Non-Volatile Flash Memory Verification Recovery and Column Seeding
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Solution Overview
Problem
Existing non-volatile memory technologies face challenges in efficiently programming and verifying flash cells due to unwanted residue electrons and disturb effects, particularly when programming in reverse order, which affect charge distribution and readability of multi-state values.
Innovation Solution
Implementing reverse order programming with top-to-bottom extended verification recovery and bottom-side seeding of flash memory cells, where residue electrons are pushed down the column and seed charge is injected from the source line, ensuring efficient charge distribution and reduced disturb effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional programming order is used, then programming process is simple, but residue electrons cause charge distribution spread and reduce multi-state storage accuracy
Solution Approach 1:
The patent applies reverse order programming by programming word lines from top to bottom instead of the conventional bottom to top approach. This inversion allows residue electrons to be naturally pushed down the column during verification recovery, eliminating charge distribution spread without requiring complex additional recovery sequences.
Solution Approach 2:
The patent performs extended verification recovery after programming each word line before moving to the next one. This preliminary recovery action ensures that residue electrons are removed from each word line's column before subsequent programming operations, preventing charge distribution spread and improving multi-state storage accuracy.
2Manufacturing precision
If extended verification recovery is performed after each programming operation, then charge distribution uniformity is improved, but programming time is increased
Solution Approach 1:
By reversing the programming order to top-to-bottom, the patent enables verification recovery to proceed automatically in the same direction as programming. This eliminates the need for separate recovery sequences and reduces overall programming time while maintaining charge distribution uniformity.
Solution Approach 2:
The patent integrates verification recovery into the programming sequence by performing it continuously after each programming operation without requiring additional time steps. The recovery process overlaps with or immediately follows programming, ensuring charge distribution uniformity is maintained without significant time penalty.
3Reliability
If conventional bottom-to-top programming is used, then column charge recovery is simplified, but disturb effects increase and multi-state value readability decreases
Solution Approach 1:
The patent inverts the programming sequence to top-to-bottom, which causes residue electrons to be pushed down the column during verification recovery. This natural electron flow direction eliminates disturb effects on lower word lines and improves the readability of multi-state values without requiring complex additional sequences.
Solution Approach 2:
The patent performs verification recovery after programming each word line to preemptively remove residue electrons before they can cause disturb effects during subsequent programming operations. This preliminary anti-action prevents charge distribution spread and maintains multi-state value integrity.
4Productivity
If seed charge is injected from top side, then column seeding is simple, but charge distribution spread increases and programming efficiency decreases
Solution Approach 1:
The patent inverts the seed charge injection direction to from bottom to top, matching the reverse programming order. This allows seed charge to be injected at the source line and naturally distributed upward through the column, improving programming efficiency and reducing charge distribution spread by aligning with the electron flow direction during verification recovery.
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 enhances programming efficiency and reduces charge distribution spread, improving the reliability and accuracy of multi-state storage in non-volatile memory devices.
Implementation Method 1
residue electrons are pushed down the column
Implementation Method 2
seed charge is injected from the source line
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
An apparatus is described. The apparatus includes a non volatile memory chip. The non volatile memory chip includes an interface to receive access commands, a three dimensional array of non volatile storage cells, and, a controller to orchestrate removal of charge in a column of stacked ones of the non volatile storage cells after a verification process that determined whether or not a particular cell along the column was programmed with a correct charge amount. The removal of the charge pushes the charge out of the column by changing respective word line potentials along a particular direction along the column. Cells that are coupled to the column are programmed in the particular direction. Disturbance of neighboring cells during programming is less along the particular direction than a direction opposite that of the particular direction.