Mixed FeRAM OxRAM Memory Cells for Energy-Efficient Computing

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Solution Overview

Problem

On-board computers executing calculation algorithms require large memory capacity for numerous write and read operations, leading to energy-intensive systems with limited robustness, especially in mobile applications like telephony and autonomous vehicles.

Innovation Solution

A data storage circuit with non-volatile memory cells configurable between ferroelectric and resistive memory technologies, allowing adaptation based on operational phases with high write endurance and low energy consumption for writing, and high read endurance and low energy for reading.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single non-volatile memory technology is used, then the memory structure is simple, but the energy performance and robustness deteriorate under intensive read and write operations

Engineering Contradiction:
Improvememory structureVSAvoidenergy consumption
Core Design Contradiction:
Device complexityVSUse of energy by moving object

Solution Approach 1:

The patent divides the memory system into two distinct segments: FeRAM memory cells for write-intensive operations and OxRAM memory cells for read-intensive operations. Each segment is optimized for its specific operational requirements, with FeRAM providing low-energy write capability and OxRAM providing high-endurance read capability. This segmentation resolves the contradiction by allowing the system to achieve low energy consumption without requiring a single complex memory structure to handle all operation types.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent creates a universal memory system that can perform both write-intensive and read-intensive operations by integrating two different memory technologies. The mixed FeRAM-OxRAM architecture provides multi-functionality, enabling the same memory system to adapt to different operational phases (training vs. inference) and thereby resolve the contradiction between structural simplicity and energy efficiency across diverse workloads.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Use of energy by moving object

If FeRAM is used for write operations, then write energy is low, but read endurance is insufficient for intensive read operations

Engineering Contradiction:
Improvewrite energyVSAvoidread endurance
Core Design Contradiction:
Use of energy by moving objectVSReliability

Solution Approach 1:

The patent segments the memory functionality by assigning FeRAM cells specifically to handle write operations where low energy consumption is critical, while OxRAM cells handle read operations where high endurance is critical. This functional segmentation allows FeRAM to operate within its optimal performance envelope without being subjected to intensive read operations that would degrade its reliability.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent applies local quality by optimizing different parts of the memory system for different operational requirements. FeRAM cells are optimized with properties suitable for low-energy writing, while OxRAM cells are optimized with properties suitable for high-endurance reading. Each local component has qualities tailored to its specific function, resolving the contradiction between write energy efficiency and read endurance.

Inventive Principle:
Principle #3Local quality

3Reliability

If OxRAM is used for read operations, then read endurance is high, but write cyclability is insufficient for intensive write operations

Engineering Contradiction:
Improveread enduranceVSAvoidwrite cyclability
Core Design Contradiction:
ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent segments the operational workload by directing write-intensive tasks to FeRAM cells and read-intensive tasks to OxRAM cells. This segmentation protects OxRAM cells from intensive write operations that would limit their write cyclability, while still allowing them to excel at read operations where their high endurance is fully utilized.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent optimizes local qualities by designing OxRAM cells with properties specifically suited for high-endurance reading, while FeRAM cells are designed with properties optimized for write cyclability. Each memory type operates in its zone of optimal performance, resolving the contradiction between read endurance and write cyclability.

Inventive Principle:
Principle #3Local quality

4Quantity of substance

If memory capacity is increased to store more calculation variables, then algorithm execution is enabled, but energy consumption increases

Engineering Contradiction:
Improvememory capacityVSAvoidenergy consumption
Core Design Contradiction:
Quantity of substanceVSUse of energy by moving object

Solution Approach 1:

The patent changes the operational parameters by switching between two different memory technologies based on the operational phase. During training phases requiring intensive writes, FeRAM is activated with its low write energy parameter. During inference phases requiring intensive reads, OxRAM is activated with its high read endurance parameter. This dynamic parameter change allows large memory capacity to be utilized without proportionally increasing energy consumption.

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

The solution enhances energy performance and technological robustness by optimizing memory operations according to the phase of the calculation algorithm, reducing energy consumption and extending the lifespan of memory cells.

Implementation Method 1

The memory component comprises a stack of thin layers in the following order: a first layer of an electrically conductive material forming a lower electrode, a second layer of a dielectric and ferroelectric material, a third layer of electrically conductive material forming an upper electrode

Methodology Applied
Scientific EffectFerroelectric polarization: Polarisation

Implementation Method 2

variable conductive filament resistive memory technology (OxRAM or ReRAM) has high read endurance and low read energy making it more efficient for performing a calculation operation requiring a considerable number of readings of the stored data

Methodology Applied
Scientific EffectResistive switching: Electrical Resistance

Data Source

PatentEP4195207B1Oxram/feram mixed technology nonvolatile memories
Publication Date: 2024.08.28 COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES
  • EP4195207B1 patent drawingFigure 1a~1b
  • EP4195207B1 patent drawingFigure 1c
  • EP4195207B1 patent drawingFigure 2a

AI summary

A data storage circuit comprises an array of configurable, non-volatile (NVM) memory cells, each designed to operate in one of two configurations. The first configuration (CONF1) corresponds to a ferroelectric memory with variable electrical bias, and the second configuration (CONF2) corresponds to a resistive memory with a variable conductive filament. Each memory cell includes a first layer (C1) of an electrically conductive material forming a lower electrode (EL1), a second layer (C2) of a dielectric and ferroelectric material, and a third layer (C3) of an electrically conductive material forming an upper electrode (EL2).