Dielectric-Filled Trench Isolation for Low-Capacitance RDL Electrodes
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Solution Overview
Problem
As devices scale, the decreased distance between electrodes and the substrate increases parasitic capacitance in galvanic isolation structures, limiting the ability to add dielectric thickness or layers for effective isolation, especially in high-voltage applications.
Innovation Solution
A structure with a dielectric-filled trench or deep trench isolation in the substrate under electrodes, extending fully or partially to the backside, reduces parasitic capacitance by increasing capacitive coupling and dielectric strength without requiring thicker or additional BEOL interconnect layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the distance between electrode and substrate is decreased due to device scaling, then device integration is improved, but parasitic capacitance increases
Solution Approach 1:
A dielectric material is introduced as an intermediary substance between the electrode and substrate to reduce parasitic capacitance. The dielectric-filled trench acts as a mediator that blocks direct capacitive coupling while allowing the scaled geometry to be maintained for high integration.
Solution Approach 2:
The substrate area under the electrode is segmented by creating a trench that divides the continuous substrate into isolated regions. This segmentation prevents the formation of large parasitic capacitance by breaking up the capacitive coupling area between the electrode and substrate.
2Reliability
If dielectric thickness or number of dielectric layers is increased to reduce parasitic capacitance, then galvanic isolation is improved, but available space is consumed
Solution Approach 1:
Instead of increasing dielectric thickness in the vertical dimension between electrode and substrate, the solution creates a trench that extends into the substrate dimension. This dimensional change allows for effective capacitance reduction without consuming the limited vertical space between interconnect layers.
Solution Approach 2:
A trench is excavated from the substrate to remove a portion of the substrate material that would otherwise contribute to parasitic capacitance. By taking out this substrate region and filling it with dielectric, the harmful capacitive coupling is eliminated while preserving the limited space above the substrate.
3Ease of manufacture
If conventional BEOL interconnect layers are used for galvanic isolation, then manufacturing is simplified, but isolation strength is insufficient for high-voltage applications
Solution Approach 1:
The galvanic isolation structure uses a composite approach combining the existing BEOL dielectric layers with an additional dielectric-filled trench in the substrate. This composite structure leverages the manufacturing simplicity of standard BEOL processes while adding the trench-based isolation to achieve the required high-voltage breakdown strength.
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 approach provides stronger kilo-Volt level galvanic isolation with reduced parasitic capacitive leakage to the substrate, enhancing voltage domain separation and protection beyond conventional BEOL interconnect layers.
Implementation Method 1
reduces parasitic capacitance by increasing capacitive coupling and dielectric strength
Implementation Method 2
reduces parasitic capacitance by increasing capacitive coupling and dielectric strength
Data Source
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AI summary
A structure includes a substrate having a frontside and a backside. A first electrode is in a first insulator layer and is adjacent to the frontside of the substrate. The first electrode is part of a redistribution layer (RDL). A second electrode is between the substrate and the first electrode. A dielectric-filled trench in the substrate is under the first electrode and the second electrode, the dielectric-filled trench may extend fully to the backside of the substrate. The structure provides a galvanic isolation that exhibits less parasitic capacitance to the substrate from the lower electrode.