Semiconductor Protection Diode With Field Plate
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Solution Overview
Problem
Conventional semiconductor devices face challenges in reducing ON-resistance, maintaining desired withstand voltage characteristics, and managing reverse recovery current rates due to high parasitic resistance and capacitance, especially when used as protection diodes in high-frequency circuits.
Innovation Solution
The semiconductor device incorporates first and second anode diffusion layers of opposite conductivity types, a cathode diffusion layer, and a third anode diffusion layer connected to the second anode diffusion layer, with an insulation layer and an anode electrode forming a Schottky junction, and includes a discharge diffusion layer for recombination of free carriers, reducing the rate of change of reverse recovery current and preventing electric field concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the epitaxial layer is used as a channel for main current in the Schottky barrier diode, then the forward voltage characteristic is improved, but the parasitic resistance increases and ON-resistance cannot be reduced
Solution Approach 1:
The patent divides the current conduction path into two separate regions: the epitaxial layer region for forward voltage control (Schottky barrier diode function) and the diffusion layer region for low-resistance current conduction (Zener diode function). This segmentation allows each region to optimize its specific function without compromising the other, resolving the contradiction between forward voltage characteristic and ON-resistance.
Solution Approach 2:
The patent creates a multi-functional device where the same semiconductor structure serves dual purposes: the Schottky barrier diode provides low forward voltage drop while the Zener diode provides low ON-resistance current conduction. This multi-functionality allows the protection diode to achieve both low forward voltage and low ON-resistance simultaneously.
2Reliability
If the P-type diffusion layer with high impurity concentration is formed on the surface, then the Schottky barrier is formed, but the free carriers are reduced and reverse recovery current density increases
Solution Approach 1:
The patent segments the diffusion layer structure into multiple regions with different impurity concentrations. The high impurity concentration region forms the Schottky barrier, while the low impurity concentration region reduces free carrier storage. This segmentation allows the device to maintain both the Schottky barrier function and low reverse recovery current density.
3Device complexity
If the anode electrode is formed on the top surface of the P-type semiconductor region, then the device structure is simplified, but the electric field concentration occurs and withstand voltage characteristic deteriorates
Solution Approach 1:
The patent applies local quality by forming the P-type diffusion layer with specific impurity concentration distribution at the electrode contact region. This localized modification of material properties (impurity concentration) at the critical electrode interface prevents electric field concentration and improves withstand voltage characteristic without significantly increasing overall device complexity.
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 allows for lower ON-resistance, improved withstand voltage characteristics, and reduced reverse recovery current rates, effectively protecting circuit elements from overvoltage and maintaining performance in high-frequency applications.
Implementation Method 1
A Schottky barrier metal layer is formed in such a way to come in contact with the epitaxial layer surrounded by both guard regions. Then, a Schottky barrier diode is formed of a silicide of the Schottky barrier metal layer and the epitaxial layer.
Implementation Method 2
A P-type diffusion layer is overlapped onto an N-type diffusion layer formed on the epitaxial layer. Then, an anode electrode is formed on the P-type diffusion layer, and a cathode electrode is formed on a back surface of the substrate to form a Zener diode using a PN junction of both diffusion layers.
Implementation Method 3
an insulation layer formed on a top surface of the semiconductor layer
Implementation Method 4
includes a discharge diffusion layer for recombination of free carriers, reducing the rate of change of reverse recovery current
Data Source
AI summary
In a semiconductor device of the present invention, a protection diode for protecting a device is formed on an epitaxial layer formed on a substrate. A Schottky barrier metal layer is formed on a surface of the epitaxial layer and a P-type diffusion layer is formed at a lower portion of an end portion of the Schottky barrier metal layer. Then, a P-type diffusion layer is formed to be connected to a P-type diffusion layer and is extended to a cathode region. A metal layer to which an anode electrode is applied is formed above the P-type diffusion layer, thereby making it possible to obtain a field plate effect. This structure reduces a large change in a curvature of a depletion layer, thereby improving a withstand voltage characteristic of the protection diode.