Power Semiconductor Device Charge Balance Cosmic Ray Robustness
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Solution Overview
Problem
Power semiconductor devices, particularly those used in switching applications, are vulnerable to cosmic ray radiation, which can cause irreversible failure due to high electric field gradients, and existing methods to enhance cosmic ray robustness often result in electrical performance trade-offs such as higher on-state losses and poorer diode reverse recovery.
Innovation Solution
A vertical trenched gate transistor structure is developed with a doped superjunction region at the bottom of the gate trench, comprising doped pillars of alternating conductivity type, which extends no more than halfway into the drift region, reducing high electric fields and improving electrical performance while maintaining robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If techniques are used to tailor the electric field profile to improve cosmic ray robustness (increasing wafer thickness, introducing graded base material, reducing doping concentration, optimizing field-stop layer, using deeper p-type junctions, thickening gate trench oxide), then device robustness against cosmic ray radiation is improved, but electrical performance deteriorates with poorer diode reverse recovery softness and higher on-state losses
Solution Approach 1:
The patent introduces a doped superjunction region with alternating conductivity type pillars that changes the electric field distribution parameters. This creates a more uniform electric field profile that reduces peak fields without requiring the conventional approaches that degrade electrical performance. The superjunction structure achieves cosmic ray hardening through parameter optimization rather than structural modifications that harm electrical characteristics.
Solution Approach 2:
The doped superjunction region forms a composite structure with alternating p-type and n-type pillars within the drift region. This composite doping structure creates beneficial electric field distribution that simultaneously improves cosmic ray robustness and maintains electrical performance, avoiding the trade-offs of conventional single-type doping approaches.
2Reliability
If techniques are used to tailor the electric field profile to improve cosmic ray robustness, then device robustness against cosmic ray radiation is improved, but diode reverse recovery performance deteriorates with poorer softness
Solution Approach 1:
The doped superjunction region modifies the electric field distribution parameters to achieve a more uniform profile during reverse recovery. This parameter optimization allows for softer reverse recovery characteristics while simultaneously providing cosmic ray hardening, resolving the contradiction between reliability improvement and electrical performance degradation.
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 doped superjunction region enhances the device's robustness against cosmic ray radiation, improves switching losses and speed, and maintains desirable breakdown voltage and on-resistance, with more cost-effective and controllable processing compared to prior art techniques.
Implementation Method 1
The doped superjunction region vertically extending into the drift region from a bottom of the gate trench reduces high electric fields
Implementation Method 2
A gate dielectric that is disposed in the gate trench is formed. The gate dialectic electrically insulates the gate electrode from adjacent semiconductor material.
Data Source
AI summary
A semiconductor body having first and second vertically spaced apart surfaces is formed. A gate trench that vertically extends from the first surface of the semiconductor body towards the second surface is formed. A gate electrode and a gate dielectric are formed in the gate trench. The gate dielectric electrically insulates the gate electrode from adjacent semiconductor material. A doped superjunction region vertically extending from a bottom of the gate trench towards the second surface of the semiconductor body is formed. The doped superjunction region includes first, second, and third doped pillars vertically extending from the first surface of the first semiconductor layer and directly adjoining one another. The second pillar is laterally centered between the first and third pillars and has an opposite conductivity type as the first and third pillars.