Ohmic Contact Formation Using Sacrificial Metal Doping in GaN HEMTs
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Solution Overview
Problem
Existing methods for forming ohmic contacts on compound semiconductor devices, such as GaN HEMTs, face challenges in achieving low-resistance and stable contacts, which are critical for the performance and reliability of integrated circuits.
Innovation Solution
A method involving the formation of a sacrificial metallic layer on a compound semiconductor device, followed by an annealing process to create a heavily doped region, and subsequent removal of the sacrificial layer to form a metal silicide layer on the doped region, enhancing the ohmic contact resistance and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional contact formation methods are used on GaN HEMTs, then the fabrication process is simple, but the contact resistance is high and stability is poor
Solution Approach 1:
The method performs preliminary doping of the channel layer through the barrier layer before contact formation using a sacrificial metallic layer and annealing process. This preliminary action creates a heavily doped region that ensures low resistance and stable ohmic contact, resolving the contradiction by preparing the contact area in advance rather than during the standard contact formation process.
Solution Approach 2:
The sacrificial metallic layer acts as an intermediary that facilitates the formation of a heavily doped region in the channel layer. It is deposited conformally, undergoes annealing to dope the underlying channel layer, and is then removed to reveal the doped region for subsequent metal deposition. This intermediary approach enables controlled doping without direct ion implantation, improving contact reliability.
2Reliability
If the sacrificial metallic layer is completely removed, then the ohmic contact resistance is low, but the sidewall protection is lost
Solution Approach 1:
The method applies local quality by differentiating the fate of the sacrificial metallic layer in different spatial locations. In the contact area, the sacrificial layer is completely removed to enable low-resistance ohmic contact. On the sidewalls, a portion of the sacrificial layer is retained as a spacer to provide protective coverage. This spatial differentiation resolves the contradiction between achieving low contact resistance and maintaining sidewall protection.
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 method results in the formation of a low-resistance and stable ohmic contact, improving the performance and reliability of compound semiconductor devices by increasing the nitrogen vacancy and forming a heavily doped region through the reaction with the sacrificial metallic layer.
Implementation Method 1
The sacrificial metallic layer is subjected to an annealing process, thereby forming a heavily doped region in the channel layer directly under the sacrificial metallic layer
Implementation Method 2
a two-dimensional electron gas (2DEG) is generated at a semiconductor heterojunction
Data Source
AI summary
A method for forming ohmic contacts on a compound semiconductor device is disclosed. A channel layer is formed on a substrate. A barrier layer is formed on the channel layer. A passivation layer is formed on the barrier layer. A contact area is formed by etching through the passivation layer and the barrier layer. The channel layer is partially exposed at a bottom of the contact area. A sacrificial metallic layer is conformally deposited on the contact area. The sacrificial metallic layer is subjected to an annealing process, thereby forming a heavily doped region in the channel layer directly under the sacrificial metallic layer. The sacrificial metallic layer is removed to expose the heavily doped region. A metal silicide layer is formed on the heavily doped region.