Non-Volatile Memory Program-Verify Voltage Adjustment
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Solution Overview
Problem
Conventional NAND flash memory devices experience widened threshold voltage distributions among memory cells due to back pattern dependency and interference effects, degrading read margin and retention characteristics.
Innovation Solution
Applying different program-verify voltages to different groups of word lines, with the last word line receiving a distinct voltage to mitigate interference and align its threshold voltage with other cells, thereby reducing overall distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ISPP is used to program memory cells, then programming capability is achieved, but threshold voltage distribution widens due to back pattern dependency and interference effects
Solution Approach 1:
The patent applies different program-verify voltages to different groups of word lines based on their position in the programming sequence. The last word line receives a distinct program-verify voltage compared to other word lines, creating localized quality differences in the verification process to compensate for interference effects specific to each position.
Solution Approach 2:
The patent changes the program-verify voltage parameter based on the word line position. By applying a different program-verify voltage to the last word line compared to other word lines, the system adjusts the verification parameter to account for the unique interference conditions experienced by cells programmed later in the sequence.
2Ease of operation
If ISPP is used to program memory cells, then programming operation is enabled, but read margin degrades due to increased threshold voltage differences
Solution Approach 1:
The patent applies different program-verify voltages to different groups of word lines based on their position in the programming sequence. The last word line receives a distinct program-verify voltage compared to other word lines, creating localized quality differences in the verification process to compensate for interference effects specific to each position.
Solution Approach 2:
The patent implements a feedback mechanism where the program-verify step provides information about the programming success of each word line. By verifying programming results and using this feedback to guide subsequent programming operations, the system can adjust parameters to maintain read margin reliability.
3Productivity
If ISPP is used to program memory cells, then data writing is achieved, but retention characteristics are adversely affected due to threshold voltage distribution
Solution Approach 1:
The patent applies different program-verify voltages to different groups of word lines based on their position in the programming sequence. The last word line receives a distinct program-verify voltage compared to other word lines, creating localized quality differences in the verification process to compensate for interference effects specific to each position.
Solution Approach 2:
The patent changes the program-verify voltage parameter based on the word line position. By applying a different program-verify voltage to the last word line compared to other word lines, the system adjusts the verification parameter to account for the unique interference conditions experienced by cells programmed later in the sequence.
Data Source
AI summary
A method for programming a non-volatile memory device includes applying a first program-verify voltage to a first word line to determine whether or not memory cells associated with the first word line have been programmed successfully. A second program-verify voltage is applied to a second word line to determine whether or not memory cells associated with the second word line have been programmed successfully. The second program-verify voltage is different from the first program-verify voltage. The first and second word lines are associated with the same word line switching unit.