Capacitive Micromachined Ultrasonic Transducer Adhesion Layer
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Solution Overview
Problem
Current methods for manufacturing capacitive micromachined ultrasonic transducers face challenges in achieving high precision and reducing manufacturing costs while ensuring structural integrity and preventing delamination during the wet etching process.
Innovation Solution
A method involving the deposition of a first metal layer on a substrate, followed by photoresist application and exposure to electromagnetic radiation, wet etching to form cavities, and subsequent deposition of a second metal layer, which includes using chromium or platinum for improved adhesion and structural integrity, and forming a membrane for precise sound transducer fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional semiconductor processes are used to fabricate cMUTs, then integration with ancillary transducer circuitry is achieved, but manufacturing precision and structural integrity during wet etching are compromised
Solution Approach 1:
The patent applies preliminary action by depositing the first metal layer (adhesion layer) onto the substrate before applying the photoresist layer. This adhesion layer is specifically designed to prevent delamination during subsequent wet etching processes, thereby ensuring manufacturing precision is maintained while still allowing integration with circuitry through conventional semiconductor processes.
Solution Approach 2:
The patent introduces an intermediary element - the first metal adhesion layer - that mediates between the substrate and the photoresist layer. This intermediary layer prevents direct contact between the photoresist and substrate, thereby preventing delamination during wet etching while still allowing the photoresist to function properly for patterning, enabling both precision and circuit integration.
2Device complexity
If photoresist is applied directly to the substrate, then manufacturing steps are reduced, but delamination occurs during wet etching
Solution Approach 1:
The first metal layer serves as an intermediary between the substrate and photoresist, preventing direct adhesion that would cause delamination during wet etching. This intermediary layer maintains structural integrity and reliability while adding only one additional manufacturing step, which is justified by the prevention of defective transducers.
Solution Approach 2:
The adhesion layer is deposited in advance before photoresist application, preliminarily establishing the structural foundation needed to prevent delamination during subsequent wet etching. This preliminary action ensures reliability is maintained without significantly increasing device complexity.
3Reliability
If chromium or platinum is used as the first metal layer, then adhesion and structural integrity are improved, but manufacturing cost increases
Solution Approach 1:
The patent applies parameter changes by allowing selection of different materials for the first metal layer based on specific application requirements. While chromium or platinum provide superior adhesion and structural integrity, the patent structure enables cost-optimized alternatives to be used when extreme reliability is not required, thereby balancing reliability improvements with manufacturing cost considerations.
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 allows for the precise manufacturing of capacitive micromachined sound transducers with improved accuracy and reduced costs, enabling the production of high-quality transducers capable of emitting and sensing ultrasonic waves with enhanced structural integrity.
Implementation Method 1
exposing portions of the photo resist layer to electromagnetic radiation
Implementation Method 2
wet etching portions of the substrate above which the first metal layer has been removed
Data Source
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AI summary
Provided is a process for manufacturing a sound transducer. The process comprises depositing a first metal layer onto a substrate, applying a photo resist layer to the first metal layer, exposing portions of the photo resist layer to electromagnetic radiation, developing the photo resist layer, removing portions of the first metal layer, wet etching portions of the substrate above which the first metal layer has been removed, and depositing a second metal layer onto the substrate.