Actuator Upper Electrode Sputtering Stress Control
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Solution Overview
Problem
Piezoelectric elements in actuator devices, such as those used in liquid-jet heads, face issues with film peeling and delamination due to film stress and quality, leading to compromised piezoelectric characteristics and displacement performance.
Innovation Solution
A method for producing actuator devices involves forming a piezoelectric element with a lower electrode, piezoelectric layer, and upper electrode, where the upper electrode is sputtered at specific temperature and pressure conditions to achieve optimal stress and resistance, enhancing adhesion and maintaining piezoelectric characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the upper electrode is formed by conventional sputtering methods, then the film can be deposited, but the electrode peels off the piezoelectric layer due to film stress and quality issues
Solution Approach 1:
The patent applies parameter changes by optimizing sputtering conditions including substrate temperature (25-250°C), pressure (0.4-1.5 Pa), and power density (3-30 kW/m²) to control the stress and film quality of the upper electrode, preventing peeling while maintaining adhesion
Solution Approach 2:
The patent uses composite material approach by selecting specific materials for the upper electrode (iridium or platinum) and controlling their deposition characteristics to achieve both adhesion to the piezoelectric layer and mechanical strength
2Reliability
If a stress relaxation layer is added between the piezoelectric layer and opposed film, then delamination is prevented to some degree, but the piezoelectric characteristics of the piezoelectric layer decline
Solution Approach 1:
The patent extracts the stress management function from the piezoelectric layer by forming the stress-relieving upper electrode directly on top of it through controlled sputtering, eliminating the need for an additional stress relaxation layer that would compromise piezoelectric properties
Solution Approach 2:
The upper electrode serves multiple functions: it provides electrical conductivity, mechanical protection, and stress management simultaneously, eliminating the need for separate functional layers
3Manufacturing precision
If lithography is used to form piezoelectric elements with high density, then fabrication precision is improved, but film peeling and delamination occur due to film stress
Solution Approach 1:
The patent changes the deposition parameters of the upper electrode (temperature, pressure, power density) to control film stress and prevent peeling, enabling high-density lithographic fabrication to proceed without adhesion failures
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 ensures improved adhesion of the upper electrode to the piezoelectric layer, maintaining satisfactory piezoelectric characteristics and achieving enhanced displacement and durability in actuator devices, resulting in improved ejection characteristics and reliability of liquid-jet heads.
Implementation Method 1
the upper electrode is formed on the piezoelectric layer by sputtering; a temperature of 25 to 250 (° C.) and a pressure of 0.4 to 1.5 (Pa) are used during the sputtering
Implementation Method 2
a piezoelectric layer comprising a piezoelectric material showing an electromechanical transducer function
Data Source
AI summary
A method for producing an actuator device, comprising the steps of: forming a vibration plate on a substrate; and forming a piezoelectric element composed of a lower electrode, a piezoelectric layer, and an upper electrode on the vibration plate, wherein in the step of forming the piezoelectric element, the upper electrode is formed on the piezoelectric layer by sputtering, a temperature of 25 to 250 (° C.) and a pressure of 0.4 to 1.5 (Pa) are used during the sputtering, and upon the sputtering, the upper electrode having a thickness of 30 to 100 (nm), stress of 0.3 to 2.0 (GPa), and specific resistance of 2.0 (×10−7 Ω·m) or less is formed.