Conductive Buffer Layers for Reliable Hybrid Die Bonding
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Solution Overview
Problem
Semiconductor packages with stacked semiconductor dies face challenges in reducing height and minimizing signal propagation delays due to bond wire arrangements, which often result in inadequate recess depths of conductive pads leading to oxide openings or resistive joints.
Innovation Solution
The introduction of a conductive buffer layer between conductive pads in semiconductor dies, which is porous and flexible, allowing for wider tolerances in recess depth variations and facilitating metallurgical bonding through CTE-based expansion, thereby forming robust interconnects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If bond wires are used to connect semiconductor dies in a stacked configuration, then the footprint of the semiconductor package is reduced, but the overall height of the package increases and signal propagation delays are introduced
Solution Approach 1:
A conductive buffer layer is introduced as an intermediary between the conductive pads of adjacent semiconductor dies. This buffer layer facilitates direct die-to-die bonding, eliminating the need for bond wires. The buffer layer comprises a porous flexible material that accommodates variations in recess depth, enabling reliable metallurgical bonding while reducing package height compared to bond wire approaches.
Solution Approach 2:
The conductive buffer layer undergoes parameter changes through CTE-based expansion during the bonding process. The flexible porous material expands to fill gaps and accommodate recess depth variations, enabling robust metallurgical bonding between conductive pads. This parameter change allows direct bonding without requiring precise control of recess depths, simplifying the bonding process and reducing package height.
2Device complexity
If conductive pads are directly bonded without a buffer layer, then the bonding process is simpler, but variations in recess depth lead to oxide openings or resistive joints
Solution Approach 1:
The conductive buffer layer serves as a beforehand cushioning layer between the conductive pads of adjacent dies. This porous flexible material is positioned in advance to accommodate variations in recess depth that occur during manufacturing. The buffer layer prevents oxide openings and resistive joints by maintaining intimate contact between conductive pads despite dimensional variations, thereby improving bonding reliability without significantly increasing process complexity.
Solution Approach 2:
The conductive buffer layer is made of a porous flexible material that can deform and expand to accommodate variations in recess depth. The porous structure allows the material to be compressed and expanded during the bonding process, ensuring reliable metallurgical bonding between conductive pads even when recess depths vary. This use of porous materials enables robust bonding while keeping the overall structure compact.
3Reliability
If the recess depth of conductive pads is precisely controlled, then oxide openings and resistive joints are minimized, but manufacturing complexity and cost increase
Solution Approach 1:
The conductive buffer layer undergoes parameter changes through CTE-based expansion during the bonding process. This expansion allows the buffer layer to accommodate variations in recess depth that would otherwise lead to bonding defects. By utilizing this parameter change, the invention relaxes the manufacturing precision requirements for recess depth control while maintaining reliable metallurgical bonding between conductive pads.
Solution Approach 2:
The porous flexible material in the conductive buffer layer can be compressed and expanded to fill gaps caused by recess depth variations. This porosity allows the material to adapt to dimensional variations without requiring precise control of recess depths, thereby reducing manufacturing complexity and cost while maintaining connection reliability.
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 conductive buffer layer enhances the reliability and yield of hybrid bonding processes by accommodating variations in recess depths, ensuring stable metal-to-metal connections and reducing the risk of oxide openings or resistive joints.
Implementation Method 1
facilitating metallurgical bonding through CTE-based expansion
Data Source
AI summary
Conductive buffer layers for semiconductor die assemblies, and associated systems and methods are disclosed. In an embodiment, a semiconductor die assembly includes first and second semiconductor dies directly bonded to each other. The first semiconductor die includes a first copper pad and the second semiconductor die includes a second copper pad. The first and second copper pads form an interconnect between the first and second semiconductor dies, and the interconnect includes a conductive buffer material between the first and second copper pads, where the conductive buffer material includes aggregates of conductive particles. In some embodiments, the first and second copper pads are not conjoined but electrically connected to each other through the conductive buffer material. In some embodiments, the conductive buffer material is porous such that the aggregates of conductive particles can be compressed together in response to the pressure applied to the conductive buffer layer.