IGBT Trench Gate Stability via Silicon Nitride Hydrogen Termination
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Solution Overview
Problem
The existing semiconductor devices face variations in threshold voltage of trench gates due to interface states formed between the gate insulating film and the semiconductor substrate, which affect the reverse recovery characteristics of the diode region.
Innovation Solution
A semiconductor device with a lifetime control region having a peak of crystal defect density is positioned between the trench gate and the body layer, and a silicon nitride film or an Al-based electrode layer is used to supply hydrogen atoms, reducing interface states and stabilizing the threshold voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lifetime control region is provided at a position in the drift layer that is as close as possible to the boundary between the body layer and the drift layer to improve reverse recovery characteristics, then the reverse recovery characteristics are improved, but interface states are formed between the gate insulating film and the semiconductor substrate, causing variations in threshold voltage of trench gates
Solution Approach 1:
A silicon nitride film is introduced as an intermediary layer between the gate insulating film and the lifetime control region. This film acts as a mediator that prevents direct interaction between the gate insulating film and the high-density crystal defects in the lifetime control region, thereby eliminating interface states while allowing the lifetime control region to maintain its position for optimal reverse recovery characteristics.
Solution Approach 2:
The high crystal defect density in the lifetime control region, which would normally create harmful interface states, is converted into a beneficial structure by introducing the silicon nitride film. The film transforms the potentially harmful interface into a controlled structure where the lifetime control region can fulfill its function of improving reverse recovery characteristics without causing threshold voltage variations.
2Manufacturing precision
If the lifetime control region is positioned deeper in the drift layer to avoid overlap with the trench gate, then threshold voltage variation is reduced, but reverse recovery characteristics deteriorate
Solution Approach 1:
The silicon nitride film serves as a protective intermediary that enables the lifetime control region to be positioned at the optimal depth (close to the body layer boundary) without creating harmful interface states. This resolves the need to compromise on depth positioning by eliminating the harmful interaction that would otherwise occur.
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
This configuration effectively reduces threshold voltage variations and improves the reverse recovery characteristics of the diode region by terminating and reducing interface states through hydrogen termination.
Implementation Method 1
hydrogen atoms are supplied from the silicon nitride film provided above the trench gate on the front surface side of the semiconductor substrate and an interface state is terminated and reduced by hydrogen
Implementation Method 2
A lifetime control region which includes a peak of a crystal defect density is provided in the first drift layer and the second drift layer
Data Source
AI summary
An IGBT region includes a collector layer, a first drift layer, a first body layer, an emitter layer, and a trench gate reaching the first drift layer through the first body layer from a front surface side of a semiconductor substrate. A diode region includes a cathode layer, a second drift layer, and a second body layer. A lifetime control region which includes a peak of a crystal defect density is provided in the first drift layer and the second drift layer that are located between a depth of a lower end of the trench gate and surfaces of the first drift layer and the second drift layer. A silicon nitride film is further provided above the trench gate on the front surface side of the semiconductor substrate.