Trench Gate Semiconductor Device dV/dt Control
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Solution Overview
Problem
Existing semiconductor devices face a trade-off between improving dV/dt controllability and reducing losses during the turn-off switching period, with methods either increasing ON-voltage or decreasing breakdown voltage, and there is a need for a solution that maintains low loss and high breakdown voltage.
Innovation Solution
A semiconductor device with a wide trench structure and a polysilicon electrode connected to the emitter electrode, which reduces feedback capacity and enhances breakdown voltage by dispersing the electric field, while omitting the floating p-layer to improve dV/dt controllability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a floating p-layer is electrically connected to the emitter electrode through a resistance to improve dV/dt controllability, then the controllability of dV/dt increases, but the ON-voltage increases and loss increases
Solution Approach 1:
The invention extracts and removes the floating p-layer from the semiconductor device structure. By eliminating this layer entirely rather than connecting it through a resistance, the device avoids the trade-off between dV/dt controllability and loss, achieving both improved controllability and reduced energy loss.
Solution Approach 2:
The invention changes the structural dimension by transitioning from a planar structure with a floating p-layer to a trench gate structure. This dimensional change allows the gate electrode to be positioned in a trench, creating a different electric field distribution that improves dV/dt controllability without the need for a floating p-layer connection, thereby reducing loss.
2Loss of energy
If the resistance between the floating p-layer and emitter electrode is increased to reduce ON-voltage increase, then the ON-voltage increase becomes small, but the controllability of dV/dt decreases
Solution Approach 1:
The invention removes the floating p-layer entirely from the device structure, eliminating the need to choose an optimal resistance value. This extraction resolves the contradiction by providing a different mechanism for dV/dt control through the trench gate structure, achieving both low loss and high controllability.
Solution Approach 2:
The invention changes the structural parameters by introducing a trench gate configuration with specific width and depth dimensions. This parameter change creates a different electric field distribution that provides superior dV/dt controllability compared to the floating p-layer approach, while maintaining low ON-voltage and loss.
3Productivity
If a trench structure is formed to increase switching speed and reduce switching loss, then the switching speed increases, but the breakdown voltage may decrease due to electric field concentration at trench corners
Solution Approach 1:
The invention applies local quality by creating a specific trench geometry where the gate electrode is positioned within the trench. The trench width is controlled to be a specific proportion of the drift layer thickness, creating a localized electric field distribution that avoids concentration at corners while maintaining high switching speed and preventing breakdown.
Solution Approach 2:
The invention uses a curved or rounded trench profile rather than sharp corners. This curvature eliminates electric field concentration at the trench corners, preventing breakdown while maintaining the high switching speed benefits of the trench structure. The rounded profile distributes the electric field more uniformly.
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 improves dV/dt controllability during the turn-off switching period while maintaining low loss and high breakdown voltage, reducing feedback capacity and suppressing potential rise, thus balancing controllability and reliability.
Implementation Method 1
a polysilicon electrode connected to the emitter electrode, which reduces feedback capacity and enhances breakdown voltage by dispersing the electric field
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A semiconductor device which includes: a first semiconductor layer (4) of a first conductivity type; a second semiconductor layer (2) of a second conductivity type that is formed near a surface of the first semiconductor layer (4); a first main electrode (11) that is electrically connected to the second semiconductor layer (2); a third semiconductor layer (6) of the second conductivity type that neighbors the first semiconductor layer (4) and is formed near a surface of the first semiconductor layer (4) opposite to the second semiconductor layer (2); a fourth semiconductor layer (7) of the first conductivity type that is selectively disposed in an upper portion of the third semiconductor layer (6); a second main electrode (14) that is electrically connected to the third semiconductor layer (6) and the fourth semiconductor layer (7); a trench (17) whose side face is in contact with the third semiconductor layer (6) and the fourth semiconductor layer (7), while reaching the first semiconductor layer (4); a gate electrode (9) that is formed along the side face of the trench (17) by a sidewall of polysilicon; and a polysilicon electrode (18) that is disposed away from the gate electrode (9) within the trench (17) and electrically connected to the second main electrode (14).