Oxide Semiconductor Gate Stack for Oxygen-Stable Transistor Operation
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Solution Overview
Problem
Semiconductor devices with oxide semiconductor channels face challenges in maintaining high mobility and reliability due to oxygen deficiencies and defects in the insulating layer, leading to variations in electrical characteristics.
Innovation Solution
A semiconductor device configuration with a titanium-containing layer and a conductive layer in the gate electrode, and a gate insulating layer with varying thickness regions, where the titanium-containing layer is 50% or less of the gate insulating layer's thickness, helps in supplying oxygen to the oxide semiconductor layer and reducing defects, thereby achieving stable and reliable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating layer is formed with high oxygen content to supply oxygen to the oxide semiconductor layer, then oxygen supply is improved, but defects are generated in the insulating layer causing abnormal characteristics and variations in reliability test
Solution Approach 1:
The gate insulating layer is divided into a first region (overlapping the gate electrode) and a second region (not overlapping the gate electrode), with different thicknesses. The first region has a thickness of 50 nm or less to reduce oxygen supply, while the second region has a greater thickness to provide oxygen reservoir without causing defects in the channel region.
Solution Approach 2:
Different regions of the gate insulating layer are given different oxygen concentrations and thicknesses tailored to their specific functions. The first region has lower oxygen content to prevent defects in the active channel area, while the second region has higher oxygen content to serve as an oxygen source without interfering with channel characteristics.
2Reliability
If the thickness of the gate insulating layer is increased to supply more oxygen, then oxygen supply is improved, but normally-on electrical characteristics occur
Solution Approach 1:
The gate insulating layer is segmented into regions with different thicknesses. The first region directly above the channel has controlled thickness (50 nm or less) to prevent excess oxygen supply that causes normally-on characteristics, while the second region extends beyond the gate electrode to provide oxygen reservoir functionality.
Solution Approach 2:
The titanium-containing layer serves as an intermediary between the gate insulating layer and the oxide semiconductor layer. It has selective oxygen permeability, allowing controlled oxygen transfer to the channel region while preventing uncontrolled oxygen diffusion that would lead to normally-on characteristics.
3Reliability
If a thick titanium-containing layer is used in the gate electrode, then oxygen supply to oxide semiconductor is improved, but etching time increases and gate insulating layer is removed by over-etching
Solution Approach 1:
The thickness of the titanium-containing layer is precisely controlled to be 50 nm or less, optimizing the balance between oxygen supply capability and etching time. This parameter optimization ensures sufficient oxygen permeability while maintaining reasonable manufacturing cycle time and preventing over-etching of the gate insulating layer.
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 ensures high mobility and suppresses normally-on electrical characteristics, reducing in-plane variations in the transistor's electrical characteristics and enhancing the reliability of the semiconductor device.
Implementation Method 1
the titanium-containing layer is 50% or less than a thickness of the gate insulating layer in the first region... helps in supplying oxygen to the oxide semiconductor layer
Data Source
AI summary
A semiconductor device according to an embodiment includes an oxide semiconductor layer provided above an insulating surface, a gate insulating layer provided above the oxide semiconductor layer, and a gate electrode provided above the oxide semiconductor layer via the gate insulating layer, wherein the gate electrode has a titanium-containing layer and a conductive layer in order from the gate insulating layer side, the gate insulating layer includes a first region overlapping the gate electrode and a second region not overlapping the gate electrode, and a thickness of the titanium-containing layer is 50% or less than a thickness of the gate insulating layer in the first region.