Oxide Semiconductor Transistor Nitrogen Gradient Interface
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Solution Overview
Problem
The electric characteristics of transistors using oxide semiconductor layers are often degraded due to the amorphous state of the interface between the oxide semiconductor layer and the insulating film, leading to variations in performance.
Innovation Solution
A concentration gradient of nitrogen is introduced in the oxide semiconductor layer near the interface with the gate insulating layer to enhance crystallinity and stability, with specific nitrogen and oxygen concentration profiles achieved through controlled sputtering methods, forming regions with high crystallinity and aligned crystal structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the interface between oxide semiconductor layer and insulating film is amorphous, then the manufacturing process is simple, but the electric characteristics of transistor are degraded
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of nitrogen within the oxide semiconductor layer, where the nitrogen concentration is higher near the interface with the gate insulating layer and decreases toward the top surface. This localized nitrogen addition promotes crystallinity specifically at the critical interface region without requiring the entire layer to be crystalline, thus improving electric characteristics while maintaining manufacturing feasibility
Solution Approach 2:
The patent changes the chemical composition parameter by introducing nitrogen into the oxide semiconductor layer with a controlled concentration gradient. This parameter change transforms the interface region from amorphous to crystalline state, improving the electric characteristics such as field-effect mobility and threshold voltage stability
2Reliability
If nitrogen is added to enhance crystallinity at the interface, then the electric characteristics improve, but the manufacturing process complexity increases
Solution Approach 1:
The patent applies preliminary action by forming the nitrogen-containing oxide semiconductor layer with a concentration gradient before subsequent processing steps. The nitrogen is incorporated during the sputtering process itself, preparing the interface region in advance to achieve desired crystallinity and electric characteristics without requiring additional post-processing steps
Solution Approach 2:
The manufacturing process complexity is managed by controlling the nitrogen concentration gradient through sputtering parameters such as gas flow rates and power conditions. By adjusting these parameters, the desired concentration profile is achieved in a single deposition process, avoiding the need for multiple sequential steps
3Reliability
If a concentration gradient of nitrogen is formed in the oxide semiconductor layer, then the field-effect mobility increases, but the manufacturing precision requirements increase
Solution Approach 1:
The patent controls the nitrogen concentration gradient by adjusting sputtering parameters including gas flow rates of oxygen and nitrogen, RF power, and pressure conditions. These parameter changes enable precise control over the nitrogen incorporation and its spatial distribution, achieving the desired concentration profile that enhances field-effect mobility
Solution Approach 2:
The patent employs feedback control by monitoring the relationship between sputtering parameters and the resulting nitrogen concentration profile. By establishing correlations between process conditions and material properties, the manufacturing process can be optimized and controlled to achieve consistent results
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 results in improved electric characteristics, such as higher field-effect mobility and reduced threshold voltage variation, while maintaining high productivity and stability of the transistor.
Implementation Method 1
a concentration gradient of nitrogen is formed in the oxide semiconductor layer, and a region containing much nitrogen is provided at the interface with the gate insulating layer. By the addition of nitrogen, a region with high crystallinity can be formed
Implementation Method 2
much oxygen be contained in a region in the vicinity of an interface between the oxide semiconductor layer and an insulating film (protective insulating layer) in contact with the oxide semiconductor layer. Specifically, a concentration gradient of oxygen is formed in the oxide semiconductor layer
Data Source
AI summary
An object is to provide a transistor in which the state of an interface between an oxide semiconductor layer and an insulating film (gate insulating layer) in contact with the oxide semiconductor layer is favorable; and a method for manufacturing the transistor. In order to obtain the transistor, nitrogen is added to a region of the oxide semiconductor layer in the vicinity of the interface with the gate insulating layer. Specifically, a concentration gradient of nitrogen is formed in the oxide semiconductor layer, and a region containing much nitrogen is provided at the interface with the gate insulating layer. By the addition of nitrogen, a region with high crystallinity can be formed in the region of the oxide semiconductor layer in the vicinity of the interface with the gate insulating layer, so that a stable interface state can be obtained.