III-Nitride Semiconductor Gate Dielectric Interface State Reduction
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Solution Overview
Problem
III group nitride semiconductor devices, particularly insulated gate field effect transistors, face issues with high gate leakage current and current collapse due to interface states between dielectric layers and nitride semiconductor layers, which affect their performance and reliability.
Innovation Solution
A composite dielectric layer comprising nitride, oxynitride, and oxide layers is introduced between the gate metal layer and the nitride semiconductor layer to reduce interface states, thereby minimizing leakage current and current collapse effects. This layer structure includes an aluminum nitride dielectric layer, an aluminum oxynitride layer, and an aluminum oxide layer, with the aluminum nitride layer being less than 2 nm thick to avoid threshold voltage drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single dielectric layer is used as insulated gate dielectric, then the device structure is simple, but interface states are high causing severe current collapse effect
Solution Approach 1:
The single dielectric layer is segmented into multiple layers with different compositions (AlN, AlGaN, AlxGa1-xN:y). Each layer serves specific functions: the AlN layer provides lattice matching and reduces interface states, the AlGaN layer provides insulation, and the graded AlxGa1-xN:y layer transitions composition to minimize dislocation density. This segmentation resolves the contradiction by reducing interface states through layered structure while maintaining manageable complexity through systematic design.
Solution Approach 2:
The patent employs composite dielectric materials with varying aluminum and nitrogen compositions arranged in multiple layers. The composite structure combines materials with different properties: AlN for low interface states, AlGaN for insulation, and graded composition layers for stress management. This composite approach reduces current collapse effect while the systematic layering keeps the overall structure controllable.
2Reliability
If aluminum nitride layer is made thicker to reduce interface states, then current collapse effect is reduced, but threshold voltage drift occurs
Solution Approach 1:
Different regions of the dielectric structure have different thicknesses and compositions optimized for their specific functions. The AlN layer at the interface has specific thickness (e.g., 2-5 nm) optimized for reducing interface states without causing excessive threshold voltage drift. The graded AlxGa1-xN:y layer has varying composition (y parameter) that transitions from higher nitrogen content near the interface to lower content away from it, creating local quality variations that manage both interface states and electric field distribution to control threshold voltage.
Solution Approach 2:
The patent changes material composition parameters systematically. The graded AlxGa1-xN:y layer varies the nitrogen content parameter (y) through its thickness, transitioning from higher to lower nitrogen content. This parameter gradient allows the structure to reduce interface states where needed while managing the overall electric field to prevent threshold voltage drift. The composition parameter y is adjusted locally to achieve both objectives.
3Loss of energy
If oxide dielectric layer is used to reduce gate leakage current, then gate insulation is improved, but interface states increase causing current collapse
Solution Approach 1:
The AlN layer acts as an intermediary between the nitride semiconductor and the oxide-containing dielectric layers. It provides a low-interface-state-density interface with the semiconductor while the subsequent AlGaN and graded AlxGa1-xN:y layers provide the insulation function. This intermediary structure separates the functions of interface state reduction and gate insulation, allowing oxide-containing layers to provide insulation without directly contacting the semiconductor and creating harmful interface states.
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 composite dielectric layer significantly reduces both gate leakage current and current collapse effects, enabling a nitride semiconductor device with low interface states, high gate bearable voltage, and improved power handling capabilities.
Implementation Method 1
A composite dielectric layer comprising nitride, oxynitride, and oxide layers is introduced between the gate metal layer and the nitride semiconductor layer to reduce interface states
Implementation Method 2
a large amount of charges are generated in a channel layer by piezoelectric polarization and spontaneous polarization
Data Source
AI summary
An III group nitride semiconductor device comprises: a substrate; a nitride semiconductor layer located on the substrate; a passivation layer located on the nitride semiconductor layer, a portion of the passivation layer in a gate region being etched to expose the nitride semiconductor layer so as to form a gate groove; a composite dielectric layer located on the passivation layer and the gate groove, the composite dielectric layer comprising one or more combination structures of two or more of a nitride dielectric layer, an oxynitride dielectric layer and an oxide dielectric layer which are formed sequentially in the direction away from the substrate; and a source electrode and a drain electrode respectively located in a source region and a drain region on the nitride semiconductor layer, and a gate electrode located in a gate region between the source region and the drain region on the composite dielectric layer.