Liquid Ejection Head Substrate Manufacturing with Protective Coating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing liquid ejection head substrates face challenges in efficiently heating liquids while maintaining the integrity of the heat-generating resistor layer, as thin insulating and protective layers struggle to protect height differences caused by electrodes, leading to insulation and durability issues, and surface alterations during the production process can result in premature failure.
Innovation Solution
A method for manufacturing a liquid ejection head substrate involves stacking a heat storage layer, electrodes, a heat-generating resistor layer, and cover layers, with precise etching and ashing techniques to maintain the surface integrity of the heat-generating resistor layer, using materials like SiN, SiO, and TaSiN, and employing chemical mechanical polishing to ensure flat surfaces and adequate layer thicknesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the insulating layer and protective layer are made thin to enable efficient liquid heating, then heating efficiency is improved, but the height difference portion generated by the pair of electrodes cannot be protected sufficiently, causing insulation and durability issues
Solution Approach 1:
The patent introduces a third layer (protective layer) above the insulating layer to create a multi-layer structure. This additional dimension allows the protective layer to cover the height difference portion generated by the electrodes, providing sufficient protection while maintaining thin insulating and protective layers for efficient heating.
Solution Approach 2:
The patent divides the protective function into two separate layers: an insulating layer for electrical insulation and a protective layer for mechanical protection against cavitation. This segmentation allows each layer to be optimized for its specific function while maintaining overall thinness for heating efficiency.
2Loss of substance
If dry ashing is performed to completely remove the photoresist, then the photoresist is fully removed, but the surface of the heat-generating resistor layer is exposed to oxygen plasma, causing oxidation and alteration that increases resistance value and degrades durability
Solution Approach 1:
The patent applies a protective coating on the heat-generating resistor layer before the dry ashing process. This preliminary protective layer prevents oxygen plasma from oxidizing and altering the resistor surface during photoresist removal, thereby maintaining resistance stability and durability while still achieving complete photoresist removal.
3Manufacturing precision
If the heat-generating resistor layer is made thin to increase resistance value, then resistance value is improved, but even several nanometers of surface alteration has a profound effect, causing early failure
Solution Approach 1:
The patent applies a protective coating before the etching and ashing processes to cushion and protect the thin heat-generating resistor layer from surface alteration. This beforehand protection prevents oxidation and damage during manufacturing, ensuring that even several nanometers-thick resistors maintain their integrity and durability while achieving the desired resistance value.
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 approach enables efficient liquid heating while suppressing surface alterations, enhancing the durability and insulation of the heat-generating resistor layer, thereby preventing early failure and maintaining consistent resistance values.
Implementation Method 1
heating a liquid rapidly with a heat-generating resistor disposed in a liquid ejection head substrate so as to generate bubbles
Implementation Method 2
the surface of the photoresist is altered and the photoresist is not removed completely by only being dipped into an chemical solution configured to dissolve the photoresist. Therefore, the photoresist is removed by performing dry ashing using oxygen plasma
Implementation Method 3
the surface of the heat-generating resistor layer is exposed to the oxygen plasma, the surface is oxidized, a portion having a thickness of several nanometers from the surface of the heat-generating resistor layer is altered, and the resistance value of that portion increases
Data Source
AI summary
A method for manufacturing a liquid ejection head substrate, in which a heat storage layer, a pair of electrodes extending from the surface of the heat storage layer toward the back surface, a heat-generating resistor layer in contact with the pair of electrodes and the surface of the heat storage layer, and a first cover layer configured to cover the heat-generating resistor layer are stacked, includes the steps of etching the heat-generating resistor layer and the first cover layer by using a mask disposed on a substrate including the heat-generating resistor layer and the first cover layer, removing the mask, and forming a second cover layer configured to cover an end portion of the heat-generating resistor layer in that order.