HV Drain Trench Layout for Reliable Current Transmission
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Solution Overview
Problem
The reliability of high voltage (HV) devices in OLED technology is compromised due to the inclination angle and interface issues of shallow trench isolations, which affect current transmission and device performance, especially as process nodes decrease.
Innovation Solution
The introduction of a second dielectric layer in a second trench, aligned with the drain shallow trench isolation, increases the depth of current transmission and alleviates the adverse impact of the drain shallow trench isolation's sharp corners, enhancing device reliability by forming an integral structure with a step-like inclination angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a drain shallow trench isolation is formed in the drain structure of an HV device to achieve higher withstand voltage, then the reliability of the HV device is improved, but the sharp corners of the drain shallow trench isolation adversely affect current transmission and reduce device reliability
Solution Approach 1:
The patent introduces a second trench filled with a second dielectric layer adjacent to the drain shallow trench isolation. This adds a new spatial dimension to the current transmission path, allowing current to flow through multiple pathways (along the side face and bottom surface of the drain shallow trench isolation, and through the second trench). This dimensional expansion resolves the contradiction by maintaining the beneficial voltage blocking function while creating alternative current routes that avoid the harmful sharp corners.
Solution Approach 2:
The second trench filled with a second dielectric layer acts as an intermediary structure between the drain shallow trench isolation and the active region. It provides a mediating current transmission path that bypasses the sharp corners of the drain shallow trench isolation, thereby eliminating the adverse impact on current transmission while preserving the voltage blocking function of the original isolation structure.
2Reliability
If the inclination angle of the drain shallow trench isolation is adjusted to improve current transmission, then the device reliability may be improved, but at advanced process nodes like 28-nanometer technology, the adjustment capability is limited and cannot sufficiently resolve the adverse impact
Solution Approach 1:
Instead of relying solely on adjusting the inclination angle within the existing planar constraint, the patent adds a second trench structure that extends the current transmission path into an additional spatial dimension. This provides adaptability beyond what inclination angle adjustment can achieve, especially at advanced process nodes where geometric adjustments are increasingly constrained.
3Reliability
If a thicker gate dielectric layer is used in HV devices to achieve higher withstand voltage, then the voltage blocking capability is improved, but it affects subsequent processes of the metal gate and increases device complexity
Solution Approach 1:
The patent segments the dielectric structure into two distinct parts: a first dielectric layer in the gate dielectric trench and a second dielectric layer in the second trench. This segmentation allows each layer to be optimized independently - the first layer for gate control and the second layer for current path management - thereby reducing the complexity associated with using a uniformly thick gate dielectric layer throughout the entire device structure.
Data Source
AI summary
The present application discloses an HV device, comprising: a gate dielectric layer formed in a first trench and a second dielectric layer formed in a second trench. A second side face of a drain shallow trench isolation is aligned with a first side face of the first trench. A second side face of the second trench is aligned with a first side face of the drain shallow trench isolation. A drain high voltage diffusion region is formed in a first high voltage well region, and the drain shallow trench isolation is located in the drain high voltage diffusion region. A drain region is formed in a surface region of the drain high voltage diffusion region outside the first side face of the second dielectric layer. The present application also discloses a method for manufacturing an HV device.