WO2012147315A1 - 抵抗変化型不揮発性記憶装置およびその駆動方法 - Google Patents
抵抗変化型不揮発性記憶装置およびその駆動方法 Download PDFInfo
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- WO2012147315A1 WO2012147315A1 PCT/JP2012/002725 JP2012002725W WO2012147315A1 WO 2012147315 A1 WO2012147315 A1 WO 2012147315A1 JP 2012002725 W JP2012002725 W JP 2012002725W WO 2012147315 A1 WO2012147315 A1 WO 2012147315A1
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0021—Auxiliary circuits
- G11C13/0069—Writing or programming circuits or methods
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0007—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements comprising metal oxide memory material, e.g. perovskites
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0021—Auxiliary circuits
- G11C13/004—Reading or sensing circuits or methods
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C29/00—Checking stores for correct operation ; Subsequent repair; Testing stores during standby or offline operation
- G11C29/04—Detection or location of defective memory elements, e.g. cell constructio details, timing of test signals
- G11C29/50—Marginal testing, e.g. race, voltage or current testing
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C29/00—Checking stores for correct operation ; Subsequent repair; Testing stores during standby or offline operation
- G11C29/04—Detection or location of defective memory elements, e.g. cell constructio details, timing of test signals
- G11C29/50—Marginal testing, e.g. race, voltage or current testing
- G11C2029/5006—Current
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C2213/00—Indexing scheme relating to G11C13/00 for features not covered by this group
- G11C2213/70—Resistive array aspects
- G11C2213/72—Array wherein the access device being a diode
Definitions
- the present invention relates to a variable resistance nonvolatile memory device and a driving method thereof, and in particular, reversibly transitions between a low resistance state and a high resistance state having a higher resistance value than the low resistance state by application of a voltage pulse.
- the present invention relates to a variable resistance nonvolatile memory device having a memory cell composed of a variable resistance element and a current control element represented by a diode element, and a driving method thereof.
- the resistance change element refers to an element having a property that the resistance value reversibly changes by an electrical signal, and further capable of storing data corresponding to the resistance value in a nonvolatile manner.
- nonvolatile memory device using a resistance change element As a nonvolatile memory device using a resistance change element, a so-called 1T1R type memory in which a MOS transistor and a resistance change element are connected in series at a position near the intersection of a bit line and a word line arranged orthogonally A nonvolatile memory device in which cells are arranged in a matrix is generally known.
- a non-volatile memory device having a cross-point structure in which memory cells called 1D1R type using a diode that is a current control element instead of a transistor and arranged in a matrix is generally known (for example, a patent) References 1 and 2).
- Patent Document 1 discloses a 1D1R type nonvolatile memory device using a variable resistance element having bidirectional resistance change characteristics as a memory cell.
- Patent Document 2 discloses a 1D1R type memory cell using a unidirectional variable resistance element as a memory cell.
- JP 2006-203098 A (FIG. 2) JP 2009-199695 A (FIG. 6)
- an object of the present invention is to provide a highly reliable resistance change nonvolatile memory device capable of stable operation and a method of driving the resistance change nonvolatile memory device. .
- a variable resistance nonvolatile memory device includes a resistance change element whose resistance value reversibly changes in accordance with an applied voltage pulse, and is connected in series with the resistance change element.
- a plurality of memory cells configured with current control elements through which a current that is considered to be conductive when a predetermined threshold voltage is exceeded, and each of the plurality of solid intersections of a plurality of word lines and a plurality of bit lines Selecting at least one from the plurality of word lines and selecting at least one from the plurality of bit lines, thereby selecting at least one or more memory cells from the memory cell array.
- a memory cell selection circuit for selecting the memory cell; and applying a voltage pulse to the selected memory cell to A write circuit for rewriting the resistance value of the resistance change element, and a first voltage higher than the threshold voltage or a second voltage lower than the threshold voltage is applied to the current control element of the selected memory cell.
- a read circuit that reads a state of the selected memory cell by applying a voltage to the selected memory cell, and the write circuit uses a first low-resistance pulse as the voltage pulse, or Applying the first high-resistance pulse to the selected memory cell, thereby causing the resistance change element of the selected memory cell among the plurality of memory cells to be in a first low-resistance state, or 1 in a high resistance state, and the read circuit applies the first voltage to the selected memory cell to thereby change the resistance variable element of the selected memory cell.
- the resistance state of the resistance change element of the selected memory cell is read, if a current of a predetermined value or more flows through the selected memory cell, the read circuit is selected.
- the memory cell is determined to be a defective memory cell having a short circuit defect, and the write circuit is disposed on at least one of the same bit line as the defective memory cell and the same word line as the defective memory cell.
- the resistance change element of the other memory cell is set to a third high resistance state indicating a resistance value equal to or higher than the resistance value of the first high resistance state. A second high resistance pulse is applied.
- FIG. 1 is a schematic diagram showing a basic structure of a memory cell according to an embodiment of the present invention.
- FIG. 2 is an equivalent circuit diagram of the memory cell according to the embodiment of the present invention.
- FIG. 3A is a diagram illustrating the voltage-current characteristics of the memory cell.
- FIG. 3B is a diagram illustrating a resistance voltage characteristic of the variable resistance element.
- FIG. 4 is a diagram showing voltage-current characteristics of normal memory cells and defective memory cells.
- FIG. 5 is a configuration diagram of a variable resistance nonvolatile memory device.
- FIG. 6A is a diagram illustrating an example of an address conversion table.
- FIG. 6B is a circuit diagram illustrating an example of a configuration of the reading circuit.
- FIG. 7 is a circuit diagram for explaining a current path in the read mode.
- FIG. 1 is a schematic diagram showing a basic structure of a memory cell according to an embodiment of the present invention.
- FIG. 2 is an equivalent circuit diagram of the memory cell according to the embodiment of the
- FIG. 8 is an equivalent circuit diagram of the circuit diagram of FIG.
- FIG. 9 is a circuit diagram for explaining a current path in the read mode.
- FIG. 10 is an equivalent circuit diagram of the circuit diagram of FIG.
- FIG. 11 is a circuit diagram for explaining a current path in the cell characteristic determination mode.
- 12 is an equivalent circuit diagram of the circuit diagram of FIG.
- FIG. 13 is a truth table for each mode.
- FIG. 14 is an example of a determination flow in the cell characteristic determination mode.
- FIG. 15 is an example of a determination flow in the cell characteristic determination mode.
- FIG. 16 is an example of a determination flow in the relief mode.
- FIG. 17 is a circuit diagram showing an example of the configuration of the write circuit.
- FIG. 18 is a diagram illustrating an example of voltage-current characteristics of the voltage applied to the selected bit line and the flowing current.
- FIG. 19 is a circuit diagram showing an example of the configuration of the write circuit.
- FIG. 20 is an example of a determination flow in the relief mode.
- FIG. 21 is a diagram illustrating an example of voltage-current characteristics of the voltage applied to the selected bit line and the flowing current.
- FIG. 22A is a configuration diagram of a variable resistance nonvolatile memory device.
- FIG. 22B is a diagram showing an example of the arrangement of the main memory cell array and the redundant memory cell array.
- FIG. 22C is a diagram showing an example of the arrangement of the main memory cell array and the redundant memory cell array.
- FIG. 22A is a configuration diagram of a variable resistance nonvolatile memory device.
- FIG. 22B is a diagram showing an example of the arrangement of the main memory cell array and the redundant memory cell array.
- FIG. 22C is a diagram showing an example of the arrangement of the main memory
- FIG. 22D is a diagram showing an example of the arrangement of the main memory cell array and the redundant memory cell array.
- FIG. 23A is a circuit diagram showing an example of the configuration of the bit line control voltage generation circuit.
- FIG. 23B is a circuit diagram showing an example of the configuration of the bit line control voltage generation circuit.
- FIG. 23C is a circuit diagram showing an example of the configuration of the bit line control voltage generation circuit.
- FIG. 24 is a circuit diagram illustrating an example of a configuration of a reading circuit.
- FIG. 25 is a circuit diagram illustrating an example of a configuration of a reading circuit.
- FIG. 26 is an example of an inspection flow in the cell characteristic determination mode.
- FIG. 27 is a circuit diagram illustrating an example of the configuration of the readout circuit.
- FIG. 23A is a circuit diagram showing an example of the configuration of the bit line control voltage generation circuit.
- FIG. 23B is a circuit diagram showing an example of the configuration of the bit line control voltage generation circuit.
- FIG. 23C is
- FIG. 28 is a circuit diagram illustrating an example of a configuration of a reading circuit.
- FIG. 29 is a configuration diagram of a conventional nonvolatile memory cell.
- FIG. 30 is a configuration diagram of a conventional nonvolatile memory cell array.
- FIG. 31 shows a model of a memory cell using a conventional unidirectional diode.
- nonvolatile memory devices As described above, as a nonvolatile memory device using a resistance change element, there are generally known nonvolatile memory devices having a cross-point structure in which memory cells called 1T1R type and memory cells called 1D1R type are arranged in a matrix. It has been.
- FIG. 29 is a configuration diagram of a conventional nonvolatile memory cell, and shows a 1D1R nonvolatile memory device using a variable resistance element having bidirectional resistance change characteristics as a memory cell (Patent Document 1). reference).
- a memory cell 1280 in which a variable resistance element 1260 having a variable resistor 1230 sandwiched between an upper electrode 1240 and a lower electrode 1250 and a non-linear element 1270 are connected in series is an intersection of a bit line 1210 and a word line 1220.
- 2 shows a memory cell array having a cross-point structure arranged at a portion where the cross-section is located.
- variable resistance element 1260 is a variable resistance element having a bidirectional resistance change characteristic in which a resistance value reversibly transitions between a low resistance state and a high resistance state depending on the polarity of an applied voltage.
- the non-linear element 1270 is constituted by, for example, a varistor for the purpose of reducing a so-called leakage current flowing through the non-selected cell.
- a memory cell array having a cross-point structure can have a large capacity because memory cells can be arranged at a wiring pitch and the memory cell arrays can be stacked three-dimensionally.
- FIG. 30 is a block diagram of a conventional nonvolatile memory cell array, and shows a non-linear element defect detection method in a 1D1R type memory cell using a unidirectional variable resistance element as a memory cell (Patent Document 2). reference).
- a memory cell in which a unidirectional variable resistance element and a unidirectional diode element having an anode and a cathode are connected in series are shown as bit lines BL1, BL2, BL3 and word lines WL, WL2, WL3. It is placed at the intersection.
- Patent Document 2 discloses that the bit line to which the defective diode element belongs is detected as a defective bit line.
- FIG. 31 shows a memory cell model using a conventional unidirectional diode (see Patent Document 2).
- the defect detection circuit 2053 includes a bit line power supply circuit 2054, a latch circuit 2531, and a switch circuit 2055, and is connected to a bit line connected to the bit line selection circuit 2024, and is in a standby state.
- the unit 2052 a defective bit line to which a defective diode element is connected is detected, and a relief method is disclosed.
- Patent Document 2 describes a method for detecting a defective bit line in a unidirectional memory cell array using a unidirectional diode element having an anode and a cathode. That is, it describes a method for detecting a defective bit line causing a leakage current abnormality by utilizing the fact that a current flows when a voltage is applied in the forward direction and no current flows when a voltage is applied in the reverse direction. .
- By setting all the bit lines to the Vdd potential, all the word lines to the Vss potential, and setting the diode elements to the reverse bias state current does not flow if all the memory cells are normal, but leakage current abnormality occurs. If there is a defective memory cell, a leak current flows from the bit line including the defective memory cell to the word line. By determining this leakage current, it is possible to detect a defective bit line causing a leakage current abnormality.
- a bidirectional memory cell array using a bidirectional current control element for example, an MSM diode or an MIM diode
- a defective memory cell in which a leakage current abnormality occurs cannot be detected.
- the defect detection circuit 2053 since the defect detection circuit 2053 is connected only to the bit line, it can detect a defective bit line causing a leakage current abnormality, but is connected to the defective bit line. Another problem is that it cannot be detected which memory cell is defective.
- Patent Document 2 discloses that a detected defective bit line is set in a floating state and then replaced with a redundant bit line.
- a bidirectional current control element leakage is caused even if a defective bit line is set in a floating state. Since a current flows, a leakage current abnormality cannot be prevented and a stable operation cannot be performed.
- the present invention provides a highly reliable variable resistance nonvolatile memory device capable of stable operation and a resistance variable nonvolatile memory device driving method.
- variable resistance nonvolatile memory device is connected in series with a variable resistance element whose resistance value reversibly changes according to an applied voltage pulse, and the variable resistance element.
- a variable resistance element whose resistance value reversibly changes according to an applied voltage pulse
- the variable resistance element Each of the three-dimensional intersections of the plurality of word lines and the plurality of bit lines each having a plurality of memory cells configured with a current control element through which a current that is considered to be conductive when the applied voltage exceeds a predetermined threshold voltage.
- a memory cell selection circuit for selecting one or more of the memory cells; and applying a voltage pulse to the selected memory cell, thereby selecting the selected memory cell.
- a first voltage higher than the threshold voltage or a second voltage lower than the threshold voltage is applied to the write circuit for rewriting the resistance value of the resistance change element of the recell and the current control element of the selected memory cell.
- the read circuit reads out the state of the selected memory cell by applying a voltage to the selected memory cell, and the write circuit uses the first low-resistance pulse as the voltage pulse. Or by applying a first high-resistance pulse to the selected memory cell, each of the resistance change elements of the selected memory cell among the plurality of memory cells is in a first low-resistance state, or The first high resistance state is applied, and the read circuit applies the first voltage to the selected memory cell to apply the first voltage to the selected memory cell.
- the reading circuit reads the resistance state of the resistance change element of the selected memory cell, if a current of a predetermined value or more flows in the selected memory cell,
- the selected memory cell is determined to be a defective memory cell having a short defect, and the write circuit is disposed on at least one of the same bit line as the defective memory cell and the same word line as the defective memory cell.
- the resistance change element of the other memory cell is set to a third high resistance state indicating a resistance value equal to or higher than the resistance value of the first high resistance state.
- the second high-resistance pulse is applied as described above.
- the resistance of the memory cells other than the defective memory cell arranged on the same bit line or word line as the defective memory cell is increased without performing processing such as increasing the resistance of the defective memory cell.
- a highly reliable variable resistance nonvolatile memory device can be realized.
- a defective memory cell having a current control element having a threshold voltage characteristic defect that is, a memory having a current control element having a short-circuit defect The cell can be identified and rescued.
- the write circuit sets the resistance change element of the defective memory cell to a third high resistance state indicating a resistance value equal to or higher than the resistance value of the first low resistance state.
- a third resistance-enhancing pulse having an absolute value of a voltage equal to or higher than the absolute value of the pulse voltage at which the resistance-changing element starts to increase in resistance is applied to the resistance-changing element.
- the defective memory cell itself can be remedied by increasing the resistance.
- a highly reliable variable resistance nonvolatile memory device can be realized.
- the read circuit applies the second voltage to the selected memory cell, and the selected memory cell is a defective memory cell having a short circuit when a current of the predetermined value or more flows. It is preferable to determine.
- the read circuit again detects whether a current of a predetermined value or more flows through the defective memory cell.
- the current greater than or equal to the predetermined value flows through the selected memory cell, it is preferable to determine that the resistance change element of the defective memory cell is not greater than or equal to the resistance value in the third high resistance state. .
- the write circuit includes the resistance change element of the defective memory cell. It is preferable that the third high-resistance pulse is repeatedly applied up to a resistance value of 3 in the high resistance state or a predetermined number of times.
- the write circuit includes the resistance change element of the defective memory cell. It is preferable that the fourth high-resistance pulse different from the third high-resistance pulse condition is repeatedly applied after the second time until the resistance value of the high-resistance state of 3 or more is reached or a predetermined number of times.
- the voltage value of the fourth high-resistance pulse is a voltage whose absolute value is larger than the voltage value of the third high-resistance pulse.
- the current value of the fourth high-resistance pulse is larger than the current value of the third high-resistance pulse.
- the pulse width of the fourth high-resistance pulse is larger than the pulse width of the third high-resistance pulse.
- the resistance of the defective memory cell can be reliably increased by changing the voltage value, current value, and pulse width conditions of the fourth high-resistance pulse.
- a highly reliable variable resistance nonvolatile memory device can be realized.
- the write circuit has the same bit line as that of the defective memory cell and the defective memory cell when the resistance value of the variable resistance element of the defective memory cell is lower than the resistance value of the third high resistance state.
- the second high resistance state having a resistance value higher than that of the first high resistance state is applied to a resistance change element of a memory cell other than the defective memory cell disposed at least on the same word line. It is preferable to apply the second resistance increasing pulse so that
- the second high-resistance pulse is set so that the other memory cells arranged in at least one of the bit line and the word line in which the defective memory cell is arranged are brought into the second high-resistance state. Since a voltage is applied, the defective memory cell can be remedied whether or not the defective memory cell can be increased in resistance. As a result, a highly reliable variable resistance nonvolatile memory device can be realized.
- a resistance value of the third high resistance state of the variable resistance element is equal to or higher than a resistance value of the first high resistance state.
- the resistance value of the variable resistance element in the third high resistance state is 10 times or more than the resistance value in the first high resistance state.
- the resistance value of the resistance change element of the defective memory cell in the second high resistance state is 10 times or more than the resistance value of the first high resistance state.
- the memory cell array replaces the defective memory cell when the main memory cell array having a plurality of the memory cells for main memory and at least one of the memory cells in the main memory cell array is a defective memory cell. And a redundant memory cell array including a plurality of redundant memory cells for use.
- variable resistance nonvolatile memory device includes a defective address storage circuit that stores the address information of the defective memory cell and the address information of the redundant memory cell in association with each other.
- the defective address storage circuit includes an address of at least one of a bit line and a word line having the defective memory cell, and a bit line corresponding to the bit line having the redundant memory cell replacing the defective memory cell. It is preferable that at least one address of a word line corresponding to the word line is stored in association with each other.
- the defective memory cell can be replaced with the redundant memory cell, the defective memory cell can be relieved and a highly reliable variable resistance nonvolatile memory device can be realized.
- variable resistance nonvolatile memory device includes a writing power source including a low resistance power source that supplies a low resistance voltage to the writing circuit and a high resistance power source that supplies a high resistance writing voltage to the writing circuit. It is preferable to provide.
- the write circuit having the low resistance power source and the high resistance power source is used to generate the first high resistance pulse and the write circuit that generates the first low resistance pulse, and thereby the second resistance increase.
- the pulse and the third resistance increasing pulse can be easily generated. Thereby, the defective memory cell can be relieved with the configuration of the existing variable resistance nonvolatile memory device.
- a resistance change type nonvolatile memory device driving method includes a resistance change element whose resistance value reversibly changes in accordance with an applied voltage pulse; A plurality of memory cells connected in series with the variable resistance element and configured by current control elements through which a current that is considered to be conductive when an applied voltage exceeds a predetermined threshold voltage; a plurality of word lines; A method of driving a variable resistance nonvolatile memory device including a memory cell array in which one of the plurality of memory cells is arranged at each of three-dimensional intersections with a bit line of the plurality of memory cells, wherein the plurality of memory cells are Each of the resistance change elements of the selected memory cell by applying the first low resistance pulse or the first high resistance pulse to the selected memory cell.
- a read circuit for applying a first voltage higher than the threshold voltage to the selected memory cell by a writing step for bringing the selected memory cell into a low resistance state or a first high resistance state.
- a read step of reading the resistance state of the variable resistance element, and when reading a resistance state of the selected memory cell, if a current of a predetermined value or more flows through the selected memory cell, the selected memory cell A failure detection step for determining that the memory cell has a short failure, and at least one of the same bit line as the defective memory cell and the same word line as the defective memory cell by the write circuit. With respect to other memory cells other than the defective memory cell that is arranged, the resistance change element of the other memory cell is moved forward. Applying a second high resistance pulse to the second high resistance state showing a resistance value of more than the resistance value of the first high resistance state, and a another memory cell high resistance step.
