Memory Programming Voltage Step Adjustment for Suspend-Resume Drift
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Solution Overview
Problem
During programming operations in semiconductor memory devices, suspensions can lead to threshold voltage drift in memory cells, resulting in overprogramming and reduced data reliability.
Innovation Solution
The method involves suspending the programming operation for a duration, then resuming it. Before the next program loop, the programming voltage is increased by a step size determined based on the suspension duration and the targeted data state, using either a baseline step size for short suspensions or a reduced step size for longer suspensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the programming operation is suspended and then resumed, then the memory device can perform other operations or handle errors, but threshold voltage drift occurs causing overprogramming and reduced data reliability
Solution Approach 1:
The system performs preliminary actions by calculating and applying a voltage step adjustment before resuming the programming operation. The controller determines a step size based on suspension duration and applies it to the programming voltage before the next program loop, preventing overprogramming before it occurs.
Solution Approach 2:
The system uses feedback by monitoring the suspension duration and using this information to adjust the programming voltage step size. The controller continuously tracks how long the programming operation was suspended and dynamically adjusts the voltage step accordingly to compensate for threshold voltage drift.
2Reliability
If the programming voltage step size is increased to compensate for threshold voltage drift, then data reliability is maintained, but programming time increases and productivity decreases
Solution Approach 1:
The system applies dynamics by making the voltage step size adjustable rather than fixed. The controller dynamically selects between different step sizes (first step size for short suspensions, second step size for longer suspensions) based on the actual suspension duration, optimizing both reliability and productivity.
Solution Approach 2:
The system changes the programming voltage parameter by adjusting the step size applied before each program loop. The controller modifies this parameter based on suspension duration, using larger steps when needed for reliability and smaller steps when suspensions were brief, thus balancing productivity.
3Device complexity
If a fixed voltage step size is used for all suspensions, then the control logic is simple, but overprogramming occurs for long suspensions reducing data reliability
Solution Approach 1:
The system transitions from a static fixed step size to a dynamic adjustable step size. The controller evaluates suspension duration and selects appropriate step sizes, adding minimal complexity while significantly improving reliability for long suspensions.
Solution Approach 2:
The system changes the voltage step parameter based on suspension duration conditions. By introducing conditional logic that selects different step sizes based on whether suspension duration exceeds a threshold, the system maintains simple control while preventing overprogramming.
Data Source
AI summary
The memory device includes a memory block with an array of memory cells that are arranged word lines. The memory device also includes circuitry that is configured to program the memory cells of a selected word line of the plurality of word lines. During programming, the circuitry is configured to, in a program loop, apply a programming pulse at a programming voltage VPGM to a selected word line to program a plurality of the memory cells of the selected word line to a target data state. The circuitry is also configured to suspend the programming operation for a suspension duration and then resume the programming operation. Before a next program loop, the circuitry is further configured to increase a programming voltage VPGM by a step size that is determined based on the suspension duration and on the targeted data state.