Memory Cell Interference Measurement via Low Frequency Noise
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Solution Overview
Problem
Nonvolatile memory devices, such as flash memory, experience interference from adjacent memory cells, leading to malfunctions during read operations due to changes in threshold voltage, which existing technologies fail to accurately measure and mitigate.
Innovation Solution
A method for measuring interference in memory devices by programming and erasing selected and adjacent memory cells, detecting low-frequency noise changes to determine interference, using initial, first, and third noise values to quantify charge trap amounts and interference effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adjacent memory cells are programmed to store data, then data retention capability is improved, but interference between adjacent cells causes threshold voltage changes leading to read operation malfunctions
Solution Approach 1:
The patent applies preliminary action by measuring the noise value of a first memory cell before programming adjacent memory cells. This initial measurement establishes a baseline to detect interference effects later, allowing the system to identify when adjacent cell programming has caused harmful threshold voltage changes in the first memory cell.
Solution Approach 2:
The patent implements feedback by measuring noise values at multiple stages (initial, after first cell programming, after adjacent cell programming) and using these measurements to determine interference levels. The feedback loop allows the system to detect when interference has occurred and adjust operations accordingly to prevent read failures.
2Quantity of substance
If multiple adjacent memory cells are programmed to increase storage capacity, then data retention is improved, but measurement of interference effects becomes more complex
Solution Approach 1:
The patent applies segmentation by measuring noise values at distinct stages separated by specific programming operations. The measurement process is divided into: initial measurement, measurement after first cell programming, and measurement after adjacent cell programming. This segmentation allows the system to isolate and attribute noise changes to specific programming events, simplifying the analysis even when multiple cells are involved.
Solution Approach 2:
The patent uses preliminary measurement of the first memory cell's noise value before any adjacent cell programming. This baseline measurement simplifies subsequent interference analysis by providing a reference point, allowing the system to attribute any noise changes to the programming operations of adjacent cells rather than requiring complex multi-variable analysis.
3Measurement precision
If noise values are measured at multiple stages to accurately detect interference, then measurement precision is improved, but measurement time and process complexity increase
Solution Approach 1:
The patent performs the initial noise measurement of the first memory cell before any programming operations. This preliminary action establishes a baseline that simplifies subsequent measurements, as the system only needs to detect changes from this known reference state rather than measuring all possible combinations of cell states.
Solution Approach 2:
The patent segments the measurement process into three key stages: initial measurement, measurement after first cell programming, and measurement after adjacent cell programming. This segmentation identifies the most critical measurement points where interference occurs, avoiding the need for continuous or exhaustive measurements while maintaining detection accuracy.
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
Accurately measures and analyzes interference between memory cells, improving the prediction of threshold voltage distributions and enhancing data stability by setting optimal read voltages, thereby reducing read operation errors.
Implementation Method 1
the first noise value and the second noise value are measured by detecting a low frequency noise of a cell current of the selected memory cell
Data Source
AI summary
A method for measuring interference in a memory device is provided. The method includes: programming a selected memory cell among a plurality of memory cells connected in series between a bit line and a source line; measuring a first noise value of the programmed selected memory cell; programming an adjacent memory cell adjacent to the selected memory cell among the plurality of memory cells; measuring a second noise value of the selected memory cell, after the programming of the adjacent memory cell is completed; and determining interference on the selected memory cell based on the first noise value and the second noise value. The first noise value and the second noise value are measured by detecting a low frequency noise of a cell current of the selected memory cell.