Zinc-Based Semiconductor Bonding Material with Diffusion Barrier
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Solution Overview
Problem
Conventional semiconductor device bonding materials with low melting points are inadequate for next-generation power semiconductors, such as GaN and SiC, due to inferior thermal stability, especially when exposed to high temperatures above 200°C.
Innovation Solution
A semiconductor device bonding material with zinc as the main component, featuring a coating layer with a nitride or carbide barrier layer and a noble metal protective layer to prevent diffusion and reaction, ensuring high thermal stability and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead-based bonding material is used for die attachment, then bonding process is simple and cost-effective, but thermal stability is insufficient for high temperature applications above 200°C
Solution Approach 1:
The patent changes the material parameter from lead-based to zinc-based bonding material, which has a higher melting point (420°C) compared to conventional lead-based materials. This parameter change enables the bonding material to maintain thermal stability at high temperatures above 200°C, resolving the contradiction between reliability and ease of manufacture by selecting a different material class that inherently possesses the required thermal properties.
Solution Approach 2:
The patent employs a composite coating structure consisting of a barrier layer (made of materials like TiN, TaN, W, Mo, or their nitrides/carbides) and a protective layer (made of noble metals like Au, Ag, or Pd). This composite material approach prevents zinc diffusion into the substrate and semiconductor member, while maintaining bonding strength and thermal stability, thus enabling reliable high-temperature operation without sacrificing manufacturability.
2Reliability
If zinc-based bonding material is used to improve thermal stability, then thermal fatigue resistance increases, but diffusion and reaction with substrate/semiconductor member may occur
Solution Approach 1:
The patent introduces a barrier layer as an intermediary between the zinc-based bonding material and the substrate/semiconductor member. This barrier layer (composed of materials such as TiN, TaN, W, Mo, or their nitrides and carbides) acts as a diffusion barrier that prevents zinc from reacting with the substrate or semiconductor member, while still allowing the bonding material to maintain its thermal fatigue resistance properties. The protective layer of noble metals further protects the barrier layer from oxidation and degradation.
3Strength
If coating layer is added to prevent diffusion, then bonding strength is maintained, but device structure becomes more complex
Solution Approach 1:
The patent uses a composite coating structure with a barrier layer and a protective layer, where each layer has a specific function. The barrier layer prevents zinc diffusion, while the protective layer prevents oxidation and provides additional mechanical protection. This composite approach maintains bonding strength through proper material selection and thickness control, while the layered structure is integrated into the existing manufacturing process, minimizing the impact on device complexity.
Solution Approach 2:
The coating layers are applied locally only at the bonding interface between the semiconductor member and substrate, rather than throughout the entire device. The barrier layer thickness is optimized (typically 10-100 nm) to provide sufficient diffusion protection without excessive complexity. This localized application maintains bonding strength where needed while avoiding unnecessary complexity in other parts of the device.
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 zinc-based bonding material provides excellent thermal fatigue resistance, maintaining bonding strength and preventing reaction layer formation, enabling semiconductor devices to withstand temperature cycles up to 300°C.
Implementation Method 1
a coating layer to prevent diffusion of the semiconductor device bonding material is provided on at least one of the surface of the substrate and the surface of the semiconductor member
Implementation Method 2
noble metals (especially, Au) can improve the wettability of the semiconductor device bonding material with respect to the coating layer
Data Source
AI summary
In a semiconductor device 100 according to the present invention in which a semiconductor member 120 is stacked on a substrate 110, the semiconductor member 120 and the substrate 110 are bonded together by means of a semiconductor device bonding material 130 of which main component is zinc. Further, a coating layer to prevent diffusion of the semiconductor device bonding material 130 is provided on at least one of the surface of the substrate 110 and the surface of the semiconductor member 120. In addition, the coating layer 140 is configured such that a barrier layer 141 composed of nitride, carbide, or carbonitride and a protective layer 142 composed of a noble metal are stacked. Further, the nitride, the carbide, or the carbonitride composing the barrier layer 141 is selected so as to have free energy smaller than that of a material composing an insulating layer 111 provided in the substrate 110.