Galvanically-Isolated Semiconductor Capacitor with Series Dielectric Segmentation
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Solution Overview
Problem
Conventional galvanic isolators require thick dielectric materials to withstand ultra-high voltages, leading to increased stress and volume, making them inefficient and bulky.
Innovation Solution
A galvanically-isolated device with a high-voltage semiconductor capacitor structure featuring inter-metal dielectric layers and discrete plates connected in series, encapsulated in a molding compound with bonding wires, and a protective polyimide layer, which enhances breakdown voltage without increasing thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick dielectric material is used in conventional capacitive isolators to withstand ultra-high voltage, then the breakdown voltage capability is improved, but the device volume and stress increase significantly
Solution Approach 1:
The patent divides the single thick dielectric into multiple thin dielectric layers (first inter-metal dielectric layer, second inter-metal dielectric layer, third inter-metal dielectric layer) separated by conductive plates. This segmentation allows the total voltage blocking capability to be achieved through series connection of multiple smaller units, avoiding the need for a single thick dielectric and reducing overall device volume.
Solution Approach 2:
The patent transitions from a planar capacitor structure to a three-dimensional stacked structure with multiple layers arranged vertically. By utilizing the vertical dimension, the design achieves high voltage blocking capability through series connection of multiple capacitor units stacked in the vertical direction, thereby reducing the horizontal footprint and overall device volume.
2Reliability
If thick dielectric material is used in conventional capacitive isolators to withstand ultra-high voltage, then the breakdown voltage capability is improved, but the mechanical stress on the dielectric increases
Solution Approach 1:
The patent segments the single thick dielectric into multiple thin dielectric layers, which distributes the mechanical stress across multiple interfaces rather than concentrating it in one location. Each thin layer experiences reduced stress compared to a single thick layer, improving reliability under high voltage conditions.
Solution Approach 2:
The patent employs composite structures combining multiple dielectric materials (first, second, and third inter-metal dielectric layers) with different properties. This composite approach allows optimization of stress distribution and electrical properties, achieving high breakdown voltage capability while managing mechanical stress through material selection and layer configuration.
3Reliability
If conventional capacitive isolator design is used, then galvanic isolation is achieved, but the device requires enhanced isolation strength and great thickness
Solution Approach 1:
The patent segments the isolation function into multiple discrete capacitor units arranged in series, where each unit contributes to the total breakdown voltage capability. This segmentation achieves enhanced galvanic isolation through the cumulative effect of multiple thin dielectric layers, eliminating the need for a single thick dielectric while maintaining reliable isolation.
Solution Approach 2:
The patent utilizes the vertical stacking dimension to achieve enhanced isolation strength without increasing the horizontal dimensions. By arranging multiple capacitor units in series in the vertical direction, the design accomplishes high breakdown voltage capability and reliable galvanic isolation while keeping the device compact in the horizontal plane.
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 provides improved breakdown voltage and reduced volume, addressing the inefficiencies of conventional galvanic isolators by optimizing the capacitor structure and materials, resulting in a more compact and effective isolation solution.
Implementation Method 1
The dielectric of the conventional capacitive isolator, however, requires great thickness and an enhanced isolation strength to endure the application of ultra-high voltage
Implementation Method 2
A first bonding wire is electrically connected between the second plate and the first lead. A second bonding wire is electrically connected between the third plate and the second lead
Implementation Method 3
A molding compound layer encapsulates the high-voltage semiconductor capacitor, the first die-attach pad, the first bonding wire and the second bonding wire
Data Source
AI summary
A galvanically-isolated device and a method for fabricating the same are provided. The galvanically-isolated device includes a lead frame including a first die-attach pad, a first lead and a second lead. A substrate is disposed on the first die-attach pad. A high-voltage semiconductor capacitor formed on the substrate includes an interconnection structure. The interconnection structure includes an inter-metal dielectric layer structure. A first plate, a second plate and a third plate are formed on the inter-metal dielectric layer structure, separated from each other. The first plate, the second plate and a first portion of the inter-metal dielectric layer structure are composed of a first capacitor. The first plate, the third plate and a second portion of the inter-metal dielectric layer structure are composed of a second capacitor connected in series with the first capacitor.