CN102543195A - Method and device for erasing nonvolatile memory - Google Patents
Method and device for erasing nonvolatile memory Download PDFInfo
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- CN102543195A CN102543195A CN2010106120808A CN201010612080A CN102543195A CN 102543195 A CN102543195 A CN 102543195A CN 2010106120808 A CN2010106120808 A CN 2010106120808A CN 201010612080 A CN201010612080 A CN 201010612080A CN 102543195 A CN102543195 A CN 102543195A
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Abstract
The invention provides a method and a device for erasing a nonvolatile memory. The method comprises the following steps of: erasing, namely performing erasing operation on all storage units in a target block; performing first soft programming verification, namely verifying whether threshold voltage of the storage units in the target block is higher than zero or not, if so, performing an erasing verification step, and otherwise, performing a first soft programming step; performing first soft programming, namely performing soft programming operation on the storage units in the target block to increase the threshold voltage of the storage units, and returning to the first soft programming verification step; and performing erasing verification, namely verifying whether the threshold voltage of all the storage units in the target block is lower than the upper limit of the threshold voltage in an erasing state or not, if so, stopping the operation, and otherwise, returning to the erasing step. By the method and the device, the threshold voltage of the storage units after the erasing operation can be accurately controlled, so that the threshold voltage of all the storage units can be kept in the erasing state.
Description
Technical field
The present invention relates to the semiconductor memory technologies field, particularly relate to a kind of method for deleting and device of nonvolatile memory.
Background technology
Along with electronic product is day by day popularized; Nonvolatile memory (for example; Flash memory Flash, or electro-erasable programmable ROM (read-only memory) EEPROM etc.) but because the data message in the reserved storage location still after the outage, become the main flow of semiconductor memory; It is widely used in the electronic product, like computing machine and digital communication equipment.
Nonvolatile memory has storage unit (cell) to form, cell can comprise source electrode (source, S), drain electrode (drain, D), grid (gate, G), and floating grid (floatinggate, FG), FG can be used for connecing voltage.(Flash Memory) is example with flash memory, and it adopts FN (Fowler-Nordheim) tunnel effect to realize programming and erase operation.When electronics is introduced in the floating gate of storage unit through the FN tunnel effect, be programming operation; When the electronics in the floating gate of storage unit is discharged into source electrode through the FN tunnel effect, be erase operation.Before in flash memory, Updating Information, must carry out erase operation to block, only wipe the back and can carry out the renewal of new data.
In the flash memory all storage unit wipe parallel carrying out, a piece (block comprises a plurality of cell) as long as in have storage unit not reach erase status, then need apply erasing pulse to whole block again.Owing to electron number on the floating gate of each storage unit among the block is all different, so each storage unit receives the influence of erasing pulse also different.Then when certain block applies erasing pulse, the electronics on the floating gate of each storage unit is also different to the number of source electrode migration, promptly some storage unit wipe comparatively fast, wiping of some storage unit is slower.Wipe the fastest with wipe the distribution range that the slowest storage unit has determined threshold voltage, both gaps are big more, the threshold voltage distribution scope is wide more.So; After the threshold voltage of most of storage unit is lower than reference value; The threshold voltage of wiping fast storage unit will be very low, possibly will be lower than the threshold voltage ranges (threshold voltage is lower than 0V) of erase status, thus the phenomenon that (over-erase) took place to wipe.
A kind of method that prevented erase status commonly used does, carries out behind the erase operation each storage unit being carried out stronger soft programming, promptly constantly applies programming pulse to storage, returns to normal erase status to the storage unit that was in erase status.Yet behind the erase operation, the threshold voltage distribution scope of each storage unit is wider, even through the soft programming operation, the threshold voltage that still also has partial memory cell is lower than 0V, can't return to normal erase status; Perhaps, through the soft programming operation, in each storage unit, the storage unit with lowest threshold voltage has returned to normal erase status, but the storage unit with higher preset voltage has exceeded normal erase status.
In a word; Need the urgent technical matters that solves of those skilled in the art to be exactly: method for deleting that how can nonvolatile memory; Can control the threshold voltage of storage unit behind the erase operation accurately, make the threshold voltage of each storage unit all can be in erase status.
Summary of the invention
Technical matters to be solved by this invention provides a kind of method for deleting and device of nonvolatile memory, can control the threshold voltage of storage unit behind the erase operation accurately, makes the threshold voltage of each storage unit all can be in erase status.
In order to address the above problem, the invention discloses a kind of method for deleting of nonvolatile memory, comprising:
Wipe: each storage unit in the object block is carried out erase operation;
The first soft programming verification: whether the threshold voltage of storage unit is all greater than zero in the verification object piece; If then carry out and wipe checking procedure; If not, then carry out first soft-program step;
First soft programming: operate the threshold voltage of the said storage unit of lifting through the storage unit in the said object block being carried out soft programming, and return the first soft programming checking procedure;
Wipe verification: whether the threshold voltage of each storage unit is all less than the threshold voltage upper limit of erase status in the checking object block; If, end operation then; If not, then return erase step.
Preferably, before said erase step, also comprise: pre-programmed: each storage unit in the object block is carried out the pre-programmed operation.
