GaN Transistor Field Plate Structures with Patterned Passivation
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Solution Overview
Problem
Conventional GaN transistors face challenges in simultaneously reducing leakage current and gate-to-drain capacitance while maintaining high electron density in the channel and low electric fields, as single or two insulator layers fail to achieve these characteristics effectively.
Innovation Solution
A column III nitride transistor with multiple interleaved segments of different insulators, including an insulator offset layer, positioned between the gate and drain contacts, to balance electron donor density and electric field distribution, along with metal field plates to shape the electric field and enhance breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a single layer of surface passivating insulator is used, then leakage current is reduced, but gate-to-drain capacitance cannot be sufficiently reduced and electron density in channel is insufficient
Solution Approach 1:
The patent divides the surface passivating insulator into multiple interleaved segments of different insulator materials (first insulator segments and second insulator segments) positioned at different locations between gate and drain contacts. This segmentation allows each insulator type to perform its specialized function: first insulators reduce leakage current while second insulators reduce gate-to-drain capacitance, resolving the contradiction between these two parameters.
Solution Approach 2:
The patent applies different insulator materials with different properties at different locations along the gate-drain path. First insulator segments are positioned where leakage current reduction is prioritized, while second insulator segments are positioned where gate-to-drain capacitance reduction is prioritized. This local differentiation of insulator quality enables simultaneous optimization of both parameters.
2Ease of manufacture
If conventional insulator structures are used, then manufacturing is simpler, but device breakdown voltage is limited and cannot withstand higher voltages
Solution Approach 1:
The patent employs composite insulator structures consisting of multiple interleaved insulator segments made from different insulator materials. This composite approach combines the advantages of different materials to achieve higher breakdown voltage while maintaining manufacturability through established semiconductor fabrication processes for depositing and patterning multiple insulator layers.
3Ease of manufacture
If uniform insulator density is used, then manufacturing is easier, but electron donor density cannot be optimized for high electron density in channel and low electric fields
Solution Approach 1:
The patent creates local variations in insulator properties by using different insulator materials with different electron donor densities at different locations. First insulator segments have properties optimized for reducing leakage current, while second insulator segments have properties optimized for reducing gate-to-drain capacitance and controlling electron density. This local quality differentiation enables precise control of electron donor density without compromising manufacturability.
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 solution effectively reduces leakage current and gate-to-drain capacitance while maintaining high electron density and low drain fields, enabling GaN transistors to withstand higher voltages and achieve precise control over device characteristics.
Implementation Method 1
The net electron donor density above the channel under the first insulator segments is lower than a net electron density above the channel under the second insulator segments
Implementation Method 2
reduces leakage current and gate-to-drain capacitance
Implementation Method 3
metal field plates to shape the electric field and enhance breakdown voltage
Implementation Method 4
The different material in the adjacent nitride layers also causes polarization, which contributes to a conductive two-dimensional electron gas (2DEG) region near the junction of the two layers
Data Source
AI summary
A gallium nitride (GaN) transistor which includes multiple insulator semiconductor interface regions. Two or more first insulator segments and two or more second insulator segments are positioned between the gate and drain contacts and interleaved together. At least one first insulator segment is nearer to the gate contact than the second insulator segments. At least one second insulator segment is nearer to the drain contact than the first insulator segments. The first and second insulators are chosen such that a net electron donor density above the channel under the first insulator segments is lower than a net electron density above the channel under the second insulator segments. The first insulator segments reduce gate leakage and electric fields near the gate that cause high gate-drain charge. The second insulator segments reduce electric fields near the drain contact and provide a high density of charge in the channel for reduced on-resistance.