Oxide Semiconductor Gate Stack Oxygen Supply for Stable Mobility
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Solution Overview
Problem
Existing semiconductor devices using oxide semiconductors for channels face challenges in supplying sufficient oxygen to the layer while minimizing defects, leading to unstable operation and variations in characteristics due to oxygen vacancies, particularly when high indium content is used.
Innovation Solution
A manufacturing method involving the formation of a gate insulating layer, a metal oxide layer containing aluminum, and subsequent heat treatment followed by removal of the metal oxide layer to supply oxygen to the oxide semiconductor layer, thereby repairing vacancies and reducing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating layer with more oxygen is formed to supply oxygen to the oxide semiconductor layer, then oxygen vacancies in the oxide semiconductor layer are reduced, but defects in the insulating layer increase causing electron-trapping and variation in device characteristics
Solution Approach 1:
The insulating layer is divided into two distinct layers: a first insulating layer formed with fewer defects (lower oxygen content) and a second insulating layer formed with more oxygen. This segmentation allows each layer to fulfill different functions - the first layer provides structural integrity with fewer defects, while the second layer supplies oxygen to reduce vacancies in the oxide semiconductor layer, thereby resolving the contradiction between reliability and harmful defects.
Solution Approach 2:
Different regions of the insulating structure are assigned different oxygen contents and defect densities. The first insulating layer has lower oxygen content and fewer defects, while the second insulating layer has higher oxygen content. This local quality differentiation enables the system to simultaneously achieve low electron-trapping (in the first layer) and sufficient oxygen supply (in the second layer), resolving the technical contradiction.
2Speed
If the ratio of indium in the oxide semiconductor layer is increased to achieve high mobility, then device mobility improves, but oxygen vacancies are more likely to form reducing reliability
Solution Approach 1:
The second insulating layer is pre-formed with high oxygen content before the oxide semiconductor layer is completely processed. During subsequent heat treatment, this oxygen-rich layer serves as an oxygen reservoir that actively supplies oxygen to the indium-rich oxide semiconductor layer, preventing oxygen vacancy formation. This preliminary action of oxygen supply enables the use of high indium content for mobility without suffering from reliability degradation due to oxygen vacancies.
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
The method achieves high mobility and reliability in semiconductor devices by efficiently supplying oxygen to the oxide semiconductor layer, reducing resistance, and minimizing defects, resulting in improved electrical characteristics.
Implementation Method 1
performing a heat treatment in a state where the metal oxide layer is formed above the gate insulating layer
Implementation Method 2
supply oxygen to the oxide semiconductor layer... forming a metal oxide layer containing aluminum as a main component above the gate insulating layer; performing a heat treatment
Data Source
AI summary
A method for manufacturing semiconductor device according to an embodiment includes; forming an oxide semiconductor layer above a substrate; forming a gate insulating layer above the oxide semiconductor layer; forming a metal oxide layer containing aluminum as a main component above the gate insulating layer; performing a heat treatment in a state where the metal oxide layer is formed above the gate insulating layer; removing the metal oxide layer after the heat treatment; and forming a gate electrode above the gate insulating layer.