TSV Liner Recess for Uniform Current Distribution
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Solution Overview
Problem
The small diameter of through silicon vias (TSVs) leads to non-uniform current distribution and current crowding at the interface with the glue layer, causing electromagnetic failures and the formation of hillocks and voids.
Innovation Solution
The TSVs are formed with a liner and a passivation layer, which are recessed to increase the surface area at the interface, allowing for a more uniform current distribution and reducing the formation of voids and hillocks by using a conductive interface layer over the recessed passivation and liner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the TSV diameter is reduced to increase integration density, then the number of connections per unit area increases, but current crowding occurs at the interface causing electromagnetic failures and void formation
Solution Approach 1:
The patent transitions from a two-dimensional circular interface to a three-dimensional annular ring interface by adding a protrusion structure. This dimensional change increases the effective contact area from a single point to a ring-shaped region, distributing current more uniformly across the interface between the TSV and glue layer.
Solution Approach 2:
The interface between the TSV and glue layer is segmented into multiple contact regions around the circumference of the TSV. The protrusion creates several discrete contact points distributed angularly around the TSV base, which divides the current flow path and reduces crowding at any single location.
2Area of stationary object
If the TSV diameter is reduced to achieve finer pitch, then more vias can be packed in the same area, but the current density increases causing electromagnetic failures
Solution Approach 1:
By adding vertical protrusion to the TSV structure, the patent creates an extended interface area that compensates for the reduced horizontal diameter. The annular ring contact area provides sufficient current carrying capacity even when the TSV pitch is reduced, preventing electromagnetic failures.
Solution Approach 2:
The protrusion structure concentrates the current distribution enhancement at the critical TSV-glue interface region. By locally modifying the geometry at the via base with an annular ring protrusion, the patent addresses the current density issue specifically where it occurs without affecting the overall TSV dimensions or pitch.
3Productivity
If the TSV diameter is reduced to increase connection density, then more electrical connections are possible, but voids and hillocks form at the interface
Solution Approach 1:
The protrusion structure adds vertical dimension to the TSV interface, creating an annular ring contact area that is more tolerant to manufacturing variations. This extended interface geometry provides a larger margin for error in the formation process, reducing void and hillock formation.
Solution Approach 2:
The protrusion structure is formed in advance during TSV fabrication, creating a pre-engineered stress distribution pattern. This preliminary geometric modification prevents stress concentration that would otherwise lead to void and hillock formation during subsequent processing steps.
Data Source
AI summary
A device includes a through substrate via (TSV) extending through a device substrate. The TSV includes a first conductive material having a sidewall, a protruding end of the TSV protruding from a second side of the device substrate. A liner covers the sidewall of the first conductive material from a below the top surface of the protruding end of the TSV to an opposite end of the TSV. A passivation layer is disposed over the second side of the device substrate and over a portion of the liner disposed on the protruding end of the TSV, the passivation layer having a stair-step surface extending away from the TSV. A conductive interface layer is disposed over the passivation layer, the sidewall of the first conductive material, and the top surface of the protruding end of the TSV. A second conductive material is disposed over the first conductive material.