Oxide Semiconductor Transistor Cross-Shaped Channel Oxygen Desorption
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Solution Overview
Problem
Oxide semiconductor transistors face issues with abnormal electrical characteristics due to oxygen desorption during processing, leading to parasitic channels and low-resistance regions near the side surfaces, which affect the reliability and performance of the devices.
Innovation Solution
The transistor design includes an oxide semiconductor film etched into a cross shape with varying lengths, where the source and drain electrodes are positioned relative to the channel length and width, and the use of insulating films to manage oxygen levels, preventing oxygen desorption and reducing parasitic channel formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If oxygen is removed during processing, then the oxide semiconductor film can be formed, but parasitic channels form near side surfaces causing abnormal electrical characteristics
Solution Approach 1:
The patent applies preliminary anti-action by forming a protective insulating film covering the side surfaces of the oxide semiconductor film before processing. This protective layer prevents oxygen desorption from the side surfaces during subsequent heating or processing steps, thereby preventing the formation of low-resistance regions and parasitic channels that would degrade electrical characteristics.
Solution Approach 2:
The patent introduces an intermediary protective insulating film between the oxide semiconductor film and the processing environment. This intermediary layer acts as a barrier that prevents direct interaction between oxygen and the oxide semiconductor film side surfaces during heating, thus preventing oxygen desorption and the formation of parasitic channels while allowing the film formation process to proceed.
2Reliability
If the oxide semiconductor film is etched to have a cross shape, then parasitic channel formation is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs asymmetry by designing the oxide semiconductor film with a cross-shaped configuration where the length in the channel width direction is intentionally made larger than the length in the channel length direction. This asymmetric geometry increases the distance between side surfaces and the channel formation region, effectively reducing parasitic channel formation while the protective insulating film helps manage the increased manufacturing precision requirements.
Solution Approach 2:
The patent addresses the precision challenge by adding a spatial dimension solution - forming a protective insulating film on the side surfaces. This three-dimensional approach complements the cross-shaped planar design, providing protection against oxygen desorption at critical locations without requiring extremely tight etching tolerances, thus managing the manufacturing precision requirements.
3Reliability
If insulating films are added to prevent oxygen desorption, then electrical characteristics are maintained, but device complexity increases
Solution Approach 1:
The patent applies local quality by forming the protective insulating film specifically on the side surfaces of the oxide semiconductor film where oxygen desorption occurs, rather than uniformly across the entire device. This targeted approach maintains electrical characteristics by protecting critical regions while minimizing the addition of structural complexity to non-critical areas.
Solution Approach 2:
The patent segments the protective function by using the gate insulating film to provide protection for the upper surface while a separate protective insulating film covers the side surfaces. This segmentation allows each insulating layer to be optimized for its specific location and function, maintaining electrical characteristics without requiring a single complex protective structure.
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 design enhances the reliability and performance of oxide semiconductor transistors by reducing leakage currents and maintaining favorable electrical characteristics, even when oxygen desorbs from the semiconductor film.
Implementation Method 1
Oxygen (O) has been found to be likely to desorb from a side surface (end surface) of the oxide semiconductor film during a step for forming the oxide semiconductor film
Data Source
AI summary
Provided is a transistor which has favorable transistor characteristics and includes an oxide semiconductor, and a highly reliable semiconductor device which includes the transistor including the oxide semiconductor. In the semiconductor device including the transistor in which an oxide semiconductor film, a gate insulating film, and a gate electrode are stacked in this order, a sidewall insulating film is formed along side surfaces and a top surface of the gate electrode, and the oxide semiconductor film is subjected to etching treatment so as to have a cross shape having different lengths in the channel length direction or to have a larger length than a source electrode and a drain electrode in the channel width direction. Further, the source electrode and the drain electrode are formed in contact with the oxide semiconductor film.