Radiation-Hardened SiC Drift Layer for Low-Resistance High-Voltage Blocking
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Solution Overview
Problem
Conventional semiconductor power devices, such as silicon carbide (SiC) MOSFETs, are susceptible to single event effects and failure at high blocking voltages due to radiation intolerance, leading to device failure from events like heavy ion, beta, or neutron strikes, and existing solutions like derating and buffer layers increase on-state resistance losses and manufacturing complexity.
Innovation Solution
A radiation hardened semiconductor device is designed with a heavily doped and thick drift layer, maintaining a doping concentration between 1×10^15 cm^-3 and 1.5×10^16 cm^-3 and thickness between 15 μm and 200 μm, which allows the device to block high voltages while minimizing on-state resistance losses and surviving radiation events by keeping the drift layer substantially less depleted than in conventional designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SiC power devices are used, then high-power applications are enabled, but radiation intolerance causes single event burnout and failure at high blocking voltages
Solution Approach 1:
The patent changes the electrical parameters of the drift layer by introducing a graded doping profile where the doping concentration increases with depth from the surface. This parameter change creates a more favorable electric field distribution that prevents single event burnout while maintaining high blocking voltage capability, directly resolving the radiation tolerance contradiction.
Solution Approach 2:
The patent applies local quality by creating a non-uniform doping distribution within the drift layer, where different regions have different doping concentrations. The surface region has lower doping while deeper regions have higher doping, optimizing each region's function: the surface region minimizes on-state resistance while the deeper regions provide radiation hardness and high voltage blocking.
2Reliability
If derating is applied to improve radiation hardness, then device survives radiation events, but on-state resistance losses increase
Solution Approach 1:
Instead of derating the device, the patent changes the drift layer doping profile parameters to achieve both radiation hardness and low on-state resistance simultaneously. The graded profile allows the device to operate at its rated voltage while maintaining radiation tolerance, eliminating the need for derating and its associated energy losses.
3Reliability
If buffer layers are added to harden against radiation, then radiation tolerance improves, but manufacturing complexity increases
Solution Approach 1:
The patent merges the radiation hardening function into the existing drift layer by creating a graded doping profile within it, rather than adding a separate buffer layer. This integration maintains the device's structural simplicity and manufacturing ease while achieving the desired radiation tolerance, resolving the complexity contradiction.
4Strength
If drift layer thickness is increased to block high voltages, then blocking voltage capability improves, but on-state resistance losses increase
Solution Approach 1:
The patent changes the doping concentration parameter as a function of depth within the drift layer. By increasing doping concentration toward the substrate, the electric field is better distributed, allowing high blocking voltage capability with reduced on-state resistance losses compared to uniform doping profiles.
Solution Approach 2:
The patent applies local quality by creating regions of different doping concentrations within the drift layer. The graded profile optimizes each region's contribution: lower doping near the surface reduces on-state resistance while higher doping deeper in the layer enhances voltage blocking capability.
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 device effectively blocks high voltages and survives radiation events with reduced on-state resistance losses, offering improved reliability and cost-effectiveness compared to derated or buffer-layer-based solutions, as the thick drift layer prevents complete depletion and maintains lower resistance.
Implementation Method 1
the drift layer having a doping concentration and a thickness such that when the semiconductor device is operating at a predetermined target operating voltage, an electrical field profile in the drift layer extends less than 80% of the thickness of the drift layer
Data Source
AI summary
A radiation hardened semiconductor device including a heavily doped substrate of a semiconductor device, a drift layer having a substantially uniform doping concentration and a thickness is provided. The doping concentration and the thickness of the drift layer are such that when the semiconductor device is operating at a maximum voltage rating, an electrical field profile in the drift layer extends less than 80% of the thickness of the drift layer, providing the radiation hardened nature of the device.