Low-Hydrogen Sputtering Target for Stable Oxide Semiconductor Transistors
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Solution Overview
Problem
Transistors using oxide semiconductors face challenges in controlling threshold voltage stability due to impurities like hydrogen-containing compounds, which affect carrier density and reliability.
Innovation Solution
A sputtering target with a sintered body of metal oxides such as magnesium, zinc, aluminum, gallium, and indium oxides is used, with hydrogen concentration below 1×10^16 atoms/cm^3, and silicon oxide added to inhibit crystallization, to form an oxide semiconductor film with reduced impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a transistor is manufactured using an oxide semiconductor film formed by conventional sputtering, then the manufacturing process is relatively simple and can be performed at low temperature, but the threshold voltage stability deteriorates due to impurities like hydrogen-containing compounds
Solution Approach 1:
The patent applies preliminary action by pre-treating the sputtering target with hydrogen removal processing before film formation. The target is heated to 100°C to 700°C in a vacuum or inert atmosphere to remove hydrogen and hydrogen-containing compounds from the target material, ensuring low-impurity film deposition without complicating the overall manufacturing process
Solution Approach 2:
The patent changes physical parameters by controlling the hydrogen concentration in the sputtering target to be 1×10^16 atoms/cm³ or less, and by controlling the deposition temperature and post-deposition heat treatment parameters. These parameter changes enable formation of oxide semiconductor films with carrier density of 1×10^12 to 1×10^18 atoms/cm³, achieving stable threshold voltage while maintaining simple manufacturing
2Quantity of substance
If impurities like hydrogen-containing compounds are present in the oxide semiconductor film, then the carrier density increases, but the threshold voltage control deteriorates and reliability decreases
Solution Approach 1:
The patent applies the extraction principle by removing hydrogen and hydrogen-containing compounds from the sputtering target through heat treatment in vacuum or inert atmosphere before film deposition. This extraction of impurities from the source material ensures that the deposited oxide semiconductor film has controlled carrier density and stable threshold voltage characteristics
Solution Approach 2:
The patent changes the chemical composition parameters by controlling hydrogen concentration in the target to 1×10^16 atoms/cm³ or less, and by controlling the oxide semiconductor stoichiometry (e.g., In-Ga-Zn-O ratio). These parameter changes enable precise control of carrier density while maintaining threshold voltage stability
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 approach results in a highly reliable oxide semiconductor film with controlled carrier density and improved threshold voltage stability, enhancing the performance and reliability of transistors.
Implementation Method 1
An oxide semiconductor film can be formed by a sputtering method
Implementation Method 2
a sintered body of at least one metal oxide selected from magnesium oxide, zinc oxide, aluminum oxide, gallium oxide, indium oxide, and tin oxide
Data Source
AI summary
One object is to provide a deposition technique for forming an oxide semiconductor film. By forming an oxide semiconductor film using a sputtering target including a sintered body of a metal oxide whose concentration of hydrogen contained is low, for example, lower than 1×1016 atoms/cm3, the oxide semiconductor film contains a small amount of impurities such as a compound containing hydrogen typified by H2O or a hydrogen atom. In addition, this oxide semiconductor film is used as an active layer of a transistor.