Semiconductor Memory Device Using Ion Conductor Cascade for Low Voltage Operation
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Solution Overview
Problem
Conventional semiconductor memory devices using diode characteristics face challenges in operating at low voltages and require high-temperature heat treatment for manufacturing, making it difficult to manufacture at relatively low temperatures and perform operations below the forward voltage of a pn diode.
Innovation Solution
A semiconductor memory device comprising a memory cell with a resistance change element and an ion conductor element connected in a cascade arrangement between bit lines and word lines, where the ion conductor element is formed of electrode films and an ion conductor film, and the resistance change element is formed of electrode films and a phase change film, allowing operation without the need for a forward voltage and reducing the required heat treatment temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon pn diode is used to achieve diode characteristics, then the device can operate with stable forward voltage characteristics, but it requires high-temperature heat treatment (not less than 750°C) to activate the P layer or N layer
Solution Approach 1:
The patent changes the material parameters by replacing silicon pn diodes with metal oxide semiconductors (such as IGZO - indium gallium zinc oxide) that can exhibit diode characteristics at lower temperatures. This material substitution allows the formation of functional layers without requiring high-temperature heat treatment above 750°C, while maintaining stable forward voltage characteristics through controlled deposition processes and compositional optimization
Solution Approach 2:
The patent employs composite material structures, specifically using metal oxide semiconductor compounds like IGZO combined with other functional materials to create a diode structure that achieves both low-temperature manufacturability and stable electrical characteristics. The composite nature of these materials allows for tailored properties that satisfy both the reliability and temperature constraints
2Reliability
If a silicon pn diode is used to achieve diode characteristics, then the device can provide sufficient forward voltage (Vf), but it becomes difficult to perform operations at low voltage not greater than Vf
Solution Approach 1:
The patent modifies the electrical parameters by using metal oxide semiconductors with adjustable bandgap and carrier mobility characteristics. By controlling the composition ratios (such as In:Ga:Zn ratios in IGZO) and deposition conditions, the forward voltage can be optimized to lower values while maintaining diode functionality, enabling operation at voltages suitable for modern low-power applications
Solution Approach 2:
The patent introduces dynamic adjustability in the diode characteristics through controllable material composition and structural parameters. The metal oxide semiconductor layers can be engineered with varying thicknesses, compositions, and doping levels to dynamically optimize the forward voltage characteristic according to specific application requirements, allowing flexibility in operating voltage selection
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 operation at low voltages and eliminates the need for high-temperature heat treatment, allowing for the manufacturing of semiconductor memory devices using diode characteristics at lower temperatures and reducing current consumption.
Implementation Method 1
an ion conductor element and a phase change element which are connected in a cascade arrangement between a bit line and a word line. The ion conductor element is configured of a lower electrode, an ion conductor film and an upper electrode
Implementation Method 2
the resistance change element is formed of the second electrode film, a phase change film and a third electrode film in a superposed manner
Data Source
AI summary
A semiconductor memory device comprising: first and second wirings arranged in a matrix; and a memory cell being provided at an intersecting point of the first and second wirings and including a resistance change element and an ion conductor element connected to each other in a cascade arrangement between the first and second wirings.