Stacked IC Die Signal Routing via Controllable Impedance
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Solution Overview
Problem
Existing techniques for routing signals to and from stacked integrated circuit dies face challenges, including the need for separate signal application to each die and the inefficiency of using an insulative redistribution layer, which increases signal path lengths and is economically undesirable.
Innovation Solution
The use of controllable impedance devices to selectively connect bonding pads on stacked dies, allowing signals to be routed directly between identical dies by configuring them as either upper or lower dies during fabrication, thereby eliminating the need for separate redistribution layers and ensuring synchronized signal response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an insulative redistribution layer is used to route signals between stacked dies, then signal routing is enabled, but signal path length increases and manufacturing cost increases
Solution Approach 1:
The patent extracts and eliminates the insulative redistribution layer from the signal path by establishing direct bonding pad-to-bonding pad connections between stacked dies. This removes the intermediate routing layer that was causing increased signal path length and manufacturing complexity, while still enabling signal routing through direct vertical connections.
Solution Approach 2:
The patent uses controllable impedance devices as intermediaries between bonding pads to enable signal routing without requiring an insulative redistribution layer. These devices provide the necessary signal isolation and routing control directly at the bonding interface, eliminating the need for the problematic intermediate layer.
2Ease of operation
If separate bonding pads are fabricated on each die for individual signal routing, then signal isolation between dies is achieved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies dynamics by making the impedance devices controllable and reconfigurable. The impedance devices can dynamically switch between connected and isolated states based on which die (upper or lower) is active, providing individual signal routing capability without requiring permanently separate bonding pad configurations for each die.
Solution Approach 2:
The patent makes each bonding pad universal by enabling it to serve both its own die and the opposing die through the controllable impedance devices. The same bonding pad structure and impedance device can route signals to either the upper or lower die depending on the operational state, eliminating the need for dedicated separate bonding pads for each die.
3Ease of manufacture
If identical dies are stacked without position-specific configuration, then manufacturing cost decreases, but signal routing to specific dies becomes difficult
Solution Approach 1:
The patent uses dynamic control of the impedance devices to enable selective signal routing to either the upper or lower die. The impedance devices can be controlled to connect bonding pads to the appropriate die based on operational requirements, allowing identical dies to be selectively activated without requiring position-specific die configurations.
Solution Approach 2:
The patent enables the stacked die system to self-configure for signal routing. The controllable impedance devices automatically route signals to the appropriate die based on the operational state, eliminating the need for external complex routing configurations or position-specific die modifications.
Data Source
AI summary
Signals are routed to and from identical stacked integrated circuit dies by selectively coupling first and second bonding pads on each of the dies to respective circuits fabricated on the dies through respective transistors. The transistors connected to the first bonding pads of an upper die are made conductive while the transistors connected to the second bonding pads of the upper die are made non-conductive. The transistors connected to the second bonding pads of a lower die are made conductive while the transistors connected to the first bonding pads of the lower die are made non-conductive. The second bonding pads of the upper die are connected to the second bonding pads of the lower die through wafer interconnects extending through the upper die. Signals are routed to and from the circuits on the first and second dies through the first and second bonding pads, respectively.