3D Die-on-Die Packaging Using a Silicon Thermal Sink
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Solution Overview
Problem
High-power low thermal conductivity dies in RF applications face challenges with heat dissipation due to the use of low thermal conductivity materials, and traditional metal heat sinks are not feasible in low-profile portable electronic devices, leading to high die temperatures and size constraints.
Innovation Solution
A 3D package design utilizing a silicon die as a thermal sink, where a first die with high thermal conductivity is stacked over one or more low thermal conductivity dies, with a substrate tie structure extending through the device region and substrate to enhance heat dissipation, and bump structures and a mold compound are used to encapsulate and connect the dies for efficient thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If metal heat sinks are used for heat extraction, then thermal performance is improved, but package height increases significantly
Solution Approach 1:
The patent embeds the heat extraction function within the BEOL structure itself, nesting thermal management capabilities inside the existing package layers rather than adding external heat sinks. The BEOL is configured to conduct heat away from the die, utilizing the existing back-end-of-line structure as the heat extraction pathway.
Solution Approach 2:
The patent transitions from vertical heat extraction (requiring tall metal heat sinks extending upward from the die) to lateral heat extraction through the BEOL structure. By routing heat conduction paths horizontally through the back-end-of-line layers, the solution achieves effective thermal management without increasing package height.
2Power
If low thermal conductivity materials are used for high-power RF dies, then device performance is achieved, but heat dissipation capability deteriorates
Solution Approach 1:
The patent segments the heat dissipation function from the active device region, placing high thermal conductivity heat extraction structures in the BEOL portion separate from the low thermal conductivity RF die material. This allows the die to maintain its low thermal conductivity for RF performance while the BEOL provides dedicated heat extraction pathways.
Solution Approach 2:
The BEOL structure serves as an intermediary between the low thermal conductivity RF die and the heat sink. It receives heat from the die through thermal conduction and transports it laterally to external heat dissipation structures, bridging the thermal management gap created by using low thermal conductivity materials for high-power RF devices.
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 design provides enhanced thermal performance and reduced package size, effectively managing heat dissipation in high-power low thermal conductivity dies, even in low-profile devices, by creating a short thermal resistance path and utilizing high thermal conductivity materials.
Implementation Method 1
heat generated by the second device region can propagate through the BEOL portion and the substrate tie structure, and radiate out of the first substrate
Implementation Method 2
heat generated by the second device region can propagate through the BEOL portion and the substrate tie structure, and radiate out of the first substrate
Implementation Method 3
create an efficient (relatively short) low thermal resistance path for high-power low thermal conductivity dies
Data Source
AI summary
The present disclosure relates to a three-dimensional (3D) package that has a die-on-die configuration, and includes a first die and at least one second die deposed underneath the first die. The first die includes a back-end-of-line (BEOL) portion, a device region over the BEOL portion, a substrate over the device region, and a substrate tie structure that extends through the device region and at least extends into the substrate. The substrate and the substrate tie structure each has a high thermal conductivity higher than 50 W/mK. The at least one second die is configured to be coupled to the BEOL portion of the first die, such that heat generated by the second die can propagate through the BEOL portion and the substrate tie structure, and radiate out of the first substrate.