, respectively. Configured to share the line RSL. In addition, the reference memory cells RMC are commonly connected to one reference word line RWL, and the number of reference memory cells RMC is reduced. Thus, a nonvolatile memory device 100 having a reduced area and a read method thereof are provided.

In the above-described embodiment, each access unit has been described as being connected to four bit lines BL and two source lines SL. However, the number of bit lines BL and source lines of each access unit is not limited. Similarly, the number of reference bit lines RBL and reference source lines RSL of each reference access unit is not limited.

In the above-described embodiment, an access unit and a reference access unit have been described based on rows and columns. However, rows and columns are terms according to the relative positions of the access unit and the reference access unit, and are not limited.

FIG. 14 is a block diagram illustrating a memory system 1000 including the nonvolatile memory device 100 of FIG. 1. Referring to FIG. 14, the memory system 1000 includes a nonvolatile memory device 100 and a controller 200.

The controller 200 is connected to a host and the nonvolatile memory device 100. In response to a request from the host, the controller 200 is configured to access the nonvolatile memory device 100. For example, the controller 200 is configured to control read, write, and erase operations of the nonvolatile memory device 100 in response to a request of a host. The controller 200 is configured to control the background operation of the nonvolatile memory device 100. The controller 200 is configured to provide an interface between the nonvolatile memory device 100 and a host. The controller 200 is configured to drive firmware for controlling the nonvolatile memory device 100.

In exemplary embodiments, the controller 200 is configured to provide the control signal CTRL and the address ADDR to the nonvolatile memory device 100. The controller 200 is configured to exchange data DATA with the nonvolatile memory device 100.

In exemplary embodiments, the controller 200 may include well-known components, such as random access memory (RAM), a processing unit, a host interface, and a memory interface. The RAM is used as at least one of an operating memory of the processing unit, a cache memory between the nonvolatile memory device 100 and the host, and a buffer memory between the nonvolatile memory device 100 and the host. do. The processing unit controls the overall operation of the controller 200.

The host interface includes a protocol for performing data exchange between the host and the controller 200. For example, the controller 200 may include a universal serial bus (USB) protocol, a multimedia card (MMC) protocol, a peripheral component interconnection (PCI) protocol, a PCI-express (PCI-express) protocol, an Advanced Technology Attachment (ATA) protocol, Serial-ATA protocol, Parallel-ATA protocol, small computer small interface (SCSI) protocol, enhanced small disk interface (ESDI) protocol, and integrated drive electronics (IDE) protocol, Firewire protocol, Personal Computer Memory Card International Association (PCMCIA) protocol And communicate with an external (host) via at least one of various interface protocols, such as the like. The memory interface interfaces with the nonvolatile memory device 100. For example, the memory interface includes a NAND interface or a NOR interface.

The memory system 1000 may be configured to additionally include an error correction block. The error correction block is configured to detect and correct an error of data read from the nonvolatile memory device 100 using an error correction code (ECC). By way of example, the error correction block is provided as a component of the controller 200. The error correction block may be provided as a component of the nonvolatile memory device 100.

The controller 200 and the nonvolatile memory device 100 may be integrated into one semiconductor device. In exemplary embodiments, the controller 200 and the nonvolatile memory device 100 may be integrated into one semiconductor device to configure a memory card. For example, the controller 200 and the nonvolatile memory device 100 may be integrated into a single semiconductor device, such as a personal computer memory card international association (PCMCIA), a smart media card (SM, SMC), a memory stick, and a multimedia. Memory cards such as cards (MMC, RS-MMC, MMCmicro) and SD cards (SD, miniSD, microSD, SDHC) are constituted.

The controller 300 and the nonvolatile memory device 100 are integrated into one semiconductor device to form a solid state drive (SSD). A semiconductor drive (SSD) includes a storage device configured to store data in a semiconductor memory. When the memory system 1000 is used as the semiconductor drive SSD, an operation speed of a host connected to the memory system 1000 is significantly improved.

