Finfet.pptx (Size: 1.39 MB / Downloads: 249)
Seminar on finFET technology
PARTIALLY DEPLETED SOI
PARASITIC BIPOLAR EFFECT
SCALING FROM PD SOI TO FD SOI
MAJOR DESIGN ISSUES
FEATURES OF FINFET
PROCESS FLOW OF FINFET
APPLICATIONS OF FINFET
Since the fabrication of MOSFET, the minimum channel length has been shrinking continuously.
The motivation behind this decrease is seen in high speed devices and in very large scale integrated circuits.
The limits most often cited are:-
control of the density.
finite subthreshold slope .
quantum-mechanical tunneling .
The channel depletion width must scale with the channel length to contain the off-state leakage I off
high doping concentration.
The gate oxide thickness tox must also scale with the channel length to maintain :-
proper threshold voltage VT .
The thinning of the gate dielectric results in :-
gate tunneling leakage.
degrading the circuit performance.
power and noise margin.
Partially depleted(PD)SOI was the first SOI technology introduced for high performance microprocessor applications.
PARTIALLY DEPLETED [PD] SOI:
The PD SOI device is largely identical to the bulk device, except for the addition of a buried oxide (“BOX”) layer
The device offers several advantages for performance/ power improvement:-
reduced junction capacitance.
Parasitic bipolar effect.
Hysteretic VT variation.
Dynamic loading effects.
MAJOR DESIGN ISSUES :
Gate Oxide Tunneling Leakage
Soft Error Rate
Strained-Si channel And High-k Gate
Features of finFET:
Finfet consists of a vertical Si fin controlled by self_aligned double gate.
Main Features of Finfet are:-
Ultra thin Si fin for suppression of short channel effects
Raised source/drain to reduce parasitic resistance and improve currrent drive
Symmetric gates yield great performance,but can built asymmetric gates that target VT .
Finfets are designed to use multiple fins to achieve larger channel widths.
Source/Drain pads connect the fins in parallel.
As the number of fins is increased ,the current through the device increases.
.For eg: A 5 fin device 5 times more current than single fin device.
FinFET-DGCMOS Process Flow in Detail:
A conventional SOI wafer can be used as starting material for:-
Masked ion implantations.
specialized passive elements.
Gate deposition and etch.
APPLICATIONS OF FinFET:
DG devices like Fin FETs offer unique opportunities for microprocessor design.compared to a planar process in the same technology node,
FinFETs have reduced channel and gate leakage currents. This can lead to considerable power reductions when converting a planar design to fin FET technology.
Utilizing fin FETs would lead to a reduction in total power by a factor of two, without compromising performance.
Another possibility to save power arises when both gates can be controlled separately.
The second gate can be used to control the threshold voltage of the device, thereby allowing fast switching on one side and reduced leakage currents when circuits are idle.
Finally, separate access to both gates could also be used to design simplified logic gates.
This would also reduce power, and save chip area, leading to smaller, more cost-efficient designs. However chip designs using finFETs must cope with quantization of device width.
since every single transistor consists of an integral number of fins,each fin having the same height.
SIMULATION OF finFET USING DEVICE3D:
This article will present the simulation methodology of a self-aligned double-gate MOSFET structure (FinFET) using SILVACO 3-D simulation suite.
A transistor is formed in a vertical ultra –thin Si fin and is controlled by a double-gate, which considerably reduced short channel effects.
the two gates are self aligned and are aligned to S/D.
S/D is raised to reduce the access resistance.
Up to date gate process: low temperature, high -k dielectrics can be used .
The 3-D SILVACO simulation suite including Device3D, DevEdit3D and TonyPlot3D, allows device engineers to study deep sub-micron devices which are 3-D by nature like the FinFET presented above.
A 3-D FinFET structure was designed by using DevEdit3D. This is an advanced tool for structure editing and mesh generation.
Simulations show that this structure should be scalable down to 10 nm.
This structure was fabricated by forming the S\D before the gate.
Further performance improvement is possible by using a thinner gate dielectric and thinner spacers.
FinFET is similar to the conventional MOSFET with regard to layout and fabrication.
. It is an attractive successor to the single gate MOSFET by virtue of its superior electrostatic properties and comparative ease of manufacturability.
Industrial research groups such as Intel, IBM and AMD have shown interests in developing similar devices, as well as mechanisms to migrate mask layouts from Bulk-MOS to FinFETs.
Design Issues such as high quality ultra thin fin lithography and source\drain resistance need to be resolved and a high-yield process flow needs to be established by process researchers before FinFETs can be used in commercial.
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