Shared ScAlN HEMT-Resonator Structure for Crack-Resistant RF Integration

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Solution Overview

Problem

Piezoelectric resonator devices face challenges in achieving high-quality single crystal piezoelectric layers, particularly at 5G frequencies, due to thermal issues and stress-induced cracking.

Innovation Solution

The integration of a High Electron Mobility Transistor (HEMT) device with a piezoelectric resonator on a shared ScAlN layer, which provides strain balancing and acts as both a buffer layer for the HEMT and a piezoelectric layer for the resonator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a piezoelectric material layer is grown on a substrate to form a resonator, then the resonator can function at RF frequencies, but thermal issues and stress-induced cracking occur that degrade device reliability

Engineering Contradiction:

Improvedevice reliabilityVSAvoidstress-induced cracking

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent employs a composite material structure consisting of multiple layers including piezoelectric material layers (such as AlN or ScAlN), buffer layers (such as GaN or AlGaN), and substrate layers. This composite structure allows the piezoelectric layer to function while the buffer layers provide stress management and thermal stability, preventing cracking and improving overall device reliability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent modifies physical parameters of the piezoelectric structure, including layer thicknesses, material composition ratios (such as Scandium content in ScAlN), and growth conditions. By optimizing these parameters, the patent achieves stress balancing in the piezoelectric layer, reducing thermal stress and preventing cracking while maintaining piezoelectric performance for RF resonance.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If a piezoelectric layer is used for both buffer and resonator functions, then device integration is improved, but achieving high-quality single crystal growth becomes more difficult

Engineering Contradiction:

Improvedevice integrationVSAvoidsingle crystal growth quality

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent divides the piezoelectric structure into functionally distinct segments: a buffer region where the piezoelectric material serves as a buffer layer for the HEMT, and a resonator region where the same material serves as the piezoelectric resonator. This segmentation allows each region to be optimized for its specific function while using the same material system, maintaining single crystal quality through controlled epitaxial growth.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent makes the piezoelectric material layer multi-functional by having it serve dual purposes: as a buffer layer for the HEMT device and as the active piezoelectric resonator. This universal use of the same high-quality single crystal piezoelectric layer for both functions improves device integration and reduces manufacturing complexity while maintaining crystal quality through precise growth control.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 integration enhances the performance of both devices by reducing stress-induced cracking in the piezoelectric layer and providing a stable structure for the HEMT channel layer, thereby improving the overall frequency response and reliability of the devices.

Implementation Method 1

The integration of a High Electron Mobility Transistor (HEMT) device with a piezoelectric resonator on a shared ScAlN layer, which provides strain balancing

Methodology Applied

Scientific EffectStrain balancing:

Implementation Method 2

RF piezoelectric resonator device can be on the substrate including the ScAlN layer sandwiched between a top electrode and a bottom electrode of the RF piezoelectric resonator device to provide a piezoelectric resonator

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS12289087B2RF acoustic wave resonators integrated with high electron mobility transistors including a shared piezoelectric/buffer layer

Publication Date: 2025.04.29 AKOUSTIS TECHNOLOGIES CORP

AI summary

An RF integrated circuit device can includes a substrate and a High Electron Mobility Transistor (HEMT) device on the substrate including a ScAlN layer configured to provide a buffer layer of the HEMT device to confine formation of a 2DEG channel region of the HEMT device. An RF piezoelectric resonator device can be on the substrate including the ScAlN layer sandwiched between a top electrode and a bottom electrode of the RF piezoelectric resonator device to provide a piezoelectric resonator for the RF piezoelectric resonator device.