Nonvolatile Memory Program Voltage Control
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Solution Overview
Problem
In nonvolatile memory devices, the distribution of threshold voltages in multi-level cells (MLCs) widens during programming, leading to reduced reliability due to varying operation speeds among memory cells, which affects the margin between different voltage distributions.
Innovation Solution
A nonvolatile memory device and method that control the duration of program voltage supply according to the rise in program voltage levels, using a high voltage generation unit, block selection unit, discharge unit, and discharge control unit to shorten the time for program voltage application, thereby preventing the widening of threshold voltage distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the program voltage is supplied for a fixed duration during ISPP operation, then the programming process is simple to control, but the distribution of threshold voltages of memory cells widens
Solution Approach 1:
The patent applies dynamics by making the program voltage supply duration variable rather than fixed. The discharge control unit dynamically adjusts the discharge timing based on the current program voltage level, causing the program voltage to be supplied for different durations at different programming stages. This dynamic adjustment prevents the threshold voltage distribution from widening while maintaining operational simplicity.
Solution Approach 2:
The patent implements feedback through the discharge control unit that monitors the program voltage level and adjusts the discharge timing accordingly. The discharge elements are controlled based on the current program voltage, creating a feedback mechanism that ensures optimal programming duration at each stage and prevents threshold voltage distribution broadening.
2Adaptability or versatility
If the program voltage level is increased to program slower memory cells, then all memory cells can be programmed, but the threshold voltage distribution widens due to prolonged voltage application
Solution Approach 1:
The patent uses dynamics by adjusting the program voltage supply duration according to the voltage level. When higher program voltage levels are applied to program slower memory cells, the discharge timing is accordingly adjusted to limit the exposure time. This dynamic adjustment allows programming of all memory cells while preventing threshold voltage distribution from widening.
Solution Approach 2:
The patent applies parameter changes by varying both the program voltage level and the supply duration as different programming stages are completed. The discharge control unit adjusts the discharge timing parameter based on the current program voltage level, creating a coordinated change in both voltage magnitude and duration parameters to achieve comprehensive programming without distribution broadening.
3Productivity
If the program voltage is supplied for a longer duration to ensure complete programming, then all memory cells are programmed, but the margin between different threshold voltage distributions is reduced
Solution Approach 1:
The patent applies dynamics by making the program voltage supply duration adaptive rather than fixed. The discharge control unit dynamically adjusts the discharge timing based on the program voltage level, ensuring that the voltage is supplied long enough to program all memory cells but not so long as to widen the threshold voltage distribution. This dynamic adjustment maintains the margin between different distributions.
Solution Approach 2:
The patent applies partial action by providing just enough program voltage exposure to achieve complete programming without excessive duration. The discharge timing is precisely controlled to stop voltage application at the optimal moment, avoiding over-programming that would widen threshold voltage distributions while ensuring all memory cells are adequately programmed.
Data Source
AI summary
A nonvolatile memory device includes a high voltage generation unit configured to generate a program voltage and a pass voltage, a block selection unit coupled to the high voltage generation unit through global word lines, a memory cell array coupled to the block selection unit through word lines, a discharge unit coupled to the global word lines and configured to change a level of voltage supplied to the global word lines, and a discharge control unit configured to generate a discharge signal, and transfer the discharge signal to the discharge unit in response to the program voltage.