Nitride Semiconductor Gate Stack Stress Engineering
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Solution Overview
Problem
Semiconductor devices using nitride semiconductors face issues with current collapse phenomena and metal diffusion into insulating films, particularly in high-frequency power devices like HEMT transistors, where existing silicon nitride films fail to simultaneously suppress these issues effectively.
Innovation Solution
A semiconductor device structure featuring a gate electrode on a nitride semiconductor layer, with a first silicon nitride film having a silicon-to-nitrogen ratio of 0.75 or higher and compressive stress, and a second silicon nitride film with the same ratio but tensile stress, forming a stacked layer structure that suppresses metal diffusion and current collapse by controlling stress and leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer silicon nitride film is used to cover the gate electrode, then the structure is simple, but it cannot simultaneously suppress metal diffusion and current collapse effectively
Solution Approach 1:
The silicon nitride film is divided into two distinct layers: a first silicon nitride film with compressive stress that suppresses metal diffusion, and a second silicon nitride film with tensile stress that suppresses current collapse. This segmentation allows each layer to perform its specific function independently, resolving the contradiction between reliability improvement and structural simplicity.
Solution Approach 2:
The patent uses a composite structure of two silicon nitride films with different stress characteristics. The first film has compressive stress (Si/N ratio ≥ 0.75) to prevent metal diffusion, while the second film has tensile stress to reduce current collapse. This composite approach enables simultaneous suppression of both failure mechanisms without requiring entirely different materials.
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 gate leakage, current collapse, and metal diffusion, maintaining stable device characteristics during burn-in tests, while preventing metal diffusion into the insulating film, thus addressing the limitations of existing technologies.
Implementation Method 1
a first silicon nitride film that covers the gate electrode and the silicon nitride film and has a composition ratio of silicon to nitrogen equal to or larger than 0.75, the first silicon nitride film having compressive stress solely
Implementation Method 2
a second silicon nitride film that is formed on the first silicon nitride film and has a composition ratio of silicon to nitrogen equal to or larger than 0.75 solely, a whole stacked layer structure of the first and second silicon nitride films having tensile stress
Data Source
AI summary
A semiconductor device includes a gate electrode formed on a nitride semiconductor layer, and a source electrode and a drain electrode provided on the nitride semiconductor layer so as to interpose the gate electrode therebetween, a first silicon nitride film that covers the gate electrode and the silicon nitride film and has a composition ratio of silicon to nitrogen equal to or larger than 0.75, the first silicon nitride film having compressive stress solely, and a second silicon nitride film that is formed on the first silicon nitride film and has a composition ratio of silicon to nitrogen equal to or larger than 0.75 solely, a whole stacked layer structure of the first and second silicon nitride films having tensile stress.