Digital Isolator With Embedded Trench Coil
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Solution Overview
Problem
Current signal isolators, such as photocouplers and transformers, face challenges in reducing size, increasing breakdown voltage, and improving noise resistance, while also being costly and power-intensive, especially when integrated into semiconductor chips for industrial and medical applications.
Innovation Solution
A digital isolator with a transformer configuration featuring a primary-side coil embedded in a trench on a semiconductor substrate and a secondary-side coil formed on an insulating layer, where the coils are oriented in a depth direction to minimize parasitic capacitance and maximize breakdown voltage, allowing for integration on a single semiconductor chip without the need for bump electrodes, thus simplifying assembly and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional photocouplers or transformers are used as isolators, then electrical isolation and signal transfer are achieved, but the device size becomes large, cost increases, and power consumption rises
Solution Approach 1:
The patent transitions from planar coil arrangements to three-dimensional vertically stacked coil structures. The primary coil and secondary coil are positioned on different substrate layers separated by an insulating layer, utilizing the vertical dimension to achieve electrical isolation while maintaining compact footprint. This dimensional transition resolves the contradiction by enabling high isolation performance without increasing planar device area.
Solution Approach 2:
The patent embeds the primary coil within a trench structure formed in the semiconductor substrate, then fills the trench with conductive material to create the secondary coil. This nesting approach allows one coil structure to be contained within or around another, maximizing space utilization and reducing overall device volume while maintaining effective electrical isolation between primary and secondary circuits.
2Reliability
If conventional isolators are used, then signal transfer between high and low voltage units is achieved, but manufacturing complexity and assembly processes become cumbersome
Solution Approach 1:
The patent integrates both the primary coil and secondary coil, along with their respective transmission and reception circuits, onto a single semiconductor substrate using standard CMOS fabrication processes. This merging of previously separate components (isolator and circuits) into one monolithic structure eliminates the need for external mounting, wire bonding, and bump electrode formation, thereby simplifying assembly while maintaining high isolation performance.
Solution Approach 2:
The semiconductor substrate itself serves multiple functions: it provides the structural foundation, the insulating layer for electrical isolation, and the integration platform for all circuit components. The substrate structure automatically provides mechanical support and electrical isolation without requiring additional external assembly steps, enabling self-contained manufacturing and simplifying the overall fabrication process.
3Ease of manufacture
If standard planar coil configurations are used, then manufacturing is simplified, but parasitic capacitance increases and breakdown voltage decreases
Solution Approach 1:
The patent positions the primary and secondary coils in the vertical dimension rather than arranging them side-by-side in the planar dimension. By separating the coils along the vertical axis with an insulating layer, the design reduces parasitic capacitance between windings while maintaining manufacturability through standard thin-film deposition and etching processes. This vertical arrangement inherently provides better electrical isolation without complicating fabrication.
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 isolator's size reduction, breakdown voltage, and noise resistance, while simplifying the assembly process and reducing costs by eliminating the need for bump electrodes and wire bonding, making it suitable for high-voltage electronic devices.
Implementation Method 1
a transformer configured by the first coil and the second coil to transfer a signal between the first circuit and the second circuit from the first circuit to the second circuit or from the second circuit to the first circuit in an electrically isolated state
Data Source
AI summary
An isolator is configured by a transmission circuit, a transformer, and a reception circuit. A first coil of the transformer is disposed on a back surface of a first semiconductor substrate; a transmission circuit and a second coil of the transformer are disposed on a front surface. The first coil is embedded within a coil trench, is led out through an embedded via-metal-film to a substrate front surface, and is electrically connected to the transmission circuit. The second coil is disposed on an insulating layer of the substrate front surface. The reception circuit is disposed on a front surface of a second semiconductor substrate. The second coil and the reception circuit are electrically connected to each other by connecting first and third electrode pads disposed respectively on the front surfaces of the first and second semiconductor substrates through wires.