- a defective memory cell including a current control element having a threshold voltage characteristic defect that is, a current control element having a short defect It is possible to identify and relieve a memory cell provided with. Since the second high-resistance pulse voltage is applied so that the other memory cells arranged in at least one of the bit line and the word line in which the defective memory cell is arranged are in the second high-resistance state, Whether or not the defective memory cell can be increased in resistance, the defective memory cell can be relieved. As a result, a highly reliable variable resistance nonvolatile memory device can be realized.
- the write circuit causes the resistance change element of the defective memory cell to be in a third high resistance state indicating a resistance value equal to or higher than the resistance value in the first low resistance state.
- a defective memory cell in which a third high-resistance pulse having an absolute value of a voltage equal to or greater than an absolute value of a pulse voltage at which the variable resistance element starts increasing resistance is applied to the variable resistance element of the defective memory cell. High resistance step.
- the defective memory cell itself can be remedied by increasing the resistance.
- a highly reliable variable resistance nonvolatile memory device can be realized.
- the defect detection step when the read circuit applies a second voltage lower than the threshold voltage to the selected memory cell and a current of the predetermined value or more flows, the selected memory cell It is preferable to determine that the memory cell has a short circuit failure.
- the defect detection step is performed again to detect whether a current exceeding a predetermined value flows through the defective memory cell.
- the method further includes repeating the steps up to a predetermined number of times when the resistance change element of the defective memory cell is equal to or higher than a resistance value of a third high resistance state.
- the memory cell array includes a main memory cell array including a plurality of memory cells for main storage, and at least one of the memory cells in the main memory cell array is a defective memory cell.
- a redundant memory cell array including a plurality of redundant memory cells to be used in place of the defective memory cells, and the variable resistance nonvolatile memory device includes address information of the defective memory cells and the redundant memory cells. It is preferable that address information is associated and stored in a defective address storage circuit, and when the defective memory cell is accessed during memory operation, the redundant memory cell is accessed with reference to the defective address storage circuit.
- the address information of the defective memory cell is obtained. It is preferable that a repair step for storing in the defective address storage circuit is further included.
- the defective memory cell can be replaced with the redundant memory cell, the defective memory cell can be relieved and a highly reliable variable resistance nonvolatile memory device can be realized.
- nonvolatile memory device variable resistance nonvolatile memory device
- nonvolatile memory device variable resistance nonvolatile memory device
- FIG. 1 shows a preferred specific example of the present invention.
- the numerical values, shapes, materials, constituent elements, arrangement positions and connecting forms of the constituent elements, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention.
- constituent elements that are not described in the independent claims indicating the highest concept of the present invention are described as optional constituent elements that constitute a more preferable embodiment.
- FIG. 1 is an example of a configuration diagram of a memory cell according to the first embodiment of the present invention.
- a memory cell 10 shown in FIG. 1 includes a current control element 20 and a resistance change element 30 connected in series.
- the resistance change element 30 is connected to the current control element 20 via a contact 41, and the resistance change element 30 and the current control element 20 constitute a 1-bit 1D1R type memory cell 10.
- One terminal of the memory cell 10 is connected to the lower wiring 50 through the contact 40, and the other terminal of the memory cell 10 is connected to the upper wiring 51 through the contact 42.
- the memory cell 10 of FIG. 1 has a connection relationship in which the current control element 20 is on the bottom and the resistance change element 30 is on the top, but the connection relation is reversed and the current control element 20 is on the top.
- the connection relationship may be such that the resistance change element 30 faces downward.
- the current control element 20 includes a lower electrode (first electrode) 21, an upper electrode (second electrode) 23, and a current control layer 22 (semiconductor layer 22 or semiconductor electrode 22) sandwiched between the lower electrode 21 and the upper electrode 23. And an insulator layer 22).
- the lower electrode 21 and the semiconductor layer 22 are in physical and electrical contact to form a Schottky junction
- the upper electrode 23 and the semiconductor layer 22 are in physical and electrical contact to form a Schottky junction.
- it has bidirectional rectification characteristics.
- the insulator layer 22 is used instead of the semiconductor layer 22, the lower electrode 21, the insulator layer 22, and the upper electrode 23 constitute a tunnel diode and have bidirectional rectification characteristics.
- the current control element 20 is an element in which a voltage applied to both ends of the current control element 20 and a current flowing through both ends of the current control element 20 exhibit nonlinear characteristics.
- This is a bidirectional diode in which the direction of the flowing current changes depending on the polarity of the applied voltage. That is, the current control element 20 has a threshold voltage in each of the positive applied voltage region and the negative applied voltage region, and the absolute value of the voltage applied to both ends of the current control element 20 is less than or equal to the threshold voltage (VF).
- VF threshold voltage
- the resistance value of the current control element 20 increases, and the absolute value of the flowing current is such that almost no current flows, but the absolute value of the voltage applied to both ends of the current control element 20 is the threshold voltage (VF).
- the resistance value of the current control element 20 becomes extremely small, and the absolute value of the flowing current has a characteristic that increases nonlinearly. That is, when the absolute value of the voltage applied to both ends of the current control element 20 is equal to or lower than the threshold voltage (VF), only a small off current flows through the current control element 20, so that the current control element 20 is in the off state. become.
- the absolute value of the voltage applied to both ends of the current control element 20 is equal to or higher than the threshold voltage (VF)
- VF threshold voltage
- the current control element 20 has a function of a switch having an on state and an off state by a voltage applied to both ends of the current control element 20.
- the current control element 20 has a vertically symmetrical structure (that is, when the two electrodes are made of the same material and the current control layer 22 is homogeneous in the vertical direction)
- the voltage-current characteristics of the current control element 20 are positive and negative applied voltages. Shows almost point-symmetric characteristics. That is, the absolute values of the threshold voltages in the positive applied voltage region and the negative applied voltage region are substantially the same value.
- the current control element 20 in the present embodiment includes, for example, a lower electrode 21 made of tantalum nitride, a semiconductor layer 22 made of a nitrogen-deficient silicon nitride film having a nitrogen content smaller than that of Si 3 N 4 , Further, it is configured as an MSM (Metal-Semiconductor-Metal) diode having an upper electrode 23 made of tantalum nitride.
- the thickness of the semiconductor layer 22 can be set to 3 to 20 nm, for example.
- the silicon nitride film can be formed to have semiconductor characteristics by reducing the nitrogen content, and a diode configured as an MSM diode can be manufactured by a simple manufacturing process.
- a nitrogen-deficient silicon nitride film (SiN z : 0 ⁇ z ⁇ 0.85) can be formed, for example, by reactive sputtering in a nitrogen gas atmosphere using a Si target.
- the chamber pressure may be 0.1 Pa to 1 Pa and the Ar / N 2 flow rate may be 18 sccm / 2 sccm at room temperature.
- the current control element 20 in the present embodiment may be a MIM (Metal-Insulator-Metal) diode, PN diode, Schottky diode, or Zener diode.
- MIM Metal-Insulator-Metal
- an insulator layer 22 is provided between the lower electrode 21 and the upper electrode 23 instead of the semiconductor layer.
- the current control element 20 may be a unidirectional current control element in which current flows only in one direction.
- the resistance change element 30 includes a lower electrode (third electrode) 31, an upper electrode (fourth electrode) 34, and a resistance change layer 35 sandwiched between the lower electrode 31 and the upper electrode 34. .
- the resistance change layer 35 includes a first transition metal oxide layer 32 made of an oxygen-deficient transition metal oxide, and a transition metal having a lower degree of oxygen deficiency than the first transition metal oxide layer 32.
- a second transition metal oxide layer 33 made of an oxide is laminated.
- a first oxygen-deficient tantalum oxide layer hereinafter referred to as a first Ta oxide layer
- a second tantalum oxide layer hereinafter referred to as a second Ta oxidation layer.
- Material layer is laminated.
- the oxygen content of the second Ta oxide layer 33 is higher than the oxygen content of the first Ta oxide layer 32.
- the oxygen deficiency of the second Ta oxide layer 33 is less than the oxygen deficiency of the first Ta oxide layer 32.
- the degree of oxygen deficiency refers to the proportion of oxygen that is deficient with respect to the amount of oxygen constituting the oxide of the stoichiometric composition in each transition metal.
- the transition metal is tantalum (Ta)
- the stoichiometric oxide composition is Ta 2 O 5 , and thus can be expressed as TaO 2.5 .
- the degree of oxygen deficiency of TaO 2.5 is 0%.
- the oxygen content of Ta 2 O 5 is the ratio of oxygen to the total number of atoms (O / (Ta + O)), which is 71.4 atm%. Therefore, the oxygen-deficient tantalum oxide has an oxygen content greater than 0 and less than 71.4 atm%.
- the metal constituting the resistance change layer 35 may be a transition metal other than tantalum.
- the transition metal tantalum (Ta), titanium (Ti), hafnium (Hf), zirconium (Zr), niobium (Nb), tungsten (W), or the like can be used. Since transition metals can take a plurality of oxidation states, different resistance states can be realized by oxidation-reduction reactions.
- the composition of the first hafnium oxide layer 32 is HfO x
- x is 0.9 or more and 1.6 or less
- the second hafnium oxide layer 33 It has been confirmed that when the composition is HfO y and y is larger than the value of x, the resistance value of the resistance change layer 35 is stably changed at high speed.
- the thickness of the second hafnium oxide layer 33 is preferably 3 nm or more and 4 nm or less.
- x is 0.9 or more and 1.4 or less when the composition of the first zirconium oxide layer 32 is ZrO x , and the second zirconium oxide layer 33 It has been confirmed that when the composition is ZrO y and y is larger than the value of x, the resistance value of the resistance change layer 35 is stably changed at high speed.
- the thickness of the second zirconium oxide layer 33 is preferably 1 nm or more and 5 nm or less.
- the second transition metal oxide layer 33 has a lower degree of oxygen deficiency than the first transition metal oxide layer 32, that is, has a higher resistance.
- the standard electrode potential of the second transition metal is preferably smaller than the standard electrode potential of the first transition metal.
- the resistance change phenomenon is considered to occur due to the oxidation-reduction reaction occurring in a minute filament (conductive path) formed in the second transition metal oxide layer 33 having a high resistance, resulting in a change in resistance value. is there.
- oxygen-deficient tantalum oxide for the first transition metal oxide layer 32 and titanium oxide (TiO 2 ) for the second transition metal oxide layer 33 stable resistance change operation Is obtained.
- the standard electrode potential represents a characteristic that the greater the value, the less likely it is to oxidize.
- the resistance change phenomenon in the resistance change film having the laminated structure of each material described above is caused by an oxidation-reduction reaction occurring in a minute filament formed in the second transition metal oxide layer 33 having a high resistance. Changes and is thought to occur. That is, when a positive voltage is applied to the electrode 34 on the second transition metal oxide layer 33 side with respect to the lower electrode 31, oxygen ions in the resistance change film 35 are converted into the second transition metal oxide layer 33. It is considered that the resistance of the microfilament is increased by causing an oxidation reaction in the microfilament formed in the second transition metal oxide layer 33 by being drawn to the side.
- the upper electrode 34 connected to the second transition metal oxide layer 33 having a lower oxygen deficiency constitutes the second transition metal oxide layer 33 such as platinum (Pt) or iridium (Ir).
- the transition metal and the material constituting the lower electrode 31 are made of a material having a higher standard electrode potential.
- the lower electrode 31 is made of an electrode material whose main component is a material having a lower standard electrode potential than the upper electrode 34 (for example, TaN (tantalum nitride)). Specifically, when tantalum oxide is used for the first transition metal oxide layer 32 and the second transition metal oxide layer 33, the lower electrode 31 is made of TaN, W, Ni, Ta, Ti, Al, etc.
- the upper electrode 34 is preferably selected from the group consisting of Pt, Ir, Pd, Ag, Cu, Au, and the like.
- a voltage satisfying a predetermined condition is applied between the lower electrode 31 and the upper electrode 34 by an external power source.
- the current control element 20 in FIG. 1 and the resistance change element 30 may be connected in the reverse relationship, and the first transition metal oxide layer 32 and the second transition metal oxide layer may be connected.
- the upper and lower connection relationships with the upper electrode 34 may be reversed, and the upper and lower connection relationships between the lower electrode 31 and the upper electrode 34 may be reversed.
- FIG. 2 is an equivalent circuit diagram of the memory cell 10 in the present embodiment shown in FIG.
- the memory cell 100 is an equivalent circuit diagram in which a current control element 101 and a resistance change element 102 are connected in series.
- One terminal T1 of the memory cell 100 is connected to the current control element 101, and the memory cell
- the other terminal T 2 of 100 is connected to the resistance change element 102.
- the terminal T1 is connected to the lower wiring 50, and the terminal T2 is connected to the upper wiring 51.
- Vdi is a voltage applied across the current control element 101
- Vre is a voltage applied across the resistance change element 102.
- the current control element 101 when the absolute value of the voltage Vdi applied to the current control element 101 exceeds the threshold voltage (VF), the current control element 101 is turned on, and the memory cell current Ice flows through the memory cell 100.
- the absolute value of the voltage Vdi applied to the current control element 101 is equal to or lower than the threshold voltage (VF)
- the current control element 101 is turned off, and only the off current Ioff that is a minute current flows through the memory cell 100. Absent. That is, the current control element 101 is turned on or off depending on the threshold voltage (VF) applied to the memory cell 100, whereby the memory cell 100 can be controlled to be in a selected state or a non-selected state. .
- FIG. 3A is a diagram showing voltage-current characteristics of a normal memory cell 10 according to the present embodiment.
- the polarity at which the upper wiring 51 is higher than the lower wiring 50 is a positive voltage
- the polarity at which the lower wiring 50 is higher than the upper wiring 51 is a negative voltage.
- a voltage is applied across the memory cell 10. The measured value of the relationship between the voltage and the current when the voltage is applied is shown.
- the measured data shown in FIG. 3A indicates that the voltage of the lower wiring 50 is the first low resistance write voltage (first low resistance reduction) with respect to the memory cell 10 having the structure of FIG. Pulse) Vwl1 (in FIG. 3A, Vwl1 indicates an absolute value, and when the potential of the upper wiring 51 is lower than the potential of the lower wiring 50 by Vwl1), the first low resistance state (point B) is obtained.
- the voltage of the upper wiring 51 becomes the high resistance start voltage Vwh0 with respect to the voltage of the lower wiring 50, the bidirectional resistance change starts from the low resistance state to the high resistance state (point D). The characteristics are shown.
- 3A indicates that the first low resistance write voltage Vwl1 and the high resistance start voltage Vwh0 are in a voltage and current relationship that is substantially symmetrical with respect to the origin of the actual measurement data.
- a first high-resistance write voltage (first high-resistance pulse) Vwh1 higher than the high-resistance start voltage Vwh0 is applied, the first high-resistance state (D ′ point) is obtained.
- the resistance value at the point D ′ is larger than the resistance value at the point D.
- the current control element 20 of the memory cell 10 is an element in which the current flowing by the applied voltage has a non-linear characteristic. Therefore, the absolute value of the voltage applied to the current control element 20 is the threshold voltage (VF) of the current control element 20. In the case of the following, almost no current flows, the current control element 20 is regarded as an off state, and almost no current flows in the memory cell 10.
- the threshold voltage (VF) of the current control element 20 is a maximum voltage applied to the current control element 20 when only a current (maximum off current) that can be regarded as an off state flows.
- the maximum off current of the current control element 20 is a current value that is smaller than at least the maximum current IHR that flows when the resistance change element 30 of the memory cell 10 is in the high resistance state. In one example of the present embodiment, IHR is Since it is 10 ⁇ A, the maximum off-current of the current control element 20 may be less than 10 ⁇ A.
- the points A and C correspond to the threshold voltage (VF) of the current control element 20 and the total voltage applied to the resistance change element 30, and a plurality of memory cells 10 are arranged in an array.
- VF threshold voltage
- a voltage exceeding the voltage band from the point A to the point C is applied to the selected memory cell (selected memory cell) 10, and the memory cell not selected (unselected memory cell) ) Is configured such that a voltage is applied to the voltage range between the point A and the point C, thereby suppressing the leakage current to the non-selected cells and causing the current to flow through the selected memory cell 10.
- the resistance state of the memory cell 10 can be determined by applying the read voltage Vread shown in FIG. 3A to the memory cell 10 and determining the current flowing at that time. That is, in the case of the characteristics shown in FIG. 3A, when the resistance change element 30 of the memory cell 10 is in the first low resistance state, for example, when a voltage of 4.0 V is applied as the read voltage Vread, A current of about 55 ⁇ A flows. However, when the resistance change element 30 of the memory cell 10 is in the first high resistance state, a current of about 10 ⁇ A flows through the memory cell 10 when the read voltage Vread (4.0 V) is applied. By determining this current value, the state of the memory cell 10 can be determined.
- the read voltage Vread is applied to the memory cell 10 and the memory cell current flowing at that time is determined.
- the resistance state of the cell 10 can be determined.
- the current control element 20 of the memory cell 10 is destroyed and a short circuit is defective, an excessive current flows through the memory cell 10.
- the open is defective, almost no current flows and the resistance state of the memory cell 10 cannot be determined. Therefore, it is necessary to detect a defective memory cell (defective memory cell) and prevent an abnormal current from flowing through the defective memory cell.
- FIG. 3B schematically shows a part of the voltage resistance characteristic of the variable resistance element 30 shown in FIG.
- the horizontal axis is the voltage value applied between the lower electrode 31 and the upper electrode 34 of the resistance change element 30 with reference to the lower electrode, and the vertical axis is the resistance value of the resistance change element 30.
- the resistance change element 30 When the voltage applied to the resistance change element 30 is gradually increased from the state O in the low resistance state, the resistance change element 30 starts to increase in resistance at the voltage Vwh0 (A0). When the voltage applied to the resistance change element 30 is further increased, the resistance change element 30 enters the high resistance state B1 (limit high resistance state) having the maximum resistance value at the voltage Vwh4. Furthermore, even if the voltage applied to the resistance change element 30 is increased, the resistance value of the resistance change element 30 does not change (C1). Even if the voltage applied to the resistance change element 30 from C1 is gradually decreased, the resistance value does not decrease and the limit resistance state is maintained.
- the voltage / resistance characteristics of the resistance change element 30 from state A0 to state B1 have a predetermined slope (actually nonlinear).
- the corresponding first high resistance write voltage Vwh1 is applied.
- the corresponding third high resistance write voltage Vwh3 is applied.
- the corresponding second high resistance write voltage Vwh2 is applied.
- a limit high resistance state can be obtained.
- FIG. 4 is a diagram illustrating the voltage-current characteristics of the memory cell 10 in which the current control element 20 has normal characteristics and the memory cell 10 in which the current control element 20 has defective characteristics (short circuit failure) in the present embodiment. is there.
- the polarity at which the upper wiring 51 is higher than the lower wiring 50 is a positive voltage.
- the positive voltage and current applied to the normal memory cell 10 having the first low resistance state are represented by the characteristic (1).
- the absolute value of the voltage applied to the memory cell 10 is about 2.6 V or less, almost no current flows through the memory cell 10, but when it exceeds 2.6 V, the current flows through the memory cell 10. The flowing current increases non-linearly with increasing applied voltage.
- the memory cell 10 having a defective characteristic has a linear characteristic in terms of voltage and current characteristics, as indicated by characteristic (2) in FIG. .
- a voltage equal to or lower than the threshold voltage VF at which the current control element 20 is turned off is applied to both ends of the memory cell.
- a voltage of 2.6 V when a normal characteristic such as characteristic (1) is exhibited, almost no current flows as indicated by point E, but a short defect characteristic such as characteristic (2) is exhibited.
