N-Polar GaN Transistor Structure via Substrate Inversion
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Solution Overview
Problem
The preparation of high-quality N-polar GaN materials is challenging due to high surface roughness, poor crystal quality, and high impurity concentration, making it difficult to obtain a high-resistance N-polar GaN insulating layer and steep-interface heterojunction, which limits the performance of N-polar HEMT devices.
Innovation Solution
A fabrication method involving the growth of a Ga-polar epitaxial structure, followed by substrate inversion and removal, to form an N-polar GaN transistor with a high-resistance GaN insulating layer and steep-interface heterojunction, improving material quality and device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If N-polar GaN materials are directly grown on sapphire or SiC substrates by MOVPE or MBE, then the device can be fabricated, but the material quality deteriorates with high surface roughness, poor crystal quality, and high impurity concentration
Solution Approach 1:
The patent inverts the conventional growth approach by first growing high-quality Ga-polar GaN materials on suitable substrates, then bonding the grown structure to a carrier substrate, and finally removing the original substrate and buffer layer. This inversion allows obtaining N-polar GaN materials with superior crystal quality and low impurity concentration, directly resolving the material quality issue while maintaining device performance
Solution Approach 2:
The patent performs preliminary growth of high-quality Ga-polar GaN materials and formation of the active layer structure on a suitable substrate before substrate removal. By preliminarily establishing the high-quality material structure when growth conditions are optimal, the method ensures low impurity concentration and good crystal quality are achieved before the polarity inversion process
2Ease of manufacture
If N-polar GaN materials are directly grown, then the device structure can be formed, but the interface quality deteriorates with poor hetero-interface sharpness and high channel resistance
Solution Approach 1:
The patent inverts the growth sequence to grow Ga-polar materials first (which form sharp, high-quality interfaces) and then inverts the structure after bonding. This approach leverages the superior interface formation capability of Ga-polar growth while ultimately achieving N-polar device functionality with low channel resistance and sharp hetero-interfaces
3Device complexity
If conventional direct growth method is used, then the process is simpler, but the insulating layer quality deteriorates with low resistance
Solution Approach 1:
The patent inverts the conventional approach by growing the insulating layer as part of the Ga-polar structure where high-quality material growth is achieved, then inverting the entire structure. This yields N-polar insulating layers with high resistance despite the increased fabrication complexity, directly improving device reliability
Solution Approach 2:
The patent introduces a carrier substrate as an intermediary that enables the inversion process. The carrier substrate facilitates bonding, allows for controlled substrate and buffer removal, and supports the inverted structure, making the complex process feasible while achieving high-resistance insulating layers
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 results in an N-polar GaN transistor with enhanced high-voltage resistance and reduced conduction loss, surpassing the material quality of directly grown N-polar GaN materials, thus improving overall device performance.
Implementation Method 1
forming a buffer layer by depositing on one side of a structural substrate
Implementation Method 2
forming an etching-blocking barrier layer by depositing on a side of the buffer layer away from the structural substrate
Implementation Method 3
forming an epitaxial functional layer of an upside-down (inverted) N-polar transistor by depositing on a side of the etching-blocking barrier layer away from the structural substrate
Implementation Method 4
forming a support substrate by bonding on a side of the epitaxial functional layer away from the structural substrate
Data Source
AI summary
Embodiments of the present application relate to the technical field of semiconductors, and provide a manufacturing method for an N-polar GaN transistor structure and a semiconductor structure. A Ga-polar epitaxial functional layer is formed by depositing, a supporting substrate is formed on the epitaxial functional layer by bonding, after the epitaxial structure is inverted, a structural substrate and a buffer layer are removed, and a source, a drain, and a gate are manufactured on the side of the exposed epitaxial functional layer away from the supporting substrate, to form an N-polar GaN transistor structure.