Amorphous Oxide Semiconductor Thin Film Selective Wet Etching
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Solution Overview
Problem
Current oxide semiconductor technologies face challenges in patterning electrodes using wet etching due to solubility issues in etching solutions, leading to low yield and high production costs, especially for amorphous oxide semiconductors like ZnO, which are insoluble in phosphoric acid-based solutions but soluble in oxalic acid-based ones, complicating the production of high-resolution, large-scale TFTs.
Innovation Solution
An amorphous oxide semiconductor thin film with a carrier density of less than 10^18 cm^-3, insoluble in phosphoric acid-based etching solutions but soluble in oxalic acid-based solutions, is developed by adjusting the indium, tin, and zinc atomic ratios, allowing for selective etching and reducing production costs through wet etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wet etching is used to pattern electrodes on oxide semiconductor films, then production cost is reduced and productivity is improved, but the oxide semiconductor film must be insoluble in the etching solution to prevent damage
Solution Approach 1:
The patent applies local quality by creating distinct etching resistance properties in different regions of the oxide semiconductor film. The active layer is made insoluble in phosphoric acid-based etching solutions through specific composition control (In/Ga ratio and carrier concentration), while allowing selective etching in other regions, thus enabling wet etching processes without damaging the functional semiconductor regions
Solution Approach 2:
The patent utilizes parameter changes by controlling the carrier concentration (10^16 to 10^18 cm^-3) and composition ratios (In/(In+Ga) = 0.1 to 0.9) of the oxide semiconductor film to achieve insolubility in phosphoric acid-based etching solutions. This allows the film to withstand wet etching processes that would otherwise damage it, enabling cost-effective and high-productivity manufacturing
2Speed
If amorphous oxide semiconductor like ZnO is used, then electron mobility is improved, but the film becomes soluble in oxalic acid-based etching solutions making wet etching difficult
Solution Approach 1:
The patent changes the chemical composition parameters of the oxide semiconductor by controlling the In/Ga ratio and carrier concentration to achieve insolubility in phosphoric acid-based etching solutions while maintaining high electron mobility. This allows amorphous oxide semiconductors to be processed using wet etching techniques
Solution Approach 2:
The patent adopts properties from crystalline oxide semiconductors (insolubility in phosphoric acid-based etching solutions) and applies them to amorphous oxide semiconductors through composition control, enabling amorphous films to exhibit both high electron mobility and etching resistance
3Manufacturing precision
If dry etching is used to pattern silicon-based semiconductors, then manufacturing precision is maintained, but equipment cost increases and productivity decreases
Solution Approach 1:
The patent changes the etching resistance properties of the oxide semiconductor film through composition control (In/Ga ratio and carrier concentration), enabling the use of wet etching processes that are more cost-effective and higher productivity compared to dry etching, while still achieving the required patterning precision
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 approach enables cost-effective and high-productivity production of TFTs with improved resolution and scalability by allowing wet etching of the semiconductor film and patterning electrodes, reducing the need for expensive dry etching and complex liftoff methods.
Implementation Method 1
The amorphous oxide semiconductor thin film is insoluble in a phosphoric acid-based etching solution and is soluble in an oxalic acid-based etching solution
Implementation Method 2
a sputtering target comprising indium, tin, zinc, a lanthanoid series element
Data Source
AI summary
This invention provides an amorphous oxide semiconductor thin film, which is insoluble in a phosphoric acid-based etching solution and is soluble in an oxalic acid-based etching solution by optimizing the amounts of indium, tin, and zinc, a method of producing the amorphous oxide semiconductor thin film, etc. An image display device (1) comprises a glass substrate (10), a liquid crystal (40) as a light control element, a bottom gate-type thin film transistor (1) for driving the liquid crystal (40), a pixel electrode (30), and an opposing electrode (50). The amorphous oxide semiconductor thin film (2) in the bottom gate-type thin film transistor (1) has a carrier density of less than 10+18 cm−3, is insoluble in a phosphoric acid-based etching liquid, and is soluble in an oxalic acid-based etching liquid.