Memory Word-Line Isolation for Stable Suspend-Resume Programming
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Solution Overview
Problem
Existing semiconductor memory technologies face challenges in preventing under-programming and over-programming during suspension events in memory cell programming operations, leading to data retention issues and increased error rates.
Innovation Solution
A suspend-resume-go technique is employed where the voltage applied to a selected word line is ramped to a control gate hold voltage, and the word line switch is turned off to isolate the word line from the driver, maintaining the selected word line at this voltage during suspension, thereby preventing under-programming and over-programming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the programming operation is suspended during normal programming, then the memory device can perform other operations, but under-programming and over-programming occur leading to data retention issues
Solution Approach 1:
Before suspending the programming operation, the control circuitry ramps the selected word line voltage to a specific control gate hold voltage and turns off the word line switch to isolate the word line from the driver. This preliminary action ensures that when programming resumes, the word line is already at the correct voltage level, preventing under-programming and over-programming while allowing other operations to occur during suspension.
2Duration of action of moving object
If the word line voltage is maintained at elevated programming voltage during suspension, then programming can resume immediately, but short-term data retention issues occur
Solution Approach 1:
The control circuitry changes the voltage parameter of the selected word line from the elevated programming voltage to a specific control gate hold voltage before suspension. This parameter change maintains the word line in a stable state during suspension, preventing short-term data retention issues while allowing the programming operation to resume correctly after suspension.
3Speed
If the word line switch remains on during suspension, then the word line can be quickly reprogrammed, but the word line cannot be isolated from the driver causing voltage instability
Solution Approach 1:
Before suspending the programming operation, the control circuitry performs the preliminary action of turning off the word line switch to isolate the selected word line from the word line driver. This isolation stabilizes the word line voltage at the control gate hold voltage during suspension. When programming resumes, the switch can be turned back on quickly, combining both voltage stability during suspension and fast reprogramming capability.
Data Source
AI summary
The memory device includes a memory block with an array of memory cells that are arranged in word lines. The word lines are in electrical communication with respective word line drivers and switches. Control circuitry is configured to program the memory cells of a selected word line in a programming operation during which the control circuitry applies an elevated voltage to the selected word line and receives a command to suspend the programming operation. With the word line switch associated with the selected word line turned on, the control circuitry ramps the selected word line from the elevated voltage to a reduced gate holding voltage and then turn the word line switch associated with the selected word line off to electrically isolate the selected word line from the associated word line driver so that the selected word line remains at the gate holding voltage until the programming operation resumes.