High Voltage FinFET Shielding Region Design
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Solution Overview
Problem
FINFETs are not compatible with high voltage applications due to issues such as drain endurance and gate-induced drain leakage, as they lack the structural features like shallow trench isolation that planar devices have, making it difficult to integrate high voltage and standard voltage circuitry in the same system.
Innovation Solution
The formation of FINFETs with shielding regions covering the drain-side FIN region and/or stepped dielectric layers in the gate stack, which improves field distribution and enhances voltage endurance by reducing peak electric fields and gate-induced drain leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If FINFET structure is used for device dimension scaling, then gate control and scalability are improved, but voltage endurance and reliability deteriorate due to high electric field at gate edge
Solution Approach 1:
The drift region is segmented into multiple regions with different doping concentrations (first drift region with first doping concentration, second drift region with second doping concentration). This segmentation allows the electric field to be distributed across different regions, reducing the peak electric field at the gate edge while maintaining the overall FINFET structure's scalability and gate control benefits.
Solution Approach 2:
Different regions of the drift region are assigned different doping concentrations to create local variations in electrical properties. The first drift region has a first doping concentration optimized for one aspect of performance, while the second drift region has a second doping concentration optimized for another aspect, allowing simultaneous optimization of voltage endurance and scalability in different locations.
2Reliability
If shallow trench isolation is introduced to improve voltage endurance, then reliability is improved, but device complexity increases due to difficulty in introducing STI into thin FIN structures
Solution Approach 1:
Instead of introducing complex STI structures, the patent changes the doping concentration parameter in the drift region. By adjusting the doping concentration from a first value to a second value in different regions, the patent achieves improved voltage endurance through a parameter modification that is compatible with existing FINFET manufacturing processes, avoiding additional structural complexity.
3Reliability
If gate stack region is optimized to reduce gate field, then reliability is improved, but gate-induced drain leakage issues persist
Solution Approach 1:
The drift region with its specific doping concentration profile acts as an intermediary between the gate and the drain. By optimizing the doping concentration in the drift region, the patent mediates the electric field distribution, reducing both the gate field strength and the gate-induced drain leakage current, thereby addressing both issues simultaneously.
Data Source
AI summary
Methods for forming FIN-shaped field effect transistors (FINFETs) capable of withstanding high voltage applications and the resulting devices are disclosed. Embodiments include forming a source and a drain on a substrate, forming a thin body (FIN) on the substrate and connecting the source and the drain, forming a gate over top and side surfaces of a first part of the FIN, thereby defining a drain-side FIN region of the FIN between the gate and the drain, and forming a shielding region over top and side surfaces of a second part of the FIN in the drain-side FIN region.