SiC Insulated Gate Trench Injection Suppression Structure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Silicon carbide (SiC) MISFETs face higher ON resistance and reliability issues due to bipolar operation of the body diode, with existing solutions like polysilicon barrier-forming layers having weak electric field strength and separate manufacturing steps, and Schottky junction diodes having higher ON resistance.
Innovation Solution
An insulated gate semiconductor device with a trench gate structure, including a charge transport region, injection control region, main electrode contact region, insulated gate electrode, injection suppression region, and contact protection region, where the injection suppression region has a narrower bandgap than the charge transport region, and the gate electrode is embedded with a gate insulating film, suppressing bipolar operation and reducing ON resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polysilicon barrier-forming layer is used to suppress bipolar operation, then bipolar operation is suppressed, but the electric field strength is weak and manufacturing steps increase
Solution Approach 1:
The gate electrode and barrier-forming layer are merged into a single integrated structure. The gate electrode is formed of a first semiconductor material (e.g., SiC) while the barrier-forming layer is formed of a second semiconductor material (e.g., Si) with a narrower bandgap, both within the same trench structure. This integration eliminates separate manufacturing steps while maintaining the suppression of bipolar operation through the heterojunction barrier.
Solution Approach 2:
The gate structure uses composite materials consisting of two different semiconductor materials with different bandgaps. The first semiconductor material (SiC) provides high breakdown voltage and low ON resistance, while the second semiconductor material (Si) provides the barrier function to suppress bipolar operation. This composite structure achieves both electrical performance and manufacturing simplicity.
2Reliability
If a Schottky junction diode is used, then bipolar operation is suppressed, but ON resistance increases
Solution Approach 1:
The barrier function is localized to the heterojunction interface between the first and second semiconductor materials at the gate structure. The main current path through the drift region maintains low resistance because it flows through the high-quality first semiconductor material (SiC) without being impeded by the barrier layer, which only affects minority carrier injection at the gate interface.
3Reliability
If a heterojunction with narrower bandgap material is used, then bipolar operation is suppressed and ON resistance is reduced, but manufacturing complexity increases
Solution Approach 1:
The gate electrode and barrier-forming layer are formed simultaneously or in an integrated sequence within the same trench during the manufacturing process. This merging of structures eliminates multiple separate fabrication steps while achieving the dual functionality of gate control and bipolar operation suppression through the heterojunction.
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 solution effectively suppresses bipolar operation, reduces ON resistance, and enhances reliability by controlling surface potential and minority carrier injection, while maintaining high withstand voltage.
Implementation Method 1
an injection suppression structure that has a contact trench penetrating from the top of the main electrode contact region through the main electrode contact region and the injection control region in the depth direction and reaching the charge transport region, and an injection suppression region filling in the trench, the injection suppression structure being disposed at a position laterally separated from the insulating gate structure in a plan view, the injection suppression region including a second semiconductor material having a narrower bandgap than a bandgap of the first semiconductor material of the charge transport region
Implementation Method 2
a gate electrode embedded in the trench with a gate insulating film interposed between the gate electrode and the trench, the insulated gate electrode structure controlling a surface potential of the injection control region
Data Source
AI summary
A method of manufacturing an insulated gate semiconductor device includes simultaneously forming a gate trench and a contact trench that respectively penetrate form a top of the electrode contact region through a main electrode contact region and a injection control region in a depth direction and respectively reach a charge transport region, the contact trench being disposed at a position laterally separated from the gate trench in a plan view; and embedding a gate electrode inside the gate trench with a gate insulating film interposed therebetween, thereby forming an insulated gate structure, and simultaneously embedding an injection suppression region inside the contact trench, the gate electrode and the injection suppression region being both made of a second semiconductor material having a narrower bandgap than a bandgap of the first semiconductor material of the charge transport region.