Piezoelectric Liquid Ejection Head Etching with Plasma Endpoint Control
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Solution Overview
Problem
Existing liquid ejection heads face issues with inconsistent control of protection film thickness on piezoelectric elements, leading to variations in displacement amount and potential damage to the piezoelectric membrane, especially when using water-based ink, due to the exposure of upper electrodes during plasma etching.
Innovation Solution
A manufacturing method that uses an end point detector (EPD) to stabilize the etching process, ensuring precise control of protection film thickness by monitoring plasma emission spectra, thereby reducing the film thickness over the piezoelectric element while maintaining the integrity of the piezoelectric membrane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the protection film thickness is reduced to expose the upper electrode, then the displacement amount of the piezoelectric element is improved, but the long-term reliability of the piezoelectric element deteriorates due to insufficient sealing and plasma damage
Solution Approach 1:
The patent applies local quality by creating a multi-layer protection film structure where different regions have different thicknesses. The first protection film is thinner to allow sufficient displacement, while the second protection film is thicker to provide enhanced sealing and prevent plasma damage to the piezoelectric membrane. This localized variation in film thickness resolves the contradiction between achieving adequate displacement and maintaining long-term reliability.
2Ease of manufacture
If the etching time is controlled to manage the remaining protection film amount, then the manufacturing process is simplified, but the stability of the protection film thickness deteriorates due to variations in etching rate and apparatus state
Solution Approach 1:
The patent implements feedback control in the etching process by using an end-point detector to monitor the etching progress in real-time. The etching is automatically terminated when the detector identifies the exposure of the upper electrode, ensuring consistent protection film thickness across different wafers and etching sessions. This feedback mechanism compensates for variations in etching rate caused by changes in apparatus state, thereby improving manufacturing precision while maintaining ease of manufacture.
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
Stabilizes the thickness of the protection film, ensuring consistent displacement performance of the piezoelectric element and preventing damage, thus enhancing the reliability and efficiency of the liquid ejection head.
Implementation Method 1
monitoring plasma emission spectra
Implementation Method 2
monitoring plasma emission spectra
Implementation Method 3
etching the protection film
Data Source
AI summary
A manufacturing method of a liquid ejection head including an element substrate including a piezoelectric element including a first electrode, a piezoelectric membrane, and a second electrode on a surface of a substrate in this order, wiring connected to the piezoelectric element, a terminal for supplying an electric signal and connected to the wiring, an inorganic structure arranged at a position not overlapping the piezoelectric element, the wiring, and the terminal when viewed from a direction vertical to the surface of the substrate, and a protection film that covers at least the piezoelectric element, the wiring, and the inorganic structure includes etching the protection film to form a region in which part of the protection film overlapping the piezoelectric element is removed, and to form an opening in which the protection film overlapping the inorganic structure is removed to expose a part of the inorganic structure.