- a voltage Vtest1 2.6V in this embodiment
- a voltage Vtest1 for detecting a defect is applied to the memory cell 10 so that a voltage equal to or lower than the threshold voltage is applied to the current control element 20 of the memory cell 10. It is possible to determine whether or not a memory cell is defective by detecting a difference in current that sometimes flows through the memory cell 10.
- Characteristic (3) and characteristic (4) in FIG. 4 are voltage-current characteristics when the threshold voltage of the current control element 20 is smaller than the threshold voltage VF of the current control element 20 of the normal memory cell 10, respectively.
- the current control element 20 in the case of the characteristic (3) and the characteristic (4) has a defective characteristic, and is indicated by the G point and the H point.
- currents of about 100 ⁇ A and about 25 ⁇ A flow in the memory cells 10 respectively.
- the memory cell 10 having normal characteristics such as the characteristic (1) almost no current flows as indicated by the point E. Therefore, by detecting this difference in current, the characteristics of the defective memory cell are determined. You can investigate.
- the memory cell 10 has a bad characteristic (open failure), even if the read voltage Vread is applied to the memory cell 10, almost no current flows through the memory cell 10.
- the resistance value of the resistance change element 30 of the memory cell 10 is in the first low resistance state as shown in the characteristic (1), and the current control element 20 is normal.
- a memory cell current of about 5 ⁇ A flows as shown by the point K, but in the case of the memory cell 10 having an open defect, the current is about 1 ⁇ A or less (not shown in the figure). ) Only flows. That is, after the resistance change element 30 of the memory cell 10 is set to the first low resistance state, the read voltage Vread (3.0 V in the present embodiment) is applied to the memory cell 10, thereby Open failure can be determined.
- FIG. 5 shows a configuration diagram of the variable resistance nonvolatile memory device 200 according to the first embodiment.
- the variable resistance nonvolatile memory device 200 according to the present embodiment includes a memory main body 201 on a substrate.
- the memory body 201 includes a memory cell array 202, a word line selection circuit 203, a bit line selection circuit 204, a write circuit 205 for writing data, a read circuit 206 for reading data, and a data And a signal input / output circuit 207.
- the read circuit 206 includes a sense amplifier 300, a bit line control voltage switching circuit 400, and a bit line control voltage generation circuit 500 that generates a bit line control voltage. It is connected to a data signal input / output circuit 207 for outputting.
- the variable resistance nonvolatile memory device 200 includes an address signal input circuit 208 that receives address information input from the outside of the variable resistance nonvolatile memory device 200 and an input from the outside of the variable resistance nonvolatile memory device 200. And a control circuit 209 for receiving a control signal to be transmitted.
- a low-resistance power source 211 and a high-resistance power source 212 are provided as the write power source 210.
- the output VL of the low-resistance power source 211 and the output VH of the high-resistance power source 212 are the memory main body. This is supplied to the writing circuit 205 of the unit 201.
- the variable resistance nonvolatile memory device 200 includes a defective address storage circuit 213 that stores a defective address detected by the read circuit 206 and an address comparison circuit 214 that performs address comparison.
- variable resistance nonvolatile memory device 200 determines, as operation modes, a write mode for writing data into the memory cell, a normal read mode for reading data from the memory cell, and the characteristics of the memory cell.
- a cell characteristic determination mode and a repair mode in which a memory cell having a short circuit failure is set to a third high resistance state having a resistance value higher than that of the first low resistance state and replaced with a normal memory cell are provided.
- the memory cell array 202 includes a main memory cell array 600 in which a plurality of memory cells 100 shown in FIG. 2 are arranged in a matrix in the row direction and the column direction, and a plurality of memory cells 100 shown in FIG.
- the redundant memory cell array 610 is arranged.
- the redundant memory cell array 610 is configured by arranging the same number of memory cells 100 in each row of the main memory cell array 600. As an example, in the redundant memory cell array 610 in FIG. 5, one memory cell 100 is arranged in each row of the main memory cell array 600 to form a redundant memory cell array 610 in one column.
- the memory cell array 202 includes a plurality of word lines WL1, WL2, WL3,... And a plurality of bit lines BL1, BL2, BL3,. Are provided with at least one redundant bit line BLR1,... Arranged in parallel with the bit lines BL1, BL2, BL3,.
- the plurality of word lines WL1, WL2, WL3,... are arranged in parallel to each other in the same plane (in the first plane) parallel to the main surface of the substrate.
- the plurality of bit lines BL1, BL2, BL3,... are arranged in parallel to each other in the same plane parallel to the first plane (in a second plane parallel to the first plane).
- the redundant bit lines BLR1,... are arranged in parallel with the bit lines BL1, BL2, BL3,.
- the first plane and the second plane are arranged in parallel, and the plurality of word lines WL1, WL2, WL3,... And the plurality of bit lines BL1, BL2, BL3,.
- the memory cells M11, M12, M13, M21, M22 are located at three-dimensionally intersecting positions of the word lines WL1, WL2, WL3,... And the bit lines BL1, BL2, BL3,. , M23, M31, M32, M33,... (Hereinafter referred to as “memory cells M11, M12, M13,...”) Are arranged, and in the redundant memory cell array 610, word lines WL1, WL2, Redundant memory cells MB1, MB2, MB3,... Are arranged at the positions where WL3,... And the redundant bit lines BLR1,. That is, the plurality of word lines WL1, WL2, WL3,... Are arranged in common to the main memory cell array 600 and the redundant memory cell array 610.
- Memory cells M11, M12, M13,... Are current control elements D11, D12, D13, D21, D22, D23, D31, D32, D33, (hereinafter referred to as “current control elements D11, D12, D13,. ..)), And resistance change elements R11, R12, R13, R21, R22, R23, R31, R32, R33,... Connected in series with the current control elements D11, D12, D13,. (Hereinafter referred to as “resistance change elements R11, R12, R13,...”).
- the redundancy memory cells MB1, MB2, MB3,... Have resistance changes connected in series with the current control elements DB1, DB2, DB3,... And the current control elements DB1, DB2, DB3,. It comprises elements RB1, RB2, RB3,.
- one terminal of the resistance change elements R11, R21, R31,... In the main memory cell array 600 is connected to the current control elements D11, D21, D31,.
- the other terminal is connected to the bit line BL1, and one terminal of the resistance change elements R12, R22, R32,... Is connected to the current control elements D12, D22, D32,.
- the other terminal is connected to the bit line BL2, and one terminal of the resistance change elements R13, R23, R33,... Is connected to the current control elements D13, D23, D33,.
- One terminal is connected to the bit line BL3.
- one terminal of the resistance change elements RB1, RB2, RB3,... In the redundant memory cell array 610 is connected to the current control elements DB1, DB2, DB3, and the other terminal is the redundant bit line.
- BLR1,... Are connected.
- one terminal of the current control elements DB1, DB2, DB3,... Is connected to the resistance change elements RB1, RB2, RB3,...
- the other terminal is the word lines WL1, WL2, WL3. , ... are connected.
- a resistance change element is connected to the bit line side and a current control element is connected to the word line side.
- a current control element is connected to the bit line side and resistance change is made to the word line side. Elements may be connected.
- at least one redundant bit line BLR1,... Of the redundant memory cell array is required, and a plurality of redundant bit lines BLR1,... Are mounted according to the number of memory cells 100 arranged in the redundant memory cell array. It doesn't matter.
- the word line selection circuit 203 receives the row address information output from the address signal input circuit 208, and a word selected from the plurality of word lines WL1, WL2, WL3,... According to the row address information. Whether a voltage supplied from the write circuit 205 is applied to the line, and a predetermined unselected row application voltage (a voltage of Vss to Vwl or a voltage of Vss to Vwh) is applied to the unselected word line Or a high impedance (Hi-Z) state.
- a predetermined unselected row application voltage a voltage of Vss to Vwl or a voltage of Vss to Vwh
- the bit line selection circuit 204 receives the column address information output from the address signal input circuit 208 and the address match determination signal from the address comparison circuit 214, and uses the column address information and the address match determination signal as the column address information. Accordingly, of the plurality of bit lines BL1, BL2, BL3,... And the redundant bit line BLR1,..., The voltage supplied from the write circuit 205 to the selected bit line or supplied from the read circuit 206. In addition, a predetermined unselected column application voltage (a voltage of Vss to Vwl, a voltage of Vss to Vwh, or a voltage of Vss to Vbl) is applied to unselected bit lines. Or a high impedance (Hi-Z) state.
- a predetermined unselected column application voltage a voltage of Vss to Vwl, a voltage of Vss to Vwh, or a voltage of Vss to Vbl
- word line selection circuit 203 and the bit line selection circuit 204 correspond to the memory selection circuit in the present invention.
- the write circuit 205 receives the write signal output from the control circuit 209 and applies a write voltage to the memory cell selected by the word line selection circuit 203 and the bit line selection circuit 204, so that the memory cell The state can be rewritten.
- variable resistance nonvolatile memory device 200 when the first low resistance write voltage Vwl1 having a high potential is applied to WL1 with respect to BL1, for example, to a normal memory cell M11 in the write mode.
- the resistance change element R11 changes to the first low resistance state.
- a first high resistance write voltage Vwh1 that is a high potential is applied to BL1 with respect to WL1 with respect to a normal memory cell M11, the resistance change element R11 changes to the first high resistance state.
- the read circuit 206 applies a read voltage Vblr between the word line selected by the word line selection circuit 203 and the bit line selected by the bit line selection circuit 204 in the normal read mode, and flows in the memory cell.
- the state stored in the memory cell can be read by determining the cell current with the sense amplifier 300.
- a cell characteristic determination voltage Vblt is applied between the word line selected by the word line selection circuit 203 and the bit line selected by the bit line selection circuit 204, and flows to the memory cell. By determining the memory cell current with the sense amplifier 300, the cell characteristics of the memory cell can be determined.
- bit line control voltage generation circuit 500 sets the potential of the selected bit line selected by the bit line selection circuit 204 according to the respective modes in the normal read mode and the cell characteristic determination mode. A voltage Vcr and a cell characteristic determination clamp voltage Vct are generated.
- the bit line control voltage switching circuit 400 supplies the read clamp voltage Vcr output from the bit line control voltage generation circuit 500 to the sense amplifier 300 in the normal read mode, and generates the bit line control voltage in the cell characteristic determination mode.
- the voltage supplied to the sense amplifier can be switched according to the normal read mode and the cell characteristic determination mode so that the cell characteristic determination clamp voltage Vct output from the circuit 500 is supplied to the sense amplifier 300.
- the sense amplifier 300 uses the read clamp voltage Vcr or the cell characteristic determination clamp voltage Vct supplied from the bit line control voltage switching circuit 400 in accordance with the normal read mode and the cell characteristic determination mode, respectively.
- Vblr or cell characteristic determination voltage Vblt is set.
- the sense amplifier 300 determines whether the state of the resistance change element of the memory cell is the first low resistance state based on the memory cell current read through the bit line selection circuit 204. The high resistance state is read and the result is output to the outside via the data signal input / output circuit 207.
- the memory cell current read out via the bit line selection circuit 204 is read out as to whether the memory cell is in a normal state or a defective state, and the result is a data signal input / output. It is output to the outside via the circuit 207 and also output to the defective address storage circuit 213.
- the control circuit 209 In the write mode, the control circuit 209 outputs a signal instructing application of a write voltage to the write circuit 205 in accordance with the input data Din input from the data signal input / output circuit 207, and in the normal read mode, A signal instructing application of the read voltage is output to the read circuit 206, and in the cell characteristic determination mode, a signal instructing application of a cell determination voltage for determining the characteristics of the memory cell is output to the read circuit 206.
- the relief mode a signal instructing application of a write voltage for setting the memory cell in the third high resistance state having a resistance value higher than that in the first low resistance state is output to the write circuit 205 to perform the relief processing. The signal is output to the memory body 201.
- the address signal input circuit 208 receives externally input address information, outputs row address information to the word line selection circuit 203 based on this address information, and outputs column address information to the bit line selection circuit 204.
- the address information is information indicating the address of a specific memory cell in the memory cell array 202
- the column address information is address information indicating a specific column in the memory cell array 202
- the row address information is specific in the memory cell array 202. This is address information indicating the line.
- the address signal input circuit 208 outputs address information (column address information, row address information) to the defective address storage circuit 213 and the address comparison circuit 214.
- the defective address storage circuit 213 stores column address information input from the address signal input circuit 208 as a defective address when the selected memory is determined to be defective in the cell characteristic determination mode of the read circuit 206.
- the defective address storage circuit 213 has an address conversion table 213a as shown in FIG. 6A.
- FIG. 6A is a diagram illustrating an example of an address conversion table provided in the defective address storage circuit 213.
- FIG. 6A shows a case where defective memory cells are repaired in units of bit lines.
- the address conversion table 213a stores a defective bit line having a defective memory cell and a redundant bit line having a replacement redundant memory cell in association with each other.
- a defective memory cell may be replaced not only in units of bit lines but also in units of word lines or memory cells.
- the memory cell When repairing a defective memory cell in units of word lines or memory cells, a defective word line or defective memory cell having a defective memory cell, and a replacement redundant word line or redundant to replace the defective word line or defective memory cell
- the memory cell may be associated with and stored in the address conversion table 213a.
- the address comparison circuit 214 compares the column address information input from the address signal input circuit 208 with the defective bit line address stored in the defective address storage circuit 213, and addresses match whether they match.
- the determination signal is output to the bit line selection circuit 204.
- the repair mode described later is shown in FIG. 6A.
- a defective bit line for example, BL3
- a redundant bit line for example, BLR1
- the write power supply 210 includes a low resistance power supply 211 and a high resistance power supply 212, and outputs thereof are respectively supplied to the write circuit 205 of the memory main body 201.
- FIG. 6B is a circuit diagram showing an example of the configuration of the readout circuit 206 in FIG.
- the read circuit 206 includes a sense amplifier 300, a bit line control voltage switching circuit 400, and a bit line control voltage generation circuit 500.
- the sense amplifier 300 includes a comparison circuit 310, a current mirror circuit 320, and a bit line voltage control transistor N1.
- the current mirror circuit 320 includes a PMOS transistor P1, a PMOS transistor P2, a PMOS transistor P3, and a constant current circuit 330.
- the source terminals of the PMOS transistor P1, the PMOS transistor P2, and the PMOS transistor P3 of the current mirror circuit 320 are connected to the power supply, the gate terminals are connected to each other, the drain terminal of the PMOS transistor P1, and the constant current It is connected to one terminal of the circuit 330.
- the other terminal of the constant current circuit 330 is connected to the ground potential.
- the drain terminal of the PMOS transistor P2 is connected to one input terminal (for example, + terminal) of the comparison circuit 310 and the drain terminal of the bit line voltage control transistor N1.
- the drain terminal of the PMOS transistor P3 is connected to the bit line control voltage generation circuit 500.
- the gate terminal of the bit line voltage control transistor N1 is connected to the output terminal of the bit line control voltage switching circuit 400, and the source terminal of the bit line voltage control transistor N1 is connected to the bit line selection circuit via the terminal BLIN of the read circuit 206. 204 is connected.
- the other terminal (eg, ⁇ terminal) of the comparison circuit 310 is connected to the terminal SAREF of the readout circuit 206, and the output terminal of the comparison circuit 310 is connected to the data signal input / output circuit via the output terminal SAOUT of the readout circuit 206. It is connected to 207 and outputs data to the outside.
- the clamp voltage (Vcr or Vct) output from the bit line control voltage switching circuit 400 is applied to the gate terminal of the bit line voltage control transistor N1, the source terminal (terminal BLIN) of the bit line voltage control transistor N1.
- the clamp voltage (Vcr or Vct) output from the bit line control voltage switching circuit 400 is applied to the gate terminal of the bit line voltage control transistor N1, the source terminal (terminal BLIN) of the bit line voltage control transistor N1.
- the potential of the drain terminal (terminal SAIN) of the bit line voltage control transistor N1 is applied to the + terminal of the comparison circuit 310, and the reference voltage Vref is applied to the ⁇ terminal of the comparison circuit 310 from the terminal SAREF.
- the comparison circuit 310 compares the reference voltage Vref applied to the ⁇ terminal and the potential of the terminal SAIN applied to the + terminal.
- the comparison circuit 310 outputs an L potential to the output terminal if the potential of the terminal SAIN is lower than the potential of the terminal SAREF, and outputs an H potential if the potential of the terminal SAIN is higher than the potential of the terminal SAREF.
- the state of the memory cell 10 is output to the outside via the data signal input / output circuit 207.
- the potential at the terminal SAIN changes from the H potential to the L potential quickly. If the current flowing through the memory cell 10 is small, the potential at the terminal SAIN is changed from the H potential to the L potential. Transition slowly or remain at H potential.
- the potential of the terminal SAIN and the terminal SAREF is compared by the comparison circuit 310 at a predetermined output sense timing, if the potential of the terminal SAIN is lower, the L potential is output to the output terminal SAOUT, and the current flowing through the memory cell 10 is small. Is determined. Similarly, if the potential of the terminal SAIN is higher, the H potential is output to the output terminal SAOUT, and it is determined that the current flowing through the memory cell 10 is large.
- the reference voltage Vref applied from the terminal SAREF may be generated inside the variable resistance nonvolatile memory device 200 or may be applied from an external terminal. .
- the voltage applied to the gate terminal of the bit line voltage control transistor N1 is generated by the bit line control voltage generation circuit 500.
- the bit line control voltage generation circuit 500 includes a reference current control element RD10, an NMOS transistor N10, and a reference resistance change element RE10.
- One terminal of the reference current control element RD10 is connected to the drain terminal of the PMOS transistor P3 of the current mirror circuit 320 and is also connected to the output terminal OUT1 of the bit line control voltage generation circuit 500 to output the read clamp voltage Vcr. Output more.
- the other terminal of the reference current control element RD10 is connected to the drain terminal and the gate terminal of the NMOS transistor N10 and to the output terminal OUT2, and outputs the cell characteristic determination clamp voltage Vct from the output terminal.
- the source terminal of the NMOS transistor N10 is connected to one terminal of the reference resistance change element RE10, and the other terminal of the reference resistance change element RE10 is grounded.
- the reference current control element RD10 and the reference resistance change element RE10 are current control elements D11, D12, D13,... And resistance change elements R11, R12, R13,. Consists of the same elements.
- the reference resistance change element RE10 can be set to a high resistance state or a low resistance state similarly to the resistance change element included in the memory cell array 202, and at least a memory cell in the low resistance state is set. In order to detect, it is desirable to set the resistance value of the reference resistance change element RE10 to an average high resistance state resistance value of the memory cell array 202.
- the read clamp voltage Vcr output from the output terminal OUT1 of the bit line control voltage generation circuit 500 and the cell characteristic determination clamp voltage Vct output from the output terminal OUT2 are voltages applied to the reference resistance change element RE10 by Vre (resistance Are substantially the same applied voltage as the change elements R11, R12, R13,...,
- the threshold voltage of the NMOS transistor N10 is Vtn (substantially the same threshold voltage as the NMOS transistor N1), and the threshold voltage of the reference current control element RD10 is VF (current control) Assuming that the threshold voltages are substantially the same as those of the elements D11, D12, D13,.
- Vcr Vre + Vtn + VF (Formula 1)
- Vct Vre + Vtn (Formula 2)
- the NMOS transistor N10 is configured with the same transistor size as the bit line voltage control transistor N1 of the sense amplifier 300, and the PMOS transistor P3 of the sense amplifier 300 is configured with the same transistor size as the PMOS transistor P2.
- the NMOS transistor N10 and the PMOS transistor P3 may be reduced in size while maintaining the size ratio of the control transistor N1 and the PMOS transistor P2.
