Corona Discharge Electretization for MEMS Microphone Substrates
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Solution Overview
Problem
The production of ultra-small condenser microphones using semiconductor process technology faces challenges in efficiently electretizing dielectric films within MEMS microphone chips, leading to damage and low throughput due to the fragile nature of these microphones, which requires complex and costly equipment for handling and positioning.
Innovation Solution
A method involving the use of a semiconductor substrate with a dielectric film and a fixed electrode, where ions from a corona discharge are used to electretize the dielectric film between the electrodes, allowing for simultaneous electretization and charge inspection of multiple microphones on a single substrate without damaging them, using a simple and cost-effective setup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electretization apparatus with needle electrode is used for MEMS microphone chips, then electretization can be performed, but the fragile microphone chips are damaged and throughput is low
Solution Approach 1:
The patent replaces the mechanical needle electrode system with a corona discharge electretization system. Instead of using physical contact or close proximity mechanical electrodes that damage fragile MEMS chips, the invention uses corona discharge from a wire electrode to generate ions that electretize the dielectric film through air discharge, eliminating mechanical damage while maintaining electretization effectiveness
Solution Approach 2:
The patent introduces air as an intermediary medium between the wire electrode and the dielectric film. The corona discharge occurs in the air, generating ions that then interact with the dielectric film. This intermediary air layer prevents direct contact or close mechanical interaction that would damage the fragile MEMS microphone chips while still achieving the desired electretization effect
2Manufacturing precision
If complex handling mechanisms are used to position and hold microphone chips, then precise electretization can be achieved, but equipment cost increases
Solution Approach 1:
The patent changes the positioning approach from precise lateral positioning of individual chips to positioning the entire substrate in a corona discharge field. The wire electrode can electretize multiple chips simultaneously across the substrate area, eliminating the need for complex mechanisms to position and hold each fragile chip individually while maintaining manufacturing precision through substrate-level control
3Productivity
If multiple microphone chips are processed simultaneously, then productivity increases, but damage risk to individual chips increases
Solution Approach 1:
The patent replaces mechanical handling and positioning systems with a corona discharge field-based system. The wire electrode generates ions that can electretize multiple chips simultaneously without requiring physical contact or close mechanical interaction with each chip, thereby increasing productivity while eliminating the damage risk associated with handling multiple fragile chips
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 and cost-effective electretization of multiple ultra-small condenser microphones on a single substrate, enhancing productivity and reducing equipment costs by eliminating the need for complex handling mechanisms and allowing for parallel inspection and processing.
Implementation Method 1
a dielectric film is electretized by causing a corona discharge using a needle electrode
Implementation Method 2
irradiating the dielectric film placed between the fixed electrode and the vibration film with ions resulting from a corona discharge
Implementation Method 3
a potential difference is generated between both electrodes by an electric field occurred by the fixed charges
Data Source
AI summary
In the present invention, a semiconductor substrate wherein a plurality of MEMS microphones is formed is disposed opposed to a discharge electrode in a state of being stuck on a sheet. Electretization of a dielectric film provided in the MEMS microphone is performed by irradiating the dielectric film between a fixed electrode and a vibration film provided in the MEMS microphone with ions resulting from a corona discharge of the discharge electrode in a state that a predetermined potential difference is applied to the fixed electrode and the vibration film and fixing charges based on the ions to the dielectric film. The electretization is successively performed to each MEMS microphone on the semiconductor substrate by relatively moving the semiconductor substrate and the discharge electrode. Therefore, electretization of the dielectric film in the MEMS microphone chip is realized using a low-cost and simple fabricating equipment and productivity can be enhanced.