Embedded Schottky MOSFET Layout for Faster SiC Switching
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Solution Overview
Problem
Existing semiconductor devices, such as silicon carbide MOSFETs, have large cell pitches, leading to increased size, lower chip density, higher costs, and reduced switching speed, making them unsuitable for high-speed applications due to the limitations of body diodes with high turn-on voltages.
Innovation Solution
A semiconductor device with an embedded Schottky diode is designed, featuring a substrate with a well region, source region, contact region, and Schottky region, where the Schottky diode is formed by a portion of the source metal layer contacting the Schottky region, surrounded by the well and contact regions, allowing for a self-aligning method to embed the Schottky diode without additional process steps or expensive masks, thereby improving device performance and reducing body diode turn-on voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional body diode structure is used, then the device can be manufactured with existing processes, but the turn-on voltage is high and switching speed is reduced
Solution Approach 1:
The patent changes the fundamental parameter of the diode structure by replacing the conventional body diode with a Schottky diode. This involves changing the material composition (using Schottky contact metal instead of diffused junction) and the electrical characteristics (lower turn-on voltage, faster switching). The Schottky diode is formed by depositing a metal layer that creates a Schottky barrier with the semiconductor substrate, fundamentally altering the diode's electrical parameters to achieve lower turn-on voltage and higher switching speed while remaining compatible with existing manufacturing processes.
2Area of stationary object
If the cell pitch is reduced to increase chip density, then the device size decreases and chip density increases, but the existing device structures have many shortcomings
Solution Approach 1:
The patent segments the device structure into distinct functional regions: a first region containing the Schottky diode and a second region containing the MOSFET. This segmentation allows each region to be independently optimized for its specific function. The Schottky diode region can be designed with parameters optimized for low turn-on voltage and fast switching, while the MOSFET region maintains its standard structure for high voltage blocking and current handling. This segmentation enables the device to achieve high chip density through reduced cell pitch while maintaining reliability through optimized regional structures.
3Speed
If an embedded Schottky diode is implemented, then switching speed and chip density improve, but additional process steps or expensive masks may be required
Solution Approach 1:
The patent merges the Schottky diode formation process with the existing MOSFET manufacturing process. The Schottky contact metal layer is deposited using the same metal deposition equipment and processes already used for forming source and drain contacts in the MOSFET. The Schottky diode region is defined using the same photolithography and etching steps that define the MOSFET regions. By merging these processes, the patent achieves embedded Schottky diode implementation without adding significant process complexity or requiring expensive specialized equipment.
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 semiconductor device achieves smaller size, higher switching speed, and increased chip density, reducing manufacturing costs and expanding application range to high-speed applications while improving the turn-on capability of body diodes and current capability without increasing process complexity.
Implementation Method 1
A first portion of the source metal layer contacts the Schottky region to form a Schottky diode
Data Source
AI summary
One embodiment provides a semiconductor device. The device comprises a substrate having a first face and a second face, a well region, a source region disposed in the well region, a contact region contacting the well region and the source region, a Schottky region, and a source metal layer. A first part of the source metal layer contacts the Schottky region to form a Schottky diode. The Schottky region is surrounded by the contact region and the well region in a first plane perpendicular to a direction from the first face toward the second face.