- the threshold voltage Vtn of the bit line voltage control transistor N1 is simulated based on the voltage from the output terminal OUT1 to the terminal BLIN of the read circuit 206 (that is, the bit line voltage when the memory cell is read). Higher voltage is output. Further, a voltage lower than the output terminal OUT1 by the threshold voltage VF ′ of the reference current control element RD10 (may be the same as the threshold voltage VF of the current control element of the memory cell) is output from the output terminal OUT2. Note that voltages output from the output terminal OUT1 and the output terminal OUT2 correspond to the first output and the second output in this embodiment, respectively.
- the bit line control voltage switching circuit 400 is composed of switches SW1 and SW2. One terminal of the switch SW1 of the bit line control voltage switching circuit 400 is connected to the output terminal OUT1 of the bit line control voltage generation circuit 500, and one terminal of the switch SW2 is the output terminal OUT2 of the bit line control voltage generation circuit 500. Connected with. The other terminals of the switches SW1 and SW2 are connected to each other and connected to the gate terminal of the bit line voltage control transistor N1 of the sense amplifier 300. In the normal read mode of the sense amplifier 300, the bit line control voltage switching circuit 400 sets the read clamp voltage Vcr of the output terminal OUT1 of the bit line control voltage generation circuit 500 to a transistor by turning SW1 on and SW2 off. Output to the gate terminal of N1. In the cell characteristic determination mode, SW1 is turned off and SW2 is turned on to output the cell characteristic determination clamp voltage Vct of the output terminal OUT2 of the bit line control voltage generation circuit 500 to the gate terminal of the transistor N1.
- the voltage applied to the bit line does not exceed a voltage lower than the voltage applied to the gate terminal of the bit line voltage control transistor N1 by the threshold voltage Vtn of the transistor N1.
- the read voltage Vblr applied to the line and the cell characteristic determination voltage Vblt applied to the bit line in the cell characteristic determination mode can be expressed by (Expression 3) and (Expression 4), respectively.
- FIG. 7 is a circuit diagram for explaining a current path in the main memory cell array 600.
- FIG. 8 is an equivalent circuit diagram of FIG.
- the reading of the resistance state of the memory cell M22 will be described as an example of the reading of the resistance state of the memory cell when all the memory cells of the main memory cell array 601 in FIG. 7 are normal memory cells.
- a Vss potential is applied to the word line WL2 selected by the word line selection circuit 203, and the bit line BL2 selected by the bit line selection circuit 204 is given by (Equation 3) And the non-selected bit lines BL1 and BL3 and the non-selected word lines WL1 and WL3 are set to a high impedance state (Hi-Z) to select the memory cell M22.
- the non-selected bit lines BL1 and BL3 and the non-selected word lines WL1 and WL3 are in a high impedance state, but a voltage equal to or lower than the voltage applied between the selected bit line BL2 and the selected word line WL2. It may be set to a value.
- the unselected memory cells M11, M12, M13, M21, M23, M31, M32, and M33 in the unselected memory cell array 602 are connected in series in three stages. This is equivalent to the memory cell being connected in parallel to the memory cell M22. That is, the total unselected memory cell current ⁇ Inselr flowing in the unselected memory cell array 602 is a plurality of currents via at least three or more stages of unselected memory cells in the shortest current path from the selected bit line BL2 to the selected word line WL2. Current flows through the path. A plurality of non-selected memory cells are connected in parallel to each stage.
- the first stage is a non-selected memory cell M12, M32 connected to the selected bit line BL2, and the second stage is a non-selected bit line BL1 or BL3.
- the non-selected memory cells M11, M13, M31, M33 connected to the non-selected word line WL1 or WL3 are connected to the non-selected memory cells M21, M23 connected to the selected word line WL2 in the third stage. Yes.
- the voltage applied to the non-selected memory cells is divided by the impedance ratio of the non-selected memory cells M12, M32, M21, and M23 arranged in the first and second stages.
- a voltage of about 1 ⁇ 2 or less of the read voltage Vblr applied between the selected bit line BL2 and the selected word line WL2 is 1st stage Applied to the non-selected memory cells M12, M32, M21 and M23 arranged in the second stage.
- non-selected memory cells M11, M12, M13, M21, M23, M31, M32, and M33 are normal memory cells indicated by the characteristic (1) in FIG. 4, the non-selected memory cells M11, M12, respectively. , M13, M21, M23, M31, M32, and M33 current control elements D11, D12, D13, D21, D23, D31, D32, and D33 are turned off because a voltage equal to or lower than the threshold voltage VF is applied. Therefore, the sum ⁇ Insel of the unselected cell currents flowing in each of the unselected memory cells M11, M12, M13, M21, M23, M31, M32, and M33 flows only an off current smaller than 1 ⁇ A.
- the selected bit line current Iblr that flows in the selected bit line BL2 that flows when the resistance state of the memory cell M22 is read is the sum of the selected cell current Iselr and the all unselected cell current ⁇ Inselr as shown in (Equation 5).
- the selected bit line current Iblr flowing through the selected bit line BL2 can be approximated as in (Equation 6). Therefore, the memory cell current of the selected memory cell M22 can be read via the selected bit line BL2, and it can be read whether the resistance change element R22 of the selected memory cell M22 is in the first high resistance state or the low resistance state. .
- Iblr Iselr + ⁇ Inselr (Formula 5) Iblr ⁇ Iselr (Formula 6)
- the non-selected current path flowing from the selected bit line BL2 to the selected word line WL2 via the three stages of non-selected memory cells is at least the following (a) to ( There are four paths d). Therefore, the total unselected memory cell current ⁇ Inselr is expressed by (Equation 7).
- the current control element D22 of the selected memory cell M22 when the current control element D22 of the selected memory cell M22 is broken and short-circuited, the current control element D22 can be regarded as a conductive state, and all the bit line voltage Vblr is applied to the resistance change element R22. Applied. Therefore, the selected bit line current Iblr has a value equal to or larger than the memory cell current that flows in a normal memory cell, regardless of whether the resistance change element R22 of the memory cell M22 is in the low resistance state or the first high resistance state. Therefore, since the current according to the resistance state of the resistance change element R22 of the memory cell M22 cannot be read accurately, the resistance state of the memory cell M22 cannot be detected.
- FIG. 9 is a circuit diagram for explaining a current path when one of the non-selected memory cells in the main memory cell array 601, for example, the memory cell M 23 has a short circuit defect.
- the circuit diagram in the case where the main memory cell array 600 of FIG. 5 described above is arranged in 3 ⁇ 3 the case where the memory cell M22 is selected and the memory cell M23 has a short circuit defect is shown. An example is shown.
- FIG. 10 is an equivalent circuit diagram of FIG.
- the Vss potential is applied to the word line WL2 selected by the word line selection circuit 203, and the bit line BL2 selected by the bit line selection circuit 204 is applied.
- the read voltage Vblr shown in (Equation 3) is applied, and the unselected bit lines BL1 and BL3 and the unselected word lines WL1 and WL3 are set to the high impedance state (Hi-Z) to select the memory cell M22.
- the non-selected bit lines BL1 and BL3 and the non-selected word lines WL1 and WL3 are in a high impedance state, but a voltage equal to or lower than the voltage applied between the selected bit line BL2 and the selected word line WL2. It may be set to a value.
- the memory cell M23 in the non-selected memory cell array 602 when the non-selected memory cell M23 in the non-selected memory cell array 602 has a short circuit defect, the memory cell M23 can be regarded as being almost in a conductive state, and the non-selected current as previously described. Since the resistance value becomes low and abnormal current flows in the plurality of current paths (b) and (d) of the path, the value of the all unselected memory cell current ⁇ Inselr shown in (Equation 7) becomes a large value and is selected. The memory cell current flowing through the memory cell M22 cannot be normally read out.
- FIG. 11 is a circuit diagram for explaining current paths in the memory cell array 202 of the present embodiment.
- an example of selecting the memory cell M22 is shown in the circuit diagram when the main memory cell array 600 of FIG.
- FIG. 12 is an equivalent circuit diagram of FIG.
- the memory cell M22 in the main memory cell array 601 in FIG. 11 is determined in the cell characteristic determination mode.
- the cell characteristic determination mode when determining whether the memory cell M22 is in a normal state or in a state where a short circuit has occurred, a Vss potential is applied to the word line WL2 selected by the word line selection circuit 203, and the bit line selection circuit 204 is selected.
- the cell characteristic determination voltage Vblt shown in (Equation 4) is applied to the bit line BL2 selected in (4), and the unselected bit lines BL1 and BL3 and the unselected word lines WL1 and WL3 are in the high impedance state (Hi-Z).
- the memory cell M22 is selected.
- bit line voltage Vblt that is lower than the bit line voltage Vblr in the normal read mode by the threshold voltage VF ′ of the reference current control element RD10 (substantially the same threshold voltage as the current control element D22) is applied to the bit line BL2.
- the non-selected bit lines BL1 and BL3 and the non-selected word lines WL1 and WL3 are in a high impedance state, but the voltage is less than the voltage applied between the selected bit line BL2 and the selected word line WL2. You may set to the voltage value.
- the selected bit line current Iblt that flows through the selected bit line is the selected memory cell current Iselt that flows through the selected memory cell M22 and the all unselected current that flows through the unselected memory cell array 602. This is the sum of the memory cell current ⁇ Inselt.
- the cell characteristic determination voltage Vblt applied between the selected bit line BL2 and the selected word line WL2 is applied to the memory cell M22, and the selected memory cell current Iselt flows according to the cell characteristic state of the memory cell M22.
- the cell characteristic determination voltage Vblt applied between the selected bit line BL2 and the selected word line WL2 is applied to the unselected memory cell array 602.
- the cell characteristic determination voltage Vblt applied to the selected bit line BL2 is determined by the unselected memory cells M11, M12, M13, M21, M23, M31, The voltage is divided and applied according to the respective impedances of M32 and M33. Therefore, when the non-selected memory cells M11, M12, M13, M21, M23, M31, M32, and M33 in the non-selected memory cell array 602 are normal memory cells, each current control element has only a voltage equal to or lower than the threshold voltage VF. Since no voltage is applied, each current control element is turned off, and almost no current flows through all the unselected memory cell currents ⁇ Inselt of the unselected memory cell array 602.
- the selected bit line current Iblt is almost the same as the selected memory cell current Iselt, and the cell characteristic state of the selected memory cell M22 can be read.
- the cell characteristic determination voltage Vblt applied between the selected bit line BL2 and the selected word line WL2 is lower than the threshold voltage VF of the current control element D22.
- each current control element has a voltage equal to or lower than the threshold voltage VF. Only applied. Therefore, each current control element is turned off, and almost no current flows through all the unselected memory cell currents ⁇ Inselt of the unselected memory cell array 602. That is, the selected bit line current Iblt is almost the same as the selected memory cell current Iselt. Therefore, the cell characteristic state of the selected memory cell M22 can be read by detecting the selected bit line current Iblt.
- the selected bit line current Iblt flowing in the selected bit line BL2 flowing when reading the state of the memory cell M22 is the sum of the selected cell current Iselt and the all unselected cell current ⁇ Inselt as shown in (Equation 8).
- the value of the total unselected cell current ⁇ Inselt is small enough to be ignored. Therefore, the selected bit line current Iblt flowing through the selected bit line BL2 can be approximated as shown in (Equation 9), and the memory cell current of the selected memory cell M22 can be read out via the selected bit line BL2. It is possible to read out whether the state is normal or short-circuit failure.
- Iblt Iselt + ⁇ Inselt (Formula 8) Iblt ⁇ Iselt (Formula 9)
- the current control element D22 When the selected memory cell M22 is a normal memory cell, when the bit line voltage Vblt shown in (Equation 4) is applied to the memory cell M22, the current control element D22 has a voltage equal to or lower than the threshold voltage VF. Is applied, the current control element D22 is turned off. Thereby, almost no current flows through the selected bit line current Iblt regardless of the resistance state of the resistance change element R22.
- the current control element D22 of the memory cell M22 when the current control element D22 of the memory cell M22 is short-circuited, the current control element D22 can be regarded as a conductive state, and all the bit line voltage Vblt is applied to the resistance change element R22.
- the resistance change element R22 when the resistance change element R22 is in the low resistance state, the selected bit line current Iblt flows in accordance with the resistance value of the resistance change element R22. Therefore, the memory cell M22 is short-circuited by detecting the current with the read circuit 206. It can be determined that it has been destroyed.
- the current control element D22 can be regarded as an off state (maximum off current flows).
- the maximum off-current flowing through the normal current control element D22 flows through the abnormal current control element D22, it may be determined that “the memory cell M22 is destroyed”.
- variable resistance element R22 when the variable resistance element R22 is in the first high resistance state, the selected bit line current Iblt hardly flows through the variable resistance element R22, so it can be determined whether or not the current control element D22 is destroyed. Have difficulty.
- variable resistance nonvolatile memory device 200 in the cell characteristic determination mode, at least when the variable resistance element R22 of the selected memory cell M22 is in the low resistance state. Can determine whether the state of the current control element D22 of the selected memory cell M22 is a normal state or a short breakdown state, and can specify the address of a defective memory cell. Further, when the resistance change element R22 of the selected memory cell M22 is in the first high resistance state, the state (normal state or short-circuit breakdown state) of the current control element D22 of the selected memory cell M22 cannot be correctly determined. It is possible to determine whether the state of the current control element D22 of the selected memory cell M22 is normal or destroyed by performing the cell characteristic determination mode after setting the resistance change element R22 of the selected memory cell M22 to the low resistance state. it can.
- the address of the defective memory cell can be specified by determining the selected bit line current Iblt flowing through the selected bit line BL2. For example, even if there are defective memory cells exceeding 2 bits such as M12, M11, and M23, there are only defective memory cells of 2 bits or less on the leakage current paths of (a) to (d).
- the non-selected memory cell array current War hardly flows, and the address of the defective memory cell can be specified similarly. If all three bits on the same leakage current path are defective memory cells, most of the memory cells in the memory cell array 202 have the same defect. It is possible to find a cell.
- FIG. 13 is a table (truth table for each mode) showing each setting state in the normal reading mode and the cell characteristic determination mode, and the state of the output terminal SAOUT of the reading circuit 206 shown in FIG. 6B.
- “L” is the first logic output in this embodiment, and indicates that the sense amplifier 300 outputs the L potential when the resistance state of the memory cell is in the low resistance state.
- “H” is the second logic output in the present embodiment, and indicates that the output of the sense amplifier 300 outputs the H potential when the resistance state of the memory cell is the first high resistance state. Yes.
- the current control element of the memory cell is turned on, and the memory cell current flowing through the memory cell is determined by the resistance state of the resistance change element of the memory cell.
- the potential of the terminal SAIN of the sense amplifier 300 of the read circuit 206 changes from the H potential to the L potential via the bit line BL and the bit line selection circuit 204.
- the resistance change element of the memory cell is in the low resistance state, the memory cell current increases, the potential of the terminal SAIN is quickly changed to the L potential, and the resistance change element of the memory cell is in the first high resistance state. If so, the memory cell current is reduced, and the potential at the terminal SAIN is slowly changed to the L potential or is maintained at the H potential.
- the comparison circuit 310 when the potential of the terminal SAIN and the terminal SAREF is compared by the comparison circuit 310 at a predetermined output timing, if the potential of the terminal SAIN is lower, it is determined that the L potential is output to the output terminal SAOUT and the current flowing through the memory cell is small. If the potential at the terminal SAIN is higher, the H potential is output to the output terminal SAOUT and it is determined that the current flowing through the memory cell is large. That is, if the sense amplifier 300 outputs an L potential, the state of the memory cell indicates a low resistance state, and if the output of the sense amplifier 300 outputs an H potential, the state of the memory cell indicates a first high resistance state. .
- the current control element of the selected memory cell when the current control element of the selected memory cell is destroyed, most of the voltage applied to the memory cell is applied to the resistance change element, so that the resistance change element is in the first high resistance state. Even then, a large amount of memory cell current may flow.
- the variable resistance element if the variable resistance element is in the low resistance state, the output of the sense amplifier 300 is L potential, and the state of the memory cell indicates the low resistance state, but if the variable resistance element is in the first high resistance state, the sense Since the output of the amplifier 300 becomes the L potential or the H potential, the resistance state of the memory cell cannot be accurately determined.
- the resistance state of the memory cell can be determined by the output potential of the sense amplifier 300.
- the resistance state of the memory cell cannot be determined.
- the current control element of the memory cell is turned off, so that the memory cell current flowing through the memory cell is almost independent of the resistance state of the resistance change element of the memory cell. Not flowing.
- this memory cell current is determined by the sense amplifier 300 of the read circuit 206 via the bit line BL and the bit line selection circuit 204, the output of the sense amplifier 300 becomes the H potential regardless of the resistance state of the resistance change element. Output.
- the current control element of the selected memory cell when the current control element of the selected memory cell is destroyed, most of the voltage applied to the memory cell is applied to the resistance change element, so that the resistance change element is in the first high resistance state. Even then, a large amount of memory cell current may flow. That is, if the variable resistance element is in the low resistance state, the output of the sense amplifier 300 is at the L potential, and it can be determined that the current control element is destroyed. In the resistance state, the output of the sense amplifier 300 becomes the L potential or the H potential depending on the resistance value of the variable resistance element, so that the cell characteristic state of the memory cell cannot be accurately determined.
- the state of the current control element of the memory cell is in a normal state by performing the cell characteristic determination mode after the resistance change element is set to the low resistance state in advance. It can be determined whether it is in a destructive state.
- the resistance change element is set in a low resistance state in advance, it is possible to clearly determine that the current control element is normal when a current of a predetermined value or more does not flow through the current control element.
- the resistance change element changes to the low resistance state.
- the state of the current control element of the memory cell can be determined. That is, when the resistance change element is in a low resistance state and a current of a predetermined value or more flows through the current control element, it can be determined that the current control element of the memory cell has a short circuit abnormality.
- the predetermined value may be the value of the maximum off-state current of the current control element of the memory cell.
- the maximum off current is, for example, 10 ⁇ A.
- the state of the current control element of the memory cell cannot be accurately determined.
- the cell characteristic determination is performed after the resistance change element is in the low resistance state. By executing the mode, it can be determined whether the current control element of the memory cell is in a normal state or a destructive state. A memory cell determined to have a current control element in a destroyed state may not be used, or may be subjected to a predetermined repair process or the like.
- FIG. 14 is an example of a determination flow in the cell characteristic determination mode that does not depend on the state of the resistance change element of the memory cell.
- step S101 when the reading circuit 206 is set to the cell characteristic determination mode (step S101), SW1 of the bit line control voltage switching circuit 400 is turned off and SW2 is turned on. As a result, the output terminal OUT2 of the bit line control voltage generation circuit 500 shown in FIG. 6B is selected, and the cell characteristic determination clamp voltage Vct is applied to the gate terminal of the bit line voltage control transistor N1 of the sense amplifier 300.
- At least one memory cell of the memory cell array 202 is selected by the word line selected by the word line selection circuit 203 and the bit line selected by the bit line selection circuit 204 (step S102). Further, a read operation is performed on the selected memory cell (step S103).
- step S104 the voltage output to the output terminal SAOUT of the sense amplifier 300 is determined (step S104), and if it is L potential, it is determined that the current control element of the memory cell is destroyed (step S105). If the potential is H, it is determined that the cell is a normal cell or a cell in which no breakdown of the current control element is detected (step S106). Then, after determining all memory cell regions (step S107), the cell characteristic determination mode is terminated.
- FIG. 15 is an example of a determination flow in the cell characteristic determination mode after the state of the resistance change element of the memory cell is first set to the low resistance state.
- a memory cell that is subject to cell characteristic determination is set to a low resistance state (step S200), and then the read circuit 206 is set to cell characteristic determination mode (step S201).
- SW1 is turned off and SW2 is turned on.
- the output terminal OUT2 of the bit line control voltage generation circuit 500 shown in FIG. 6B is selected, and the cell characteristic determination clamp voltage Vct is applied to the gate terminal of the bit line voltage control transistor N1 of the sense amplifier 300.
