Oxide Semiconductor Transistor Interface Stability via Metal Oxide Layer
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Solution Overview
Problem
Oxide semiconductor transistors face reliability issues due to charge trapping at the interface between the active layer and the interfacial stability layer, leading to fluctuations in electric characteristics and low reliability.
Innovation Solution
A layered structure is introduced with a metal oxide film acting as a channel protective film, containing constituents similar to the oxide semiconductor film, and an insulating film with different constituents, to suppress charge trapping and enhance interface stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an interfacial stability layer with same characteristics as gate insulating layer is used, then manufacturing is simplified, but charge trapping occurs at the interface leading to threshold voltage fluctuation
Solution Approach 1:
The patent applies local quality by creating distinct regions with different properties: the interfacial stability layer has different characteristics from both the gate insulating layer and the oxide semiconductor layer. This localized differentiation at the interface region prevents charge trapping while maintaining manufacturing feasibility through a structured layered approach.
Solution Approach 2:
The interfacial stability layer serves as an intermediary between the gate insulating layer and the oxide semiconductor layer. It mediates the interface properties to prevent charge trapping, acting as a buffer zone with controlled characteristics that are optimized for interface stability rather than being identical to either adjacent layer.
2Reliability
If a metal oxide film containing constituents similar to oxide semiconductor film is introduced, then charge trapping at oxide semiconductor interface is suppressed, but device structure becomes more complex
Solution Approach 1:
The patent employs composite materials by introducing a metal oxide film that contains constituents similar to the oxide semiconductor film. This composite structure at the interface provides compatible electronic properties that suppress charge trapping, while the film can be integrated into existing manufacturing processes.
Solution Approach 2:
The patent applies parameter changes by carefully controlling the composition and properties of the metal oxide film. By adjusting parameters such as constituent ratios, thickness, and formation conditions, the film achieves optimal charge trapping suppression while maintaining compatibility with standard device fabrication processes.
Data Source
AI summary
An object is to provide a semiconductor device using an oxide semiconductor having stable electric characteristics and high reliability. A transistor including the oxide semiconductor film in which a top surface portion of the oxide semiconductor film is provided with a metal oxide film containing a constituent similar to that of the oxide semiconductor film and functioning as a channel protective film is provided. In addition, the oxide semiconductor film used for an active layer of the transistor is an oxide semiconductor film highly purified to be electrically i-type (intrinsic) by heat treatment in which impurities such as hydrogen, moisture, a hydroxyl group, or a hydride are removed from the oxide semiconductor and oxygen which is a major constituent of the oxide semiconductor and is reduced concurrently with a step of removing impurities is supplied.