Nonvolatile Memory Device with Transition Metal Oxide Layers
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Solution Overview
Problem
Non-uniformity in initial breakdown voltages among nonvolatile memory elements leads to reduced yield and reliability, particularly when using iridium or its alloys as electrode materials, due to sensitivity to dimensional variations.
Innovation Solution
A nonvolatile memory device with a stacked-layer structure where the resistance variable layer includes an oxygen-deficient first transition metal oxide layer and a second transition metal oxide layer with higher oxygen content, ensuring the plug's end surface area is greater than the cross-sectional area of the conductive region, which stabilizes current density and reduces misalignment effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If iridium or its alloys are used as electrode materials, then electrical conductivity and stability are improved, but sensitivity to dimensional variations increases causing non-uniformity in initial breakdown voltages
Solution Approach 1:
The patent introduces an intermediate layer with specific material composition and controlled thickness between the electrode and resistance variable layer. This intermediate layer has different properties than the main electrode, creating a localized transition zone that compensates for dimensional variations and reduces sensitivity to manufacturing tolerances, thereby suppressing non-uniformity in initial breakdown voltages while maintaining the stability benefits of iridium-based electrodes
2Ease of manufacture
If the plug area is reduced to minimize misalignment effects, then manufacturing tolerance requirements are relaxed, but current density becomes more sensitive to dimensional variations
Solution Approach 1:
The patent optimizes the thickness and material composition of the intermediate layer to create a transition zone that maintains stable current density distribution. By carefully controlling the parameters of this intermediate structure, the design achieves robustness against both misalignment and dimensional variations, allowing for relaxed alignment tolerances while preventing current density non-uniformity
3Reliability
If a stacked-layer structure with oxygen-deficient and oxygen-rich transition metal oxide layers is used, then resistance change stability is improved, but device complexity increases
Solution Approach 1:
The resistance variable layer is segmented into multiple sub-layers with different oxygen contents (oxygen-deficient and oxygen-rich transition metal oxide layers). This segmentation allows each sub-layer to perform a specific function in the resistance switching mechanism, improving overall stability while maintaining a manageable structural complexity through systematic layering
4Speed
If the cross-sectional area of the conductive region is reduced to increase current density, then switching speed is improved, but non-uniformity in initial breakdown voltages increases
Solution Approach 1:
The intermediate layer acts as a mediator between the electrode and the narrow conductive path in the resistance variable layer. This intermediary structure ensures uniform electric field distribution and stable current density even when the conductive path cross-sectional area is small, allowing high switching speed to be achieved without increasing non-uniformity in initial breakdown voltages
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 suppresses non-uniformity in initial breakdown voltages, enhances yield, and improves reliability by ensuring current density is determined by the resistance variable layer's cross-sectional area, independent of misalignment, and reduces parasitic resistance.
Implementation Method 1
Oxidation or reduction are caused to take place selectively in a region of an interface between a transition metal oxide layer with a higher oxygen content and an electrode in contact with this transition metal oxide layer and thereby a resistance changing phenomenon is stabilized
Data Source
AI summary
Provided are a nonvolatile memory device which can suppress non-uniformity in initial breakdown voltages among nonvolatile memory elements and prevent reduction of yield, and a manufacturing method thereof. The nonvolatile memory device includes a nonvolatile memory element (108) having a stacked-layer structure in which a resistance variable layer (106) is parallel to a main surface of a substrate (117) and is planarized, and a plug (103) electrically connected to either a first electrode (105) or a second electrode (107), and an area of an end surface of a plug (103) at which the plug (103) and the nonvolatile memory element (108) are connected together, the end surface being parallel to the main surface of the substrate (117), is greater than a cross-sectional area of a cross-section of a first transition metal oxide layer (115) which is an electrically-conductive region, the cross-section being parallel to the main surface of the substrate (117).