Backside TSV Connection via Redistribution Lines
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Solution Overview
Problem
The existing through-silicon via (TSV) bonding process is limited by the need for large pitch between TSVs, restricting their location and increasing interconnection complexity, which leads to increased circuit RC delay and power consumption in two-dimensional integrated circuits.
Innovation Solution
A novel backside connection structure is developed, featuring a conductive via penetrating the semiconductor substrate with a redistribution line (RDL) and nickel layer on the backside, allowing for improved bonding and increased standoff between stacked dies, eliminating the need for copper pads and eutectic bonds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional TSV bonding is used to connect dies, then electrical connection between dies is achieved, but large pitch between TSVs is required which restricts TSV locations and increases device complexity
Solution Approach 1:
The patent introduces redistribution lines (RDLs) that route signals laterally on the backside of the die, transforming the vertical connection constraint into a two-dimensional routing problem. This allows TSVs to be positioned more flexibly while maintaining electrical connectivity through the RDL network, thereby reducing interconnection complexity without compromising electrical connection reliability.
Solution Approach 2:
The RDL acts as an intermediary between the TSV and the bond pad, decoupling the location of the TSV from the location of the bonding interface. This mediator allows the TSV to be positioned optimally for electrical connection while the RDL routes the signal to the appropriate bond pad location, reducing overall device complexity.
2Ease of manufacture
If TSV pitch is increased to allow solder ball placement, then bonding is enabled, but the distance between TSVs must be large which increases interconnection length and RC delay
Solution Approach 1:
By introducing the RDL layer, the patent separates the bonding function from the vertical TSV connection. The RDL allows signals to be redistributed laterally, enabling shorter effective interconnection paths between functional blocks while maintaining the larger pitch required for solder ball placement, thus reducing RC delay and power consumption.
Solution Approach 2:
The interconnection path is segmented into two parts: the vertical TSV connection and the lateral RDL routing. This segmentation allows optimization of each part independently - the TSV can be spaced for reliable bonding while the RDL provides efficient signal routing, reducing overall interconnection length and power consumption.
3Reliability
If nickel layer thickness is increased to prevent underfill intrusion, then bonding reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent specifies a particular nickel layer thickness range (50-200 nm) that optimizes the balance between preventing underfill intrusion and maintaining manufacturing feasibility. This parameter optimization ensures bonding reliability while avoiding excessive manufacturing complexity associated with very thin or very thick nickel layers.
Solution Approach 2:
The use of a nickel layer as part of a composite interconnection structure (TSV + RDL + nickel barrier) provides both the electrical connection function and the underfill barrier function, integrating multiple requirements into a unified structure that does not significantly increase manufacturing complexity.
Data Source
AI summary
An integrated circuit structure includes a semiconductor substrate including a front side and a backside. A through-silicon via (TSV) penetrates the semiconductor substrate, and has a back end extending to the backside of the semiconductor substrate. A redistribution line (RDL) is over the backside of the semiconductor substrate and connected to the back end of the TSV. The integrated circuit structure further includes a passivation layer over the RDL; an opening in the passivation layer, wherein a portion of the RDL is exposed through the opening; and a nickel layer in the opening and contacting the RDL.