UV Sensor Filter on SOI Substrate for Wavelength Selection
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Solution Overview
Problem
Conventional light sensors in electronic devices are unable to effectively filter out visible and infrared wavelengths, allowing them to detect ultraviolet (UV) light, which affects their quantum efficiency and the accuracy of UV wavelength detection.
Innovation Solution
A light sensor with a filter positioned over a photodetector on a silicon on insulator (SOI) substrate, specifically designed to block infrared and visible light while allowing UV wavelengths to pass, using a filter such as an absorption filter or McKinlay-Diffey Erythema Action Spectrum-based filter, tailored to modify the UV/visible wavelength ratio and enhance quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional light sensors are used without a filter, then the device structure is simple, but the sensor cannot effectively detect UV wavelengths due to interference from visible and infrared light
Solution Approach 1:
A filter layer is introduced as an intermediary component between the environment and the photodetector. This filter selectively transmits UV wavelengths while blocking visible and infrared light, enabling accurate UV detection without requiring complex sensor design. The filter acts as a mediator that prepares the light signal before it reaches the photodetector.
Solution Approach 2:
The solution segments the light detection function by separating wavelength filtering from photodetection. Instead of requiring the photodetector to handle all wavelengths, the system divides the task: the filter handles wavelength selection and the photodetector handles signal conversion. This segmentation improves UV detection precision while keeping each component relatively simple.
2Measurement precision
If no filter is used, then the quantum efficiency is maintained at baseline levels, but visible and infrared light interfere with UV wavelength detection
Solution Approach 1:
The filter is designed with local quality characteristics that vary by wavelength. It exhibits high transmission for UV wavelengths (280-400nm) while showing high absorption for visible and infrared wavelengths. This wavelength-dependent local quality allows the filter to improve UV detection precision while minimizing energy loss in the UV range.
Solution Approach 2:
The filter's optical parameters (transmission and absorption coefficients) are specifically engineered to change based on wavelength. By optimizing these parameters across different wavelength ranges, the system achieves high UV transmission while blocking other wavelengths, thus improving detection precision without excessive quantum efficiency loss.
3Measurement precision
If a filter is added to block visible and infrared light, then UV wavelength detection accuracy improves, but the device structure becomes more complex
Solution Approach 1:
The filter is implemented as a thin film deposited directly on the photodetector surface, rather than a bulky mechanical filter. This thin-film approach maintains UV detection accuracy while minimizing structural complexity and space requirements. The filter layer integrates seamlessly with the existing photodetector structure.
Solution Approach 2:
The filter function is merged with the photodetector structure by depositing the filter layer directly onto the photodetector surface. This integration combines two functions (filtering and detection) into a single integrated component, improving UV detection accuracy while reducing overall device complexity compared to separate filter and sensor assemblies.
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
The solution enables precise detection of UV wavelengths, improving the quantum efficiency and accuracy of UV light sensing, while reducing unwanted interference from visible and infrared light, thereby enhancing the performance of electronic devices.
Implementation Method 1
The filter is configured to filter infrared light and visible light from light received by the light sensor to at least substantially block infrared light and visible light from reaching the photodetector
Implementation Method 2
light sensors may be used by an electronic device to detect environmental conditions... Typical light sensors employ photodetectors such as photodiodes, phototransistors, or the like, which convert received light into an electrical signal
Data Source
AI summary
Techniques are provided to furnish a light sensor that includes a filter positioned over a photodetector to filter visible and infrared wavelengths to permit the sensing of ultraviolet (UV) wavelengths. In one or more implementations, the light sensor comprises a semiconductor device (e.g., a die) that includes a substrate. A photodetector (e.g., photodiode, phototransistor, etc.) is formed in the substrate proximate to the surface of the substrate. In one or more implementations, the substrate comprises a silicon on insulator substrate (SOI). A filter (e.g., absorption filter, interference filter, flat pass filter, McKinlay-Diffey Erythema Action Spectrum-based filter, UVA/UVB filter, and so forth) is disposed over the photodetector. The filter is configured to filter infrared light and visible light from light received by the light sensor to at least substantially block infrared light and visible light from reaching the photodetector. The thickness of the SOI substrate can be tailored to modify received UV/visible wavelength ratios.