Nanostructured Optical Filter CMOS Multispectral Sensor
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Solution Overview
Problem
Current semiconductor manufacturing processes, such as CMOS, are unable to efficiently produce optical bandpass filters with small filter bandwidths and high transmission, limiting the production of multispectral sensors and spectrometers, as existing filters are either limited to three channels or require additional metal layers that reduce transmission.
Innovation Solution
An optical filter with nanostructured layers, featuring intersecting transmission gratings and a polariser, is manufactured using standard CMOS processes, allowing for the creation of multiple filters with different spectral characteristics on a single chip without modifying the layer structure, by varying the grating wire width, period, and angle, and using the Kerr or Faraday effect for precise polarisation adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dielectric thin film filter systems with more than 50 layers are used, then high transmission and small filter bandwidth are achieved, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The patent changes the fundamental parameters of filter fabrication by transitioning from dielectric thin film deposition to semiconductor semiconductor manufacturing processes. This enables the use of standard CMOS fabrication techniques to create optical filters with nanostructured metal layers, reducing the number of manufacturing steps while maintaining spectral filtering performance
Solution Approach 2:
The patent replaces the mechanical/physical deposition process of dielectric thin films with semiconductor manufacturing processes. By using standard CMOS fabrication techniques, the patent eliminates the need for complex multi-layer dielectric deposition while achieving comparable or superior filter performance
2Ease of manufacture
If standard semiconductor manufacturing processes are used, then manufacturing simplicity is improved, but the ability to produce filters with small bandwidth and high transmission deteriorates
Solution Approach 1:
The patent makes standard semiconductor manufacturing processes universal by demonstrating that they can produce both conventional electronic components and optical filters with precise spectral characteristics. The same CMOS fabrication process creates both the photodetector array and the optical filters, eliminating the need for separate filter manufacturing steps
Solution Approach 2:
The patent changes the material parameters and structural configurations within standard semiconductor processes to enable optical filtering functionality. By carefully selecting metal layer compositions, thicknesses, and nanostructure geometries, the patent achieves precise spectral filtering using conventional semiconductor fabrication
3Measurement precision
If additional metal layers are added to create nanostructured filters, then filter performance is improved, but transmission decreases
Solution Approach 1:
The patent applies local quality by creating nanostructured metal layers with spatially varying properties. The metal layers are patterned with sub-wavelength structures that locally enhance or suppress specific wavelengths, allowing precise spectral filtering without requiring additional bulk metal layers that would uniformly block light
Solution Approach 2:
The patent embeds nanostructures within the existing metal layers of the semiconductor process. By patterning metal layers with sub-wavelength features during standard fabrication, the patent creates nested structures where the nanostructures provide filtering functionality without adding separate metal layer thickness
4Ease of manufacture
If CFA pigment filters are used, then manufacturing simplicity is improved, but the number of spectral channels is limited to three
Solution Approach 1:
The patent changes the spectral filtering mechanism from pigment-based absorption to nanostructure-based resonant scattering. By varying the dimensions, shape, and material composition of nanostructured metal layers, the patent can design filters for any desired spectral channel, not just the three primary colors
Solution Approach 2:
The patent segments the spectral filtering function across multiple independent nanostructured layers and photodetector elements. Each photodetector can be equipped with custom nanostructures optimized for specific wavelengths, enabling multispectral imaging with many channels rather than being limited to a fixed three-channel CFA pattern
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 enables the production of multispectral sensors and cameras with numerous channels, including 16 wavelengths, without mechanically moving parts or complex filter arrays, achieving narrow bandpass filters with improved spectral characteristics and reduced manufacturing costs.
Implementation Method 1
an optical polariser arranged over both transmission gratings, in particular as a polarisation layer which polarises incident optical radiation linearly
Implementation Method 2
using the Kerr or Faraday effect for precise polarisation adjustments
Implementation Method 3
using the Kerr or Faraday effect for precise polarisation adjustments
Implementation Method 4
the first nanostructured layer forms a first transmission grating from grating wires extending parallel to each other, the second nanostructured layer forms a second transmission grating from grating wires extending parallel to each other
Data Source
AI summary
The present invention relates to an optical filter with nanostructured layers and spectral sensors with layers of such kind. The optical filter has at least two nanostructured layers, each of which forms a transmission grating from grating wires extending parallel to each other. The grating wires of the two transmission gratings intersect each other and are positioned one on top of the other in the optical filter. An optical polarise which polarises incident optical radiation linearly parallel to the grating wires of one of the two transmission gratings is arranged over the transmission gratings. The optical filter can be produced as a bandpass filter with standard semiconductor processes without additional layers or modification of said processes.