SiC Device Hermetic Packaging for NBTI Mitigation

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Solution Overview

Problem

Silicon carbide (SiC) semiconductor devices face significant reliability and performance issues due to negative bias temperature instability (NBTI), which causes threshold voltage shifts, transforming normally-off devices into normally-on devices, and existing solutions for silicon devices do not effectively translate to SiC devices.

Innovation Solution

A hermetically sealed packaging system that maintains a reduced pressure or inert atmosphere around SiC semiconductor devices, such as a vacuum or inert gas environment, to inhibit NBTI and reduce threshold voltage shifts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If SiC devices are operated at elevated temperatures and biases, then device performance is improved, but NBTI causes threshold voltage shifts that degrade reliability

Engineering Contradiction:

Improveoperating temperatureVSAvoidthreshold voltage stability

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent applies an inert atmosphere (vacuum or inert gas) inside a hermetically sealed package to isolate the SiC device from reactive environmental species. This inert environment prevents oxidation and chemical reactions at the oxide-semiconductor interface that would otherwise be accelerated by elevated temperatures, thereby maintaining threshold voltage stability while allowing the device to operate at high temperatures for improved performance

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

2Reliability

If hermetically sealed packaging is used to maintain inert atmosphere, then NBTI is reduced, but device complexity increases

Engineering Contradiction:

Improvethreshold voltage stabilityVSAvoidpackaging structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs a hermetically sealed package containing an inert atmosphere (vacuum or inert gas) to prevent NBTI effects. While this does increase packaging complexity compared to conventional open devices, it provides a robust solution for maintaining threshold voltage stability in high-temperature applications where the added complexity is justified by the significant reliability improvement

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

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

Substantially reduces NBTI effects in SiC devices, limiting threshold voltage shifts to less than 1 V, thereby enhancing device reliability and performance, and allowing SiC devices to operate effectively at elevated temperatures.

Implementation Method 1

negative bias temperature instability (NBTI), which causes threshold voltage shifts

Methodology Applied

Scientific EffectNegative bias temperature instability (NBTI):

Implementation Method 2

The NBTI in SiC devices is thought to be a result of interfacial charge trapping (e.g., oxide charges)

Methodology Applied

Scientific EffectInterfacial charge trapping:

Data Source

PatentUS9576868B2Semiconductor device and method for reduced bias temperature instability (BTI) in silicon carbide devices

Publication Date: 2017.02.21 GENERAL ELECTRIC CO

AI summary

A system includes a silicon carbide (SiC) semiconductor device and a hermetically sealed packaging enclosing the SiC semiconductor device. The hermetically sealed packaging is configured to maintain a particular atmosphere near the SiC semiconductor device. Further, the particular atmosphere limits a shift in a threshold voltage of the SiC semiconductor device to less than 1 V during operation.