Laser Forming of Resistive Memory Cells

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Solution Overview

Problem

The miniaturization of Flash memory technology is limited by the minimum thickness of the charge trapping layer, which affects information retention, and high forming voltages required for resistive memory cells can damage neighboring components, necessitating expensive protective designs.

Innovation Solution

A method for forming resistive memory cells using at least one laser shot to break down the insulating material, avoiding high electrical potentials and allowing the memory cell to switch from a highly resistant to a low resistance state without electrical power supply, enabling cost-effective formation without specific design requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high forming voltages are applied to break down insulating material in resistive memory cells, then the memory cell can be formed and switched from high resistance to low resistance state, but neighboring components can be damaged

Engineering Contradiction:

Improvememory cell formationVSAvoiddamage to neighboring components

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the electrical field-based breakdown mechanism with a thermal field-based mechanism. A laser beam is applied to locally heat and break down the insulating material in the memory cell, eliminating the need for high forming voltages that would otherwise damage neighboring components. The thermal energy from the laser is concentrated precisely on the target memory cell, providing spatial selectivity that prevents collateral damage.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The laser beam acts as an intermediary between the formation process and the memory cell. Instead of applying electrical stress directly to the memory cell (which would require high voltages affecting neighboring components), the laser serves as a mediating energy source that converts optical energy to thermal energy, enabling controlled breakdown without electrical interference with adjacent structures.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If electrical stress is used to form resistive memory cells, then the formation process can be performed, but expensive protective designs are required to prevent damage to neighboring components

Engineering Contradiction:

Improveforming processVSAvoidprotective design requirements

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent substitutes the electrical stress-based forming process with a laser-based thermal process. This eliminates the need for complex protective circuitry and voltage division schemes that would be required to safely apply high forming voltages. The laser process is inherently more selective and does not require additional protective components, simplifying the overall device design.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Area of moving object

If Flash memory is miniaturized, then integration density increases, but the charge trapping layer thickness cannot be reduced below minimum value affecting information retention

Engineering Contradiction:

Improveintegration densityVSAvoidinformation retention

Core Design Contradiction:

Area of moving objectVSStability of the object's composition

Solution Approach 1:

The patent changes the fundamental operating mechanism from charge trapping (Flash memory) to resistive switching (OxRRAM). This parameter change allows for much smaller device dimensions because resistive switching does not rely on charge storage in a trapping layer, eliminating the minimum thickness constraint. The memory effect is achieved through formation of conductive filaments in the oxide layer, which can occur in much thinner structures while maintaining data retention.

Inventive Principle:

Principle #35Parameter changes

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 allows for the stable formation of resistive memory cells with optimal resistance levels, similar to those formed by electrical stress, without damaging neighboring components, and reduces the need for expensive protective designs, achieving stable and cost-effective memory cell formation.

Implementation Method 1

at least one laser shot is emitted towards the layer of insulating material to make said layer of insulating material active by causing it to pass from a highly resistant state (state HRS) to a low resistance state (LRS state)

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentEP3379539B1Method for forming a non-volatile memory cell, non-volatile memory cell formed by this method and microelectronic device comprising such memory cells

Publication Date: 2023.08.09 COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES

Figure 1~4
Figure 5A~5B

AI summary

The invention relates to a method for forming (100) a non-volatile memory cell for switching said memory cell (10) from an unformed state to a formed state, said memory cell comprising an ordered stack of a lower electrode (12), a layer of insulating material (13), and an upper electrode (11). This forming method includes a breakdown operation (130) in which at least one laser pulse is fired at the layer of insulating material (13) to activate said layer of insulating material by switching it from a high resistance state (HRS state) to a low resistance state (LRS state), the memory cell being formed when the layer of insulating material is active. The invention also relates to a non-volatile memory cell (10) in which the layer of insulating material (13) is activated by the above forming method.