FLOTOX EEPROM Tunnel Window Voltage Protection
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Solution Overview
Problem
FLOTOX-TYPE EEPROMs face issues with excessive voltage application to the tunnel window, leading to potential failure and reduced rewrite capabilities due to high breakdown voltages in peripheral circuits, which are not adequately managed in the EEPROM's thin oxide film and drain junction.
Innovation Solution
The EEPROM design includes impurity regions and channel stopper regions spaced apart by predetermined distances to adjust breakdown voltages, allowing the EEPROM to withstand high voltages while preventing excessive voltage application to the tunnel window, thereby increasing the number of rewrites and reducing stress on the thin oxide film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the tunnel window is formed with a thin oxide film to enable FN tunneling current, then electron injection and extraction efficiency is improved, but the breakdown voltage decreases making the tunnel window vulnerable to damage from excessive voltage
Solution Approach 1:
A protection structure comprising a protection gate electrode and protection oxide film is introduced as an intermediary element between the control gate and the tunnel window. This protection structure acts as a voltage buffer that prevents excessive voltage from reaching the thin tunnel window oxide film, thereby protecting it from breakdown while allowing normal operation. The protection structure absorbs the harmful voltage spikes and ensures the tunnel window operates within safe voltage limits.
2Power
If the breakdown voltage of the drain junction is set high to withstand FN tunneling current, then high voltage operation is enabled, but the drain junction becomes vulnerable to damage when high voltage is applied for screening early failure in peripheral circuits
Solution Approach 1:
The gate structure is segmented into multiple independent components: a control gate electrode for normal operation and a protection gate electrode specifically designed for voltage protection. This segmentation allows the control gate to maintain high voltage operation capability for FN tunneling while the protection gate can be independently activated during voltage screening to protect the drain junction from excessive voltage damage.
3Power
If peripheral circuits are designed to withstand high voltages for FN tunneling, then high voltage operation is achieved, but the tunnel window and drain junction are exposed to excessive voltage during voltage screening that causes failure or reduces rewrite capability
Solution Approach 1:
The protection gate electrode and protection oxide film structure is pre-configured to activate before the tunnel window and drain junction can be damaged by excessive voltage. During voltage screening or abnormal high voltage conditions, the protection structure creates a voltage barrier that prevents excessive voltage from reaching the sensitive tunnel window and drain junction, thereby preemptively protecting them from harmful voltage effects.
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 configuration effectively sets lower breakdown voltages for the drain junction and tunnel window, preventing damage from excessive voltage and enhancing the EEPROM's durability and rewrite capacity.
Implementation Method 1
the EEPROM uses FN tunneling current for writing data
Data Source
AI summary
A FLOTOX-TYPE EEPROM of the invention has a configuration wherein an N region 25 as an impurity region formed under a tunnel window 12 and a channel stopper region 19 formed under a LOCOS oxide film 18 are spaced apart by a predetermined distance Y. Therefore, the tunnel window 12 does not sustain damage if an excessive voltage is applied to the tunnel window 12. As a result, the FLOTOX-TYPE EEPROM is adapted to limit the voltage applied to the tunnel window 12 and to reduce stress on the tunnel window 12 and can achieve an increased number of rewrites.