Flash Memory Cell Stabilization Voltage for Threshold Variability
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Solution Overview
Problem
In flash memory devices, the variability in threshold voltage of memory cells after programming leads to inconsistent data storage, as it takes time for charges to distribute evenly in the charge storage layer, resulting in inaccurate data reading before the threshold voltage becomes constant.
Innovation Solution
Applying a stabilization voltage with an electric field opposite to the programming voltage after the higher of the two programming voltages in a memory cell programming method for 2-bit data, which accelerates the distribution of charges and stabilizes the threshold voltage, thereby improving programming speed and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If charges are injected into a charge storage layer to program a memory cell, then the threshold voltage increases to store data, but it takes a predetermined period of time for the threshold voltage to become constant, causing variability in measured threshold voltage and inaccurate data reading
Solution Approach 1:
The patent applies a stabilization voltage having an electric field opposite in polarity to the programming voltage after charge injection. This preliminary stabilization action accelerates the distribution of charges in the charge storage layer, causing the threshold voltage to become constant more quickly. By performing this stabilization step immediately after programming, the method reduces the waiting time required for threshold voltage saturation while ensuring accurate and consistent threshold voltage measurements for reliable data reading.
2Productivity
If a stabilization voltage with opposite polarity to programming voltage is applied after programming, then charge distribution is accelerated and threshold voltage becomes constant faster, but additional voltage application steps are required
Solution Approach 1:
The patent implements a periodic stabilization voltage application scheme where a stabilization voltage with opposite polarity to the programming voltage is applied in pulses immediately after charge injection. This periodic application of opposite-polarity voltage creates an electric field that accelerates charge distribution in the charge storage layer, causing the threshold voltage to saturate faster. The periodic nature of this stabilization step enhances programming speed while managing the complexity through a structured, repeatable process.
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 the time required for the threshold voltage to become constant, enhancing data storage reliability and programming speed by ensuring even charge distribution and accurate data reading.
Implementation Method 1
a stabilization voltage having an electric field opposite in polarity to an electric field of a programming voltage used in the programming of the bits
Implementation Method 2
charges may permeate into a charge storage layer of the cell transistor due to an F-N tunneling effect
Implementation Method 3
charges existing in the charge storage layer may be emitted to the bulk layer due to an F-N tunneling effect
Data Source
AI summary
A non-volatile memory cell programming method of programming 2-bit data in a memory cell having 4 threshold voltage distributions may include a first program operation of programming a first bit of the 2-bit data in the memory cell by applying a first programming voltage to the memory cell; a second program operation of programming a second bit of the 2-bit data in the memory cell by applying a second programming voltage to the memory cell; and a stabilization operation of applying a stabilization voltage having an electric field opposite in polarity to an electric field formed by the first and second programming voltages to the memory cell after one of the first and second program operations that corresponds to a higher one of the first and second programming voltages is performed.