Nonvolatile Memory Programming Voltage Control
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Solution Overview
Problem
Nonvolatile memory devices face program disturbance issues due to channel boosting, where unselected memory cells are inadvertently programmed, and as devices shrink, the limited number of cells participating in boosting leads to insufficient capacitance and increased leakage currents, causing disturbances and failures.
Innovation Solution
A method of programming nonvolatile memory devices by controlling the number of memory cells involved in channel boosting through specific voltage applications to word lines, using a program voltage higher than pass voltages, with buffer and cut-off voltages to isolate channels and prevent excessive boosting, and re-programming sequences that limit peripheral cell influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If channel boosting is increased to prevent program disturbance in unselected memory cells, then program disturbance is reduced, but leakage current increases and causes disturbances and failures
Solution Approach 1:
The patent applies different voltage levels to different groups of word lines based on their position relative to the selected word line. Word lines closer to the selected line receive higher pass voltages to generate sufficient channel boosting for program disturbance prevention, while word lines farther away receive lower pass voltages to minimize leakage current. This localized voltage differentiation resolves the contradiction by optimizing each region's voltage according to its specific needs.
Solution Approach 2:
The patent divides the word lines into multiple groups (first group, second group, third group, etc.) based on their distance from the selected word line. Each group is assigned a different pass voltage level, creating a segmented voltage distribution strategy. This segmentation allows the system to manage channel boosting and leakage current trade-offs independently in different regions, preventing program disturbance while controlling overall leakage.
2Quantity of substance
If device size is reduced to increase integration capacity, then storage capacity increases, but the number of cells participating in channel boosting decreases, leading to insufficient capacitance and increased leakage effects
Solution Approach 1:
The patent changes the voltage parameter distribution across word lines to compensate for reduced channel capacitance in scaled-down devices. By applying higher pass voltages to critical word lines (those closer to the selected line), the system maintains sufficient channel boosting effects even when fewer cells are available to participate in boosting due to device scaling. This parameter adjustment ensures reliable operation despite reduced physical dimensions.
3Reliability
If pass voltage is increased to boost channel voltage and prevent program disturbance, then unselected memory cells are protected, but excessive channel boosting occurs causing hot electron injection and program disturbance
Solution Approach 1:
The patent implements local quality control by assigning different pass voltage levels to different word line groups based on their position. Word lines immediately adjacent to the selected line receive moderate pass voltages to prevent program disturbance, while word lines farther away receive lower voltages to avoid excessive channel boosting and hot electron injection. This spatially differentiated approach optimizes program inhibition while preventing harmful side effects.
Solution Approach 2:
The patent employs dynamic voltage control where pass voltages are adjusted based on the specific programming operation being performed and the position of word lines. The voltage levels are not fixed but are optimized for each programming context, allowing the system to maintain program inhibition effectiveness while dynamically preventing excessive channel boosting that would cause hot electron injection.
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 reduces program disturbance and leakage current effects, maintaining data integrity by optimizing channel potential and reducing the number of electrons generated by GIDL, thereby enhancing the programming characteristics of memory cells.
Implementation Method 1
During the program operation, hot electrons are injected into the floating gate
Implementation Method 2
During the erase operation, electrons injected into the floating gate are discharged by F-N tunneling
Data Source
AI summary
In a method of programming a nonvolatile memory device, when a program is performed, a program voltage is applied to a first word line selected for the program. A first pass voltage is applied to three second word lines neighboring the first word line toward a source select line. First and second voltages are applied to third and fourth word lines neighboring the first word line toward the source select line. A second pass voltage is applied to the remaining word lines other than the first to fourth word lines.