Preferably, the operation of said pre-programmed is specially: the word line to each storage unit in the object block applies positive voltage, and the threshold voltage of each storage unit is promoted to the 2nd
nIn the state corresponding threshold voltage range; Wherein, said cell stores n bit data has 2
nThe state of kind, the 2nd
nState corresponding threshold lower voltage limit is greater than all the other state corresponding threshold upper voltage limit.
Preferably, in the said first soft programming checking procedure, the threshold voltage of each storage unit of verification all after the threshold voltage upper limit less than erase status, also comprises:
The second soft programming verification: whether the threshold voltage of the storage unit on the verification selected word line is all greater than the threshold voltage lower limit of erase status; If then choose next word line to verify, up to the storage unit of having verified on all word lines, end operation; If not, then carry out second soft-program step;
Second soft programming: operate the threshold voltage of the said storage unit of lifting through the storage unit on the current selected word line being carried out soft programming, and return the second soft programming checking procedure.
Preferably, the said first soft programming checking procedure comprises: the voltage that applies on the word line with each storage unit is changed to zero; Detect the leakage current in each storage unit drain electrode successively; If leakage current is more than or equal to first reference current, then the threshold voltage of this storage unit is smaller or equal to zero; If leakage current is less than first reference current, then the threshold voltage of this storage unit is greater than zero.
Preferably, wipe in the checking procedure, choose each word line successively, each storage unit on this word line is verified, specifically comprise said:
Word line to choosing applies positive voltage;
To unchecked word line with its voltage zero setting; Perhaps, unchecked word line is applied the voltage of the minimum threshold voltage that is less than or equal to all unchecked storage unit;
Detect the leakage current in each storage unit drain electrode successively; If leakage current is greater than second reference current, then the threshold voltage of this storage unit is less than the threshold voltage upper limit of erase status; If leakage current is smaller or equal to second reference current, then the threshold voltage of this storage unit is more than or equal to the threshold voltage upper limit of erase status; Wherein, second reference current is less than first reference current.
Preferably, the said second soft programming checking procedure comprises:
Word line to choosing applies positive voltage;
To unchecked word line with its voltage zero setting; Perhaps, unchecked word line is applied the voltage of the minimum threshold voltage that is less than or equal to all unchecked storage unit;
Detect the leakage current in each storage unit drain electrode successively;
If leakage current is more than or equal to the 3rd reference current, then the threshold voltage of this storage unit is smaller or equal to the threshold voltage lower limit of erase status; If leakage current is less than the 3rd reference current, then the threshold voltage of this storage unit is greater than the threshold voltage lower limit of erase status; Wherein, the 3rd reference current is less than first reference current and greater than second reference current.
Accordingly, the invention also discloses a kind of erasing apparatus of nonvolatile memory, comprising:
Wipe module, be used for each storage unit of object block is carried out erase operation;
The first soft programming verification module, whether the threshold voltage that is used for verification object piece storage unit is all greater than zero; If then trigger and wipe the verification module; If not, then trigger the first soft programming module;
The first soft programming module is used for triggering the first soft programming verification module afterwards through the storage unit of said object block being carried out the threshold voltage of the said storage unit of soft programming operation lifting;
Wipe the verification module, whether the threshold voltage that is used for verifying each storage unit of object block is all less than the threshold voltage upper limit of erase status; If, end operation then; If not, then module is wiped in triggering.
Preferably, said device also comprises: the pre-programmed module, be used for before said erase step, and each storage unit in the object block is carried out the pre-programmed operation.
Preferably, the pre-programmed of said pre-programmed module operation is specially: the word line to each storage unit in the object block applies positive voltage, and the threshold voltage of each storage unit is promoted to the 2nd
nIn the state corresponding threshold voltage range; Wherein, said cell stores n bit data has 2
nThe state of kind, the 2nd
nState corresponding threshold lower voltage limit is greater than all the other state corresponding threshold upper voltage limit.
Preferably, said device also comprises:
The second soft programming verification module; Be used at the threshold voltage of said first each storage unit of soft programming calibration mode block check all after the threshold voltage upper limit less than erase status, whether the threshold voltage of the storage unit on the verification selected word line is all greater than the threshold voltage lower limit of erase status; If then choose next word line to verify, up to the storage unit of having verified on all word lines, end operation; If not, then trigger the second soft programming module;
The second soft programming module is used for operating the threshold voltage of the said storage unit of lifting through the storage unit on the current selected word line being carried out soft programming, and returns the second soft programming checking procedure.
Preferably, the said first soft programming verification module comprises:
The first pressurization submodule, the voltage that is used for applying on the word line with each storage unit is changed to zero;
First comparison sub-module is used for detecting successively the leakage current in each storage unit drain electrode; If leakage current is more than or equal to first reference current, then the threshold voltage of this storage unit is smaller or equal to zero; If leakage current is less than first reference current, then the threshold voltage of this storage unit is greater than zero.