- At least one memory cell of the memory cell array 202 is selected by the word line selected by the word line selection circuit 203 and the bit line selected by the bit line selection circuit 204 (step S202). Further, the above-described cell characteristic determination operation (cell characteristic read operation) is performed on the selected memory cell (step S203).
- step S204 the voltage output to the output terminal SAOUT of the sense amplifier 300 is determined (step S204), and if it is L potential, it is determined that the current control element of the memory cell is destroyed (step S205). If the potential is H, it is determined as a normal cell (step S206). Then, after determining all memory cell regions (step S207), the cell characteristic determination mode is terminated.
- FIG. 16 shows an example of a flowchart of a method for relieving a memory cell determined as a defective memory cell in the cell characteristic determination mode.
- the abnormal current flowing through the defective memory cell is reduced by setting the variable resistance element of the defective memory cell to a third high resistance state having a higher resistance value than that of the first low resistance state. Cut. Or, in place of the defective memory cell, other memory cells other than the defective memory cell arranged on the same bit line as the defective memory cell and / or on the same word line as the defective memory cell An abnormal current flowing through a defective memory cell is cut by setting the resistance change element of the memory cell to a second high resistance state having a resistance value higher than that of the first high resistance state.
- these memories may be used for defective memory cells and other memory cells other than the defective memory cells arranged on the same bit line as the defective memory cell and / or on the same word line as the defective memory cell.
- the abnormal current flowing through the defective memory cell is cut by setting the resistance change elements of the cells to the above-described high resistance state. Further, in order to substitute a normal memory cell in place of the memory cell (target memory cell) brought into the high resistance state using the redundant memory cell, the address of the memory cell brought into the high resistance state is stored.
- the variable resistance nonvolatile memory device is set to a write mode (high resistance) (step S301), and a word line selection circuit is set.
- the high resistance write operation is performed on at least one selected defective memory cell of the memory cell array 202 by the word line selected in 203 and the bit line selected by the bit line selection circuit 204.
- another memory other than the defective memory cell arranged on at least one of the same bit line as the defective memory cell and the same word line as the defective memory cell A high resistance write operation is performed on the cell (step S302).
- a memory cell that performs a high resistance write operation is referred to as a target memory cell.
- a third high-resistance write voltage (third high-resistance pulse) is applied to the defective memory cell to bring the variable resistance element of the defective memory cell into the third high-resistance state.
- other memory cells other than the defective memory cell arranged on the same bit line as the defective memory cell and on the same word line as the defective memory cell are provided with resistance change elements of these other memory cells.
- a second high resistance write voltage (second high resistance pulse) for applying the second high resistance state is applied.
- the failure detection mode is set (step S303), and whether the defective memory cell is in the third high resistance state, or whether other memory cells other than the defective memory cell are in the second high resistance state. Is determined by the sense amplifier 300 of the read circuit 206 (step S304).
- the target memory cell is successfully increased in resistance. Judgment is made (step S305), the address of the target memory cell is stored in the defective address storage circuit 213 (step S306), and the process ends.
- step S304 the mode setting is again set to the write mode (high resistance) (step S307). Thereafter, it is determined whether another writing condition can be set (step S308). If another writing condition can be set, another writing condition is set (step S309), and the defective memory is again set.
- the above-described high resistance write operation is performed on the memory cells other than the cell or the defective memory cell (step S302).
- the defective memory cell includes a fourth high-resistance write voltage (fourth high-resistance pulse) whose absolute value is larger than the voltage value of the third high-resistance write voltage.
- Fourth high resistance write voltage having a current value larger than the current value of the third high resistance write voltage, and fourth high resistance write having a pulse width larger than the pulse width of the third high resistance write voltage A voltage may be applied.
- step S308 If it is determined in step S308 that another write condition cannot be set, it is determined that the resistance of the target memory cell has failed to be increased (step S310), and the process ends. In this case, since the defective memory cell cannot be relieved, it is treated as a defective circuit.
- defective memory cell detection flow and relief flow may be performed every predetermined period or every recording write when the variable resistance nonvolatile memory device 200 is powered on.
- FIG. 17 is a circuit diagram showing an example of the write circuit 205, the write power supply 210, and their connection relationship in the present embodiment.
- the write circuit 205 includes an HR write circuit 700 that applies a voltage and a current to the memory cell to change the resistance state of the resistance change element of the memory cell to a high resistance state, and the resistance of the resistance change element.
- the LR write circuit 800 applies voltage and current to the memory cell in order to change the state to the low resistance state.
- the HR write circuit 700 changes the resistance change element of the memory cell to the first high-resistance element.
- the first high resistance write voltage Vwh1 is applied to the bit line BL selected by the bit line selection circuit 204 with reference to the word line WL selected by the word line selection circuit 203. Is a circuit for applying.
- the HR write circuit 700 includes a PMOS 701, a PMOS 702, an NMOS 703, an NMOS 704, an inverter 705, and an inverter 706. Note that the descriptions simply “PMOS” and “NMOS” mean “PMOS transistor” and “NMOS transistor”, respectively.
- the PMOS 701, the PMOS 702, the NMOS 703, and the NMOS 704 have their main terminals (one drain terminal and the other source terminal) connected in series in this order to form one current path.
- the main terminal (source terminal) to which the PMOS 702 is not connected is connected to a power source (for example, the high resistance power source 212).
- the main terminal (source terminal) that is not connected to the NMOS 703 is connected to the ground potential.
- the HR write enable signal WEH output from the data signal input / output circuit 207 is input to the input terminal of the inverter 706 and the gate of the NMOS 703.
- the HR write enable signal WEH input from the input terminal of the inverter 706 is an inverted signal.
- the HR write pulse signal WPH output from the control circuit 209 is input to the input terminal of the inverter 705, and the signal input from the input terminal of the inverter 705 is input to the gates of the PMOS 701 and the NMOS 704 as inverted signals. .
- One main terminal (drain terminal) of each of the PMOS 702 and the NMOS 703 is connected, output from the write circuit 205 through the output terminal WDH of the HR write circuit 700, and connected to the bit line selection circuit 204 and the word line selection circuit 203.
- VH potential first high resistance write voltage Vwh1 supplied from the high resistance power supply 212 and a ground potential in accordance with the write pulse signal WPH. (Vss) is output, and when the HR write enable signal WEH is in the L state, the Hi-Z state is output from the output terminal WDH.
- the LR write circuit 800 changes the resistance change element of the memory cell to the first low-resistance element.
- the first low resistance write voltage Vwl1 is applied to the word line WL selected by the word line selection circuit 203 with reference to the bit line BL selected by the bit line selection circuit 204. Is a circuit for applying.
- the LR write circuit 800 includes a PMOS 801, a PMOS 802, an NMOS 803, an NMOS 804, an inverter 805, and an inverter 806.
- the PMOS 801, the PMOS 802, the NMOS 803, and the NMOS 804 have their main terminals (drain terminal or source terminal) connected in series in this order to form one current path.
- the main terminal (source terminal) to which the PMOS 802 is not connected is connected to a power source (for example, the power source 211 for reducing resistance).
- the main terminal (source terminal) not connected to the NMOS 803 is connected to the ground potential.
- the LR write enable signal WEL output from the data signal input / output circuit 207 is input to the input terminal of the inverter 806 and the gate of the NMOS 803, and the LR write enable signal WEL input from the input terminal of the inverter 806 is an inverted signal.
- the LR write pulse signal WPL output from the control circuit 209 is input to the input terminal of the inverter 805, and the signal input from the input terminal of the inverter 805 is input to the gates of the PMOS 801 and the NMOS 804 as inverted signals. .
- One main terminal (drain terminal) of each of the PMOS 802 and the NMOS 803 is connected, output from the write circuit 205 through the output terminal WDL of the LR write circuit 800, and connected to the word line selection circuit 203.
- the abnormal current flowing in the defective memory cell can be reduced by setting the defective memory cell to the third high resistance state having a resistance value at least equal to or higher than the resistance value of the first low resistance state. After that, even if repair processing is performed by replacing the bit line or word line including the defective memory cell with a redundant bit line or redundant word line, no abnormal current flows through the defective memory cell. Even when the cell array 202 is not disconnected, an abnormal current does not flow to the memory cell array 202, and stable reading can be performed on the selected memory cell.
- the third high resistance state is higher than the first high resistance state. Indicates the resistance value.
- the first high resistance write voltage Vwh1 is applied to a defective memory cell in which the current control element is in a short state
- the current control element is in a short state, so that the resistance change element has almost the first high resistance write voltage. This is because Vwh1 is applied, and the variable resistance element is in the second high resistance state in which the resistance value is higher than that in the first high resistance state.
- the third high resistance state is preferably as the resistance value is larger from the viewpoint of suppressing the current flowing through the defective memory cell.
- FIG. 18 is a diagram showing an example of voltage-current characteristics of the voltage applied to the selected bit line and the current flowing through the selected bit line in the present embodiment.
- all the memory cells 100 of the memory cell array 202 exhibit normal characteristics such as the characteristic (1) shown in FIG.
- the horizontal axis indicates the voltage V [V] applied to the selected bit line
- the vertical axis indicates the current I [ [mu] A]
- a characteristic such as the characteristic (10) shown by the broken line in FIG.
- all the memory cells 100 of the memory cell array 202 exhibit normal characteristics such as the characteristic (1) shown in FIG. 4 and the resistance change elements 102 of all the memory cells 100 are the first In the high resistance state, a characteristic such as the solid line characteristic (11) in FIG. 18 is exhibited.
- one of the non-selected memory cells in the memory cell array 202 of the variable resistance nonvolatile memory device 200 of FIG. 5 causes a short circuit failure in the current control element D23, such as the memory cell M23 shown in FIG.
- the resistance change element R23 of the defective memory cell M23 has a second low resistance state lower than the first low resistance state, for example, the resistance value in the second low resistance state is 10% of the resistance value in the first low resistance state.
- the resistance value is about 1 / n, even if the selected memory cell M22 has normal characteristics and is in the first high resistance state, it exhibits characteristics such as the characteristics (12) indicated by white squares in FIG.
- the resistance value of the resistance change element R23 of the defective memory cell M23 is set to When the resistance value is in the third high resistance state, characteristics such as the characteristic (13) indicated by white triangles in FIG. Similarly, for example, when the resistance value of the variable resistance element R23 of the defective memory cell M23 is set to the resistance value in the first low resistance state, a characteristic such as the characteristic (14) of x in FIG. 18 is exhibited.
- the selected memory cell 100 has the characteristics (13) and (14) in the first high resistance state. Indicates a characteristic having a higher resistance value than the characteristic (10) in the first low resistance state. Therefore, the state of the selected memory cell can be determined regardless of the presence or absence of a memory cell in the non-selected memory cell array.
- the third high resistance write voltage Vwh3 is set higher than the first high resistance write voltage Vwh1 so that the resistance value in the third high resistance state is 10 times or more the resistance value in the first high resistance state. Is set to a higher value, a characteristic such as the characteristic (15) indicated by the white circle in FIG. 18 is exhibited, and all the non-selected memory cells in the memory cell array 202 of the variable resistance nonvolatile memory device 200 have normal characteristics and the selected memory.
- the cell 100 has the characteristic that the resistance value is almost equal to the characteristic (11) in the first high resistance state, and the resistance value in the third high resistance state is 10 times the resistance value in the first high resistance state. This shows that it is even better.
- the pulse width twh1 of the HR write pulse signal WPH output from the control circuit 209 may be a pulse width twh2 having a longer pulse width. Further, as shown in the following embodiments, the current value may be increased by increasing the number of write circuits.
- variable resistance nonvolatile memory device (Second Embodiment) Next, a variable resistance nonvolatile memory device according to a second embodiment of the present invention will be described.
- FIG. 19 is a circuit diagram showing a configuration different from the configuration described in the first embodiment of the write circuit 255, the write power supply 210, and their connection relationship according to the present embodiment.
- the write circuit 255 includes an HR write circuit 750 that applies a voltage and a current to the memory cell to change the resistance state of the resistance change element of the memory cell to a high resistance state, and a resistance change.
- the LR write circuit 850 applies voltage and current to the memory cell in order to change the resistance state of the element to the low resistance state.
- the HR write circuit 750 includes a first HR write circuit 710 and a second write circuit 720, and the output terminal WDH1 of the first write circuit 710 and the output terminal WDH2 of the second write circuit 720 are connected to each other.
- the first write circuit 710 sets the resistance change element of the memory cell to the first As a voltage for transition to the high resistance state, the first high resistance write voltage is applied to the bit line BL selected by the bit line selection circuit 204 with the word line WL selected by the word line selection circuit 203 as a reference. Vwh1 is applied. Further, the third high resistance write voltage Vwh3 is applied by changing the power supply voltage VH output from the high resistance power supply 212 of the write power supply 210.
- the HR write circuit 750 includes the second write circuit 720, so that the first high resistance write current Iwh1 is output from the output terminal WDH1 of the first write circuit 710, and the second write circuit 720 is output from the output terminal WDH2.
- the detailed configuration of the HR write circuit 750 is as follows.
- the first HR write circuit 710 includes a PMOS 711, a PMOS 712, an NMOS 713, an NMOS 714, an inverter 715, and an inverter 716.
- the PMOS 711, the PMOS 712, the NMOS 713, and the NMOS 714 have their main terminals (drain terminal or source terminal) connected in series in this order to form one current path.
- the main terminal (source terminal) to which the PMOS 712 is not connected is connected to a power source (for example, the high resistance power source 212).
- the main terminal (source terminal) not connected to the NMOS 713 is connected to the ground potential.
- the first HR write enable signal WEH1 output from the data signal input / output circuit 207 is input to the input terminal of the inverter 716 and the gate of the NMOS 713, and the first HR write enable signal WEH1 input from the input terminal of the inverter 716 is an inverted signal. Is input to the gate of the PMOS 712.
- the HR write pulse signal WPH output from the control circuit 209 is input to the input terminal of the inverter 715, and the signal input from the input terminal of the inverter 715 is input to the gates of the PMOS 711 and the NMOS 714 as an inverted signal. .
- One main terminal (drain terminal) of each of the PMOS 712 and the NMOS 713 is connected, output from the write circuit 255 through the output terminal WDH of the HR write circuit 750, and connected to the bit line selection circuit 204.
- the second HR write circuit 720 includes a PMOS 721, a PMOS 722, an inverter 723, and an inverter 724.
- the main terminals (one drain terminal and the other source terminal) of the PMOS 721 and the PMOS 722 are connected in series in this order to form one current path.
- the main terminal (source terminal) to which the PMOS 722 is not connected is connected to a power source (for example, the high resistance power source 212).
- the second HR write enable signal WEH2 output from the control circuit 209 is input to the gate of the input terminal of the inverter 724, and the second HR write enable signal WEH2 input from the input terminal of the inverter 724 is the inverted signal of the gate of the PMOS 722. Is input.
- the HR write pulse signal WPH output from the control circuit 209 is input to the input terminal of the inverter 723, and the signal input from the input terminal of the inverter 723 is input to the gate of the PMOS 721 as an inverted signal.
- One main terminal (drain terminal) of the PMOS 722 is output from the write circuit 255 through the output terminal WDH of the HR write circuit 750 and connected to the bit line selection circuit 204.
- VH potential first high resistance write voltage Vwh1
- IHH2 second high resistance write current Iwh2
- the first HR write enable signal WEH1 is set to an H state, that is, an enabled state for the defective memory cell, the VHR potential is supplied by the first HR write circuit 710, and the output current of the current IHH1 flows.
- the cell By setting the cell to the third high resistance state that exhibits a resistance value greater than that of the first low resistance state, it is possible to reduce abnormal current that has flowed through the defective memory cell.
- the defective memory cell can be brought into the third high resistance state or a resistance value higher than that.
- the HR write circuit 750 in the following embodiment, a normal memory cell can be brought into a second high resistance state having a higher resistance value than the first high resistance state.
- FIG. 20 is a diagram showing an example of a repair flow for a defective memory cell in the present embodiment.
- the third high resistance state in which the resistance change element of the defective memory cell has a higher resistance value than the first low resistance state with respect to the memory cell determined as the defective memory cell in the cell characteristic determination mode.
- the abnormal current flowing in the defective memory cell is cut.
- the address of the defective memory cell is stored.
- variable resistance nonvolatile memory device 200 is set to a write mode (high resistance) (step S 401), the word line selected by the word line selection circuit 203 and the bit selected by the bit line selection circuit 204.
- a high resistance write operation (1) is performed on at least one selected defective memory cell of the memory cell array 202 by the line (step S402).
- the failure detection mode is set (step S403), and the sense amplifier 300 of the read circuit 206 determines whether the defective memory cell is in the third high resistance state (step S404).
- step S405 If it is in the third high resistance state, it is determined that the target defective memory cell has succeeded in increasing the resistance (step S405), and the address of the target defective memory cell is stored in the defective address storage circuit 213 (step S406). ),finish.
- step S404 the mode setting is again set to the write mode (high resistance) (step S407). Thereafter, it is determined whether another writing condition can be set (step S408). If another writing condition can be set, another writing condition is set (step S409), and the defective memory is again set. A high resistance write operation is performed on the cell (step S402).
- Another writing condition is, for example, changing a writing voltage value, a writing current value, a writing pulse time, a driving capability of a writing driver, or the like.
- step S408 if it is not possible to set another write condition, another write condition is connected to the same bit line or word line as the target defective memory cell.
- Memory cells are sequentially selected, and a high resistance write operation is performed (step S410).
- the other memory cell may be a defective memory cell different from the above-described defective memory cell, or may be a normal memory cell.
- the first high resistance described above as the write voltage is applied to the memory cell performing the high resistance write operation so as to be in the second high resistance state having a higher resistance value than the first high resistance state.
- a second high resistance write voltage (second high resistance pulse) Vwh2 higher than the control write voltage Vwh1 is applied. It is more preferable to set the second high resistance write voltage Vwh2 so that the resistance value in the second high resistance state is, for example, 10 times or more the resistance value in the first high resistance state.
- the defect detection mode is set (step S411), and all other memory cells connected to the same bit line or word line as the target defective memory cell and different from the defective memory cell are set in the high resistance state. It is determined by the sense amplifier 300 of the read circuit 206 (step S412). If all other memory cells other than the defective memory cell connected to the same bit line or word line as the target defective memory cell are in a high resistance state, the address of the target defective memory cell Is stored in the defective address storage circuit 213 (step S406), and the process ends. If all other memory cells other than the defective memory cell connected to the same bit line or word line as the target defective memory cell are not in a high resistance state, the target defective memory cell It is determined that the resistance has failed (step S413), and the process ends. In this case, since it cannot be relieved, the memory cell array 202 is treated as a defective circuit.
- FIG. 21 is a diagram showing an example of voltage-current characteristics of the voltage applied to the selected bit line and the current flowing through the selected bit line in the present embodiment.
- all the memory cells 100 of the memory cell array 202 exhibit normal characteristics such as the characteristic (1) shown in FIG.
- the horizontal axis indicates the voltage V [V] applied to the selected bit line
- the vertical axis indicates the current I [ [mu] A]
- a characteristic such as the characteristic (10) shown by the broken line in FIG.
- all the memory cells 100 of the memory cell array 202 exhibit normal characteristics such as the characteristic (1) shown in FIG. 4 and the resistance change elements 102 of all the memory cells 100 are the first In the case of the high resistance state, a characteristic such as the characteristic (11) of the thick solid line in FIG. 21 is shown.
- the selected memory cell 100 in the memory cell array 202 of the variable resistance nonvolatile memory device 200 of FIG. 5 is set to the first high resistance state, and one of the non-selected memory cells is, for example, a memory cell as shown in FIG.
- the current control element D23 is short-circuited like M23, and the resistance change element R23 of the defective memory cell M23 has a resistance value in the second low-resistance state lower than the resistance value in the first low-resistance state.
