Tapered Optical Waveguides for Void-Free Light Convergence
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Solution Overview
Problem
In semiconductor devices with metal wiring-stacked structures for miniaturization and high-speed applications, the formation of long optical waveguide films is challenging due to increased upper layer thickness, which can lead to voids and compromised light convergence and sensitivity.
Innovation Solution
A semiconductor device with a layered structure featuring tapered optical waveguide portions made of translucent materials, where each layer includes a wiring portion, an interlayer insulating film, and a tapered optical waveguide portion with a gradually reducing sectional area, formed by patterning and etching the insulating film to embed the translucent material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the thickness of the upper layer on the substrate is increased to accommodate metal wiring-stacked structure for miniaturization and high-speed applications, then the device can achieve sensor miniaturization, high-speed drive, and logic integration, but it becomes difficult to form the translucent film acting as optical waveguide member long in the stacking direction
Solution Approach 1:
The optical waveguide function is segmented across multiple separate translucent films formed in different layers, rather than requiring a single long continuous film. Each layer contains its own translucent film segment that guides light locally, eliminating the need for one continuous long film through the entire stack.
Solution Approach 2:
The solution transitions from a single-dimensional long vertical film to a multi-dimensional approach where multiple shorter films are distributed across different horizontal layers. This distributes the optical waveguide function across the layer dimension rather than relying solely on vertical continuity.
2Reliability
If the translucent film is formed long in the stacking direction, then light guidance can be achieved, but a cavity called a void might be easily generated in an inside of the translucent film
Solution Approach 1:
By dividing the optical waveguide function into multiple segments across different layers, each segment is shorter and can be formed with better process control. This segmentation prevents the formation of voids that would occur in a single long continuous film.
Solution Approach 2:
The translucent films are formed in each layer separately during the layer-by-layer construction process, allowing proper formation and consolidation of each film before proceeding to the next layer. This preliminary formation of each segment prevents void formation that would occur if attempting to form one long film.
3Reliability
If a single long translucent film is used for light guidance, then the optical waveguide function can be achieved, but the converging effect for converging light to photoelectric converting portion deteriorates and sensitivity decreases
Solution Approach 1:
Each translucent film in the stacked layers provides localized optical guidance and convergence appropriate to its specific layer position. The multiple films work together with different local convergence functions, achieving better overall light convergence at the photoelectric converting portion compared to a single long film.
Solution Approach 2:
The optical convergence function is segmented across multiple films, with each film contributing to light convergence at its specific layer level. This segmented approach allows progressive convergence of light as it passes through each layer, improving the overall converging effect and sensitivity.
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 ensures effective light guidance to the photoelectric converting portion without voids, maintaining high light convergence and sensitivity even with increased layer thickness, and prevents cavity formation during manufacturing.
Implementation Method 1
an irradiation light is converged by the microlens 6, passed through a columnar translucent film 7 formed below the microlens 6, and received by the photodiode 3a
Implementation Method 2
optical waveguide portions stacked above the photoelectric conversion portion, each of the plurality of optical waveguide portions comprising a translucent material and being shaped in a taper
Data Source
AI summary
A semiconductor device is provided and includes a substrate, a photoelectric converting portion, a plurality of optical waveguide portions stacked above the photoelectric conversion portion, each of the plurality of optical waveguide portions including a translucent material and being shaped in a taper.