Ferroelectric Memory Capacitor Arrays for Non-Destructive Readout
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Solution Overview
Problem
Existing memory technologies using ferroelectric capacitors face challenges in maintaining the polarization state during reading operations, often requiring immediate re-write after reading, which can lead to data loss and inefficiency.
Innovation Solution
The method involves forming arrays of capacitors and memory cells with a specific structure that includes rows and columns of transistors, horizontally-spaced openings, and a common upper capacitor electrode, where a capacitor insulator and upper capacitor electrode are formed over lower capacitor electrodes, and a horizontally-elongated conductive line connects the upper electrodes across groups, allowing for efficient data storage and retrieval without reversing the polarization state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ferroelectric capacitors are used for non-volatile memory storage, then data retention capability is improved, but reading operations may reverse the polarization state causing data loss
Solution Approach 1:
The memory array is divided into multiple independently addressable memory cells, each with its own transistor and capacitor. This segmentation allows selective reading of individual cells without affecting the polarization state of other cells, enabling non-destructive read operations while maintaining data retention capability.
Solution Approach 2:
A transistor is introduced as an intermediary between the read circuitry and the ferroelectric capacitor. The transistor acts as a controlled switch that allows reading operations to be performed without directly disturbing the capacitor's polarization state, thus preventing data loss while maintaining non-volatile storage.
2Reliability
If immediate re-write is performed after reading to maintain polarization state, then data integrity is improved, but operational efficiency deteriorates
Solution Approach 1:
The memory cell structure is designed with the transistor and capacitor in a specific configuration where the read operation itself is made non-destructive. This preliminary design eliminates the need for subsequent re-write operations, as the polarization state is preserved during reading, thereby improving operational efficiency while maintaining data integrity.
3Ease of manufacture
If arrays of memory cells are formed with specific structures including common upper capacitor electrode, then manufacturing complexity is reduced, but device functionality must be maintained
Solution Approach 1:
Multiple capacitors in the memory array share a common upper electrode structure. This merging of electrode elements simplifies the manufacturing process by reducing the number of separate electrode formation steps, while the individual capacitors maintain their distinct lower electrodes and insulation layers to preserve device functionality and electrical isolation.
Solution Approach 2:
The common upper capacitor electrode serves multiple functions: it acts as one electrode for multiple individual capacitors, provides a shared reference potential, and simplifies the interconnect structure. This multi-functionality reduces manufacturing complexity while maintaining the required device functionality through proper electrical isolation of individual memory cells.
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 approach enables non-volatile memory storage with reduced data loss and improved efficiency by maintaining the polarization state during read operations, enhancing the reliability and performance of memory arrays.
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.
Implementation Method 2
One type of non-volatile 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 capacitor and/or memory cell. The polarization state of the ferroelectric material can be changed by application of suitable programming voltages and remains after removal of the programming voltage
Data Source
AI summary
A method of forming an array of capacitors comprises forming rows and columns of horizontally-spaced openings in a sacrificial material. Fill material is formed in multiple of the columns of the openings and lower capacitor electrodes a are formed in a plurality of the columns that are between the columns of the openings comprising the fill material therein. The fill material is of different composition from that of the lower capacitor electrodes. The fill material is between a plurality of horizontally-spaced groups that individually comprises the lower capacitor electrodes. Immediately-adjacent of the groups are horizontally spaced apart from one another by a gap that comprises at least one of the columns of the openings comprising the fill material therein. The sacrificial material is removed to expose laterally-outer sides of the lower capacitor electrodes. A capacitor insulator is formed over tops and the laterally-outer sides of the lower capacitor electrodes. Upper capacitor electrode material is formed over the capacitor insulator and the lower capacitor electrodes. A horizontally-elongated conductive line is formed atop individual of the groups that directly electrically couple together the upper capacitor electrode material there-below in that individual group.