SiC-Nitride Epitaxial Structure for Low Capacitance and Crack Control
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Solution Overview
Problem
Nitride semiconductor devices using conductive SiC substrates face challenges with substrate warping, internal cracking of epitaxial layers, and high parasitic capacitance, which are not effectively addressed by existing technologies.
Innovation Solution
A nitride semiconductor device is designed with a conductive SiC substrate, a semi-insulating SiC layer, and a nitride epitaxial layer, where the semi-insulating SiC layer is formed on the substrate surface, and the nitride epitaxial layer is grown to cover this layer, reducing parasitic capacitance and preventing warping and cracking, with specific layer configurations and manufacturing steps to achieve optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conductive SiC substrate is used to reduce parasitic capacitance, then parasitic capacitance is reduced, but substrate warping and internal cracking occur
Solution Approach 1:
The patent employs a composite structure consisting of a conductive SiC substrate combined with a semi-insulating SiC layer. This composite material approach allows the device to benefit from the low parasitic capacitance of the conductive SiC substrate while the semi-insulating SiC layer compensates for mechanical instability, preventing warping and internal cracking.
Solution Approach 2:
The semi-insulating SiC layer acts as an intermediary between the conductive SiC substrate and the nitride epitaxial layer. This intermediate layer mediates the mechanical stress and thermal expansion differences, preventing direct transmission of stress that would cause warping and cracking in the epitaxial layer.
2Object-affected harmful factors
If an SiC substrate is used as a semiconductor substrate, then parasitic capacitance is reduced, but manufacturing complexity increases
Solution Approach 1:
The semi-insulating SiC layer serves multiple functions simultaneously: it provides mechanical support to prevent substrate warping, acts as a stress buffer to prevent internal cracking, and maintains the low parasitic capacitance characteristic of SiC substrates. This multi-functionality reduces the need for additional separate components.
3Reliability
If a nitride epitaxial layer is grown on a conductive SiC substrate, then device performance is improved, but internal cracking occurs
Solution Approach 1:
The semi-insulating SiC layer is formed on the conductive SiC substrate before growing the nitride epitaxial layer. This pre-positioned layer acts as a cushion that absorbs and distributes mechanical stress during the epitaxial growth process, preventing internal cracking before it can occur in the nitride layer.
Solution Approach 2:
The patent changes the physical and mechanical parameters of the substrate structure by introducing a semi-insulating SiC layer with different mechanical properties than the conductive SiC substrate. This parameter change creates a gradient structure that better accommodates thermal and mechanical stress during epitaxial growth.
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 solution effectively suppresses warping of the SiC substrate and internal cracking of the nitride epitaxial layer while reducing parasitic capacitance, enhancing the reliability and performance of the nitride semiconductor device.
Implementation Method 1
a semi-insulating SiC layer that is formed in at least a portion of a surface layer portion at a first surface side of the conductive SiC substrate
Implementation Method 2
a nitride epitaxial layer that is formed on the conductive SiC substrate such as to cover the semi-insulating SiC layer
Data Source
AI summary
A nitride semiconductor device 1 includes a conductive SiC substrate 2 that has a first surface 2a and a second surface 2b opposite thereto, a semi-insulating SiC layer 3 that is formed in at least a portion of a surface layer portion at the first surface 2a side of the conductive SiC substrate 2, and a nitride epitaxial layer 40 that is formed on the conductive SiC substrate 2 such as to cover the semi-insulating SiC layer 3.