Nonvolatile memory and writing method
AssigneeKioxia Corporation
InventorsTokumasa Hara, Noboru Shibata
Life of this patent
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Abstract
According to one embodiment, three bits stored in one memory cell of a nonvolatile memory correspond to three pages. In first page writing, a threshold voltage becomes within a first or second region base on a bit value. In second page writing, if being within the first region, it becomes within the first or fourth region; and if being within the second region, it becomes within the second or third region. In the third page writing, if being within the first region, it becomes within the first or sixth region; if being within the second region, it becomes within the second or seventh region; if being within the third region, it becomes within the third or eighth region; and if being within the fourth region, it becomes within the fourth or fifth region.
Claims18
A nonvolatile memory comprising:
- a word line;
- a plurality of memory cells connected to the word line, each of the plurality of memory cells being configured to store 3-bit data of first to third bits by eight threshold regions including a first threshold region indicating an erased state and second to eighth threshold regions having higher voltage levels than a voltage level of the first threshold region and indicating a written state, an n-th threshold region having a higher voltage level than an (n−1)-th threshold region of the eight threshold regions, n being a natural number of two or more and eight or less, the three bits respectively corresponding to first to third pages;
- and
- a control unit configured to:
- perform writing of the first page;
- perform writing of the second page after the writing of the first page is performed;
- perform writing of the third page after the writing of the second page is performed;
- when reading out data from the first page, read out the data using a fourth read voltage, the fourth read voltage being a boundary voltage between the fourth threshold region and the fifth threshold region, and determine data of the first page on a basis of the read out data;
- when reading out data from the second page, read out the data using a first, a third, and a sixth read voltage, the first read voltage being a boundary voltage between the first threshold region and the second threshold region, the third read voltage being a boundary voltage between the third threshold region and the fourth threshold region, the sixth read voltage being a boundary voltage between the sixth threshold region and the seventh threshold region, and determine data of the second page on a basis of the read out data;
- when reading out data from the third page, read out the data using a second, a fifth, and a seventh read voltage, the second read voltage being a boundary voltage between the second threshold region and the third threshold region, the fifth read voltage being a boundary voltage between the fifth threshold region and the sixth threshold region, the seventh read voltage being a boundary voltage between the seventh threshold region and the eighth threshold region, and determine data of the third page on a basis of the read out data, and
- during writing of the first page, the second page, and the third page to the plurality of memory cells:
- when reading out data from the first page before the writing of the third page is performed and after performing the writing of the second page, read out the data using the fourth read voltage, and determine data of the first page on a basis of the read out data, and
- when reading out data from the first page before the writing of the second page is performed and after performing the writing of the first page, read out the data using the fourth read voltage, and determine data of the first page on a basis of the read out data.
A method for controlling writing of a first page, a second page, and a third page to a nonvolatile memory including a plurality of memory cells connected to a word line, each of the plurality of memory cells being configured to store 3-bit data of first to third bits by eight threshold regions including a first threshold region indicating an erased state and second to eighth threshold regions having higher voltage levels than a voltage level of the first threshold region and indicating a written state, an n-th threshold region having a higher voltage level than an (n−1)-th threshold region of the eight threshold regions, n being a natural number of two or more and eight or less, the three bits respectively corresponding to the first to third pages, the method comprising:
- performing the writing of the first page;
- performing the writing of the second page after the writing of the first page is performed;
- performing the writing of the third page after the writing of the second page is performed;
- when reading out data from the first page, reading out the data using a fourth read voltage, the fourth read voltage being a boundary voltage between the fourth threshold region and the fifth threshold region, and determining data of the first page on a basis of the read out data;
- when reading out data from the second page, reading out the data using a first, a third, and a sixth read voltage, the first read voltage being a boundary voltage between the first threshold region and the second threshold region, the third read voltage being a boundary voltage between the third threshold region and the fourth threshold region, the sixth read voltage being a boundary voltage between the sixth threshold region and the seventh threshold region, and determining data of the second page on a basis of the read out data;
- when reading out data from the third page, reading out the data using a second, a fifth, and a seventh read voltage, the second read voltage being a boundary voltage between the second threshold region and the third threshold region, the fifth read voltage being a boundary voltage between the fifth threshold region and the sixth threshold region, the seventh read voltage being a boundary voltage between the seventh threshold region and the eighth threshold region, and determining data of the third page on a basis of the read out data,
- when reading out data from the first page before the writing of the third page is performed and after performing the writing of the second page, reading out the data using the fourth read voltage, and determining data of the first page on a basis of the read out data;
- and
- when reading out data from the first page before the writing of the second page is performed and after performing the writing of the first page, reading out the data using the fourth read voltage, and determining data of the first page on a basis of the read out data.
Dependencies are inferred from the claim text.