GaN Transistor N-Plane Formation via Support Substrate Inversion
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Solution Overview
Problem
The development of GaN semiconductor devices with transistors formed on the N-plane is hindered by the difficulty of crystal growth in the N-polar direction, leading to poor crystal quality and high contact resistance, which limits their high-frequency characteristics and practical application.
Innovation Solution
A manufacturing method for GaN semiconductor devices that forms transistor elements on the N-plane of a GaN epitaxial substrate grown in the Ga-polar direction, allowing for the use of a support substrate without the need for N-polar crystal growth, and includes a multilayer structure with an n-type conductive layer to reduce contact resistance and improve crystal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If crystal growth is performed in the N-polar direction to form transistors on the N-plane, then high-frequency characteristics and low contact resistance are achieved, but crystal quality deteriorates and manufacturing difficulty increases
Solution Approach 1:
The patent inverts the conventional approach by forming transistors on the N-plane side rather than the conventional Ga-plane side. This is achieved by bonding a support substrate to the Ga-plane of a GaN epitaxial substrate grown in the Ga-polar direction, then removing the growth substrate to expose the N-plane, allowing transistor formation on the previously difficult-to-access N-plane surface
Solution Approach 2:
The patent introduces a support substrate as an intermediary element that enables the formation of transistors on the N-plane. The support substrate is bonded to the Ga-plane side, allowing the growth substrate to be removed and the N-plane to be exposed for transistor formation, thus mediating between the crystal growth process and the final device structure
2Manufacturing precision
If the AlGaN layer is positioned closer to the channel to improve electron supply, then contact resistance increases due to barrier effects, but crystal quality improves
Solution Approach 1:
The patent inverts the conventional layer arrangement by forming transistors on the N-plane side, which reverses the position of the AlGaN layer relative to the channel. This inversion eliminates the barrier effect between the AlGaN layer and the contact electrodes, allowing for lower contact resistance while maintaining good crystal quality
3Ease of operation
If N-polar crystal growth is attempted to improve transistor performance, then contact resistance decreases, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The patent performs preliminary actions by bonding the support substrate to the Ga-plane side before removing the growth substrate. This preliminary bonding enables subsequent easy access to the N-plane for transistor formation, avoiding the need for complex N-polar crystal growth processes
Solution Approach 2:
The support substrate serves as an intermediary that simplifies the manufacturing process. By bonding it to the Ga-plane side first, the growth substrate can be removed to expose the N-plane, making transistor formation straightforward without requiring complex N-polar growth techniques
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 method enables the production of GaN semiconductor devices with reduced contact resistance and improved high-frequency characteristics, allowing for high-speed transistors while simplifying the manufacturing process and reducing costs by avoiding the complexity of N-polar crystal growth.
Implementation Method 1
The GaN layer 14 is formed on the growth substrate 12 such as a SiC substrate by means of crystal growth in the Ga-polar direction
Implementation Method 2
the AlGaN layer 16 configured as an electron supply layer is formed on the GaN layer 14 by means of epitaxial growth
Data Source
AI summary
A support substrate is bonded to a GaN epitaxial substrate including at least an electron transport layer and an electron supply layer grown on a growth substrate in the Ga-polar direction such that the support substrate faces the Ga-plane of the GaN epitaxial substrate. Furthermore, at least the growth substrate is removed from the GaN epitaxial substrate so as to expose an N-plane of the GaN epitaxial substrate. Subsequently, a semiconductor element is formed on the N-plane side.