- FIG. The characteristic of the white triangle mark (20) is shown.
- the selected memory cell 100 is connected to the same bit line as that of the defective memory cell M23 in the first high resistance state, and other memory cells M13, M33,.
- the characteristic (20) when all are set to the first low resistance state indicates a characteristic that the selected memory cell 100 has a higher resistance value than the characteristic (10) of the first low resistance state. Therefore, all the other memory cells M13, M33,... Connected to the same bit line as the defective memory cell M23, which are different from the defective memory cell M23, have resistance values of the first low resistance state.
- the state of the selected memory cell can be determined regardless of the presence or absence of a defect in the memory cell in the unselected memory cell array.
- all other memory cells M13, M33,... Connected to the same bit line as the defective memory cell M23 and different from the defective memory cell M23 are more resistant than the first high resistance state. It is better to have a higher resistance state.
- all the other memory cells M13, M33,... Connected to the same bit line as the defective memory cell M23 and different from the defective memory cell M23 are all in the first high resistance state resistance value.
- the second high resistance state is 10 times higher than the resistance value, a characteristic such as the characteristic (21) of the white square in FIG. 21 is exhibited, and the resistance is higher (less current) than the characteristic (20). The characteristics are shown. Therefore, it is possible to better determine the state of the selected memory cell regardless of whether there is a defect in the memory cell in the unselected memory cell array.
- FIG. 22A shows a configuration diagram of the variable resistance nonvolatile memory device 200 according to the first embodiment of FIG. 5 with redundant memory cell arrays 620 having the same number of memory cells 100 in each column of the main memory cells 600.
- An example of the variable resistance nonvolatile memory device 900 is shown.
- the redundant memory cell array 620 in FIG. 22A one memory cell 100 is arranged in each column of the main memory cell array 600, and one row of redundant memory cell arrays 620 is configured.
- the redundant memory cell array 620 in FIG. 22A is arranged at the upper end of the main memory cell array 600, but it may be arranged in the main memory cell array 600.
- a variable resistance nonvolatile memory device 900 includes a memory main body 201 on a substrate.
- the memory body 201 includes a memory cell array 202.
- the memory cell array 202 is similar to the main memory cell array 600 in which a plurality of memory cells 100 shown in FIG. 2 are arranged in a matrix in the row direction and the column direction.
- a redundant memory cell array 620 in which a plurality of memory cells 100 shown in FIG. 2 are arranged is provided. .. And a plurality of bit lines BL 1, BL 2, BL 3,... Arranged in such a manner as to intersect with each other, and further, the word lines WL 1, WL 2 are provided. , WL3,... And at least one redundant word line WLR1,.
- the plurality of word lines WL1, WL2, WL3,... are arranged in parallel to each other in the same plane (in the first plane) parallel to the main surface of the substrate.
- the plurality of bit lines BL1, BL2, BL3,... are arranged in parallel to each other in the same plane parallel to the first plane (in a second plane parallel to the first plane).
- the redundant word lines WLR1,... are arranged in parallel with the word lines WL1, WL2, WL3,.
- the first plane and the second plane are arranged in parallel, and the plurality of word lines WL1, WL2, WL3,... And the plurality of bit lines BL1, BL2, BL3,.
- the memory cells M11, M12, M13, M21, M22 are located at three-dimensionally intersecting positions of the word lines WL1, WL2, WL3,... And the bit lines BL1, BL2, BL3,. , M23, M31, M32, M33,... (Hereinafter referred to as “memory cells M11, M12, M13,...”) Are arranged in the redundant memory cell array 620, and bit lines BL1, BL2, Redundant memory cells MW1, MW2, MW3,... Are arranged at the positions where BL3,... And redundant word lines WLR1,.
- Memory cells M11, M12, M13,... Are current control elements D11, D12, D13, D21, D22, D23, D31, D32, D33, (hereinafter referred to as “current control elements D11, D12, D13,. ..)), And resistance change elements R11, R12, R13, R21, R22, R23, R31, R32, R33,... Connected in series with the current control elements D11, D12, D13,. (Hereinafter referred to as “resistance change elements R11, R12, R13,...”).
- the redundancy memory cells MW1, MW2, MW3,... Have resistance changes connected in series with the current control elements DW1, DW2, DW3,... And the current control elements DW1, DW2, DW3,. It is composed of elements RW1, RW2, RW3,.
- one terminal of the resistance change elements R11, R21, R31,... In the main memory cell array 600 is connected to the current control elements D11, D21, D31,.
- the other terminal is connected to the bit line BL1, and one terminal of the resistance change elements R12, R22, R32,... Is connected to the current control elements D12, D22, D32,.
- the other terminal is connected to the bit line BL2, and one terminal of the resistance change elements R13, R23, R33,... Is connected to the current control elements D13, D23, D33,.
- One terminal is connected to the bit line BL3.
- one terminal of the resistance change elements RW1, RW2, RW3,... In the redundant memory cell array 620 is connected to the current control elements DW1, DW2, DW3, and the other terminal is the redundant word line. WLR1,... Are connected. Further, one terminal of the current control elements DW1, DW2, DW3,... Is connected to the resistance change elements RW1, RW2, RW3,..., And the other terminal is the bit lines BL1, BL2, BL3. , ... are connected.
- a resistance change element is connected to the bit line side and a current control element is connected to the word line side.
- a current control element is connected to the bit line side and resistance change is made to the word line side.
- Elements may be connected.
- at least one redundant word line WLR1,... Of the redundant memory cell array 620 may be provided, and a plurality of redundant word lines WLR1,.
- the word line selection circuit 203 receives the row address information signal output from the address signal input circuit 208 and the address match determination signal from the address comparison circuit 214, and in response to the row address information and the address match determination signal, .., And redundant word lines WLR1,..., A voltage supplied from the write circuit 205 is applied to the selected word line among the word lines WL1, WL2, WL3,. In addition, a predetermined unselected row application voltage (Vss to Vwl, or Vss to Vwh) is applied to the unselected word line, or a high impedance (Hi-Z) state is set.
- the bit line selection circuit 204 receives the column address information output from the address signal input circuit 208 and the address match determination signal from the address comparison circuit 214, and uses the column address information and the address match determination signal as the column address information.
- a voltage supplied from the write circuit 205 or a voltage supplied from the read circuit 206 is applied to the selected bit line among the plurality of bit lines BL1, BL2, BL3,.
- a predetermined non-selected column applied voltage (voltage of Vss to Vwl, voltage of Vss to Vwh, or voltage of Vss to Vbl) is applied to the non-selected bit line, or high impedance (Hi-Z) Can be in a state.
- word line selection circuit 203 and the bit line selection circuit 204 correspond to the memory selection circuit in the present invention.
- the defective address storage circuit 213 stores the row address information input from the address signal input circuit 208 as a defective address when it is determined as defective when the operation mode of the reading circuit 206 is the cell characteristic determination mode. Specifically, as in the case of storing defective addresses in bit line units, the defective address storage circuit 213 has an address conversion table (not shown), a defective word line having defective memory cells, and a replacement destination. The redundant word lines having the redundant memory cells are stored in association with each other.
- the address comparison circuit 214 compares the row address information input from the address signal input circuit 208 with the defective address stored in the defective address storage circuit 213, and addresses match whether they match. A determination signal is output to the word line selection circuit 203. If the row address information input from the address signal input circuit 208 matches the address of the defective word line stored in the defective address storage circuit 213, it is stored in the defective address storage circuit 213 in the relief mode. According to the address conversion table, the defective word line is replaced with the replacement redundant word line, and writing and reading of the record are performed.
- the arrangement of the redundant memory cell array 620 is not limited to the row direction as shown in FIG. 22A. As already described in the first embodiment, the arrangement in the column direction as shown in FIG. 5 is conceivable, and other arrangements are possible.
- 22B, 22C, and 22D are diagrams showing other arrangement examples of the main memory cell array and the redundant memory cell array. 22B, 22C, and 22D, the hatched portion indicates the position of the redundant memory cell array in the memory cell array.
- the main memory cell array 600 may be configured as a memory cell array 232 including redundant memory cell arrays 630 and 640 in both the column direction and the row direction, or one of them.
- the main memory cell array is divided into a plurality of main memory cell arrays 650a, 650b, 650c, and 650d, and each of the divided main memory cell arrays 650 has a column direction and a row direction.
- the memory cell array 242 may include redundant memory cell arrays 660a, 660b, 660c, 660d, 670a, 670b, 670c, and 670d.
- the main memory cell array is divided into a plurality of main memory cell arrays 680a, 680b, 680c, and 680d, and each of the divided main memory cell arrays 680 is divided into the column direction and the row direction.
- the memory cell array 252 may be provided with redundant memory cell arrays 690a, 690b, 700a, and 700b in both or one of them.
- variable resistance nonvolatile memory device Next, a variable resistance nonvolatile memory device according to a fifth embodiment of the present invention will be described.
- 23A to 23C are circuit diagrams showing the bit line control voltage generation circuit 500 of the read circuit 206 of the nonvolatile memory device according to this embodiment.
- the bit line control voltage generation circuit 501 shown in FIG. 23A is an example in which the reference resistance change element RE10 of the bit line control voltage generation circuit 500 of FIG. 6B is changed to a fixed resistance element RR21.
- the resistance value of the fixed resistance element RR21 is set to one of the resistance values of the reference resistance change element RE10 from the low resistance state to the high resistance state.
- only one fixed resistance element is shown, but a plurality of fixed resistance elements may be provided and switched independently by a switch.
- the bit line control voltage generation circuit 501 outputs to OUT1 and OUT2.
- the read clamp voltage Vcr and the cell characteristic determination clamp voltage Vct can be easily generated. Further, by using the fixed resistance element RR21 having a small variation in resistance value, variations in the read clamp voltage Vcr and the cell characteristic determination clamp voltage Vct can be reduced, and the state of the memory cell can be detected with higher accuracy. .
- a bit line control voltage generation circuit 502 shown in FIG. 23B changes the reference resistance change element RE10 of the bit line control voltage generation circuit 500 of FIG. 6B to a fixed resistance element RR22, and performs reference current control of the bit line control voltage generation circuit 500.
- the resistance value of the fixed resistance element RR22 is set to one of the resistance values of the reference resistance change element RE10 from the low resistance state to the high resistance state, and the resistance value of the fixed resistance element RR12 is the threshold voltage of the reference current control element RD11.
- a voltage corresponding to VF is set to such a resistance value that is applied to both ends of the fixed resistance element RR12.
- a bit line control voltage generation circuit 503 shown in FIG. 23C changes the reference resistance change element RE10 and the NMOS transistor N10 of the bit line control voltage generation circuit 500 of FIG.
- the reference current control element RD10 is a fixed resistance element RR13.
- the resistance value of the fixed resistance element RR23 is set such that a voltage corresponding to the threshold voltage Vtn of the NMOS transistor and the voltage applied to the reference resistance change element RE10 is applied to the fixed resistance element RR23.
- the resistance value of the fixed resistance element RR13 is set to a resistance value such that a voltage corresponding to the threshold voltage VF of the reference current control element RD11 is applied to both ends of the fixed resistance element RR13.
- a voltage exceeding the threshold voltage of the current control element is output to the output terminal OUT1, and the current control of the memory cell is output to the output terminal OUT2.
- Any circuit configuration that outputs a voltage equal to or lower than the threshold voltage of the element may be used.
- the reference fixed resistance element may be a resistance change element.
- FIG. 24 is a circuit diagram showing an example of the configuration of the readout circuit 206 in the present embodiment.
- the same reference numerals are used for the same components as in the previous drawings, and the description thereof is omitted.
- the read circuit 206 shown in FIG. 24 includes a sense amplifier 301, a bit line control voltage switching circuit 400, and a bit line control voltage generation circuit 504.
- the sense amplifier 301 includes a comparison circuit 310, a current mirror circuit 321 and a bit line voltage control transistor N1.
- the current mirror circuit 321 includes a PMOS transistor P1, a PMOS transistor P2, a PMOS transistor P3, a PMOS transistor P4, and a constant current circuit 330.
- the source terminals of the PMOS transistor P1, the PMOS transistor P2, the PMOS transistor P3, and the PMOS transistor P4 of the current mirror circuit 321 are connected to the power source, the gate terminals are connected to each other, and the PMOS transistor P1.
- the other terminal of the constant current circuit 330 is grounded.
- the drain terminal of the PMOS transistor P2 is connected to one input terminal (for example, + terminal) of the comparison circuit 310 and the drain terminal of the bit line voltage control transistor N1.
- the drain terminal of the PMOS transistor P3 and the drain terminal of the PMOS transistor P4 are connected to the bit line control voltage generation circuit 504, respectively.
- the gate terminal of the bit line voltage control transistor N1 is connected to the output terminal of the bit line control voltage switching circuit 400, and the source terminal of the bit line voltage control transistor N1 is connected to the bit line selection circuit via the terminal BLIN of the read circuit 206. 204 is connected.
- the other terminal (eg, ⁇ terminal) of the comparison circuit 310 is connected to the terminal SAREF of the readout circuit 206, and the output terminal of the comparison circuit 310 is connected to the data signal input / output circuit via the output terminal SAOUT of the readout circuit 206. It is connected to 207 and outputs data to the outside.
- the voltage applied to the gate terminal of the bit line voltage control transistor N1 is generated by the bit line control voltage generation circuit 504.
- the bit line control voltage generation circuit 504 includes a read clamp voltage generation circuit 510 that generates a read clamp voltage Vcr and a cell characteristic determination clamp voltage generation circuit 520 that generates a cell characteristic determination clamp voltage Vct.
- the read clamp voltage generation circuit 510 includes an NMOS transistor N14 and a reference memory cell RM14.
- the reference memory cell RM14 is configured by connecting a reference resistance change element RE14 and a reference current control element RD14 in series.
- the drain terminal and gate terminal of the NMOS transistor N14 are connected to the drain terminal of the PMOS transistor P3 of the current mirror circuit 321 and to the output terminal OUT1 of the bit line control voltage generation circuit 504, and the read clamp voltage Vcr. Is output from the output terminal OUT1.
- the source terminal of the NMOS transistor N14 is connected to one terminal of the reference resistance change element RE14 of the reference memory cell RM14, and the other terminal of the reference resistance change element RE14 is connected to one terminal of the reference current control element RD14.
- the other terminal of the reference current control element RD14 is grounded.
- the cell characteristic determination clamp voltage generation circuit 520 includes an NMOS transistor N24 and a reference fixed resistance element RR24.
- the drain terminal and gate terminal of the NMOS transistor N24 are connected to the drain terminal of the PMOS transistor P4 of the current mirror circuit 321 and to the output terminal OUT2 of the bit line control voltage generation circuit 504, and the cell characteristic determination clamp voltage Vct is set. Output from the output terminal OUT2.
- the source terminal of the NMOS transistor N24 is connected to one terminal of the reference fixed resistance element RR24, and the other terminal of the reference fixed resistance element RR24 is grounded.
- the reference current control element RD14 and the reference resistance change element RE14 of the reference memory cell RM14 are current control elements D11, D12, D13,... And resistance change elements R11, R12, R13 included in the memory cell array 202.
- the reference fixed resistance element RR24 is set to a resistance value of the resistance change elements R11, R12, R13,... Included in the memory cell array 202 in a low resistance state or a high resistance state.
- the reference fixed resistance element RR24 may be a resistance change element.
- the reference resistance change element RE14 can be set to a high resistance state or a low resistance state in the same manner as the resistance change elements included in the memory cell array 202. In order to detect at least the memory cell in the low resistance state, it is desirable to set the resistance values of the reference resistance change element RE10 and the reference fixed resistance element RR24 to the average resistance value of the memory cell array 202 in the high resistance state. .
- the reference memory cell RM14 can be realized with the same configuration as the memory cells M11, M12, M13,... Included in the memory cell array 202, and thus detects the state of the memory cell with higher accuracy.
- the fixed resistance element RR24 having a small variation in resistance value, variations in the read clamp voltage Vcr and the cell characteristic determination clamp voltage Vct can be reduced, and the state of the memory cell can be detected with higher accuracy. can do.
- variable resistance nonvolatile memory device (Seventh embodiment) Next, a variable resistance nonvolatile memory device according to a seventh embodiment of the present invention will be described.
- FIG. 25 is a circuit diagram showing an example of the configuration of the read circuit 206 in the present embodiment, and includes at least two cell characteristic determination clamp voltage generation circuits 520 of FIG. Further, in the present embodiment, a case where two cell characteristic determination clamp voltage generation circuits are configured will be described, but three or more cell characteristic determination clamp voltage generation circuits may be configured.
- the read circuit 206 shown in FIG. 25 includes a sense amplifier 302, a bit line voltage switching circuit 401, and a bit line control voltage generation circuit 505.
- the sense amplifier 302 includes a comparison circuit 310, a current mirror circuit 322, and a bit line voltage control transistor N1.
- the current mirror circuit 322 includes a PMOS transistor P1, a PMOS transistor P2, a PMOS transistor P3, a PMOS transistor P4, a PMOS transistor P5, and a constant current circuit 330.
- the source terminals of the PMOS transistor P1, the PMOS transistor P2, the PMOS transistor P3, the PMOS transistor P4, and the PMOS transistor P5 of the current mirror circuit 322 are connected to the power supply, and the gate terminals are connected to each other.
- the drain terminal of the PMOS transistor P1 and one terminal of the constant current circuit 330 are connected.
- the other terminal of the constant current circuit 330 is grounded.
- the drain terminal of the PMOS transistor P2 is connected to one input terminal (for example, + terminal) of the comparison circuit 310 and the drain terminal of the bit line voltage control transistor N1.
- the drain terminal of the PMOS transistor P3, the drain terminal of the PMOS transistor P4, and the drain terminal of the PMOS transistor P5 are connected to the bit line control voltage generation circuit 505, respectively.
- the gate terminal of the bit line voltage control transistor N1 is connected to the output terminal of the bit line voltage switching circuit 401, and the source terminal of the bit line voltage control transistor N1 is connected to the bit line selection circuit 204 via the terminal BLIN of the read circuit 206. Connected with.
- the other terminal (eg, ⁇ terminal) of the comparison circuit 310 is connected to the terminal SAREF of the readout circuit 206, and the output terminal of the comparison circuit 310 is connected to the data signal input / output circuit via the output terminal SAOUT of the readout circuit 206. It is connected to 207 and outputs data to the outside.
- load currents Ild4 and Ild5 are determined from the PMOS transistor P4 and the PMOS transistor P5, respectively.
- the voltage applied to the gate terminal of the bit line voltage control transistor N1 is generated by the bit line control voltage generation circuit 505.
- the bit line control voltage generation circuit 505 includes a read clamp voltage generation circuit 510 that generates a read clamp voltage Vcr, a cell characteristic determination clamp voltage generation circuit 521 that generates a first cell characteristic determination clamp voltage Vct1, and a second cell.
- a cell characteristic determination clamp voltage generation circuit 522 that generates a characteristic determination clamp voltage Vct2 is configured.
- the read clamp voltage generation circuit 510 includes an NMOS transistor N14 and a reference memory cell RM14.
- the reference memory cell RM14 is configured by connecting a reference resistance change element RE14 and a reference current control element RD14 in series.
- the drain terminal and gate terminal of the NMOS transistor N14 are connected to the drain terminal of the PMOS transistor P3 of the current mirror circuit 322 and to the output terminal OUT1 of the bit line control voltage generating circuit 505, and the read clamp voltage Vcr. Is output from the output terminal OUT1.
- the source terminal of the NMOS transistor N14 is connected to one terminal of the reference resistance change element RE14 of the reference memory cell RM14, and the other terminal of the reference resistance change element RE14 is connected to one terminal of the reference current control element RD14.
- the other terminal of the reference current control element RD14 is grounded.
