Ferroelectric storage apparatus, driving method therefor, and driving circuit therefor

• US 20040109363A1
• Filed: 03/26/2003
• Published: 06/10/2004
• Est. Priority Date: 03/27/2002
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Hamada, Yasuaki
• Granted Patent: US 6,788,564 B2
• Time in Patent Office: Days
• US Class Current: 365/200
• CPC Class Codes: G11C 11/22 using ferroelectric elements

Abstract

A ferroelectric storage apparatus which can prevent disturbance, a driving method therefor, and a driving circuit therefor are provided. In the ferroelectric storage apparatus, an operation step of applying one of data reading, data re-writing, and data writing to at least one selected cell 18a among a plurality of ferroelectric memory cells 18 formed at the intersections of a plurality of word lines 14 and a plurality of bit lines 16 is repeatedly performed. A disturbance prevention step of applying a voltage to each of the plurality of ferroelectric memory cells 18 in an electric-field direction in which the stored data of each ferroelectric memory cell 18 is not inverted is performed after the operation step is executed at least once. With this, a voltage is applied to not selected cells 18b at a certain frequency in an electric-field direction in which they stored data of the not-selected cells is not inverted, and data deterioration is suppressed.

Claims

1. A driving method for a ferroelectric storage apparatus, characterized by comprising:

an operation step of applying one of data reading, data re-writing, and data-writing to at least one-selected cell among, a plurality of ferroelectric memory cells formed at the intersections of a plurality of word lines and a plurality of bit lines; and

a disturbance prevention step of applying a voltage to each of the plurality of ferroelectric memory cells in an electric-field direction in which the stored data of each ferroelectric memory cell is not inverted, after the operation step is executed at least once.

2. A driving method for a ferroelectric storage apparatus, according to claim 1,

characterized in that each of the plurality of ferroelectric, memory cells is formed of a ferroelectric capacitor only.

3. A driving method for a ferroelectric storage apparatus, according to claim 1 or 2,

characterized in that, in the operation step, one of a first-polarity selection voltage and a second-polarity selection voltage is applied to the at least one selected cell, and one or both of a first-polarity non-selection voltage and a, second-polarity non-selection voltage is applied to not-selected cells;

and

in the disturbance prevention step, the first-polarity non-selection voltage and the second-polarity non-selection voltage are alternately applied to each of the plurality of ferroelectric memory cells.

4. A ferroelectric storage apparatus characterized by comprising:

a plurality of word lines disposed in parallel to each other;

a plurality of bit lines disposed in parallel to each other and intersecting with the plurality of word lines;

a plurality of ferroelectric memory cells formed at the intersections of the plurality of word lines and the plurality of bit lines;

a word-line driver for driving the plurality of word lines; and

a bit-line driver for driving the plurality of bit lines, and

characterized in that the word-line driver and the bit-line driver apply an operation mode of one of data reading, data re-writing, and data writing to at least one selected cell among the plurality of ferroelectric memory cells, and apply a voltage to each of the plurality of ferroelectric memory, cells in an electric-field direction in which the stored data of each ferroelectric memory cell is not inverted, during a disturbance prevention mode performed after the operation mode is performed at least once.

5. A ferroelectric storage apparatus according to claim 4,

characterized in that each of the plurality of ferroelectric memory cells is formed of a ferroelectric capacitor only.

6. A ferroelectric storage apparatus according to claim 4 or 5,

characterized in that the word-line driver and the bit-line driver apply, in the operation mode, one of the first-polarity selection voltage and the second-polarity selection-voltage to the at least one selected cell, and apply one or both of a first-polarity non-selection voltage and a second-polarity non-selection voltage to not-selected cells;

and

in the disturbance prevention mode, apply the first-polarity non-selection voltage and the second-polarity non-selection voltage alternately to each of the plurality of ferroelectric memory cells.

7. A ferroelectric storage apparatus according to claim 6,

characterized in that, in the operation mode, the word-line driver supplies one of two types of selection potentials to a word line connected to the at least one selected cell, and supplies one of two types of non-selection potentials to word lines connected to the not-selected cells, and the bit-line driver-supplies the other of the two types of selection potentials to a bit line connected to the at least, one selected cell, and supplies the other of the two types of non-selection potential to bit lines connected to the not-selected cells;

the disturbance prevention mode is divided into a first zone and a second zone;

in the first zone, the word-line driver supplies one of the two types of non-selection potentials to the plurality of word lines, and the bit-line driver supplies the other of the two types of non-selection potentials to the plurality of bit lines; and

in the second zone, the word-line driver supplies the other of the two types of non-selection potentials to the plurality of word lines, and the bit-line driver supplies the one of the two types of non-selection potentials to the plurality of bit lines.

8. A ferroelectric storage apparatus according to claim 7,

characterized in that the word-line driver and the bit-line driver set the plurality of word lines-and the plurality of bit lines to the same potential during a third zone provided between the first zone and the second zone.

9. A ferroelectric storage apparatus according to one of claims 5 to 8,

characterized by further comprising a counter for counting the number of times the operation mode is performed, and characterized in that the word-line driver and the bit-line driver perform the disturbance prevention mode according to the output of the counter.

10. A ferroelectric storage apparatus according to one of claims 5 to 8,

characterized in that the word-line driver is connected to N word lines, the bit-line driver is connected to M bit lines, a total of N-by-M ferroelectric memory cells are, disposed, and the word-line driver and the bit-line driver perform the operation made when at least one effective address in the N-by-M ferroelectric memory cells is selected, and perform the disturbance prevention mode when a dummy address other than the effective address is selected.

11. A driving circuit connected to a ferroelectric storage section provided with a plurality of ferroelectric memory cells formed at the intersections of a plurality of word lines and a plurality of bit lines, characterized by comprising:

a word-line driver for driving the plurality of word lines; and

a plurality of bit-line drivers for driving the plurality of bit lines, and

characterized in that the word-line driver and the bit-line drivers apply an operation mode of one of data reading, data re-writing, and data writing to at least one selected cell among the plurality of ferroelectric memory cells, formed at the intersections of the plurality of word lines and the plurality of bit lines, and-apply a voltage to each of the plurality of ferroelectric memory cells in an electric-field direction in which the stored data of each ferroelectric memory cell is not inverted, during a disturbance prevention mode performed after the operation mode is performed at least once.