Solid-State Imaging Device Light Condensing Structure
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Solution Overview
Problem
Solid-state imaging devices with global shutter structures face challenges in maintaining high sensitivity and reducing optical noise as cell size decreases, particularly due to oblique light entering memories and difficulties in forming optical waveguides.
Innovation Solution
A solid-state imaging device design featuring a semiconductor substrate with photodetectors, memories, and a configuration of transparent insulating films and projections that refract and condense light effectively, reducing oblique light components and noise, while omitting optical waveguides to simplify manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the cell size is reduced to maintain high-quality images without increasing device size, then the sensitivity decreases and optical noise increases due to difficulty in condensing light and oblique light entering memories
Solution Approach 1:
The patent divides the insulating film into multiple layers with different refractive indices (first transparent insulating film with lower refractive index, second transparent insulating film with higher refractive index). This segmentation allows each layer to perform specific optical functions: the lower refractive index layer reduces oblique light components, while the higher refractive index layer condenses light effectively. This multi-layer structure resolves the contradiction by enabling both noise reduction and light condensing in a compact cell design.
Solution Approach 2:
The patent applies different refractive index properties to different regions and layers of the insulating film structure. The first transparent insulating film (lower refractive index) is positioned closer to the photodetector to handle oblique light, while the second transparent insulating film (higher refractive index) is positioned above to enhance light condensing. This local differentiation of optical properties allows the structure to simultaneously address noise reduction and sensitivity maintenance in the reduced cell size.
2Use of energy by moving object
If optical waveguides are formed by removing interlayer insulating film and filling with constituent material, then light-gathering efficiency improves, but manufacturing complexity increases and cell size reduction becomes difficult
Solution Approach 1:
The patent extracts the optical waveguide formation process from the conventional method of removing interlayer insulating film and filling with material. Instead, it uses naturally formed insulating films with appropriate refractive indices through standard semiconductor manufacturing processes. This extraction eliminates the complex hole-filling process while maintaining light-gathering efficiency through the refractive index design of the insulating film layers.
Solution Approach 2:
The patent enables the insulating films to serve dual purposes: electrical insulation and optical waveguide functions. By selecting materials with appropriate refractive indices for the insulating films, the structure self-organizes to guide light from the photodetector to the memory without requiring additional waveguide formation steps. This self-service approach simplifies manufacturing while maintaining light-gathering efficiency.
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 device achieves significant reduction in noise and maintains high sensitivity even with reduced cell size, with a simpler manufacturing process and improved light-condensing efficiency.
Implementation Method 1
a first transparent insulating film provided in a region located directly above the photodetectors and between the plurality of metal wires, and penetrating the wiring layer; a transparent protective film covering the wiring layer and the first transparent insulating film, and having a higher refractive index than the first transparent insulating film; first projections arranged on the transparent protective film... and a second transparent insulating film provided over the first projections, and having a lower refractive index than the first projections
Data Source
AI summary
A solid state imaging device has a global shutter structure and includes: a photodetector; a wiring layer; a first transparent insulating film disposed immediately above the photodetector and penetrating the wiring layer; a transparent protective film covering the wiring layer and the first transparent insulating film, and having a higher refractive index than the first transparent insulating film; a first projection provided on the transparent protective film and having a quadrilateral shape in top view; and a second transparent insulating film having a lower refractive index than the first projection.