Vertical Current-Path HV FET Structure for Surface Breakdown
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Solution Overview
Problem
High voltage field effect transistors face surface breakdown voltage issues due to complex extended low doped drain structures, which increase process complexity and cost.
Innovation Solution
A semiconductor structure with a shallow trench isolation structure, a gate stack structure, and epitaxial semiconductor material portions to reduce high voltage breakdown by increasing the total length of current paths within a smaller device area, including a dielectric gate spacer and source/drain regions with specific doping configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex extended low doped drain structures are used to improve surface breakdown characteristics, then surface breakdown voltage is improved, but process complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts and eliminates the complex extended low doped drain structure from the device design. Instead of using the traditional complex LDD structure to improve surface breakdown characteristics, the invention employs a simplified structure that achieves the same reliability improvement through a different approach, thereby reducing process complexity and manufacturing cost while maintaining enhanced surface breakdown voltage performance
2Reliability
If complex extended low doped drain structures are used to improve surface breakdown characteristics, then surface breakdown voltage is improved, but manufacturing cost increases
Solution Approach 1:
The patent removes the complex extended low doped drain structure that drives up manufacturing costs. The simplified structure design requires fewer fabrication steps and less complex processing, directly reducing manufacturing cost while still achieving improved surface breakdown voltage characteristics through alternative structural arrangements
Solution Approach 2:
The invention changes key structural parameters such as doping concentration distributions and geometric dimensions to achieve improved surface breakdown voltage without requiring complex extended low doped drain structures. By optimizing these parameters in a simplified structure, the patent achieves both reliability improvement and cost reduction
3Reliability
If larger device area is used to accommodate complex structures, then high voltage breakdown performance is improved, but device area increases
Solution Approach 1:
The patent transitions from horizontal current paths to vertical current paths in the device structure. This dimensional change allows the current to flow vertically through the device, enabling improved high voltage breakdown performance within a smaller lateral footprint. The vertical architecture efficiently utilizes the third dimension to achieve better breakdown characteristics without increasing the device's planar area
Data Source
AI summary
A field effect transistor for a high voltage operation can include vertical current paths, which may include vertical surface regions of a pedestal semiconductor portion that protrudes above a base semiconductor portion. The pedestal semiconductor portion can be formed by etching a semiconductor material layer employing a gate structure as an etch mask. A dielectric gate spacer can be formed on sidewalls of the pedestal semiconductor portion. A source region and a drain region may be formed underneath top surfaces of the base semiconductor portion. Alternatively, epitaxial semiconductor material portions can be grown on the top surfaces of the base semiconductor portions, and a source region and a drain region can be formed therein. Alternatively, a source region and a drain region can be formed within via cavities in a planarization dielectric layer.