Diode-Isolated Resistance-Switching Memory Cell for High-Density Arrays
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Solution Overview
Problem
Forming a large, high-density array of non-volatile memory cells using resistance-switching elements is challenging due to issues like disturbance between cells, high leakage currents, and fabrication difficulties.
Innovation Solution
A non-volatile memory cell comprising a diode and a resistance-switching element, where the resistance-switching element is made of a metal nitride compound with a thickness between 50 Angstroms and 400 Angstroms, paired with a diode to form a reliable and programmable memory cell, allowing for the creation of a monolithic three-dimensional memory array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If resistance-switching elements are used to form a large, high-density memory array, then memory density and capacity are improved, but cell disturbance and leakage currents increase
Solution Approach 1:
The memory cell is segmented into distinct functional regions: a first region containing the resistance-switching element and a second region containing the diode. This spatial segmentation isolates the high-density storage function from the control function, allowing the resistance-switching element to be closely packed for high density while the diode provides localized isolation to prevent cell disturbance.
Solution Approach 2:
The diode acts as an intermediary component between the resistance-switching element and neighboring cells. It mediates the electrical isolation, preventing leakage currents from affecting adjacent cells while allowing the resistance-switching element to maintain its high-density configuration.
2Quantity of substance
If resistance-switching elements are used to form a large, high-density memory array, then memory density is improved, but fabrication challenges increase
Solution Approach 1:
The memory cell structure is segmented into a first region with the resistance-switching element and a second region with the diode, allowing each component to be optimized and fabricated using different processes. This segmentation simplifies manufacturing by enabling independent optimization of each component's fabrication parameters.
Solution Approach 2:
The invention specifies particular parameter ranges for the resistance-switching element (50-400 Angstrom thickness) and uses materials with specific properties (metal nitride compounds, metal chalcogenides) to achieve reliable fabrication. These parameter specifications make the fabrication process more controllable and reproducible.
3Quantity of substance
If resistance-switching elements with thin layers are used, then memory density is improved, but leakage currents increase
Solution Approach 1:
The memory cell uses composite material structures: metal nitride compounds (Ni x O y, Nb x O y, Ti x O y, Hf x O y) and metal chalcogenides (CdS, CdSe, ZnS, ZnSe) for the resistance-switching element, combined with diode materials. These composite material systems provide both the thin-layer capability for high density and the electrical isolation needed to reduce leakage currents.
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
Enables the reliable fabrication and programming of a large, high-density non-volatile memory array by using a diode to isolate neighboring cells and prevent inadvertent programming, thereby addressing the challenges of cell disturbance and leakage currents.
Implementation Method 1
resistance-switching materials, which can reversibly be converted between a high-resistance state and a low-resistance state
Implementation Method 2
using a diode to isolate neighboring cells and prevent inadvertent programming
Data Source
Figure 1~2
Figure 3~4
Figure 5a~5b
AI summary
In a novel nonvolatile memory cell formed above a substrate, a diode is paired with a reversible resistance-switching material, preferably a metal oxide or nitride such as, for example, NixOy, NbxOy, TixOy, HfxOy, AlxOy, MgxOy, CoxOy, CrxOy, VxOy, ZnxOy, ZrxOy, BxNy, and AlxNy. In preferred embodiments, the diode is formed as a vertical pillar disposed between conductors. Multiple memory levels can be stacked to form a monolithic three dimensional memory array. In some embodiments, the diode comprises germanium or a germanium alloy, which can be deposited and crystallized at relatively low temperatures, allowing use of aluminum or copper in the conductors. The memory cell of the present invention can be used as a rewriteable memory cell or a one-time-programmable memory cell, and can store two or more data states.