Semiconductor Solder Bump Barrier Layer for IMC Control
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Solution Overview
Problem
The formation of intermetallic compounds (IMCs) between solder bumps and under bump metallurgy (UBM) layers in semiconductor devices leads to residual stress and cracking, causing separation of solder bumps from electrodes due to phase changes during the reflow process.
Innovation Solution
A semiconductor device design incorporating a barrier layer with reduced wettability, such as an oxide layer containing nickel (Ni) or copper (Cu), is introduced on the UBM layer to prevent diffusion of the solder bump into the UBM layer, thereby minimizing the formation of IMCs and reducing stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a solder bump is formed on a UBM layer through reflow process, then bonding between solder bump and electrode is achieved, but intermetallic compound formation and residual stress cause cracks and separation
Solution Approach 1:
The UBM layer is divided into multiple layers with different materials (e.g., Cu layer and Ni layer) to segment the functions: the Cu layer provides bonding strength while the Ni layer prevents excessive IMC formation and reduces stress, thus resolving the contradiction between bonding strength and crack resistance
Solution Approach 2:
A composite UBM structure is created using multiple materials (Cu and Ni layers) where each material contributes different properties: Cu for strong bonding and Ni for stress reduction and IMC control, achieving both high bonding strength and crack resistance simultaneously
2Strength
If the UBM layer has high wettability to facilitate solder bonding, then bonding strength is improved, but IMC diffusion into the UBM layer increases causing stress and cracks
Solution Approach 1:
The UBM layer is segmented into a lower Cu layer for high wettability and bonding strength, and an upper Ni layer with lower wettability that controls IMC diffusion, thus achieving strong bonding while preventing harmful IMC penetration
Solution Approach 2:
The Ni layer acts as an intermediary between the Cu layer and the solder bump, mediating the interaction by allowing controlled IMC formation at the Ni-solder interface while preventing excessive diffusion into the Cu layer, thus maintaining bonding strength while reducing harmful effects
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 implementation of a barrier layer effectively prevents the diffusion of solder bumps into the UBM layer, reducing the occurrence of cracks and enhancing the bonding strength between the solder bumps and electrodes, thus improving the reliability of semiconductor devices.
Implementation Method 1
A formation of the IMC or the solder bump may be absent from the barrier layer... The barrier layer may have a lower level of wettability with respect to the IMC and the solder bump than a level of wettability with respect to the UBM layer
Implementation Method 2
The barrier layer may include an oxide layer containing at least one element of the UBM layer... substantially preventing the solder bump from being diffused into the second surface of the UBM layer
Data Source
AI summary
A semiconductor device includes a light emitting structure, and an interconnection bump including an under bump metallurgy (UBM) layer disposed on an electrode of at least one of the first and second conductivity-type semiconductor layers, and having a first surface disposed opposite to a surface of the electrode and a second surface extending from an edge of the first surface to be connected to the electrode, an intermetallic compound (IMC) disposed on the first surface of the UBM layer, a solder bump bonded to the UBM layer with the IMC therebetween, and a barrier layer disposed on the second surface of the UBM layer and substantially preventing the solder bump from being diffused into the second surface of the UBM layer.