GaN Semiconductor Device SiN Insulating Film Current Collapse
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Solution Overview
Problem
Nitride semiconductor devices with n-type GaN layers face issues of increased leak current due to conductive GaN layers and current collapse caused by excess Si atoms in SiN films, which degrade the I-V characteristics by extracting nitrogen atoms and creating deep traps.
Innovation Solution
A nitride semiconductor device with a silicon nitride (SiN) insulating film having a composition ratio of silicon to nitrogen greater than ¾ and substantial oxygen content, formed using plasma-enhanced chemical vapor deposition (p-CVD), is used between the gate and drain electrodes, along with a second insulating film with stoichiometric composition, to suppress current collapse and leak current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an n-type GaN layer is used to enhance current to voltage characteristic, then the I-V characteristic is improved, but the leak current increases
Solution Approach 1:
An AlGaN layer is introduced as an intermediate layer between the n-type GaN layer and the SiN insulating film. This AlGaN layer acts as a mediator that prevents direct interaction between the conductive GaN and the SiN film, thereby reducing leak current while preserving the improved I-V characteristic provided by the n-type GaN layer.
Solution Approach 2:
The patent utilizes the natural tendency of Si atoms in the SiN film to bind with N atoms by providing an AlGaN layer that contains nitrogen, allowing the Si atoms to satisfy their chemical affinity for nitrogen without extracting nitrogen from the active GaN channel layer, thus preventing deep trap formation and current collapse.
2Reliability
If an SiN film with Si-rich composition is used, then the current collapse is suppressed, but nitrogen atoms are extracted from the GaN layer causing vacancies and deep traps
Solution Approach 1:
The AlGaN layer serves as a protective intermediary between the SiN film and the GaN layer. It allows the SiN film to maintain its Si-rich composition for suppressing current collapse while preventing the Si atoms from extracting nitrogen from the GaN layer, as the AlGaN layer absorbs the excess nitrogen demand.
Solution Approach 2:
The patent applies different compositions of AlGaN layers at different locations: the first AlGaN layer has a specific composition ratio optimized for preventing nitrogen extraction at the interface with SiN, while the second AlGaN layer has a different composition ratio optimized for maintaining channel conductivity. This local differentiation resolves the contradiction between suppressing current collapse and maintaining GaN layer integrity.
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 Si-rich SiN film with high oxygen content terminates dangling bonds and captures nitrogen vacancies, stabilizing the surface states and reducing current collapse, while the stoichiometric SiN film minimizes nitrogen dissociation, effectively enhancing the I-V characteristics and reducing drain leak current.
Implementation Method 1
The first insulating film is made of silicon nitride (SiN) and formed by a plasma-enhanced chemical vapor deposition (p-CVD) technique
Data Source
AI summary
A process for forming a nitride semiconductor device is disclosed. The resulting semiconductor device includes a semiconductor stack with a top layer containing gallium (Ga) and nitrogen (N), electrodes of a source, a gate and a drain provided on the semiconductor stack, and a silicon nitride (SiN) film provided on the GaN layer between the drain electrode and the gate electrode but apart from the gate electrode. The SiN film has a silicon rich composition with a composition ratio of Si/N that is greater than ¾ and substantial oxygen contents.