Piezoelectric Element Buffer Layer Sc-Doped AlN Roughness
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Solution Overview
Problem
The use of Sc-doped AlN piezoelectric films in multi-morph structures leads to crystal structure distortion and surface roughness, resulting in deteriorated crystallinity and piezoelectricity of subsequent layers, limiting the sensitivity and driving force of piezoelectric elements.
Innovation Solution
A piezoelectric element with a multi-morph structure incorporating a buffer layer of undoped aluminum nitride between the piezoelectric layers to absorb surface roughness and improve crystallinity, along with scandium-doped aluminum nitride layers to enhance piezoelectric constants, and specific electrode materials like molybdenum for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If scandium is doped to AlN piezoelectric film to improve piezoelectric constant, then piezoelectric constant is improved, but crystal structure distortion and surface roughness occur
Solution Approach 1:
A buffer layer is introduced between the Sc-doped AlN piezoelectric layer and the upper AlN piezoelectric layer to act as an intermediary. This buffer layer absorbs the surface roughness caused by Sc doping and prevents it from propagating to subsequent layers, while allowing the Sc-doped layer to maintain its improved piezoelectric constant
Solution Approach 2:
The piezoelectric structure is segmented into multiple layers: a lower AlN piezoelectric layer, a Sc-doped AlN piezoelectric layer in the intermediate layer, and an upper AlN piezoelectric layer. This segmentation allows each layer to perform its specific function - the Sc-doped layer provides high piezoelectric constant while the undoped AlN layers maintain good crystallinity
2Power
If multi-morph structure with two or more piezoelectric film layers is formed to improve sensitivity and driving force, then sensitivity and driving force are improved, but crystallinity and piezoelectricity of second and subsequent layers deteriorate due to surface roughness from Sc doping
Solution Approach 1:
The buffer layer serves as a mediator between the Sc-doped piezoelectric layer and subsequent piezoelectric layers. It absorbs the harmful surface roughness from Sc doping while allowing the multi-morph structure to maintain its improved sensitivity and driving force
Solution Approach 2:
Different regions of the piezoelectric element have different compositions: the intermediate layer contains Sc-doped AlN for high piezoelectric constant, while the upper piezoelectric layer uses undoped AlN for good crystallinity. This local quality differentiation allows each region to optimize its function
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 proposed structure reduces crystallinity and piezoelectricity degradation, enhancing sensitivity and driving force by improving the crystallinity and piezoelectric characteristics of subsequent layers, as verified through experimental results showing improved surface roughness and piezoelectric constants.
Implementation Method 1
a piezoelectric element including a substrate, a lower electrode layer on the substrate, an intermediate layer on the lower electrode layer, and an upper electrode layer on the intermediate layer. The intermediate layer includes a first piezoelectric layer including an aluminum nitride as a main component
Data Source
AI summary
A piezoelectric element that includes a substrate, a lower electrode layer on the substrate, an intermediate layer on the lower electrode layer, and an upper electrode layer on the intermediate layer. The intermediate layer includes a first piezoelectric layer including an aluminum nitride as a main component thereof and located between the lower electrode layer and the upper electrode layer, a first buffer layer including an aluminum nitride as a main component and located between the first piezoelectric layer and the upper electrode layer, a first intermediate electrode layer located between the first buffer layer and the upper electrode layer, and a second piezoelectric layer located between the first intermediate electrode layer and the upper electrode layer.