Multi-Trench Schottky Diode Termination Design
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Solution Overview
Problem
Conventional trench Schottky diodes face limitations in reverse bias and leakage current, leading to potential early breakdown due to concentrated electric fields and surface charge accumulation in the termination area.
Innovation Solution
A multi-trench Schottky diode design featuring a semiconductor base layer, epitaxial layer, interlayer dielectric layer, and metal layers with specific trench structures and widths, which scatter electric fields and distribute voltage gradients to prevent early breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first metal layer and second metal layer are extended into the termination area to increase reverse bias, then reverse bias capability is improved, but surface charges accumulate on the epitaxial layer leading to early breakdown
Solution Approach 1:
The patent divides the termination area into multiple segments by introducing first, second, and third trench structures at different positions. These trenches segment the continuous epitaxial layer surface into discrete regions, preventing the accumulation of surface charges across the entire termination area. The segmentation approach maintains reverse bias capability while eliminating the harmful charge accumulation effect.
Solution Approach 2:
The patent introduces dielectric layers as intermediary substances between the metal layers and the epitaxial layer in the termination area. These dielectric layers act as mediators that prevent direct contact between metal and semiconductor, thereby preventing surface charge accumulation on the epitaxial layer while still allowing the structure to support reverse bias voltage.
2Reliability
If a guard ring structure is provided to distribute voltage level, then voltage distribution is improved, but the buffer ability is limited and electric charges still cluster to the rim of termination area
Solution Approach 1:
The patent enhances the guard ring structure by adding multiple trench structures (first, second, and third trenches) at different positions in the termination area. This segmentation approach divides the termination area into multiple zones, preventing charge clustering at the rim by providing alternative paths and distributing the electric field more evenly across the entire termination area.
Solution Approach 2:
The patent transitions from a two-dimensional planar guard ring structure to a three-dimensional multi-trench structure by introducing vertical trenches at multiple positions. This dimensional change allows for better voltage distribution and charge management by creating multiple discharge paths and distributing the electric field in both horizontal and vertical dimensions.
3Reliability
If multiple trenches with different widths are introduced to scatter electric fields, then electric field distribution is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by designing trenches with different widths at different positions according to the specific electric field distribution requirements of each region. The first trench has a different width than the second and third trenches, optimizing the electric field scattering effect in each local area. This approach improves overall electric field distribution while keeping the structure relatively simple by only varying trench width rather than introducing completely different structures.
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 multi-trench Schottky diode effectively reduces electric field concentration and voltage variations in the termination area, enhancing reverse bias capabilities and preventing early voltage breakdown.
Implementation Method 1
metal-semiconductor junctions are utilized as Schottky barriers to have characteristics in low forward voltage drop and high-speed switching
Implementation Method 2
the polysilicon in the trench can be used effectively to deplete drift electrons in a drift region
Implementation Method 3
an ideal rectifier should be at least featured in a low forward voltage drop, a high reverse breakdown voltage and zero leakage current
Data Source
AI summary
A multi-trench schottky diode includes a semiconductor base layer, a back metal layer, an epitaxial layer, an interlayer dielectric layer, a first metal layer, a passivation layer and a second metal layer. The epitaxial layer on the semiconductor base layer includes a termination trench structure, a first trench structure, a second trench structure and a third trench structure. The dielectric layer is on the epitaxial layer in a termination area. The first metal layer stacked on the termination trench structure and the interlayer dielectric layer extends between the second trench structure and the third trench structure. The passivation layer is on the first metal layer and the interlayer dielectric layer. The second metal layer on the first metal layer and the passivation layer extends to the first trench structure. Thus, the electric field is dispersed and the voltage breakdown can be avoided with the trench structures in the termination area.