Flash Memory Programming Precompensation for Coupling Errors
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Solution Overview
Problem
In flash memory programming, floating gate to floating gate coupling causes errors due to unpredictable threshold voltage shifts in neighbor cells, leading to increased programming errors and overprogramming, especially as multilevel cells require precise voltage range management.
Innovation Solution
The method involves precompensating the target threshold voltage of a selected cell by accounting for coupling disturb from neighboring cells, determining pretarget voltages based on coupling ratios between the selected cell and its neighbors, and alternating between programming to target and pretarget threshold voltages in a rolling pattern to minimize error.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional flash memory programming is used without precompensation, then programming speed is maintained, but programming errors increase due to floating gate coupling effects
Solution Approach 1:
The patent applies preliminary action by precompensating the target threshold voltage before the actual programming operation. The method calculates coupling ratios between selected cells and neighbor cells, then adjusts the target voltage to account for expected threshold voltage shifts. This preliminary compensation ensures that even though programming continues at high speed, the final threshold voltage accuracy is maintained despite floating gate coupling effects from neighboring cells being programmed.
2Quantity of substance
If multilevel cells are used to increase memory density, then storage capacity increases, but programming precision requirements increase due to tighter voltage range management
Solution Approach 1:
The patent applies local quality by treating each selected cell individually with its own precompensated target threshold voltage based on its specific coupling ratios with neighboring cells. Rather than applying a uniform programming approach, the method calculates and applies localized compensation for each cell's unique position and coupling characteristics. This enables multilevel cells to maintain precise voltage ranges despite varying coupling effects, thereby supporting higher memory density with adequate programming precision.
3Productivity
If neighbor cells are programmed to higher threshold voltages, then memory capacity utilization improves, but threshold voltage shifts in selected cells increase due to coupling effects
Solution Approach 1:
The patent applies preliminary anti-action by precompensating the target threshold voltage to counteract the expected coupling effects from neighboring cell programming. The method calculates coupling ratios and uses them to adjust the target voltage in advance, creating a compensating effect that offsets the threshold voltage shifts caused by programming neighbor cells to higher voltages. This allows full utilization of memory capacity while maintaining precise threshold voltage control through the preemptive compensation mechanism.
Data Source
AI summary
Methods of programming a memory and memories are disclosed. In at least one embodiment, a memory is programmed by determining a pretarget threshold voltage for a selected cell, wherein the pretarget threshold voltage is determined using pretarget threshold voltage values for at least one neighbor cell of the selected cell.