Preferably, the said verification module of wiping is chosen each word line successively, and each storage unit on this word line is verified that it specifically comprises:
Wipe compression module, be used for the word line of choosing is applied positive voltage; And, unchecked word line with its voltage zero setting, is perhaps applied the voltage of the minimum threshold voltage that is less than or equal to all unchecked storage unit to unchecked word line;
Wipe comparison sub-module, be used for detecting successively the leakage current in each storage unit drain electrode; If leakage current is greater than second reference current, then the threshold voltage of this storage unit is less than the threshold voltage upper limit of erase status; If leakage current is smaller or equal to second reference current, then the threshold voltage of this storage unit is more than or equal to the threshold voltage upper limit of erase status; Wherein, second reference current is less than first reference current.
Preferably, the said second soft programming verification module comprises:
The first pressurization submodule is used for the word line of choosing is applied positive voltage; And, unchecked word line with its voltage zero setting, is perhaps applied the voltage of the minimum threshold voltage that is less than or equal to all unchecked storage unit to unchecked word line;
First comparison sub-module is used for detecting successively the leakage current in each storage unit drain electrode; If leakage current is more than or equal to the 3rd reference current, then the threshold voltage of this storage unit is smaller or equal to the threshold voltage lower limit of erase status; If leakage current is less than the 3rd reference current, then the threshold voltage of this storage unit is greater than the threshold voltage lower limit of erase status; Wherein, the 3rd reference current is less than first reference current and greater than second reference current.
Compared with prior art, the present invention has the following advantages:
The present invention carries out the first soft programming verification behind erase operation, if the threshold voltage that storage unit arranged in the verification object piece is smaller or equal to zero then carry out first soft programming, the threshold voltage of lifting storage unit, verification once more afterwards; When through the first soft programming verification, wipe verification, if the threshold voltage upper limit of the threshold voltage of storage unit more than or equal to erase status arranged in the object block, then return erase step, turn down the threshold voltage of storage unit, afterwards verification once more.Make each storage unit in the object block simultaneously through the first soft programming verification with wipe verification at last; Both can guarantee that threshold voltage was greater than zero; Can guarantee simultaneously the threshold voltage upper limit of threshold voltage again less than erase status; Can control the threshold voltage of storage unit behind the erase operation accurately through this method, make the threshold voltage of each storage unit all can be in erase status.
Further because the value of threshold voltage is prone to take place minor fluctuations, threshold voltage be zero or with zero comparatively near the time, its distribution is in the edge of erase status, is easy to the erase status that jumps out, and causes reading of state to be made mistakes.The present invention is through after wiping verification; Increased by the second soft programming verification; If the threshold voltage of storage unit is smaller or equal to the threshold voltage lower limit of the erase status that is provided with in advance on a certain word line, then carry out the threshold voltage of second this word line storage unit of soft programming lifting, owing to carry out soft programming to each word line respectively; Avoided in the object block threshold voltage lifting of all storage unit too high, guaranteed that again each storage unit can be in erase status accurately simultaneously.
Description of drawings
Fig. 1 is the process flow diagram of the method for deleting embodiment one of a kind of nonvolatile memory of the present invention;
Fig. 2 is the process flow diagram of the method for deleting embodiment two of a kind of nonvolatile memory of the present invention;
Fig. 3 is the threshold voltage distribution synoptic diagram of erase status in the embodiment of the invention two;
Fig. 4 is the structural drawing of the erasing apparatus embodiment one of a kind of nonvolatile memory of the present invention;
Fig. 5 is the structural drawing of the erasing apparatus embodiment two of a kind of nonvolatile memory of the present invention.
Embodiment
For make above-mentioned purpose of the present invention, feature and advantage can be more obviously understandable, below in conjunction with accompanying drawing and embodiment the present invention done further detailed explanation.
With reference to Fig. 1, show the process flow diagram of the method for deleting embodiment one of a kind of nonvolatile memory of the present invention, comprising:
Erase operation carries out whole object block, and the erase operation of each storage unit in the object block is parallel to carry out.As long as have storage unit not reach erase status in the object block, then need again to apply erasing pulse to whole, storage unit all in object block all reach erase status.
Step 102, the first soft programming verification: whether the threshold voltage of storage unit is all greater than zero in the verification object piece; If then execution in step 104 is wiped verification; If not, execution in step 103 first soft programmings then;
Because each is variant for the storage unit in the object block, each storage unit receives the influence of erasing pulse also different, and wiping of some storage unit is very fast; Wiping of some storage unit is slower; So through after wiping, the threshold voltage distribution wide range of each storage unit in the object block, the threshold voltage of some storage unit is low excessively; Even being lower than 0V, erase status promptly appearred.The said first soft programming verification is exactly for verification goes out the storage unit that whether occurred erase status in the object block, if then trigger the soft programming operation.The said first soft programming verification operation can compare the judgement acquisition through leakage current and the reference current of the cell on the detection of stored cell.
When having threshold voltage in the verification object piece smaller or equal to zero storage unit; Explanation has got into this storage unit through erase operation and crosses erase status; At this moment; Need carry out first soft programming, the threshold voltage of lifting storage unit, purpose is that the threshold voltage of storage unit is raised to more than zero.Need to prove, if the threshold voltage of verification some storage unit in object block smaller or equal to zero the time, then all carries out the operation of first soft programming to all storage unit in this object block.Carry out verification through returning the first soft programming checking procedure behind first soft programming again, the threshold voltage of all storage unit is all greater than till zero in object block.
