Flash Memory Cell Programming with Photon-Assisted Tunneling

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Solution Overview

Problem

Existing flash memory devices face challenges in achieving efficient programming and erasing times while minimizing power consumption and maintaining endurance, as they rely on high electric fields that can degrade the tunnel insulator.

Innovation Solution

Illuminating the flash memory cell with photons whose energy approaches the barrier height of the tunnel insulator, enhancing the Fowler-Nordheim tunneling current and allowing for lower programming voltages, thus reducing electric fields and improving endurance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If high programming voltages are used to achieve fast programming times, then programming speed is improved, but power consumption increases and tunnel insulator degradation accelerates

Engineering Contradiction:

Improveprogramming speedVSAvoidpower consumption

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The patent changes the energy state of electrons by introducing photons with energy close to the tunnel insulator barrier height. This allows electrons to tunnel through the insulator at lower voltages by combining photon energy with electrical energy, thereby reducing power consumption while maintaining programming speed

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces photons as an intermediary carrier that mediates the tunneling process. The photons bridge the energy gap between the applied voltage and the tunnel insulator barrier height, enabling efficient charge transfer without requiring high voltages

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If high programming voltages are applied to reduce program time, then programming speed is improved, but tunnel insulator degradation increases

Engineering Contradiction:

Improveprogramming speedVSAvoidendurance

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent changes the energy delivery mechanism from purely electrical to a combination of optical and electrical energy. By tuning photon energy to match the tunnel insulator barrier height, electrons can tunnel effectively at lower voltages, reducing electrical stress and degradation on the tunnel insulator while maintaining programming speed

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent substitutes part of the electrical field mechanism with an optical field mechanism. Instead of relying solely on high electrical fields to drive tunneling, the system uses photon-assisted tunneling where optical energy supplements the electrical energy, reducing the mechanical/electrical stress on the tunnel insulator

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If conventional tunneling is used without photon assistance, then device structure is simple, but programming efficiency is low

Engineering Contradiction:

Improvedevice structureVSAvoidprogramming efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent introduces photons as an intermediary to enhance the tunneling process. This adds a new dimension to the tunneling mechanism without fundamentally changing the device structure, maintaining simplicity while dramatically improving programming efficiency through photon-assisted tunneling

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent makes the existing tunnel insulator serve multiple functions: it acts as both the barrier for charge storage and the target for photon absorption. The same insulator layer that provides data retention also benefits from photon-assisted tunneling, eliminating the need for additional specialized components

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 enables shorter program/erase times with reduced power consumption and increased endurance by leveraging photon-assisted tunneling to accumulate charge faster and lower electric fields across the tunnel insulator.

Implementation Method 1

Illuminating the flash memory cell during programming/erase increases the Fowler-Nordheim tunneling current through the tunnel insulator by way of the photon assisted tunneling (PAT) effect. The PAT effect is similar to the photoelectric effect except that the electron struck by the photon in the PAT effect is promoted over the tunnel barrier rather than being removed from the metal.

Methodology Applied

Scientific EffectPhoton assisted tunneling (PAT) effect: Photoelectric Effect

Implementation Method 2

increases the Fowler-Nordheim tunneling current through the tunnel insulator

Methodology Applied

Scientific EffectFowler-Nordheim tunneling: Electrical Resistance

Data Source

PatentUS12499937B2Flash memory device with photon assisted programming

Publication Date: 2025.12.16 RAMBUS INC

AI summary

A flash memory cell of a flash memory device is illuminated with light during programming and/or erasing. The wavelength of the light is selected such that the photons impinging on the flash memory cell have an energy that approaches the barrier height (conduction band offset) of the tunnel insulator. Illuminating the flash memory cell during programming/erase increases the tunneling current through the tunnel insulator by way of the photon assisted tunneling (PAT) effect.