SiC Junction Termination via Graded Diffusion
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Solution Overview
Problem
Conventional edge termination techniques for high-voltage silicon carbide (SiC) devices, such as field plate terminations, are unsuitable due to high electric fields at the oxide-semiconductor interface, leading to reliability issues, and existing junction termination extension (JTE) methods require complex multi-step implantation processes and may not provide ideal termination.
Innovation Solution
A method for forming a junction termination extension with a smoothly graded doping profile in silicon carbide devices using controlled diffusion of dopants through a mask with strategically designed openings, allowing for a single masking step and a single drive-in diffusion step to create a doped region with decreasing dopant concentration laterally and vertically from the main junction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If field plate termination is used, then cost-effectiveness is improved, but reliability deteriorates due to high oxide fields at the oxide-semiconductor interface
Solution Approach 1:
The patent removes the oxide layer from the field plate structure, extracting the harmful component (oxide) that causes high electric fields and reliability issues. The field plate is implemented without requiring an oxide layer, thereby eliminating the root cause of the reliability problem while maintaining the cost-effectiveness of the field plate approach
Solution Approach 2:
The patent converts the harmful high electric field effect at the oxide-semiconductor interface into a beneficial distributed field termination effect by using the metal field plate directly on the semiconductor surface. The field plate structure, when implemented without oxide, creates a gradual field distribution that terminates high electric fields effectively without causing oxide breakdown
2Manufacturing precision
If conventional JTE methods with multi-step implantation are used, then doping profile control is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple implantation steps and masking operations into a single implantation step with a specially designed mask. The mask contains multiple openings of varying sizes that allow a single implantation event to create the complex graded doping profile that previously required multiple sequential implantation steps, thereby reducing process complexity while maintaining doping profile control
Solution Approach 2:
The patent performs preliminary action by designing a specialized mask with strategically positioned openings of different sizes before the implantation process. This pre-planned mask structure enables the single implantation step to deposit dopants in a pattern that automatically creates the desired graded doping profile, eliminating the need for multiple implantation steps with different doses
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 approach provides superior junction termination characteristics with reduced complexity and cost, achieving a linearly graded doping profile that extends effectively from the main junction, enhancing the reliability and performance of SiC devices by reducing sensitivity to implant dose variations and oxide field stresses.
Implementation Method 1
second conductivity type dopants are diffused into the silicon carbide layer to form doped regions in the silicon carbide layer corresponding to respective ones of the mask openings
Data Source
AI summary
An electronic device includes a silicon carbide layer having a first conductivity type and a main junction adjacent a surface of the silicon carbide layer, and a junction termination region at the surface of the silicon carbide layer adjacent the main junction. Charge in the junction termination region decreases with lateral distance from the main junction, and a maximum charge in the junction termination region may be less than about 2×1014 cm−2.