Single-Substrate IC and MEMS Microphone Integration
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Solution Overview
Problem
Conventional methods for integrating micro-silicon condenser microphones and ICs on a single substrate face challenges, such as pollution of ICs during MEMS component fabrication and the need for high temperatures that can damage metal electrodes, limiting the use of existing standard semiconductor processes.
Innovation Solution
A method involving a SOI substrate with separate areas for IC and microphone fabrication, using standard semiconductor processes to form the IC and then fabricating the micro-silicon condenser microphone with low-temperature deposition and etching techniques, including forming a backplate, sound holes, and a Poly Sil-xGex film as the second electrode plate, while avoiding high-temperature steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high-temperature deposition processes are used to form polycrystalline silicon for the microphone, then the microphone structure can be formed, but the metal electrodes of the IC are damaged
Solution Approach 1:
The patent changes the deposition temperature parameter from conventional high-temperature (above 400°C) to low-temperature (below 400°C) processes. Specifically, it uses PECVD to deposit silicon nitride at 350-380°C and sputtering to deposit aluminum at room temperature or slightly elevated temperatures, thereby forming the microphone structure without damaging the IC metal electrodes.
Solution Approach 2:
The patent replaces the conventional thermal field-based polycrystalline silicon deposition with alternative deposition methods. It uses PECVD (plasma-enhanced chemical vapor deposition) for silicon nitride and sputtering (physical vapor deposition) for aluminum electrodes, substituting the high-temperature thermal process with plasma and physical deposition processes that operate at lower temperatures.
2Productivity
If standard semiconductor processes are used for IC fabrication, then IC can be manufactured, but subsequent high-temperature MEMS fabrication is required which damages the IC
Solution Approach 1:
The patent inverts the conventional sequence by fabricating the MEMS microphone structure first on the substrate, then fabricating the IC on the same substrate. This reversal allows the IC to be protected from high-temperature processes, as the MEMS structure is already in place and the IC fabrication occurs at lower temperatures compatible with the existing MEMS components.
Solution Approach 2:
The patent segments the fabrication process into distinct low-temperature stages: first forming the MEMS microphone structure using PECVD and sputtering, then fabricating the IC using standard semiconductor processes. This segmentation allows each component to be optimized independently while maintaining compatibility on the same substrate.
3Reliability
If single substrate integration is used, then noise influence is reduced and integral capability is improved, but fabrication complexity increases due to process constraints
Solution Approach 1:
The patent changes the temperature parameters of the fabrication process to enable single-substrate integration. By using low-temperature PECVD and sputtering processes, it achieves single-substrate integration of IC and MEMS microphone without the temperature conflicts that would otherwise require multi-substrate approaches, thereby maintaining noise immunity while simplifying the overall integration architecture.
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 allows for the integration of high-sensitive micro-silicon condenser microphones with ICs on a single substrate, reducing equipment investment and improving component performance by avoiding pollution and temperature-related issues, while maintaining compatibility with existing semiconductor processes.
Implementation Method 1
depositing a sacrificial layer above the SOI base via a low-temperature deposition process
Implementation Method 2
forming a Poly Sil-xGex film on the sacrificial layer
Implementation Method 3
eroding the sacrificial layer from the sound holes to form a chamber
Data Source
AI summary
A method for integrating an IC and a MEMS component includes the following steps: S1) providing a SOI base (20) having a first area (21) and a second area (22); S2) fabricating an IC on the first area through a standard semiconductor process, and simultaneously forming a metal conductive layer (26) and a medium insulation layer (25c) extending to the second area; S3) partly removing the medium insulation layer and then further partly removing the silicon component layer so as to form a backplate diagram; S4) depositing a sacrificial layer (32) above the SOI base; S5) forming a Poly Sil-xGex film (33) on the sacrificial layer; S6) forming a back cavity (34); and S7) eroding the sacrificial layer to form a chamber (36) in communication with the back cavity. Besides, a chip (10) fabricated by the above method is also disclosed.