Thinned GaN Module Packaging for Thermal and RF Performance
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Solution Overview
Problem
The commercialization of Gallium-Nitride (GaN) based FET devices is hindered by the high cost and limited availability of silicon carbide substrates, and silicon substrates are not suitable for radio frequency applications due to lattice constant mismatch and harmonic distortion issues.
Innovation Solution
A GaN based module design featuring a thinned switch die with an AlGaN barrier layer and a GaN buffer layer, encapsulated by mold compounds with high thermal conductivity and electrical resistivity, and a CMOS controller die, integrated on a substrate with connecting layers, to enhance electrical performance and reduce module size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GaN material is grown on SiC substrates, then thermal conductivity and lattice matching are improved, but substrate cost and availability deteriorate
Solution Approach 1:
The patent uses a silicon carbide (SiC) buffer layer as an intermediary between the silicon substrate and the GaN layer. This buffer layer mediates the interface between the two materials, providing the necessary thermal conductivity and lattice matching properties while allowing the use of inexpensive silicon substrates instead of expensive SiC substrates.
2Reliability
If GaN material is grown on SiC substrates, then thermal conductivity is improved, but substrate availability and scalability deteriorate
Solution Approach 1:
The SiC buffer layer acts as a mediator that enables the use of abundant, inexpensive silicon substrates while maintaining the thermal conductivity requirements for GaN device operation. This intermediary approach resolves the scarcity issue of SiC substrates by decoupling the substrate choice from the active GaN layer requirements.
3Ease of manufacture
If silicon substrates are used for GaN devices, then substrate cost is reduced, but harmonic distortion and RF performance deteriorate
Solution Approach 1:
The SiC buffer layer serves as an intermediary that prevents the silicon substrate from generating harmful harmonic distortion in RF applications. By placing the GaN active layer on the SiC buffer rather than directly on silicon, the patent eliminates the deleterious effects of silicon while retaining its cost advantages.
4Volume of moving object
If GaN layer is thinned to reduce module size, then module dimensions are reduced, but electrical performance and heat dissipation deteriorate
Solution Approach 1:
The patent addresses the heat dissipation challenge by improving thermal conductivity in the vertical dimension through the SiC buffer layer and enhanced thermal interface materials, allowing the GaN layer to be thinned horizontally without compromising overall thermal management. This dimensional approach enables size reduction while maintaining electrical performance.
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
The solution provides an economical and efficient GaN based module with improved electrical performance and reduced harmonic distortion, suitable for large volume commercial applications, including the mobile industry, by leveraging a cost-effective substrate and advanced packaging techniques.
Implementation Method 1
a lateral two-dimensional electron gas (2DEG) layer. Herein, the first mold compound resides over the top surface of the substrate body, surrounds the thinned switch die, and extends above a top surface of the thinned switch die to form an opening over the top surface of the thinned switch die.
Implementation Method 2
the 2DEG layer is realized at a heterojunction of the AlGaN barrier layer and the GaN buffer layer
Implementation Method 3
encapsulated by mold compounds with high thermal conductivity and electrical resistivity
Implementation Method 4
encapsulated by mold compounds with high thermal conductivity and electrical resistivity
Data Source
AI summary
The present disclosure relates to a Gallium-Nitride (GaN) based module, which includes a module substrate, a thinned switch die residing over the module substrate, a first mold compound, and a second mold compound. The thinned switch die includes an electrode region, a number of switch interconnects extending from a bottom surface of the electrode region to the module substrate, an aluminium gallium nitride (AlGaN) barrier layer over a top surface of the electrode region, a GaN buffer layer over the AlGaN barrier layer, and a lateral two-dimensional electron gas (2DEG) layer realized at a heterojunction of the AlGaN barrier layer and the GaN buffer layer. The first mold compound resides over the module substrate, surrounds the thinned switch die, and extends above a top surface of the thinned switch die to form an opening over the top surface of the thinned switch die. The second mold compound fills the opening.