- the cell characteristic determination clamp voltage generation circuit 521 includes an NMOS transistor N25 and a reference fixed resistance element RR25.
- the drain terminal and gate terminal of the NMOS transistor N25 are connected to the drain terminal of the PMOS transistor P4 of the current mirror circuit 322 and to the output terminal OUT2 of the bit line control voltage generation circuit 505, and the first cell characteristic determination clamp
- the voltage Vct1 is output from the output terminal OUT2.
- the source terminal of the NMOS transistor N25 is connected to one terminal of the reference fixed resistance element RR25, and the other terminal of the reference fixed resistance element RR25 is grounded.
- the cell characteristic determination clamp voltage generation circuit 522 includes an NMOS transistor N26 and a reference fixed resistance element RR26.
- the drain terminal and the gate terminal of the NMOS transistor N26 are connected to the drain terminal of the PMOS transistor P5 of the current mirror circuit 322 and to the output terminal OUT3 of the bit line control voltage generation circuit 505, and the second cell characteristic determination clamp The voltage Vct2 is output from the output terminal OUT3.
- the source terminal of the NMOS transistor N26 is connected to one terminal of the reference fixed resistance element RR26, and the other terminal of the reference fixed resistance element RR26 is grounded.
- the reference current control element RD14 and the reference resistance change element RE14 of the reference memory cell RM14 are current control elements D11, D12, D13,... And resistance change elements R11, R12, R13 included in the memory cell array 202.
- the reference fixed resistance elements RR25 and RR26 are set to the resistance values of the resistance change elements R11, R12, R13,... Included in the memory cell array 202 in the low resistance state or the high resistance state.
- the reference fixed resistance elements RR25 and RR26 may be resistance change elements.
- the reference resistance change element RE14 can be set to a high resistance state or a low resistance state in the same manner as the resistance change elements included in the memory cell array 202. In order to detect at least the memory cell in the low resistance state, the resistance values of the reference resistance change element RE14 and the reference fixed resistance elements RR25 and RR26 should be set to the average resistance value of the memory cell array 202. Is desirable.
- the determination clamp voltage Vct2 is Vre (substantially the same applied voltage as the resistance change elements R11, R12, R13,...) Applied to the reference resistance change element RE14, and the threshold voltages of the NMOS transistors N14, N25, N26 are Vtn.
- the threshold voltage is substantially the same as the NMOS transistor N1
- the threshold voltage of the reference current control element RD14 is VF ′′
- the threshold voltage is substantially the same as the threshold voltage VF of the current control elements D11, D12, D13, etc
- the reference fixed resistance element The voltage applied to RR25 and RR26 is Vre , When Vre2, respectively, (Equation 10), (Equation 11) is expressed by (Equation 12).
- Vcr Vre + Vtn + VF ”(Formula 10)
- Vct1 Vr1 + Vtn (Formula 11)
- Vct2 Vr2 + Vtn (Formula 12)
- the NMOS transistors N14, N25, and N26 are configured with the same transistor size as the bit line voltage control transistor N1 of the sense amplifier 302, and the PMOS transistors P3, P4, and P5 of the sense amplifier 302 are configured with the same transistor size as the PMOS transistor P2.
- the NMOS transistor N14 and the PMOS transistor P3 may be reduced in size while maintaining the size ratio of the bit line voltage control transistor N1 and the PMOS transistor P2.
- the NMOS transistor N25 and the PMOS transistor P4, and the NMOS transistor N26 and the PMOS transistor P5 may be reduced in size while maintaining the size ratio between the bit line voltage control transistor N1 and the PMOS transistor P2.
- the threshold voltage Vtn of the bit line voltage control transistor N1 is simulated based on the voltage from the output terminal OUT1 to the terminal BLIN of the read circuit 206 (that is, the bit line voltage when the memory cell is read). Higher voltage is output. Further, a voltage lower than the output terminal OUT2 by the threshold voltage VF ′′ of the reference current control element RD14 than the output terminal OUT1, a voltage Vre applied to the reference resistance change element RE14, and a voltage Vre1 applied to the reference fixed resistance element RR25.
- a total voltage of the differential voltage (Vre ⁇ Vre1) is output, and is applied from the output terminal OUT3 to a voltage lower than the output terminal OUT1 by the threshold voltage VF ′′ of the reference current control element RD14 and to the reference resistance change element RE14.
- the total voltage of the difference voltage (Vre ⁇ Vre2) between the voltage Vre and the voltage Vre2 applied to the reference fixed resistance element RR26 is output.
- the bit line voltage switching circuit 401 includes switches SW1, SW2, and SW3.
- One terminal of the switch SW1 of the bit line voltage switching circuit 401 is connected to the output terminal OUT1 of the bit line control voltage generation circuit 505, and one terminal of the switch SW2 is connected to the output terminal OUT2 of the bit line control voltage generation circuit 505.
- One terminal of the switch SW3 is connected to the output terminal OUT3 of the bit line control voltage generation circuit 505.
- the other terminals of the switch SW1, the switch SW2, and the switch SW2 are connected to each other and connected to the gate terminal of the bit line voltage control transistor N1 of the sense amplifier 302.
- the bit line voltage switching circuit 401 sets the read clamp voltage Vcr at the output terminal OUT1 of the bit line control voltage generation circuit 505 by turning SW1 on and SW2 and SW3 off. Output to the gate terminal of the transistor N1.
- the first cell of the output terminal OUT2 of the bit line control voltage generation circuit 505 is set by turning off SW1, turning on one of SW2 and SW3, and turning off the other.
- the characteristic determination clamp voltage Vct1 or the second cell characteristic determination clamp voltage Vct2 at the output terminal OUT3 is output to the gate terminal of the transistor N1.
- bit line voltage switching circuit 401 applies the read clamp voltage Vcr to the gate terminal of the bit line voltage control transistor N1 of the sense amplifier 302 in the normal read mode, and the first cell characteristic determination clamp voltage in the cell characteristic determination mode. Vct1 or the second cell characteristic determination clamp voltage Vct2 is applied.
- the voltage applied to the bit line does not exceed a voltage lower than the voltage applied to the gate terminal of the bit line voltage control transistor N1 by the threshold voltage Vtn of the transistor N1.
- the bit line voltage Vblr applied to the line and the bit line voltage Vblt1 (SW1: on state, SW2 off state) and Vblt2 (SW1: off state, SW2 on state) applied to the bit line in the cell characteristic determination mode are: These can be expressed by (Expression 13), (Expression 14), and (Expression 15), respectively.
- the current control element included in the memory cell array 202 is turned on, and the memory cell state is changed. Can be detected.
- the characteristics of the current control element having various variations can be detected by switching and applying a plurality of voltages equal to or lower than the threshold voltage VF of the current control element to the bit line.
- FIG. 26 is an example of a determination flow in the cell characteristic determination mode using the nonvolatile memory device according to the seventh embodiment. This determination flow will be described assuming that the first and second clamp voltages can be set using the circuit diagram described in FIG. 25 as an example.
- step S500 when the cell characteristic determination mode is set (step S500), SW1 of the bit line voltage switching circuit 401 is turned off.
- step S501 in order to set the first cell characteristic determination clamp voltage (step S501), SW2 of the bit line voltage switching circuit 401 is turned on and SW3 is turned off, so that the bit line control voltage generation circuit 505 The output terminal OUT2 is selected, and the first cell characteristic determination clamp voltage Vct1 is applied to the gate terminal of the bit line voltage control transistor N1 of the sense amplifier 302.
- step S502 at least one memory cell of the memory cell array 202 is selected by the word line selected by the word line selection circuit 203 and the bit line selected by the bit line selection circuit 204 (step S502).
- step S503 The above-described cell characteristic determination operation (cell characteristic read operation) is performed on the memory cell (step S503). Then, the output voltage of the sense amplifier 302 is determined (step S504). If the potential is L, it is determined that the current control element of the memory cell is destroyed (step S505). If the potential is H, the cell is a normal cell. A determination is made as a cell in which no breakdown of the current control element has been detected (step S506). If all the cell characteristic determination clamp voltages have been detected (Yes in step S507), all the memory cell regions are determined (step S509), and then the cell characteristic determination mode is terminated and all the cell characteristic determinations are completed. If detection by the clamp voltage has not been performed (No in step S507), switching to the next cell characteristic determination clamp voltage (after the second cell characteristic determination clamp voltage) (step S508), read operation (step S503) and thereafter Repeat the flow.
- the state of the memory cell can be sequentially detected with a plurality of cell characteristic determination operation voltages, so that the variation of the threshold voltage of the current control element of the memory cell is evaluated. can do.
- the cell characteristic determination clamp voltage is evaluated starting from a low cell characteristic determination clamp voltage and then set to a higher cell characteristic determination clamp voltage. This is because, when a high cell characteristic determination clamp voltage is initially set, if the current control element of the memory cell is destroyed, the set high cell characteristic determination clamp voltage is applied to the resistance change element of the memory cell, This is because the state of the resistance change element may change when the write voltage of the resistance change element is exceeded. In particular, when the variable resistance element changes to the high resistance state, there is a case where the destruction state of the memory cell is not detected, as described in the truth table for each mode in FIG. In addition, it is more preferable that the voltage applied in the cell characteristic determination mode is applied with a polarity that changes the memory cell to a low resistance state.
- variable resistance nonvolatile memory device (Eighth embodiment) Next, a variable resistance nonvolatile memory device according to an eighth embodiment of the present invention will be described.
- FIG. 27 is a circuit diagram showing an example of the configuration of the read circuit 206 in this embodiment. As shown in FIG. 27, an example of the configuration using at least two voltage sources in the bit line control voltage generation circuit 506 is shown. Is shown. In the present embodiment, a case where two voltage sources are used will be described. However, three or more voltage sources may be used and the bit line control voltage switching circuit 400 may be used for switching. .
- 27 is composed of a sense amplifier 303, a bit line control voltage switching circuit 400, and a bit line control voltage generation circuit 506.
- the bit line control voltage generation circuit 506 includes voltage sources VPP1 and VPP2.
- the voltage source VPP1 outputs the read clamp voltage Vcr from the output terminal OUT1 of the bit line control voltage generation circuit 506, and the voltage source VPP2 outputs the cell characteristic determination clamp voltage Vct from the output terminal OUT2 of the bit line control voltage generation circuit 506. To do.
- the voltage sources VPP1 and VPP2 may be incorporated in the nonvolatile memory device or supplied from an external power source.
- the sense amplifier 303 includes a comparison circuit 310, a current mirror circuit 323, and a bit line voltage control transistor N1.
- the current mirror circuit 323 includes a PMOS transistor P1, a PMOS transistor P2, and a constant current circuit 330.
- the source terminals of the PMOS transistor P1 and the PMOS transistor P2 of the current mirror circuit 323 are connected to the power supply, the gate terminals are connected to each other, and the drain terminal of the PMOS transistor P1 and one of the constant current circuit 330 are connected to each other. Connected to the terminal.
- the other terminal of the constant current circuit 330 is grounded.
- the drain terminal of the PMOS transistor P2 is connected to one input terminal (for example, + terminal) of the comparison circuit 310 and the drain terminal of the bit line voltage control transistor N1.
- the gate terminal of the bit line voltage control transistor N1 is connected to the output terminal of the bit line control voltage switching circuit 400, and the source terminal of the bit line voltage control transistor N1 is connected to the bit line selection circuit via the terminal BLIN of the read circuit 206. 204 is connected.
- the other terminal (eg, ⁇ terminal) of the comparison circuit 310 is connected to the terminal SAREF of the readout circuit 206, and the output terminal of the comparison circuit 310 is connected to the data signal input / output circuit via the output terminal SAOUT of the readout circuit 206. It is connected to 207 and outputs data to the outside.
- the voltage applied to the gate terminal of the bit line voltage control transistor N1 is supplied from the voltage source VPP1 or the voltage source VPP2.
- the voltage source VPP1 generates a read clamp voltage Vcr shown in (Expression 1)
- the voltage source VPP2 generates a cell characteristic determination clamp voltage Vct shown in (Expression 2).
- the bit line control voltage switching circuit 400 is composed of switches SW1 and SW2. One terminal of the switch SW1 of the bit line control voltage switching circuit 400 is connected to the voltage source VPP1, and one terminal of the switch SW2 is connected to the voltage source VPP2. The other terminals of the switches SW1 and SW2 are connected to each other, and are connected to the gate terminal of the bit line voltage control transistor N1 of the sense amplifier 303. In the normal read mode of the sense amplifier 303, the bit line control voltage switching circuit 400 outputs the read clamp voltage Vcr of the voltage source VPP1 to the gate terminal of the transistor N1 by turning SW1 on and SW2 off.
- SW1 is turned off and SW2 is turned on to output the cell characteristic determination clamp voltage Vct of the voltage source VPP2 to the gate terminal of the bit line voltage control transistor N1. That is, the bit line control voltage switching circuit 400 applies the read clamp voltage Vcr to the gate terminal of the bit line voltage control transistor N1 of the sense amplifier 303 in the normal read mode, and applies the cell characteristic determination clamp voltage Vct in the cell characteristic determination mode. Apply.
- the voltage applied to the bit line does not exceed a voltage lower than the voltage applied to the gate terminal of the bit line voltage control transistor N1 by the threshold voltage Vtn of the transistor N1.
- the bit line voltage Vblr applied to the line and the bit line voltage Vblt applied to the bit line in the cell characteristic determination mode can be expressed by (Equation 3) and (Equation 4), respectively. By using it, the state of the memory cell can be detected with higher accuracy.
- FIG. 28 is a circuit diagram showing an example of the configuration of the readout circuit 206 in the present embodiment.
- the read circuit 206 shown in FIG. 28 includes a sense amplifier 304, a bit line control voltage switching circuit 400, and a bit line control voltage generation circuit 507.
- the bit line control voltage generation circuit 507 includes a voltage source VPP and a reference current control element RD15.
- the voltage source VPP outputs a read clamp voltage Vcr from the output terminal OUT1 of the bit line control voltage generation circuit 507.
- the voltage source VPP is connected to one terminal of the reference current control element RD15.
- the other terminal of the reference current control element RD15 is connected to the output terminal OUT2 of the bit line control voltage generation circuit 507, and the reference current control element RD15 outputs a cell characteristic determination clamp voltage Vct.
- the voltage source VPP may be incorporated in a nonvolatile memory device or supplied from an external power source.
- the sense amplifier 304 includes a comparison circuit 310, a current mirror circuit 323, an NMOS transistor (bit line voltage control transistor) N1, an NMOS transistor (bit line precharge transistor) N10, and a bit line voltage detection circuit 680. ing.
- the current mirror circuit 323 includes a PMOS transistor P1, a PMOS transistor P2, and a constant current circuit 330. The source terminals of the PMOS transistor P1 and the PMOS transistor P2 of the current mirror circuit 323 are connected to the power supply, the gate terminals are connected to each other, and the drain terminal of the PMOS transistor P1 and one of the constant current circuit 330 are connected to each other. Connected to the terminal. The other terminal of the constant current circuit 330 is grounded.
- the drain terminal of the PMOS transistor P2 is connected to one input terminal (for example, + terminal) of the comparison circuit 310 and the drain terminal of the bit line voltage control transistor N1.
- the gate terminal of the bit line voltage control transistor N1 is connected to the gate terminal of the bit line precharge transistor N11 and to the output terminal BDOUT of the bit line voltage detection circuit 680.
- the source terminal of the bit line voltage control transistor N1 is connected to the bit line selection circuit 204 via the terminal BLIN of the read circuit 206, and the source terminal of the bit line precharge transistor N10 and the bit line voltage detection circuit 680 It is connected to the input terminal BDIN.
- the drain terminal of the bit line precharge transistor N10 is connected to the power supply voltage.
- the other terminal (for example, ⁇ terminal) of the comparison circuit 310 is connected to the terminal SAREF of the readout circuit 206, and the output terminal of the comparison circuit 310 is input to the data signal via the output terminal SAOUT of the readout circuit 206. It is connected to the output circuit 207 and outputs data to the outside.
- the bit line voltage detection circuit 680 is an inverter element composed of a PMOS transistor P10 and an NMOS transistor N13.
- the source terminal of the PMOS transistor P10 is connected to the bit line control voltage switching circuit 400 via the terminal VDDBD of the bit line voltage detection circuit 680.
- the gate terminal of the PMOS transistor P10 is grounded.
- the drain terminal of the PMOS transistor P10 is connected to the output terminal BDOUT of the bit line voltage detection circuit 680 and to the drain terminal of the NMOS transistor N13.
- the gate terminal of the NMOS transistor N13 is connected to the input terminal BDIN of the bit line voltage detection circuit 680, and the source terminal of the NMOS transistor N13 is grounded.
- the bit line control voltage switching circuit 400 is composed of switches SW1 and SW2. One terminal of the switch SW1 of the bit line control voltage switching circuit 400 is connected to the output terminal OUT1 of the bit line control voltage generation circuit 507, and one terminal of the switch SW2 is the output terminal OUT2 of the bit line control voltage generation circuit 507. Connected with. The other terminals of the switches SW1 and SW2 are connected to each other and to the terminal VDDBD of the bit line voltage detection circuit 680 of the sense amplifier 304.
- the bit line control voltage generation circuit 507 includes a voltage source VPP and a reference current control element RD15.
- the voltage source VPP generates a read clamp voltage Vcr expressed by (Equation 1), and outputs the read clamp voltage Vcr via the output terminal OUT1 of the bit line control voltage generation circuit 507.
- One terminal of the reference current control element RD15 is connected to the voltage source VPP, and the other terminal is connected to the output terminal OUT2 of the bit line control voltage generation circuit 507, so that the cell characteristic determination shown in (Expression 2) is performed.
- a clamp voltage Vct is generated.
- the cell characteristic determination clamp voltage Vct output from the output terminal OUT2 of the bit line control voltage generation circuit 507 is reduced by the threshold voltage VF ′ ′′ of the reference current control element RD15 from the read clamp voltage Vcr output from the output terminal OUT1. Become a voltage.
- the bit line control voltage switching circuit 400 In the normal read mode of the sense amplifier 304, the bit line control voltage switching circuit 400 outputs the read clamp voltage Vcr to the terminal VDDBD of the bit line voltage detection circuit 680 by turning SW1 on and SW2 off. In the cell characteristic determination mode, the cell characteristic determination clamp voltage Vct is output to the terminal VDDBD of the bit line voltage detection circuit 680 by turning SW1 off and SW2 on.
- the bit line voltage detection circuit 680 detects the potential of the bit line at the input terminal BDIN via the terminal BLIN of the sense amplifier 304.
- the NMOS transistor N13 is turned off, and the voltage supplied from the terminal VDDBD is supplied to the bit line voltage control transistor N1 via the output terminal BDOUT.
- the NMOS transistor N13 When the potential of the bit line exceeds the threshold voltage of the bit line voltage detection circuit 680, the NMOS transistor N13 is turned on, and the voltage at the output terminal BDOUT of the bit line voltage detection circuit 680 decreases, thereby controlling the bit line voltage control.
- the transistor N1 and the bit line precharge transistor N10 are turned off. That is, when the potential of the bit line is equal to or lower than the threshold voltage of the bit line voltage detection circuit 680, the bit line can be precharged to a predetermined potential at high speed by the bit line precharge transistor N10.
- the voltage applied to the bit line is precharged to a predetermined potential by the bit line precharge transistor N10, so that the state of the memory cell can be detected at high speed.
- a bidirectional diode is used as the current control element provided in the memory cell.
- the current control element is not limited to the above example, and may be a unidirectional diode.
- a unidirectional diode is used as a current control element, in the failure detection step for detecting a defective memory cell, if the memory cell is normal, no current flows through the memory cell when a current is passed in the reverse direction.
- a memory cell having a short circuit failure is included, a current flows through the defective memory cell. Therefore, the memory cell may be defective when a current flows in the opposite direction. With such a configuration, a defective memory cell can be detected.
