SiC Die Attach Metallization With Low-Void Sputtered Eutectic Alloy
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Solution Overview
Problem
In semiconductor device die attach operations, the incorporation of sputter gas byproducts, such as argon (Ar), leads to void formation in die attach material layers, resulting in poor thermal performance, delamination, and reduced reliability, especially in high-power and high-frequency devices with larger die sizes and varying coefficients of thermal expansion between substrate materials.
Innovation Solution
The use of heavier noble gases like krypton (Kr), xenon (Xe), or radon (Rn) in the sputter gas reduces void formation by minimizing the incorporation of sputter gas contaminants into the die attach material layer, with a sputtering process that forms a die attach material layer with a void percent of 15% or less and a contact area greater than one square millimeter, and includes a metal interlayer to prevent contact with the barrier metal layer during phase transition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If argon (Ar) is used as sputter gas to deposit die attach material layer, then the deposition process is simple and cost-effective, but void formation occurs leading to poor thermal performance and delamination
Solution Approach 1:
The patent changes the sputter gas parameter from argon to heavier noble gases (krypton, xenon, or radon). This parameter change reduces void formation in the die attach material layer by minimizing gas incorporation during deposition, thereby improving thermal performance and bonding strength while maintaining process simplicity
Solution Approach 2:
The patent employs a composite metallization structure consisting of multiple layers including barrier metal layer, die attach material layer, and optional copper layer. This composite structure enhances overall reliability by combining materials with complementary properties - the barrier layer prevents diffusion, the die attach material provides thermal conductivity, and the copper layer improves electrical conductivity
2Productivity
If die attach material layer is deposited with conventional sputter gas, then deposition rate is high, but void percent increases leading to delamination
Solution Approach 1:
The patent changes the sputter gas from light noble gas (argon) to heavy noble gases (krypton, xenon, radon). This parameter change maintains high deposition rates while significantly reducing void formation in the die attach material layer, achieving both productivity and manufacturing precision
3Device complexity
If barrier metal layer is directly contacted with die attach material layer during phase transition, then structure is simple, but thermal conductivity decreases due to reaction and void formation
Solution Approach 1:
The patent introduces an optional copper layer as an intermediary between the barrier metal layer and die attach material layer. This intermediate layer prevents direct contact and unwanted reactions during phase transition, while maintaining excellent thermal conductivity at the die attach interface
Solution Approach 2:
The patent creates a composite metallization stack with multiple functional layers. The barrier layer provides diffusion protection, the copper intermediate layer provides thermal conduction and prevents reactions, and the die attach material provides bonding. This composite structure optimizes thermal conductivity while maintaining structural simplicity
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 thermal conductivity and bonding strength of the die attach interface, improving the reliability and yield of semiconductor devices by reducing void formation and delamination issues, particularly for SiC-based devices attached to copper-based packages.
Implementation Method 1
performing a sputtering process to deposit a die attach material layer on the second surface of the SiC substrate using a sputter gas comprising at least one of krypton (Kr), xenon (Xe), or radon (Rn)
Implementation Method 2
performing a die attach operation comprising a phase transition of the die attach material layer to attach the second surface of the SiC substrate to a surface of a package substrate
Data Source
AI summary
A semiconductor device package includes a package substrate having a die attach region, a silicon carbide (SiC) substrate having a first surface including a semiconductor device layer thereon and a second surface that is opposite the first surface, and a die attach metal stack. The die attach metal stack includes a sputtered die attach material layer that attaches the second surface of the SiC substrate to the die attach region of the package substrate, where the sputtered die attach material layer comprises a void percent of about 15% or less. The sputtered die attach material layer may be formed using a sputter gas including at least one of krypton (Kr), xenon (Xe), or radon (Rn). The die attach metal stack may further include a metal interlayer that prevent contacts with a first barrier metal layer during a phase transition of the die attach material layer.