Erase status is to there being the upper limit of a threshold voltage, if exceed this upper limit, then storage unit can change other state over to.For example, for SLC (Single Level Cell single-bit storage unit) flash memory, erase status storage data are " 1 "; If exceed the threshold voltage upper limit of erase status, get into next state, then store data and just become " 0 ".Therefore; After the first soft programming verification; When the threshold voltage of storage unit in the object block all greater than zero the time, though be not erase status, too high and get into other state for fear of threshold voltage; Then need further do and wipe verification, whether the threshold voltage of judging each storage unit is all less than the threshold voltage upper limit of erase status.If greater than the threshold voltage upper limit, then return step 101, carry out erase operation, reducing the threshold voltage of storage unit, and then execution in step 102 to the 104 first soft programming verification that each storage unit is all passed through in object block and wipe verification again.Need to prove, when returning step 101 and carrying out erase operation, to be storage unit all in the object block.If the threshold voltage of each storage unit all greater than prescribing a time limit on the threshold voltage, explains that then the threshold voltage of each storage unit satisfies greater than zero and less than the threshold voltage upper limit simultaneously, be in erase status, then end operation.
Method for deleting through the present invention's proposition; Make each storage unit in the object block simultaneously through the first soft programming verification with wipe verification; Both can guarantee that threshold voltage was greater than zero; Can guarantee again that simultaneously the threshold voltage upper limit of threshold voltage less than erase status, this method can control the threshold voltage of storage unit behind the erase operation accurately, make the threshold voltage of each storage unit all can be in erase status.
In a preferred embodiment of the invention, before said erase step, also comprise pre-programmed: each storage unit in the object block is carried out the pre-programmed operation.
Because erasing pulse is to be applied to simultaneously on the storage unit of whole object block; With the downward modulation of the threshold voltage of each storage unit, for the threshold voltage distribution that as far as possible makes all storage unit more concentrated, in a preferred embodiment of the invention; Carry out before the erase step; At first draw the threshold value of all storage unit to be that unanimity, usual way are to rise to roughly the same higher value to the threshold voltage of all storage unit through programming process, this process is called pre-programmed.
In the specific implementation, said pre-programmed is operating as: the word line to each storage unit in the object block applies positive voltage, and the threshold voltage of each storage unit is promoted to the 2nd
nIn the state corresponding threshold voltage range; Wherein, said cell stores n bit data has 2
nThe state of kind, the 2nd
nState corresponding threshold lower voltage limit is greater than all the other state corresponding threshold upper voltage limit.
For example; For storage 1 bit data SLC flash memory; Have 2 kinds of states; The threshold voltage lower limit of store status " 0 " is greater than the threshold voltage upper limit of store status " 1 " (also being erase status), then through pre-programmed with the threshold voltage of storage unit be promoted to the corresponding threshold voltage ranges of store status " 0 " in.And for example; MLC flash memory for the storage two bits; Have 4 kinds of states; The threshold voltage lower limit of store status " 00 " is all greater than the threshold voltage upper limit of store status " 11 " " 10 " " 01 ", then will through pre-programmed with the threshold voltage of storage unit be promoted to the corresponding threshold voltage ranges of store status " 00 " in.
With reference to Fig. 2, show the process flow diagram of the method for deleting embodiment two of a kind of nonvolatile memory of the present invention, comprising:
With MLC Flash Memory is example, and pre-programmed operation is that the cell to object block writes " 00 ", the stability of wiping with raising.Because wiping and being based on piece is unit, an object block has a plurality of cell, the threshold voltage V of each cell during beginning
TDifference, what have is in erase status, like V
TIn 0～2.5V scope; The PV1 state that is in that has (storage data " 10 ") is like V
TIn 2.7～3.7V scope; The PV2 state that is in that has (storage data " 01 ") is like V
TIn 3.9～5.3V scope; The PV3 state that is in that has (storage data " 00 ") is like V
TIn 5.5～6.9V scope.Then at first through the pre-programmed operation, the V of all cell
TAll adjust in 5.5～6.9V scope, make it be in the PV3 state.A kind of to the cell in the MLC Flash Memory object block write 00 (promptly cell being carried out pre-programmed) method can for: apply a higher voltage on the word line, more than 7～8V, a large amount of electronics injected floating grid FG, make V thereby make
TRise.
With MLC Flash Memory is example, and erase operation is meant through applying erasing pulse the cell in the current block is all write " 11 ".A kind ofly cell is write 11 method be: source and substrate in whole object block apply the voltage about 8.4V; Apply a lower negative voltage then on the word line WL of cell; As-8～-9V, and lasting a period of time, be 20ms like application time; The threshold value of all cell all can descend in the object block like this, and the target of wiping is the V with all cell
TDrop to below the 2.5V.
Step 203, the first soft programming verification: whether the threshold voltage of storage unit is all greater than zero in the verification object piece; If then execution in step 205 is wiped verification; If not, execution in step 204 first soft programmings then;
Because each cell receives the influence of erasing pulse different, so through after wiping, the V of some cell in the object block
TCross lowly, even be lower than 0V, erase status promptly occurred.Draw the cell that whether occurred erase status among the block through the first soft programming verification.
