Embedded Schottky Diode in Trenched MOSFET Cell
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Solution Overview
Problem
Conventional semiconductor power devices require external Schottky diodes, which occupy additional space, increase capacitance, and complicate manufacturing, limiting miniaturization and increasing costs due to the need for additional masks and higher phosphorus dopant concentration, leading to inefficiencies in high-efficiency DC/DC applications.
Innovation Solution
A semiconductor power device configuration with embedded Schottky diodes in the same cell, featuring a trenched gate surrounded by source and body regions, an insulation layer, and a contact trench filled with a metal plug, where the Schottky diode is formed near the bottom of the trench with a barrier layer to reduce leakage current and forward voltage, and a dopant region along the sidewall for improved contact, reducing the need for additional masks and parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external Schottky diodes are used in parallel with power MOSFET devices, then clamping effect and prevention of body diode turn-on are achieved, but additional space is occupied and device miniaturization is limited
Solution Approach 1:
The patent merges the Schottky diode and MOSFET into a single integrated cell structure. The Schottky diode is formed within the same cell as the MOSFET by creating a Schottky contact at the bottom of the contact trench, eliminating the need for separate external Schottky diodes and reducing overall device area.
Solution Approach 2:
The Schottky diode structure is nested within the MOSFET cell structure. The Schottky contact is positioned at the bottom of the contact trench, utilizing the existing trench structure to house both the MOSFET and Schottky diode functions in a compact integrated arrangement.
2Area of stationary object
If trench Schottky diodes are integrated with MOSFET, then space is saved, but high leakage current occurs due to increased phosphorus dopant concentration during sacrificial and gate oxidation processes
Solution Approach 1:
The patent applies local quality by creating a dopant region with different doping characteristics at the bottom of the contact trench where the Schottky contact is formed. This localized dopant region reduces phosphorus dopant concentration specifically at the Schottky contact area, minimizing leakage current while maintaining the integrated space-saving structure.
3Area of stationary object
If planar Schottky diodes are integrated with trench MOSFET, then space is saved, but additional contact mask is required increasing manufacturing cost and process complexity
Solution Approach 1:
The contact trench structure serves multiple functions: it provides the contact path for the MOSFET and simultaneously forms the Schottky diode structure. The same contact mask and fabrication processes used for MOSFET contact formation are also used to create the Schottky contact, eliminating the need for additional masks and reducing manufacturing complexity.
4Reliability
If additional P+ mask is used to form Schottky diodes, then Schottky diode formation is achieved, but manufacturing cost increases and production efficiency decreases
Solution Approach 1:
The contact mask serves dual purposes: defining the MOSFET contact area and defining the Schottky contact area. This multi-functionality eliminates the need for a separate P+ mask step, reducing the total number of fabrication steps and improving production efficiency while ensuring proper Schottky diode formation.
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
This configuration achieves significant space savings, reduced parasitic capacitance, improved device performance, and simplified manufacturing, enabling higher switching speed and lower production costs while maintaining reliability.
Implementation Method 1
forming a Schottky barrier layer along sidewall of the source-body contact trench in the epitaxial layer and near a bottom of the source-body contact trench below the contact metal plug with the Schottky barrier layer having a barrier height for reducing a leakage current through the embedded Schottky diode during a reverse bias between the drain and the source
Implementation Method 2
forming a source-dopant region below the source-body contact trench in contact with the Schottky barrier layer of the Schottky diode having a different dopant concentration from the epitaxial layer surrounding the body region supported on the semiconductor substrate
Data Source
AI summary
A method for manufacturing a trenched semiconductor power device includes a step of forming said semiconductor power device with a trenched gate surrounded by a source region encompassed in a body region above a drain region disposed on a bottom surface of a substrate. The method further includes the steps of covering the MOSFET cell with an insulation layer and applying a contact mask for opening a source-body contact trench extending through the source and body regions into an epitaxial layer underneath for filling a contact metal plug therein. And, the method further includes a step of forming an embedded Schottky diode by forming a Schottky barrier layer near a bottom of the source-body contact trench below the contact metal plug with the Schottky barrier layer having a barrier height for reducing a leakage current through the embedded Schottky diode during a reverse bias between the drain and the source.