Cross-Point Memory Cell Architecture with Select Device
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Solution Overview
Problem
Existing memory technologies face challenges in efficiently writing and reading data from ferroelectric and phase change memory cells, as the act of reading can often reverse the polarization state, requiring immediate re-write operations and affecting data retention in non-volatile memory systems.
Innovation Solution
The development of an array of cross-point memory cells comprising a select device and a programmable device in series, where the programmable device includes a ferroelectric capacitor or phase change material, allowing for stable data storage and retrieval without immediate re-write after reading, by utilizing conductive pillars and electrodes to manage electric fields and phase changes effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If ferroelectric capacitor is used in memory cell, then non-volatile data storage is achieved, but reading the memory state reverses the polarization state requiring immediate re-write
Solution Approach 1:
The memory cell is segmented into distinct functional components: a select device (diode or transistor) and a ferroelectric capacitor. This segmentation allows the read operation to be performed through the select device while the ferroelectric capacitor maintains its polarization state, preventing the read-disturb problem and eliminating the need for immediate re-write operations.
Solution Approach 2:
The select device acts as an intermediary between the read operation and the ferroelectric capacitor. By placing the select device in series with the capacitor, it mediates the read current flow in a way that does not reverse the capacitor's polarization, thus protecting the stored data while still enabling reading.
2Stability of the object's composition
If phase change material is used for memory, then stable data storage is achieved, but temperature control is required to maintain phase state
Solution Approach 1:
The patent utilizes phase change material that transitions between amorphous and crystalline phases to store data. The material's inherent phase stability at different temperature ranges allows for non-volatile storage without continuous temperature control, as the phase state is maintained once set.
Solution Approach 2:
The memory cell employs a composite structure combining phase change material with conductive pillars and electrodes. This composite architecture enables effective thermal management during programming while maintaining phase stability during normal operation and reading, reducing the need for continuous temperature control.
3Quantity of substance
If cross-point memory cell architecture is used, then data storage density is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent transitions from planar memory architecture to a three-dimensional cross-point architecture with vertical conductive pillars intersecting horizontal electrodes. This dimensional change enables higher memory cell density by utilizing vertical space, while the self-aligned nature of the cross-point intersections reduces manufacturing precision requirements compared to conventional approaches.
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 solution enables stable and efficient data storage and retrieval in non-volatile memory cells, reducing the need for immediate re-write operations and improving data retention by utilizing the bi-stable characteristics of ferroelectric or phase change materials within the cross-point memory cell architecture.
Implementation Method 1
A capacitor has two electrical conductors separated by electrically insulating material. Energy as an electric field may be electrostatically stored within such material. One type of capacitor is a ferroelectric capacitor which has ferroelectric material as at least part of the insulating material.
Implementation Method 2
Another type of non-volatile memory is phase change memory. 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. The two phases may be associated with resistivities of significantly different values.
Implementation Method 3
The development of an array of cross-point memory cells comprising a select device and a programmable device in series, where the programmable device includes a ferroelectric capacitor or phase change material, allowing for stable data storage and retrieval without immediate re-write after reading, by utilizing conductive pillars and electrodes to manage electric fields and phase changes effectively.
Implementation Method 4
Phase change can be obtained by locally increasing the temperature of the chalcogenide. Below 150° C., both phases are stable. 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 sufficiently long 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 forming spaced conductive lower electrode pillars for individual of the memory cells being formed along and elevationally over spaced lower first lines. Walls cross elevationally over the first lines and between the electrode pillars that are along the first lines. The electrode pillars and walls form spaced openings between the first lines. The openings are lined with programmable material of the memory cells being formed to less-than-fill the openings with the programmable material. Conductive upper electrode material is formed over the programmable material within remaining volume of the openings and spaced upper second lines are formed which cross the first lines elevationally over the conductive upper electrode material that is within the openings. A select device is between the lower electrode pillar and the underlying first line or is between the conductive upper electrode material and the overlying second line for the individual memory cells. Aspects of the invention include an array of cross point memory cells independent of method of manufacture.