Plasma Etching Piezoelectric Material for High Aspect Ratio Features
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Solution Overview
Problem
Existing methods for shaping piezoelectric materials in ink jet printheads are limited by the need for mechanical sawing, which restricts the geometry and packing density of actuators, and often require high temperatures that can depole the material, making it difficult to create deep features with high aspect ratios and irregular shapes.
Innovation Solution
The method involves plasma etching of piezoelectric materials like PZT under controlled conditions, using a masking material with high selectivity and etchability, to form features with depths of 5 microns or more and aspect ratios of 2 or greater, while maintaining the material below its Curie temperature to prevent depoling, allowing for rapid etching and precise shaping into non-rectangular geometries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mechanical sawing is used to shape piezoelectric material, then the material can be cut into basic geometric forms, but the geometry is restricted to simple shapes and packing density is limited
Solution Approach 1:
The patent replaces mechanical sawing with plasma etching to shape piezoelectric material. This substitution enables complex geometries including curved surfaces, non-planar features, and irregular shapes that cannot be achieved with mechanical cutting, while maintaining manufacturing capability through a controllable chemical process
Solution Approach 2:
The patent changes the fundamental parameter of material removal from mechanical cutting to chemical etching. By controlling plasma etching parameters such as power, gas flow, and etch chemistry, the process achieves both manufacturing efficiency and geometric versatility, creating features with aspect ratios exceeding 10:1 and complex three-dimensional shapes
2Productivity
If high temperature processing is used to shape piezoelectric material, then etching can proceed, but the material depoles and loses its piezoelectric properties
Solution Approach 1:
The patent changes the temperature parameter from high-temperature processing to low-temperature plasma etching (below Curie temperature). This parameter change maintains high productivity through efficient plasma chemistry while preserving piezoelectric properties by avoiding thermal depoling, achieving both fast etching rates and material property retention
Solution Approach 2:
The patent replaces thermal etching mechanisms with plasma-based chemical etching. This substitution eliminates the need for high temperatures by using reactive plasma species to remove material chemically, thereby maintaining etching productivity while preventing thermal damage and depoling of the piezoelectric material
3Manufacturing precision
If deep features are etched in piezoelectric material, then high aspect ratio structures are achieved, but the etching process becomes more difficult and time-consuming
Solution Approach 1:
The patent replaces mechanical drilling or sequential machining with plasma etching to create deep features. The plasma process achieves high aspect ratio structures (exceeding 10:1) in a single step with uniform etch rates, simplifying the overall manufacturing process while achieving superior geometric precision that would be extremely complex to obtain through mechanical means
Solution Approach 2:
The patent applies preliminary patterning with photoresist and hard mask layers before plasma etching. This preliminary action defines the exact feature geometry and protects surrounding areas, enabling precise deep feature creation with complex shapes while maintaining process simplicity through a standardized multi-layer patterning approach
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 the creation of piezoelectric actuators with deep, high-aspect-ratio features and irregular shapes, allowing for more densely packed and efficient ink jet printheads with improved resolution and integration into MEMS devices, while maintaining the material's polarity and reducing processing costs.
Implementation Method 1
shaping a piezoelectric material, e.g. PZT, by exposing the material to plasma etching conditions and etching a feature having a depth of about 1 micron or more
Implementation Method 2
A piezoelectric actuator has a layer of piezoelectric material, which changes geometry, or bends, in response to an applied voltage. The bending of the piezoelectric layer pressurizes ink in a pumping chamber located along the ink path
Data Source
AI summary
Piezoelectric material is shaped by plasma etching to form deep features with high aspect ratios, and desired geometries.