Nonvolatile Memory Programming via Substrate Hot Carrier Injection
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Solution Overview
Problem
Nonvolatile memory devices face a compromise between writing speed, reliability, and data retention due to the physical limitations of the tunneling oxide layer, where thinner layers improve speed but degrade retention, and thicker layers improve retention but slow down writing.
Innovation Solution
A method for programming nonvolatile memory that combines the advantages of Fowler-Nordheim tunneling and channel-hot-electron processes by using substrate hot carriers to inject carriers into the memory device, reducing voltage, time, and power consumption, thereby allowing the use of thicker oxide layers for improved efficiency and retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the thickness of the tunneling oxide layer is decreased to improve writing speed, then the writing speed increases, but the data retention degrades
Solution Approach 1:
The patent changes the voltage parameter applied to the control gate, using a pulsed voltage sequence (first voltage level followed by a second higher voltage level) to enable efficient charge injection without requiring thin oxide layers, thus maintaining both writing speed and data retention
2Reliability
If the thickness of the tunneling oxide layer is increased to improve data retention, then the data retention improves, but the writing speed decreases
Solution Approach 1:
The patent applies a two-level pulsed voltage sequence to the control gate, where the second voltage level provides sufficient energy for rapid charge injection into thick oxide layers, achieving both fast writing speed and high data retention with thicker oxide layers
3Speed
If the voltage of the FN tunneling program process is increased to improve writing speed, then the writing speed increases, but the power consumption increases
Solution Approach 1:
The patent uses a periodic pulsed voltage sequence applied to the control gate, with specific pulse widths and amplitude levels, to achieve rapid charge injection at lower average power consumption compared to continuous high-voltage FN tunneling
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 method reduces voltage, time, and power consumption while maintaining writing efficiency and data retention, overcoming the limitations of existing methods by utilizing substrate hot carriers to enhance programming speed and reliability without degrading data retention.
Implementation Method 1
applying a third voltage to the gate or the substrate, to energize the carrier of the substrate enough energy to overcome the barrier of the oxide layer to reach the charge storage device
Data Source
AI summary
A method for programming a nonvolatile memory includes applying at least a voltage to a source or a drain, so as to inject carriers of the source or drain into a substrate; applying a third voltage to a gate or the substrate, so that the carriers which are in the substrate having enough energy can surmount an oxide layer to reach a charge storage device.