If occur the V of cell in the verification object piece
TSituation smaller or equal to zero is then carried out the soft programming operation.Common, in said first soft programming operation, the voltage on the word line of each cell being changed to zero, drain electrode applies positive voltage (soft programming pulse), and in order to promote threshold voltage faster, drain electrode applies bigger positive voltage usually, like 4V.Apply and return the first soft programming checking procedure again after a period of time and carry out verification, the V of all cell in object block
TAll greater than till zero.
Wipe in the checking procedure said, choose each word line successively, each cell on this word line is verified, if the V of cell is arranged on the selected word line
TThreshold voltage upper limit V greater than erase status
Upedge, then the cell on all word lines in the object block is carried out erase operation.
In the embodiment of the invention two, compare with embodiment one, increased by the second soft programming verification and second soft-program step.Through the first soft programming verification with wipe verification, the threshold voltage that can guarantee all cell in the object block is all greater than zero and less than the threshold voltage upper limit V of erase status
Upedge, but in practical application, minor fluctuations can take place in the value of threshold voltage, threshold voltage be zero or with zero comparatively near the time, its distribution is in the edge of erase status, is easy to the erase status that jumps out, and causes reading of state to be made mistakes.In order to guarantee that storage unit accurately is positioned at erase status, the threshold voltage lower limit V of an erase status is set in advance usually
Lower edge, this value is slightly larger than zero, is lower than V
Lower edgeStorage unit be regarded as non-erase status.V through verification cell
TWhether greater than V
Lower edgeTo guarantee that each cell is in erase status accurately.As shown in Figure 3, in the embodiment of the invention two, the threshold voltage distribution synoptic diagram of erase status.
Through second soft programming, the threshold voltage of the storage unit on the lifting selected word line, purpose is to make the threshold voltage lower limit of the threshold voltage of storage unit greater than erase status.Need to prove, carry out successively to each word line in the object block during the second soft programming verification, as cell being arranged on the wordline current not through verification, i.e. V
TSmaller or equal to V
Lower edge, then only carry out second soft programming, the threshold voltage of lifting cell to the cell on this word line; And then returning the second soft programming verification, each cell on this word line chooses next word line again and carries out the second soft programming verification all through the second soft programming verification.
Through the embodiment of the invention two; Make in the object block each storage unit simultaneously through the first soft programming verification, wipe the verification and the first soft programming verification; Both can guarantee the threshold voltage upper limit of threshold voltage less than erase status; Simultaneously can guarantee the threshold voltage lower limit of threshold voltage again, make each storage unit can be in erase status accurately greater than erase status.
Down in the face of the first soft programming verification, wipe verification and the second soft programming verification specifies.
The said first soft programming checking procedure specifically comprises:
A1, the voltage that applies on the word line with each storage unit are changed to zero;
A2 detects the leakage current in each storage unit drain electrode successively; If leakage current is more than or equal to first reference current, then the threshold voltage of this storage unit is smaller or equal to zero; If leakage current is less than first reference current, then the threshold voltage of this storage unit is greater than zero.
The threshold voltage of storage unit is big more, and then the leakage current of its generation is more little, and whether above-mentioned first reference current is threshold voltage is zero verification foundation.For example, when first reference current is 16uA, if the leakage current in the drain electrode, proves then that the threshold voltage of this storage unit is smaller or equal to zero more than or equal to 16uA.
Saidly wipe verification and specifically comprise:
B1 applies positive voltage to the word line of choosing;
B2, to unchecked word line with its voltage zero setting; Perhaps, unchecked word line is applied the voltage of the minimum threshold voltage that is less than or equal to all unchecked storage unit;
B3 detects the leakage current in each storage unit drain electrode successively; If leakage current is greater than second reference current, then the threshold voltage of this storage unit is less than the threshold voltage upper limit of erase status; If leakage current is smaller or equal to second reference current, then the threshold voltage of this storage unit is more than or equal to the threshold voltage upper limit of erase status; Wherein, second reference current is less than first reference current.
Positive voltage to the word line of choosing applies can confirm that the present invention does not limit according to the process condition of reality.For example, the positive voltage of the 3V that the word line of choosing is applied.Whether said second reference current is threshold voltage is the threshold voltage upper limit V of erase status
Up edgeThe verification foundation.Because the threshold voltage of storage unit is big more, leakage current is more little, so and V
Up edgeSecond reference current of (greater than 0V) correspondence is less than first reference current.For example, first reference current is 3uA, V
Up edgeBe 2.5V, if the drain electrode on leakage current greater than 3uA, the threshold voltage that then proves this storage unit is less than 2.5V.
The said second soft programming checking procedure specifically comprises:
C1 applies positive voltage to the word line of choosing;
C2, to unchecked word line with its voltage zero setting; Perhaps, unchecked word line is applied the voltage of the minimum threshold voltage that is less than or equal to all unchecked storage unit;
C3 detects the leakage current in each storage unit drain electrode successively; If leakage current is more than or equal to the 3rd reference current, then the threshold voltage of this storage unit is smaller or equal to the threshold voltage lower limit of erase status; If leakage current is less than the 3rd reference current, then the threshold voltage of this storage unit is greater than the threshold voltage lower limit of erase status; Wherein, the 3rd reference current is less than first reference current and greater than second reference current.
