Light Sensor Reflection Layer for Thin Substrate Sensitivity
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Solution Overview
Problem
Thinning of light sensors to accommodate modern electronic devices with high screen-to-body ratios leads to reduced optical sensitivity due to light passing through the substrate, necessitating a solution to maintain sensitivity while minimizing thickness.
Innovation Solution
A reflection layer is disposed on the semiconductor substrate to reflect incident light back to the light-sensing device, ensuring optical sensitivity is maintained even when the substrate is thinned, and this is achieved through backside grinding and metallization or by coating a backplate with the reflection layer and bonding it to the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the substrate is thinned to reduce overall sensor thickness, then the device size is reduced, but optical sensitivity decreases due to light passing through the substrate
Solution Approach 1:
The patent converts the harmful effect of light passing through the thin substrate into a beneficial effect by introducing a reflection layer. This layer reflects the transmitted light back to the light-sensing device, transforming the wasted light into useful signal light, thereby maintaining optical sensitivity while keeping the substrate thin.
Solution Approach 2:
The reflection layer acts as an intermediary element between the thin substrate and the light-sensing device. It mediates the interaction by capturing light that would otherwise be lost and redirecting it to the sensing area, enabling the system to maintain sensitivity despite the reduced substrate thickness.
2Length of stationary object
If the substrate is ground thin to reduce sensor thickness, then the device can accommodate high screen-to-body ratio requirements, but the effective light-sensing area is reduced
Solution Approach 1:
The patent transforms the problem of reduced light-sensing capability caused by thin substrate into an opportunity by adding the reflection layer. This layer ensures that light passing through the thin substrate is reflected back and can be detected, effectively compensating for the reduced sensing area and maintaining measurement precision.
3Reliability
If a reflection layer is added to maintain optical sensitivity, then light sensitivity is improved, but device complexity increases
Solution Approach 1:
The reflection layer is applied selectively to specific regions of the substrate rather than uniformly across the entire surface. This localized approach maintains optical sensitivity where needed while minimizing the addition of structural complexity and material usage.
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 reflection layer effectively recycles light signals, maintaining optical sensitivity and increasing the signal-to-noise ratio of the light sensor, even when the substrate is ground thin, thus addressing the challenge of reduced sensitivity in thin light sensors.
Implementation Method 1
a reflection layer disposed on a semiconductor substrate for reflecting the incident light passing through the light-sensing area of light-sensing devices and the substrate
Data Source
AI summary
A light sensor structure and the manufacturing method thereof are disclosed. The light sensor structure includes a substrate with a first surface and a second surface opposite to each other. A light sensing element including a light sensing area is disposed on the first surface. A reflection layer is disposed on the second surface. The reflection layer covers a portion of the second surface aligning with the light sensing area.