Die Stacking with Annular Via Recessed Socket
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Solution Overview
Problem
The miniaturization trend in microelectronics packaging challenges the efficient integration of multiple dies within a single package while maintaining high-speed and reliable interfaces, as existing methods struggle to minimize die real estate and ensure stable alignment and bonding.
Innovation Solution
The method involves forming conductive annular vias with recessed conductive sockets and conductive pillars to create a stable interlocking feature for die stacking, allowing for near-zero bond-line die stacking and enhanced alignment stability through the use of conductive materials like copper and under bump metal (UBM) alloys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional die stacking methods are used, then multiple dies can be integrated in a single package, but alignment stability and bonding reliability are insufficient
Solution Approach 1:
The via structure is segmented into multiple functional zones: an annular via body providing mechanical support, a recessed portion creating a socket for interlocking, and a conductive filling material providing electrical connection. This segmentation allows each zone to optimize its function, with the recessed socket specifically addressing alignment stability while maintaining bonding reliability.
Solution Approach 2:
The recessed socket structure嵌套 within the annular via creates a nested configuration where the conductive filling material is nested within the recessed portion, which is itself nested within the annular via structure. This nesting provides mechanical interlocking that enhances alignment stability during die stacking while ensuring reliable bonding.
2Area of stationary object
If die real estate is minimized for miniaturization, then package size is reduced, but alignment precision and bonding stability deteriorate
Solution Approach 1:
The solution moves from two-dimensional planar alignment to three-dimensional interlocking alignment. The recessed socket creates a vertical dimension for mechanical interlocking, allowing precise alignment to be achieved through depth-based engagement rather than relying solely on surface-level positioning. This enables miniaturization while maintaining alignment precision.
Solution Approach 2:
The via structure parameters are optimized with specific dimensional relationships: the recessed portion depth, annular via diameter, and conductive material dimensions are carefully controlled. These parameter changes create a geometric constraint system that maintains alignment precision even as overall die size is reduced for miniaturization.
3Reliability
If conventional via structures are used, then manufacturing is simpler, but alignment stability and bonding strength are insufficient
Solution Approach 1:
The recessed socket structure is formed preliminarily within the annular via before die stacking. This preliminary action creates a pre-configured interlocking mechanism that guides die alignment and ensures bonding stability from the outset, rather than requiring complex post-assembly adjustments or additional bonding steps.
Data Source
AI summary
A die stack including a die having an annular via with a recessed conductive socket and methods of forming the die stack provide a structure for use in a variety of electronic systems. In an embodiment, a die stack includes a conductive pillar on the top of a die inserted into the recessed conductive socket of another die.