Metallization Light Tunnel for Imaging Device Crosstalk
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Solution Overview
Problem
Current solid-state imagers face challenges with optical crosstalk due to stray light, which degrades image quality, reduces sensitivity, and causes noise, especially as pixel sizes decrease, and existing solutions like micro-lens arrays and light shields are inefficient or add complexity to the manufacturing process.
Innovation Solution
The use of patterned metallization and via layers to form a light tunnel structure that focuses light directly onto the photosensor, with apertures of varying widths to enhance light collection and reduce crosstalk, similar to the shape of the photosensor region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If micro-lens arrays are used to focus light onto photosensors, then light collection efficiency is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent combines the light focusing function with the existing metallization layers that are already part of the imager structure. The metallization layers are patterned to form light tunnels that guide light to photosensors, merging the optical guiding function with the electrical interconnect structure, thereby avoiding additional micro-lens components and reducing device complexity while maintaining light collection efficiency
Solution Approach 2:
The metallization layers serve dual purposes: they provide electrical interconnect functionality for the pixel circuitry and simultaneously act as optical waveguides to direct light to the photosensors. This multi-functionality eliminates the need for separate dedicated light-guiding structures, reducing overall device complexity while improving light collection
2Object-affected harmful factors
If light shields are formed in upper device layers to reduce optical crosstalk, then crosstalk is reduced, but manufacturing complexity and process steps increase
Solution Approach 1:
The patent integrates the light shielding function into the existing metallization layers that are already fabricated as part of the pixel circuit interconnect structure. By patterning these layers to form light tunnels with appropriate geometries, the structure simultaneously provides electrical connectivity and optical isolation, eliminating the need for separate light shield layers and reducing manufacturing complexity
Solution Approach 2:
The metallization layers, which are already present in the device structure for electrical purposes, are configured to perform the additional function of optical waveguiding and light shielding. The structure serves itself by using its own existing material layers to accomplish multiple functions without requiring additional dedicated components or process steps
3Measurement precision
If pixel size is reduced to increase array density, then imaging resolution is improved, but optical crosstalk between pixels increases
Solution Approach 1:
The patent addresses the crosstalk problem by introducing a vertical dimension to light guidance. The light tunnels extend vertically through multiple metallization layers to deliver light directly to the photosensor surface, confining light propagation in the vertical direction and preventing lateral spread that would cause crosstalk between adjacent pixels, thereby enabling higher density pixel arrays
4Adaptability or versatility
If light is allowed to penetrate deeply into silicon structure, then longer wavelengths are detected, but optical crosstalk and light loss increase
Solution Approach 1:
The patent implements preliminary light guidance through vertically extending light tunnels before light enters the silicon structure. The metallization layers are configured to confine and direct light from the top surface down to the photosensor region, ensuring that light reaches the detection zone efficiently before penetrating into the silicon. This preliminary confinement reduces lateral spread and reflection losses, enabling effective detection of longer wavelengths with reduced crosstalk
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 light tunnel structure effectively directs light onto the photosensor, reducing optical crosstalk and improving image quality by confining light rather than reflecting or refracting it, thus enhancing the spatial resolution and sensitivity of the imager without adding complexity to the manufacturing process.
Implementation Method 1
a light tunnel structure that focuses light directly onto the photosensor, with apertures of varying widths to enhance light collection and reduce crosstalk
Implementation Method 2
The light tunnel structure effectively directs light onto the photosensor, reducing optical crosstalk and improving image quality by confining light rather than reflecting or refracting it
Data Source
AI summary
A pixel cell and imager device, and method of forming the same, where the pixel cell has a plurality of metallization and via layers formed over a photosensitive region. The metallization and via layers form a step-like light tunnel structure that augments the photosensitive region's ability to capture light impinging on the photosensitive region.