TaN/AlCu Metallization for 3D Interconnect Bonding
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Solution Overview
Problem
The existing methods for bonding semiconductor substrates in three-dimensional interconnects face challenges such as poor wetting between copper and conventional eutectic solder, oxidation of copper, and the large size of solder bumps, which hinder the reliability and scalability of interconnects.
Innovation Solution
A structure comprising a conductive stack with a Cu layer, a TaN layer, and an AlCu layer on the metal pads of a substrate, which allows for reliable bonding between substrates without the need for solder bumps, utilizing a TaN/AlCu film for improved adhesion and reduced package size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional eutectic solder is used for bonding copper surfaces, then the bonding process is simple, but the wetting is poor and bonding area is insufficient
Solution Approach 1:
The patent applies composite materials by creating a multi-layer metallization structure consisting of Cu/Ni/Au layers on the substrate and Ta/Ni/Sn layers on the bump. This composite structure improves wetting characteristics and bonding reliability while maintaining manufacturing simplicity. The specific combination of metals is selected to optimize interfacial adhesion and prevent oxidation, directly addressing the poor wetting issue with conventional solder alone.
Solution Approach 2:
The patent introduces intermediate layers (Ni and Au on substrate, Ni and Sn on bump) that act as mediators between the copper surfaces. These intermediate layers facilitate better wetting and bonding by providing compatible interfaces, preventing direct oxidation of copper, and enabling reliable metallurgical bonding. The Ni/Au/Ta/Ni/Sn stack serves as an intermediary system that resolves the wetting problem without complicating the overall bonding process.
2Reliability
If solder bumps are used for substrate bonding, then bonding is achieved, but copper oxidation occurs during the solder process
Solution Approach 1:
The patent applies preliminary action by pre-depositing protective metallization layers (Ni and Au on substrate, Ni and Sn on bump) before the bonding process. These layers are formed in advance to prevent copper oxidation during subsequent soldering and bonding operations. The preliminary metallization stack serves as a protective barrier that eliminates oxidation issues without affecting bonding achievement.
Solution Approach 2:
The patent creates an inert environment by using non-oxidizing metal layers (Au, Ni, Sn) that protect the reactive copper surfaces from oxidation. The metallization stack effectively isolates copper from oxygen exposure during the bonding process, creating a chemically inert interface that prevents harmful oxidation while maintaining bonding reliability.
3Reliability
If large size solder bumps are used for bonding, then bonding reliability is achieved, but device shrinkage is hindered
Solution Approach 1:
The patent applies parameter changes by modifying the size and composition parameters of the bonding structures. The metallization layers are deposited with controlled thicknesses (e.g., 100-500 nm for Ni, 50-200 nm for Au) that provide sufficient bonding strength while occupying minimal volume. This parameter optimization enables device shrinkage while maintaining bonding reliability through enhanced interfacial adhesion rather than relying on large bump volume.
Solution Approach 2:
The patent utilizes thin films by replacing traditional thick solder bumps with ultrathin metallization layers (total thickness in the micrometer range compared to millimeter-scale solder bumps). The multi-layer thin film structure provides adequate mechanical strength and bonding reliability through distributed stress and enhanced interfacial area, enabling significant device size reduction while maintaining performance.
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 TaN/AlCu film provides enhanced bonding reliability and scalability by ensuring better contact between copper surfaces, reducing oxidation issues, and enabling finer pitch assembly, thus improving the yield and reliability of three-dimensional interconnects while allowing for the miniaturization of semiconductor devices.
Implementation Method 1
forming a TaN/AlCu film on the metal pads of a first substrate for three-dimensional interconnects
Data Source
AI summary
A method provides a first substrate with a conductive pad and disposes layers of Cu, TaN, and AlCu, respectively, forming a conductive stack on the conductive pad. The AlCu layer of the first substrate is bonded to a through substrate via (TSV) structure of a second substrate, wherein a conductive path is formed from the conductive pad of the first substrate to the TSV structure of the second substrate.