CHISEL Programming for Non-Volatile Memory Leakage Reduction
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Solution Overview
Problem
As non-volatile memory cells shrink, high operating voltages required for programming in EEPROM devices lead to increased leakage current and reduced programming efficiency due to the punch-through effect, especially when the tunneling oxide layer has defects.
Innovation Solution
The method employs a charge-trapping layer with an auxiliary charge region and a data storage region, utilizing channel initiated secondary hot electron injection (CHISEL) with controlled voltage applications to inject electrons into the data storage region, creating an abrupt electrical field and reducing programming voltage and current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high operating voltage is applied to program the memory cell, then programming capability is achieved, but leakage current increases and programming efficiency decreases due to punch-through effect
Solution Approach 1:
The charge-trapping layer is divided into two distinct regions: an auxiliary charge region near the source and a data storage region near the drain. This segmentation allows different voltage conditions to be applied to each region, enabling efficient electron injection into the data storage region while preventing punch-through effects that cause leakage current in the channel.
Solution Approach 2:
The auxiliary charge region is specifically designed to have different electrical characteristics than the data storage region. By controlling the threshold voltage and charge distribution locally in the auxiliary region, the invention creates optimal conditions for electron injection while maintaining channel integrity and preventing harmful leakage.
2Length of moving object
If channel length is reduced to enable miniaturization, then device size decreases, but punch-through effect intensifies causing higher leakage current
Solution Approach 1:
The auxiliary charge region acts as an intermediary structure between the source and the data storage region. It mediates the electron injection process by creating a controlled electric field that facilitates electron transfer to the data storage region without allowing direct punch-through of the channel, thus preventing leakage current even in miniaturized devices.
Solution Approach 2:
Electrons are first injected into the auxiliary charge region before being transferred to the data storage region. This preliminary action in the auxiliary region prepares the charge distribution and electric field conditions necessary for efficient programming while maintaining channel integrity and preventing premature punch-through effects.
3Reliability
If conventional hot electron injection is used for programming, then data can be stored, but high power rating and high operating voltage are required
Solution Approach 1:
Dividing the charge-trapping layer into auxiliary and data storage regions enables a two-stage electron injection process that is more energy-efficient than conventional single-stage hot electron injection. The segmentation allows for controlled voltage application that reduces overall power requirements while achieving the same data retention capability.
Solution Approach 2:
The invention changes the voltage parameters applied during programming by using separate voltage controls for the auxiliary charge region and data storage region. This parameter optimization enables electron injection at lower overall power levels compared to conventional hot electron injection methods that require uniformly high voltages across the entire structure.
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 by reducing programming voltage and current while maintaining data retention, addressing the inefficiencies and reliability issues in miniaturized EEPROM devices.
Implementation Method 1
utilizing channel initiated secondary hot electron injection (CHISEL) with controlled voltage applications to inject electrons into the data storage region
Implementation Method 2
creating an abrupt electrical field and reducing programming voltage and current
Data Source
AI summary
A method of operating a non-volatile memory comprising a substrate, a gate, a charge-trapping layer, a source region and a drain region is provided. The charge-trapping layer close to the source region is an auxiliary charge region and the charge-trapping layer close to the drain region is a data storage region. Before prosecuting the operation, electrons have been injected into the auxiliary charge region. When prosecuting the programming operation, a first voltage is applied to the gate, a second voltage is applied to the source region, a third voltage is applied to the drain region and a fourth voltage is applied to the substrate. The first voltage is bigger than the fourth voltage, the third voltage is bigger than the second voltage, and the second voltage is bigger than the fourth voltage to initiate a channel initiated secondary hot electron injection to inject electrons into the data storage region.