Copper Pillar Interconnect Thermal Stability via Diffusion Barrier
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Solution Overview
Problem
Copper pillar interconnect structures in semiconductor devices are limited by temperature cycling, restricting their use to environments with limited temperature variations due to issues such as intermetallic compound formation and void creation at high temperatures.
Innovation Solution
A method involving the deposition of a copper pillar with a diffusion barrier layer that overhangs the pillar, preventing direct contact between the solder and copper, and featuring a stepped sidewall to enhance separation and protect against solder wetting, migration, and contamination, thereby improving the device's thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper pillar interconnect structures are used for electrical connection, then electrical connectivity is achieved, but thermal stability deteriorates due to intermetallic compound formation and void creation at high temperatures
Solution Approach 1:
A diffusion barrier layer is introduced as an intermediary between the copper pillar and solder structure. This barrier layer prevents direct contact between copper and solder, thereby preventing intermetallic compound formation and void creation that occur at high temperatures during temperature cycling.
Solution Approach 2:
The diffusion barrier layer is designed with a stepped sidewall profile that overhangs the copper pillar in the lateral dimension. This dimensional change creates a protective overhang that prevents solder wetting and migration onto the copper pillar sidewalls, adding a spatial dimension to the protection mechanism.
2Reliability
If diffusion barrier layer is formed to prevent intermetallic compound formation, then thermal stability is improved, but device complexity increases due to additional manufacturing steps
Solution Approach 1:
The formation of the diffusion barrier layer with stepped sidewall is merged with the existing copper pillar formation process. The barrier layer is deposited conformally over the copper pillar and then selectively removed, combining multiple functions (diffusion barrier, stepped profile creation, sidewall protection) into a integrated process sequence.
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 enhances the thermal stability of semiconductor devices, allowing them to withstand temperature cycling from -40°C to 150°C, reducing degradation and enabling use in critical applications like the automotive industry.
Implementation Method 1
A diffusion barrier layer is arranged between the copper pillar and the solder structure
Implementation Method 2
The photoresist layer is patterned to form an opening in the photoresist layer
Data Source
AI summary
A method of manufacturing a semiconductor device is described. The method includes depositing a photoresist layer over a semiconductor substrate. The photoresist layer is patterned to form an opening in the photoresist layer. A copper pillar is formed in the opening. A diffusion barrier layer is formed over the copper pillar and over a photoresist portion of the photoresist layer directly adjoining the opening. A solder structure is deposited over the diffusion barrier layer.