SiC MISFET Interface Nitrogen Fluorine Termination
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Solution Overview
Problem
The high on-resistance of metal insulator semiconductor field effect transistors (MISFETs) and insulated gate bipolar transistors (IGBTs) using silicon carbide (SiC) is attributed to a larger number of interface states between the semiconductor and insulating film, which reduces charge mobility due to increased interface states caused by the MIS structure.
Innovation Solution
A semiconductor device with a SiC layer, a gate electrode, and a gate insulating layer, featuring a first interface region with peak nitrogen and fluorine concentration distributions to terminate dangling bonds, reducing interface states and enhancing mobility, and a second interface region with fluorine concentration to improve reliability and reduce threshold voltage variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a metal insulator semiconductor (MIS) structure is formed using SiC, then the device can operate at high temperature with excellent physical properties, but the amount of interface state increases, reducing charge mobility and increasing on-resistance
Solution Approach 1:
The patent applies local quality by creating a nitrogen-rich interface region specifically at the SiC-semiconductor substrate boundary. This localized nitrogen enrichment terminates dangling bonds at the interface, reducing interface states and improving charge mobility in the critical region where electrons traverse, without affecting the bulk SiC material properties that enable high-temperature operation.
Solution Approach 2:
The patent changes the chemical composition parameter by introducing nitrogen into the SiC layer at the interface region. This parameter change (adding nitrogen) modifies the electronic structure to reduce interface states, thereby improving charge mobility while preserving the high-temperature operational characteristics of SiC.
2Reliability
If nitrogen is added to the SiC layer to terminate dangling bonds, then interface states are reduced and charge mobility is improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating nitrogen into the SiC layer during the epitaxial growth process, before device fabrication begins. This preliminary nitrogen incorporation eliminates the need for subsequent complex nitrogen implantation and annealing steps that would otherwise be required, thereby reducing manufacturing process complexity while achieving the desired interface state reduction.
Solution Approach 2:
The patent merges the nitrogen introduction step with the SiC epitaxial growth process. By combining these two processes, the nitrogen is incorporated into the SiC layer in a single manufacturing step, reducing the total number of process steps and simplifying the overall manufacturing complexity compared to separate nitrogen implantation and annealing processes.
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 approach effectively reduces interface states, enhances charge mobility, and improves the reliability of MISFETs and IGBTs by terminating dangling bonds with nitrogen and fluorine, resulting in high-performance devices with reduced on-resistance and increased operational stability.
Implementation Method 1
a first interface region, having a peak of nitrogen (N) concentration distribution and a peak of fluorine (F) concentration distribution
Data Source
AI summary
A semiconductor device of an embodiment includes a SiC layer, a gate electrode, a gate insulating layer provided between the SiC layer and the gate electrode, and a first region provided between the SiC layer and the gate insulating layer and having a peak of nitrogen (N) concentration distribution and a peak of fluorine (F) concentration distribution.