Stacked Memory Package Structure With Trench-Separated Underfill
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Solution Overview
Problem
Existing semiconductor package structures face challenges in reducing warpage due to thermal expansion mismatch between underfill material and the substrate, leading to inefficiencies in packaging and potential yield losses.
Innovation Solution
The formation of trenches in the substrate to separate the underfill material into discrete portions, reducing warpage by blocking underfill bridging and minimizing shrinkage volume, combined with a method of stacking memory dies and using a package layer to protect the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If underfill material is used to fill the cavity between stacked die, then voids are reduced and mechanical support is improved, but thermal expansion mismatch causes warpage
Solution Approach 1:
The underfill material is divided into discrete portions by trenches formed in the substrate. Each portion is contained within a defined region, preventing continuous underfill bridging across the entire substrate. This segmentation reduces the cumulative shrinkage stress that causes warpage while maintaining localized mechanical support between stacked dies.
Solution Approach 2:
The substrate is modified with trenches at specific locations to create regions with different properties. Areas with underfill material provide mechanical support, while trench regions provide relief from shrinkage stress. This local differentiation allows the structure to have both support and warpage reduction in different zones.
2Reliability
If underfill material is dispersed into cavities between adjacent memory dies, then voids are eliminated, but shrinkage volume causes warpage
Solution Approach 1:
Trenches are formed in the substrate to divide the underfill material into discrete portions. Each portion fills the cavity between adjacent memory dies, eliminating voids locally, while the trenches prevent continuous shrinkage across the substrate, reducing overall warpage.
Solution Approach 2:
The trenches act as intermediary structures between regions of underfill material. They provide a physical barrier that mediates the interaction between adjacent underfill portions, preventing their shrinkage forces from combining and causing excessive warpage while still allowing each portion to eliminate voids in its local cavity.
3Shape
If trenches are formed in substrate to separate underfill material, then warpage is reduced, but manufacturing complexity increases
Solution Approach 1:
The substrate is segmented with trenches that can be formed using standard semiconductor fabrication techniques. This segmentation approach to warpage reduction leverages existing manufacturing capabilities, minimizing the increase in manufacturing complexity while achieving the desired shape control.
4Strength
If package layer is formed to protect structure, then mechanical protection is improved, but thermal expansion mismatch is exacerbated
Solution Approach 1:
The package layer is applied over a substrate that has already been segmented with trenches to contain underfill material. This pre-segmentation of the underlying structure prevents the package layer from experiencing continuous thermal expansion stress across its entire area, reducing warpage while maintaining mechanical protection.
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 effectively reduces warpage and improves the yield and performance of semiconductor package structures by managing thermal expansion and underfill material distribution.
Implementation Method 1
an underfill layer is formed in a cavity between two adjacent memory dies
Implementation Method 2
warpage due to thermal expansion mismatch between underfill material and the substrate
Data Source
AI summary
A package structure is provided. The package structure includes a through substrate via structure, a first stacked die package structure, an underfill layer, and a package layer. The through substrate via structure is formed over a substrate. The first stacked die package structure is over the through substrate via structure, wherein the first stacked die package structure comprises a plurality of memory dies. The underfill layer is over the first stacked die package structure. the package layer is over the underfill layer, wherein the package layer has a protruding portion that extends below a top surface of the through substrate via structure.