Photoimageable Dielectric Structure to Prevent UBM Cracking
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Solution Overview
Problem
The outermost insulating layer adjacent to the under-bump metal (UBM) in semiconductor packages tends to crack due to a low degree of curing, affecting the reliability of the package.
Innovation Solution
A semiconductor package design that includes a lower and upper redistribution layer with inner and outer insulating patterns, where the inner insulating pattern has a higher cyclization rate than the outer, using materials like polybenzoxazole (PBO) and polyhydroxyamide (PHA) to enhance mechanical strength and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single insulating layer is used to simplify the structure, then the device complexity is reduced, but the mechanical strength and reliability deteriorate due to cracking near the UBM
Solution Approach 1:
The insulating layer is segmented into two distinct patterns: an inner insulating pattern surrounding the UBM and an outer insulating pattern surrounding the inner pattern. This segmentation allows each layer to be optimized for its specific function, with the inner layer providing high mechanical strength to prevent cracking and the outer layer providing chemical resistance, thereby resolving the contradiction between structural simplicity and reliability.
Solution Approach 2:
Different regions of the insulating structure are assigned different materials and properties. The inner insulating pattern uses a material with high mechanical strength (first material) to specifically address the cracking issue near the UBM, while the outer insulating pattern uses a material with high chemical resistance (second material) for the remaining areas. This local differentiation resolves the contradiction by providing targeted solutions for different functional requirements.
2Reliability
If the insulating layer has high chemical resistance to improve reliability, then the reliability is improved, but the mechanical strength may deteriorate leading to cracking
Solution Approach 1:
The patent applies local quality by assigning different material properties to different regions. The inner insulating pattern uses a material optimized for mechanical strength to prevent cracking, while the outer insulating pattern uses a material optimized for chemical resistance. This resolves the contradiction by ensuring that each region has the appropriate material properties for its specific functional requirements.
Solution Approach 2:
The insulating structure employs a composite configuration with two different materials: a first material for the inner insulating pattern providing high mechanical strength, and a second material for the outer insulating pattern providing high chemical resistance. This composite approach allows the system to simultaneously achieve both high mechanical strength and high chemical resistance, resolving the contradiction between these two properties.
3Strength
If the insulating layer is cured at high temperature to improve mechanical strength, then the mechanical strength is improved, but the chemical resistance may deteriorate
Solution Approach 1:
The insulating layer is segmented into inner and outer patterns with different material compositions. The inner pattern uses a material that can achieve high mechanical strength through high-temperature curing, while the outer pattern uses a material that maintains high chemical resistance. This segmentation resolves the contradiction by allowing each region to be optimized for its primary function without compromising the other.
Solution Approach 2:
Different regions are assigned different material qualities: the inner insulating pattern uses a material suitable for high-temperature curing to achieve high mechanical strength near the UBM, while the outer insulating pattern uses a material with superior chemical resistance. This local quality differentiation resolves the contradiction between mechanical strength and chemical resistance.
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 enhanced mechanical and thermal properties of the inner insulating pattern reduce cracking near the UBM, improving the reliability and chemical resistance of the semiconductor package.
Implementation Method 1
The cyclization rate of the inner insulating pattern may be higher than the cyclization rate of the outer insulating pattern
Data Source
AI summary
A semiconductor package includes a frame, a semiconductor chip, a through via, a connection pad, a lower redistribution layer on the bottom surfaces of the frame and the semiconductor chip, a connection terminal on the lower redistribution layer, an encapsulant covering the top surfaces of the frame and the semiconductor chip, and an upper redistribution layer on the encapsulant. The lower redistribution layer includes a lower insulating layer, a lower redistribution pattern, and an under-bump metal (UBM). The upper redistribution layer includes an upper insulating layer, an upper redistribution pattern, an upper via, and an upper connection pad. The lower insulating layer includes an inner insulating pattern surrounding the side surface of the UBM and an outer insulating pattern surrounding the side surface of the inner insulating pattern. The cyclization rate of the inner insulating pattern is higher than the cyclization rate of the outer insulating pattern.