Chip Package Trench Design for Optical Sensing
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Solution Overview
Problem
Chip packages with photodiodes face optical loss due to metal wire and dielectric layers on the incident side, leading to insufficient strength and the need for additional supporting carriers, which hinders miniaturization in front illumination designs, while backside illumination designs aim to improve transmittance but compromise on package strength.
Innovation Solution
A chip package design featuring a trench on the non-incident side aligned with the photodiode, allowing thinner chip coverage and improved light transmission, along with a conductive structure on the incident side, which enhances optical sensing sensitivity and eliminates the need for additional carriers by maintaining structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the chip is made thinner to improve light transmittance in BSI package, then optical sensing sensitivity is improved, but structural strength becomes insufficient
Solution Approach 1:
The chip structure is segmented into functional regions: the incident side maintains sufficient thickness for structural strength, while the non-incident side is thinned to improve light transmittance. This spatial segmentation allows each region to optimize for its specific function without compromising the other.
Solution Approach 2:
Different thickness characteristics are applied to different locations of the chip. The incident side (first surface) maintains original thickness for strength, while the non-incident side (second surface) is thinned locally to enhance light transmission. This local quality variation resolves the contradiction between strength and transmittance.
2Reliability
If metal wire layer and dielectric layer are placed on the incident side in FSI package, then electrical connectivity is achieved, but optical loss occurs
Solution Approach 1:
The conventional FSI structure is inverted to BSI architecture. The photodiode is positioned to receive light from the non-incident side, and the metal wire layer and dielectric layer are relocated to the incident side where they do not interfere with light propagation. This inversion eliminates optical loss while maintaining electrical connectivity.
Solution Approach 2:
The metal wire layer and dielectric layer are extracted from the light path region. By placing these conductive structures on the incident side away from the light-receiving surface, they are removed from the optical path, eliminating their harmful effect of causing optical loss while preserving their electrical function.
3Strength
If additional supporting carriers are added to BSI package to improve strength, then structural integrity is enhanced, but device complexity and size increase
Solution Approach 1:
The incident side of the chip serves multiple functions simultaneously: it provides structural strength support and houses the metal wire layer and dielectric layer for electrical connectivity. This multi-functionality eliminates the need for separate supporting carriers, reducing device complexity while maintaining structural integrity.
Solution Approach 2:
The chip structure itself provides the necessary support function through its incident side configuration. The incident side acts as a self-supporting structure that eliminates the need for external supporting carriers, making the system self-sufficient and reducing overall complexity.
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 design enables improved optical sensing sensitivity and sufficient structural strength without additional carriers, facilitating miniaturization in chip packages by allowing light to pass through the trench and be received by the photodiode effectively.
Implementation Method 1
The first surface of the chip has a photodiode... When light enters the chip package by the trench, it may easily pass through the chip covering the photodiode and then be received by the photodiode
Data Source
AI summary
A chip package includes a chip and a conductive structure. A first surface of the chip has a photodiode. A second surface of the chip facing away from the first surface has a recess aligned with the photodiode. The conductive structure is located on the first surface of the chip.