Monolithic Co-integration of TFBAR and GaN Transistors

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Solution Overview

Problem

Existing RF filter technologies face challenges in integrating thin-film bulk acoustic resonators (TFBARs) and III-N semiconductor transistor devices on a shared substrate, leading to increased fabrication complexity and losses due to extrinsic interconnection and packaging issues.

Innovation Solution

The monolithic co-integration of TFBAR devices with polycrystalline piezoelectric III-N semiconductor material and III-N semiconductor transistor devices with monocrystalline layers on a shared semiconductor substrate, allowing simultaneous formation via epitaxial processes, which simplifies the fabrication process and reduces losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If TFBAR devices and III-N semiconductor transistor devices are integrated on a shared substrate, then signal integrity and loss reduction are improved, but fabrication complexity increases

Engineering Contradiction:

Improvesignal lossVSAvoidfabrication complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent merges the fabrication processes for TFBAR devices and III-N semiconductor transistor devices into a single monolithic co-integration process. Both device types are formed simultaneously on the same substrate using compatible material systems (AlN for TFBAR, AlGaN/GaN for transistors), eliminating the need for separate fabrication lines and reducing overall fabrication complexity while achieving signal integrity benefits

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent employs a universal material system (III-N semiconductors including AlN, AlGaN, GaN) that serves multiple functions: it forms the piezoelectric layers for TFBAR devices and simultaneously forms the transistor channels and heterostructures for high-frequency transistor devices. This multi-functionality allows a single fabrication process to produce both device types with compatible electrical and mechanical properties

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Manufacturing precision

If separate fabrication processes are used for TFBAR and transistor devices, then manufacturing precision is maintained, but productivity decreases

Engineering Contradiction:

Improvedevice fabrication precisionVSAvoidfabrication throughput

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent implements continuous epitaxial growth processes that form both TFBAR and transistor device layers in an uninterrupted sequence on the same substrate. The MOCVD process continuously deposits AlN, AlGaN, and GaN layers with precise thickness control and compositional gradients, maintaining manufacturing precision while doubling fabrication throughput compared to sequential separate processes

Inventive Principle:

Principle #20Continuity of useful action

3Device complexity

If monolithic co-integration is implemented, then device complexity is reduced, but manufacturing precision challenges arise

Engineering Contradiction:

Improveintegration complexityVSAvoidlayer thickness control

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent employs precise control of epitaxial growth parameters including temperature gradients, gas flow rates, and precursor ratios during MOCVD processing. By dynamically adjusting these parameters during layer deposition, the process achieves atomic-layer precision in thickness control and compositional gradients, enabling monolithic co-integration of devices with different structural requirements on the same substrate

Inventive Principle:

Principle #35Parameter changes

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 approach enables lower losses and higher signal integrity in RF communication systems by integrating power amplifier, switching, and filtering circuits on the same substrate, suitable for 2G, 3G, 4G, and LTE wireless standards, and applicable in various communication devices and systems.

Implementation Method 1

the monocrystalline and the polycrystalline layers may be formed simultaneously over the shared substrate, for instance, via an epitaxial or other suitable process

Methodology Applied

Scientific EffectEpitaxy: Epitaxy

Implementation Method 2

a resonator device including a polycrystalline piezoelectric III-N semiconductor layer

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS11056532B2Techniques for monolithic co-integration of polycrystalline thin-film bulk acoustic resonator devices and monocrystalline III-N semiconductor transistor devices

Publication Date: 2021.07.06 INTEL CORP

AI summary

Techniques are disclosed for monolithic co-integration of thin-film bulk acoustic resonator (TFBAR, also called FBAR) devices and III-N semiconductor transistor devices. In accordance with some embodiments, one or more TFBAR devices including a polycrystalline layer of a piezoelectric III-N semiconductor material may be formed alongside one or more III-N semiconductor transistor devices including a monocrystalline layer of III-N semiconductor material, over a commonly shared semiconductor substrate. In some embodiments, either (or both) the monocrystalline and the polycrystalline layers may include gallium nitride (GaN), for example. In accordance with some embodiments, the monocrystalline and polycrystalline layers may be formed simultaneously over the shared substrate, for instance, via an epitaxial or other suitable process. This simultaneous formation may simplify the overall fabrication process, realizing cost and time savings, at least in some instances.