Avalanche Ranging Image Sensor Layout for Uniform Pixels
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Solution Overview
Problem
Existing ranging image sensors face challenges in achieving uniform light receiving sensitivity across multiple pixels, leading to variations in sensitivity and potential crosstalk between adjacent pixels.
Innovation Solution
The ranging image sensor incorporates a semiconductor layer with continuous avalanche multiplication regions over multiple pixels, separated by trenches, and includes conductive type regions and electrodes to enhance sensitivity and reduce crosstalk, along with a wiring layer for signal input and output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the avalanche multiplication region is made continuous over multiple pixels, then light receiving sensitivity is improved uniformly, but crosstalk between adjacent pixels increases
Solution Approach 1:
The continuous avalanche multiplication region is segmented by introducing trenches that extend from the first surface to the second surface of the semiconductor layer. These trenches physically divide the continuous region into pixel-specific sections, preventing crosstalk while maintaining the benefits of continuity within each pixel. The trench structure creates electrical isolation between adjacent pixels through the depletion region formed in the avalanche multiplication region near the trench interface.
Solution Approach 2:
The patent applies different structural characteristics to different spatial locations: within each pixel, the avalanche multiplication region maintains continuity for high sensitivity, while at pixel boundaries, trenches introduce discontinuity to prevent crosstalk. This local differentiation allows the system to simultaneously achieve both uniform sensitivity improvement and crosstalk suppression by optimizing the structure for its specific functional requirement at each location.
2Object-affected harmful factors
If the avalanche multiplication region reaches the trench to suppress crosstalk, then pixel separation is improved, but manufacturing complexity increases
Solution Approach 1:
The trenches are formed in the semiconductor layer before the avalanche multiplication region is created through ion implantation or diffusion. This preliminary formation of the trench structure establishes the pixel boundaries in advance, guiding subsequent processing steps and ensuring that the avalanche multiplication region develops with appropriate confinement near the trenches. This sequencing simplifies manufacturing by providing a physical template for subsequent dopant diffusion or implantation patterns.
3Productivity
If multiple charge transfer regions are added to each pixel, then charge transfer capability is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple charge transfer functions into a single integrated charge transfer region that connects to both the first and second multiplication regions. Rather than creating separate independent transfer paths, the design merges the charge collection and transfer functionality into one region that handles charges from both multiplication regions, reducing the number of discrete components while maintaining comprehensive charge transfer capability.
Solution Approach 2:
The charge transfer region is designed with multi-functionality, serving as both a collection point for charges from the first multiplication region and a transfer path to the second multiplication region. This universal structure performs multiple functions (charge collection, charge storage, and charge transfer) within a single region, eliminating the need for separate dedicated structures for each function and thereby reducing overall device complexity.
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 achieves uniform light receiving sensitivity across pixels while minimizing sensitivity variations and crosstalk, enhancing overall sensor performance.
Implementation Method 1
an avalanche multiplication region including a first conductive type first multiplication region formed in the semiconductor layer and a second conductive type second multiplication region formed on the first side of the first multiplication region in the semiconductor layer
Data Source
AI summary
A ranging image sensor includes a semiconductor layer and an electrode layer. The semiconductor layer and the electrode layer form a plurality of pixels. Each of the plurality of pixels includes an avalanche multiplication region, a charge distribution region, a first charge transfer region, and a second charge transfer region in the semiconductor layer. Each of the plurality of pixels includes a photogate electrode, a first transfer gate electrode, and a second transfer gate electrode in the electrode layer. The avalanche multiplication region is continuous over the plurality of pixels or reaches a trench formed in the semiconductor layer so as to separate the plurality of pixels from each other.