HEMT Multi-Layer Passivation for Drain Current Drift
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Solution Overview
Problem
High electron mobility transistors (HEMTs) face challenges with drain current drift and leakage current performance due to charge build-up in semiconductor structures, leading to RF dispersion and passive intermodulation (PIM) distortion, especially when switching between on and off states.
Innovation Solution
The implementation of a multi-layer passivation structure with a first passivation layer made of a charge dissipation material, such as silicon-rich silicon nitride or alumina, and a second passivation layer of a non-charge dissipation material, strategically positioned between the source and drain contacts, helps dissipate trapped charges and reduce leakage currents, thereby improving drain current drift and leakage current performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-layer passivation structure is used, then the device structure is simple, but charge build-up occurs leading to drain current drift and leakage current
Solution Approach 1:
The passivation structure is divided into multiple layers with different functions: a first passivation layer (e.g., silicon-rich silicon nitride) that dissipates charges, and a second passivation layer that provides additional passivation. This segmentation allows each layer to address specific charge management needs, improving drain current drift performance while maintaining manageable structural complexity
Solution Approach 2:
Different regions of the passivation structure use different materials with specific properties tailored to local requirements. The first passivation layer uses charge dissipation material in regions where charge build-up is problematic, while other regions may use different materials optimized for their specific functions, thereby addressing local charge accumulation issues without uniformly increasing complexity throughout the entire structure
2Reliability
If a multi-layer passivation structure with charge dissipation material is implemented, then charge build-up is reduced improving drain current drift performance, but the device structure becomes more complex
Solution Approach 1:
The passivation structure is divided into multiple layers with different functions: a first passivation layer (e.g., silicon-rich silicon nitride) that dissipates charges, and a second passivation layer that provides additional passivation. This segmentation allows each layer to address specific charge management needs, improving drain current drift performance while maintaining manageable structural complexity
Solution Approach 2:
The passivation structure uses composite materials with different charge dissipation properties. By combining materials like silicon-rich silicon nitride (high charge dissipation) with other passivation materials (lower charge dissipation), the structure achieves superior charge management and leakage current performance through the synergistic effects of the composite material system
3Reliability
If passivation layers are strategically positioned between source and drain contacts, then leakage currents are reduced, but manufacturing process complexity increases
Solution Approach 1:
Different regions of the passivation structure use different materials with specific properties tailored to local requirements. The first passivation layer uses charge dissipation material in regions where charge build-up is problematic, while other regions may use different materials optimized for their specific functions, thereby addressing local charge accumulation issues without uniformly increasing complexity throughout the entire structure
Solution Approach 2:
The passivation layers are strategically positioned and formed during the manufacturing process to preemptively address charge build-up and leakage current issues before they affect device performance. By establishing the multi-layer passivation structure in advance during fabrication, the design anticipates and prevents charge management problems rather than requiring post-manufacturing adjustments
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
This configuration significantly enhances drain current drift performance and reduces PIM distortion by effectively modulating electron traps and minimizing charge accumulation, leading to improved operational stability and performance in high-frequency applications.
Implementation Method 1
a first passivation layer made of a charge dissipation material, such as silicon-rich silicon nitride or alumina
Implementation Method 2
effectively modulating electron traps and minimizing charge accumulation, leading to improved operational stability
Data Source
AI summary
A high electron mobility transistor includes a channel layer, a barrier layer on the channel layer, source and drain contacts on the barrier layer, a gate contact between the source and drain contacts, and a multi-layer passivation structure on the upper surface of the barrier layer between the source contact and the drain contact. The multi-layer passivation structure includes a first passivation layer that comprises a charge dissipation material directly contacts the upper surface of the barrier layer and a second passivation layer comprising a different material than the first passivation layer that also directly contacts the upper surface of the barrier layer. In some embodiments, at least one recess may be formed in the upper surface of the barrier layer and the second passivation layer may be formed within the recesses.