HEMT Contact Structure With 3D Protrusions for Lower Rc
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Solution Overview
Problem
Existing high electron mobility transistors (HEMTs) face challenges in reducing on-resistance (Rdson) and power loss due to high contact resistance (Rc) with the two-dimensional electron gas (2DEG) layer.
Innovation Solution
The HEMT design incorporates a contact structure with a body portion and a plurality of protruding portions connected to the bottom surface of the body portion. This contact structure penetrates through the passivation layer and is in direct contact with the barrier layer, while the protruding portions extend through the barrier layer and a portion of the channel layer, reducing contact resistance with the 2DEG layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional contact structure is used, then the device structure is simple, but the contact resistance with the 2DEG layer is high
Solution Approach 1:
The contact structure is divided into a body portion and multiple protruding portions that extend into the channel layer. This segmentation allows different parts of the contact structure to serve different functions: the body portion provides structural support and electrical connection, while the protruding portions directly contact the 2DEG layer to reduce contact resistance. The segmentation resolves the contradiction by creating a multi-component structure that achieves low contact resistance without excessive complexity.
Solution Approach 2:
The contact structure transitions from a conventional planar contact to a three-dimensional structure with protruding portions extending vertically into the channel layer. This dimensional change allows the contact to reach the 2DEG layer more effectively, reducing contact resistance by establishing direct electrical contact in the vertical dimension while maintaining a relatively simple overall structure.
2Loss of energy
If the contact resistance is reduced, then the on-resistance and power loss are reduced, but the contact structure becomes more complex
Solution Approach 1:
By segmenting the contact into body and protruding portions, the invention achieves reduced power loss through lower contact resistance while keeping the structural complexity manageable. The segmentation allows the protruding portions to specifically target the 2DEG layer for optimal electrical contact without requiring complete redesign of the entire contact system.
Solution Approach 2:
The protruding portions are strategically positioned to make local contact with the 2DEG layer where it is most needed for reducing contact resistance. This local quality approach reduces power loss at the critical contact interface while maintaining a simple overall contact structure that does not require complex modifications throughout the entire device.
3Reliability
If the contact structure penetrates deeper into the channel layer, then the contact resistance decreases, but the manufacturing precision requirements increase
Solution Approach 1:
The segmentation into body and protruding portions allows for staged manufacturing processes. The body portion can be formed first with standard precision, and then the protruding portions can be added in subsequent steps. This segmentation reduces the overall manufacturing precision requirements compared to forming a single complex deep-penetrating contact structure in one step.
Solution Approach 2:
The body portion is formed first as a preliminary structure, providing a foundation for the subsequent formation of protruding portions. This preliminary action allows manufacturers to establish the main contact structure with standard precision before adding the finer protruding features, thereby reducing the overall manufacturing precision requirements while still achieving deep penetration into the channel layer.
Data Source
AI summary
A method for forming a high electron mobility transistor is disclosed. A mesa structure having a channel layer and a barrier layer is formed on a substrate. The mesa structure has two first edges extending along a first direction and two second edges extending along a second direction. A passivation layer is formed on the substrate and the mesa structure. A first opening and a plurality of second openings connected to a bottom surface of the first opening are formed and through the passivation layer, the barrier layer and a portion of the channel layer. In a top view, the first opening exposes the two first edges of the mesa structure without exposing the two second edges of the mesa structure. A metal layer is formed in the first opening and the second openings thereby forming a contact structure.