Gate Insulating Film Crystallization Suppression in GaN Devices
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The use of aluminum oxide as a gate insulating film on group III nitride semiconductor layers leads to crystallization, increasing leakage current and varying threshold voltage due to crystal grain boundaries and interface states formed during heat treatment.
Innovation Solution
A semiconductor device configuration with a gate insulating film comprising a first silicon-containing film with a higher crystallization temperature than aluminum oxide, and a second aluminum oxide film, where the first film has a hydrogen concentration of not lower than 1×10^21 atoms/cm^3, a nitrogen concentration of not lower than 1×10^19 atoms/cm^3, and a carbon concentration of not lower than 1×10^19 atoms/cm^3, preventing crystallization of the aluminum oxide film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum oxide is used as the gate insulating film on the group III nitride semiconductor layer, then the relative permittivity is improved (higher than silicon dioxide), but crystallization occurs during heat treatment leading to increased leakage current and threshold voltage variation
Solution Approach 1:
A silicon-containing film is introduced as an intermediary layer between the group III nitride semiconductor layer and the aluminum oxide gate insulating film. This intermediate film prevents direct interaction between the semiconductor layer and aluminum oxide during heat treatment, thereby suppressing crystallization of the aluminum oxide while maintaining its high permittivity benefits.
Solution Approach 2:
The gate insulating film structure is designed as a composite system consisting of multiple layers: a silicon-containing film layer and an aluminum oxide layer. This composite structure combines the advantages of both materials - the silicon-containing film provides crystallization suppression while the aluminum oxide provides high permittivity, achieving both reliability and compositional stability.
2Ease of manufacture
If heat treatment is applied to form the gate insulating film using aluminum oxide, then the film formation is achieved, but crystal grain boundaries are generated serving as electron propagation pathways increasing leakage current
Solution Approach 1:
The silicon-containing film acts as a protective intermediary that prevents the formation of crystal grain boundaries in the aluminum oxide layer during heat treatment. By suppressing crystallization, it eliminates the creation of electron propagation pathways, thereby reducing leakage current while still allowing the heat treatment process to proceed for film formation.
Solution Approach 2:
The silicon-containing film, which could be considered an additional manufacturing step, actually converts the potential harm of heat treatment-induced crystallization into a benefit by suppressing crystal grain boundary formation. The heat treatment process that would normally create harmful crystal structures is transformed into a beneficial process that forms the insulating film without creating leakage pathways.
3Reliability
If aluminum oxide is used as the gate insulating film, then higher relative permittivity is achieved, but interface states formed by crystallization trap carriers and vary threshold voltage
Solution Approach 1:
The silicon-containing film serves as a buffer intermediary between the semiconductor layer and aluminum oxide, preventing the formation of interface states that would otherwise trap carriers. This intermediate layer maintains electrical stability by eliminating the direct interface between materials that would create trapping sites, thereby stabilizing threshold voltage while preserving the high permittivity advantage.
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 suppresses crystallization of the aluminum oxide film, reducing leakage current and stabilizing the electric properties by inserting a silicon-containing film with high impurity concentrations between the semiconductor layer and the aluminum oxide film, thereby preventing crystallization and maintaining stable operation.
Implementation Method 1
aluminum oxide may be crystallized by heat treatment at an interface between the group III nitride semiconductor layer and aluminum oxide
Data Source
AI summary
There is provided a semiconductor device comprising a group III nitride semiconductor layer; a gate insulating film formed on the group III nitride semiconductor layer; and a gate electrode formed on the gate insulating film. The gate insulating film comprises a first film that is placed on the group III nitride semiconductor layer, includes silicon and has a higher crystallization temperature than a crystallization temperature of aluminum oxide; and a second film that is placed on the first film and contains aluminum oxide. The first film has a hydrogen concentration of not lower than 1×1021 atoms/cm3, a nitrogen concentration of not lower than 1×1019 atoms/cm3 and a carbon concentration of not lower than 1×1019 atoms/cm3. This configuration prevents crystallization of aluminum oxide.