Transistor Field Electrode Coupling Circuit for Voltage Spike Suppression
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Solution Overview
Problem
Transistor devices with field electrode structures face significant voltage spikes during transitions from conducting to blocking states due to parasitic oscillations, which can exceed their voltage blocking capability, potentially damaging the device and increasing conduction losses.
Innovation Solution
A transistor device with a field electrode structure that includes a first and second field electrode, both dielectrically insulated from the drift region, and a coupling circuit connecting the second field electrode to the source node based on voltage conditions, reducing output capacitance and voltage overshoots by controlling the connection of the second field electrode to the source node.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the voltage blocking capability is increased to withstand voltage spikes, then device reliability is improved, but conduction losses and device price increase
Solution Approach 1:
The field electrode structure implements dynamic voltage distribution during switching transitions. The field electrodes are configured to create a time-varying electric field that adapts to the switching state, providing enhanced voltage blocking during transitions while maintaining lower on-resistance in the conducting state. This dynamic approach allows the device to withstand voltage spikes without requiring excessive voltage blocking capability in the steady state.
Solution Approach 2:
The invention changes the electrical parameters of the drift region by introducing field electrodes that modify the electric field distribution. The field electrodes create a non-uniform electric field that increases the effective breakdown voltage during switching transitions. By controlling the doping concentration and geometry of the field electrodes, the device achieves improved voltage blocking capability during transitions without proportionally increasing the on-resistance in the conducting state.
2Duration of action of moving object
If the output capacitance is reduced to decrease oscillation duration, then switching speed is improved, but voltage spikes may increase
Solution Approach 1:
The field electrodes act as intermediary elements between the drain and source regions, creating a distributed capacitance structure. This intermediary field electrode structure modifies the capacitive coupling during switching transitions, reducing the effective output capacitance that participates in parasitic oscillations. The field electrodes provide a gradual voltage transition path that suppresses voltage spikes while maintaining reduced oscillation duration.
3Loss of energy
If a field electrode structure is added to reduce on-resistance, then conductivity is improved, but device complexity increases
Solution Approach 1:
The field electrode structure is segmented into multiple discrete field electrodes distributed along the drift region. This segmentation allows the complex function of voltage blocking and field control to be distributed across multiple simpler elements. Each field electrode can be independently optimized for local field control, reducing the overall complexity compared to a single complex electrode structure while achieving lower on-resistance through the distributed field effect.
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 reduces the amplitude and duration of parasitic oscillations, enhancing the transistor's voltage blocking capability without increasing on-resistance, thereby protecting the device and minimizing conduction losses.
Implementation Method 1
a gate electrode dielectrically insulated from the body region by a gate dielectric
Implementation Method 2
a first field electrode connected to the source node and dielectrically insulated from the drift region by a first field electrode dielectric
Implementation Method 3
a coupling circuit connected between the second field electrode and the source node. The coupling circuit is configured to connect the second field electrode to the source node dependent on a voltage between the source node and the second field electrode
Data Source
Figure 1~3
Figure 4~5
Figure 6~8
AI summary
A transistor device is disclosed. The transistor device includes, in a semiconductor body (100), a drift region (11), a body region (12), and a source region (13) separated from the drift region (11) by the body region (12) and connected to a source node (S); a drain region (14) spaced apart from the body region (12); a gate electrode (21) dielectrically insulated from the body region (12) by a gate dielectric (22); and a field electrode structure (3). The field electrode structure includes a first field electrode (31) connected to the source node (S) and dielectrically insulated from the drift region (11) by a first field electrode dielectric (33); a second field electrode (32) dielectrically insulated from the drift region (11) by a second field electrode dielectric (33) and located closer to the drain region (14) than the first field electrode (31); and a coupling circuit (4) connected between the second field electrode (32) and the source node (S) and configured to connect the second field electrode (32) to the source node (S) dependent on a voltage between the source node (S) and the second field electrode (32).