Integrated Schottky Contact in Superjunction MOSFETs
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Solution Overview
Problem
High-voltage MOSFET devices face a trade-off between breakdown voltage and on-state resistance, with superjunction devices presenting challenges in manufacturing fast reverse recovery and low forward voltage without increasing complexity and cost.
Innovation Solution
A semiconductor device with integrated Schottky contacts and a local charge balance structure, featuring pillars of different conductivity types and doping concentrations, and polysilicon-filled gate trenches, which enables fast reverse recovery and low forward voltage without degrading other electrical parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If superjunction devices are used to improve the trade-off between breakdown voltage and on-state resistance, then the electrical performance is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent merges the body diode formation with the superjunction structure by integrating the Schottky contact directly into the device architecture. The Schottky contact forms the body diode anode while the P-type pillars serve as the body diode cathode, eliminating the need for separate body diode fabrication processes and reducing manufacturing complexity while maintaining improved electrical performance.
Solution Approach 2:
The Schottky contact serves multiple functions: it acts as the anode for the body diode, provides a low-forward-voltage contact, and enables fast reverse recovery. The P-type pillars simultaneously form part of the superjunction structure for high voltage blocking and serve as the cathode for the body diode, reducing the number of separate components needed.
2Speed
If fast reverse recovery and low forward voltage are achieved in superjunction devices, then the switching performance is improved, but other electrical parameters may degrade
Solution Approach 1:
The patent applies local quality by creating P-type pillars with specific doping concentrations (1E15 to 1E17 atoms/cm³) in localized regions between the N-type drift region and the P-type body. These localized doped regions provide fast reverse recovery and low forward voltage where needed, while the surrounding undoped or lightly-doped regions maintain high voltage blocking capability and prevent parameter degradation.
Solution Approach 2:
The patent changes the doping concentration parameter in the body region by introducing P-type pillars with doping concentrations of 1E15 to 1E17 atoms/cm³. This parameter change enables fast reverse recovery and low forward voltage while the controlled doping levels prevent degradation of other electrical parameters such as breakdown voltage and on-resistance.
3Loss of energy
If a Schottky contact is integrated into the superjunction device, then body diode conduction loss is reduced, but the device structure becomes more complex
Solution Approach 1:
The patent merges the Schottky contact integration with the superjunction structure by using the P-type pillars as the body diode cathode and the Schottky contact as the anode. This merging reduces device structure complexity compared to adding a separate body diode structure, while still achieving reduced body diode conduction loss through the low-barrier Schottky contact.
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 solution provides a semiconductor device with improved reverse recovery and reduced body diode conduction loss, maintaining high voltage capability and preventing parameter degradation, while avoiding increased complexity and cost.
Implementation Method 1
The Schottky barrier of the Schottky contact may be 0.4 eV or less
Data Source
AI summary
A semiconductor device includes a semiconductor substrate defining a major surface. The device further includes a first region including at least a first pillar of a first conductivity type extending in a vertical orientation with respect to the major surface. The device further includes a second region of the first conductivity type. The first pillar includes a higher doping concentration than the second region. The device further includes a Schottky contact coupled to the second region.