Stacked Semiconductor Pixel Unit for Simultaneous Visible and Near-Infrared Light Detection
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Solution Overview
Problem
Current semiconductor technologies face challenges in simultaneously capturing high-quality visible light and near-infrared light information for distance measurement, as existing solutions either require multiple cameras or result in inferior image resolution and high system costs.
Innovation Solution
A semiconductor pixel unit with a single substrate featuring a first semiconductor region for visible light detection and a second semiconductor region for near-infrared light detection, separated by an insulating region to enhance signal-to-noise ratio and reduce power consumption, allowing simultaneous capture of both light types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If two separate cameras (image camera and 3D camera) are used to capture both visible light and near-infrared light information, then both image information and distance information can be obtained, but system cost and device complexity increase significantly
Solution Approach 1:
The patent combines image camera and 3D camera functions into a single semiconductor pixel unit by stacking a first photodetector layer for visible light and a second photodetector layer for near-infrared light on the same substrate, with the second layer positioned below the first layer. This merging eliminates the need for two separate camera systems while capturing both image and depth information simultaneously.
Solution Approach 2:
The patent transitions from a planar two-dimensional sensor arrangement to a three-dimensional stacked architecture, where photodetectors for different wavelengths are arranged in vertical layers. This dimensional change allows multiple sensing functions to coexist within the same footprint area, reducing system complexity while maintaining information capture capabilities.
2Device complexity
If a single semiconductor substrate with stacked photodetector layers is used to simultaneously detect visible and near-infrared light, then system cost and complexity are reduced, but electrical interference between the two detection regions may occur
Solution Approach 1:
The patent introduces an insulating layer positioned between the first photodetector layer and the second photodetector layer. This intermediary insulating layer acts as an electrical barrier that prevents charge carrier diffusion and electrical interference between the two detection regions, thereby maintaining high signal-to-noise ratio while enabling integration on a single substrate.
3Adaptability or versatility
If visible light detectors are placed in the first substrate and TOF photodetectors in a second substrate as disclosed in US 2013/0234029, then both visible and near-infrared light can be detected simultaneously, but manufacturing cost increases due to bonding techniques
Solution Approach 1:
The patent merges the detection of visible and near-infrared light into a single integrated semiconductor substrate with stacked photodetector layers, eliminating the need for separate substrates and complex bonding processes. This approach maintains simultaneous detection capability while significantly simplifying manufacturing and reducing costs.
4Measurement precision
If typical time-of-flight pixels are made much larger than image sensor pixels to increase sensitivity, then near-infrared light detection sensitivity is improved, but image resolution deteriorates
Solution Approach 1:
The patent resolves the size conflict by arranging photodetectors in a vertical stack where the second photodetector layer for near-infrared detection is positioned below the first photodetector layer. This three-dimensional arrangement allows both detector types to maintain their optimal sizes for sensitivity while preserving high spatial resolution through the stacked architecture.
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 efficient and cost-effective simultaneous capture of visible and near-infrared light information with improved resolution and sensitivity, reducing system complexity and cost while maintaining image quality.
Implementation Method 1
The first semiconductor region comprises at least one visible light detector for detecting photoelectrons generated in the first semiconductor region by the visible light
Implementation Method 2
the second semiconductor region comprising at least one near infrared light detector located at the surface of the semiconductor substrate for detecting the photoelectrons generated in the second semiconductor region by the near infrared light
Implementation Method 3
means for generating a lateral electrical field in a region underneath the first semiconductor region, the electrical field being adapted for facilitating or promoting transport of photoelectrons generated in the second semiconductor region
Data Source
AI summary
A semiconductor pixel unit for sensing near-infrared light, and for optionally simultaneously sensing visible light. The pixel unit comprises a single substrate with a first semiconductor region and a second semiconductor region electrically separated by an insulating region, for example a buried oxide layer. The pixel unit is adapted for generating a lateral electrical field in the second region for facilitating transport of photoelectrons generated in the second region by near-infrared light passing through the first region and the insulating region.