Substrate Through-Hole Etching Notching Control
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Solution Overview
Problem
The existing substrate processing methods using reactive ion etching often result in notching, where the through-hole opening is enlarged undesirably due to electric charging, especially when forming small openings, which can compromise the reliability of liquid ejection heads.
Innovation Solution
A substrate processing method is developed where a first layer with a higher etching rate is disposed on the first surface and a second layer with a lower etching rate covers it, allowing reactive ion etching to form a through-hole while suppressing notching by controlling the etching process effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the etching-stop layer is removed after etching reaches it, then the through-hole is completed, but the notching effect has already enlarged the opening
Solution Approach 1:
The patent segments the etching process into multiple cycles where protective film formation and etching are alternated. In each cycle, the protective film is formed, then etching is performed to advance the hole depth. This segmentation ensures that the opening size is controlled throughout the entire etching process, preventing notching-induced enlargement even as productivity is maintained through efficient cycling.
Solution Approach 2:
The patent maintains continuity of useful action by efficiently alternating between protective film formation and etching steps. The process continues in cycles until the through-hole is completed, ensuring that the opening size remains controlled throughout the entire duration of the etching process while maintaining high productivity through continuous progress.
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
This method effectively suppresses the enlargement of the through-hole opening, maintaining the desired size and enhancing the reliability of liquid ejection heads by managing the etching process and preventing horizontal extension of the opening.
Implementation Method 1
performing reactive ion etching on the substrate from the second surface to form a through-hole extending through the substrate from the first surface to the second surface
Implementation Method 2
a phenomenon called 'notching' may occur when reactive ion etching reaches the etching-stop layer. The term 'notching' refers a phenomenon in which a through-hole is enlarged in a direction perpendicular to the direction in which the through-hole is to be formed due to the effect of electric charging
Data Source
AI summary
A substrate processing method for forming a through-hole in a substrate by reactive ion etching includes preparing a substrate that has a first surface and a second surface and on the first surface side of which a first layer and a second layer are disposed, the second surface being on the opposite side to the first surface, the second layer covering the first layer; and performing reactive ion etching on the substrate from the second surface to form a through-hole extending through the substrate from the first surface to the second surface, the reactive ion etching being performed to reach the first layer. The etching rate of the second layer for the reactive ion etching is lower than that of the first layer.