Epitaxial Piezoelectric Thin Film for MEMS Scanner Flatness
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Solution Overview
Problem
Existing piezoelectric thin film devices used in MEMS scanners have insufficient surface flatness due to the lack of crystallinity and domain area orientation, leading to inadequate arithmetic average roughness and reflective efficiency.
Innovation Solution
A piezoelectric element is fabricated using a substrate with a predetermined orientation, where a piezoelectric thin film is grown epitaxially using physical vapor deposition or chemical vapor deposition methods, resulting in higher crystallinity and improved surface flatness, with a multilayer structure that includes a lower electrode, piezoelectric thin film, and upper electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a sol gel process is used to form a piezoelectric thin film, then the film can be formed on the substrate, but the crystallinity and domain area orientation are insufficient, leading to poor surface flatness
Solution Approach 1:
The patent changes the formation method parameters from sol gel process to epitaxial growth using PVD or CVD methods. This parameter change enables the piezoelectric thin film to be formed with high crystallinity and proper domain area orientation, achieving arithmetic average roughness of 5 nm or less, thereby resolving the contradiction between ease of manufacture and manufacturing precision.
2Manufacturing precision
If a multilayer film is formed by photoresist between the piezoelectric thin film and reflective film layer, then the structure can be created, but the interface crystallinity is not improved, resulting in insufficient flatness
Solution Approach 1:
The patent changes the material and formation parameters of the intermediate layer from photoresist-based multilayer film to a thin film formed by epitaxial growth. This parameter change improves the interface crystallinity and flatness while reducing the need for complex multilayer structures, achieving arithmetic average roughness of 5 nm or less at the interface with the reflective film layer.
3Reliability
If the piezoelectric thin film has insufficient crystallinity, then the film can be formed easily, but the arithmetic average coarseness increases due to grain boundaries, reducing reflective efficiency
Solution Approach 1:
The patent changes the formation method from sol gel process to epitaxial growth using PVD or CVD, which fundamentally alters the crystal structure development. This parameter change eliminates grain boundary formation by creating a single-crystal or highly-oriented polycrystal structure, achieving arithmetic average coarseness of 5 nm or less and improving reflective efficiency for MEMS scanner applications.
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 enhances the crystallinity and surface flatness of the piezoelectric thin film, improving the reflective efficiency and image quality in MEMS scanners by reducing the arithmetic average roughness, allowing for sharper and more focused projections.
Implementation Method 1
The piezoelectric thin film is epitaxially grown on the lower electrode using a physical vapor deposition method or a chemical vapor deposition method
Implementation Method 2
The piezoelectric thin film is epitaxially grown on the lower electrode using a physical vapor deposition method or a chemical vapor deposition method
Implementation Method 3
The piezoelectric thin film is epitaxially grown on the lower electrode using a physical vapor deposition method or a chemical vapor deposition method
Implementation Method 4
A voltage is impressed between the lower electrode and the upper electrode to deform the piezoelectric thin film
Data Source
AI summary
A piezoelectric element includes a substrate having a first surface with a predetermined orientation; a lower electrode layered on the first surface of the substrate; a piezoelectric thin film layered on the lower electrode and having a piezoelectric body; and an upper electrode layered on the piezoelectric thin film. A voltage is to be impressed between the lower electrode and the upper electrode to deform the piezoelectric thin film. The piezoelectric thin film is epitaxially grown on the lower electrode using a physical vapor deposition or a chemical vapor deposition.