CN102568596A - Method for reducing flash memory threshold voltage distribution range - Google Patents
Method for reducing flash memory threshold voltage distribution range Download PDFInfo
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- CN102568596A CN102568596A CN2012100060291A CN201210006029A CN102568596A CN 102568596 A CN102568596 A CN 102568596A CN 2012100060291 A CN2012100060291 A CN 2012100060291A CN 201210006029 A CN201210006029 A CN 201210006029A CN 102568596 A CN102568596 A CN 102568596A
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Abstract
The invention discloses a method for reducing a flash memory threshold voltage distribution range, and belongs to the flash memory circuit design technical field. The method comprises the following steps that: 1) an erasing pulse is applied on all memory units of the flash memory; 2) whether the threshold voltage of all memory units of the flash memory is lower than a first preset value Vr1 is judged through erasing verification operation; and 3) Vd is controlled by adjusting and controlling Vstep, and the Vd is reduced along with the increasing of the Vstep. The method has beneficial effects that: a distribution range of the threshold voltage of the memory unit after the erasing operation can be effectively reduced, a memory space of data can be enlarged, and the flash memory can be used as an image sensor to be used in the field requiring storing multi-bit simulation values.
Description
Technical field
The invention belongs to the flash memory circuit design field, particularly a kind of method that reduces flash memory threshold voltage distribution scope.
Background technology
Flash memory has a wide range of applications, such as portable electric appts such as camera, MP3.Flash memory generally all can be carried out erase operation before data write; And for fear of the retention performance (Retention) that erase state (Over Erase) occurred and guaranteed data, system design all can be controlled through the threshold voltage distribution of algorithm after to the flash memory cell erase operation.Flash memory based on multidigit storage (Multi-Level Cell) especially need be controlled the threshold voltage distribution behind the erase operation.Existed algorithms mainly receives the restriction of running time at present; Threshold voltage through erase operation control store unit is lower than certain preset value and guarantees that through the soft programming operation storage unit can not be in erase status and get final product; The threshold voltage distribution scope of not being strict with storage unit is enough narrow, and its threshold voltage distribution synoptic diagram is as shown in Figure 1.And under special cases; Store such as the multidigit analogue value; Or even need store flash memory in the occasion of the multidigit analogue value more as image sensor etc.; Time, data retention characteristics to erase operation are not strict with, but require the threshold voltage distribution scope after the cell erase operation very narrow.
Summary of the invention
The present invention is directed to above-mentioned defective and disclose a kind of method that reduces flash memory threshold voltage distribution scope, the present invention is that a kind of high precision is wiped algorithm, can effectively reduce the distribution range of storage unit threshold voltage behind the erase operation.
A kind of method that reduces flash memory threshold voltage distribution scope may further comprise the steps:
1) at first all storage unit of flash memory is applied erasing pulse, with the threshold voltage of all storage unit of reducing flash memory;
2) operate the threshold voltage of judging all storage unit of flash memory through erase verification then and whether be lower than the first preset value Vr1; If not; Need once more storage unit to be applied erasing pulse; If explain that then the threshold voltage of all storage unit has been lower than the first preset value Vr1;
3) storage unit is applied the soft programming operation to improve the threshold voltage of storage unit; This soft programming controls the voltage Vw size that is added to the storage unit grid and satisfies following condition: Vw-Vr1=Vstep; Thereby make the threshold voltage of storage unit converge to the second preset value Vr2 gradually through behind the programming operation of special time; Vr1-Vr2=Vd wherein; And Vd is exactly the distribution range of storage unit threshold voltage behind the erase operation, controls the size of Vd through adjusting the size of controlling Vstep, and Vd reduces along with the increase of Vstep.
The scope of said special time is: 100 microseconds are to 500 microseconds.
Beneficial effect of the present invention is: can effectively reduce the distribution range of storage unit threshold voltage behind the erase operation, enlarge the storage space of data, help flash memory need be stored in the occasion of the multidigit analogue value more as image sensor etc.
Description of drawings
Fig. 1 for existing wipe with programming operation after storage unit threshold voltage distribution synoptic diagram.
The erase operation algorithm synoptic diagram that Fig. 2 proposes for the present invention.
In the soft programming operating process of Fig. 3 for the present invention's proposition, storage unit threshold voltage variation synoptic diagram.
Fig. 4 for the erase operation algorithm that adopts the present invention and propose after storage unit threshold voltage distribution synoptic diagram.
Embodiment
Below in conjunction with accompanying drawing, preferred embodiment is elaborated.Should be emphasized that following explanation only is exemplary, rather than in order to limit scope of the present invention and application thereof.
The present invention proposes a kind of high precision and wipe algorithm, can effectively reduce the distribution range of storage unit threshold voltage behind the erase operation.
