TSV Bulbous Tips for Electromigration and IMC Cracking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Through-silicon via (TSV) joints in integrated circuits face limitations due to low electromigration current density and stress-induced failures, particularly when using solder-mediated joints, which restrict the area for TSV tips and lead to inter-metallic compound (IMC) formation causing cracking of the outer dielectric sleeve.
Innovation Solution
The formation of bulbous distal tip ends on TSV tips using a combination of two non-solder metal layers, one acting as an IMC block and current spreader, significantly increasing the cross-sectional area by at least 25% and delaying IMC formation with Sn-based solder, thereby reducing current density and preventing IMC-induced failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder-mediated joints are used for TSV connections, then the TSV tips can be bonded to other dies, but the electromigration current density is limited due to the low EM current limit of solder
Solution Approach 1:
The patent applies composite materials by creating a bulbous distal tip end composed of multiple metal layers (first metal layer and second metal layer) that combines the advantages of different materials. This composite structure provides both mechanical bonding capability and high electromigration performance, overcoming the limitations of single-material solder joints.
Solution Approach 2:
The patent changes the physical parameters of the TSV tip by forming a bulbous distal tip end with increased cross-sectional area (≥25% more than the TSV body). This parameter change increases the current-carrying capacity and reduces current density, thereby improving electromigration performance without changing the fundamental solder-mediated bonding mechanism.
2Reliability
If additional TSVs are formed in parallel to reduce current density, then electromigration performance improves, but die area increases and manufacturing complexity increases
Solution Approach 1:
Instead of increasing the number of TSVs, the patent changes the geometric parameter of the existing TSV tip by forming a bulbous distal tip end. This increases the effective cross-sectional area for current flow by at least 25%, reducing current density and improving electromigration performance without occupying additional die area.
3Ease of manufacture
If conventional TSV tips are used, then manufacturing is simpler, but IMC formation causes cracking of the outer dielectric sleeve
Solution Approach 1:
The patent introduces an intermediary structure (bulbous distal tip end with multiple metal layers) between the TSV inner metal core and the solder joint. This intermediary structure acts as a barrier that delays IMC formation and prevents cracking of the outer dielectric sleeve, while still allowing solder-mediated bonding to occur.
Solution Approach 2:
The bulbous distal tip end structure is formed in advance before the final solder bonding process. This preliminary action creates a protective structure that prevents IMC-induced cracking before it can occur during subsequent processing or operation, rather than attempting to fix the problem after damage occurs.
4Reliability
If the TSV area is increased to improve EM performance, then current density decreases, but the TSV area is limited by die area restrictions and stress on TSV layers
Solution Approach 1:
The patent changes the geometric parameter of the TSV tip by forming a bulbous distal tip end that increases the cross-sectional area by at least 25%. This localized parameter change occurs at the tip region where it is most needed for current distribution, without increasing the overall TSV footprint or violating die area restrictions.
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 solution enhances electromigration performance without adding cost or cycle time, delays IMC formation, and prevents cracking of the outer dielectric sleeve, effectively addressing the limitations of conventional TSV joints.
Implementation Method 1
plating a first metal layer exclusive of solder on a distal portion of a protruding TSV tip of a TSV that comprises an outer dielectric sleeve and an inner metal core, and plating a second metal layer exclusive of solder that is different from the first metal layer on the first metal layer
Data Source
AI summary
A through substrate via (TSV) die includes a plurality of TSVs including an outer dielectric sleeve, an inner metal core and protruding TSV tips including sidewalls that emerge from the TSV die. A passivation layer lateral to protruding TSV tips is on a portion of the sidewalls of protruding TSV tips. The passivation layers is absent from a distal portion of protruding TSV tips to provide an exposed portion of the inner metal core. The TSV tips include bulbous distal tip ends which cover a portion of the TSV sidewalls, are over a topmost surface of the outer dielectric sleeve, and have a maximum cross sectional area that is ≧25% more as compared to a cross sectional area of the protruding TSV tips below the bulbous distal tip ends.