Oxide Semiconductor Transistor with C-Axis Aligned Crystals
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Solution Overview
Problem
Transistors using amorphous oxide semiconductor films face reliability issues due to unstable physical properties and high defect states, leading to variations in threshold voltage and increased power consumption.
Innovation Solution
A semiconductor device with an oxide semiconductor layer comprising crystalline regions, including a first region with nanocrystals and a second region with c-axis aligned crystals, which reduces defect states and enhances reliability by suppressing changes in electrical characteristics under light irradiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an amorphous oxide semiconductor film is used to form a transistor, then the transistor can be manufactured with ease and relatively simple processes, but the physical properties become unstable and reliability deteriorates due to high defect states and threshold voltage variations
Solution Approach 1:
The invention changes the crystalline state parameter of the oxide semiconductor from amorphous to crystalline. By forming a crystalline oxide semiconductor film with specific crystal structures (such as c-axis aligned crystalline oxide semiconductor), the material achieves stable physical properties and low defect states while maintaining manufacturability through controlled crystal growth processes
Solution Approach 2:
The invention creates a composite structure by combining crystalline oxide semiconductor regions with specific crystal orientations. The structure includes a first region with c-axis aligned crystalline oxide semiconductor and a second region with different crystal orientation, forming a composite material that optimizes both electrical characteristics and reliability
2Ease of manufacture
If an amorphous oxide semiconductor film is used, then manufacturing is simpler, but off-state current increases and power consumption rises due to unstable electrical characteristics
Solution Approach 1:
By changing the oxide semiconductor from amorphous to crystalline state with specific crystal orientations, the invention reduces off-state current and stabilizes electrical characteristics, thereby reducing power consumption in active devices while maintaining ease of manufacture through controlled crystallization processes
3Device complexity
If an amorphous oxide semiconductor film is used, then the manufacturing process is less complex, but threshold voltage varies and deteriorates due to high defect states
Solution Approach 1:
The invention changes the crystalline structure parameter from amorphous to crystalline oxide semiconductor with specific orientations. This parameter change reduces defect states and stabilizes threshold voltage, achieving high manufacturing precision while keeping device structure relatively simple
Solution Approach 2:
The invention applies local quality by creating regions with different crystal orientations within the oxide semiconductor film. The first region has c-axis aligned crystalline oxide semiconductor for stable threshold voltage, while the second region has different orientation, optimizing local electrical characteristics to achieve overall device stability
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 proposed structure provides a highly reliable semiconductor device with low off-state current, stable threshold voltage, and reduced power consumption, improving the reliability and performance of transistors by minimizing defect states and electrical variations.
Implementation Method 1
the oxide semiconductor layer includes a first region having a crystal whose size is less than or equal to 10 nm and a second region which overlaps with the insulating layer with the first region provided therebetween and which includes a crystal part whose c-axis is aligned in a direction parallel to a normal vector of a surface of the oxide semiconductor layer
Data Source
AI summary
A highly reliable semiconductor device including an oxide semiconductor is provided. Provided is a semiconductor device including an oxide semiconductor layer, an insulating layer in contact with the oxide semiconductor layer, a gate electrode layer overlapping with the oxide semiconductor layer, and a source electrode layer and a drain electrode layer electrically connected to the oxide semiconductor layer. The oxide semiconductor layer includes a first region having a crystal whose size is less than or equal to 10 nm and a second region which overlaps with the insulating layer with the first region provided therebetween and which includes a crystal part whose c-axis is aligned in a direction parallel to a normal vector of the surface of the oxide semiconductor layer.