Semiconductor storage device
A semiconductor storage device includes: a cell array including a plurality of first wirings, a plurality of second wirings intersecting the first wirings, and memory cells positioned at intersecting portions between the first wirings and the second wirings, each of the memory cells having a series circuit of a non-ohmic element and a variable resistance element; a control circuit configured to apply a control voltage, which is necessary for the variable resistance element to transit from a low resistance state to a high resistance state, to the memory cells through the first wirings and the second wirings; and a bias voltage application circuit configured to apply a bias voltage, which suppresses a potential variation caused by the transition of the variable resistance element from the low resistance state to the high resistance state, to one end of the variable resistance element.
1. A semiconductor storage device comprising:
a cell array including a plurality of first wirings, a plurality of second wirings intersecting the first wirings, and memory cells positioned at intersecting portions between the first wirings and the second wirings, each of the memory cells having a series circuit of a non-ohmic element and a variable resistance element;
a control circuit configured to apply a control voltage, which is necessary for the variable resistance element to transit from a low resistance state to a high resistance state, to the memory cells through the first wirings and the second wirings; and
a bias voltage application circuit configured to apply a bias voltage, which suppresses a potential variation caused by the transition of the variable resistance element from the low resistance state to the high resistance state, to one end of the variable resistance element.
2. The semiconductor storage device according to claim 1 , wherein the bias voltage application circuit comprises:
a dummy wiring intersecting the first or second wirings;
dummy memory cells positioned at intersecting portions between the first or second wirings and the dummy wiring, each of the dummy memory cells having a resistance element having a resistance lower than that of the variable resistance element in the high resistance state; and
a dummy wiring control circuit configured to apply a dummy wiring control voltage to the dummy memory cells through the dummy wiring when the control circuit applies the control voltage to the memory cells.
3. The semiconductor storage device according to claim 2 , wherein the bias voltage application circuit comprises:
a constant current circuit configured to supply a constant current to the dummy wiring as the control circuit applies the control voltage to the memory cells;
a sampling circuit configured to be sampling a potential on the dummy wiring side of the dummy memory cells just after the constant current circuit supplies the constant current to the dummy wiring; and
an amplifying circuit configured to keep the potential on the dummy wiring side sampled by the sampling circuit as the dummy wiring control voltage during a period in which the memory cells are applied with the control voltage.
4. The semiconductor storage device according to claim 2 , wherein the bias voltage application circuit outputs a voltage, which is larger than a voltage obtained by subtracting a voltage necessary for the memory cells to transit from the high resistance state to the low resistance state from the control voltage applied to the memory cells by the control circuit, as the dummy wiring control voltage.
5. The semiconductor storage device according to claim 2 , wherein the bias voltage application circuit keeps the dummy wiring control voltage by increasing a current flowing to the dummy wiring when the memory cells transit from the low resistance state to the high resistance state.
6. The semiconductor storage device according to claim 2 , wherein the dummy memory cells are disposed in end portions of the cell array.
7. The semiconductor storage device according to claim 2 , wherein the dummy memory cells are disposed by being dispersed in the cell arrays.
8. The semiconductor storage device according to claim 2 , wherein the dummy memory cells are memory cells permanently placed in a low resistance state by breaking the variable resistance element of each of the memory cells.
9. A semiconductor storage device comprising:
a cell array including a plurality of first wirings, a plurality of second wirings intersecting the first wirings, and memory cells positioned at intersecting portions between the first wirings and the second wirings, each of the memory cells having a series circuit of a non-ohmic element and a variable resistance element;
a control circuit configured to apply a control voltage, which is necessary for the variable resistance element to transit from a low resistance state to a high resistance state, to the memory cells through the first wirings and the second wirings; and
a bias voltage application circuit configured to apply a bias voltage, which suppresses a potential variation caused by the transition of the variable resistance element from the low resistance state to the high resistance state, to one end of the variable resistance element,
the bias voltage application circuit applying the bias voltage so that the voltage applied to the memory cells through the first wirings and the second wirings when the variable resistance element transits to the high resistance state is made smaller than a voltage necessary for the memory cells to transit from the high resistance state to the low resistance state.
