Silicon Passivation for Through-Silicon Via Imaging Reliability
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Solution Overview
Problem
The existing wafer level chip size package (WLCSP) process for imaging devices faces issues with deformation of through silicon vias due to resin-based passivation films, leading to spot defects and conduction failures during temperature cycle tests due to stress-related expansion and contraction.
Innovation Solution
A passivation film containing silicon, such as silicon oxide, silicon nitride, or silicon carbonitride, is used to cover the through silicon via and connection terminal, alleviating stress and preventing deformation, with a thickness of 30 nm to 50 nm, and formed using chemical vapor deposition or atomic layer deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resin-based passivation film is used to cover the through silicon via, then corrosion prevention and insulation are improved, but stress-induced deformation of the through silicon via occurs leading to spot defects
Solution Approach 1:
The patent changes the material parameter of the passivation film from resin to silicon-based material. This material substitution fundamentally alters the thermal expansion characteristics, reducing the stress differential that causes through silicon via deformation while maintaining corrosion protection and insulation properties.
Solution Approach 2:
The patent employs a composite structure by integrating the silicon-based passivation film with the underlying silicon substrate and copper-filled through silicon vias. This composite material system ensures compatible thermal expansion coefficients, minimizing stress-induced deformation while providing effective corrosion barrier and electrical insulation.
2Reliability
If a resin-based passivation film is used, then insulation is ensured, but solder deforms during temperature cycle tests due to expansion and contraction stress
Solution Approach 1:
The patent changes the thermal expansion parameter of the passivation film by substituting resin with silicon-based material. This reduces the thermal expansion coefficient mismatch between the passivation film and solder, minimizing deformation stress during temperature cycling while preserving insulation performance.
Solution Approach 2:
The patent addresses thermal expansion issues by selecting a silicon-based passivation film whose thermal expansion characteristics are matched to the silicon substrate and solder materials. This reduces differential expansion and contraction during temperature cycle tests, preventing solder deformation and maintaining connection integrity.
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 use of silicon-based passivation films reduces stress on through silicon vias and solder balls, minimizing spot defects and conduction failures, thereby enhancing the reliability and performance of imaging devices.
Implementation Method 1
The passivation film contains at least silicon... alleviating stress and preventing deformation
Implementation Method 2
formed using chemical vapor deposition or atomic layer deposition
Implementation Method 3
formed using chemical vapor deposition or atomic layer deposition
Data Source
AI summary
An imaging device capable of suppressing at least one of defects caused by a passivation film is provided. An imaging device according to an embodiment of the present disclosure includes a substrate, a pixel circuit provided on the substrate, a through silicon via that penetrates the substrate and is electrically connected to the pixel circuit, and a passivation film that covers the through silicon via. The passivation film contains at least silicon.