Positive voltage to the word line of choosing applies can confirm that the present invention does not limit according to the process condition of reality.For example, the positive voltage of the 2V that the word line of choosing is applied.Whether said the 3rd reference current is threshold voltage is the threshold voltage lower limit V of erase status
Lower edgeThe verification foundation.Because the threshold voltage of storage unit is big more, leakage current is more little; V
Lower edgeGreater than zero and less than V
Up edge, therefore the 3rd reference current is less than first reference current and greater than second reference current.For example, the 3rd reference current is 6uA, V
Lower edgeBe 0.6V, if the drain electrode on leakage current less than 6uA, the threshold voltage that then proves this storage unit is greater than 0.6V.
Above-mentioned in wiping the verification and the second soft programming checking procedure, apply threshold voltage V for the word line of unchecked storage unit smaller or equal to this unchecked storage unit
TVoltage, be that (bit line, the storage unit on BL) is directly received on the bit line through drain electrode, if the voltage on the grid of storage unit greater than threshold voltage, then can produce electric current because all bit lines.Because the voltage on the word line of storage unit is the voltage on the grid, therefore,, can avoid this storage unit on bit line, to produce leakage current if give the voltage that applies on the unchecked storage unit grid less than threshold voltage.
Further; Because the threshold voltage of unchecked storage unit is the different value in a scope; If the threshold voltage to each cell is all confirmed its voltage that applies, this just need measure all unchecked threshold voltages one by one, and this has increased workload and working time.Therefore; For for simplicity; Word line for unchecked storage unit applies a unified voltage, as long as this voltage is less than or equal to the minimum threshold voltage in all unchecked storage unit, just can guarantee that all unchecked storage unit all can not produce leakage current on bit line.For example; After a soft programming operation; The threshold voltage distribution scope of each storage unit is-2V～-2V; Apply for so the word line of unchecked all storage unit-2V or, can avoid producing on the bit line leakage current, guarantee for the validity of crossing the processing operation of wiping less than the voltage of-2V.
Need to prove, in wiping the verification and the second soft programming checking procedure, also can directly be directed against unchecked word line its voltage zero setting.Than the voltage that applies less than the minimum threshold voltage VT of all unchecked storage unit, directly zero setting does not obviously have aforesaid way effective, but it has made things convenient for operation.In the specific implementation, can be according to wiping the strict degree with soft programming verification effect requirements, suitable chooses wherein a kind of mode to not selected word line pressurization.
With reference to Fig. 4, show the structural drawing of the erasing apparatus embodiment one of a kind of nonvolatile memory of the present invention, comprising:
Wipe module 401, be used for each storage unit of object block is carried out erase operation;
The first soft programming verification module 402, whether the threshold voltage that is used for verification object piece storage unit is all greater than zero; If then trigger and wipe verification module 404; If not, then trigger the first soft programming module 403;
The first soft programming module 403 is used for triggering the first soft programming verification module 402 afterwards through the storage unit of said object block being carried out the threshold voltage of the said storage unit of soft programming operation lifting;
Wipe verification module 404, whether the threshold voltage that is used for verifying each storage unit of object block is all less than the threshold voltage upper limit of erase status; If, end operation then; If not, then module 401 is wiped in triggering.
Further, the said first soft programming verification module 403 comprises:
The first pressurization submodule, the voltage that is used for applying on the word line with each storage unit is changed to zero;
First comparison sub-module is used for detecting successively the leakage current in each storage unit drain electrode; If leakage current is more than or equal to first reference current, then the threshold voltage of this storage unit is smaller or equal to zero; If leakage current is less than first reference current, then the threshold voltage of this storage unit is greater than zero.
Further the said verification module 404 of wiping is chosen each word line successively, and each storage unit on this word line is verified that it specifically comprises:
Wipe compression module, be used for the word line of choosing is applied positive voltage; And, unchecked word line with its voltage zero setting, is perhaps applied the voltage of the minimum threshold voltage that is less than or equal to all unchecked storage unit to unchecked word line;
Wipe comparison sub-module, be used for detecting successively the leakage current in each storage unit drain electrode; If leakage current is greater than second reference current, then the threshold voltage of this storage unit is less than the threshold voltage upper limit of erase status; If leakage current is smaller or equal to second reference current, then the threshold voltage of this storage unit is more than or equal to the threshold voltage upper limit of erase status; Wherein, second reference current is less than first reference current.
With reference to Fig. 5, show the structural drawing of the erasing apparatus embodiment two of a kind of nonvolatile memory of the present invention, comprising:
Wipe module 501, be used for each storage unit of object block is carried out erase operation;
The first soft programming verification module 502, whether the threshold voltage that is used for verification object piece storage unit is all greater than zero; If then trigger and wipe verification module 504; If not, then trigger the first soft programming module 503;
The first soft programming module 503 is used for triggering the first soft programming verification module 502 afterwards through the storage unit of said object block being carried out the threshold voltage of the said storage unit of soft programming operation lifting;
Wipe verification module 504, whether the threshold voltage that is used for verifying each storage unit of object block is all less than the threshold voltage upper limit of erase status; If, end operation then; If not, then module 501 is wiped in triggering.
