Monolithically Integrated MEMS Microphone with CMOS Substrate
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional Electret Condenser Microphones (ECMs) have large form factors, are costly, and difficult to manufacture efficiently, while silicon microphones, although smaller and more efficient, still face challenges in manufacturing due to their MEMS fabrication processes.
Innovation Solution
The integration of a MEMS structure on a CMOS substrate using IC-foundry compatible processes, with a diaphragm having a stress relief corrugated structure, air vent holes, and encapsulation by a thick insulating layer, enables the creation of a microphone device with improved size, temperature, and humidity performance, and reduced manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional Electret Condenser Microphones (ECMs) are used, then they provide reliable microphone function, but they have large form factors and are costly to manufacture
Solution Approach 1:
The patent combines the MEMS microphone structure with CMOS integrated circuit substrate to create a monolithically integrated device. The microphone diaphragm, air vent holes, and CMOS processing are all integrated on a single substrate, eliminating the need for separate manufacturing steps and assembly processes. This merging of structures achieves both size reduction and manufacturing efficiency improvement.
Solution Approach 2:
The CMOS substrate serves multiple functions: it provides the mechanical support structure for the MEMS microphone, acts as the processing substrate for integrated circuit fabrication, and enables surface mountability. This multi-functionality allows the same substrate to fulfill both acoustic and electronic requirements, reducing overall device complexity and manufacturing cost.
2Ease of manufacture
If silicon microphones are used, then they reduce size and improve temperature performance, but they remain difficult to manufacture efficiently due to MEMS fabrication processes
Solution Approach 1:
The patent changes the fabrication approach from traditional MEMS processes to IC-foundry compatible CMOS processes. This parameter change in manufacturing methodology enables the use of standard semiconductor fabrication techniques that are highly optimized, reliable, and scalable, thereby improving manufacturing efficiency while maintaining the temperature and humidity performance benefits of silicon-based structures.
3Ease of operation
If ECMs are hand soldered to overcome temperature limitations, then they can be assembled, but manufacturing costs and inefficiencies increase significantly
Solution Approach 1:
The patent merges the microphone structure with the CMOS substrate to create a monolithically integrated device that can be surface mounted using conventional pick and place methods. This integration eliminates the need for hand soldering by combining all microphone components onto a single substrate that can be assembled using automated surface mount technology, thereby improving both assembly ease and manufacturing productivity.
Data Source
AI summary
A monolithically integrated MEMS and CMOS substrates provided by an IC-foundry compatible process. The CMOS substrate is completed first using standard IC processes. A diaphragm with stress relief corrugated structure is then fabricated on top of the CMOS. Air vent holes are then etched in the CMOS substrate. Finally, the microphone device is encapsulated by a thick insulating layer at the wafer level. The monolithically integrated microphone that adopts IC foundry-compatible processes yields the highest performance, smallest form factor, and lowest cost. Using this architecture and fabrication flow, it is feasible and cost-effective to make an array of Silicon microphones for noise cancellation, beam forming, better directionality and fidelity.