SiC Superjunction Drift Region with Angled Channeled Doping
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Solution Overview
Problem
Conventional methods for forming superjunction-type drift regions in silicon carbide power semiconductor devices face challenges such as breakdown voltage issues due to carrier tunneling and non-uniform dopant incorporation, particularly in high bandgap materials like silicon carbide, where conventional fabrication techniques like trench refill and thermal diffusion are inefficient.
Innovation Solution
The approach involves ion implantation along specific crystallographic axes, such as the crystallographic axis, to create deeply doped pillars with channeling techniques, allowing for deeper and more uniform dopant implantation with reduced lattice damage, thereby enhancing the depth and uniformity of the superjunction structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional trench refill or thermal diffusion methods are used to form superjunction drift regions in silicon carbide, then the fabrication process can be completed, but the dopant incorporation is non-uniform and carrier tunneling causes breakdown voltage issues
Solution Approach 1:
The patent changes the ion implantation parameters by aligning the ion beam along specific crystallographic axes (such as the <0001> axis) of the silicon carbide wafer. This parameter change enables channeling effects that dramatically improve dopant penetration depth and uniformity, resolving the contradiction between manufacturing precision and reliability by achieving both deep, uniform doping and high breakdown voltage through controlled carrier distribution
Solution Approach 2:
The patent replaces conventional thermal diffusion or trench refill methods with ion implantation along crystallographic channels. This substitution uses the channeling effect—a quantum mechanical phenomenon where ions travel through crystal lattice channels with minimal scattering—to achieve uniform deep doping without the non-uniformity and carrier tunneling issues associated with conventional thermal or mechanical refill processes
2Length of moving object
If ion implantation is performed without channeling techniques, then the fabrication process is simpler, but dopant penetration depth is insufficient for high voltage devices
Solution Approach 1:
The patent changes the implantation geometry parameter by aligning the ion beam direction with crystallographic axes of the silicon carbide wafer. This simple parameter change—rotating the wafer or adjusting the beam angle to match crystallographic directions—enables channeling effects that increase dopant penetration depth by micrometers without adding complex fabrication steps, maintaining process simplicity while achieving the required doping depth for high voltage devices
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 achieves higher breakdown voltages and lower on-state resistance in silicon carbide power semiconductor devices by optimizing the implantation depth and uniformity of dopants, making the process more cost-effective and scalable.
Implementation Method 1
The approach involves ion implantation along specific crystallographic axes, such as the <0001> crystallographic axis, to create deeply doped pillars with channeling techniques
Implementation Method 2
allowing for deeper and more uniform dopant implantation with reduced lattice damage, thereby enhancing the depth and uniformity of the superjunction structure
Data Source
AI summary
Semiconductor devices include a silicon carbide drift region having an upper portion and a lower portion. A first contact is on the upper portion of the drift region and a second contact is on the lower portion of the drift region. The drift region includes a superjunction structure that includes a p-n junction that is formed at an angle of between 10° and 30° from a plane that is normal to a top surface of the drift region. The p-n junction extends within +/−1.5° of a crystallographic axis of the silicon carbide material forming the drift region.