Tin Solder Crystal Orientation for Strain and Electromigration
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Solution Overview
Problem
Tin-based solder layers in semiconductor devices experience anisotropic inelastic strain and electromigration, leading to deterioration due to temperature changes and electron flow, respectively, with existing orientations either exacerbating strain or migration issues.
Innovation Solution
The tin-based solder layer is formed with the C-axis of its crystals oriented at angles greater than 45 degrees in the central portion and less than or equal to 45 degrees or parallel in the peripheral portion relative to the substrate normal, using a heat transfer plate to control crystallization and reduce both inelastic strain and electromigration effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the C-axis of tin crystals is oriented parallel to the substrate normal, then inelastic strain due to temperature change is reduced, but electromigration deteriorates the solder layer
Solution Approach 1:
The patent applies different C-axis orientations in different regions of the solder layer. The central portion has C-axes oriented at angles greater than 45 degrees to reduce electromigration, while the peripheral portion has C-axes oriented at angles less than or equal to 45 degrees to reduce inelastic strain. This spatial differentiation of crystal orientation properties resolves the contradiction between the two opposing requirements.
2Reliability
If the C-axis of tin crystals is oriented perpendicular to the substrate normal, then electromigration is reduced, but inelastic strain due to temperature change increases
Solution Approach 1:
The patent implements regional differentiation where the peripheral portion of the solder layer has C-axes oriented at angles less than or equal to 45 degrees to the substrate normal. This local orientation minimizes inelastic strain in the peripheral region, while the central portion maintains angles greater than 45 degrees to address electromigration, thus resolving the contradiction through spatially varying crystal orientation.
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 configuration enhances the semiconductor device's resistance to both inelastic strain and electromigration, balancing current flow and stress direction to maintain structural integrity and prevent metal distribution non-uniformity.
Implementation Method 1
The tin-based solder layer includes a central portion and a peripheral portion. The C-axis at the central portion intersects the normal line at an angle larger than 45 degrees with respect to the normal line. The C-axis at the peripheral portion either intersects the normal line at an angle smaller than or equal to 45 degrees with respect to the normal line, or is parallel to the normal line.
Data Source
AI summary
A semiconductor device includes a substrate, a semiconductor element and a tin-based solder layer. The semiconductor element faces the substrate in a normal direction of the substrate. The normal direction corresponds to a normal line of the substrate. The tin-based solder layer joins the semiconductor element to the substrate. The tin-based solder layer a central portion and a peripheral portion surrounding the central portion. The tin-based solder layer has a tin crystal with a C-axis at each of the central portion and the peripheral portion. The C-axis at the central portion intersects the normal line at an angle larger than 45 degrees with respect to the normal line. The C-axis at the peripheral portion either intersects the normal line at an angle smaller than or equal to 45 degrees with respect to the normal line, or is parallel to the normal line.