Vertical Semiconductor Electrode Structure for Crack-Resistant Bonding
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Solution Overview
Problem
Existing semiconductor modules face issues with bonding reliability and thermal stress resistance, particularly in high-temperature operations, due to the use of gold layers that are costly and prone to cracking, leading to reduced heat dissipation and failure.
Innovation Solution
Incorporating a lowermost layer of copper and gold alloy in the lower electrode, along with a bonding layer composed of copper, tin, and nickel, which enhances bonding reliability and thermal stress resistance by suppressing crack formation and maintaining solder wettability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gold layer is used in the lower electrode, then bonding reliability is improved, but cost increases and crack resistance deteriorates
Solution Approach 1:
The patent applies composite materials by creating a multi-layer lower electrode structure consisting of a Cu-Ni alloy layer, a Cu-Sn alloy layer, and a Cu-Au alloy layer. Each layer serves specific functions: the Cu-Ni layer provides base adhesion, the Cu-Sn layer enhances bonding reliability and solder wettability, and the Cu-Au layer provides thermal stress resistance. This composite structure resolves the contradiction by combining materials with complementary properties rather than using a single gold layer.
Solution Approach 2:
The patent applies local quality by optimizing the composition and thickness of each layer in the multi-layer structure. The Cu-Sn alloy layer is specifically designed with controlled Sn content (1-20 at%) and thickness (0.1-5 μm) to provide localized bonding enhancement at the interface, while the Cu-Au alloy layer (0.1-5 μm thick) provides localized thermal stress resistance. This localized optimization allows each layer to address specific problems without requiring extensive gold throughout the entire structure.
2Reliability
If a gold layer is used in the lower electrode, then bonding reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent reduces gold content by replacing a substantial portion with copper-based alloy layers. The Cu-Ni alloy layer (Ni: 1-20 at%, thickness: 0.1-5 μm) and Cu-Sn alloy layer (Sn: 1-20 at%, thickness: 0.1-5 μm) provide bonding functionality that would otherwise require gold, thereby reducing the quantity and cost of gold while maintaining or improving bonding reliability.
Solution Approach 2:
The patent uses cheaper copper-based alloy materials (Cu-Ni, Cu-Sn) as替代 materials for expensive gold in the lower electrode structure. These copper-based layers provide the necessary bonding and thermal stress resistance functions at a lower cost, effectively replacing expensive materials with more economical alternatives that achieve the same or better performance.
3Ease of manufacture
If existing bonding structures are used, then manufacturing is simplified, but thermal stress resistance deteriorates in high-temperature operations
Solution Approach 1:
The patent applies composite materials by creating a multi-layer lower electrode structure consisting of a Cu-Ni alloy layer, a Cu-Sn alloy layer, and a Cu-Au alloy layer. Each layer serves specific functions: the Cu-Ni layer provides base adhesion, the Cu-Sn alloy layer enhances bonding reliability and solder wettability, and the Cu-Au alloy layer provides thermal stress resistance. This composite structure resolves the contradiction by combining materials with complementary properties rather than using a single gold layer.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the composition and thickness parameters of each layer. The Cu-Sn alloy layer has Sn content controlled at 1-20 at% and thickness at 0.1-5 μm, while the Cu-Au alloy layer has Au content at 1-20 at% and thickness at 0.1-5 μm. These parameter optimizations enhance thermal stress resistance through controlled material properties while maintaining compatibility with existing manufacturing processes.
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 solution improves the dTjP/C withstand value, ensuring enhanced bonding reliability and reduced solder erosion, thereby supporting high-temperature operations and miniaturization in semiconductor modules.
Implementation Method 1
a bonding layer composed of copper, tin, and nickel
Implementation Method 2
a bonding layer composed of copper, tin, and nickel, which enhances bonding reliability
Implementation Method 3
enhances bonding reliability and thermal stress resistance by suppressing crack formation
Implementation Method 4
maintaining solder wettability
Data Source
AI summary
There is provided a vertical device including: a semiconductor substrate which has an upper surface and a lower surface; and a lower electrode which is provided on the entire lower surface of the semiconductor substrate, in which the lower electrode contains copper. The lower electrode may have a lowermost layer which is exposed at a surface that is farthest away from the lower surface of the semiconductor substrate, the lowermost layer may contain copper, a ratio of copper in the lowermost layer may be 50 wt% or more and 90 wt% or less, and a thickness of the lowermost layer may be 0.2 μm or more and 0.8 μm or less.