Further, said device also comprises: pre-programmed module 505, be used for before said erase step, and each storage unit in the object block is carried out the pre-programmed operation.
The operation of the pre-programmed of said pre-programmed module is specially: the word line to each storage unit in the object block applies positive voltage, and the threshold voltage of each storage unit is promoted to the 2nd
nIn the state corresponding threshold voltage range; Wherein, said cell stores n bit data has 2
nThe state of kind, the 2nd
nState corresponding threshold lower voltage limit is greater than all the other state corresponding threshold upper voltage limit.
Said device also comprises: the second soft programming verification module 506; Be used at the threshold voltage of said first each storage unit of soft programming calibration mode block check all after the threshold voltage upper limit less than erase status, whether the threshold voltage of the storage unit on the verification selected word line is all greater than the threshold voltage lower limit of erase status; If then choose next word line to verify, up to the storage unit of having verified on all word lines, end operation; If not, then trigger the second soft programming module 507;
The second soft programming module 507 is used for operating the threshold voltage of the said storage unit of lifting through the storage unit on the current selected word line being carried out soft programming, and returns the second soft programming checking procedure.
Further, the said second soft programming verification module 506 comprises:
The first pressurization submodule is used for the word line of choosing is applied positive voltage; And, unchecked word line with its voltage zero setting, is perhaps applied the voltage of the minimum threshold voltage that is less than or equal to all unchecked storage unit to unchecked word line;
First comparison sub-module is used for detecting successively the leakage current in each storage unit drain electrode; If leakage current is more than or equal to the 3rd reference current, then the threshold voltage of this storage unit is smaller or equal to the threshold voltage lower limit of erase status; If leakage current is less than the 3rd reference current, then the threshold voltage of this storage unit is greater than the threshold voltage lower limit of erase status; Wherein, the 3rd reference current is less than first reference current and greater than second reference current.
Each embodiment in this instructions all adopts the mode of going forward one by one to describe, and what each embodiment stressed all is and the difference of other embodiment that identical similar part is mutually referring to getting final product between each embodiment.For system embodiment, because it is similar basically with method embodiment, so description is fairly simple, relevant part gets final product referring to the part explanation of method embodiment.
More than to the method for deleting and the device of a kind of nonvolatile memory provided by the present invention; Carried out detailed introduction; Used concrete example among this paper principle of the present invention and embodiment are set forth, the explanation of above embodiment just is used for helping to understand method of the present invention and core concept thereof; Simultaneously, for one of ordinary skill in the art, according to thought of the present invention, the part that on embodiment and range of application, all can change, in sum, this description should not be construed as limitation of the present invention.
Claims (14)
1. the method for deleting of a nonvolatile memory is characterized in that, comprising:
Wipe: each storage unit in the object block is carried out erase operation;
The first soft programming verification: whether the threshold voltage of storage unit is all greater than zero in the verification object piece; If then carry out and wipe checking procedure; If not, then carry out first soft-program step;
First soft programming: operate the threshold voltage of the said storage unit of lifting through the storage unit in the said object block being carried out soft programming, and return the first soft programming checking procedure;
Wipe verification: whether the threshold voltage of each storage unit is all less than the threshold voltage upper limit of erase status in the checking object block; If, end operation then; If not, then return erase step.
2. the method for claim 1 is characterized in that, before said erase step, also comprises:
Pre-programmed: each storage unit in the object block is carried out the pre-programmed operation.
3. method as claimed in claim 2 is characterized in that, said pre-programmed operation is specially:
Word line to each storage unit in the object block applies positive voltage, and the threshold voltage of each storage unit is promoted to the 2nd
nIn the state corresponding threshold voltage range;
Wherein, said cell stores n bit data has 2
nThe state of kind, the 2nd
nState corresponding threshold lower voltage limit is greater than all the other state corresponding threshold upper voltage limit.
4. like claim 1 or 3 described methods, it is characterized in that in the said first soft programming checking procedure, the threshold voltage of each storage unit of verification all after the threshold voltage upper limit less than erase status, also comprises:
The second soft programming verification: whether the threshold voltage of the storage unit on the verification selected word line is all greater than the threshold voltage lower limit of erase status; If then choose next word line to verify, up to the storage unit of having verified on all word lines, end operation; If not, then carry out second soft-program step;
Second soft programming: operate the threshold voltage of the said storage unit of lifting through the storage unit on the current selected word line being carried out soft programming, and return the second soft programming checking procedure.
5. method as claimed in claim 4 is characterized in that, the said first soft programming checking procedure comprises:
The voltage that applies on the word line with each storage unit is changed to zero;
Detect the leakage current in each storage unit drain electrode successively; If leakage current is more than or equal to first reference current, then the threshold voltage of this storage unit is smaller or equal to zero; If leakage current is less than first reference current, then the threshold voltage of this storage unit is greater than zero.
