C-Axis Aligned Sputtering Target for Reliable Oxide TFT Films
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Solution Overview
Problem
Transistors formed using oxide semiconductors often have lower reliability compared to those formed using amorphous silicon, due to issues with crystal structure and impurity contamination.
Innovation Solution
A sputtering target with an oxide semiconductor having a crystal region where the c-axis is parallel to the normal vector of the top surface is used, along with specific deposition conditions such as low surface temperature, reduced impurity contamination, and optimized substrate temperature and oxygen gas proportion, to deposit an oxide semiconductor film with a crystal region aligned in the same direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If oxide semiconductor is used as semiconductor thin film material, then alternative to silicon-based materials is achieved, but reliability is inferior to amorphous silicon transistors
Solution Approach 1:
The patent changes the crystal structure parameters of the oxide semiconductor by controlling the sputtering process to form a c-axis aligned crystalline structure. This parameter change in crystal orientation resolves the reliability issue while maintaining the material alternative benefit
Solution Approach 2:
The patent creates local crystal orientation quality by aligning c-axes perpendicular to the film surface in specific regions. This local quality improvement in crystal structure enhances transistor reliability without requiring complete structural transformation
2Ease of manufacture
If sputtering method is used to deposit oxide semiconductor film, then deposition capability is achieved, but crystal structure alignment and impurity control are challenging
Solution Approach 1:
The patent performs preliminary action by preparing the sputtering target with specific crystal orientation (c-axis perpendicular to target surface) before deposition. This preliminary preparation ensures that the deposited film inherits the aligned crystal structure, achieving manufacturing precision through advance preparation
Solution Approach 2:
The patent replaces mechanical mixing or physical alignment methods with a field-based sputtering process. By using plasma field to deposit atoms from the oriented target, the crystal structure alignment is transferred to the film without mechanical intervention
3Productivity
If conventional sputtering target is used, then deposition is achieved, but crystal region alignment with c-axis parallel to normal vector is not obtained
Solution Approach 1:
The patent changes the physical parameter of the sputtering target by orienting the crystal structure so that c-axes are parallel to the normal vector of the target surface. This parameter change in target crystal orientation directly produces the desired film alignment while maintaining deposition efficiency
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 results in a highly reliable transistor with reduced defect and impurity levels, improved crystal structure alignment, and increased film density, leading to enhanced semiconductor device performance.
Implementation Method 1
An oxide semiconductor film is deposited by a sputtering method, using a sputtering target including an oxide semiconductor having a crystal region in which the direction of c-axis is parallel to a normal vector of the top surface of the oxide semiconductor
Data Source
AI summary
There have been cases where transistors formed using oxide semiconductors are inferior in reliability to transistors formed using amorphous silicon. Thus, in the present invention, a semiconductor device including a highly reliable transistor formed using an oxide semiconductor is manufactured. An oxide semiconductor film is deposited by a sputtering method, using a sputtering target including an oxide semiconductor having crystallinity, and in which the direction of the c-axis of a crystal is parallel to a normal vector of the top surface of the oxide semiconductor. The target is formed by mixing raw materials so that its composition ratio can obtain a crystal structure.