Semiconductor Device Using Oxide Semiconductor for Low Power Data Retention
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Solution Overview
Problem
Current semiconductor devices, such as DRAM and SRAM, face challenges with short data holding periods due to leakage current, requiring frequent refresh operations and high power consumption, while flash memory suffers from limited write cycles and high voltage requirements, making them unsuitable for frequent data rewriting.
Innovation Solution
A semiconductor device utilizing an oxide semiconductor material with a p-channel writing transistor and a different semiconductor material for reading, allowing charge to be held at a node without the need for high voltage, enabling unlimited write cycles and low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DRAM is used to store data, then data can be stored in a volatile memory cell, but leakage current causes charge to be lost and requires frequent refresh operations increasing power consumption
Solution Approach 1:
The patent changes the material parameter of the transistor channel from conventional silicon to oxide semiconductor, which fundamentally alters the leakage current characteristic. This material substitution enables extremely low off-state current while maintaining reasonable on-state current, thereby achieving long data retention without frequent refresh operations and reducing power consumption significantly.
2Duration of action of stationary object
If flash memory is used to store data, then data can be retained for a long time without refresh operation, but high voltage is required for writing and erasing and the gate insulating layer deteriorates after predetermined number of writing operations
Solution Approach 1:
The patent changes the operating voltage parameter from high voltage (required for flash memory charge injection) to low voltage operation. By using oxide semiconductor transistors with their inherent low leakage current, the system achieves long data retention without requiring high voltage for writing, thereby preventing gate insulating layer deterioration and enabling unlimited write cycles.
Solution Approach 2:
The patent replaces the physical charge injection mechanism of flash memory (which causes mechanical stress and deterioration) with an electrical field-based switching mechanism using oxide semiconductor transistors. This substitution eliminates the need for high voltage tunneling current, thereby avoiding gate insulating layer damage and enabling unlimited write operations.
3Duration of action of stationary object
If flash memory is used to store data, then data can be retained permanently, but it takes a relatively long time to inject or remove charge and speed of writing and erasing data cannot be increased easily
Solution Approach 1:
The patent changes the material parameter of the transistor to oxide semiconductor, which enables faster switching speeds compared to conventional silicon transistors. The oxide semiconductor material provides superior mobility characteristics and faster charge transport, allowing data to be written and erased at high speeds while maintaining permanent storage capability.
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 semiconductor device achieves long-term data retention with minimal power consumption, high-speed operation, and no limitations on write cycles, improving reliability and reducing the need for complex peripheral circuits.
Implementation Method 1
a semiconductor device using a material which allows a sufficient reduction in off-state current of a transistor; for example, an oxide semiconductor material, which is a wide-gap semiconductor
Data Source
Figure 1A-1~1B
Figure 2A~2B
Figure 3
AI summary
A semiconductor device including a nonvolatile memory cell in which a writing transistor which includes an oxide semiconductor, a reading transistor which includes a semiconductor material different from that of the writing transistor, and a capacitor are included is provided. Data is written to the memory cell by turning on the writing transistor and applying a potential to a node where a source electrode (or a drain electrode) of the writing transistor, one electrode of the capacitor, and a gate electrode of the reading transistor are electrically connected, and then turning off the writing transistor, so that the predetermined amount of charge is held in the node. Further, when a p-channel transistor is used as the reading transistor, a reading potential is a positive potential.