Stacked MEMS-CMOS Structure With Bonded Movable Membrane
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Solution Overview
Problem
The integration of MEMS and CMOS devices in stacked semiconductor structures is challenging due to fabrication technology incompatibilities, leading to difficulties in manufacturing devices with multiple functions.
Innovation Solution
A method for forming a stacked semiconductor structure that includes a MEMS device and a CMOS device, involving specific fabrication steps such as cleaning, depositing, patterning, etching, and doping, to create a movable structure with a flexible top electrode and a CMOS device with interconnects, followed by bonding and thinning processes to integrate the two devices, ensuring electrical connectivity and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If MEMS and CMOS devices are integrated in stacked semiconductor structures, then device functionality and performance are improved, but fabrication complexity and manufacturing difficulty increase due to technology incompatibilities
Solution Approach 1:
The patent divides the integrated device into separate MEMS and CMOS sections that are fabricated independently on different substrates using their respective optimized processes. The MEMS section is fabricated on a first substrate using MEMS-specific processes, while the CMOS section is fabricated on a second substrate using standard CMOS processes. These separate sections are then bonded together to form the stacked structure, allowing each section to be optimized for its specific fabrication requirements while achieving integrated functionality.
Solution Approach 2:
The patent introduces intermediary bonding interfaces and connection structures that facilitate the integration of MEMS and CMOS sections. These intermediary elements include bonding pads, interconnect structures, and interface layers that enable electrical and mechanical coupling between the two different technology sections, bridging the fabrication process incompatibilities.
2Reliability
If multiple fabrication processes are used for MEMS and CMOS devices, then device performance is optimized, but manufacturing precision and integration reliability deteriorate
Solution Approach 1:
By segmenting the device into separately fabricated MEMS and CMOS sections, the patent allows each section to be manufactured with high precision using its optimized process without compromising the other section's precision requirements.
Solution Approach 2:
The patent performs preliminary fabrication of MEMS and CMOS sections on separate substrates before final integration, allowing each section to be fully processed and tested independently. This preliminary action ensures that each section meets its performance specifications before being combined, reducing integration risks.
3Ease of manufacture
If MEMS and CMOS devices are stacked together, then assembly costs are reduced and electrical parasitics are minimized, but mechanical integrity and electrical connectivity become more difficult to ensure
Solution Approach 1:
The stacked structure is divided into discrete MEMS and CMOS sections bonded at defined interfaces, allowing for modular assembly that reduces overall complexity and cost while maintaining mechanical strength through dedicated bonding structures.
Solution Approach 2:
The patent employs composite bonding structures that combine different materials and bonding techniques to achieve both mechanical integrity and electrical connectivity. The bonding interfaces use material combinations that provide both structural strength and electrical connection, ensuring reliable integration of the stacked sections.
Data Source
AI summary
A stacked semiconductor structure includes a first substrate. A multilayer interconnect is disposed over the first substrate. Metal sections are disposed over the multilayer interconnect. First bonding features are over the metal sections. A second substrate has a front surface. A cavity extends from the front surface into a depth D in the second substrate. A movable structure is disposed over the front surface of the second substrate and suspending over the cavity. The movable structure includes a dielectric membrane, metal units over the dielectric membrane and a cap dielectric layer over the metal units. Second bonding features are over the cap dielectric layer and bonded to the first bonding features. The second bonding features extend through the cap dielectric layer and electrically coupled to the metal units.