Cross Point Memory Array Select Device Configuration
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Solution Overview
Problem
Existing memory technologies face challenges in efficiently reading and writing data using ferroelectric capacitors, as the act of reading reverses the polarization state, requiring immediate rewriting, and phase change memory materials are limited by high temperatures for phase transitions.
Innovation Solution
The development of an array of cross-point memory cells utilizing a select device and a programmable device in series, with a ferroelectric capacitor or phase change material, where the select device is electrically coupled to one of the lines and the programmable device is coupled to both lines, allowing for efficient data storage and retrieval without immediate rewriting, and using a U-shaped or L-shaped configuration for the select device to optimize material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If ferroelectric capacitor is used for non-volatile memory storage, then data retention is improved, but reading operation causes polarization reversal requiring immediate rewriting
Solution Approach 1:
A select device is introduced as an intermediary element between the read/write circuitry and the ferroelectric capacitor. This select device controls current flow to enable reading operations without causing unwanted polarization reversal in the memory cell, thus maintaining data integrity while enabling efficient read access.
Solution Approach 2:
The memory cell is segmented into distinct functional components: a select device and a programmable device (ferroelectric capacitor). The select device handles current control and read operations, while the programmable device maintains data storage. This segmentation allows independent optimization of read operations without affecting data retention.
2Duration of action of stationary object
If phase change material is used for non-volatile memory, then data retention is improved, but high temperatures are required for phase transitions
Solution Approach 1:
The patent modifies the physical and chemical parameters of the phase change material to reduce the temperature required for phase transitions. By changing material composition and structural parameters, the phase change occurs at lower temperatures, enabling non-volatile memory operation without excessive thermal requirements.
3Quantity of substance
If U-shaped or L-shaped configuration is used for select device, then material usage is optimized, but device fabrication complexity increases
Solution Approach 1:
The select device is configured in U-shaped or L-shaped geometries that allow a single continuous material layer to serve multiple functions and interconnect multiple memory cells. This merging approach optimizes material usage by eliminating redundant structures while the shapes are designed to be compatible with standard fabrication processes.
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 enables non-volatile data storage with reduced polarization reversal during reading and efficient phase transitions, improving the reliability and efficiency of memory cell operations.
Implementation Method 1
One type of capacitor is a ferroelectric capacitor which has ferroelectric material as at least part of the insulating material. Ferroelectric materials are characterized by having two stable polarized states and thereby can comprise programmable material of a memory cell.
Implementation Method 2
Energy as an electric field may be electrostatically stored within such material.
Implementation Method 3
Such memory uses a reversibly programmable material that has the property of switching between two different phases, for example between an amorphous disorderly phase and a crystalline or polycrystalline orderly phase.
Implementation Method 4
Starting from an amorphous state and rising to temperature above about 400° C., a rapid nucleation of crystallites may occur and, if the material is kept at the crystallization temperature for a sufficient time, it undergoes a phase change to become crystalline.
Data Source
AI summary
A method of forming an array of cross point memory cells comprises using two, and only two, masking steps to collectively pattern within the array spaced lower first lines, spaced upper second lines which cross the first lines, and individual programmable devices between the first lines and the second lines where such cross that have an upwardly open generally U-shape vertical cross-section of programmable material laterally between immediately adjacent of the first lines beneath individual of the upper second lines. Arrays of cross point memory cells independent of method of manufacture are disclosed.