Non-Volatile Memory Program Disturb Reduction via Differential Pass Voltages
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional channel boosting techniques are ineffective in reducing program disturb in non-volatile memory devices, especially with decreasing channel lengths, leading to increased leakage and hot carrier generation due to band-to-band tunneling and gate-induced drain leakage.
Innovation Solution
Applying a higher pass voltage to word lines associated with previously programmed non-volatile storage elements than to unprogrammed or partly programmed elements, creating a balanced potential difference to reduce charge leakage and forming an isolation region between programmed and unprogrammed elements during programming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional channel boosting techniques are used to reduce program disturb, then program disturb is reduced in devices with longer channel lengths, but the technique becomes ineffective and leads to increased leakage and hot carrier generation in devices with decreasing channel lengths
Solution Approach 1:
The patent applies different pass voltages to different regions of the memory device based on their programming state. Specifically, a first pass voltage is applied to word lines associated with previously programmed memory elements, while a second (lower) pass voltage is applied to word lines associated with unprogrammed or partly programmed elements. This local differentiation in voltage application addresses the specific needs of each region to prevent program disturb without causing excessive leakage or hot carrier generation in scaled devices
Solution Approach 2:
The patent changes the voltage parameter applied to different word lines based on the programming state of associated memory elements. By dynamically adjusting the pass voltage level (first pass voltage for programmed elements, second pass voltage for unprogrammed elements), the system adapts to the specific conditions of each memory element region, effectively reducing program disturb in devices with decreasing channel lengths
2Ease of operation
If a single pass voltage is applied to all word lines during programming, then the programming operation is simplified, but program disturb occurs in unselected memory elements
Solution Approach 1:
The patent implements local quality by applying different pass voltages to different word line groups based on the programming state of their associated memory elements. Word lines connected to previously programmed elements receive a first pass voltage, while word lines connected to unprogrammed or partly programmed elements receive a second pass voltage. This localized voltage differentiation prevents program disturb in unselected elements while maintaining operational clarity
3Reliability
If higher pass voltage is applied to all word lines to prevent program disturb, then program disturb is reduced, but leakage current and hot carrier generation increase
Solution Approach 1:
The patent applies higher pass voltage (first pass voltage) only to word lines associated with previously programmed memory elements where program disturb is the primary concern, while applying lower pass voltage (second pass voltage) to word lines associated with unprogrammed or partly programmed elements. This localized approach reduces program disturb where needed while minimizing leakage current and hot carrier generation in other regions
Solution Approach 2:
The patent converts the potential harm of high voltage application into a benefit by selectively applying higher pass voltage only to specific word line groups where it is most needed (previously programmed elements). The lower pass voltage applied to unprogrammed elements prevents excessive leakage and hot carrier generation, thus converting what would be a harmful side effect into a controlled and beneficial selective protection mechanism
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces program disturb by maintaining a stable boosted channel potential, minimizing leakage and hot carrier generation, and improving programming efficiency even with shorter channel lengths.
Implementation Method 1
The pass voltages boost a potential of associated channel regions
Implementation Method 2
the differential in the pass voltages reduces the leakage of charge from the channel region associated with the unprogrammed and/or partly programmed non-volatile storage elements to the channel region associated with the previously programmed non-volatile storage elements
Data Source
Figure 1~3
Figure 4
Figure 5
AI summary
Non-volatile storage elements (1110..1155) are programmed in a manner that reduces program disturb by using modified pass voltages (Vpassl, Vpass2). -In particular, during the programming of a selected storage element associated with a selected word line, a higher pass voltage (Vpassl) is applied to word lines associated with previously programmed non-volatile storage elements in the set than to word lines associated with unprogrammed and/or partly programmed non- volatile storage elements in the set. (Vpass2) The pass voltage is sufficiently high to balance the channel potentials on the source and drain sides of the selected word line and/or to reduce leakage of charge between the boosted channel regions. Optionally, an isolation region is formed between the boosted channel regions by applying a reduced voltage on one or more word lines between the selected word line and the word lines that receive the higher pass voltage.