Light Receiving Element Separation Region Crosstalk Reduction
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Solution Overview
Problem
Existing light receiving elements used in distance measuring devices suffer from crosstalk due to reflected light from the wiring layer adjacent to the semiconductor substrate, which is not effectively blocked by the separation region, leading to noise and malfunction.
Innovation Solution
A light receiving element with a separation region in the semiconductor substrate that penetrates the substrate and has a wider width on the front surface side than the back surface side, surrounding the photoelectric conversion units and including a wiring region adjacent portion with a wider width or specific cross-sectional shapes to effectively block obliquely incident light, and optionally featuring a wiring layer protective film or insulating film for enhanced light blocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separation region is formed on the semiconductor substrate to block light from adjacent pixels, then crosstalk is reduced, but light reflected by the wiring layer can still incident on adjacent pixels causing crosstalk
Solution Approach 1:
The separation region is extended from a two-dimensional planar structure to a three-dimensional structure that penetrates through the semiconductor substrate thickness direction. By adding the depth dimension and creating a tapered shape wider at the front surface, the separation region effectively blocks light paths that were previously unaffected by planar separation, including reflected light from the wiring layer.
Solution Approach 2:
The separation region is designed with an asymmetric tapered shape where the width varies through the substrate thickness, being wider at the front surface side and narrower at the back surface side. This asymmetric geometry is specifically optimized to block obliquely incident reflected light from the wiring layer while maintaining effective separation between adjacent pixels.
2Reliability
If the separation region width is increased to block reflected light, then crosstalk from reflected light is reduced, but the device complexity increases
Solution Approach 1:
The separation region is segmented into different width portions along the thickness direction: a first width portion at the front surface side and a second width portion at the back surface side. This segmentation allows each portion to serve different functions - the wider first portion blocks reflected light while the narrower second portion maintains pixel separation, optimizing both crosstalk reduction and structural simplicity.
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 significantly reduces crosstalk by effectively blocking obliquely incident light, improving the accuracy and reliability of light detection in distance measuring devices.
Implementation Method 1
photoelectric conversion units, each photoelectric conversion unit being disposed in a semiconductor substrate to perform photoelectric conversion of incident light
Data Source
AI summary
A light receiving element includes pixels, a wiring region, and a separation region. The pixels have photoelectric conversion units, each photoelectric conversion unit being disposed in a semiconductor substrate to perform photoelectric conversion of incident light. The wiring region has a wiring layer that is connected to the photoelectric conversion unit to transmit a signal and an insulating layer that insulates the wiring layer, the wiring region being disposed adjacent to a front surface opposite to a back surface which is a surface on which the incident light is incident in the semiconductor substrate. The separation region is disposed in the semiconductor substrate at a boundary between the pixels, is formed in a shape which penetrates the semiconductor substrate and in which a width on the front surface side is wider than a width on the back surface side, and separates the photoelectric conversion units from each other.