GaN Interlayer Barrier Structure Against Water and Ion Diffusion
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Solution Overview
Problem
Conventional GaN HEMT devices suffer from corrosion and destruction due to the diffusion of water and ion penetration through the passivation layer, especially under high electric fields, leading to insufficient THB lifetimes and device failure.
Innovation Solution
Implementing a barrier below the uppermost metal layer and in or above the lowermost interlayer dielectric to prevent the diffusion of water, water ions, sodium ions, and potassium ions, using materials like silicon oxynitride or silicon nitride, and optionally incorporating electrically conductive liners to prevent crack propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard thin silicon nitride passivation layer (100 nm) is used, then the device structure is simple and compatible with Si processes, but it is too thin to block water ions and provides insufficient protection against corrosion
Solution Approach 1:
The passivation system is divided into multiple functional layers: a thin silicon nitride layer (100 nm) for basic protection and process compatibility, and a thicker oxide layer (1000 nm) for enhanced ion blocking. This segmentation allows each layer to perform its specific function optimally while maintaining overall device simplicity.
Solution Approach 2:
The patent employs a composite passivation structure combining silicon nitride and oxide materials. The silicon nitride provides good adhesion and basic protection, while the oxide layer provides superior ion blocking capability. This composite approach achieves enhanced corrosion protection without significantly increasing device complexity.
2Reliability
If a thick top passivation layer (>800 nm) is used to block ions, then ion protection is improved, but cracks in the passivation layer propagate more easily into interlayer dielectrics and down to the GaN surface layer
Solution Approach 1:
The thick passivation requirement is segmented into two layers: a thin 100 nm silicon nitride layer that maintains crack resistance, and a 1000 nm oxide layer that provides the necessary ion blocking capability. This segmentation allows the system to achieve thick-layer protection benefits without the crack propagation problems of monolithic thick layers.
Solution Approach 2:
Different regions of the passivation system have different thicknesses and material properties optimized for their specific functions. The silicon nitride layer is thin and positioned where crack resistance is critical, while the oxide layer is thick and positioned where ion blocking is most needed, creating local quality optimization throughout the structure.
3Reliability
If conventional passivation layers are used, then the device structure is simple, but water and ions diffuse through the passivation layer under high electric fields, leading to oxidation and device destruction
Solution Approach 1:
The barrier function is segmented between the silicon nitride layer (providing basic protection and adhesion) and the oxide layer (providing enhanced ion blocking). This segmentation creates a more reliable barrier against water and ion diffusion under high electric fields without requiring a completely redesigned complex structure.
Solution Approach 2:
The composite structure of silicon nitride and oxide layers works synergistically to prevent water and ion diffusion. The silicon nitride provides good adhesion and basic protection, while the oxide provides superior ion blocking, together achieving extended device lifetime in harsh environments with minimal structural complexity.
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 barrier effectively prevents oxidation and ion diffusion, maintaining the integrity of the interlayer dielectrics and enhancing the device's lifetime by protecting the GaN surface layer from corrosion and electric field disruptions.
Implementation Method 1
The barrier is configured to prevent water, water ions, sodium ions and potassium ions from diffusing into the interlayer dielectric or portion of the interlayer dielectric immediately below the barrier
Implementation Method 2
The combination of a high electric field and moisture leads to severe oxidation of the GaN or AlGaN surface layer, and therefore to destruction of the device
Data Source
AI summary
A semiconductor device includes: a device formed in a III-V semiconductor body; metal layer(s) above the III-V semiconductor body; an interlayer dielectric adjacent each metal layer; vias electrically connecting each metal layer to the device formed in the III-V semiconductor body; a passivation layer touching and being supported by a top surface of the III-V semiconductor body, the lowermost interlayer dielectric touching and being supported by a top surface of the passivation layer, the passivation layer being an ineffective barrier against diffusion of water, water ions, sodium ions and potassium ions into the III-V semiconductor body; and a barrier interposed between a first oxide layer and a second oxide layer of the lowermost interlayer dielectric. The barrier is configured to prevent water, water ions, sodium ions and potassium ions from diffusing into the first oxide layer of the lowermost interlayer dielectric and which is immediately below the barrier.