Vertical FET Schottky Diode Integration for Power Loss Reduction
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Solution Overview
Problem
Vertical field effect transistors experience significant power and switching losses due to the voltage drop across the body diode between the body and drift regions, which is not efficiently addressed by existing technologies.
Innovation Solution
Incorporating a Schottky diode electrically connected in parallel to the body diode, with its junction formed vertically above the lower end of the body region, reducing the forward voltage drop and thereby minimizing power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a body diode is formed between the body region and drift region in a vertical field effect transistor, then the device structure is simple and manufacturing is easy, but the forward voltage drop is high causing significant power and switching losses
Solution Approach 1:
The patent combines a Schottky diode structure with the vertical field effect transistor by forming a Schottky contact between the drift region and a metal electrode. This merged structure allows the Schottky diode to operate in parallel with the body diode, providing a lower forward voltage path while maintaining the original transistor structure, thus reducing power loss without significantly increasing device complexity
Solution Approach 2:
The patent changes the physical and chemical parameters of the diode junction by using a Schottky contact instead of a standard p-n junction. The Schottky contact creates a metal-semiconductor junction with different electrical characteristics, specifically achieving a lower forward voltage drop (typically 0.3-0.7V compared to 0.7-1.0V for p-n junctions) while maintaining the vertical device structure
2Ease of manufacture
If the Schottky diode junction is formed below the body region at a side wall of field electrode trench, then the manufacturing process is simplified, but the Schottky junction characteristics become dependent on two process variables (trench etch and body implant) with lot variation
Solution Approach 1:
The patent extracts the Schottky diode junction formation from the complex interaction of multiple process steps (trench etch and body implant) by positioning it at a location where it depends on fewer process variables. By forming the Schottky contact at a specific position relative to the body region boundary, the junction characteristics become less sensitive to process variations, improving manufacturing precision
Solution Approach 2:
The patent introduces a field electrode structure as an intermediary element that helps define the position of the Schottky junction. The field electrode trench and its associated structures serve as a reference framework that decouples the Schottky junction positioning from direct dependence on both trench etch and body implant variables, reducing lot variation
3Reliability
If a metal structure for Schottky junction is placed below the body region, then the junction can be formed, but the small structure is critical and takes much current under high reverse current conditions
Solution Approach 1:
The patent moves the Schottky diode junction from a vertical position below the body region to a horizontal/planar position at the boundary between body and drift regions. This dimensional change allows the Schottky contact to be formed over a larger area in the plane of the device, reducing current density and improving reliability without requiring complex small-scale vertical metal structures
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 with a lower forward voltage than the body diode reduces power losses by approximately 0.2 V at a given current, enhancing the overall performance of the transistor device.
Implementation Method 1
a Schottky diode electrically connected in parallel to the body diode, with its junction formed vertically above the lower end of the body region
Data Source
AI summary
The present application relates to a semiconductor transistor device that includes a Schottky diode electrically connected in parallel to a body diode formed between a body region and a drift region. A diode junction of the Schottky diode is formed adjacent to the drift region and is arranged vertically above a lower end of the body region.