Variable resistance nonvolatile memory element writing method and variable resistance nonvolatile memory device
First Claim
1. A variable resistance nonvolatile memory element writing method of, by applying a voltage pulse to a memory cell including a variable resistance nonvolatile memory element, reversibly changing the variable resistance nonvolatile memory element between a first resistance state and a second resistance state according to a polarity of the applied voltage pulse,wherein the variable resistance nonvolatile memory element includes a first electrode, a second electrode, and a variable resistance layer placed between the first electrode and the second electrode,the variable resistance layer includes an oxygen-deficient first transition metal oxide layer that is in contact with the first electrode, and a second transition metal oxide layer that is in contact with the second electrode and is lower in oxygen deficiency than the first transition metal oxide layer, andthe variable resistance nonvolatile memory element has characteristics of changing to the first resistance state when, with respect to one of the first electrode and the second electrode, a first voltage pulse having a positive potential and equal to or more than a first threshold voltage is applied to an other one of the first electrode and the second electrode, and changing to the second resistance state when, with respect to the other one of the first electrode and the second electrode, a second voltage pulse having a positive potential and equal to or more than a second threshold voltage is applied to the one of the first electrode and the second electrode,the variable resistance nonvolatile memory element writing method comprisingduring a writing operation, successively applying a first voltage pulse set and a memory cell value measurement a plurality of times, the first voltage pulse set including a first preliminary voltage pulse and the first voltage pulse, wherein in the first voltage pulse set, the first voltage pulse is applied to the variable resistance nonvolatile memory element subsequent to the first preliminary voltage pulse when changing the variable resistance nonvolatile memory element from the second resistance state to the first resistance state, such that a value of the memory cell changes in accordance with each successive application of the first voltage pulse set, the first preliminary voltage pulse being smaller in voltage absolute value than the second threshold voltage and different in polarity from the first voltage pulse.
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Abstract
A variable resistance nonvolatile memory element writing method of, by applying a voltage pulse to a memory cell including a variable resistance element, reversibly changing the variable resistance element between a first resistance state and a second resistance state according to a polarity of the applied voltage pulse is provided. The variable resistance nonvolatile memory element writing method includes applying a first preliminary voltage pulse and subsequently applying the first voltage pulse to the variable resistance element to change the variable resistance element from the second resistance state to the first resistance state, the first preliminary voltage pulse being smaller in voltage absolute value than the second threshold voltage and different in polarity from the first voltage pulse.
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Citations
18 Claims
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1. A variable resistance nonvolatile memory element writing method of, by applying a voltage pulse to a memory cell including a variable resistance nonvolatile memory element, reversibly changing the variable resistance nonvolatile memory element between a first resistance state and a second resistance state according to a polarity of the applied voltage pulse,
wherein the variable resistance nonvolatile memory element includes a first electrode, a second electrode, and a variable resistance layer placed between the first electrode and the second electrode, the variable resistance layer includes an oxygen-deficient first transition metal oxide layer that is in contact with the first electrode, and a second transition metal oxide layer that is in contact with the second electrode and is lower in oxygen deficiency than the first transition metal oxide layer, and the variable resistance nonvolatile memory element has characteristics of changing to the first resistance state when, with respect to one of the first electrode and the second electrode, a first voltage pulse having a positive potential and equal to or more than a first threshold voltage is applied to an other one of the first electrode and the second electrode, and changing to the second resistance state when, with respect to the other one of the first electrode and the second electrode, a second voltage pulse having a positive potential and equal to or more than a second threshold voltage is applied to the one of the first electrode and the second electrode, the variable resistance nonvolatile memory element writing method comprising during a writing operation, successively applying a first voltage pulse set and a memory cell value measurement a plurality of times, the first voltage pulse set including a first preliminary voltage pulse and the first voltage pulse, wherein in the first voltage pulse set, the first voltage pulse is applied to the variable resistance nonvolatile memory element subsequent to the first preliminary voltage pulse when changing the variable resistance nonvolatile memory element from the second resistance state to the first resistance state, such that a value of the memory cell changes in accordance with each successive application of the first voltage pulse set, the first preliminary voltage pulse being smaller in voltage absolute value than the second threshold voltage and different in polarity from the first voltage pulse.
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16. A variable resistance nonvolatile memory device comprising:
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a memory cell including a variable resistance nonvolatile memory element; and a write control unit configured to, by applying a voltage pulse to the memory cell, perform writing for reversibly changing the variable resistance nonvolatile memory element between a first resistance state and a second resistance state according to a polarity of the applied voltage pulse, wherein the variable resistance nonvolatile memory element includes a first electrode, a second electrode, and a variable resistance layer placed between the first electrode and the second electrode, the variable resistance layer includes an oxygen-deficient first transition metal oxide layer that is in contact with the first electrode, and a second transition metal oxide layer that is in contact with the second electrode and is lower in oxygen deficiency than the first transition metal oxide layer, the variable resistance nonvolatile memory element has characteristics of changing to the first resistance state when, with respect to one of the first electrode and the second electrode, a first voltage pulse having a positive potential and equal to or more than a first threshold voltage is applied to an other one of the first electrode and the second electrode, and changing to the second resistance state when, with respect to the other one of the first electrode and the second electrode, a second voltage pulse having a positive potential and equal to or more than a second threshold voltage is applied to the one of the first electrode and the second electrode, and the write control unit is configured to, during a writing operation, successively apply a first voltage pulse set and a memory cell value measurement a plurality of times, the first voltage pulse set including a first preliminary voltage pulse and the first voltage pulse, wherein in the first voltage pulse set, the first voltage pulse is applied to the variable resistance nonvolatile memory element subsequent to the first preliminary voltage pulse when changing the variable resistance nonvolatile memory element from the second resistance state to the first resistance state, such that a value of the memory cell changes in accordance with each successive application of the first voltage pulse set, the first preliminary voltage pulse being smaller in voltage absolute value than the second threshold voltage and different in polarity from the first voltage pulse. - View Dependent Claims (17, 18)
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Specification