Schottky Rectifier with Transparent Layer for High Voltage
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Solution Overview
Problem
Conventional Schottky rectifiers have limited blocking voltage range due to high on-state resistance and leakage currents at high breakdown voltages, making them unsuitable for applications beyond 200V, and the Trench MOS Barrier Schottky device still faces challenges with on-state voltage drop at voltages exceeding 300V.
Innovation Solution
A Schottky diode with a mixed bipolar and unipolar conduction mechanism, featuring a lightly doped transparent layer that forms a Schottky contact and a low injection efficiency junction, reduces on-state resistance and leakage current, and includes a p-transparent layer to control minority carrier injection and plasma formation, enhancing on-state performance and reverse recovery speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the doping concentration of the drift region is decreased to increase breakdown voltage, then the blocking voltage range is improved, but the on-state forward voltage drop increases severely
Solution Approach 1:
The patent changes the doping concentration parameter in the drift region to optimize the balance between breakdown voltage and on-state forward voltage drop. By carefully controlling the doping concentration, the device achieves high breakdown voltage while maintaining low on-state resistance, resolving the contradiction between blocking voltage range and energy loss.
Solution Approach 2:
The patent employs a composite structure combining the drift region with a specially designed contact structure that includes multiple layers with different doping concentrations. This composite approach allows the device to achieve both high breakdown voltage and low on-state forward voltage drop by optimizing the interaction between different regions.
2Loss of energy
If the depth of the drift region is increased to reduce on-state resistance, then the on-state forward voltage drop is reduced, but the breakdown voltage decreases
Solution Approach 1:
The patent optimizes the depth parameter of the drift region to achieve the right balance. By controlling the depth within a specific range and combining it with appropriate doping concentrations, the device achieves low on-state forward voltage drop while maintaining high breakdown voltage capability.
Solution Approach 2:
The patent applies local quality by creating regions with different doping concentrations at different locations. The drift region has a specific doping profile that varies with depth, allowing different parts of the device to optimize for either low on-state resistance or high breakdown voltage as needed.
3Device complexity
If conventional Schottky rectifier structure is used for high breakdown voltage applications, then the device simplicity is maintained, but leakage currents increase significantly
Solution Approach 1:
The patent applies local quality by introducing a specifically doped region at the Schottky contact interface. This localized modification with appropriate doping concentration creates a potential barrier that reduces leakage currents while maintaining the overall simplicity of the Schottky rectifier structure.
Solution Approach 2:
The patent changes the doping concentration parameter in the drift region to optimize the balance between breakdown voltage and on-state forward voltage drop. By carefully controlling the doping concentration, the device achieves high breakdown voltage while maintaining low on-state resistance, resolving the contradiction between blocking voltage range and energy loss.
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 achieves significantly lower on-state resistance and leakage current, faster switching speed, and reduced losses during reverse recovery, enabling higher current capability and improved performance at high blocking voltages.
Implementation Method 1
A Schottky contact is formed at the interface between the metal layer 230 and the drift layer 220
Implementation Method 2
a lightly doped transparent layer that forms a Schottky contact and a low injection efficiency junction, reduces on-state resistance and leakage current, and includes a p-transparent layer to control minority carrier injection and plasma formation
Implementation Method 3
A Schottky diode with a mixed bipolar and unipolar conduction mechanism
Implementation Method 4
the unipolar conduction mechanism of the Schottky rectifier
Implementation Method 5
control minority carrier injection and plasma formation, enhancing on-state performance
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A semiconductor rectifier includes a semiconductor substrate having a first type of conductivity. A first layer, which is formed on the substrate, has the first type of conductivity and is more lightly doped than the substrate. A second layer having a second type of conductivity is formed on the substrate and a metal layer is disposed over the second layer. The second layer is lightly doped so that a Schottky contact is formed between the metal layer and the second layer. A first electrode is formed over the metal layer and a second electrode is formed on a backside of the substrate.