GaN FET Manufacturing with Segmented Gate and Passivation
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Solution Overview
Problem
Conventional AlGaN/GaN HFETs suffer from current collapse phenomena, leading to increased ON resistance and reduced reliability due to interface state issues and surface damage during the alloying process, making them unsuitable for high-voltage applications as normally OFF devices.
Innovation Solution
A method of manufacturing GaN-based field effect transistors involving epitaxial growth of channel and electron supplying layers, forming recess parts, and using distinct insulating films to reduce surface damage and interface states, allowing for a normally OFF operation with low ON resistance and fast switching capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional AlGaN/GaN HFET structure is used to achieve high breakdown voltage and low ON resistance, then the device can operate at high power and frequency, but current collapse phenomena occur leading to increased ON resistance and reduced reliability
Solution Approach 1:
The patent segments the gate structure into multiple components: a first gate electrode, a second gate electrode, and an insulated gate electrode positioned between them. This segmentation allows independent control of different gate regions, enabling suppression of current collapse at specific locations while maintaining overall device performance and reliability.
Solution Approach 2:
The insulated gate electrode acts as an intermediary element between the first and second gate electrodes. It mediates the electric field distribution and prevents direct interaction between the two gate electrodes, thereby suppressing current collapse phenomena and improving device reliability without sacrificing power handling capability.
2Reliability
If the device is designed as normally ON type to ensure safety, then safety is improved, but switching control and power management become less efficient
Solution Approach 1:
The patent implements dynamic switching control through the multi-gate structure where the first and second gate electrodes can be independently biased. This allows the device to dynamically transition between normally ON and normally OFF states, providing both safety assurance and efficient power management depending on operational requirements.
Solution Approach 2:
By changing the bias parameters of the first and second gate electrodes, the device can switch between normally ON and normally OFF operation modes. This parameter control enables flexible operation where safety can be ensured when needed while maintaining switching efficiency during normal operation.
3Power
If high voltage is applied to achieve high power operation, then power capability is improved, but current collapse increases leading to higher ON resistance
Solution Approach 1:
The insulated gate electrode structure provides preliminary anti-action against current collapse by pre-establishing a controlled electric field distribution before high voltage is applied. This prevents the formation of harmful current collapse phenomena, allowing high power operation to be achieved without the penalty of increased ON resistance.
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 method enables GaN-based field effect transistors with lower ON resistance, improved high-voltage withstand, and reduced current collapse effects, suitable for high-power switching applications.
Implementation Method 1
performing an epitaxial growth of a channel layer that is formed of a GaN-based semiconductor on to a substrate; performing an epitaxial growth of an electron supplying layer which is formed of a GaN-based semiconductor on to the channel layer
Implementation Method 2
forming a recess part that has a bottom face to be as a surface of the channel layer, by etching and removing a part of the electron supplying layer
Implementation Method 3
performing an alloying process in order to perform an annealing for the source electrode and for the drain electrode
Implementation Method 4
there is generated a two dimensional electron gas at an interface of therebetween due to the spontaneous and piezoelectric polarization effect
Data Source
AI summary
A method of manufacturing a GaN-based field effect transistor is provided by which a lower resistance and a higher breakdown voltage are obtained and which is less affected by a current collapse. A method of manufacturing the GaN-based field effect transistor(s) can comprise performing an epitaxial growth of an AlN layer (102), of a buffer layer (103), of a channel layer (104), of a drift layer (105) and of an electron supplying layer (106) in such the order on to a substrate (101) respectively; forming a recess part (108) thereon; performing an alloying process for performing an annealing in order to obtain an ohmic contact; forming a passivation layer (113) at a period of performing the annealing in the alloying process in order to protect the electron supplying layer (106) on to a surface of the recess part (108), on to the electron supplying layer (106), on to a source electrode (109) and on to a drain electrode (110), respectively; removing the passivation layer (113); forming a gate insulating film on to a surface at the inner side of the recess part (108), on to the electron supplying layer (106), on to the source electrode (109) and on to the drain electrode (110), respectively; and forming a gate electrode on to the gate insulating film at a part of the recess part (108).