Schottky Diode Integration in Trenched Power Transistors
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Solution Overview
Problem
Current trenched power semiconductor devices face switching loss issues due to the slow switching of body diodes, which result in time delays and additional losses, especially in high-frequency applications.
Innovation Solution
A fabrication method is developed to integrate a schottky diode in parallel with a trenched power transistor, where a polysilicon gate structure and a first polysilicon structure are formed on a silicon substrate, with a dielectric layer and a metal layer filled into an open to electrically connect with the source and drain regions, reducing minority carrier involvement and improving switching speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a body diode is used in the power semiconductor structure, then the device can conduct current in forward bias, but the switching speed is slow due to minority carriers causing time delays and switching loss
Solution Approach 1:
The patent combines a body diode and a schottky diode into a single integrated power semiconductor structure. The schottky diode is formed by creating a metal-semiconductor junction at the drain region, while the body diode is simultaneously formed through the intrinsic body region. This merging allows the device to utilize the fast switching characteristics of the schottky diode while maintaining the current conduction capability of the body diode, thereby resolving the contradiction between reliability and switching speed.
Solution Approach 2:
The patent introduces a schottky diode as an intermediary component to improve switching performance. The schottky diode acts as a mediator that provides a low-inductance current path during switching transitions, bypassing the slow minority carrier effects of the body diode. This intermediary structure enables fast switching while the body diode continues to provide reliable current conduction, thus resolving the speed-reliability contradiction.
2Speed
If a schottky diode is added in parallel with the MOS transistor to improve switching speed, then switching loss is reduced, but the device complexity increases
Solution Approach 1:
The patent merges the schottky diode formation process with the existing MOS transistor fabrication steps. The schottky diode is formed by depositing metal contacts on the drain region during the same processing sequence used for creating the power transistor terminals. This integration eliminates the need for separate schottky diode fabrication steps, thereby reducing device complexity while achieving improved switching speed.
Solution Approach 2:
The patent designs the power semiconductor structure to serve multiple functions simultaneously. The same metal contact structures serve dual purposes: as terminals for the MOS transistor and as electrodes for the schottky diode. The body region serves both as the channel formation area for the MOS transistor and as the intrinsic region for the body diode. This multi-functionality reduces overall device complexity while enabling fast switching through the integrated schottky diode.
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 integration of a schottky diode in the power semiconductor structure reduces switching loss and time delays, enhancing the switching speed and performance of trenched power semiconductor devices in high-frequency applications.
Implementation Method 1
a metal layer is filled in the open... The integration of a schottky diode in the power semiconductor structure reduces switching loss and time delays
Data Source
AI summary
A power semiconductor structure with schottky diode is provided. In the step of forming the gate structure, a separated first polysilicon structure is also formed on the silicon substrate. Then, the silicon substrate is implanted with dopants by using the first polysilicon structure as a mask to form a body and a source region. Afterward, a dielectric layer is deposited on the silicon substrate and an open penetrating the dielectric layer and the first polysilicon structure is formed so as to expose the source region and the drain region below the body. The depth of the open is smaller than the greatest depth of the body. Then, a metal layer is filled into the open to electrically connect to the source region and the drain region.