Multilayer Interconnect Light-Blocking for Solid-State Imaging
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Solution Overview
Problem
In CMOS solid-state imaging devices, reducing the thickness of the interconnect layer for light-blocking films is challenging while maintaining effective light-blocking capabilities, especially for black-level reference pixels, as the optical transmittance of metal films decreases exponentially with thickness.
Innovation Solution
A multilayer interconnect structure is implemented with two or more light-blocking films formed using metal interconnect layers and insulating layers, creating a thicker light-blocking structure without the need for an additional metal layer, enhancing light-blocking performance by forming these films in multiple layers between and above metal interconnect layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the thickness of the interconnect layer used as the light-blocking film is reduced, then the interconnect layer thickness is decreased, but the light-blocking capability becomes insufficient
Solution Approach 1:
The patent transitions from a single-layer light-blocking structure to a multi-layer structure by stacking multiple metal interconnect layers and insulating films vertically. This dimensional change allows the light-blocking film to achieve sufficient thickness for effective light blocking while maintaining a compact overall structure that satisfies miniaturization requirements.
Solution Approach 2:
The patent creates a composite light-blocking structure combining multiple metal interconnect layers (such as Cu, Al, Mo) and insulating films (such as SiO2, Si3N4). This composite structure achieves superior light-blocking performance compared to a single metal layer, as the combination of different materials with varying optical properties provides enhanced attenuation of incident light.
2Ease of manufacture
If a light-blocking film is formed at the same height as the interconnect layer, then the manufacturing process is simplified, but the light-blocking performance is insufficient for black-level reference pixels
Solution Approach 1:
The patent divides the light-blocking function across multiple discrete layers (metal interconnect layers and insulating films) rather than relying on a single layer. Each layer contributes to the overall light-blocking performance, and the segmented structure allows for better control of light attenuation while maintaining compatibility with standard CMOS manufacturing processes.
Solution Approach 2:
The patent makes the metal interconnect layers serve dual functions: electrical interconnection and light blocking. By utilizing the existing multilayer interconnect structure for both purposes, the invention eliminates the need for separate dedicated light-blocking layers, thereby simplifying the manufacturing process while achieving sufficient light-blocking performance.
3Object-affected harmful factors
If additional metal layers are added to enhance light-blocking, then light-blocking performance is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent achieves enhanced light-blocking performance by utilizing existing metal interconnect layers that are already part of the device architecture. These layers serve dual purposes as both electrical interconnects and light-blocking films, thereby improving light-blocking capability without adding dedicated light-blocking structures that would increase device complexity.
Solution Approach 2:
The patent merges the light-blocking function with the interconnect structure by combining multiple metal layers and insulating films into a unified multilayer configuration. This integration allows the light-blocking performance to be enhanced through the cumulative effect of existing layers rather than requiring separate additional light-blocking components.
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 approach effectively blocks light above black-level reference pixels, maintaining high light-blocking performance while reducing the interconnect layer thickness and shortening the light-condensing distance, without requiring an additional metal layer for light-blocking films.
Implementation Method 1
light blocking is implemented by using a metal interconnect or an optical filter for the area that is desired to be free from light incidence thereon
Data Source
AI summary
A solid-state imaging device includes: a light-receiving pixel part configured to be formed on a semiconductor substrate; a black-level reference pixel part configured to be formed on the semiconductor substrate; and a multilayer interconnect part configured to be provided over the semiconductor substrate. The multilayer interconnect part includes an insulating layer formed over the semiconductor substrate and metal interconnect layers formed as a plurality of layers in the insulating layer. The multilayer interconnect part has a first light-blocking film formed above an area between first metal interconnects of a first metal interconnect layer as one of the metal interconnect layers above the black-level reference pixel part, and a second light-blocking film that is connected to the first light-blocking film and is formed of a second metal interconnect layer over the first metal interconnect layer.