GaN HEMT Fin-Width Integration for Threshold Voltage Control

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Solution Overview

Problem

Current technologies face challenges in fabricating reliable Enhancement-mode (E-mode) AlGaN/GaN high-electron-mobility transistors (HEMTs) due to issues with gate-leakage current and hysteresis, limiting the integration of E-mode and Depletion-mode (D-mode) HEMTs for high-power and low-power applications.

Innovation Solution

The method involves forming trenches and fins in semiconductor layers with varying widths to control the threshold voltage, allowing for the monolithic integration of E-mode and D-mode AlGaN/GaN HEMTs without additional fabrication steps or surface damage, enabling the creation of devices with different threshold voltages for E-mode and D-mode operations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional fabrication methods are used for enhancement-mode HEMTs, then device structure is simple, but gate-leakage current increases and hysteresis occurs reducing reliability

Engineering Contradiction:

Improvegate-leakage current and hysteresis controlVSAvoidfabrication process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by creating fins with different widths within the same semiconductor layer. Specifically, first fins have a first width and second fins have a second width that is less than the first width. This local variation in fin geometry enables different threshold voltages for different HEMTs on the same wafer, allowing enhancement-mode devices to achieve reliable operation without complex additional fabrication steps.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If depletion-mode HEMTs are used for all devices, then fabrication is straightforward, but integration of both depletion-mode and enhancement-mode HEMTs is not achieved

Engineering Contradiction:

Improveintegration of E-mode and D-mode HEMTsVSAvoidfin width control precision

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent implements parameter changes by varying the fin width parameter across different device regions. First fins have a first width while second fins have a second width that is less than the first width. This parameter variation, achieved through standard lithography and etching processes, enables monolithic integration of both depletion-mode and enhancement-mode HEMTs on the same wafer without requiring additional fabrication steps or compromising manufacturing precision.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If fin width is reduced to control threshold voltage, then enhancement-mode operation is achieved, but manufacturing precision requirements increase

Engineering Contradiction:

Improvethreshold voltage controlVSAvoidfabrication process simplicity

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent applies partial action by creating fins with different widths rather than uniformly reducing all fin dimensions. The second fins have a reduced width compared to first fins, providing sufficient threshold voltage control for enhancement-mode operation while remaining manufacturable with standard lithography and etching processes. This approach achieves the necessary precision without excessive manufacturing complexity.

Inventive Principle:

Principle #16Partial or excessive action

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 parallel processing of E-mode and D-mode HEMTs with controlled threshold voltages, resulting in high switching speed and reliable performance for cascode drivers and logic applications, suitable for extreme temperature environments.

Implementation Method 1

a wide bandgap semiconductor layers made of aluminum gallium nitride (AlGaN) and gallium nitride (GaN) which create a sheet of two-dimensional electron gases (2DEG) by positive polarization induced interface charges (spontaneous and piezoelectric polarization)

Methodology Applied

Scientific EffectSpontaneous polarization: Polarisation

Implementation Method 2

Methodology Applied

Scientific EffectPiezoelectric polarization: Piezoelectric Effect

Implementation Method 3

The method involves varying the width of fins in the semiconductor layers of AlGaN/GaN HEMTs using electron beam lithography and inductively coupled plasma-reactive ion etching

Methodology Applied

Scientific EffectElectron beam: Electron Beam

Implementation Method 4

The method involves varying the width of fins in the semiconductor layers of AlGaN/GaN HEMTs using electron beam lithography and inductively coupled plasma-reactive ion etching

Methodology Applied

Scientific EffectPlasma: Plasma

Data Source

PatentUS20240014291A1Monolithic integration of enhancement-mode and depletion-mode galium nitride high electron mobility transistors

Publication Date: 2024.01.11 NAT RES COUNCIL OF CANADA

AI summary

A device and method of fabricating a device having depletion-mode and enhancement-mode high-electron-mobility transistors (HEMTs) on a single wafer are disclosed. The method of fabrication involves providing semiconductor layers capable of sustaining a two-dimensional electron sheet to enable electrical current to flow through the HEMT, forming a series of trenches and fins in the semiconductor layers over an active area of the semiconductor layers on which a gate contact terminal is to be set down, the fins of respective HEMTs having different widths resulting in different voltage thresholds for the respective depletion-mode HEMTs.