On-Chip Lens Isolation in ToF Pixel Arrays to Reduce Crosstalk
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Solution Overview
Problem
Existing distance measuring sensors using the indirect time of flight (ToF) method require further improvement in sensitivity.
Innovation Solution
A light receiving device with a pixel array unit featuring a first and second tap for charge detection, an on-chip lens for each pixel, and a lens isolation portion in the same layer as the on-chip lens to isolate lenses from each other, enhancing light receiving characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If on-chip lenses are disposed for each pixel to improve light receiving characteristics, then sensitivity is improved, but crosstalk between adjacent pixels increases
Solution Approach 1:
The lens isolation portion divides the substrate into isolated regions, separating adjacent pixels and their on-chip lenses. This segmentation prevents light from one pixel's lens from interfering with adjacent pixels, thereby reducing crosstalk while maintaining the sensitivity benefits of individual on-chip lenses.
Solution Approach 2:
The lens isolation portion acts as an intermediary structure between adjacent pixels and on-chip lenses. By introducing this intermediate isolation layer, the patent prevents direct optical interference between neighboring pixels while allowing each pixel to maintain its own lens for improved light reception.
2Measurement precision
If lens isolation portion is formed to reduce crosstalk, then charge isolation efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The lens isolation portion is formed in the same layer as the on-chip lenses, combining two structures that would otherwise require separate manufacturing processes. This merging approach reduces the total number of fabrication steps while achieving both lens formation and pixel isolation functions simultaneously.
Solution Approach 2:
The same manufacturing layer serves dual purposes: forming the on-chip lenses for light collection and creating the lens isolation portions for pixel separation. This multi-functional approach simplifies the overall manufacturing process by eliminating the need for separate isolation structure fabrication.
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 improves sensitivity and reduces crosstalk between pixels, leading to enhanced charge isolation efficiency and modulation contrast.
Implementation Method 1
a first tap that detects charges photoelectrically converted by a photoelectric conversion unit and a second tap that detects charges photoelectrically converted by the photoelectric conversion unit
Data Source
AI summary
Provided is a light receiving device that includes a pixel array unit in which pixels each including a first tap that detects charges photoelectrically converted by a photoelectric conversion unit and a second tap that detects charges photoelectrically converted by the photoelectric conversion unit are two-dimensionally arranged in a matrix. The light receiving device further includes an on-chip lens disposed for each pixel on a light incident surface side of a substrate, and a lens isolation portion that is formed in the same layer as the on-chip lens and isolates the on-chip lenses from each other.