High-Density Neural Probe Manufacturing via Photolithography and Etching
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Solution Overview
Problem
Current methods for manufacturing neural probes face challenges in producing high-density, small-sized 3D probes with sharp slopes and various heights, as well as difficulties in forming electrodes with narrow gaps and integrating different heights in a single process.
Innovation Solution
A method involving photolithography and etching processes, where a mask with specific patterns is used to pattern a base material, followed by anisotropic and isotropic etching to form trenches and needles with varying shapes and heights, allowing for the creation of neural probes with sharp, long needles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a dicing saw is used to form silicon pillars, then the manufacturing process is simple, but it is difficult to manufacture high-density and small-sized 3D neural probes due to the size and moving width of the dicing saw
Solution Approach 1:
The patent replaces the mechanical dicing saw system with a photolithography-based patterning system. Instead of using a physical saw to cut silicon pillars, the invention uses photomasks and photolithography to define electrode patterns, followed by anisotropic and isotropic etching processes. This substitution enables much finer feature sizes and higher density while maintaining ease of manufacture through standard semiconductor fabrication techniques.
Solution Approach 2:
The patent introduces vertical dimensionality through controlled anisotropic etching that creates trenches at specific angles, followed by isotropic etching that rounds the tips to form needle-like structures. This multi-dimensional approach (combining planar photolithography with vertical etching) enables the formation of sharp, small-sized 3D electrodes that cannot be achieved with conventional planar dicing methods.
2Manufacturing precision
If dry and/or wet etching is used to form arrowhead structures, then 3D electrodes can be manufactured, but the slope and form of the arrowheads cannot be adjusted due to lattice preferred orientation of silicon
Solution Approach 1:
The patent employs a two-stage etching process with different parameters: first, anisotropic etching with controlled depth and angle to create the basic trench structure, then isotropic etching with different chemical parameters to round the tips and form the final needle shape. By adjusting etching depth, time, and chemical composition in each stage, the slope and form of the electrodes can be precisely controlled, overcoming the limitations of single-mode etching and lattice orientation constraints.
3Manufacturing precision
If a diamond blade is used to cut grooves, then electrodes can be formed, but the distance between micro-electrodes is determined by the blade width making it difficult to manufacture narrow-gap patterns
Solution Approach 1:
The patent replaces the mechanical diamond blade cutting system with a photolithography-based patterning system. Instead of physically cutting grooves with a blade of fixed width, the invention uses photomasks with precisely defined pattern dimensions and photolithographic exposure to transfer these patterns onto the substrate. This allows the electrode spacing to be determined by the mask design and exposure process rather than mechanical blade constraints, enabling much narrower gaps and higher electrode density.
4Manufacturing precision
If conventional etching methods are used, then trenches can be formed, but it is difficult to integrate electrodes of different heights in one process
Solution Approach 1:
The patent segments the electrode formation process into distinct stages: first forming all trenches to the same depth through anisotropic etching, then selectively filling or removing material in specific regions through additional photolithography and etching steps. This segmentation allows different electrode heights to be created from a common starting structure, enabling multi-height integration while maintaining a relatively simple base process.
Solution Approach 2:
The patent performs preliminary action by first forming all trenches to a uniform depth before proceeding to height differentiation. This preliminary uniform trench formation establishes a consistent foundation, and subsequent selective material removal or addition creates the desired height variations. This approach simplifies the overall process compared to attempting to form different heights simultaneously.
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 method enables the production of neural probes with sharp, long needles that can effectively penetrate brain tissue, record neural signals, and transmit electrical stimulation, while also simplifying the manufacturing process and ensuring high yield and commercial viability.
Implementation Method 1
patterning the base material coated with the photoresist through a photolithography process using the mask
Implementation Method 2
forming trenches by performing anisotropic etching of the patterned base material
Implementation Method 3
performing isotropic etching of the formed trenches
Data Source
AI summary
Disclosed is a method for manufacturing a high-density neural probe including needles having various forms. The method, in which only a photolithography process and an etching process are used, simplifies a manufacturing process of the neural probe, minimizes changes in the characteristics of the neural probe depending on process equipment or conditions, and may thus ensure a high yield, thereby being advantageous in terms of commercialization. In addition, various forms of needles may be manufactured depending on the shape of patterns included in a mask, the height of the needles may be controlled by adjusting the size of the patterns and the gap between the patterns, and thereby, a neural probe having a plurality of needles having different heights may be manufactured.