Hydrophilic Sidewall Etching for Inkjet Printhead Trenches
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Solution Overview
Problem
Current etching methods for deep or ultradeep trenches in silicon substrates, such as the Bosch process, struggle to maintain anisotropy and result in hydrophobic sidewalls, which are undesirable for inkjet printhead applications, and require complex gas plasma alternation and post-etching treatments that can lead to uneven sidewalls and additional fabrication steps.
Innovation Solution
A deep reactive ion etching method using a passivating gas plasma with a hydrophilizing dopant, which simultaneously etches and passivates the substrate, achieving anisotropic etching with hydrophilic sidewalls without the need for post-etch treatments, allowing for trenches or channels with depths over 100 microns and contact angles less than 50°.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional etching methods (e.g., Bosch process) are used for deep or ultradeep trenches, then etching depth can be achieved, but anisotropy is not maintained and sidewalls become hydrophobic
Solution Approach 1:
The patent modifies the gas plasma parameters by introducing a hydrophilizing dopant into the passivating gas plasma composition. This changes the chemical properties of the plasma to simultaneously achieve anisotropic etching and hydrophilic sidewall formation, resolving the contradiction between etching depth and anisotropy maintenance.
2Manufacturing precision
If complex gas plasma alternation is used to maintain anisotropy, then etching precision improves, but process complexity and post-etch treatments increase
Solution Approach 1:
The patent combines the passivation function and hydrophilizing function into a single gas plasma step by incorporating the hydrophilizing dopant into the passivating gas plasma. This eliminates the need for alternating gas plasma cycles and subsequent post-etch cleanup steps, reducing process complexity while maintaining etching precision.
3Manufacturing precision
If post-etch treatments are applied to clean sidewalls, then sidewall quality improves, but additional fabrication steps and time are required
Solution Approach 1:
The patent performs the hydrophilizing action during the etching process itself by incorporating the dopant into the passivating gas plasma. This preliminary action eliminates the need for subsequent post-etch cleanup steps, improving fabrication efficiency while maintaining sidewall quality.
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 method provides highly anisotropic etching with perpendicular sidewalls and hydrophilic surfaces, eliminating the need for post-etch cleanup steps and achieving high etch rates, suitable for forming ink supply channels in inkjet printheads with depths over 100 microns and maintaining hydrophilicity.
Implementation Method 1
A deep reactive ion etching method using a passivating gas plasma with a hydrophilizing dopant, which simultaneously etches and passivates the substrate
Implementation Method 2
deep reactive ion etching a trench into a substrate, said method comprising an etching process using an etching gas plasma and passivation process using a passivating gas plasma
Implementation Method 3
said passivating gas plasma comprises a hydrophilizing dopant... achieving anisotropic etching with hydrophilic sidewalls... sidewalls having contact angles less than 50°
Data Source
AI summary
A method suitable for etching hydrophilic trenches into a substrate, such as silicon, is provided. The method comprises etching and sidewall passivation processes for achieving anisotropy. Sidewalls of the etched trench are made hydrophilic during the etch by virtue of a hydrophilizing dopant in a passivating gas plasma. The method is useful for etching ink supply channels in inkjet printheads.