CHISEL Programming for Non-Volatile Memory Cells
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Solution Overview
Problem
Conventional non-volatile memory cell programming methods, such as channel hot electron injection, suffer from longer program times, higher power consumption, and poor endurance performance due to larger programming currents and limited cycling capabilities.
Innovation Solution
The method employs channel-initiated secondary electron (CHISEL) injection, where a negative voltage is applied to the substrate, generating secondary electrons that are drawn to a charge-trapping structure, reducing programming time, current, and improving endurance by optimizing voltage configurations across the substrate and source/drain regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If channel hot electron (CHE) injection is used to program the non-volatile memory cell, then the programming process can be completed, but the program time becomes long (0.5-5 ms) and power consumption increases (200-300 μA)
Solution Approach 1:
The patent applies a negative voltage to the substrate (e.g., -5V to -20V) instead of the conventional 0V, which fundamentally changes the electrical parameters of the system. This parameter change enables the generation of secondary electrons through impact ionization, dramatically increasing the number of electrons available for injection into the charge trapping layer and thus reducing programming time from 0.5-5 ms to much shorter durations
Solution Approach 2:
The patent introduces secondary electrons as an intermediary mechanism between the applied voltage and the charge trapping process. By applying negative voltage to the substrate, secondary electrons are generated through impact ionization and serve as the primary carriers for injection into the charge trapping layer, replacing the direct hot electron injection method and achieving faster programming
2Productivity
If channel hot electron (CHE) injection is used to program the non-volatile memory cell, then the programming process can be completed, but the programming current becomes large (200-300 μA) causing larger power consumption
Solution Approach 1:
The patent changes the voltage distribution parameters by applying negative voltage to the substrate and adjusting the gate and source/drain voltages accordingly. This parameter optimization enables efficient secondary electron generation with lower overall power consumption compared to the high current (200-300 μA) required by conventional CHE injection methods
3Productivity
If channel hot electron (CHE) injection is used to program the non-volatile memory cell, then the programming process can be completed, but the endurance performance becomes poor (less than 100 times of program-erase cycling)
Solution Approach 1:
The patent applies negative voltage to the substrate during programming, which changes the stress distribution and injection mechanism. This parameter change reduces damage to the charge trapping layer and surrounding structures, thereby improving the endurance performance from less than 100 cycles to significantly higher cycling capabilities
Solution Approach 2:
By using secondary electrons as the intermediary injection mechanism instead of direct hot electrons, the patent reduces the harmful effects of high-energy electron impact on the memory structure. The secondary electrons provide a gentler injection process that preserves the integrity of the charge trapping layer over repeated cycling operations
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
CHISEL injection significantly shortens programming time, reduces power consumption, and enhances endurance performance by inducing a large amount of secondary electrons to be drawn to the charge-trapping structure, outperforming conventional CHE methods in program time, current, and cycling reliability.
Implementation Method 1
Because the substrate is applied with a negative voltage in the program method of this invention, a large amount of secondary electrons are induced by impact of the channel hot electrons
Implementation Method 2
The hot electrons are then drawn to the charge storage layer by the high positive voltage on the gate
Data Source
AI summary
A method for programming a non-volatile memory cell is described. The memory cell includes a substrate, a gate over the substrate, a charge-trapping structure at least between the substrate and the gate, and first and second S/D regions in the substrate beside the gate. The method includes performing a channel-initiated secondary electron (CHISEL) injection process to inject electrons to the charge-trapping structure.