Vertical MOSFET Wrap-Around Gate Radial Segmentation
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Solution Overview
Problem
The continuous scaling of MOSFET gate length in III-V MOSFETs integrated on Si substrates leads to increased off-state power consumption due to leakage currents, and there is a need for improved device performance to reduce parasitic capacitances and leakage currents in vertical nanowire MOSFETs.
Innovation Solution
A vertical metal oxide semiconductor field effect transistor (MOSFET) design featuring a wrap-around gate with a field plate portion and a gate portion, where the field plate is arranged at a larger radial distance from the nanowire center than the gate portion, increasing the tunneling distance and effectively reducing leakage currents and output conductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gate length is continuously scaled down to improve device performance, then the drive current and transconductance are improved, but the off-state power consumption increases due to leakage currents
Solution Approach 1:
The gate electrode is segmented into two distinct portions: a gate portion closer to the nanowire center for strong channel control, and a field plate portion at larger radial distance for leakage suppression. This segmentation allows each portion to perform its specialized function independently, resolving the contradiction between drive current and leakage current.
Solution Approach 2:
Different regions of the gate structure are assigned different functional qualities: the gate portion provides high electric field for strong inversion layer formation (improving drive current), while the field plate portion provides extended field control at larger radius (suppressing leakage). This local differentiation of functional quality resolves the performance contradiction.
2Device complexity
If a conventional gate structure is used, then the device structure is simple, but the parasitic capacitances are high and leakage currents are not sufficiently reduced
Solution Approach 1:
The gate structure transitions from a conventional planar configuration to a three-dimensional wrap-around configuration with radial positioning. The field plate portion extends to a larger radial distance from the nanowire center, creating a multi-dimensional electric field distribution that reduces parasitic capacitance between gate and drain/source regions.
3Ease of operation
If the gate is positioned closer to the nanowire center, then the control over charge transport is improved, but the tunneling leakage current increases
Solution Approach 1:
The gate electrode is divided into spatially separated portions: the gate portion at smaller radial distance provides strong control over charge transport in the channel, while the field plate portion at larger radial distance creates an extended depletion region that suppresses tunneling leakage. This spatial segmentation resolves the contradiction between control strength and leakage suppression.
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 enhances control over charge transport, increases breakdown voltage, suppresses tunneling leakage current, and allows for higher operating voltages while reducing off-state power consumption by tailoring the electric field and bandgap along the nanowire.
Implementation Method 1
the field plate portion is arranged at a first radial distance from the center of the nanowire and the gate portion is arranged at a second radial distance from the center of the nanowire, wherein the first radial distance is larger than the second radial distance... suppresses the tunneling leakage current
Data Source
AI summary
A vertical metal oxide semiconductor field effect transistor (MOSFET) and a method for forming a vertical MOSFET is presented. The MOSFET comprises: a top contact; a bottom contact; a nanowire (602) forming a charge transport channel between the top contact and the bottom contact; and a wrap-around gate (650) enclosing the nanowire (602) circumference, the wrap-around gate (650) having an extension spanning over a portion of the nanowire (602) in a longitudinal direction of the nanowire (602), wherein the wrap-around gate (650) comprises a gate portion (614) and a field plate portion (616) for controlling a charge transport in the charge transport channel, and wherein the field plate portion (616) is arranged at a first radial distance (636) from the center of the nanowire (602) and the gate portion (614) is arranged at a second radial distance (634) from the center of the nanowire (602); characterized in that the first radial distance (636) is larger than the second radial distance (634).