As another example, the memory system 1000 may include a computer, an ultra mobile PC (UMPC), a workstation, a net-book, a personal digital assistant (PDA), a portable computer, a tablet computer, a web. Tablets, web tablets, wireless phones, mobile phones, smart phones, e-books, portable multimedia players, portable game consoles, navigation Devices, black boxes, digital cameras, digital multimedia broadcasting (DMB) players, digital audio recorders, digital audio players, digital picture recorders , A digital picture player, a digital video recorder, a digital video player, a device that can transmit and receive information in a wireless environment, and a variety of electronic devices that make up a home network. Various components of an electronic device, such as one of various electronic devices constituting a computer network, one of various electronic devices constituting a telematics network, one of various components constituting an RFID device, or a computing system Provided as one of the

In exemplary embodiments, the nonvolatile memory device 100 or the memory system 1000 may be mounted in various types of packages. For example, the nonvolatile memory device 100 or the memory system 1000 may include a Package on Package (PoP), Ball grid arrays (BGAs), Chip scale packages (CSPs), Plastic Leaded Chip Carrier (PLCC), and Plastic Dual In. Line Package (PDIP), Die in Waffle Pack, Die in Wafer Form, Chip On Board (COB), Ceramic Dual In-Line Package (CERDIP), Plastic Metric Quad Flat Pack (MQFP), Thin Quad Flatpack (TQFP), Small Outline (SOIC), Shrink Small Outline Package (SSOP), Thin Small Outline (TSOP), Thin Quad Flatpack (TQFP), System In Package (SIP), Multi Chip Package (MCP), Wafer-level Fabricated Package (WFP) It is packaged and mounted in the same way as Wafer-Level Processed Stack Package (WSP).

FIG. 15 is a block diagram illustrating an application example of the memory system 1000 of FIG. 14. Referring to FIG. 15, the memory system 2000 includes a nonvolatile memory device 300 and a controller 400. The nonvolatile memory device 300 includes a plurality of nonvolatile memory chips. The plurality of nonvolatile memory chips are divided into a plurality of groups. Each group of the plurality of nonvolatile memory chips is configured to communicate with the controller 400 through one common channel. In FIG. 15, the plurality of nonvolatile memory chips are illustrated to communicate with the controller 400 through the first through kth channels CH1 through CHk. Each nonvolatile memory chip is configured as described with reference to FIGS. 1 to 13. The controller 400 is configured as described with reference to FIG. 14.

FIG. 16 is a block diagram illustrating a computing system 3000 including the memory system 2000 described with reference to FIG. 15. Referring to FIG. 16, the computing system 3000 includes a central processing unit 3100, a random access memory (RAM) 3200, a user interface 3300, a power supply 3400, and a memory system 2000. .

The memory system 2000 is electrically connected to the CPU 3100, the RAM 3200, the user interface 3300, and the power supply 3400 through the system bus 3500. Data provided through the user interface 3300 or processed by the central processing unit 3100 is stored in the memory system 2000. The memory system 2000 includes a controller 400 and a nonvolatile memory device 300.

In FIG. 16, the nonvolatile memory device 300 is illustrated as being connected to the system bus 3500 through the controller 400. However, the nonvolatile memory device 300 may be configured to be directly connected to the system bus 3500.

In FIG. 16, the memory system 2000 described with reference to FIG. 15 is provided. However, the memory system 2000 may be replaced with the memory system 1000 described with reference to FIG. 14.

In exemplary embodiments, the computing system 300 may be configured to include all of the memory systems 1000 and 2000 described with reference to FIGS. 14 and 15.

In the detailed description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope and spirit of the present invention. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be determined by the claims equivalent to the claims of the present invention as well as the claims of the following.