10. The semiconductor storage device according to claim 9 , wherein the bias voltage application circuit comprises:
a dummy wiring intersecting the first or second wirings;
dummy memory cells positioned at intersecting portions between the first or second wirings and the dummy wiring, each of the dummy memory cells having a resistance element having a resistance lower than that of the variable resistance element in the high resistance state; and
a dummy wiring control circuit configured to apply a dummy wiring control voltage to the dummy memory cells through the dummy wiring when the control circuit applies the control voltage to the memory cells.
11. The semiconductor storage device according to claim 10 , wherein the bias voltage application circuit comprises:
a constant current circuit configured to supply a constant current to the dummy wiring as the control circuit applies the control voltage to the memory cells;
a sampling circuit configured to be sampling a potential on the dummy wiring side of the dummy memory cells just after the constant current circuit supplies the constant current to the dummy wiring; and
an amplifying circuit configured to keep the potential on the dummy wiring side sampled by the sampling circuit as the dummy wiring control voltage during a period in which the memory cells are applied with the control voltage.
12. The semiconductor storage device according to claim 10 , wherein the bias voltage application circuit outputs a voltage, which is larger than a voltage obtained by subtracting a voltage necessary for the memory cells to transit from the high resistance state to the low resistance state from the control voltage applied to the memory cells by the control circuit, as the dummy wiring control voltage.
13. The semiconductor storage device according to claim 10 , wherein the bias voltage application circuit keeps the dummy wiring control voltage by increasing a current flowing to the dummy wiring when the memory cells transit from the low resistance state to the high resistance state.
14. The semiconductor storage device according to claim 10 , wherein the dummy memory cells are disposed in end portions of the cell array.
15. The semiconductor storage device according to claim 10 , wherein the dummy memory cells are disposed by being dispersed in the cell arrays.
16. The semiconductor storage device according to claim 10 , wherein the dummy memory cells are memory cells permanently placed in a low resistance state by breaking the variable resistance element of each of the memory cells.
17. A semiconductor storage device comprising:
a cell array including a plurality of first wirings, a plurality of second wirings intersecting the first wirings, and memory cells positioned at intersecting portions between the first wirings and the second wirings, each of the memory cells having a series circuit of a non-ohmic element and a variable resistance element;
a control circuit configured to apply a control voltage, which is necessary for the variable resistance element to transit from a low resistance state to a high resistance state, to the memory cells through the first wirings and the second wirings; and
a bias voltage application circuit configured to apply a bias voltage, which suppresses a potential variation caused by the transition of the variable resistance element from the low resistance state to the high resistance state, to one end of the variable resistance element,
the bias voltage application circuit comprising:
a dummy wiring intersecting the first or second wirings;
dummy memory cells positioned at intersecting portions between the first or second wirings and the dummy wiring, each of the dummy memory cells having a resistance element having a resistance lower than that of the variable resistance element in the high resistance state; and
a dummy wiring control circuit configured to apply a dummy wiring control voltage to the dummy memory cells through the dummy wiring when the control circuit applies the control voltage to the memory cells, and
the bias voltage application circuit keeping the dummy wiring control voltage before and after transition of a resistance state of the variable resistance element.
18. The semiconductor storage device according to claim 17 , wherein the bias voltage application circuit comprises:
a constant current circuit configured to supply a constant current to the dummy wiring as the control circuit applies the control voltage to the memory cells;
a sampling circuit configured to be sampling a potential on the dummy wiring side of the dummy memory cells just after the constant current circuit supplies the constant current to the dummy wiring; and
an amplifying circuit configured to keep the potential on the dummy wiring side sampled by the sampling circuit as the dummy wiring control voltage during a period in which the memory cells are applied with the control voltage.
19. The semiconductor storage device according to claim 17 , wherein the bias voltage application circuit outputs a voltage, which is larger than a voltage obtained by subtracting a voltage necessary for the memory cells to transit from the high resistance state to the low resistance state from the control voltage applied to the memory cells by the control circuit, as the dummy wiring control voltage.
20. The semiconductor storage device according to claim 17 , wherein the bias voltage application circuit keeps the dummy wiring control voltage by increasing a current flowing to the dummy wiring when the memory cells transit from the low resistance state to the high resistance state.