Multi-Die Package Buffer Layer for Thermal Stress and Delamination
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving compact and reliable integration of multiple dies in a package structure due to thermal stress and adhesion issues, which can lead to cracks and delamination, particularly in 3D packaging and 3DIC devices.
Innovation Solution
A method involving the use of a buffer layer with a lower Young's modulus than the encapsulant, formed by patterning a photoresist material, to protect the dies from thermal stress and improve adhesion between encapsulants, while also forming a redistribution layer and connectors to connect the dies electrically and facilitate the release of the package structure from a carrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple dies are integrated in a compact package structure, then integration density is improved, but thermal stress and adhesion issues worsen leading to cracks and delamination
Solution Approach 1:
A buffer layer is introduced as an intermediary component between the first encapsulant and the second encapsulant. This buffer layer has a Young's modulus lower than both encapsulants, allowing it to absorb and distribute thermal stress, preventing direct stress transmission that would cause cracks and delamination at the interface between different encapsulants with mismatched thermal expansion coefficients.
Solution Approach 2:
The patent changes the mechanical parameter (Young's modulus) of the buffer layer to be lower than both encapsulants. This parameter change enables the buffer layer to deform more easily under thermal stress, accommodating the differential thermal expansion between encapsulants and reducing the risk of cracking and delamination while maintaining compact integration.
2Adaptability or versatility
If encapsulants with different thermal expansion coefficients are used, then material compatibility is improved, but thermal stress worsens causing cracks and delamination
Solution Approach 1:
The buffer layer serves as a mediator between encapsulants with different thermal expansion coefficients. Its lower Young's modulus allows it to accommodate the thermal expansion differences through elastic deformation, preventing the development of high thermal stresses that would otherwise cause cracks and delamination at the encapsulant interfaces.
Solution Approach 2:
The buffer layer is positioned in advance between the encapsulants to provide cushioning against thermal stress. By having this compliant layer in place before thermal cycling occurs, the system is pre-configured to absorb thermal expansion differences, preventing stress concentration and subsequent failure modes such as cracking and delamination.
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
This approach enhances the yield and reliability of the package structure by reducing thermal stress and improving adhesion, allowing for the successful integration of multiple dies in a compact and reliable manner.
Implementation Method 1
the buffer layer has a Young's modulus less than a Young's modulus of the first encapsulant and a Young's modulus of the second encapsulant
Implementation Method 2
formed by patterning a photoresist material
Data Source
AI summary
A package structure and a method of forming the same are provided. The package structure includes a first die, a second die, a first encapsulant, and a buffer layer. The first die and the second die are disposed side by side. The first encapsulant encapsulates the first die and the second die. The second die includes a die stack encapsulated by a second encapsulant encapsulating a die stack. The buffer layer is disposed between the first encapsulant and the second encapsulant and covers at least a sidewall of the second die and disposed between the first encapsulant and the second encapsulant. The buffer layer has a Young's modulus less than a Young's modulus of the first encapsulant and a Young's modulus of the second encapsulant.