Funneled Light Pipe for Pixel Sensors Without Micro-Lenses
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Solution Overview
Problem
Advanced pixel sensors with vertical light pipes often rely on micro-lenses for focusing light, which is not ideal and requires a new structure without micro-lenses.
Innovation Solution
A pixel sensor structure featuring a semiconductor substrate with a photo collection region and a funneled light pipe that includes a bottom cylindrical portion and a tapered funneled portion in direct contact, fabricated using a BEOL layer etching process to form cylindrical and funneled cavities filled with a transparent material, optionally with a light reflective layer on the side walls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If micro-lenses are used to focus light into vertical light pipes, then light collection efficiency is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent removes the micro-lens component from the traditional light pipe structure and replaces it with a funneled light pipe design that uses the light pipe's own geometry to focus light. This extraction of the micro-lens simplifies the device while maintaining light collection functionality through the tapered shape of the light pipe itself.
Solution Approach 2:
The patent combines the light pipe structure with the light-focusing function by integrating the funnel shape directly into the light pipe. Instead of having separate micro-lens and light pipe components, the light pipe itself is designed with a tapered geometry that performs both light collection and focusing functions simultaneously.
2Use of energy by moving object
If micro-lenses are used to focus light, then light focusing capability is improved, but manufacturing precision requirements increase
Solution Approach 1:
By removing the micro-lens component, the patent eliminates the need for high-precision micro-lens fabrication and assembly. The focusing function is achieved through the bulk geometry of the light pipe itself, which can be manufactured with standard semiconductor fabrication processes without requiring ultra-precise micro-optical components.
Solution Approach 2:
The patent replaces the mechanical micro-lens system with a geometric light pipe structure. Instead of using a separate optical component (micro-lens) to focus light, the tapered geometry of the light pipe itself creates the focusing effect through its shape, substituting a simpler geometric form for a complex mechanical optical system.
3Device complexity
If funneled light pipe without micro-lenses is used, then device complexity is reduced, but light collection efficiency may deteriorate
Solution Approach 1:
The patent employs a tapered, funnel-shaped geometry for the light pipe that utilizes curved surfaces to guide and focus light. The gradual tapering of the light pipe creates a smooth optical path that efficiently directs light from the color filter array to the photo diode, maintaining high light collection efficiency without requiring sharp optical elements like micro-lenses.
Solution Approach 2:
The patent optimizes the geometric parameters of the funneled light pipe, including the taper angle, diameter variations, and wall thickness profiles, to achieve effective light focusing. By carefully designing these dimensional parameters, the light pipe efficiently collects and directs light while maintaining structural integrity and manufacturability.
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
This design enhances light collection and reflection, ensuring that more photons reach the photo diodes without the need for micro-lenses, improving the overall efficiency of the pixel sensor.
Implementation Method 1
a light reflective layer on side walls of the bottom cylindrical portion and the funneled portion
Data Source
AI summary
A photo sensing structure and methods for forming the same. The structure includes (a) a semiconductor substrate and (b) a photo collection region on the semiconductor substrate. The structure also includes a funneled light pipe on top of the photo collection region. The funneled light pipe includes (i) a bottom cylindrical portion on top of the photo collection region of the photo collection region, and (ii) a funneled portion which has a tapered shape and is on top and in direct physical contact with the bottom cylindrical portion. The structure further includes a color filter region on top of the funneled light pipe.