As shown in Figure 2, a kind of method that reduces flash memory threshold voltage distribution scope may further comprise the steps:
1) at first all storage unit of flash memory is applied erasing pulse, with the threshold voltage of all storage unit of reducing flash memory;
2) operate the threshold voltage of judging all storage unit of flash memory through erase verification then and whether be lower than the first preset value Vr1 (such as 1.5V); If not; Need once more storage unit to be applied erasing pulse; If explain that then the threshold voltage of all storage unit has been lower than the first preset value Vr1;
3) but this moment storage unit threshold voltage distribution very wide (such as 0.5V to 1.5V); Need then storage unit to be applied the soft programming operation to improve the threshold voltage of storage unit; The convergence that the operation of this soft programming utilizes storage unit long-time (such as 100 microseconds to 500 microseconds) programming operation to have; Voltage Vw (such as the 4V) size that strict control is added to the storage unit grid satisfies following condition: Vw-Vr1=Vstep; Thereby make the threshold voltage of storage unit through converging to the second preset value Vr2 (such as 1V) gradually behind the programming operation of special time, Vr1-Vr2=Vd wherein, and Vd is exactly the distribution range of storage unit threshold voltage behind the erase operation; Control the size of Vd through adjusting the size of controlling Vstep, Vd reduces along with the increase of Vstep.
Fig. 3 is in the soft programming operating process, storage unit threshold voltage variation synoptic diagram.Fig. 4 is the distribution schematic diagram of storage unit threshold voltage behind the erase operation, can see that the distribution range of threshold voltage is very narrow.
Claims (2)
1. method that reduces flash memory threshold voltage distribution scope is characterized in that it may further comprise the steps:
1) at first all storage unit of flash memory is applied erasing pulse, with the threshold voltage of all storage unit of reducing flash memory;
2) operate the threshold voltage of judging all storage unit of flash memory through erase verification then and whether be lower than the first preset value Vr1; If not; Need once more storage unit to be applied erasing pulse; If explain that then the threshold voltage of all storage unit has been lower than the first preset value Vr1;
3) storage unit is applied the soft programming operation to improve the threshold voltage of storage unit; This soft programming controls the voltage Vw size that is added to the storage unit grid and satisfies following condition: Vw-Vr1=Vstep; Thereby make the threshold voltage of storage unit converge to the second preset value Vr2 gradually through behind the programming operation of special time; Vr1-Vr2=Vd wherein; And Vd is exactly the distribution range of storage unit threshold voltage behind the erase operation, controls the size of Vd through adjusting the size of controlling Vstep, and Vd reduces along with the increase of Vstep.
2. a kind of method that reduces flash memory threshold voltage distribution scope according to claim 1, it is characterized in that the scope of said special time is: 100 microseconds are to 500 microseconds.
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| CN2012100060291A CN102568596A (en) | 2012-01-10 | 2012-01-10 | Method for reducing flash memory threshold voltage distribution range |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104064222A (en) * | 2013-03-20 | 2014-09-24 | 华邦电子股份有限公司 | Verification apparatus for flash memory |
| CN104751898A (en) * | 2013-12-30 | 2015-07-01 | 北京兆易创新科技股份有限公司 | NOR(Not or) type FLASH data recovery method |
| CN109859792A (en) * | 2018-12-25 | 2019-06-07 | 北京大学 | A kind of threshold voltage distribution forecasting method and device |
| CN110176269A (en) * | 2019-04-16 | 2019-08-27 | 华中科技大学 | A kind of method and system of accuracy controlling non-volatile memory cells state |
| CN114283864A (en) * | 2021-11-19 | 2022-04-05 | 成都博尔微晶科技有限公司 | Memory unit erasing method and device, electronic equipment and storage medium |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101083137A (en) * | 2006-06-02 | 2007-12-05 | 恩益禧电子股份有限公司 | Nonvolatile semiconductor memory device and method of testing thereof |
| CN101329915A (en) * | 2007-06-19 | 2008-12-24 | 三星电子株式会社 | Method for programming the storing device |
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2012
- 2012-01-10 CN CN2012100060291A patent/CN102568596A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101083137A (en) * | 2006-06-02 | 2007-12-05 | 恩益禧电子股份有限公司 | Nonvolatile semiconductor memory device and method of testing thereof |
| CN101329915A (en) * | 2007-06-19 | 2008-12-24 | 三星电子株式会社 | Method for programming the storing device |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104064222A (en) * | 2013-03-20 | 2014-09-24 | 华邦电子股份有限公司 | Verification apparatus for flash memory |
| CN104751898A (en) * | 2013-12-30 | 2015-07-01 | 北京兆易创新科技股份有限公司 | NOR(Not or) type FLASH data recovery method |
| CN104751898B (en) * | 2013-12-30 | 2018-04-24 | 北京兆易创新科技股份有限公司 | The method of NOR type FLASH data recoveries |
| CN109859792A (en) * | 2018-12-25 | 2019-06-07 | 北京大学 | A kind of threshold voltage distribution forecasting method and device |
| CN109859792B (en) * | 2018-12-25 | 2021-05-04 | 北京大学 | Threshold voltage distribution prediction method and device |
| CN110176269A (en) * | 2019-04-16 | 2019-08-27 | 华中科技大学 | A kind of method and system of accuracy controlling non-volatile memory cells state |
| CN110176269B (en) * | 2019-04-16 | 2020-11-17 | 华中科技大学 | Method and system for accurately regulating and controlling state of nonvolatile storage unit |
| CN114283864A (en) * | 2021-11-19 | 2022-04-05 | 成都博尔微晶科技有限公司 | Memory unit erasing method and device, electronic equipment and storage medium |
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Application publication date: 20120711 |