Flash Memory Zone-Based Pass Voltage Control
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Solution Overview
Problem
Flash memory devices face malfunctions due to inadequate pass voltage windows, which are determined after fabrication, leading to delayed development and modification of programming methods.
Innovation Solution
A flash memory device with a controller and high voltage generator that divides word-line addresses into zones, applying distinct pass voltages to selected and unselected areas to enhance the pass voltage window, allowing for discriminative programming of memory cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single pass voltage is applied to all word lines, then the programming operation is simple, but program voltage disturbance occurs causing memory cell malfunction
Solution Approach 1:
The patent divides the memory array into multiple zones based on word-line address ranges, and applies different pass voltages to different zones. This segmentation allows the system to prevent program voltage disturbance while maintaining manageable complexity through structured voltage application.
Solution Approach 2:
The patent applies different pass voltage levels to different spatial zones of the memory array based on their address ranges. This local quality approach ensures that each zone receives the appropriate voltage level to prevent disturbances, improving overall reliability without requiring a completely complex global control system.
2Reliability
If a high pass voltage is applied to prevent program voltage disturbance, then program voltage disturbance is reduced, but pass voltage disturbance occurs in memory cells to which pass voltage is applied
Solution Approach 1:
The patent applies different pass voltage levels to different zones based on their word-line address ranges. By making the pass voltage level zone-dependent rather than uniform, the system prevents program voltage disturbance in selected cells while avoiding pass voltage disturbance in unselected cells, thus resolving the harmful effect.
Solution Approach 2:
The patent changes the pass voltage parameter based on the zone identification derived from word-line addresses. By dynamically adjusting the voltage level according to the target address range, the system optimizes both program voltage stability and prevents harmful pass voltage effects on non-selected memory cells.
3Reliability
If the pass voltage window is determined after wafer fabrication, then the pass voltage level can be optimized for the specific device, but development time is delayed due to multiple programming method revisions
Solution Approach 1:
The patent segments the word-line address space into multiple zones and associates different pass voltage levels with each zone. This segmentation allows for systematic voltage optimization that can be implemented through software configuration rather than hardware revision, reducing development turnaround time while maintaining optimized pass voltage windows.
Solution Approach 2:
The patent implements a dynamic pass voltage selection mechanism where the controller determines the appropriate pass voltage level based on the target word-line address range. This dynamic approach allows flexible optimization of the pass voltage window without requiring fixed hardware configurations, enabling faster development iterations.
Data Source
AI summary
A flash memory device including a controller to determine higher, M, and lower, N, word-line address bits based on an input word-line address, to determine a selected area of a memory array based on the higher and lower word-line address bits, and an unselected area of the memory array based on the selected area; and a high voltage generator to provide a first pass voltage to a word line of the selected area, and to provide a second pass voltage to a word line of the unselected area. The pass voltages are discriminately applied to the programmed and non-programmed memory cells, enlarging the pass voltage window. The memory array is divided into pluralities of zones to which local voltages are each applied in different levels.