Schottky Diode Anode Segmentation for Low ON-Resistance
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Solution Overview
Problem
Conventional semiconductor devices face challenges in achieving low ON-resistance and high breakdown voltage characteristics due to high parasitic resistance in the epitaxial layer, excessive free carrier storage in the N-type epitaxial layer, and increased reverse recovery current rates, which can lead to destruction of protection diodes and circuit elements under overvoltage conditions.
Innovation Solution
The semiconductor device incorporates first and second anode diffusion layers of opposite conductivity types, a cathode diffusion layer with varying impurity concentrations, and a third anode diffusion layer with a lower impurity concentration to surround the first and second anode diffusion layers, along with an electric field shielding film to manage electric potential and reduce parasitic capacitance and reverse recovery current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the Zener diode and Schottky barrier diode are connected in parallel to reduce forward voltage, then the forward voltage characteristic is improved, but the parasitic resistance in the epitaxial layer increases, making it impossible to reduce ON-resistance
Solution Approach 1:
The anode region is divided into multiple diffusion layers (first anode diffusion layer, second anode diffusion layer, third anode diffusion layer) with different impurity concentrations. This segmentation allows each layer to contribute differently to current conduction, reducing overall parasitic resistance while maintaining low forward voltage through the parallel-connected Zener and Schottky barrier diodes.
Solution Approach 2:
Different regions of the semiconductor device are given different impurity concentrations to optimize local electrical properties. The first and second anode diffusion layers have higher impurity concentrations for low resistance contact, while the third anode diffusion layer has lower impurity concentration to control electric field distribution and reduce parasitic resistance in the epitaxial layer.
2Reliability
If P-type diffusion layers with high impurity concentration are formed to reduce ON-resistance, then the ON-resistance is reduced, but free carriers are excessively stored in the N-type epitaxial layer, increasing reverse recovery current density
Solution Approach 1:
The device employs multiple P-type diffusion layers with spatially varying impurity concentrations. The first and second anode diffusion layers use high impurity concentration to reduce ON-resistance, while the third anode diffusion layer uses lower impurity concentration to limit excessive free carrier storage in the epitaxial layer, thereby controlling reverse recovery current density.
Solution Approach 2:
The impurity concentration parameter is changed across different diffusion layers and regions. By adjusting the impurity concentration from high in the first and second anode diffusion layers to lower in the third anode diffusion layer, the device optimizes the balance between ON-resistance and reverse recovery characteristics.
3Reliability
If the thickness of insulation film is thickened at the boundary between conductive field plate and resistive field plate to improve breakdown voltage, then the breakdown voltage characteristic is improved, but the device complexity increases
Solution Approach 1:
The insulation film structure is optimized locally at critical regions. The thickness of the insulation film is selectively increased at the lower portion of the boundary between the conductive field plate and resistive field plate where electric field concentration occurs, while other regions maintain their original insulation film thickness, thus improving breakdown voltage without excessive 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 enhances the breakdown voltage characteristic, reduces ON-resistance, and minimizes the risk of diode destruction by effectively managing electric field concentrations and reverse recovery currents, allowing for efficient protection of circuit elements from overvoltage.
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 equipotential ring electrode and the conductive field plate formed on a top surface of the N-type semiconductor region are connected to each other by a resistive field plate. This structure intensifies an effect of the resistive field plate to reduce a curvature of a depletion layer placed at the lower portion of the boundary between the conductive field plate and the resistive field plate.
Data Source
AI summary
There is a problem that a reverse off-leak current becomes too large in a Schottky barrier diode. A semiconductor device of the present invention includes P-type first and second anode diffusion layers formed in an N-type epitaxial layer, N-type cathode diffusion layers formed in the epitaxial layer, a P-type third anode diffusion layer formed in the epitaxial layer so as to surround the first and second anode diffusion layers and to extend toward the cathode diffusion layers, and a Schottky barrier metal layer formed on the first and second anode diffusion layers.