Oxide Semiconductor Device Insulating Layer Hydrogen Diffusion
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Solution Overview
Problem
The challenge lies in creating a practical oxide semiconductor device using a low temperature process that can maintain high resistance and stability, particularly on substrates with low heat resistance such as plastic, where existing barrier layers formed by PECVD contain high hydrogen levels, leading to reduced oxide semiconductor resistance.
Innovation Solution
A three-layer insulating structure is employed, comprising a first SiOx layer with low hydrogen content, a second SiNy layer with controlled hydrogen levels, and a third SiNz or SiOmNn layer with high hydrogen content, formed using PECVD, to effectively suppress hydrogen diffusion and maintain oxide semiconductor resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If PECVD is used to form barrier layer for suppressing gas transmission on plastic substrate, then productivity and film formation rate are improved, but hydrogen concentration in insulating layer increases causing oxide semiconductor resistance to decrease
Solution Approach 1:
The insulating layer is divided into three distinct layers: a first insulating layer (SiO2) in contact with oxide semiconductor, a second insulating layer (SiN4) in the middle, and a third insulating layer (SiN4) formed by PECVD on the substrate. This segmentation allows the high-productivity PECVD third layer to coexist with low-hydrogen first and second layers that protect the oxide semiconductor from hydrogen-induced resistance reduction.
Solution Approach 2:
The second insulating layer formed by sputtering acts as an intermediary barrier between the hydrogen-rich third insulating layer (PECVD) and the oxide semiconductor. This intermediate layer prevents hydrogen diffusion from the PECVD layer to the oxide semiconductor, allowing the use of high-productivity PECVD process while maintaining oxide semiconductor resistance.
2Productivity
If PECVD insulating layer is formed on oxide semiconductor, then manufacturing efficiency is improved, but hydrogen diffusion occurs reducing oxide semiconductor resistance
Solution Approach 1:
The first insulating layer (SiO2) and second insulating layer (SiN4) are formed by sputtering before forming the third insulating layer by PECVD. This preliminary action creates a low-hydrogen barrier structure in advance, preventing hydrogen diffusion from the subsequent PECVD layer to the oxide semiconductor, thus maintaining resistance control while enabling efficient PECVD processing.
3Temperature
If low temperature process (250°C or less) is used for plastic substrate, then substrate heat resistance requirement is reduced, but oxide semiconductor resistance becomes unstable due to hydrogen from barrier layers
Solution Approach 1:
The insulating layer uses a composite structure combining three different materials/layers: SiO2 (first insulating layer), SiN4 (second insulating layer), and SiN4 formed by PECVD (third insulating layer). This composite structure allows low-temperature processing compatible with plastic substrates while maintaining oxide semiconductor resistance stability through the hydrogen-blocking function of the first and second layers.
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 configuration allows for the stable formation of oxide semiconductor devices at temperatures of 250°C or less, preventing resistance reduction and ensuring high productivity, while using PECVD for barrier layer formation.
Implementation Method 1
a first insulating layer coming into contact with an oxide semiconductor, having a thickness of 50 nm or more, and including an oxide containing Si and O
Implementation Method 2
a second insulating layer coming into contact with the first insulating layer, having a thickness of 50 nm or more, and including a nitride containing Si and N
Implementation Method 3
As a formation method for the barrier layer, there is generally used PECVD which provides a higher film formation rate and excellent productivity
Data Source
AI summary
Provided is an oxide semiconductor device including an oxide semiconductor layer and an insulating layer coming into contact with the oxide semiconductor layer in which the insulating layer includes: a first insulating layer coming into contact with an oxide semiconductor, having a thickness of 50 nm or more, and including an oxide containing Si and O; a second insulating layer coming into contact with the first insulating layer, having a thickness of 50 nm or more, and including a nitride containing Si and N; and a third insulating layer coming into contact with the second insulating layer, the first insulating layer and the second insulating layer having hydrogen contents of 4×1021 atoms/cm3 or less, and the third insulating layer having a hydrogen content of more than 4×1021 atoms/cm3.