MEMS-CMOS Integration via Low-Temperature Bonding
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Solution Overview
Problem
Cavity first fabrication processes for MEMS devices face challenges in creating malleable mechanical structures due to sticking issues during wet cleaning and potential damage to CMOS devices from high-temperature bonding, especially as CMOS device sizes shrink.
Innovation Solution
A method involving forming cavities within a carrier substrate, bonding it to a MEMS substrate with a dielectric layer, patterning the MEMS substrate to create soft mechanical structures, and using a dry etching process to release them, followed by a low-temperature bonding process to attach the MEMS substrate to a CMOS substrate via a bonding structure, avoiding high-temperature damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wet cleaning is used in cavity first fabrication, then cleaning effectiveness is improved, but mechanical structures stick to cavity surfaces
Solution Approach 1:
The patent introduces an intermediary substance (release agent or coating) between the mechanical structures and cavity surfaces to prevent direct adhesion during wet cleaning, allowing effective cleaning without sticking
Solution Approach 2:
The patent extracts the cleaning process from the cavity-first sequence and performs cleaning after structure formation, eliminating the sticking problem while maintaining cleaning effectiveness
2Strength
If high-temperature bonding is used to attach MEMS to CMOS substrates, then bonding strength is improved, but CMOS devices are damaged
Solution Approach 1:
The patent changes the temperature parameter from high-temperature bonding to low-temperature bonding by modifying bonding layer materials and processes, achieving adequate bonding strength without damaging CMOS devices
Solution Approach 2:
The patent uses composite bonding structures with multiple layers having different material properties, where intermediate layers enable bonding at lower temperatures while maintaining overall bond strength
3Ease of manufacture
If cavity first fabrication is used, then manufacturing process is simplified, but mechanical structures cannot be made malleable
Solution Approach 1:
The patent inverts the traditional cavity-first sequence to structure-first fabrication, where mechanical structures are formed before creating cavities, enabling malleable structures while maintaining reasonable process complexity
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 successful formation of MEMS devices with malleable structures that operate freely while minimizing damage to CMOS devices, overcoming the limitations of traditional cavity first fabrication processes.
Implementation Method 1
the bonding structure abuts a second side of the MEMS substrate and is electrically connected to a metal interconnect layer
Implementation Method 2
using a dry etching process to release them
Data Source
AI summary
The present disclosure relates an integrated chip having one or more MEMS devices. In some embodiments, the integrated chip has a carrier substrate with one or more cavities disposed within a first side of the carrier substrate. A dielectric layer is disposed between the first side of the carrier substrate and a first side of a micro-electromechanical system (MEMS) substrate. The dielectric layer has sidewalls that are laterally set back from sidewalls of openings extending through the MEMs substrate to the one or more cavities. A bonding structure, including an intermetallic compound having a plurality of metallic elements, abuts a second side of the MEMS substrate and is electrically connected to a metal interconnect layer within a dielectric structure disposed over a CMOS substrate.