HV Trench Gate Structure to Eliminate STI Corner Trapping
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Solution Overview
Problem
The existing high voltage (HV) devices in OLEDs suffer from instability due to charge carrier trapping at the sharp corners of the shallow trench isolations (STIs) under high voltage operation, leading to surge currents and resistance fluctuations, which are not addressed by current manufacturing processes.
Innovation Solution
The proposed method involves forming a gate dielectric layer with a flush surface and a second trench aligned with the drain shallow trench isolation, eliminating sharp corners by extending the gate conductive material layer to cover the second dielectric layer, ensuring no sharp corners are present, and using a symmetrical or asymmetrical structure to align the source and drain regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shallow trench isolation (STI) is formed in the drain structure of a high voltage device, then the withstand voltage is improved, but sharp corners are formed at the STI corners which cause charge carrier trapping and device instability
Solution Approach 1:
The patent applies curvature by replacing the sharp corner geometry of the STI with a rounded corner structure. Specifically, the STI is formed with rounded corners instead of sharp 90-degree angles, which eliminates the electric field concentration at corners and prevents charge carrier trapping. This geometric modification maintains the high voltage blocking capability while eliminating the instability caused by sharp corners.
2Stability of the object's composition
If the gate conductive material layer is extended to cover the second dielectric layer, then sharp corners are eliminated and device stability is improved, but the device complexity increases
Solution Approach 1:
The patent merges the gate conductive material layer with the region over the rounded corner of the STI. By extending the gate material to cover the rounded corner area, the structure eliminates sharp corners without requiring separate processing steps or additional components. This merging approach simplifies the overall fabrication process while achieving the stability improvement.
3Reliability
If a thick silicon oxide gate dielectric layer is used in HV devices, then the withstand voltage is improved, but it affects subsequent standard processes of the metal gate
Solution Approach 1:
The patent segments the gate dielectric structure by forming a first gate dielectric layer with thickness optimized for metal gate processes, and a second gate dielectric layer with increased thickness for enhanced withstand voltage. This segmentation allows each layer to serve its specific function: the first layer ensures process compatibility while the second layer provides the additional voltage blocking capability required for high voltage operation.
Data Source
AI summary
The present application discloses an HV device, comprising: a gate dielectric layer formed in a first trench, a gate conductive material layer formed on the surface of the gate dielectric layer, and a second dielectric layer filling a second trench formed between a second side face of a drain shallow trench isolation and a first side face of the first trench. The depths of the first trench and the second trench are equal. The first trench and the second trench connect with each other to form an overall trench. Bottom surfaces of the second dielectric layer and the gate dielectric layer are flush with each other. A first side face of the gate conductive material layer extends to the surface of the second dielectric layer. The present application also discloses a method for manufacturing the HV device.