GaN HEMT Ohmic Contact Structure for Lower Contact Resistance
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Solution Overview
Problem
The existing methods for secondary epitaxial growth of n-type heavily doped GaN in ohmic contact regions for GaN-based HEMT devices result in increased contact resistance due to poor contact between the heavily doped GaN material and the sidewall of the channel structure, primarily caused by etching inaccuracies.
Innovation Solution
A semiconductor structure and manufacturing method that involve forming a first groove and a recessed trench in the source and drain regions of the channel structure, where the heavily doped material layer fills both the groove and the trench, thereby enhancing the contact area and reducing contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If etching is performed to form grooves in the channel structure, then the contact area between heavily doped GaN material and channel structure can be improved, but etching accuracy problems cause over-etching that recesses the channel structure sidewall and worsens contact quality
Solution Approach 1:
A sacrificial oxide layer is introduced as an intermediary between the channel structure and the heavily doped GaN material. This oxide layer serves as a buffer that compensates for etching over-recess, ensuring that the heavily doped material can still make contact with the channel structure even when the sidewall is recessed. The oxide layer is selectively removed in controlled steps to enable subsequent material deposition while maintaining contact integrity.
Solution Approach 2:
The channel structure sidewall is pre-coated with an oxide layer before the heavily doped GaN material is deposited. This preliminary action ensures that even if etching causes over-recess, the oxide layer remains as a protective buffer that maintains the contact interface. The oxide layer is then selectively removed in controlled steps to enable the heavily doped material to contact the channel structure at the correct position.
2Strength
If the sidewall of channel structure is recessed due to over-etching, then the structural integrity is maintained, but the contact resistance between heavily doped GaN material and sidewall greatly increases
Solution Approach 1:
The oxide layer acts as a mediator that bridges the gap created by sidewall recess. It provides a continuous conductive path between the heavily doped GaN material and the channel structure, maintaining low contact resistance even when the sidewall is recessed due to over-etching. The oxide layer compensates for the geometric discontinuity while preserving both structural integrity and electrical contact.
Solution Approach 2:
The oxide layer changes the physical and chemical parameters of the contact interface. By introducing a material with different properties (oxide) between the GaN material and channel structure, the contact resistance is reduced despite the sidewall recess. The oxide layer's properties are optimized to provide both mechanical support and electrical conductivity at the contact interface.
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 proposed solution effectively reduces the contact resistance between the heavily doped material layer and the sidewall of the channel structure, improving the overall ohmic contact performance and frequency and power performance of the GaN-based HEMT devices.
Implementation Method 1
The secondary epitaxial growth of n-type heavily doped GaN in an ohmic contact region has become a new international process
Data Source
AI summary
A semiconductor structure includes a substrate, a channel structure, a first groove, an insertion layer, and a heavily doped material layer. The channel structure is located on the substrate. The channel structure includes a channel layer and a barrier layer. The channel structure includes a gate region, a source region and a drain region. The source region and the drain region are located on two sides of the gate region. The first groove is located in the source region and the drain region. The first groove penetrates at least the barrier layer. The insertion layer is disposed in the barrier layer. The recessed trench is in communication with the first groove. The heavily doped material layer fills the first groove and the recessed trench.