CMOS Sidewall Microelectrodes for Miniaturized Neural Implants
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Solution Overview
Problem
The miniaturization of implantable medical devices (IMDs) for neural interfaces is hindered by the need for off-chip components, which increases the device's volume and compromises its reliability due to complex assembly and excessive connections.
Innovation Solution
The method involves fabricating microelectrodes on the sidewalls of a CMOS chip using atomic layer deposition (ALD) and plasma-focused ion beam (FIB) milling, eliminating the need for off-chip components and enabling a fully integrated, single-package solution for wireless, battery-free neural interfacing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If off-chip components are used in IMD assembly, then the device can be manufactured using conventional techniques, but the overall device volume increases and reliability decreases due to excessive connections
Solution Approach 1:
The patent merges previously separate off-chip components (electrodes, coils, capacitors, resistors) directly onto the CMOS chip substrate, eliminating the need for separate packaging and reducing the number of interconnect interfaces. This integration approach maintains ease of manufacture through standardized semiconductor fabrication processes while significantly reducing overall device volume.
Solution Approach 2:
The patent utilizes three-dimensional integration techniques, including vertical stacking of components and sidewall electrode configurations, to pack more functionality into a smaller footprint. By transitioning from planar to volumetric integration, the device achieves compact form factor without sacrificing manufacturability through advanced CMOS fabrication processes.
2Ease of manufacture
If off-chip components are used in IMD assembly, then the device can be manufactured using conventional techniques, but reliability decreases due to excessive interfaces and connections
Solution Approach 1:
By integrating electrodes, coils, and passive components directly onto the CMOS chip, the patent eliminates multiple wire bonds, flip-chip connections, and packaging interfaces that are prone to failure. The merged structure reduces the number of potential failure points while maintaining compatibility with conventional semiconductor manufacturing processes.
Solution Approach 2:
The patent employs standard CMOS fabrication materials and processes that are inherently reliable and well-characterized, replacing fragile wire bonds and complex interconnect structures with robust integrated circuit interconnections that are part of the monolithic chip structure.
3Ease of manufacture
If microelectrodes are mounted onto the top surface of an ASIC, then the device can be assembled, but the surface area of the top surface increases substantially, leading to a larger IMD
Solution Approach 1:
The patent transitions from planar electrode mounting on the top surface to three-dimensional electrode configurations, including sidewall electrodes that extend vertically from the chip edges and bottom electrodes that contact the substrate from underneath. This dimensional transition enables electrode integration without increasing the chip's top surface footprint.
Solution Approach 2:
The patent nests electrodes within the three-dimensional structure of the chip package, with electrodes embedded in sidewalls and bottom surfaces rather than protruding from the top surface. This nested configuration allows multiple electrodes to be accommodated within the chip's volumetric space without increasing the planar footprint.
4Ease of manufacture
If conventional assembly techniques are used to incorporate electrodes onto the ASIC, then the device can be assembled, but the process becomes complex and time-consuming
Solution Approach 1:
The patent incorporates electrode formation into the CMOS fabrication process itself, with electrodes being deposited, patterned, and integrated during the standard semiconductor manufacturing sequence. This preliminary integration eliminates subsequent assembly steps for mounting electrodes, reducing both process complexity and total manufacturing time.
Solution Approach 2:
The patent merges electrode fabrication with CMOS circuit fabrication into a single integrated manufacturing process flow, eliminating the need for separate assembly operations. Both the electrodes and the CMOS circuits are formed simultaneously using the same fabrication equipment and process techniques, dramatically reducing assembly time and 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 reduces the overall size of the IMD, enhances its reliability, and provides a more efficient and compact solution for neural interfacing, allowing for the potential implantation of multiple devices at different brain locations.
Implementation Method 1
By employing atomic layer deposition (ALD) and plasma-focused ion beam (FIB) milling
Implementation Method 2
By employing atomic layer deposition (ALD) and plasma-focused ion beam (FIB) milling
Data Source
AI summary
A fabrication technique for a miniaturized implantable medical device is described. The technique includes fabricating microelectrodes on the sidewalls of a complimentary metal-oxide-semiconductor (CMOS) chip. By employing atomic layer deposition (ALD) and plasma-focused ion beam (FIB) milling, the technique eliminates the necessity for off-chip components, thereby reducing the device's overall size and enhancing its reliability. This novel approach provides a fully integrated, single-package solution for wireless, battery-free neural interfacing, offering advantages over traditional methods that rely on complex packaging, assembly and external components.