Back-Illuminated Sensor Resolution via Resin Optical Coupling
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Solution Overview
Problem
The use of back-illuminated semiconductor photodetecting elements in solid-state imaging devices leads to a reduction in resolution due to light diffusion caused by the step between the fiber optic plate and the thinned portion of the semiconductor photodetecting element, resulting in decreased spatial resolving power.
Innovation Solution
A solid-state imaging device configuration where the fiber optic plate's light exit end surface is positioned closer to the thinned portion of the semiconductor photodetecting element using a resin optically transparent to light, with a protective member and wavelength-selective filter arrangement to prevent damage and scattering, and a package design that maintains accurate fixation and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a back-illuminated semiconductor photodetecting element is adopted to improve detection sensitivity, then detection sensitivity is improved, but resolution is reduced due to light diffusion from the step between the fiber optic plate and the thinned portion
Solution Approach 1:
A resin layer is introduced as an intermediary substance between the light exit end surface of the fiber optic plate and the thinned portion of the semiconductor photodetecting element. This resin fills the step gap and provides optical coupling, preventing light diffusion while maintaining the back-illuminated structure's sensitivity advantages.
Solution Approach 2:
The refractive index of the resin is carefully selected to match or bridge the optical properties between the fiber optic plate and semiconductor substrate. By changing the optical parameters (refractive index) of the intermediary medium, light diffusion is minimized and resolution is maintained while preserving detection sensitivity.
2Reliability
If the thinned portion is left exposed to maintain optical coupling, then optical coupling is achieved, but the thinned portion becomes vulnerable to damage
Solution Approach 1:
The resin layer is applied beforehand to fill and protect the vulnerable thinned portion before final assembly. This protective layer prevents mechanical damage to the thinned area while maintaining optical coupling, addressing both reliability and strength concerns.
Solution Approach 2:
The resin used is a composite material with specific optical properties (transparency to detection wavelength, matched refractive index) and mechanical properties (protective strength, adhesion). This composite material simultaneously provides optical coupling and mechanical protection to the thinned portion.
3Manufacturing precision
If the fiber optic plate is positioned close to the thinned portion to reduce light diffusion, then resolution is improved, but the risk of damage to the thinned portion increases
Solution Approach 1:
The resin acts as a protective intermediary that enables the fiber optic plate to be positioned close to the thinned portion for optimal resolution while simultaneously protecting the thinned portion from direct contact and potential damage. The resin fills the gap and provides mechanical cushioning.
Solution Approach 2:
The resin layer forms a flexible protective film between the rigid fiber optic plate and the fragile thinned portion. This thin film allows close positioning for resolution while providing mechanical protection against damage through its compliant nature.
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 configuration suppresses the reduction in resolution by minimizing light diffusion and preventing damage to the thinned portion of the semiconductor photodetecting element, while enhancing heat dissipation and mechanical reinforcement.
Implementation Method 1
the resin being optically transparent to light to be detected... the second portion of the fiber optic plate and the thinned portion of the semiconductor photodetecting element being optically coupled through the resin
Data Source
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AI summary
A portion 41 on the light exit end surface 40b side of a fiber optic plate 40 includes a first portion 41a and a second portion 41b. The first portion 41a corresponds to a peripheral portion 23 of a semiconductor photodetecting element 20. The second portion 41b corresponds to a thin portion 25 of the semiconductor photodetecting element 20 and projects more toward the semiconductor photodetecting element 20 than the first portion 41a. A height of a step made between the first portion 41a and the second portion 41b of the fiber optic plate 40 is lower than a height of a step made between the thin portion 25 and the peripheral portion 23 of the semiconductor photodetecting element 20. The semiconductor photodetecting element 20 and the fiber optic plate 40 are fixed by a resin 45, in a state in which the first portion 41 a and the peripheral portion 23 are in contact and in which the second portion 41b and the thin portion 25 are separated.