Oxide Semiconductor Channel Structure for Stable High Mobility
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Solution Overview
Problem
Semiconductor devices with oxide semiconductor channels face challenges in maintaining stability due to oxygen defects in the insulating layer, leading to abnormal characteristics and reliability issues, as insufficient oxygen supply to the oxide semiconductor layer results in defects and reduced mobility.
Innovation Solution
A semiconductor device configuration with a polycrystalline oxide semiconductor layer, a metal oxide layer containing aluminum, and an insulating layer with a high oxygen content is used, where the insulating layer is designed to minimize defects and enhance oxygen supply, thereby improving mobility and reducing threshold voltage fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating layer is formed to supply oxygen to the oxide semiconductor layer, then oxygen defects are reduced and stability is improved, but the insulating layer may contain defects that reduce mobility
Solution Approach 1:
The insulating layer is divided into multiple layers: a first insulating layer in contact with the oxide semiconductor layer and a second insulating layer above it. The first insulating layer has lower oxygen concentration to avoid defects, while the second insulating layer has higher oxygen concentration to supply oxygen and improve stability. This segmentation resolves the contradiction by separating the conflicting requirements of defect minimization and oxygen supply.
Solution Approach 2:
Different regions of the insulating structure have different oxygen concentrations tailored to their specific functions. The first insulating layer has lower oxygen concentration (5-20 at%) to minimize defects and maintain high mobility, while the second insulating layer has higher oxygen concentration (20-40 at%) to supply oxygen and improve stability. This local differentiation of material properties resolves the contradiction between mobility and stability.
2Reliability
If oxygen is supplied to the oxide semiconductor layer to reduce defects, then stability is improved, but threshold voltage fluctuations occur
Solution Approach 1:
The oxygen supply function is segmented between two insulating layers. The first insulating layer provides a controlled, low-level oxygen environment that prevents excessive oxygen incorporation which would cause threshold voltage shifts. The second insulating layer provides additional oxygen supply to reduce defects. This segmentation allows simultaneous achievement of defect reduction and threshold voltage stability.
Solution Approach 2:
The oxygen concentration parameter is optimized differently in each insulating layer. The first insulating layer maintains oxygen concentration at 5-20 at% to prevent threshold voltage fluctuations, while the second insulating layer has oxygen concentration of 20-40 at% to supply oxygen for defect reduction. This parameter optimization resolves the contradiction between stability improvement and threshold voltage stability.
3Manufacturing precision
If a polycrystalline oxide semiconductor structure is used to improve mobility, then linear mobility increases, but oxygen defects may still form
Solution Approach 1:
The first insulating layer is formed immediately after the polycrystalline oxide semiconductor layer to provide a controlled oxygen environment during the critical early stages of device formation. This preliminary action prevents oxygen defects from forming in the polycrystalline structure while preserving the high mobility benefits, before the second insulating layer is added for additional oxygen supply.
Solution Approach 2:
The device structure combines polycrystalline oxide semiconductor material with a composite insulating layer system having different oxygen concentrations. The polycrystalline structure provides high mobility, while the composite insulating layers (with varying oxygen concentrations) provide defect reduction. This material combination resolves the contradiction between mobility enhancement and defect prevention.
Data Source
AI summary
A semiconductor device according to an embodiment of the present invention includes: a gate electrode; a gate insulating layer; a metal oxide layer containing aluminum as a main component above the gate insulating layer; an oxide semiconductor layer having a polycrystalline structure above the metal oxide layer; a source electrode and a drain electrode contacting the oxide semiconductor layer from above the oxide semiconductor layer; and an insulating layer above the source electrode and the drain electrode, wherein a linear mobility of the semiconductor device is larger than 20 cm2/Vs when (Vg−Vth)×Cox=5×10−7 C/cm2, in the case where the Vg is a voltage supplied to the gate electrode, the Vth is a threshold voltage of the semiconductor device, and the Cox is an electrostatic capacitance of the gate insulating layer sandwiched by the gate electrode and the oxide semiconductor layer.