Piezoelectric Film Patterning via Sacrificial Layer Lift-off
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional techniques for patterning piezoelectric films, such as dry etching and lift-off methods, face challenges in achieving high shape accuracy and uniformity of protruding regions, especially for inorganic materials with micron-thick films, leading to taper shapes and increased processing time and cost.
Innovation Solution
A process involving the formation of a selectively removable resist or sacrifice layer in a predetermined pattern, followed by the growth of a pillar-shaped structure film and subsequent lift-off technique to create protruding regions with side faces normal to the base plate, allowing for precise separation and reduced pattern defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dry etching processing is used to pattern piezoelectric films, then protruding regions can be formed, but the side faces of the protruding regions develop taper shapes, reducing shape accuracy
Solution Approach 1:
A sacrificial layer is deposited beforehand on the base plate before forming the piezoelectric film. This preliminary structure enables subsequent selective removal to create vertically-sided protruding regions, preventing the taper formation that occurs with direct dry etching of the piezoelectric material.
Solution Approach 2:
The sacrificial layer acts as an intermediary element that facilitates the formation of accurately shaped protruding regions. By depositing the piezoelectric film over this intermediary layer and then selectively removing portions of both, vertically-sided structures are achieved without directly etching the piezoelectric material at angled angles.
2Manufacturing precision
If dry etching processing is used on thick piezoelectric films (1-5 μm), then patterning can be achieved, but the processing time increases significantly
Solution Approach 1:
The invention replaces the time-consuming mechanical dry etching process with a deposition-based approach followed by selective removal. Instead of removing material through slow etching, the piezoelectric film is deposited over a sacrificial layer and then patterned by selective removal, which is faster for thick films.
Solution Approach 2:
The sacrificial layer is prepared in advance, allowing the piezoelectric film to be deposited uniformly across the entire surface. The subsequent selective removal process is faster than etching through the full thickness of a 1-5 μm piezoelectric film using dry etching methods.
3Manufacturing precision
If dry etching processing is used for piezoelectric films, then patterning can be performed, but high vacuum processes are required, increasing costs
Solution Approach 1:
The invention substitutes vacuum-based dry etching processes with atmospheric pressure deposition and wet chemical removal processes. The piezoelectric film is deposited using techniques that do not require high vacuum, and the sacrificial layer is removed using chemical etchants that can be applied at atmospheric pressure, thereby reducing manufacturing costs.
Solution Approach 2:
The process changes the operating parameters from vacuum conditions to atmospheric pressure conditions. By using deposition methods and chemical removal processes that operate at atmospheric pressure, the expensive vacuum infrastructure and associated costs are eliminated while maintaining patterning capability.
4Length of moving object
If the piezoelectric film thickness is increased to 1-5 μm to achieve desired strain displacement, then larger displacement quantity is obtained, but the film becomes harder to etch with dry etching
Solution Approach 1:
The sacrificial layer serves as an intermediary that enables the formation of thick piezoelectric structures (1-5 μm) with vertical sidewalls. By depositing the thick piezoelectric film over the sacrificial layer and then selectively removing portions, the etching difficulty of thick materials is circumvented, as the removal process acts on both the sacrificial layer and overlying piezoelectric film simultaneously.
Solution Approach 2:
The sacrificial layer is prepared beforehand to the appropriate thickness and pattern, allowing a thick piezoelectric film (1-5 μm) to be deposited uniformly. The subsequent selective removal process efficiently patterns the thick film without requiring prolonged or complex dry etching, thereby solving the etching difficulty associated with thick piezoelectric materials.
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 ensures high shape accuracy and quick patterning of protruding regions regardless of material or thickness, suppressing pattern loss and maintaining smoothness, while avoiding the need for high-vacuum processes, thus reducing costs.
Implementation Method 1
a piezoelectric device provided with a piezoelectric film, which has piezoelectric characteristics such that the piezoelectric film expands and contracts in accordance with an increase and a decrease in electric field applied across the piezoelectric film
Data Source
AI summary
In a step (A), a selectively removable resist layer or a selectively removable sacrifice layer is formed in a predetermined pattern in a protrusion non-forming region on a base plate. In a step (B), a pillar-shaped structure film is formed on a side of the base plate, on which side the resist layer or the sacrifice layer has been formed in the predetermined pattern. The pillar-shaped structure film contains a plurality of pillar-shaped bodies, each of which extends in a direction nonparallel with a base plate surface of the base plate. In a step (C), the resist layer or the sacrifice layer, and a region of the pillar-shaped structure film, which region is located on the resist layer or the sacrifice layer, are removed by use of a lift-off technique. At least one protruding region, which contains the pillar-shaped bodies, is thus formed.