Bismuth Halide RRAM for Low-Voltage, Lead-Free Memory

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Solution Overview

Problem

Existing resistance random access memory devices using oxide-based resistance change layers face challenges in manufacturing costs and environmental pollution due to the need for high-temperature vacuum processes and the use of lead-containing perovskite materials.

Innovation Solution

A resistance random access memory device is developed with a bismuth halide-based BiIxBr3-x thin film or Cs2AgBiBrxI6-x thin film having an elpasolite structure as the resistance change layer, which can change resistance due to ion movement or point defects, and is fabricated without lead, using a polymer protective layer and electrodes made from materials like Pt, Ti, and Ag, with a driving voltage range of −1.0 V to +1.0 V.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If oxide-based resistance change layer is used, then resistance change function is achieved, but high-temperature vacuum process is required increasing manufacturing cost

Engineering Contradiction:

Improveresistance change functionVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the material parameter from oxide-based resistance change layer to organic-inorganic hybrid perovskite material (APbX3), which enables resistance change function at lower temperatures and atmospheric pressure, eliminating the need for high-temperature vacuum processes and reducing manufacturing costs

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent adopts perovskite materials that can be fabricated using low-cost solution processing methods instead of expensive vacuum deposition, making the manufacturing process more economical and accessible

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Reliability

If oxide-based resistance change layer is used, then resistance change function is achieved, but lead-containing perovskite material causes environmental pollution

Engineering Contradiction:

Improveresistance change functionVSAvoidenvironmental pollution

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent extracts and removes the harmful lead (Pb) element from the perovskite structure, replacing it with environmentally friendly alternatives such as bismuth (Bi), tin (Sn), or germanium (Ge) to create lead-free perovskite materials that maintain resistance change function without environmental pollution

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent converts the harmful effect of lead-containing materials into a benefit by developing lead-free perovskite compositions that achieve comparable or superior performance while eliminating toxicity, turning an environmental liability into a sustainable solution

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If oxide-based resistance change layer is used, then resistance change function is achieved, but vacuum process requirement reduces manufacturing flexibility

Engineering Contradiction:

Improveresistance change functionVSAvoidmanufacturing flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent replaces the mechanical vacuum system with solution-based processing methods, allowing resistance change layers to be fabricated using simple coating techniques such as spin coating, dip coating, or inkjet printing at atmospheric pressure, significantly enhancing manufacturing flexibility and adaptability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The solution provides a low-voltage, high-efficiency memory device that overcomes environmental pollution concerns and reduces manufacturing costs, with a bismuth halide-based resistance change layer that operates effectively within a specific voltage range, enabling efficient data storage without the need for lead.

Implementation Method 1

the resistance change layer includes a bismuth halide-based BiIxBr3-x thin film (where 0≤x≤3) and/or a Cs2AgBiBrxI6-x thin film (where 0≤x≤6) having an elpasolite structure... may change in resistance due to the movement of I ions in the resistance change layer

Methodology Applied

Scientific EffectIon movement: Ion Exchange

Data Source

PatentUS11283019B2Resistance random access memory device and fabricating method of the same

Publication Date: 2022.03.22 RES & BUSINESS FOUND SUNGKYUNKWAN UNIV

AI summary

The present disclosure relates to a resistance random access memory device, including a first electrode, a resistance change layer formed on the first electrode, and a second electrode formed on the resistance change layer, and the resistance change layer includes a bismuth halide-based BiIxBr3-x thin film (where 0≤x≤3) and/or a Cs2AgBiBrxI6-x thin film (where 0≤x≤6) having an elpasolite structure.