Trench-Isolated RESURF Diode for High Voltage
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Solution Overview
Problem
High-voltage diode devices in integrated circuits face challenges in balancing on-resistance and breakdown voltage, with increased breakdown voltage often leading to higher on-resistance, and they consume significant silicon area, making them costly and inefficient.
Innovation Solution
A trench-isolated high voltage diode structure with a RESURF (Reduced Surface Field) anode structure is developed, featuring a deep cathode region surrounded by a continuous anode region, with shallow trench isolation between anode and cathode contacts, to achieve high breakdown voltage while minimizing on-resistance and surface charging effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the device breakdown voltage is increased, then the breakdown voltage is improved, but the on-resistance increases
Solution Approach 1:
The patent applies local quality by creating a RESURF layer with specific doping characteristics in the high-field region near the junction, while maintaining different doping levels in other regions. This localized modification of electrical properties allows the device to achieve high breakdown voltage through field reduction at critical points without increasing overall on-resistance
Solution Approach 2:
The patent changes the doping concentration parameter by forming a lightly-doped RESURF layer with a doping level of 1E16 to 1E18 atoms/cm³, which is lower than conventional designs. This parameter change reduces the electric field strength in the depletion region, enabling higher breakdown voltage while maintaining low on-resistance through optimized current flow paths
2Ease of manufacture
If conventional diode structures are used, then manufacturing is simpler, but silicon area consumption increases
Solution Approach 1:
The patent transitions from planar diode structures to a vertically-integrated trench-isolated structure with multiple depth levels. The cathode extends deeper into the substrate than conventional designs, and the anode is positioned at a different vertical level, creating a three-dimensional arrangement that reduces lateral footprint while maintaining manufacturing feasibility through standard semiconductor processing techniques
3Device complexity
If surface field effects are not addressed, then device structure is simpler, but surface charging impacts performance
Solution Approach 1:
The patent introduces a RESURF layer as an intermediary region between the heavily-doped junction and the surface. This intermediate layer with moderate doping concentration (1E16 to 1E18 atoms/cm³) acts as a buffer that redistributes and reduces the electric field strength at the surface, preventing harmful surface charging effects without requiring complex surface passivation structures
Data Source
AI summary
A trench-isolated RESURF diode structure (100) is provided which includes a substrate (150) in which is formed anode (130, 132) and cathode (131) contact regions separated from one another by a shallow trench isolation region (114, 115), along with a non-uniform cathode region (104) and peripheral anode regions (106, 107) which define vertical and horizontal p-n junctions under the anode contact regions (130, 132), including a horizontal cathode/anode junction that is shielded by the heavily doped anode contact region (132).