FinFET Corner Doping Structure for Steep MOSFET Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In FinFETs, the electric field concentrates at the corner portion of the fin, leading to a parasitic channel turning ON at a lower voltage than the normal channel, resulting in varying threshold voltage and gentle ON/OFF performance.
Innovation Solution
A semiconductor device with a trench structure is designed, featuring a semiconductor region with higher impurity concentration at the corner portion of the fin, connected to the gate electrode and insulating film, to prevent the parasitic channel from turning ON at low voltage and enhance ON/OFF operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a FinFET structure is used to increase effective channel width, then on-resistance is reduced, but electric field concentration occurs at corner portions causing parasitic channels to turn ON at low voltage
Solution Approach 1:
The patent applies local quality by forming a channel impurity concentration adjustment region with higher impurity concentration specifically at the corner portion of the fin upper surface. This localized modification increases the threshold voltage at the corner while preserving the low-resistance channel paths along the fin sides, thus resolving the contradiction between low on-resistance and consistent threshold voltage.
Solution Approach 2:
The patent changes the impurity concentration parameter locally at the corner portion by forming a region with impurity concentration higher than the surrounding areas. This parameter change modifies the electrical characteristics at the critical corner location, preventing parasitic channel formation while maintaining overall device performance.
2Reliability
If impurity concentration is increased at the corner portion to prevent parasitic channels, then threshold voltage consistency is improved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the fin structure into distinct regions: the main fin body and a separate channel impurity concentration adjustment region at the corner portion. This segmentation allows independent optimization of each region's impurity concentration, simplifying the manufacturing process while achieving the desired electrical characteristics.
Solution Approach 2:
The channel impurity concentration adjustment region is formed in advance during the fabrication process, before the final device operation. This preliminary action pre-establishes the higher impurity concentration at the corner portion, preventing parasitic channel formation during subsequent operation without requiring complex real-time adjustments.
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
This design effectively increases the threshold voltage at the corner portion, allowing for steep ON/OFF operation and improved performance by uniformly distributing current across the fin, reducing ON resistance and enhancing gate controllability.
Implementation Method 1
a second semiconductor region of the second conductivity type that is formed at a corner portion which is an upper end of the side surface of the protruding portion and has impurity concentration twice or more impurity concentration of the first semiconductor region
Data Source
AI summary
In the present invention, in a FinFET having a channel forming region on a surface of a fin that is a semiconductor layer protruding on an upper surface of a substrate, a channel at a corner of the fin is prevented from becoming an ON state with a low voltage and a steep ON/OFF operation is made possible. As a means thereof, in a MOSFET that has a plurality of trenches, each of which have embedded therein a gate electrode, on an upper surface of an n-type epitaxial substrate provided with a drain region on a bottom surface and that has a channel region formed on a surface of a fin which is a protrusion part between the trenches adjacent to each other, a p-type body layer that constitutes a lateral surface of the fin, and a p+-type semiconductor region that constitutes a corner which is an end of the upper surface of the fin, are formed.