100; Nonvolatile memory device
MC; Memory cell
RMC; Reference memory cell
BL; Bit line
RBL; Reference bit line
SL; Source lines
RSL; Reference source line
WL; Word line
RWL; Reference word line
SA; amplifier
PSC; Power supply circuit
GSC; Ground supply circuit
CS1; First current source
CS2; Second current source

Claims

A memory cell array including memory cells coupled between the first and second bit lines and one source line;
A reference memory cell array including reference memory cells coupled between first and second reference bit lines and the one source line; And
And a read and write circuit connected to the first and second bit lines and the one source line.

The method of claim 1,
The reference memory cell array
A first reference memory cell coupled between the first reference bit line and the one source line; And
And a second reference memory cell coupled between the second reference bit line and the one source line.

The method of claim 2,
The first reference memory cell includes a first select transistor connected to the one source line,
The second reference memory cell comprises a second select transistor coupled to the one source line, and
And the first and second select transistors are controlled in response to a common reference word line.

The method of claim 3, wherein
The first reference memory cell further comprises a first resistor coupled to the first select transistor and the first bit line, and
The second reference memory cell further includes a second resistor connected to the second select transistor and the second bit line.

The method of claim 4, wherein
The nonvolatile memory device of claim 1, wherein the first resistor and the second resistor have different resistance values.

The method of claim 1,
In a read operation, the read and write circuit is configured to provide a second current to a selected bit line of the first and second bit lines and to provide a first current to the first and second reference bit lines. Nonvolatile memory device.

The method according to claim 6,
And the amount of the first current is greater than the amount of the second current.

The method of claim 7, wherein
In a read operation, the read and write circuit is based on the first voltage induced by the first current and the second voltage induced by the second current, the resistance state of the selected memory cell connected to the selected bit line. The nonvolatile memory device is configured to determine.

The method of claim 8,
In a read operation, the read and write circuit is configured to determine the selected memory cell as a high resistance state when the second voltage has a level higher than the first voltage.

The method of claim 8,
In a read operation, the read and write circuit is configured to determine the selected memory cell to a low resistance state when the second voltage has a level lower than the first voltage.

The method of claim 1,
And when the selected memory cell is written to a low resistance state, the read and write circuit is configured to provide a write current to the selected bit line of the first and second bit lines.

The method of claim 1,
When the selected memory cell is written to a high resistance state, the read and write circuit is configured to provide a write current to the one source line,
And a non-selected bit line of the first and second bit lines is floated.

The method of claim 1,
The read and write circuit
First and second upper transistors connected to the first and second reference bit lines; And
And a first and second lower transistors connected to the first and second bit lines.

The method of claim 13,
The read and write circuit
A power supply circuit configured to supply a power voltage to the first and second lower transistors when the selected memory cell is written to a low resistance state; And
And a ground supply circuit configured to supply a ground voltage to the one source line when the selected memory cell is written to a low resistance state.

The method of claim 14,
When the selected memory cell is written to a high resistance state, the power supply circuit is configured to supply a power supply voltage to the one source line, and
And when the selected memory cell is written to a high resistance state, the ground supply circuit is configured to supply ground voltages to the first and second lower transistors.

The method of claim 13,
The read and write circuit
A first current source supplying a first current to the first and second upper transistors in a read operation;
A second current source configured to supply a second current to the first and second bottom transistors in a read operation; And
And an amplifier configured to sense a difference between a first voltage induced by the first current and a second voltage induced by the second current.

The method of claim 13,
And the first and second upper transistors are turned on together in a read operation and turned off together in a memory cell write operation.

The method of claim 13,
When the selected reference memory cell of the first and second reference memory cells is written, the selected upper transistor of the first and second upper transistors is turned on, and the other upper transistor is turned off. Memory device.

The method of claim 1,
And the first and second reference memory cells and the first and second memory cells each include a spin torque transfer magneto-resistive element.

Grounding one source line;
Supplying a first current to an electrical path connected to the one source line through two reference bit lines and two reference memory cells respectively corresponding to the two reference bit lines;
Supplying a second current to an electrical path connected to the one source line through a bit line and a selected memory cell; And
Determining a logic state of the selected memory cell based on voltages induced by the first and second currents, respectively.