6. method as claimed in claim 5 is characterized in that, wipes in the checking procedure said, chooses each word line successively, and each storage unit on this word line is verified, specifically comprises:
Word line to choosing applies positive voltage;
To unchecked word line with its voltage zero setting; Perhaps, unchecked word line is applied the voltage of the minimum threshold voltage that is less than or equal to all unchecked storage unit;
Detect the leakage current in each storage unit drain electrode successively; If leakage current is greater than second reference current, then the threshold voltage of this storage unit is less than the threshold voltage upper limit of erase status; If leakage current is smaller or equal to second reference current, then the threshold voltage of this storage unit is more than or equal to the threshold voltage upper limit of erase status;
Wherein, second reference current is less than first reference current.
7. method as claimed in claim 6 is characterized in that, the said second soft programming checking procedure comprises:
Word line to choosing applies positive voltage;
To unchecked word line with its voltage zero setting; Perhaps, unchecked word line is applied the voltage of the minimum threshold voltage that is less than or equal to all unchecked storage unit;
Detect the leakage current in each storage unit drain electrode successively;
If leakage current is more than or equal to the 3rd reference current, then the threshold voltage of this storage unit is smaller or equal to the threshold voltage lower limit of erase status; If leakage current is less than the 3rd reference current, then the threshold voltage of this storage unit is greater than the threshold voltage lower limit of erase status;
Wherein, the 3rd reference current is less than first reference current and greater than second reference current.
8. the erasing apparatus of a nonvolatile memory is characterized in that, comprising:
Wipe module, be used for each storage unit of object block is carried out erase operation;
The first soft programming verification module, whether the threshold voltage that is used for verification object piece storage unit is all greater than zero; If then trigger and wipe the verification module; If not, then trigger the first soft programming module;
The first soft programming module is used for triggering the first soft programming verification module afterwards through the storage unit of said object block being carried out the threshold voltage of the said storage unit of soft programming operation lifting;
Wipe the verification module, whether the threshold voltage that is used for verifying each storage unit of object block is all less than the threshold voltage upper limit of erase status; If, end operation then; If not, then module is wiped in triggering.
9. device as claimed in claim 2 is characterized in that, also comprises:
The pre-programmed module was used for before said erase step, and each storage unit in the object block is carried out the pre-programmed operation.
10. device as claimed in claim 9 is characterized in that, the pre-programmed operation of said pre-programmed module is specially:
Word line to each storage unit in the object block applies positive voltage, and the threshold voltage of each storage unit is promoted to the 2nd
nIn the state corresponding threshold voltage range;
Wherein, said cell stores n bit data has 2
nThe state of kind, the 2nd
nState corresponding threshold lower voltage limit is greater than all the other state corresponding threshold upper voltage limit.
11. like claim 8 or 10 described devices, it is characterized in that, also comprise:
The second soft programming verification module; Be used at the threshold voltage of said first each storage unit of soft programming calibration mode block check all after the threshold voltage upper limit less than erase status, whether the threshold voltage of the storage unit on the verification selected word line is all greater than the threshold voltage lower limit of erase status; If then choose next word line to verify, up to the storage unit of having verified on all word lines, end operation; If not, then trigger the second soft programming module;
The second soft programming module is used for operating the threshold voltage of the said storage unit of lifting through the storage unit on the current selected word line being carried out soft programming, and returns the second soft programming checking procedure.
12. device as claimed in claim 11 is characterized in that, the said first soft programming verification module comprises:
The first pressurization submodule, the voltage that is used for applying on the word line with each storage unit is changed to zero;
First comparison sub-module is used for detecting successively the leakage current in each storage unit drain electrode; If leakage current is more than or equal to first reference current, then the threshold voltage of this storage unit is smaller or equal to zero; If leakage current is less than first reference current, then the threshold voltage of this storage unit is greater than zero.
13. device as claimed in claim 12 is characterized in that, the said verification module of wiping is chosen each word line successively, and each storage unit on this word line is verified that it specifically comprises:
Wipe compression module, be used for the word line of choosing is applied positive voltage; And, unchecked word line with its voltage zero setting, is perhaps applied the voltage of the minimum threshold voltage that is less than or equal to all unchecked storage unit to unchecked word line;
Wipe comparison sub-module, be used for detecting successively the leakage current in each storage unit drain electrode; If leakage current is greater than second reference current, then the threshold voltage of this storage unit is less than the threshold voltage upper limit of erase status; If leakage current is smaller or equal to second reference current, then the threshold voltage of this storage unit is more than or equal to the threshold voltage upper limit of erase status;
Wherein, second reference current is less than first reference current.
14. device as claimed in claim 13 is characterized in that, the said second soft programming verification module comprises:
The first pressurization submodule is used for the word line of choosing is applied positive voltage; And, unchecked word line with its voltage zero setting, is perhaps applied the voltage of the minimum threshold voltage that is less than or equal to all unchecked storage unit to unchecked word line;
First comparison sub-module is used for detecting successively the leakage current in each storage unit drain electrode; If leakage current is more than or equal to the 3rd reference current, then the threshold voltage of this storage unit is smaller or equal to the threshold voltage lower limit of erase status; If leakage current is less than the 3rd reference current, then the threshold voltage of this storage unit is greater than the threshold voltage lower limit of erase status;
Wherein, the 3rd reference current is less than first reference current and greater than second reference current.
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