Optical Sensor Structure Using Through-Substrate Vias
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Solution Overview
Problem
Conventional optical fingerprint sensors face challenges with increased volume, signal decay, and cost due to the need for metal wires to connect structural layers, which also lead to thermal expansion coefficient mismatches and inefficiencies in signal transmission.
Innovation Solution
The optical sensor structure employs a through-substrate via (TSV) under a light collimating layer to vertically conduct signals, replacing horizontal wire routing, and utilizes the sensor pixel array region without pixels for TSV placement, reducing volume and thickness while improving electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal wires are routed through structural layers to connect fingerprint sensor with other devices, then electrical connection is achieved, but volume increases, signal decays, and cost increases
Solution Approach 1:
The patent transitions from horizontal wire routing through structural layers to vertical through-substrate vias that penetrate the substrate thickness direction. This dimensional change allows electrical connections to be made more directly through the substrate, reducing the need for complex lateral wiring and associated structural layers, thereby decreasing overall sensor volume while maintaining reliable electrical connection.
2Reliability
If metal wires are routed through structural layers, then electrical connection is achieved, but signal decay increases
Solution Approach 1:
By routing connections vertically through the substrate via TSVs rather than horizontally through multiple structural layers, the patent shortens the effective signal path length. This direct vertical penetration reduces the distance signals must travel through lossy materials, thereby minimizing signal decay while maintaining reliable electrical connection.
3Volume of stationary object
If through-substrate vias are placed in sensor pixel array, then stacking density increases and volume decreases, but risk of overlapping with sensor pixels increases
Solution Approach 1:
The patent applies different functional zones within the sensor array, designating specific regions as suitable for TSV placement while preserving other regions for sensor pixel placement. This spatial differentiation allows TSVs to be positioned in areas that do not interfere with pixel functionality, reducing the precision requirements for via placement while still achieving volume reduction and increased stacking density.
Data Source
AI summary
An optical sensor structure is provided. The optical sensor structure includes a sensor pixel array in a substrate, a light collimating layer on the substrate, and at least one through-substrate via. The sensor pixel array has a plurality of sensor pixels. The at least one through-substrate via extends from a first surface to an opposite second surface of the substrate. The at least one through-substrate via is in the sensor pixel array and vertically misaligned with the plurality of sensor pixels.