Nitride Semiconductor Device Contact Resistance Reduction
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Solution Overview
Problem
Conventional methods for forming n-side electrodes on GaN substrates result in poor contact characteristics due to high contact resistance, which is attributed to carbon adsorption at the interface, making mass production challenging.
Innovation Solution
A nitride semiconductor device with a nitrogen surface on the rear face and a method involving the deposition and removal of an insulative film, such as silicon oxide, to reduce carbon concentration at the interface between the substrate and the n-side electrode, improving contact characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If an n-side electrode is formed on the rear face of a GaN substrate, then the chip area is reduced and production cost is lowered, but contact resistance increases and contact characteristics deteriorate
Solution Approach 1:
The patent applies preliminary action by performing carbon removal treatment on the rear face of the GaN substrate before forming the n-side electrode. This preliminary cleaning step eliminates carbon adsorption that would otherwise cause high contact resistance, ensuring good contact characteristics are achieved before electrode formation. The carbon removal process (using plasma, chemical treatment, or mechanical means) prepares the surface in advance to prevent contact issues.
Solution Approach 2:
The patent introduces an intermediary layer or treatment between the rear face and the n-side electrode to improve contact. This may involve forming a thin intermediate layer (such as a metal layer or treated surface layer) that facilitates better electrical contact between the electrode and substrate, acting as a mediator to overcome the carbon-induced contact resistance problem.
2Reliability
If micromachining is performed to form bumps and dents on the substrate rear face, then contact characteristics are improved, but manufacturing complexity and production difficulty increase
Solution Approach 1:
The patent extracts the harmful carbon layer from the rear face surface through removal treatment, separating the problematic carbon adsorption from the substrate surface. This extraction of carbon (via plasma treatment, chemical etching, or mechanical removal) eliminates the root cause of poor contact without requiring complex micromachining operations to create bumps and dents.
Solution Approach 2:
The patent changes the surface parameters of the rear face by controlling carbon concentration to 5 atom% or less through various removal treatments. By modifying the chemical composition and surface state parameters (carbon content, surface roughness, cleanliness) rather than creating complex geometric structures, the patent achieves good contact characteristics with simpler manufacturing.
3Ease of manufacture
If carbon concentration at the interface is high, then the interface forms easily, but electrical barrier effect increases and contact resistance rises
Solution Approach 1:
The patent converts the harmful effect of carbon (which naturally adsorbs on GaN surfaces) into a beneficial situation by systematically removing it to 5 atom% or less. The carbon removal treatment transforms the naturally carbon-contaminated surface into a clean, low-resistance contact surface, turning the usual problem of carbon adsorption into an opportunity for achieving excellent contact characteristics.
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 effectively reduces contact resistance to 5×10−4Ω·cm2 or less, enhancing the reproducibility and yield of nitride semiconductor devices by eliminating carbon as an electrical barrier at the interface.
Implementation Method 1
carbon adsorption at the interface
Implementation Method 2
a step of reducing a carbon concentration in the rear face is performed
Data Source
AI summary
An nitride semiconductor device according to the present invention is a nitride semiconductor device including: an n-GaN substrate 10; a semiconductor multilayer structure 100 formed on a principal face of the n-GaN substrate 10, the semiconductor multilayer structure 100 including a p-type region and an n-type region; a p-side electrode 32 which is in contact with a portion of the p-type region included in the semiconductor multilayer structure 100; and an n-side electrode 34 provided on the rear face of the n-GaN substrate 10. The rear face of the n-GaN substrate includes a nitrogen surface, such that a carbon concentration at an interface between the rear face and the n-side electrode 34 is adjusted to 5 atom % or less.