Oxide Semiconductor Device With Nitrogen Control and Heat-Resistant Electrodes
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Solution Overview
Problem
The electric conductivity of oxide semiconductors can vary due to deviations in stoichiometric composition or the presence of hydrogen or water during manufacturing, leading to unstable electric characteristics in semiconductor devices.
Innovation Solution
A semiconductor device with an oxide semiconductor layer having a nitrogen concentration of 2×10^19 atoms/cm^3 or lower, using heat-resistant metals like tungsten, platinum, or molybdenum for electrodes to prevent oxygen bonding, and incorporating an oxygen-rich insulating layer to supply oxygen and prevent impurity entry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional materials and processes are used for oxide semiconductor devices, then manufacturing is easier and device structure is simpler, but electric characteristics become unstable due to oxygen deficiency and impurity entry
Solution Approach 1:
The device is divided into distinct functional layers: an oxide semiconductor layer with controlled oxygen content, a gate insulating layer, and heat-resistant metal electrodes. This segmentation allows each layer to be optimized independently for its specific function, particularly protecting the oxide semiconductor from oxygen deficiency while maintaining manufacturing feasibility
Solution Approach 2:
The gate insulating layer and heat-resistant metal electrodes are formed before the oxide semiconductor layer is fully processed. These layers serve as preliminary protective structures that prevent oxygen deficiency and impurity entry during subsequent manufacturing steps, ensuring stable electric characteristics from the outset
2Reliability
If nitrogen concentration in oxide semiconductor layer is reduced to 2×10^19 atoms/cm³ or lower, then oxygen concentration can be sufficiently high for stable characteristics, but manufacturing precision requirements increase
Solution Approach 1:
The invention specifies a quantitative threshold for nitrogen concentration (2×10^19 atoms/cm³ or lower) as a critical parameter. By establishing this precise parameter boundary, the patent enables manufacturers to control oxygen concentration and achieve stable electric characteristics through measurable and controllable means
3Reliability
If heat-resistant metals (tungsten, platinum, molybdenum) are used for source and drain electrodes, then oxygen bonding is prevented and reliability improves, but manufacturing cost increases
Solution Approach 1:
Heat-resistant metals are used specifically for the source and drain electrodes that directly contact the oxide semiconductor layer, where oxygen bonding would most adversely affect performance. This localized application of expensive materials provides maximum reliability benefit while minimizing overall manufacturing cost compared to using such materials throughout the entire device
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 stabilizes the electric characteristics and reliability of the semiconductor device, reducing variations in transistor performance due to light exposure and maintaining low temperature dependence.
Implementation Method 1
Nitrogen tends to be bonded to a metal included in the oxide semiconductor, and inhibits bonding between oxygen and the metal in the oxide semiconductor layer
Implementation Method 2
a heat-resistant metal which is unlikely to be oxidized is used for a source electrode and a drain electrode which are in contact with the oxide semiconductor layer
Data Source
AI summary
It is an object to provide a semiconductor device including an oxide semiconductor, which has stable electric characteristics and high reliability. A semiconductor device having a stacked-layer structure of a gate insulating layer; a first gate electrode in contact with one surface of the gate insulating layer; an oxide semiconductor layer in contact with the other surface of the gate insulating layer and overlapping with the first gate electrode; and a source electrode, a drain electrode, and an oxide insulating layer which are in contact with the oxide semiconductor layer is provided, in which the nitrogen concentration of the oxide semiconductor layer is 2×1019 atoms/cm3 or lower and the source electrode and the drain electrode include one or more of tungsten, platinum, and molybdenum.