Nanolaminated Gate Insulator for Wide Band Gap Transistor Stability
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Solution Overview
Problem
High-permittivity dielectrics used in wide band gap transistors tend to crystallize at high temperatures, leading to increased leakage currents and requiring additional processing steps, which increase production costs and complexity.
Innovation Solution
A nanolaminated insulating gate structure composed of alternately deposited amorphous aluminum oxide and hafnium oxide layers, which diffuse and mix during annealing to form a stable, high-permittivity gate stack that avoids crystallization, allowing for simplified processing and reduced thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-permittivity dielectrics are used in insulating gate structures, then the electric field and on-state resistance are reduced, but the materials tend to crystallize at high temperatures leading to increased leakage currents
Solution Approach 1:
The patent uses a composite nanolaminated structure consisting of alternating layers of amorphous aluminum oxide and hafnium oxide. This composite material combines the high permittivity of hafnium oxide with the thermal stability of aluminum oxide, preventing crystallization at high temperatures while maintaining the desired electrical properties for reducing electric field and on-state resistance.
Solution Approach 2:
The patent changes the physical and chemical parameters of the dielectric material by using nanoscale layering and maintaining amorphous phase through controlled deposition. The nanolaminated structure with specific layer thicknesses and the amorphous phase composition allow the material to withstand high temperatures without crystallization, thus preventing leakage current increase while preserving high permittivity characteristics.
2Reliability
If high-permittivity dielectrics are used, then device performance is improved, but additional processing steps are required to prevent crystallization, increasing production costs
Solution Approach 1:
The patent applies preliminary action by depositing the nanolaminated amorphous structure before any high-temperature processing steps. The amorphous aluminum oxide and hafnium oxide layers are conformally deposited in alternated succession to form the gate stack, ensuring thermal stability is built into the structure before subsequent manufacturing steps, thereby eliminating the need for additional protective processing steps.
3Stability of the object's composition
If amorphous aluminum oxide and hafnium oxide layers are deposited in alternated succession, then high permittivity is maintained with thermal stability, but additional deposition steps are required
Solution Approach 1:
The patent segments the dielectric layer into multiple thin alternating layers of aluminum oxide and hafnium oxide, each deposited conformally in succession. This segmentation allows precise control over the composition and thickness of each layer, enabling the structure to maintain amorphous phase at high temperatures while achieving the desired overall thickness and permittivity characteristics for the gate insulator.
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 maintains high permittivity values while preventing material degradation at high temperatures, optimizing the process flow by eliminating unnecessary steps and reducing production costs.
Implementation Method 1
the aluminum oxide layers and the hafnium oxide layers having nanometer thickness to form a gate stack, followed by an annealing step
Data Source
Figure 1~2c
Figure 3~4
Figure 5~6
AI summary
A wide band gap transistor includes a semiconductor structure (2), having at least one wide band gap semiconductor layer (14, 16) of gallium nitride (GaN) or silicon carbide (SiC), an insulating gate structure (8) and a gate electrode (7), separated from the semiconductor structure (2) by the insulating gate structure (8). The insulating gate structure (8) contains a mixture of aluminum, hafnium and oxygen and is completely amorphous.