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

• US 6,788,564 B2
• Filed: 03/26/2003
• Issued: 09/07/2004
• Est. Priority Date: 03/27/2002
• Status: Expired due to Fees

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Hamada, Yasuaki
• Primary Examiner(s): PHAN, TRONG Q
• Application Number:
  US10/396,372
• Publication Number:
  US 20040109363A1
• Time in Patent Office: 531 Days
• Field of Search: 365/145, 365/149
• US Class Current: 365/145
• CPC Class Codes: G11C 11/22 using ferroelectric elements

Abstract

The invention provides a ferroelectric storage apparatus which can reduce or prevent disturbance, a driving method therefor, and a driving circuit therefor. 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 among a plurality of ferroelectric memory cells formed at the intersections of a plurality of word lines and a plurality of bit lines is repeatedly performed. 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 is performed after the operation step is executed at least once. With this, a voltage is applied to not-selected cells at a certain frequency in an electric-field direction in which the stored data of the not-selected cells is not inverted, and data deterioration is reduced or suppressed.

Claims

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

first 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

second 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 first applying is executed at least once.

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

further including forming each of the plurality of ferroelectric memory cells is formed of a ferroelectric capacitor only.

3. The driving method for a ferroelectric storage apparatus, according to claim 1, the first applying including applying

one of a first-polarity selection voltage and a second-polarity selection voltage to the at least one selected cell, and applying one or both of a first-polarity non-selection voltage and a second-polarity non-selection voltage to not-selected cells;

and

the second applying including alternately applying the first-polarity non-selection voltage and the second-polarity non-selection voltage to each of the plurality of ferroelectric memory cells.

4. A ferroelectric storage apparatus, 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 intersections of the plurality of word lines and the plurality of bit lines;

a word-line driver to drive the plurality of word lines; and

a bit-line driver to drive the plurality of bit lines,

the word-line driver and the bit-line driver applying 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 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, during a disturbance prevention mode performed after the operation mode is performed at least once.

5. The ferroelectric storage apparatus according to claim 4,

each of the plurality of ferroelectric memory cells being formed of a ferroelectric capacitor only.

6. The ferroelectric storage apparatus according to claim 4,

the word-line driver and the bit-line driver applying, 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 applying 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, applying the first-polarity non-selection voltage and the second-polarity non-selection voltage alternately to each of the plurality of ferroelectric memory cells.

7. The ferroelectric storage apparatus according to claim 6,

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

and

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

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

8. The ferroelectric storage apparatus according to claim 7,

the word-line driver and the bit-line driver setting 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. The ferroelectric storage apparatus according to claim 5,

further including a counter to count the number of times the operation mode is performed, and the word-line driver and the bit-line driver performing the disturbance prevention mode according to the output of the counter.

10. The ferroelectric storage apparatus according to claim 5,

the word-line driver being connected to N word lines, the bit-line driver being connected to M bit lines, a total of N-by-M ferroelectric memory cells being disposed, and the word-line driver and the bit-line driver performing the operation mode when at least one effective address in the N-by-M ferroelectric memory cells is selected, and performing 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, the driving circuit comprising:

a word-line driver to drive the plurality of word lines; and

a plurality of bit-line drivers to drive the plurality of bit lines,

the word-line driver and the bit-line drivers applying 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 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, during a disturbance prevention mode performed after the operation mode is performed at least once.