Wafer-Level Electretization for Ultra-Small Condenser Microphones
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Solution Overview
Problem
The assembly process of ultra-small condenser microphones using semiconductor technology is complex and costly due to the fragility of the MEMS microphone chips, requiring precise positioning and stress control, which complicates equipment and reduces productivity.
Innovation Solution
The method involves forming multiple ultra-small condenser microphones on a substrate, electretizing and inspecting the dielectric films in a wafer state before dicing, allowing for successive processing and reducing the need for transferring fragile chips, thereby simplifying equipment and enhancing productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If individual MEMS microphone chips are transferred and processed separately through multiple assembly steps, then precise positioning and stress control can be achieved, but equipment complexity increases and productivity decreases
Solution Approach 1:
The patent merges multiple separate processing steps (electretization, inspection, annealing) into a single integrated wafer-level processing system. The wafer is processed as one unit through all steps without dicing into individual chips, combining what were previously separate operations into a unified flow that reduces equipment complexity while maintaining precision through wafer-level control mechanisms
2Reliability
If individual MEMS microphone chips are transferred and handled multiple times during assembly, then inspection and processing can be performed, but productivity decreases due to complex transfer mechanisms
Solution Approach 1:
The patent implements continuous wafer-level processing where the wafer moves through electretization, inspection, and annealing steps without interruption or separation into individual chips. This continuous flow eliminates the need for repeated transfer and handling operations, maintaining inspection reliability through integrated sensing while dramatically improving productivity by keeping the workpiece in continuous motion through all processing stages
3Productivity
If wafer-level processing is used without dicing into individual chips, then productivity increases and equipment simplifies, but precise positioning and stress control become more difficult
Solution Approach 1:
The patent changes the scale parameter from chip-level to wafer-level processing, treating the entire wafer as the processing unit. This parameter change allows integrated stress control mechanisms to act uniformly across all chips simultaneously, achieving precise stress management through wafer-level uniformity while maintaining high productivity through elimination of individual chip handling
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 reduces equipment costs and increases productivity by minimizing the number of transfers and processing steps for fragile chips, improving the efficiency of the assembly process for ultra-small condenser microphones.
Implementation Method 1
a dielectric film is electretized by applying a corona discharge at least a time to a single or several MEMS microphone chips simultaneously by a needle electrode or a wire electrode
Implementation Method 2
in an UV irradiation/pick-up step S105, adhesion of the adhesive sheet is reduced through UV (ultraviolet) light irradiation
Implementation Method 3
The individual MEMS microphone chip classified as the non-defective is heat-treated in a state that the chip is placed on the metal tray in an annealing step S107
Data Source
AI summary
In the present invention, a plurality of condenser microphones is formed on a substrate. Then, charges are fixed to a dielectric film provided in each of the condenser microphones. After an amount of deposited charges of the dielectric film of each of the plurality of the condenser microphones is inspected by measuring capacitance of each condenser microphone while applying bias between the first electrode film thereof and the second electrode film thereof, the substrate is diced so that each of the condenser microphones is separated. Thus, at least the step of fixing charges is performed in a substrate state where the plurality of the condenser microphones is formed on the substrate. Therefore, the present invention contributes to enhancement of productivity in an assembly process of the condenser microphone and reduction in equipment costs.