Integrated Schottky Trench Structure for Low-Inductance MOSFET Rectification
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Solution Overview
Problem
The integration of Schottky diodes with MOSFETs in parallel circuits leads to increased parasitic inductance, reducing performance and increasing costs due to the external connection, which is not optimal for low power consumption and high switching speed applications.
Innovation Solution
A semiconductor structure incorporating a Schottky diode with a first N-type semiconductor layer, trench, insulating layer, polysilicon or metal silicide layers, and a grounded P-type protective layer, where the polysilicon or metal silicide layers are disposed in parallel and the metal layer forms electrodes, creating a Schottky junction and an electron accumulated region to enhance forward current and reduce parasitic inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Schottky diode is externally connected to the MOSFET device in parallel, then the rectifier function is achieved, but the parasitic inductance is increased and performance decreases
Solution Approach 1:
The patent merges the Schottky diode and MOSFET into a single integrated device structure. The Schottky diode is formed by creating a metal-semiconductor junction at the top surface of the N-type semiconductor layer, while the MOSFET is formed within the same semiconductor substrate. This integration eliminates the need for external connections between separate components, thereby reducing parasitic inductance while maintaining the rectifier function.
Solution Approach 2:
The integrated device structure serves multiple functions: the N-type semiconductor layer with metal contact forms both the anode of the Schottky diode and the source/drain region of the MOSFET, while the P-type protective layer provides both diode cathode functionality and MOSFET gate isolation. This multi-functionality reduces the need for additional components and external connections.
2Reliability
If the Schottky diode is externally connected to the MOSFET device in parallel, then the rectifier function is achieved, but the cost increases
Solution Approach 1:
The patent combines two separate devices (Schottky diode and MOSFET) into a single integrated structure, reducing component count and assembly complexity. The shared semiconductor substrate and overlapping fabrication processes lower manufacturing costs compared to external connections requiring additional packaging and interconnects.
3Reliability
If the Schottky junction gap is increased to enhance forward current value, then the conductivity is improved, but the device area increases
Solution Approach 1:
The patent employs localized doping regions with varying concentrations to optimize current distribution. The P-type protective layer has a doping concentration higher than the N-type semiconductor layer, creating localized high-field regions that enhance forward current without requiring proportional increases in overall device area. The trench structure also concentrates the electric field in specific regions.
Solution Approach 2:
The patent introduces a vertical dimension through the trench structure extending into the semiconductor layer. This three-dimensional configuration allows the Schottky junction gap to be optimized in the vertical direction while maintaining a compact planar footprint, effectively decoupling the forward current enhancement from lateral area expansion.
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 proposed structure increases forward current values and reduces parasitic inductance, improving the performance and efficiency of the Schottky diode by forming a Schottky junction and electron accumulated region, while maintaining low power consumption and high switching speed.
Implementation Method 1
a Schottky junction is formed at a junction of the metal layer and a top of the first N-type semiconductor layer
Implementation Method 2
An electron accumulated region is formed outside the first insulating layer
Implementation Method 3
An interface between a bottom surface of the first P-type protective layer and the first N-type semiconductor layer has a PN junction
Data Source
AI summary
A semiconductor structure includes a Schottky diode structure, which includes: a first trench extending through a first N-type semiconductor layer and being disposed in the first N-type semiconductor layer; a first insulating layer disposed in the first trench; two polysilicon layers or metal silicide layers disposed in the first trench, wherein an upper one and a lower one of the polysilicon layers or metal silicide layers are disposed in parallel; a first P-type protective layer, which is grounded and disposed on a bottom of the first trench, and contacts the first insulating layer and a bottom surface of the lower one of the polysilicon layers or metal silicide layers; a metal layer respectively disposed as a top surface and a lower bottom surface of the semiconductor structure to form a source and a drain as electrodes for the semiconductor structure to be connected to an external device.