HEMT Channel Supplying Layer Thickness Control

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Solution Overview

Problem

The fabrication of high electron mobility transistors (HEMTs) faces challenges in controlling the electron concentration in the two-dimensional electron gas (2DEG) channel, particularly in forming a low density 2DEG region, which affects the reproducibility and reliability of HEMT operations, especially in transitioning to an enhancement mode.

Innovation Solution

The method involves forming a channel supplying layer with a thickness of 0 to 15 nm, including a lightly doped drain region and a recess, and using channel increase layers and oxidation regions to control electron density, allowing for the formation of a low density 2DEG region and easy depletion under the gate electrode, thereby facilitating the fabrication of HEMTs in an enhancement mode.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If etching or oxidation methods are used to reduce electron concentration in the 2DEG channel, then the low density 2DEG region can be formed, but the manufacturing precision and reproducibility are degraded

Engineering Contradiction:

Improveelectron concentration controlVSAvoidreproducibility of low density 2DEG region

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies preliminary action by forming the low density 2DEG region through selective removal of the channel supplying layer before subsequent processing steps. This preliminary formation ensures precise electron concentration control from the outset, avoiding the need for post-processing etching or oxidation that degrades manufacturing precision and reproducibility.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent utilizes parameter changes by controlling the thickness of the channel supplying layer (0 to 15 nm) to precisely regulate electron concentration in the 2DEG channel. By adjusting this critical parameter during the formation stage, the invention achieves reliable and reproducible low density 2DEG regions without relying on less controllable etching or oxidation processes.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the 2DEG channel is formed with high electron concentration, then the channel conductivity is improved, but the breakdown voltage is reduced due to electric field concentration at the gate

Engineering Contradiction:

Improvebreakdown voltageVSAvoidelectric field concentration at gate

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by creating a spatially varying electron concentration profile in the 2DEG channel. The channel supplying layer thickness is selectively controlled to produce high electron concentration in most of the channel for good conductivity, while maintaining a low density 2DEG region near the gate to reduce electric field concentration. This local differentiation resolves the contradiction between overall channel performance and gate region stress.

Inventive Principle:

Principle #3Local quality

3Quantity of substance

If the channel supplying layer thickness is increased, then the electron density in the 2DEG channel is increased, but the formation of low density 2DEG region becomes more difficult

Engineering Contradiction:

Improveelectron densityVSAvoidlow density 2DEG region formation

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The patent utilizes parameter changes by precisely controlling the channel supplying layer thickness within a specific range (0 to 15 nm). This parameter control enables simultaneous achievement of adequate electron density for channel conduction and the ability to form low density 2DEG regions through selective removal, resolving the contradiction between quantity of electrons and manufacturability.

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 precise control of electron density in the 2DEG channel, improving reproducibility and reliability of HEMT operations by allowing for easier transition to an enhancement mode and reducing the concentration of electric field at the gate, thus enhancing the breakdown voltage and operational stability of HEMTs.

Implementation Method 1

A 2DEG may be induced by performing an n-doping process on a material having a large band gap or by using a material having polarization

Methodology Applied

Scientific EffectPolarization: Polarisation

Implementation Method 2

The electron concentration in the 2DEG channel may be reduced by etching an upper layer formed on the 2DEG channel and/or oxidizing the upper layer

Methodology Applied

Scientific EffectOxidation: Oxidation

Data Source

PatentUS9859410B2High electron mobility transistors and methods of fabricating the same

Publication Date: 2018.01.02 SAMSUNG ELECTRONICS CO LTD

AI summary

A High electron mobility transistor (HEMT) includes a source electrode, a gate electrode, a drain electrode, a channel forming layer in which a two-dimensional electron gas (2DEG) channel is induced, and a channel supplying layer for inducing the 2DEG channel in the channel forming layer. The source electrode and the drain electrode are located on the channel supplying layer. A channel increase layer is between the channel supplying layer and the source and drain electrodes. A thickness of the channel supplying layer is less than about 15 nm.