Mixed Metal Oxide Channel Composition for Low-Temperature TFTs
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Solution Overview
Problem
Current materials used for the channel in thin-film transistors (TFTs) face challenges such as low electron mobility, low chemical stability, and the need for high-temperature deposition, which can damage existing memory cells in 3D memory devices.
Innovation Solution
A mixed metal oxide comprising specific proportions of Mg, Zn, and either Al or Ga, along with oxygen and minimal impurities, is developed. This oxide is deposited at temperatures below 400°C, ensuring compatibility with silicon technology and stability against forming gas anneal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If crystalline materials are used for the channel, then electron mobility is improved, but deposition temperature must be increased above 400°C which damages existing memory cells
Solution Approach 1:
The patent uses a composite material system consisting of InGaZnO4 as the base material with MgO and Al2O3 dopants. This composite approach allows the material to maintain amorphous structure at low deposition temperatures (below 400°C) while achieving electron mobility comparable to crystalline materials through the synergistic interaction of multiple metal cations and controlled doping.
Solution Approach 2:
The patent changes the compositional parameters by introducing specific ratios of Mg (0.01-0.50 parts by mole) and Al (0.01-0.50 parts by mole) dopants into the InGaZnO4 system. These parameter changes optimize the electron mobility and chemical stability of the amorphous channel material without requiring high-temperature crystallization.
2Temperature
If amorphous materials are used for the channel, then deposition temperature is reduced below 400°C, but electron mobility and chemical stability deteriorate
Solution Approach 1:
The patent optimizes the compositional parameters by introducing Mg and Al dopants in controlled amounts (0.01-0.50 parts by mole each) into the InGaZnO4 amorphous system. This parameter optimization enhances electron mobility and chemical stability while maintaining the amorphous structure that enables low-temperature deposition below 400°C.
Solution Approach 2:
The patent introduces localized doping with Mg and Al elements at specific concentration ranges within the amorphous InGaZnO4 matrix. This local quality modification creates optimized regions that enhance electron transport properties and chemical stability without requiring global crystallization, thus maintaining low deposition temperature compatibility.
3Temperature
If amorphous materials are used for the channel, then deposition temperature is reduced below 400°C, but chemical stability against forming gas anneal deteriorates
Solution Approach 1:
The patent modifies the compositional parameters by incorporating Mg and Al dopants in optimized ratios (0.01-0.50 parts by mole each) into the amorphous InGaZnO4 system. These compositional changes enhance the chemical stability of the amorphous channel material against forming gas anneal while preserving the low deposition temperature advantage.
Solution Approach 2:
The patent creates a composite amorphous material system where InGaZnO4 is combined with MgO and Al2O3 components. This composite structure provides enhanced chemical stability and resistance to forming gas anneal degradation while maintaining the amorphous phase that enables low-temperature processing below 400°C.
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 mixed metal oxide achieves high electron mobility, high on-currents, low off-currents, and excellent chemical stability, making it suitable for use in TFTs and 3D memory devices without damaging existing components.
Implementation Method 1
a method for forming the oxide comprising depositing a magnesium oxide, a zinc oxide, and an oxide of a third element selected from Al and Ga
Data Source
AI summary
In an aspect, a mixed metal oxide comprises or consists essentially of: a mixture comprises or consisting essentially of 0.30 to 0.69 parts by mole Mg, 0.20 to 0.69 parts by mole Zn, 0.01 to 0.30 parts by mole of a third element selected from Al and Ga, and, either, when the third element is Al, 0.00 to 0.31 parts by mole of other elements selected from metals and metalloids, or, when the third element is Ga, 0.00 to 0.15 parts by mole of other elements selected from metals and metalloids, wherein the sum of all parts by mole of Mg, Zn, the third element, and the other elements amounts to 1.00, wherein the amount in parts by mole of the other elements is lower than the amount in parts by mole of Mg and is lower than the amount in parts by mole of Zn; oxygen; and less than 0.01 parts by mole of non-metallic and non-metalloid impurities.