Trench Semiconductor Device With Enclosed Cavity Insulation
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Solution Overview
Problem
In high power applications, transistor devices face a trade-off between on-state resistance and breakdown voltage, with increased doping concentration reducing on-state resistance but compromising breakdown voltage, and there is a limit to reducing trench width due to the Figure of Merit (FOM) and electrical isolation requirements.
Innovation Solution
A semiconductor device with a trench structure featuring a field plate and an enclosed cavity defined by insulating material, which allows for reduced trench width and increased breakdown voltage by using an insulating material with greater thickness at the trench bottom and a cavity-insulation material stack, ensuring mechanical stability and improved electrical isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the trench width is reduced to improve device integration, then the Figure of Merit improves, but electrical isolation between adjacent structures deteriorates
Solution Approach 1:
The patent implements a nested insulation structure where a first insulating layer is deposited on the trench base and sidewalls, followed by a second insulating layer that encapsulates the first layer. This nested configuration provides enhanced electrical isolation within the confined trench space, allowing reduced trench width while maintaining adequate isolation between adjacent field plates or gate structures.
Solution Approach 2:
The patent transitions from a single-layer insulation approach to a multi-layer insulation architecture, adding the vertical dimension of layer stacking. This dimensional change enables sufficient electrical isolation distance to be achieved within a narrower horizontal trench width, thereby improving device integration without compromising isolation reliability.
2Stability of the object's composition
If a thick insulating layer is used to ensure mechanical stability, then structural integrity improves, but the trench width must be increased which reduces device integration
Solution Approach 1:
The nested multi-layer insulating structure distributes the mechanical support function across multiple thinner layers rather than relying on a single thick layer. Each layer contributes to the overall structural integrity, enabling adequate mechanical stability to be achieved within a narrower trench width, thus improving device integration.
Solution Approach 2:
The patent employs composite insulation structures combining multiple insulating layers, potentially with different material properties. This composite approach allows optimization of both mechanical stability and space efficiency, as different layers can be selected for specific mechanical or electrical properties, achieving structural integrity without excessive trench width.
3Loss of energy
If doping concentration is increased to reduce on-state resistance, then conduction performance improves, but breakdown voltage deteriorates
Solution Approach 1:
The patent applies local quality by implementing targeted insulation structures at specific locations within the trench (on the base and sidewalls adjacent to conductive regions). This localized insulation approach allows for optimized doping profiles in different regions, enabling reduced on-state resistance in conductive paths while maintaining adequate breakdown voltage through localized field control and insulation.
Data Source
AI summary
A method includes: forming a trench in a first major surface of a semiconductor substrate, the trench having a base and a side wall extending from the base to the first major surface; forming a first insulating layer on the trench base and side wall; forming a sacrificial layer on the first insulating layer on the trench side wall; forming a second insulation layer on the sacrificial layer; inserting conductive material into the trench that at least partially covers the second insulation layer; selectively removing portions of the second insulation layer uncovered by the conductive material; selectively removing the sacrificial layer to form a recess that is positioned adjacent the conductive material in the trench and that is bounded by the first insulation layer and the second insulating layer; and forming a third insulating layer in the trench that caps the recess to form an enclosed cavity in the trench.