Integrated Spectroscopic Sensor with Tilted Thin-Film Filters
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Solution Overview
Problem
Spectroscopic sensors face challenges in downsizing due to the need for larger components like prisms and optical path lengths, which complicates their deployment in medical and agricultural applications where compactness is essential.
Innovation Solution
A spectroscopic sensor design incorporating an angle limiting filter formed on a semiconductor substrate using silicon trenches and multilayer thin films tilted at specific angles to control incident light angles and transmission wavelengths, allowing for compact size without sacrificing wavelength selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a prism and sufficient optical path length are provided to acquire a continuous spectrum, then wavelength selectivity is improved, but device size increases
Solution Approach 1:
The patent merges the functions of the angle limiting filter and the band-pass filter into a single integrated filter structure formed on the semiconductor substrate. This combination eliminates the need for separate prism components and reduces the overall device footprint while maintaining wavelength selectivity through the combined angular and spectral filtering effects.
Solution Approach 2:
The patent changes the filtering mechanism from relying on physical optical path length and prism geometry to using controlled incident angles combined with thin-film interference effects. By adjusting the incident angle parameter and the thin-film layer parameters (thickness, refractive index), the filter achieves wavelength selectivity in a compact configuration without requiring a long optical path.
2Measurement precision
If multiple separate filtering components are used to achieve wavelength selectivity, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent combines angle limiting and band-pass filtering functions into a single integrated filter component formed directly on the semiconductor substrate using semiconductor fabrication techniques. This merger reduces the number of discrete components and simplifies the overall device structure while maintaining effective wavelength selectivity through the synergistic action of angular limitation and thin-film spectral filtering.
Solution Approach 2:
The filter structure utilizes the semiconductor substrate itself as part of the filtering mechanism, where the substrate and formed holes work together to limit incident angles. This self-service approach eliminates the need for separate mounting structures and reduces assembly complexity.
3Ease of manufacture
If the filter structure is simplified for downsizing, then ease of manufacture is improved, but wavelength selectivity may deteriorate
Solution Approach 1:
The patent maintains wavelength selectivity by precisely controlling key parameters: the incident angle limitation (through hole geometry and positioning), the thin-film layer thicknesses, and the refractive indices of the alternating layers. These parameter controls ensure that even in a simplified, compact structure, the filter achieves the required spectral resolution for accurate wavelength-selective measurement.
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 design enables the creation of smaller, more versatile spectroscopic sensors with improved wavelength selectivity and simplified manufacturing, reducing the need for complex multilayer film forming steps and minimizing light loss.
Implementation Method 1
an angle limiting filter for limiting an incident angle of an incident light to a light receiving surface of the photodiode
Implementation Method 2
the angle limiting filter is formed using the semiconductor substrate left after formation of holes for receiving light in the impurity region for the photodiode from a rear surface side of the semiconductor substrate
Implementation Method 3
a light band-pass filter that transmits a specific wavelength of the incident light
Implementation Method 4
the light band-pass filter may be formed by a multilayer thin film tilted at an angle in response to the transmission wavelength relative to the semiconductor substrate
Implementation Method 5
an impurity region for a photodiode formed on a semiconductor substrate
Data Source
AI summary
A spectroscopic sensor has plural angle limiting filters that limit incident angles of incident lights, plural light band-pass filters that transmit specific wavelengths, and plural photodiodes to which corresponding transmitted lights are input. The spectroscopic sensor is a semiconductor device in which the angle limiting filters, the light band-pass filters, and the photodiodes are integrated, and, assuming that the surface on which impurity regions for the photodiodes are formed is a front surface of a semiconductor substrate, holes for receiving lights are formed in the impurity regions from the rear surface side.