Stacked SiPM Active-Area Layout for Ambient Light Rejection
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Solution Overview
Problem
Conventional image sensors suffer from limited functionality, including difficulty in determining distance to imaged objects, lower than desired image quality, and noise generation from non-target ambient light, especially when using single-photon avalanche diodes (SPADs).
Innovation Solution
The implementation of silicon photomultipliers (SiPMs) formed from stacked sensor and integrated passive component (IPC) wafers, where active areas are defined by the presence of quench resistors and inactive areas are formed by omitting them, allowing for improved signal-to-noise ratio by matching the active area to the expected light pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If single-photon avalanche diodes (SPADs) are used to improve sensitivity to incident light, then sensitivity is improved, but noise is generated in response to non-target ambient light
Solution Approach 1:
The sensor is divided into multiple pixels, each with independent SPAD elements and associated quench resistors. This segmentation allows selective activation of only those pixels receiving target light, while isolating ambient light noise to specific regions that can be individually managed or rejected.
Solution Approach 2:
Different regions of the sensor array are assigned different functional properties. Pixels in regions where target light is expected are configured with full SPAD functionality, while pixels in regions where only ambient light is present are configured with reduced functionality or disabled, creating local quality variations that optimize signal-to-noise ratio.
2Adaptability or versatility
If conventional image sensors are used, then basic imaging function is provided, but distance determination capability is limited and image quality is lower than desired
Solution Approach 1:
The sensor array is designed to perform multiple functions: standard imaging, time-of-flight distance measurement, and ambient light rejection. Each pixel functions as both an imaging element and a ranging element, eliminating the need for separate sensors and enabling versatile operation across different modes.
Solution Approach 2:
The sensor utilizes periodic modulation of the light source and corresponding time-gated detection to distinguish between target light and ambient light. By synchronizing detection windows with the modulated light source, the system achieves both accurate imaging and distance measurement while rejecting unmodulated ambient light.
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
Enhances the dynamic range and resolution of imaging systems by reducing ambient light noise, thereby improving the signal-to-noise ratio and enabling higher quality image reproduction.
Implementation Method 1
Each pixel may include a photosensitive element (such as a photodiode) that receives incident photons (light) and converts the photons into electrical signals
Implementation Method 2
single-photon avalanche diodes (SPADs) may sometimes be used in imaging systems
Data Source
AI summary
A semiconductor device may include a plurality of single-photon avalanche diode (SPAD) pixels. The semiconductor device may be a backside device that includes a sensor wafer stacked with an integrated passive component (IPC) wafer. The sensor wafer may include the SPAD pixels in an array across the sensor wafer. The IPC wafer may include active microcells that include quench resistors and dummy microcells that omit or disconnect the quench resistors. The sensor wafer may be bonded to the IPC wafer through hybrid bonding. The regions with active microcells may form active areas of the semiconductor device, while the regions with dummy microcells may form inactive areas. In this way, the active areas and inactive areas of the semiconductor device may be configurable by adjusting the active and dummy microcells of the IPC wafer.