2DEG Contact Structure With Nonlinear Implant Interface
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Solution Overview
Problem
The existing methods for creating semiconductor contact structures with a two-dimensional electron gas (2 DEG) face challenges in achieving low resistance connections due to crystal damage and interface degradation from silicon implantation, resulting in significant resistance values that are not sufficient for applications like radio frequency (RF) and impact on-device performance.
Innovation Solution
A semiconductor contact structure is designed with a nonlinear interface shape between the silicon implant and the 2 DEG, increasing the effective interface length to reduce transition resistance, which can be crenulated, saw-tooth, circular, or rectangular in shape, optimized through analytical and simulated methods to minimize total resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon implantation is performed to create contact structures, then metal to semiconductor contact resistance can be reduced to 0.06 ohm*mm, but crystal damage and interface degradation occur leading to 2 DEG density reduction and resistance increase of 0.4 to 0.5 ohm*mm
Solution Approach 1:
The contact structure is segmented into distinct functional layers: a first contact layer (silicon implant) that provides low resistance to the semiconductor, and a second contact layer (metal electrode) that provides low resistance to the 2 DEG. This segmentation allows each layer to optimize its function without compromising the other, resolving the contradiction between achieving low contact resistance and avoiding crystal damage.
Solution Approach 2:
The first contact layer acts as an intermediary between the metal electrode and the 2 DEG. It mediates the interaction by providing a transition zone that reduces the harmful effects of direct metal-to-semiconductor contact, thereby preventing crystal damage and interface degradation while maintaining low resistance.
2Reliability
If high temperature annealing is performed after metal deposition, then low resistance contact is achieved between 2 DEG and electrode, but noble metals such as gold are prohibited in CMOS fabrication
Solution Approach 1:
The first contact layer uses standard CMOS-capable metals (such as titanium or aluminum) that are readily available and compatible with CMOS fabrication processes. These materials serve as a disposable intermediate layer that achieves the necessary low resistance contact without requiring prohibited noble metals, thus resolving the contradiction between contact performance and fabrication compatibility.
3Reliability
If AlGaN recess is performed to achieve low resistance contact, then contact resistivity of 0.5 ohm*mm can be achieved, but process complexity increases due to required annealing and recess steps
Solution Approach 1:
The first contact layer is formed in advance through silicon implantation and annealing, creating a pre-prepared low-resistance pathway to the semiconductor. This preliminary action simplifies subsequent processing steps and reduces overall process complexity while maintaining the ability to achieve low contact resistivity.
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 approach improves ohmic contact performance by reducing total transition resistance by up to 30% and enhances contact uniformity across the wafer, meeting the requirements for lower resistance needed in advanced semiconductor applications.
Implementation Method 1
ion implantation of silicon (Si) into contact regions
Implementation Method 2
high temperature annealing after deposition of the electrode metals
Data Source
AI summary
A semiconductor contact structure including a two-dimensional electron gas (2DEG) between a first and a second semiconductor layer and a silicon implant extending into at least a part of the first semiconductor layer and into at least a part of the second semiconductor layer and connected to the 2DEG along an interface between the 2DEG and the silicon implant, wherein the interface has a nonlinear shape. The structure further includes a contact connected to the 2DEG via the silicon implant.