Light Sensor With Through-Substrate Vias and IR Suppression Filter
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Solution Overview
Problem
Existing light sensors face challenges in effectively filtering out infrared light while allowing visible light to reach photodetectors, leading to reduced sensitivity and limited spectral detection capabilities, particularly in gesture sensing devices where accurate ambient light detection is crucial.
Innovation Solution
A light sensor design incorporating an IR suppression filter and color pass filters integrated on-chip, with a transparent substrate providing support and encapsulation, allows for selective blocking of infrared light while passing visible light to photodetectors, enabling improved sensitivity and spectral detection across a range of wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an IR suppression filter is added to block infrared light, then infrared interference is reduced, but visible light transmission and sensitivity may be compromised
Solution Approach 1:
The optical filtering function is segmented into multiple specialized filters: an IR suppression filter layer positioned over the photodetector array to block infrared wavelengths, and color pass filters (red, green, blue) positioned over respective photodetectors to transmit specific visible light wavelengths. This segmentation allows each filter to optimize its function without compromising the other, resolving the contradiction between IR blocking and visible light transmission.
Solution Approach 2:
Different regions of the light sensor have different filtering characteristics applied locally. The IR suppression filter provides uniform infrared blocking across all photodetectors, while color pass filters provide wavelength-selective transmission only at their specific locations. This local quality approach ensures that infrared interference is suppressed globally while visible light transmission is optimized locally at each photodetector position.
2Adaptability or versatility
If multiple filters are integrated on-chip, then spectral detection capability is improved, but device complexity increases
Solution Approach 1:
Multiple filtering functions (IR suppression and color pass filtering) are merged into a single integrated filter assembly that is positioned over the photodetector array. The filters are integrated at the wafer level with through-substrate vias providing electrical connections, combining what could have been separate components into one unified structure. This merging reduces the number of discrete parts and simplifies the overall device architecture while maintaining multi-spectral detection capability.
Solution Approach 2:
The filter assembly serves multiple functions simultaneously: the IR suppression filter blocks infrared wavelengths across all detectors, while the color pass filters enable wavelength-selective detection in the visible spectrum. Through-substrate vias provide both mechanical support and electrical connectivity. This multi-functionality allows a single integrated component to perform what would otherwise require multiple separate elements, reducing device complexity while enhancing spectral detection versatility.
3Stability of the object's composition
If a transparent substrate is used to support the filter, then filter stability is improved, but manufacturing complexity increases
Solution Approach 1:
The transparent substrate and filter structures are prepared and positioned in advance during wafer fabrication, before final device assembly. Through-substrate vias are formed and conductive materials are deposited preliminarily, establishing a stable foundation that simplifies subsequent manufacturing steps. This preliminary action ensures filter stability is achieved through integrated design rather than post-assembly adjustments, reducing overall manufacturing complexity.
Solution Approach 2:
The transparent substrate acts as an intermediary element between the filter structures and the photodetector array. It provides mechanical support and stability to the filters while maintaining optical transparency to allow light transmission. The substrate mediates the connection between the filter assembly and the underlying photodetectors, simplifying the manufacturing process by providing a stable platform for filter integration without requiring complex direct bonding techniques.
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 enhances the light sensor's ability to detect ambient light conditions and infrared signals, improving the performance of gesture sensing devices by increasing sensitivity and accuracy in light detection, thereby enhancing the control of display brightness and other device functions.
Implementation Method 1
An IR suppression filter is positioned over the photodetectors. The IR suppression filter is configured to filter infrared light from light incident on the light sensor to at least substantially block infrared light from reaching the photodetectors
Implementation Method 2
Typical light sensors employ photodetectors such as photodiodes, phototransistors, or the like, which convert received light into an electrical signal (e.g., a current or voltage)
Data Source
AI summary
Techniques are described to furnish an IR suppression filter that is formed on a glass substrate to a light sensor. In one or more implementations, a light sensor includes a substrate having a surface. One or more photodetectors are formed in the substrate and configured to detect light and provide a signal in response thereto. An IR suppression filter configured to block infrared light from reaching the surface is formed on a glass substrate. The light sensor also includes a plurality of color pass filters disposed over the surface. The color pass filters are configured to filter visible light to pass light in a limited spectrum of wavelengths to the one or more photodetectors. A buffer layer is disposed over the surface and configured to encapsulate the plurality of color pass filters and adhesion layer. The light sensor further includes through-silicon vias to provide electrical interconnections between different conductive layers.