Cross-Die Bonding Ring Structure for Misalignment-Tolerant 3D Packaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Three-dimensional semiconductor packages face challenges with bonding pad alignment and bonding strength due to small cross-section areas and coefficient of thermal expansion differences between dies, leading to increased die stress and high bonding failure rates.
Innovation Solution
The use of fusion and hybrid bonding structures, including bonding rings and lines, with enhanced surface areas to ensure better alignment and bonding strength, even in cases of die misalignment, by designing the widths and surface areas of upper and lower metal rings to provide sufficient overlap and account for variations in die thickness and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If small bonding pads are used to reduce package area, then packaging size is reduced, but bonding strength decreases and alignment precision becomes more difficult to maintain
Solution Approach 1:
The bonding structure transitions from two-dimensional bonding pads to three-dimensional bonding rings with vertical extent. The bonding rings have a first thickness in the vertical direction and a second width in the horizontal direction, creating a volumetric bonding interface that increases bonding strength while maintaining compact package footprint.
Solution Approach 2:
The bonding rings are segmented into upper and lower portions with different dimensional characteristics. The upper bonding ring portion has optimized dimensions for bonding to the first die, while the lower bonding ring portion has optimized dimensions for bonding to the second die, allowing independent optimization for each bonding interface.
2Manufacturing precision
If precise alignment is required for small bonding pads, then manufacturing complexity increases, but alignment precision improves
Solution Approach 1:
The bonding rings are designed with dimensions that provide a tolerance buffer for alignment variations. The horizontal width and vertical thickness create an overlapping bonding area that accommodates misalignment, reducing the stringency of alignment requirements during manufacturing.
Solution Approach 2:
The bonding ring dimensions (horizontal width, vertical thickness) are optimized to balance alignment tolerance with bonding strength. By adjusting these parameters, the design achieves robust bonding performance across a range of alignment conditions without requiring ultra-precise positioning.
3Area of stationary object
If bonding pads have small cross-section area, then package size is reduced, but die stress increases due to coefficient of thermal expansion differences
Solution Approach 1:
The bonding structure extends into the vertical dimension with finite thickness, creating a volumetric bonding interface rather than a planar one. This three-dimensional configuration distributes thermal stress throughout the volume of the bonding rings, reducing peak stress concentrations that would occur in thin two-dimensional bonding pads.
Solution Approach 2:
The bonding rings are formed from conductive material that provides both electrical connectivity and mechanical stress distribution. The composite structure of the bonding rings, embedded in the semiconductor device architecture, creates a stress-management system that accommodates coefficient of thermal expansion differences between stacked dies.
4Strength
If larger bonding rings are used to improve bonding strength, then package area increases, but bonding strength improves
Solution Approach 1:
The bonding strength enhancement is achieved primarily through vertical thickness rather than horizontal area expansion. The first and second thicknesses in the vertical direction provide substantial bonding interface area without proportionally increasing the horizontal footprint, maintaining compact package dimensions while achieving strong bonding.
Solution Approach 2:
The bonding ring structure is segmented into upper and lower portions with optimized dimensional ratios. This segmentation allows each portion to contribute efficiently to bonding strength while the overall structure maintains a compact footprint suitable for small-package applications.
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 bonding strength and reduces die stress, improving manufacturing yields by providing a robust bonding mechanism that accommodates misalignment and size variations between semiconductor dies.
Implementation Method 1
The bonding ring may include an upper metal ring formed in a bottom surface of the cross die and a lower metal ring formed in top surfaces of the lower dies and extending through the dielectric region, wherein the lower metal ring is bonded to the upper metal ring
Data Source
AI summary
A semiconductor die includes lower dies separated by a dielectric region; a cross die vertically stacked on the lower dies and the dielectric region; a molding structure filling the dielectric region and surrounding side surfaces of the lower dies and the cross die; and a bonding ring connecting the cross die to the lower dies and including: an upper metal ring formed in a bottom surface of the cross die; and a lower metal ring formed in top surfaces of the lower dies and extending through the molding structure in the dielectric region. The lower metal ring is bonded to the upper metal ring.