Trench MOSFET Schottky Integration in Non-Active Area
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Solution Overview
Problem
MOSFET devices face challenges with high forward voltage (Vf) and reverse recovery charge (Qrr) due to their intrinsic body diode, which affects switching efficiency and requires additional components like Schottky barrier diodes that occupy active area space.
Innovation Solution
Integrating Schottky barrier diodes in non-active areas of the MOSFET structure, reducing conduction loss and reverse recovery charge without using active area space, thus improving switching efficiency and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If Schottky barrier diode is integrated at the bottom of source trenches or by opening up the bottom of source trenches into the active area, then forward voltage (Vf) and reverse recovery charge (Qrr) are reduced, but active area is lost
Solution Approach 1:
The patent relocates the Schottky barrier diode integration from the traditional bottom-of-trench position (2D plane within active area) to the sidewalls of non-active areas (utilizing the vertical dimension and peripheral space). This dimensional shift allows the diode to be formed in the lateral regions between active cells, converting space utilization from a competitive 2D footprint to a 3D peripheral arrangement that does not encroach on active switching area.
Solution Approach 2:
The patent segments the Schottky diode formation into discrete regions located in the non-active areas between active cells. Instead of a continuous integration approach that would consume active area, the diode structure is divided and distributed across multiple non-active region segments, allowing each active cell to maintain its full area while collectively providing the required diode function throughout the device.
2Area of stationary object
If Schottky barrier diode is integrated in non-active areas, then active area is preserved, but additional manufacturing complexity is introduced
Solution Approach 1:
The patent employs a universal metallization and doping process that serves dual functions: forming the Schottky barrier diode in non-active areas while simultaneously maintaining compatibility with standard MOSFET fabrication sequences. The same metal deposition and thermal processing steps that create the Schottky contact also perform necessary functions for the adjacent active regions, eliminating the need for separate dedicated process modules and reducing overall manufacturing complexity despite the added functionality.
3Device complexity
If body diode is used in MOSFET, then external freewheeling diode is eliminated, but forward voltage (Vf) and reverse recovery charge (Qrr) are higher
Solution Approach 1:
The patent fundamentally changes the physical and electrical parameters of the diode by replacing the intrinsic body diode structure with an integrated Schottky barrier diode. This parameter change involves altering the contact type from a pn-junction (body diode) to a metal-semiconductor Schottky junction, which inherently provides lower forward voltage drop and reduced reverse recovery charge, thereby improving energy efficiency while maintaining the freewheeling function.
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 results in lower conduction loss and ultra-low reverse-recovery charge with soft recovery during MOSFET switching, enhancing overall switching efficiency and device performance without penalizing the active area.
Implementation Method 1
a Schottky contact between the bottom portion of source trenches and the semiconductor region underneath the same
Data Source
AI summary
The present embodiments relate to an apparatus and method of integrating a semiconductor cell in a non-active area of a MOSFET on a semiconductor substrate. An active area of the MOSFET may include a regular MOSFET cell. The semiconductor cell which can have various structures is configured to function as trench MOS barrier Schottky (TMBS) diode. Depending on its structure the TMBS diode may be integrated in a termination region or a shield tie region or a gate finger neighboring region in the non-active area. The integrated TMBS diode as such can limit the body diode conduction and improve the conduction and switching efficiency in a circuit. Additionally, an integrated TMBS diode may improve the softness of reverse recovery of the MOSFET, reduce drain to source voltage overshoot and ringing due to softer recovery and/or shield bounce without wasting any active area of the semiconductor die of the MOSFET.