Piezoelectric Film Phase Control for MEMS and Optical Elements
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing piezoelectric thin films, particularly those made from PZT, face challenges in maintaining satisfactory characteristics due to inversion of crystal phases from bulk to thin film states and compositional gradients, leading to suboptimal performance in devices like MEMS and optical elements.
Innovation Solution
A piezoelectric substance film with a structure that includes multiple crystal phases such as tetragonal, rhombohedral, pseudocubic, and monoclinic, with a gradual change in phase proportion along the film thickness direction, maintaining a constant composition within ±2%, and without layer-structured boundary planes, is developed. This film is formed using ABO3 type perovskite oxides like lead zirconate titanate (PZT) and relaxor materials, with specific dopants and orientations, to enhance stability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin film of perovskite type oxide is formed to utilize piezoelectric characteristics, then device characteristics can be improved, but crystal phase inversion occurs between bulk state and thin film state leading to unsatisfactory performance
Solution Approach 1:
The patent changes the compositional parameters of the PZT film, specifically controlling the Zr/(Zr+Ti) ratio within 0.40-0.65 and maintaining constant composition within ±2% across the film thickness. This parameter control prevents crystal phase inversion and ensures the film maintains the desired tetragonal or rhombohedral phase for satisfactory piezoelectric characteristics.
Solution Approach 2:
The patent ensures uniform composition and crystal phase distribution throughout the film thickness by controlling the compositional gradient to be within ±2%. This local quality control prevents phase inversion that would otherwise occur in conventional films with larger compositional variations.
2Shape
If a PZT film with compositional gradient is formed, then film structure can be controlled, but desired piezoelectric characteristics cannot be obtained
Solution Approach 1:
The patent optimizes the compositional parameters by limiting the Zr/(Zr+Ti) ratio to 0.40-0.65 and maintaining composition uniformity within ±2% across the film. This controlled parameter range achieves both the desired film structure and satisfactory piezoelectric characteristics, unlike films with larger compositional gradients.
3Reliability
If PZT film characteristics are optimized, then satisfactory performance can be achieved, but characteristics deteriorate when film thickness fluctuates
Solution Approach 1:
The patent controls the compositional parameters to maintain constant composition within ±2% across the film thickness and optimizes the Zr/(Zr+Ti) ratio. This parameter control ensures that the film characteristics remain stable and satisfactory even when film thickness fluctuates, as the composition uniformity compensates for thickness variations.
Solution Approach 2:
The patent ensures local quality uniformity throughout the film by maintaining constant composition within ±2% across the thickness direction. This uniformity ensures that any region of the film, regardless of local thickness variations, maintains the desired piezoelectric characteristics.
4Reliability
If mixed crystal phases are present in PZT film, then satisfactory characteristics can be obtained, but description is limited to specific orientations and compositions
Solution Approach 1:
The patent defines a broader applicable parameter range by specifying Zr/(Zr+Ti) ratio between 0.40-0.65 and composition uniformity within ±2%, which accommodates both tetragonal and rhombohedral phases. This parameter specification enables satisfactory characteristics to be achieved across different film orientations and thicknesses, increasing versatility.
Solution Approach 2:
The patent creates a universal film structure that can achieve satisfactory piezoelectric characteristics regardless of whether the dominant phase is tetragonal or rhombohedral, as long as the compositional parameters are controlled within the specified ranges. This multi-phase compatibility increases the adaptability of the invention to different device requirements.
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 provides films with improved precision, reproducibility, and transparency, maintaining satisfactory characteristics even with fluctuations in film thickness, suitable for high-performance MEMS and optical modulation elements.
Implementation Method 1
the piezoelectric substance film does not contain a layer-structured boundary plane, the crystal phase constituting the piezoelectric substance film includes at least two of a tetragonal, a rhombohedral, a pseudocubic, an orthorhombic and a monoclinic
Implementation Method 2
an optical element including, on a substrate, a first electrode, a ferroelectric substance film and a second electrode
Data Source
AI summary
An optical element satisfactory in transparency and characteristics as an optical modulation element, and a piezoelectric substance element satisfactory in precision and reproducibility as a fine element such as MEMS can be provided. The piezoelectric substance element includes, on a substrate, at least a first electrode, a piezoelectric substance film and a second electrode. The piezoelectric substance film does not contain a layer-structured boundary plane; the crystal phase constituting the piezoelectric substance film comprises at least two of a tetragonal, a rhombohedral, a pseudocubic, an orthorhombic and a monoclinic; and the piezoelectric substance film includes, in a portion in which a change in the composition is within a range of ±2%, a portion where a proportion of the different crystal phases changes gradually in a thickness direction of the film.