Photodiode Lens Stack Structure for Safe Substrate Thinning
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Solution Overview
Problem
The existing detection devices using PIN photodiodes face challenges in thinning the substrate due to damage during the polishing process, particularly with microlenses formed on the array substrate.
Innovation Solution
A detection device is designed with a substrate, photodiodes, a protective film, and lenses where the substrates are stacked with projections that allow for polishing without damaging the lenses, enabling the thinning of the substrate while maintaining the integrity of the optical filter and photodiodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the substrate is thinned by polishing the array substrate, then the detection device becomes thinner, but the microlenses formed on the array substrate are damaged in the polishing process
Solution Approach 1:
The invention divides the optical system into two separate substrates: one substrate carries the photodiodes and the other substrate carries the microlenses. This segmentation allows each substrate to be processed independently, enabling the array substrate to be thinned by polishing without damaging the microlenses, as they are formed on a different substrate that is bonded to the array substrate via a bonding substrate.
2Length of moving object
If the array substrate is polished to thin the detection device, then the device thickness is reduced, but the polishing process causes damage to the microlenses
Solution Approach 1:
By separating the microlenses from the array substrate and forming them on a different substrate, the invention enables independent processing. The array substrate can be polished to achieve thinning without compromising lens surface quality, as the lenses are protected on their own substrate.
Solution Approach 2:
A bonding substrate is introduced as an intermediary between the array substrate and the microlens substrate. This bonding substrate allows the array substrate to be thinned by polishing while maintaining the structural integrity and surface quality of the microlenses on the separate substrate.
3Length of moving object
If the substrate is made thinner, then the detection device is more compact, but the structural stability during polishing becomes difficult to maintain
Solution Approach 1:
The invention segments the detection device into multiple substrates (array substrate, bonding substrate, and microlens substrate). This segmentation allows the array substrate to be thinned to achieve compactness while the bonding substrate provides structural support, maintaining overall structural stability during polishing and assembly processes.
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 allows for the successful thinning of the substrate while reducing damage to the lenses and improving the detection device's manufacturing efficiency and accuracy.
Implementation Method 1
the projection of one of the detection devices abuts on a portion of another of the detection devices facing the one detection device
Implementation Method 2
polishing a second principal surface on an opposite side of the first principal surface of each of the substrates in a state where the pair of the substrates are stacked together
Implementation Method 3
a plurality of lenses provided for each of the photodiodes so as to face the photodiode
Data Source
AI summary
According to an aspect, a detection device includes: a substrate; a plurality of photodiodes arranged on a first principal surface of the substrate; a protective film that covers the photodiodes; a plurality of lenses provided for each of the photodiodes so as to face the photodiode with the protective film interposed between the lenses and the photodiodes; and a projection provided between the lenses. A top of the projection is located at a position higher than a top of each of the lenses when viewed from the first principal surface.