Vertical FET Fin Structure Using Schottky Shielding for Fast Switching
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Solution Overview
Problem
Vertical field-effect transistors with traditional pn junctions exhibit slow switching behavior and short-circuit strength due to the slow formation of space charge regions, which is a limitation in power electronics applications.
Innovation Solution
Incorporating a Schottky junction at the base of the fins eliminates the need for complex p+-doping in shielding elements, allowing for quicker depletion of the region under the fins, thereby enhancing short-circuit strength and switching behavior by forming a space charge region more rapidly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a pn junction is used in the shielding region, then the transistor structure is stable and reliable, but the switching speed is slow and short-circuit strength is limited
Solution Approach 1:
The patent changes the fundamental parameter of the junction type from pn junction to Schottky junction. This parameter change transforms the shielding mechanism from minority carrier-based (slow) to majority carrier-based (fast), achieving rapid switching and enhanced short-circuit strength while eliminating complex p+-doping requirements
Solution Approach 2:
The patent extracts and removes the complex p+-doping shielding elements from the traditional FinMOS structure. By taking out this complex component and replacing it with a Schottky contact, the invention simplifies the device structure while achieving superior switching performance and short-circuit protection
2Reliability
If p+-doping is applied to shielding elements, then short-circuit protection is achieved, but the process becomes complex and expensive
Solution Approach 1:
The patent replaces expensive and complex p+-doping processes with a simpler Schottky contact structure that can be formed through metal deposition. This substitution uses a simpler, more manufacturable approach to achieve the same short-circuit protection function
Solution Approach 2:
The patent substitutes the chemical doping process (p+-doping) with a physical contact structure (Schottky contact). This replacement transitions from a complex chemical implantation process to a simpler physical deposition process, improving ease of manufacture while maintaining reliability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The Schottky junction improves short-circuit strength and switching behavior by forming a space charge region faster than a pn junction, providing effective shielding and reducing voltage transients and overvoltages during commutation.
Implementation Method 1
inserting a Schottky contact at the base of the fins
Implementation Method 2
the region under the fins can be depleted more quickly. This in turn is decisive for the short-circuit strength and the switching behavior
Data Source
AI summary
A vertical field-effect transistor structure. The vertical field-effect transistor structure has a semiconductor body having a first terminal zone, a drift zone, and a second terminal zone of a first conductivity type; a channel zone, arranged between the first and the second terminal zone, of the first or second conductivity type; a plurality of first trenches extending into the semiconductor body from the second terminal zone into the drift zone and form fins of the channel and second terminal zones; a control electrode arranged in the first trenches, which is arranged adjacent to the channel zone and insulated from the semiconductor body; a current path, connected between the first and the second terminal zone and in parallel with the channel zone, having at least one Schottky junction and being designed to conduct when a reverse voltage between the first and the second terminal zone is reached.