Piezoelectric Element OH Interface Layer for High Withstand Voltage
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Solution Overview
Problem
Existing piezoelectric elements face challenges in achieving high withstand voltage and drive stability without deteriorating piezoelectric characteristics, as methods to improve withstand voltage, such as adding additives or introducing seed layers, often compromise piezoelectric constants or increase process complexity.
Innovation Solution
A piezoelectric element with a specific configuration that includes a lower electrode, a piezoelectric film containing a perovskite-type oxide, and an upper electrode layer, where the region closest to the piezoelectric film is composed of an oxide conductive layer, and an interface layer with an amorphous structure containing an OH group, with a peak intensity ratio γ/α of binding energies satisfying certain conditions, enhancing the interface between the piezoelectric film and the upper electrode layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additives are added to improve crystallinity and withstand voltage, then the withstand voltage is improved, but the piezoelectric constant decreases
Solution Approach 1:
The patent introduces an interface layer as an intermediary between the piezoelectric film and the upper electrode. This interface layer contains an OH group that acts as a mediator to improve the interface quality and charge balance, thereby enhancing withstand voltage without requiring additives in the piezoelectric film itself, thus preserving the piezoelectric constant.
Solution Approach 2:
The patent changes the chemical composition parameter of the interface by introducing an OH group-containing layer with specific thickness (1-10 nm) and specific OH group concentration. This parameter change at the interface improves the charge balance and withstand voltage without altering the bulk piezoelectric material composition, thus maintaining high piezoelectric constant.
2Reliability
If a buffer layer (seed layer) is provided to improve crystallinity, then the withstand voltage is improved, but the process load increases
Solution Approach 1:
The patent merges the functions of the buffer layer and the upper electrode by making the upper electrode itself contain the OH group and have the specific interface characteristics. This eliminates the need for a separate buffer layer while achieving the same effect of improving crystallinity and withstand voltage, thus reducing process complexity.
Solution Approach 2:
The upper electrode in the patent is designed to serve multiple functions: it acts as both the electrical electrode and the buffer/interface layer that promotes crystallinity and improves withstand voltage. This multi-functionality eliminates the need for additional dedicated buffer layers, reducing process load while maintaining the benefits.
3Manufacturing precision
If the piezoelectric film thickness is increased to improve performance, then the piezoelectric characteristics are improved, but the drive voltage requirement increases
Solution Approach 1:
The patent changes the interfacial parameter by introducing the OH group-containing interface layer, which improves the charge balance and reduces leakage current. This allows thinner piezoelectric films to achieve the same performance, thereby maintaining high piezoelectric characteristics while reducing the drive voltage requirement compared to thicker films.
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 configuration achieves high withstand voltage and drive stability without deteriorating piezoelectric characteristics, with improved piezoelectricity and stability through the inclusion of an OH group-containing interface layer.
Implementation Method 1
an interface layer containing a constituent element of the oxide conductive layer and an OH group is provided between the piezoelectric film and the oxide conductive layer
Implementation Method 2
a piezoelectric element including, on a substrate in the following order, a lower electrode layer, a piezoelectric film containing a perovskite-type oxide as a main component, and an upper electrode layer
Data Source
Figure 1~2
Figure 3~4
Figure 5A~5B
AI summary
There are provided a piezoelectric element and a manufacturing method for a piezoelectric element, which realize high withstand voltage and drive stability without deteriorating piezoelectric characteristics. In a piezoelectric element including, on a substrate in the following order, a lower electrode layer, a piezoelectric film containing a perovskite-type oxide as a main component, and an upper electrode layer, the upper electrode layer includes an oxide conductive layer, has an interface layer containing a constituent element of the oxide conductive layer and an OH group, between the piezoelectric film and the oxide conductive layer of the upper electrode layer, where the interface layer has an amorphous structure and has a thickness of 1 nm or more and 5 nm or less, and in an intensity profile of binding energy in the interface layer, which is acquired by an X-ray photoelectron spectroscopy measurement, in a case where a peak intensity of binding energy derived from a 1s orbital of oxygen bonded to a metal is denoted as α, and a peak intensity of binding energy derived from a 1s orbital of oxygen constituting the OH group is denoted as γ, a peak intensity ratio γ/α is 0.35 or more.