- bit line or word line having a defective memory cell can be detected in units of bit lines or word lines. Further, when a current failure detection circuit is provided for both the bit line and the word line, it is possible to detect a defective memory cell connected between the selected bit line and the word line.
- the current control element and the resistance change element may be connected in the opposite upper and lower connection relation, or the upper and lower connection relation between the first resistance change layer and the second resistance change layer.
- the upper and lower connection relations of the lower electrode and the upper electrode may be reversed.
- the non-selected bit lines BL1 and BL3 and the non-selected word lines WL1 and WL3 are in a high impedance state.
- the present invention is not limited to this, and between the selected bit line BL2 and the selected word line WL2 You may set to the voltage value below the voltage applied to.
- the materials of the upper electrode, the lower electrode, the first variable resistance layer, and the second variable resistance layer in the above embodiment are merely examples, and other materials may be used.
- the metal oxide layer of the resistance change element has a laminated structure of tantalum oxide, the above-described effects of the present invention are manifested only when the metal oxide layer is tantalum oxide.
- the variable resistance element may be of any other configuration or material as long as it is an element that reversibly transits at least two resistance values.
- bidirectional current control element is described as the current control element in the above embodiment, a unidirectional diode may be used.
- the current control element in the above embodiment may be a PN diode, a Schottky diode, or a Zener diode.
- variable resistance nonvolatile memory device having a cross-point configuration detects an address of a defective memory cell of a memory cell using a current control element having bidirectional characteristics, and detects the defective memory. By performing cell relief, it is useful for realizing a highly reliable memory.
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Abstract
Description
以下、本発明の詳細を説明する前に、本発明の基礎となった知見について説明する。
[メモリセル]
図1は、本発明の第1の実施の形態におけるメモリセルの構成図の一例である。図1に示すメモリセル10は、直列に接続された電流制御素子20と抵抗変化素子30とで構成されている。
図4は、本実施の形態において、電流制御素子20が正常な特性を持つメモリセル10と、電流制御素子20が不良な特性(ショート不良)を持つメモリセル10の電圧電流特性を示す図である。図1の下部配線50と上部配線51によって選択されたメモリセル10に対し、下部配線50よりも上部配線51が高い電圧となる極性を正の電圧とする。上部配線51から下部配線50に流れる電流の向きを正の電流方向としたときに、第1の低抵抗状態を持つ正常なメモリセル10に印加される正の電圧と電流は、特性(1)で示されるように、メモリセル10に印加される電圧の絶対値が約2.6V以下では、メモリセル10にはほとんど電流が流れないが、2.6Vを超えると、メモリセル10に電流が流れ、印加される電圧の増加とともに流れる電流は非線形的に増加する。
図5は、第1の実施の形態における抵抗変化型不揮発性記憶装置200の構成図を示すものである。図5に示すように、本実施の形態に係る抵抗変化型不揮発性記憶装置200は、基板上にメモリ本体部201を備えている。メモリ本体部201は、メモリセルアレイ202と、ワード線選択回路203と、ビット線選択回路204と、データの書き込みを行うための書き込み回路205と、データの読み出しを行うための読み出し回路206と、データ信号入出力回路207とを備えている。
Vct = Vre + Vtn ・・・(式2)
Vblt ≦ Vre ・・・(式4)
Iblr ≒ Iselr ・・・(式6)
(b) Inselr(b):M12→M13→M23
(c) Inselr(c):M32→M31→M21
(d) Inselr(d):M32→M33→M23
ΣInselr = Inselr(a) + Inselr(b)
+Inselr(c) + Inselr(d)・・・(式7)
図11は、本実施の形態のメモリセルアレイ202における電流パスを説明するための回路図である。説明を簡素化するために、前述した図5のメインメモリセルアレイ600を3×3に配置した場合の回路図で、メモリセルM22を選択する場合についての一例を示している。また、図12は、図11の等価回路図である。
Iblt ≒ Iselt ・・・(式9)
次に、本実施の形態におけるメモリセルの救済方法について述べる。
次に、本発明の第2の実施の形態における抵抗変化型不揮発性記憶装置について説明をする。
次に、本発明の第3の実施の形態における抵抗変化型不揮発性記憶装置について説明をする。
次に第4の実施の形態について説明する。
次に、本発明の第5の実施の形態における抵抗変化型不揮発性記憶装置について説明をする。
次に、本発明の第6の実施の形態における抵抗変化型不揮発性記憶装置について説明をする。
次に、本発明の第7の実施の形態における抵抗変化型不揮発性記憶装置について説明をする。
Vct1 = Vr1 + Vtn (式11)
Vct2 = Vr2 + Vtn (式12)
Vblt1 ≦ Vre1 (式14)
Vblt2 ≦ Vre2 (式15)
次に、本発明の第8の実施の形態における抵抗変化型不揮発性記憶装置について説明をする。
次に、本発明の第9の実施の形態における抵抗変化型不揮発性記憶装置について説明をする。
20、101 電流制御素子
21 電流制御素子の下部電極(第1の電極)
22 電流制御素子の半導体層
23 電流制御素子の上部電極(第2の電極)
30、102 抵抗変化素子
31 抵抗変化素子の下部電極(第3の電極)
32 抵抗変化素子の第1の抵抗変化層
33 抵抗変化素子の第2の抵抗変化層
34 抵抗変化素子の上部電極(第4の電極)
35 抵抗変化素子の抵抗変化層
50 下部配線
51 上部配線
200 抵抗変化型不揮発性記憶装置
201 メモリ本体部
202、232、242、252 メモリセルアレイ
203 ワード線選択回路(メモリセル選択回路)
204 ビット線選択回路(メモリセル選択回路)
205 書き込み回路
206 読み出し回路
207 データ信号入出力回路
208 アドレス信号入力回路
209 制御回路
210 書き込み用電源
211 低抵抗化用電源
212 高抵抗化用電源
213 不良アドレス記憶回路
214 アドレス比較回路
300 センスアンプ
310 比較回路(検知回路)
320 カレントミラー回路
330 定電流回路
400 ビット線制御電圧切り替え回路
500 ビット線制御電圧発生回路
600、601 メインメモリセルアレイ
602 非選択メモリセルアレイ
610、620、630、640 冗長メモリセルアレイ
650a、650b、650c、650d メインメモリセルアレイ
660a、660b、660c、660d 冗長メモリセルアレイ
670a、670b、670c、670d 冗長メモリセルアレイ
680 ビット線電圧検知回路(電圧検知回路)
680a、680b、680c、680d メインメモリセルアレイ
690a、690b、700a、700b 冗長メモリセルアレイ
700 HR書き込み回路
710 第1HR書き込み回路
720 第2HR書き込み回路
800 LR書き込み回路
BL1、BL2、BL3 ビット線
BLR1 冗長ビット線
D11、D12、D13 電流制御素子
D21、D22、D23 電流制御素子
D31、D32、D33 電流制御素子
M11、M12、M13 メモリセル
M21、M22、M23 メモリセル
M31、M32、M33 メモリセル
R11、R12、R13 抵抗変化素子
R21、R22、R23 抵抗変化素子
R31、R32、R33 抵抗変化素子
WL1、WL2、WL3 ワード線
WLR1 冗長ワード線
Claims (25)
- 印加される電圧パルスに応じて可逆的に抵抗値が遷移する抵抗変化素子と、前記抵抗変化素子と直列に接続され、印加電圧が所定の閾値電圧を超えると導通状態とみなされる電流が流れる電流制御素子とで構成される複数のメモリセルを有し、複数のワード線と複数のビット線との立体交差点のそれぞれに、前記複数のメモリセルの1つが配置されたメモリセルアレイと、
前記複数のワード線から少なくとも1つを選択し、前記複数のビット線から少なくとも1つを選択することにより、前記メモリセルアレイから少なくとも1つ以上の前記メモリセルを選択するメモリセル選択回路と、
前記選択されたメモリセルに電圧パルスを印加することによって、前記選択されたメモリセルの前記抵抗変化素子の抵抗値を書き換える書き込み回路と、
前記選択されたメモリセルの前記電流制御素子に前記閾値電圧より高い第1電圧、または、前記閾値電圧以下の第2電圧が印加されるように、前記選択されたメモリセルに電圧を印加することによって、前記選択されたメモリセルの状態を読み出す読み出し回路と、を備え、
前記書き込み回路は、前記電圧パルスとして第1の低抵抗化パルス、または、第1の高抵抗化パルスを前記選択されたメモリセルに印加することにより、前記複数のメモリセルのうち選択されたメモリセルの前記抵抗変化素子をそれぞれ第1の低抵抗状態、または、第1の高抵抗状態にし、
前記読み出し回路は、前記選択されたメモリセルに前記第1電圧を印加して前記選択されたメモリセルの前記抵抗変化素子の抵抗状態を読み出し、
前記読み出し回路は、前記選択されたメモリセルの前記抵抗変化素子の抵抗状態を読み出すときに、前記選択されたメモリセルに所定値以上の電流が流れるならば、前記選択されたメモリセルがショート不良を有する不良メモリセルであると判定し、
前記書き込み回路は、前記不良メモリセルと同一のビット線上および前記不良メモリセルと同一のワード線上の少なくともいずれかに配置されている前記不良メモリセル以外の他のメモリセルに対して、前記他のメモリセルの抵抗変化素子を前記第1の高抵抗状態の抵抗値以上の抵抗値を示す第2の高抵抗状態にするように第2の高抵抗化パルスを印加する
抵抗変化型不揮発性記憶装置。 - 前記書き込み回路は、前記不良メモリセルの前記抵抗変化素子を前記第1の低抵抗状態の抵抗値以上の抵抗値を示す第3の高抵抗状態にするように、前記不良メモリセルの前記抵抗変化素子に、前記抵抗変化素子が高抵抗化を開始するパルス電圧の絶対値以上の電圧の絶対値を有する第3の高抵抗化パルスを印加する
請求項1に記載の抵抗変化型不揮発性記憶装置。 - 前記読み出し回路は、前記選択されたメモリセルに前記第2電圧を印加して、前記所定値以上の電流が流れるとき、前記選択されたメモリセルがショート不良を有する不良メモリセルであると判定する
請求項1または2に記載の抵抗変化型不揮発性記憶装置。 - 前記書き込み回路により前記不良メモリセルに対して前記第3の高抵抗化パルスを印加した後、前記読み出し回路は、再度、前記不良メモリセルに所定値以上の電流が流れるか否かを検知し、前記選択されたメモリセルに前記所定値以上の電流が流れるとき、前記不良メモリセルの前記抵抗変化素子が前記第3の高抵抗状態の抵抗値以上になっていないと判定する
請求項2に記載の抵抗変化型不揮発性記憶装置。 - 前記不良メモリセルの前記抵抗変化素子が前記第3の高抵抗状態の抵抗値よりも低い抵抗値になっていれば、前記書き込み回路は、前記不良メモリセルの前記抵抗変化素子が前記第3の高抵抗状態の抵抗値以上になるか、または、所定の回数まで前記第3の高抵抗化パルスを繰り返し印加する
請求項4に記載の抵抗変化型不揮発性記憶装置。 - 前記不良メモリセルの前記抵抗変化素子が前記第3の高抵抗状態の抵抗値よりも低い抵抗値になっていれば、前記書き込み回路は、前記不良メモリセルの前記抵抗変化素子が前記第3の高抵抗状態の抵抗値以上になるか、または、所定の回数まで、前記第3の高抵抗化パルス条件と異なる第4の高抵抗化パルスを、2回目以降繰り返し印加する
請求項4に記載の抵抗変化型不揮発性記憶装置。 - 前記第4の高抵抗化パルスの電圧値は、前記第3の高抵抗化パルスの電圧値よりも絶対値が大きい電圧である
請求項6に記載の抵抗変化型不揮発性記憶装置。 - 前記第4の高抵抗化パルスの電流値は、前記第3の高抵抗化パルスの電流値よりも大きい
請求項6に記載の抵抗変化型不揮発性記憶装置。 - 前記第4の高抵抗化パルスのパルス幅は、前記第3の高抵抗化パルスのパルス幅よりも大きい
請求項6に記載の抵抗変化型不揮発性記憶装置。 - 前記書き込み回路は、前記不良メモリセルの前記抵抗変化素子の抵抗値が前記第3の高抵抗状態の抵抗値よりも低いときに、前記不良メモリセルと同一のビット線上および前記不良メモリセルと同一のワード線上の少なくともいずれかに配置されている前記不良メモリセル以外の他のメモリセルの抵抗変化素子に、前記第1の高抵抗状態よりも抵抗値の高い前記第2の高抵抗状態にするように前記第2の高抵抗化パルスを印加する
請求項2に記載の抵抗変化型不揮発性記憶装置。 - 前記抵抗変化素子の前記第3の高抵抗状態の抵抗値は、前記第1の高抵抗状態の抵抗値以上である
請求項1~10のいずれか1項に記載の抵抗変化型不揮発性記憶装置。 - 前記抵抗変化素子の前記第3の高抵抗状態の抵抗値は、前記第1の高抵抗状態の抵抗値の10倍以上である
請求項1~11のいずれか1項に記載の抵抗変化型不揮発性記憶装置。 - 前記不良メモリセルの抵抗変化素子の前記第2の高抵抗状態の抵抗値は、前記第1の高抵抗状態の抵抗値の10倍以上である
請求項1~12のいずれか1項に記載の抵抗変化型不揮発性記憶装置。 - 前記メモリセルアレイは、
主記憶用の前記メモリセルを複数備えたメインメモリセルアレイと、
前記メインメモリセルアレイ中の少なくとも1つの前記メモリセルが不良メモリセルの場合に、前記不良メモリセルと置換して使用するための冗長メモリセルを複数備えた冗長メモリセルアレイとを備えている
請求項1~13のいずれか1項に記載の抵抗変化型不揮発性記憶装置。 - 前記抵抗変化型不揮発性記憶装置は、
前記不良メモリセルのアドレス情報と前記冗長メモリセルのアドレス情報とを対応付けて記憶する不良アドレス記憶回路を備える
請求項14に記載の抵抗変化型不揮発性記憶装置。 - 前記不良アドレス記憶回路は、
前記不良メモリセルを有するビット線およびワード線の少なくともいずれかのアドレスと、
前記不良メモリセルと置換する前記冗長メモリセルを有する、前記ビット線に対応するビット線および前記ワード線に対応するワード線の少なくともいずれかのアドレスと、
を対応付けて記憶する
請求項15に記載の抵抗変化型不揮発性記憶装置。 - 前記抵抗変化型不揮発性記憶装置は、
前記書き込み回路に低抵抗化電圧を供給する低抵抗電源と、前記書き込み回路に高抵抗化書き込み電圧を供給する高抵抗電源とを有する書き込み用電源を備える
請求項1~16のいずれか1項に記載の抵抗変化型不揮発性記憶装置。 - 印加される電圧パルスに応じて可逆的に抵抗値が遷移する抵抗変化素子と、前記抵抗変化素子と直列に接続され、印加電圧が所定の閾値電圧を超えると導通状態とみなされる電流が流れる電流制御素子とで構成される複数のメモリセルを有し、複数のワード線と複数のビット線との立体交差点のそれぞれに、前記複数のメモリセルの1つが配置されたメモリセルアレイを備えた抵抗変化型不揮発性記憶装置の駆動方法であって、
書き込み回路により、前記複数のメモリセルのうち選択されたメモリセルに第1の低抵抗化パルス、または、第1の高抵抗化パルスを印加することで、前記選択されたメモリセルの前記抵抗変化素子をそれぞれ第1の低抵抗状態、または、第1の高抵抗状態にする書き込みステップと、
読み出し回路により、前記選択されたメモリセルに前記閾値電圧より高い第1電圧を印加して前記選択されたメモリセルの前記抵抗変化素子の抵抗状態を読み出す読み出しステップと、
前記選択されたメモリセルの抵抗状態を読み出すときに、前記選択されたメモリセルに所定値以上の電流が流れるならば、前記選択されたメモリセルがショート不良を有している不良メモリセルであると判定する不良検知ステップと、
前記書き込み回路により、前記不良メモリセルと同一のビット線上および前記不良メモリセルと同一のワード線上の少なくともいずれかに配置されている前記不良メモリセル以外の他のメモリセルに対して、前記他のメモリセルの抵抗変化素子を前記第1の高抵抗状態の抵抗値以上の抵抗値を示す第2の高抵抗状態にするように第2の高抵抗化パルスを印加する、他のメモリセル高抵抗化ステップとを含む
抵抗変化型不揮発性記憶装置の駆動方法。 - 前記不良検知ステップの後に、
前記書き込み回路により、前記不良メモリセルの前記抵抗変化素子を前記第1の低抵抗状態の抵抗値以上の抵抗値を示す第3の高抵抗状態にするように、前記不良メモリセルの前記抵抗変化素子に、前記抵抗変化素子が高抵抗化を開始するパルス電圧の絶対値以上の電圧の絶対値を有する第3の高抵抗化パルスを印加する、不良メモリセル高抵抗化ステップを含む
請求項18に記載の抵抗変化型不揮発性記憶装置の駆動方法。 - 前記不良検知ステップにおいて、前記読み出し回路は、前記選択されたメモリセルに前記閾値電圧より低い第2電圧を印加して、前記所定値以上の電流が流れるとき、前記選択されたメモリセルがショート不良を有する不良メモリセルであると判定する
請求項18または19に記載の抵抗変化型不揮発性記憶装置の駆動方法。 - 前記不良メモリセルに対して、前記不良メモリセル高抵抗化ステップを実施した後に、再度、前記不良検知ステップを行い、前記不良メモリセルに所定値以上の電流が流れるか否かを検知し、前記選択されたメモリセルに前記所定値以上の電流が流れるとき、前記不良メモリセルの前記抵抗変化素子が第3の高抵抗状態の抵抗値以上になっていないと判定する不良メモリセル高抵抗化チェックステップをさらに含む
請求項19に記載の抵抗変化型不揮発性記憶装置の駆動方法。 - 前記不良メモリセル高抵抗化チェックステップで、前記不良メモリセルの前記抵抗変化素子が第3の高抵抗状態の抵抗値よりも低い抵抗値になっていれば、再度、不良メモリセル高抵抗化ステップを行い、前記不良メモリセルの前記抵抗変化素子が第3の高抵抗状態の抵抗値以上になるか、または、所定の回数まで繰り返す
請求項21に記載の抵抗変化型不揮発性記憶装置の駆動方法。 - 前記不良メモリセル高抵抗化ステップを行う際に、2回目以降の不良メモリセル高抵抗化チェックステップの書き込み条件を変更する
請求項22に記載の抵抗変化型不揮発性記憶装置の駆動方法。 - 前記メモリセルアレイは、
主記憶用の前記メモリセルを複数備えたメインメモリセルアレイと、
前記メインメモリセルアレイ中の少なくとも1つ以上の前記メモリセルが不良メモリセルの場合に、前記メインメモリセルアレイ中の前記不良メモリセルと置換して使用するための冗長メモリセルを複数備えた冗長メモリセルアレイとを備え、
前記抵抗変化型不揮発性記憶装置は、
前記不良メモリセルのアドレス情報と前記冗長メモリセルのアドレス情報とを対応付けて不良アドレス記憶回路に記憶し、
メモリ動作時において、前記不良メモリセルにアクセスしたときに、前記不良アドレス記憶回路を参照して前記冗長メモリセルにアクセスする
請求項18~23のいずれか1項に記載の抵抗変化型不揮発性記憶装置の駆動方法。 - 不良メモリセル高抵抗化チェックステップにおいて前記不良メモリセルの前記抵抗変化素子が第3の高抵抗状態の抵抗値以上になっていると判定された場合に、前記不良メモリセルのアドレス情報を前記不良アドレス記憶回路に記憶する救済ステップをさらに含む
請求項24に記載の抵抗変化型不揮発性記憶装置の駆動方法。
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