Super-Trench Schottky Diode Field Segmentation
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Solution Overview
Problem
High-voltage PN diodes face challenges with high forward voltage and switching power dissipation due to high injection and conductivity modulation, while high-voltage Schottky diodes are limited by high voltage drops at high currents due to lack of injection, restricting their use to low currents.
Innovation Solution
A super-trench Schottky barrier diode (STSBD) with multiple floated Schottky contacts on trench walls achieves a balanced design between breakdown voltage, forward voltage, and shutdown power dissipation by allowing higher doping concentrations and linear voltage distribution, enabling operation at high current densities with low power dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high-voltage PN diode uses a thick low-doped region to achieve high breakdown voltage, then the breakdown voltage is improved, but the forward voltage and switching power dissipation increase
Solution Approach 1:
The patent divides the low-doped region into multiple segments by introducing trenches that extend from the front surface to the back surface. These trenches create field plates that segment the electric field distribution, allowing the voltage to be distributed more evenly across the thick low-doped region. This segmentation enables high breakdown voltage while reducing the forward voltage drop and switching power dissipation by preventing excessive electric field concentration in any single region.
2Strength
If a high-voltage Schottky diode uses a thick low-doped region to achieve high breakdown voltage, then the breakdown voltage is improved, but the forward voltage increases at high currents
Solution Approach 1:
The patent introduces trenches with field plates that segment the electric field in the thick low-doped region. This segmentation creates multiple electric field paths that distribute the voltage stress more evenly, reducing the peak electric field intensity. As a result, the diode can maintain high breakdown voltage while reducing the forward voltage drop at high currents by preventing excessive voltage concentration across the thick low-doped region.
3Loss of energy
If a high-voltage PN diode increases the doping concentration to reduce forward voltage, then the forward voltage is improved, but the breakdown voltage decreases
Solution Approach 1:
The patent applies local quality by creating regions of different doping concentrations in specific locations. The trenches with field plates create localized regions where the electric field is redistributed, allowing the low-doped region to maintain its low doping concentration for high breakdown voltage while the field plate regions provide enhanced field distribution that reduces the effective forward voltage drop. This local modification of electric field distribution allows both parameters to be optimized simultaneously.
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 STSBD exhibits lower or comparable forward voltage and significantly reduced shutdown power dissipation compared to high-voltage PN diodes, and lower forward voltage at high current densities compared to conventional Schottky diodes, overcoming previous limitations and achieving efficient high-current operation.
Implementation Method 1
The invention relates to Schottky diodes that are suitable for high-voltage utilization... The high-voltage Schottky diode is a so-called majority charge carrier component... a Schottky contact on a semiconductor substrate
Implementation Method 2
When operating at high current density in the forward direction, high injection exists in high-voltage PN diodes, i.e. electrons and holes are injected into the low-doped region. With high injection, the concentration thereof is higher than the doping concentration of the low-doped region. The result is that the conductivity of the low-doped region is modulated
Implementation Method 3
Upon shutdown, for example in the context of an abrupt current commutation, the charge carriers (electrons and holes) that are injected during operation in the forward direction into the low-doped region and stored there must first be dissipated before the high-voltage PN diode is at all capable of accepting reverse voltage again
Data Source
AI summary
A semiconductor assemblage of a super-trench Schottky barrier diode (STSBD) made up of an n+ substrate, an n-epilayer, trenches etched into the n-epilayer that have a width and a distance from the n+ substrate, mesa regions between the adjacent trenches having a width, a metal layer on the front side of the chip that is a Schottky contact and serves as an anode electrode, and a metal layer on the back side of the chip that is an ohmic contact and serves as a cathode electrode, wherein multiple Schottky contacts having a width or distance and a distance between the Schottky contacts, and between the Schottky contact as anode electrode and the first Schottky contact, are located on the trench wall.