Buffer Layers in Oxide Semiconductor Transistors for High Voltage Reliability
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Solution Overview
Problem
Transistors used in display devices face challenges with high voltage and large current reliability due to insufficient withstand voltage, primarily caused by oxidation reactions at the contact interface between electrode layers and oxide semiconductor layers, and the formation of parasitic channels from hydrogen, hydroxyl groups, or moisture in the channel etched parts.
Innovation Solution
The implementation of buffer layers with higher resistivity than the oxide semiconductor layer, made from materials like indium, zinc, or tin oxides, between the semiconductor layer and source/drain electrode layers to increase contact resistance and relieve electric field concentration, thereby enhancing the transistor's withstand voltage and preventing oxidation reactions and parasitic channel formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If buffer layers are provided between the oxide semiconductor layer and source/drain electrode layers to prevent oxidation reactions, then reliability is improved, but contact resistance increases
Solution Approach 1:
A buffer layer made of metal oxide (such as indium oxide, zinc oxide, or tin oxide) is introduced as an intermediary between the oxide semiconductor layer and the source/drain electrode layers. This buffer layer serves as a mediator that prevents direct contact between the electrode layers and the oxide semiconductor layer, thereby preventing oxidation reactions while maintaining controlled electrical characteristics.
Solution Approach 2:
The buffer layer is formed using metal oxide materials that have specific properties different from both the oxide semiconductor layer and the electrode layers. By using composite material structure (electrode layer + buffer layer + oxide semiconductor layer), the patent achieves both good electrical contact and protection against oxidation reactions.
2Object-affected harmful factors
If the oxide semiconductor layer is directly contacted with source/drain electrode layers to reduce contact resistance, then electrical conductivity is improved, but oxidation reactions occur reducing withstand voltage
Solution Approach 1:
The buffer layer acts as a protective intermediary that prevents direct contact between the electrode layers and the oxide semiconductor layer. This mediation prevents oxidation reactions at the interface, thereby maintaining high withstand voltage while the buffer layer itself provides adequate electrical conductivity for normal operation.
Solution Approach 2:
The buffer layer creates an inert environment between the electrode layers and the oxide semiconductor layer, preventing oxidation reactions by isolating the oxide semiconductor layer from oxygen-containing electrode materials. This inert barrier maintains the integrity and electrical properties of the oxide semiconductor layer.
3Reliability
If hydrogen concentration in the oxide semiconductor layer is reduced to prevent parasitic channel formation, then withstand voltage is improved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts the hydrogen removal function to a separate heat treatment process performed after the oxide semiconductor layer is formed. By conducting hydrogen removal heat treatment in a controlled atmosphere (such as nitrogen or rare gas atmosphere at high temperature), hydrogen and other impurities are effectively removed from the oxide semiconductor layer without requiring complex in-situ control during fabrication.
Solution Approach 2:
The heat treatment process is performed as a preliminary step before forming the electrode layers and buffer layers. This preliminary hydrogen removal ensures that the oxide semiconductor layer is properly prepared and free from parasitic channels before subsequent processing steps, simplifying the overall manufacturing process by establishing a clean baseline state.
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 use of buffer layers effectively increases the transistor's withstand voltage and reliability by reducing electric field concentration and preventing oxidation reactions, ensuring stable operation and improved switching characteristics.
Implementation Method 1
the buffer layer particularly relieves an electric field in the vicinity of a drain edge and improves the withstand voltage of the transistor
Implementation Method 2
oxidation reactions at the contact interface between electrode layers and oxide semiconductor layers
Data Source
AI summary
A transistor in a display device is expected to have higher withstand voltage, and it is an object to improve the reliability of a transistor which is driven by high voltage or large current. A semiconductor device includes a transistor in which buffer layers are provided between a semiconductor layer forming a channel formation region and source and drain electrode layers. The buffer layers are provided between the semiconductor layer forming a channel formation region and the source and drain electrode layers in order to particularly relieve an electric field in the vicinity of a drain edge and improve the withstand voltage of the transistor.