Stacked Oxide Semiconductor Material for Low-Temperature High-Mobility Transistors
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Solution Overview
Problem
Conventional semiconductor materials like SiC and GaN require high-temperature processing, making them unsuitable for thin film or three-dimensional devices, and existing metal oxide semiconductors tend to be n-type, leading to normally-on transistors with high field-effect mobility but difficulty in controlling circuits.
Innovation Solution
A method for manufacturing stacked oxide materials involving the formation of c-axis-aligned oxide crystal components through sputtering and crystallization heat treatment, where the first oxide crystal component serves as a seed for the second, resulting in high-purity, intrinsic oxide semiconductors with low off-current and high field-effect mobility, enabling normally-off switching elements and low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional semiconductor materials like SiC and GaN are used, then high field-effect mobility is achieved, but high-temperature processing is required making them unsuitable for thin film or three-dimensional devices
Solution Approach 1:
The patent changes the material composition parameters by forming a specific four-layer stacked structure with In-Ga-Zn-O and In-Al-Zn-O oxide semiconductors in alternating layers. This compositional parameter change enables the material to achieve high crystallinity and field-effect mobility through crystal growth from the surface toward the inside at lower temperatures (below 1500°C), resolving the contradiction between achieving high mobility and avoiding high-temperature processing
Solution Approach 2:
The patent creates a composite material structure by stacking multiple oxide semiconductor layers with different compositions (In-Ga-Zn-O and In-Al-Zn-O) in an alternating pattern. This composite structure combines the advantages of different oxide materials to achieve both high field-effect mobility and low off-state current while enabling crystallization at lower temperatures through surface-initiated crystal growth
2Reliability
If existing metal oxide semiconductors are used, then n-type characteristics are achieved with high field-effect mobility, but normally-on transistors are formed making circuit control difficult
Solution Approach 1:
The patent applies local quality by creating regions with different oxide semiconductor compositions in the stacked structure. The alternating layers of In-Ga-Zn-O and In-Al-Zn-O provide locally optimized properties: some layers contribute to high mobility while others contribute to low off-state current. This local differentiation enables the transistor to achieve normally-off characteristics with high mobility, resolving the contradiction between mobility and controllability
Solution Approach 2:
The patent changes the material parameters by precisely controlling the composition ratios and stacking sequence of different oxide semiconductors. By adjusting the thickness and composition of each layer, the patent achieves parameter optimization that enables both high field-effect mobility and normally-off switching characteristics, allowing proper circuit control
3Reliability
If high crystallinity is achieved through conventional methods, then material quality is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by forming the oxide semiconductor layers with specific compositions and structures before the crystallization heat treatment. The alternating stacked structure is prepared in advance with controlled thickness and composition ratios, so that during subsequent heat treatment, crystal growth naturally proceeds from the surface toward the inside. This preliminary structuring simplifies the manufacturing process while achieving high crystallinity
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 approach allows for the production of transistors with high reliability, low power consumption, and stable electric characteristics, suitable for various applications including display panels and driver circuits, by achieving high crystallinity and reducing temperature-dependent current variations.
Implementation Method 1
formed by stacking films by a sputtering method
Implementation Method 2
the films are subjected to crystallization heat treatment
Implementation Method 3
causing crystal growth which proceeds from a surface toward an inside of the oxide component by heat treatment
Data Source
AI summary
One embodiment is a method for manufacturing a stacked oxide material, including the steps of forming a first oxide component over a base component, causing crystal growth which proceeds from a surface toward an inside of the first oxide component by first heat treatment to form a first oxide crystal component at least partly in contact with the base component, forming a second oxide component over the first oxide crystal component; and causing crystal growth by second heat treatment using the first oxide crystal component as a seed to form a second oxide crystal component.