Image Sensor Metal Interconnect Apertures Light Focusing
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Solution Overview
Problem
As image sensors and their pixels become smaller, they face challenges in efficiently capturing incident light, leading to reduced image quality due to light leakage and crosstalk between pixels.
Innovation Solution
The use of two levels of metal interconnect lines with strategically arranged apertures and microlenses to focus incident light onto the photosensitive region of the pixel, minimizing light leakage and crosstalk by creating an optical waveguide effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If image sensors and pixels are made smaller to reduce component size, then the area used to implement circuitry is reduced, but the ability to efficiently capture incident light deteriorates due to light leakage and crosstalk between pixels
Solution Approach 1:
The patent divides the light path management into multiple segments by introducing multiple metal layers with apertures at different depths. The first metal layer with first apertures and second metal layer with second apertures create segmented light tunnels that guide light from different incident angles to the photosensitive region, preventing light leakage and crosstalk while maintaining small pixel size
Solution Approach 2:
The patent transitions from a two-dimensional surface structure to a three-dimensional vertical structure by stacking metal layers at different heights. The apertures are positioned at different depths (first metal layer at first depth, second metal layer at second depth), creating vertical light tunnels that efficiently capture incident light from various angles without increasing horizontal pixel area
2Productivity
If pixel spacing is reduced to increase sensor resolution, then more pixels can be packed into the same area, but light leakage and crosstalk between adjacent pixels increase
Solution Approach 1:
The patent segments the light guidance function across multiple metal layers, with each layer providing aperture structures at different vertical positions. This segmentation creates isolated light tunnels for adjacent pixels, preventing lateral light migration and crosstalk even when pixels are closely spaced
Solution Approach 2:
The patent introduces metal layers with apertures as intermediary structures between the incident light and the photosensitive region. These intermediary aperture structures act as light guides that channel light vertically to the intended pixel, preventing lateral spread and crosstalk between adjacent pixels
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 arrangement enhances light focusing efficiency, reduces crosstalk, and allows for closer pixel spacing without increasing blooming, thereby improving image quality and sensitivity.
Implementation Method 1
a microlens formed over the one layer of dummy metal lines to overlap with the photodiode
Implementation Method 2
The use of two levels of metal interconnect lines with strategically arranged apertures and microlenses to focus incident light onto the photosensitive region of the pixel, minimizing light leakage and crosstalk by creating an optical waveguide effect
Implementation Method 3
a photodiode formed in a substrate in the pixel region
Data Source
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AI summary
An image sensor (100) includes a photosensitive region (102,104,106) formed in a substrate (101) of an integrated circuit. The substrate has a first layer of metal (ml) formed over the surface of the substrate so the first layer of metal defines a first aperture that has a first aperture width through with the incident light passes before illuminating the photosensitive region. The first aperture width is equal to or less than the width of the photosensitive region below the first aperture. The substrate also has a second layer of metal (tn2) formed over the first layer of metal. The second aperture has a second aperture width that is wider than the first aperture width. The first and second apertures focus the incident light onto the photosensitive region.