MIIM Diode Metal Oxide Memory Cell Low Temperature
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Solution Overview
Problem
Conventional resistance varying memory devices face challenges with silicon-based diodes, including high deposition and impurity activation temperatures, which lead to heat load difficulties and yield reduction, and the deterioration of insulating films due to forming operations, resulting in unstable memory cell operations.
Innovation Solution
A nonvolatile memory device utilizing a variable resistor with a first metal oxide film and a diode formed from a second metal oxide film, where the diode includes a MIIM structure with a higher concentration of silicon or aluminum, and a metal/oxygen ratio, to reduce voltage across the rectifier layer and enhance data retention and disturb resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a silicon-based diode is adopted for the diode, then the memory cell structure is established, but deposition and impurity activation temperatures rise, leading to heat load and difficulty in multiple stacking
Solution Approach 1:
The patent changes the material composition parameters of the diode from silicon-based to a metal oxide-based MIIM structure, which fundamentally alters the deposition temperature requirements. This material substitution enables low-temperature deposition processes while maintaining diode functionality, directly resolving the heat load issue in multiple stacking.
Solution Approach 2:
The patent employs a composite MIIM diode structure consisting of multiple metal oxide layers with different properties. This composite approach allows optimization of each layer's characteristics, achieving both low deposition temperature and proper diode rectification behavior, thereby enabling multiple stacking without excessive heat accumulation.
2Ease of manufacture
If a silicon-based diode is adopted for the diode, then the memory cell structure is established, but impurity activation temperatures rise, leading to heat load and difficulty in multiple stacking
Solution Approach 1:
The patent changes the material system from silicon-based to metal oxide-based, which eliminates the need for high-temperature impurity activation processes. The metal oxide materials inherently provide the required electrical properties without requiring high-temperature activation, thus reducing the thermal load for multiple stacking.
3Ease of operation
If conventional forming operation is applied to the variable resistor, then a current path is formed in the initial state, but the insulating film deteriorates, leading to read disturb and program disturb
Solution Approach 1:
The patent applies local quality by creating an asymmetric structure where the anode side has a larger cross-sectional area than the cathode side. This geometric differentiation localizes the forming operation effects to specific regions, preventing widespread deterioration of the insulating film while still achieving the necessary current path formation.
Solution Approach 2:
The patent implements beforehand cushioning by designing the MIIM diode structure with specific metal oxide layers that act as protective barriers. These layers are configured to absorb and dissipate the stress from forming operations before it can reach and damage the insulating film, thus preventing read disturb and program disturb.
4Length of moving object
If film thinning is performed in the silicon-based diode, then the aspect ratio increases, but this is a main cause of worsening yield
Solution Approach 1:
The patent changes the material system to metal oxides, which have different physical and chemical properties compared to silicon. This material substitution allows for easier and more controlled film thinning processes that do not result in excessive aspect ratios, thereby maintaining manufacturing precision and yield.
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
The configuration suppresses deterioration of insulating films, improves data retention, and reduces program and read disturb issues, enabling stable operation of memory cells with a lower voltage application.
Implementation Method 1
a variable resistor (22) including a first metal oxide film (26) and configured to reversibly change resistance value by energy application
Implementation Method 2
a MIIM diode which is formed by stacking two or more kinds of insulating films having different band gaps and permittivities
Implementation Method 3
a MIIM diode which is formed by stacking two or more kinds of insulating films having different band gaps and permittivities
Data Source
AI summary
According to one embodiment, a nonvolatile memory device comprises a plurality of first lines, a plurality of second lines, and memory cells. Each of the memory cells comprise a variable resistor, and a diode. The variable resistor includes a first metal oxide film and is configured to reversibly change resistance value by energy application. The diode includes a second metal oxide film and is connected in series to the variable resistor. The first metal oxide film has at least one of dielectric constant lower than that of the second metal oxide film and physical film thickness greater than that of the second metal oxide film.