Oxide Semiconductor Device With Low Electronegativity Electrode Gettering
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Solution Overview
Problem
Semiconductor devices using oxide semiconductors face reliability issues due to impurities like hydrogen and water, leading to threshold voltage shifts and high off-state current, which affect power consumption and device performance.
Innovation Solution
A semiconductor device is manufactured with a conductive film made of metals with low electronegativity, such as titanium or molybdenum, in contact with the oxide semiconductor film to absorb and getter impurities like hydrogen, reducing their concentration and improving the purity and stability of the oxide semiconductor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional transistor structure is used without special impurity management, then the manufacturing process is simple, but the threshold voltage shifts over time due to impurity degradation
Solution Approach 1:
The patent applies preliminary action by forming a conductive film with low electronegativity metal (such as titanium, magnesium, or aluminum) that contacts the oxide semiconductor film before the transistor operation begins. This conductive film acts as a gettering layer that pre-absorbs hydrogen and water impurities from the oxide semiconductor film, preventing threshold voltage shifts during device operation. The conductive film is formed as part of the source/drain electrode structure, so the preliminary impurity absorption occurs during the manufacturing process itself.
Solution Approach 2:
The patent uses an intermediary approach by introducing a conductive film made of low electronegativity metal as a mediator between the source/drain electrodes and the oxide semiconductor film. This intermediary layer serves dual functions: it provides electrical conduction while simultaneously absorbing impurities (hydrogen and water) from the oxide semiconductor film through gettering effects. The low electronegativity of the metal enables it to attract and hold impurity atoms, preventing them from degrading the transistor characteristics.
2Loss of energy
If impurities like hydrogen and water are present in the oxide semiconductor film, then the manufacturing process is easier, but the off-state current increases and power consumption rises
Solution Approach 1:
The patent applies self-service by designing the conductive film with low electronegativity metal to automatically absorb and trap hydrogen and water impurities from the oxide semiconductor film through gettering. This self-service mechanism occurs passively during and after the film formation process, eliminating the need for additional complex purification steps. The low electronegativity metal inherently has a strong affinity for hydrogen and water, so it spontaneously reduces impurity concentrations to levels that minimize off-state current and power consumption.
3Manufacturing precision
If the conductive film is formed with low electronegativity metal to absorb impurities, then the oxide semiconductor purity increases, but the manufacturing process becomes more complex
Solution Approach 1:
The patent merges multiple functions into a single conductive film structure. The same conductive film that forms part of the source/drain electrode also serves as an impurity gettering layer. By using low electronegativity metal (such as titanium, magnesium, or aluminum) in the conductive film, the patent combines electrical conduction and impurity absorption functions in one layer, rather than requiring separate purification layers and electrode structures. This merging approach achieves high oxide semiconductor purity without proportionally increasing device complexity.
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 solution effectively reduces off-state current and stabilizes the threshold voltage, enhancing the reliability and reducing power consumption of semiconductor devices by minimizing impurity-induced degradation.
Implementation Method 1
a conductive film formed using a metal with a low electronegativity, specifically, a metal with an electronegativity lower than 2.1 which is the electronegativity of hydrogen, is formed so as to be in contact with an oxide semiconductor film, so that impurities such as hydrogen or water in the oxide semiconductor film are absorbed (gettered) by the conductive film
Data Source
AI summary
It is an object to provide a method for manufacturing a highly reliable semiconductor device having a thin film transistor formed using an oxide semiconductor and having stable electric characteristics. The semiconductor device includes an oxide semiconductor film overlapping with a gate electrode with a gate insulating film interposed therebetween; and a source electrode and a drain electrode which are in contact with the oxide semiconductor film. The source electrode and the drain electrode include a mixture, metal compound, or alloy containing one or more of a metal with a low electronegativity such as titanium, magnesium, yttrium, aluminum, tungsten, and molybdenum. The concentration of hydrogen in the source electrode and the drain electrode is 1.2 times, preferably 5 times or more as high as that of hydrogen in the oxide semiconductor film.