Flash Memory Pulse-Width Programming to Prevent Cell Disturb
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing flash memory technologies face challenges in selectively programming memory cells without affecting unselected cells, leading to unwanted state alterations during programming operations.
Innovation Solution
A self-boosting inhibit scheme is employed to maintain the original state of unselected memory cells by using a selective programming method that includes biasing the unselected cells to inhibit electron tunneling through a self-boosting mechanism, ensuring they remain within an allowable range of alteration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional programming operations are performed on selected memory cells, then the selected cells can be programmed, but unselected memory cells may be unintentionally affected and altered
Solution Approach 1:
The patent applies different voltage conditions to different regions of the memory array. Selected cells receive programming voltages (Vprog on control gate, Vdd on bit line) while unselected cells receive inhibiting voltages (Vinh on bit line). This local differentiation ensures that only selected cells undergo programming while unselected cells are protected from unwanted alterations.
Solution Approach 2:
The patent applies inhibit voltages to unselected cells before and during the programming operation on selected cells. By pre-applying Vinh to the bit line and maintaining it during programming, the patent creates a protective condition that prevents electron tunneling in unselected cells before the harmful effect can occur.
2Speed
If longer program pulse width is used, then programming speed improves, but channel voltage boost is reduced affecting programming accuracy
Solution Approach 1:
The patent uses periodic pulse width modulation of the control gate voltage to program memory cells to different threshold voltage levels. By varying the pulse width (duration) of the programming pulse while maintaining the voltage amplitude, the patent achieves precise control over the amount of charge injected into the floating gate, enabling accurate multi-level cell programming without requiring continuously varying voltage levels.
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 prevents unwanted programming of unselected cells, allowing for precise and efficient programming of selected cells while using less complex and compact sense amplifiers, thereby maintaining data integrity.
Implementation Method 1
the control gate voltage is coupled to a floating gate of the non-volatile memory cell
Implementation Method 2
program the non-volatile memory cell by modulating a channel voltage... flow the memory cell current within a specified target current range
Data Source
Figure 1
Figure 2A~2B
Figure 3A
AI summary
A selective non-volatile memory programming method for a selected memory cell in a memory array is described so as to reduce or avoid program disturbance on an unselected memory cell. This selective programming method comprises: applying a programming pulse to a selected memory cell to be programmed and an unselected memory cell, wherein the programming pulse allows a change of the unselected memory cell within a range specified; boosting a region of the unselected memory cell; and setting a threshold time of the programming pulse, wherein the threshold time is defined when an absolute magnitude of a voltage difference between a floating gate of the unselected memory cell and the boosted region of the unselected memory cell reaches a threshold value defined.